Linux-2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
new file mode 100644
index 0000000..2504927
--- /dev/null
+++ b/net/ipv4/tcp_input.c
@@ -0,0 +1,4959 @@
+/*
+ * INET An implementation of the TCP/IP protocol suite for the LINUX
+ * operating system. INET is implemented using the BSD Socket
+ * interface as the means of communication with the user level.
+ *
+ * Implementation of the Transmission Control Protocol(TCP).
+ *
+ * Version: $Id: tcp_input.c,v 1.243 2002/02/01 22:01:04 davem Exp $
+ *
+ * Authors: Ross Biro, <bir7@leland.Stanford.Edu>
+ * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
+ * Mark Evans, <evansmp@uhura.aston.ac.uk>
+ * Corey Minyard <wf-rch!minyard@relay.EU.net>
+ * Florian La Roche, <flla@stud.uni-sb.de>
+ * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
+ * Linus Torvalds, <torvalds@cs.helsinki.fi>
+ * Alan Cox, <gw4pts@gw4pts.ampr.org>
+ * Matthew Dillon, <dillon@apollo.west.oic.com>
+ * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
+ * Jorge Cwik, <jorge@laser.satlink.net>
+ */
+
+/*
+ * Changes:
+ * Pedro Roque : Fast Retransmit/Recovery.
+ * Two receive queues.
+ * Retransmit queue handled by TCP.
+ * Better retransmit timer handling.
+ * New congestion avoidance.
+ * Header prediction.
+ * Variable renaming.
+ *
+ * Eric : Fast Retransmit.
+ * Randy Scott : MSS option defines.
+ * Eric Schenk : Fixes to slow start algorithm.
+ * Eric Schenk : Yet another double ACK bug.
+ * Eric Schenk : Delayed ACK bug fixes.
+ * Eric Schenk : Floyd style fast retrans war avoidance.
+ * David S. Miller : Don't allow zero congestion window.
+ * Eric Schenk : Fix retransmitter so that it sends
+ * next packet on ack of previous packet.
+ * Andi Kleen : Moved open_request checking here
+ * and process RSTs for open_requests.
+ * Andi Kleen : Better prune_queue, and other fixes.
+ * Andrey Savochkin: Fix RTT measurements in the presnce of
+ * timestamps.
+ * Andrey Savochkin: Check sequence numbers correctly when
+ * removing SACKs due to in sequence incoming
+ * data segments.
+ * Andi Kleen: Make sure we never ack data there is not
+ * enough room for. Also make this condition
+ * a fatal error if it might still happen.
+ * Andi Kleen: Add tcp_measure_rcv_mss to make
+ * connections with MSS<min(MTU,ann. MSS)
+ * work without delayed acks.
+ * Andi Kleen: Process packets with PSH set in the
+ * fast path.
+ * J Hadi Salim: ECN support
+ * Andrei Gurtov,
+ * Pasi Sarolahti,
+ * Panu Kuhlberg: Experimental audit of TCP (re)transmission
+ * engine. Lots of bugs are found.
+ * Pasi Sarolahti: F-RTO for dealing with spurious RTOs
+ * Angelo Dell'Aera: TCP Westwood+ support
+ */
+
+#include <linux/config.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/sysctl.h>
+#include <net/tcp.h>
+#include <net/inet_common.h>
+#include <linux/ipsec.h>
+#include <asm/unaligned.h>
+
+int sysctl_tcp_timestamps = 1;
+int sysctl_tcp_window_scaling = 1;
+int sysctl_tcp_sack = 1;
+int sysctl_tcp_fack = 1;
+int sysctl_tcp_reordering = TCP_FASTRETRANS_THRESH;
+int sysctl_tcp_ecn;
+int sysctl_tcp_dsack = 1;
+int sysctl_tcp_app_win = 31;
+int sysctl_tcp_adv_win_scale = 2;
+
+int sysctl_tcp_stdurg;
+int sysctl_tcp_rfc1337;
+int sysctl_tcp_max_orphans = NR_FILE;
+int sysctl_tcp_frto;
+int sysctl_tcp_nometrics_save;
+int sysctl_tcp_westwood;
+int sysctl_tcp_vegas_cong_avoid;
+
+int sysctl_tcp_moderate_rcvbuf = 1;
+
+/* Default values of the Vegas variables, in fixed-point representation
+ * with V_PARAM_SHIFT bits to the right of the binary point.
+ */
+#define V_PARAM_SHIFT 1
+int sysctl_tcp_vegas_alpha = 1<<V_PARAM_SHIFT;
+int sysctl_tcp_vegas_beta = 3<<V_PARAM_SHIFT;
+int sysctl_tcp_vegas_gamma = 1<<V_PARAM_SHIFT;
+int sysctl_tcp_bic = 1;
+int sysctl_tcp_bic_fast_convergence = 1;
+int sysctl_tcp_bic_low_window = 14;
+int sysctl_tcp_bic_beta = 819; /* = 819/1024 (BICTCP_BETA_SCALE) */
+
+#define FLAG_DATA 0x01 /* Incoming frame contained data. */
+#define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
+#define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
+#define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
+#define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
+#define FLAG_DATA_SACKED 0x20 /* New SACK. */
+#define FLAG_ECE 0x40 /* ECE in this ACK */
+#define FLAG_DATA_LOST 0x80 /* SACK detected data lossage. */
+#define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
+
+#define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
+#define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
+#define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE)
+#define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
+
+#define IsReno(tp) ((tp)->rx_opt.sack_ok == 0)
+#define IsFack(tp) ((tp)->rx_opt.sack_ok & 2)
+#define IsDSack(tp) ((tp)->rx_opt.sack_ok & 4)
+
+#define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
+
+/* Adapt the MSS value used to make delayed ack decision to the
+ * real world.
+ */
+static inline void tcp_measure_rcv_mss(struct tcp_sock *tp,
+ struct sk_buff *skb)
+{
+ unsigned int len, lss;
+
+ lss = tp->ack.last_seg_size;
+ tp->ack.last_seg_size = 0;
+
+ /* skb->len may jitter because of SACKs, even if peer
+ * sends good full-sized frames.
+ */
+ len = skb->len;
+ if (len >= tp->ack.rcv_mss) {
+ tp->ack.rcv_mss = len;
+ } else {
+ /* Otherwise, we make more careful check taking into account,
+ * that SACKs block is variable.
+ *
+ * "len" is invariant segment length, including TCP header.
+ */
+ len += skb->data - skb->h.raw;
+ if (len >= TCP_MIN_RCVMSS + sizeof(struct tcphdr) ||
+ /* If PSH is not set, packet should be
+ * full sized, provided peer TCP is not badly broken.
+ * This observation (if it is correct 8)) allows
+ * to handle super-low mtu links fairly.
+ */
+ (len >= TCP_MIN_MSS + sizeof(struct tcphdr) &&
+ !(tcp_flag_word(skb->h.th)&TCP_REMNANT))) {
+ /* Subtract also invariant (if peer is RFC compliant),
+ * tcp header plus fixed timestamp option length.
+ * Resulting "len" is MSS free of SACK jitter.
+ */
+ len -= tp->tcp_header_len;
+ tp->ack.last_seg_size = len;
+ if (len == lss) {
+ tp->ack.rcv_mss = len;
+ return;
+ }
+ }
+ tp->ack.pending |= TCP_ACK_PUSHED;
+ }
+}
+
+static void tcp_incr_quickack(struct tcp_sock *tp)
+{
+ unsigned quickacks = tp->rcv_wnd/(2*tp->ack.rcv_mss);
+
+ if (quickacks==0)
+ quickacks=2;
+ if (quickacks > tp->ack.quick)
+ tp->ack.quick = min(quickacks, TCP_MAX_QUICKACKS);
+}
+
+void tcp_enter_quickack_mode(struct tcp_sock *tp)
+{
+ tcp_incr_quickack(tp);
+ tp->ack.pingpong = 0;
+ tp->ack.ato = TCP_ATO_MIN;
+}
+
+/* Send ACKs quickly, if "quick" count is not exhausted
+ * and the session is not interactive.
+ */
+
+static __inline__ int tcp_in_quickack_mode(struct tcp_sock *tp)
+{
+ return (tp->ack.quick && !tp->ack.pingpong);
+}
+
+/* Buffer size and advertised window tuning.
+ *
+ * 1. Tuning sk->sk_sndbuf, when connection enters established state.
+ */
+
+static void tcp_fixup_sndbuf(struct sock *sk)
+{
+ int sndmem = tcp_sk(sk)->rx_opt.mss_clamp + MAX_TCP_HEADER + 16 +
+ sizeof(struct sk_buff);
+
+ if (sk->sk_sndbuf < 3 * sndmem)
+ sk->sk_sndbuf = min(3 * sndmem, sysctl_tcp_wmem[2]);
+}
+
+/* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
+ *
+ * All tcp_full_space() is split to two parts: "network" buffer, allocated
+ * forward and advertised in receiver window (tp->rcv_wnd) and
+ * "application buffer", required to isolate scheduling/application
+ * latencies from network.
+ * window_clamp is maximal advertised window. It can be less than
+ * tcp_full_space(), in this case tcp_full_space() - window_clamp
+ * is reserved for "application" buffer. The less window_clamp is
+ * the smoother our behaviour from viewpoint of network, but the lower
+ * throughput and the higher sensitivity of the connection to losses. 8)
+ *
+ * rcv_ssthresh is more strict window_clamp used at "slow start"
+ * phase to predict further behaviour of this connection.
+ * It is used for two goals:
+ * - to enforce header prediction at sender, even when application
+ * requires some significant "application buffer". It is check #1.
+ * - to prevent pruning of receive queue because of misprediction
+ * of receiver window. Check #2.
+ *
+ * The scheme does not work when sender sends good segments opening
+ * window and then starts to feed us spagetti. But it should work
+ * in common situations. Otherwise, we have to rely on queue collapsing.
+ */
+
+/* Slow part of check#2. */
+static int __tcp_grow_window(struct sock *sk, struct tcp_sock *tp,
+ struct sk_buff *skb)
+{
+ /* Optimize this! */
+ int truesize = tcp_win_from_space(skb->truesize)/2;
+ int window = tcp_full_space(sk)/2;
+
+ while (tp->rcv_ssthresh <= window) {
+ if (truesize <= skb->len)
+ return 2*tp->ack.rcv_mss;
+
+ truesize >>= 1;
+ window >>= 1;
+ }
+ return 0;
+}
+
+static inline void tcp_grow_window(struct sock *sk, struct tcp_sock *tp,
+ struct sk_buff *skb)
+{
+ /* Check #1 */
+ if (tp->rcv_ssthresh < tp->window_clamp &&
+ (int)tp->rcv_ssthresh < tcp_space(sk) &&
+ !tcp_memory_pressure) {
+ int incr;
+
+ /* Check #2. Increase window, if skb with such overhead
+ * will fit to rcvbuf in future.
+ */
+ if (tcp_win_from_space(skb->truesize) <= skb->len)
+ incr = 2*tp->advmss;
+ else
+ incr = __tcp_grow_window(sk, tp, skb);
+
+ if (incr) {
+ tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr, tp->window_clamp);
+ tp->ack.quick |= 1;
+ }
+ }
+}
+
+/* 3. Tuning rcvbuf, when connection enters established state. */
+
+static void tcp_fixup_rcvbuf(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ int rcvmem = tp->advmss + MAX_TCP_HEADER + 16 + sizeof(struct sk_buff);
+
+ /* Try to select rcvbuf so that 4 mss-sized segments
+ * will fit to window and correspoding skbs will fit to our rcvbuf.
+ * (was 3; 4 is minimum to allow fast retransmit to work.)
+ */
+ while (tcp_win_from_space(rcvmem) < tp->advmss)
+ rcvmem += 128;
+ if (sk->sk_rcvbuf < 4 * rcvmem)
+ sk->sk_rcvbuf = min(4 * rcvmem, sysctl_tcp_rmem[2]);
+}
+
+/* 4. Try to fixup all. It is made iimediately after connection enters
+ * established state.
+ */
+static void tcp_init_buffer_space(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ int maxwin;
+
+ if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK))
+ tcp_fixup_rcvbuf(sk);
+ if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK))
+ tcp_fixup_sndbuf(sk);
+
+ tp->rcvq_space.space = tp->rcv_wnd;
+
+ maxwin = tcp_full_space(sk);
+
+ if (tp->window_clamp >= maxwin) {
+ tp->window_clamp = maxwin;
+
+ if (sysctl_tcp_app_win && maxwin > 4 * tp->advmss)
+ tp->window_clamp = max(maxwin -
+ (maxwin >> sysctl_tcp_app_win),
+ 4 * tp->advmss);
+ }
+
+ /* Force reservation of one segment. */
+ if (sysctl_tcp_app_win &&
+ tp->window_clamp > 2 * tp->advmss &&
+ tp->window_clamp + tp->advmss > maxwin)
+ tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss);
+
+ tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp);
+ tp->snd_cwnd_stamp = tcp_time_stamp;
+}
+
+static void init_bictcp(struct tcp_sock *tp)
+{
+ tp->bictcp.cnt = 0;
+
+ tp->bictcp.last_max_cwnd = 0;
+ tp->bictcp.last_cwnd = 0;
+ tp->bictcp.last_stamp = 0;
+}
+
+/* 5. Recalculate window clamp after socket hit its memory bounds. */
+static void tcp_clamp_window(struct sock *sk, struct tcp_sock *tp)
+{
+ struct sk_buff *skb;
+ unsigned int app_win = tp->rcv_nxt - tp->copied_seq;
+ int ofo_win = 0;
+
+ tp->ack.quick = 0;
+
+ skb_queue_walk(&tp->out_of_order_queue, skb) {
+ ofo_win += skb->len;
+ }
+
+ /* If overcommit is due to out of order segments,
+ * do not clamp window. Try to expand rcvbuf instead.
+ */
+ if (ofo_win) {
+ if (sk->sk_rcvbuf < sysctl_tcp_rmem[2] &&
+ !(sk->sk_userlocks & SOCK_RCVBUF_LOCK) &&
+ !tcp_memory_pressure &&
+ atomic_read(&tcp_memory_allocated) < sysctl_tcp_mem[0])
+ sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc),
+ sysctl_tcp_rmem[2]);
+ }
+ if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf) {
+ app_win += ofo_win;
+ if (atomic_read(&sk->sk_rmem_alloc) >= 2 * sk->sk_rcvbuf)
+ app_win >>= 1;
+ if (app_win > tp->ack.rcv_mss)
+ app_win -= tp->ack.rcv_mss;
+ app_win = max(app_win, 2U*tp->advmss);
+
+ if (!ofo_win)
+ tp->window_clamp = min(tp->window_clamp, app_win);
+ tp->rcv_ssthresh = min(tp->window_clamp, 2U*tp->advmss);
+ }
+}
+
+/* Receiver "autotuning" code.
+ *
+ * The algorithm for RTT estimation w/o timestamps is based on
+ * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
+ * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps>
+ *
+ * More detail on this code can be found at
+ * <http://www.psc.edu/~jheffner/senior_thesis.ps>,
+ * though this reference is out of date. A new paper
+ * is pending.
+ */
+static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep)
+{
+ u32 new_sample = tp->rcv_rtt_est.rtt;
+ long m = sample;
+
+ if (m == 0)
+ m = 1;
+
+ if (new_sample != 0) {
+ /* If we sample in larger samples in the non-timestamp
+ * case, we could grossly overestimate the RTT especially
+ * with chatty applications or bulk transfer apps which
+ * are stalled on filesystem I/O.
+ *
+ * Also, since we are only going for a minimum in the
+ * non-timestamp case, we do not smoothe things out
+ * else with timestamps disabled convergance takes too
+ * long.
+ */
+ if (!win_dep) {
+ m -= (new_sample >> 3);
+ new_sample += m;
+ } else if (m < new_sample)
+ new_sample = m << 3;
+ } else {
+ /* No previous mesaure. */
+ new_sample = m << 3;
+ }
+
+ if (tp->rcv_rtt_est.rtt != new_sample)
+ tp->rcv_rtt_est.rtt = new_sample;
+}
+
+static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp)
+{
+ if (tp->rcv_rtt_est.time == 0)
+ goto new_measure;
+ if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq))
+ return;
+ tcp_rcv_rtt_update(tp,
+ jiffies - tp->rcv_rtt_est.time,
+ 1);
+
+new_measure:
+ tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd;
+ tp->rcv_rtt_est.time = tcp_time_stamp;
+}
+
+static inline void tcp_rcv_rtt_measure_ts(struct tcp_sock *tp, struct sk_buff *skb)
+{
+ if (tp->rx_opt.rcv_tsecr &&
+ (TCP_SKB_CB(skb)->end_seq -
+ TCP_SKB_CB(skb)->seq >= tp->ack.rcv_mss))
+ tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0);
+}
+
+/*
+ * This function should be called every time data is copied to user space.
+ * It calculates the appropriate TCP receive buffer space.
+ */
+void tcp_rcv_space_adjust(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ int time;
+ int space;
+
+ if (tp->rcvq_space.time == 0)
+ goto new_measure;
+
+ time = tcp_time_stamp - tp->rcvq_space.time;
+ if (time < (tp->rcv_rtt_est.rtt >> 3) ||
+ tp->rcv_rtt_est.rtt == 0)
+ return;
+
+ space = 2 * (tp->copied_seq - tp->rcvq_space.seq);
+
+ space = max(tp->rcvq_space.space, space);
+
+ if (tp->rcvq_space.space != space) {
+ int rcvmem;
+
+ tp->rcvq_space.space = space;
+
+ if (sysctl_tcp_moderate_rcvbuf) {
+ int new_clamp = space;
+
+ /* Receive space grows, normalize in order to
+ * take into account packet headers and sk_buff
+ * structure overhead.
+ */
+ space /= tp->advmss;
+ if (!space)
+ space = 1;
+ rcvmem = (tp->advmss + MAX_TCP_HEADER +
+ 16 + sizeof(struct sk_buff));
+ while (tcp_win_from_space(rcvmem) < tp->advmss)
+ rcvmem += 128;
+ space *= rcvmem;
+ space = min(space, sysctl_tcp_rmem[2]);
+ if (space > sk->sk_rcvbuf) {
+ sk->sk_rcvbuf = space;
+
+ /* Make the window clamp follow along. */
+ tp->window_clamp = new_clamp;
+ }
+ }
+ }
+
+new_measure:
+ tp->rcvq_space.seq = tp->copied_seq;
+ tp->rcvq_space.time = tcp_time_stamp;
+}
+
+/* There is something which you must keep in mind when you analyze the
+ * behavior of the tp->ato delayed ack timeout interval. When a
+ * connection starts up, we want to ack as quickly as possible. The
+ * problem is that "good" TCP's do slow start at the beginning of data
+ * transmission. The means that until we send the first few ACK's the
+ * sender will sit on his end and only queue most of his data, because
+ * he can only send snd_cwnd unacked packets at any given time. For
+ * each ACK we send, he increments snd_cwnd and transmits more of his
+ * queue. -DaveM
+ */
+static void tcp_event_data_recv(struct sock *sk, struct tcp_sock *tp, struct sk_buff *skb)
+{
+ u32 now;
+
+ tcp_schedule_ack(tp);
+
+ tcp_measure_rcv_mss(tp, skb);
+
+ tcp_rcv_rtt_measure(tp);
+
+ now = tcp_time_stamp;
+
+ if (!tp->ack.ato) {
+ /* The _first_ data packet received, initialize
+ * delayed ACK engine.
+ */
+ tcp_incr_quickack(tp);
+ tp->ack.ato = TCP_ATO_MIN;
+ } else {
+ int m = now - tp->ack.lrcvtime;
+
+ if (m <= TCP_ATO_MIN/2) {
+ /* The fastest case is the first. */
+ tp->ack.ato = (tp->ack.ato>>1) + TCP_ATO_MIN/2;
+ } else if (m < tp->ack.ato) {
+ tp->ack.ato = (tp->ack.ato>>1) + m;
+ if (tp->ack.ato > tp->rto)
+ tp->ack.ato = tp->rto;
+ } else if (m > tp->rto) {
+ /* Too long gap. Apparently sender falled to
+ * restart window, so that we send ACKs quickly.
+ */
+ tcp_incr_quickack(tp);
+ sk_stream_mem_reclaim(sk);
+ }
+ }
+ tp->ack.lrcvtime = now;
+
+ TCP_ECN_check_ce(tp, skb);
+
+ if (skb->len >= 128)
+ tcp_grow_window(sk, tp, skb);
+}
+
+/* When starting a new connection, pin down the current choice of
+ * congestion algorithm.
+ */
+void tcp_ca_init(struct tcp_sock *tp)
+{
+ if (sysctl_tcp_westwood)
+ tp->adv_cong = TCP_WESTWOOD;
+ else if (sysctl_tcp_bic)
+ tp->adv_cong = TCP_BIC;
+ else if (sysctl_tcp_vegas_cong_avoid) {
+ tp->adv_cong = TCP_VEGAS;
+ tp->vegas.baseRTT = 0x7fffffff;
+ tcp_vegas_enable(tp);
+ }
+}
+
+/* Do RTT sampling needed for Vegas.
+ * Basically we:
+ * o min-filter RTT samples from within an RTT to get the current
+ * propagation delay + queuing delay (we are min-filtering to try to
+ * avoid the effects of delayed ACKs)
+ * o min-filter RTT samples from a much longer window (forever for now)
+ * to find the propagation delay (baseRTT)
+ */
+static inline void vegas_rtt_calc(struct tcp_sock *tp, __u32 rtt)
+{
+ __u32 vrtt = rtt + 1; /* Never allow zero rtt or baseRTT */
+
+ /* Filter to find propagation delay: */
+ if (vrtt < tp->vegas.baseRTT)
+ tp->vegas.baseRTT = vrtt;
+
+ /* Find the min RTT during the last RTT to find
+ * the current prop. delay + queuing delay:
+ */
+ tp->vegas.minRTT = min(tp->vegas.minRTT, vrtt);
+ tp->vegas.cntRTT++;
+}
+
+/* Called to compute a smoothed rtt estimate. The data fed to this
+ * routine either comes from timestamps, or from segments that were
+ * known _not_ to have been retransmitted [see Karn/Partridge
+ * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
+ * piece by Van Jacobson.
+ * NOTE: the next three routines used to be one big routine.
+ * To save cycles in the RFC 1323 implementation it was better to break
+ * it up into three procedures. -- erics
+ */
+static void tcp_rtt_estimator(struct tcp_sock *tp, __u32 mrtt)
+{
+ long m = mrtt; /* RTT */
+
+ if (tcp_vegas_enabled(tp))
+ vegas_rtt_calc(tp, mrtt);
+
+ /* The following amusing code comes from Jacobson's
+ * article in SIGCOMM '88. Note that rtt and mdev
+ * are scaled versions of rtt and mean deviation.
+ * This is designed to be as fast as possible
+ * m stands for "measurement".
+ *
+ * On a 1990 paper the rto value is changed to:
+ * RTO = rtt + 4 * mdev
+ *
+ * Funny. This algorithm seems to be very broken.
+ * These formulae increase RTO, when it should be decreased, increase
+ * too slowly, when it should be incresed fastly, decrease too fastly
+ * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
+ * does not matter how to _calculate_ it. Seems, it was trap
+ * that VJ failed to avoid. 8)
+ */
+ if(m == 0)
+ m = 1;
+ if (tp->srtt != 0) {
+ m -= (tp->srtt >> 3); /* m is now error in rtt est */
+ tp->srtt += m; /* rtt = 7/8 rtt + 1/8 new */
+ if (m < 0) {
+ m = -m; /* m is now abs(error) */
+ m -= (tp->mdev >> 2); /* similar update on mdev */
+ /* This is similar to one of Eifel findings.
+ * Eifel blocks mdev updates when rtt decreases.
+ * This solution is a bit different: we use finer gain
+ * for mdev in this case (alpha*beta).
+ * Like Eifel it also prevents growth of rto,
+ * but also it limits too fast rto decreases,
+ * happening in pure Eifel.
+ */
+ if (m > 0)
+ m >>= 3;
+ } else {
+ m -= (tp->mdev >> 2); /* similar update on mdev */
+ }
+ tp->mdev += m; /* mdev = 3/4 mdev + 1/4 new */
+ if (tp->mdev > tp->mdev_max) {
+ tp->mdev_max = tp->mdev;
+ if (tp->mdev_max > tp->rttvar)
+ tp->rttvar = tp->mdev_max;
+ }
+ if (after(tp->snd_una, tp->rtt_seq)) {
+ if (tp->mdev_max < tp->rttvar)
+ tp->rttvar -= (tp->rttvar-tp->mdev_max)>>2;
+ tp->rtt_seq = tp->snd_nxt;
+ tp->mdev_max = TCP_RTO_MIN;
+ }
+ } else {
+ /* no previous measure. */
+ tp->srtt = m<<3; /* take the measured time to be rtt */
+ tp->mdev = m<<1; /* make sure rto = 3*rtt */
+ tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN);
+ tp->rtt_seq = tp->snd_nxt;
+ }
+
+ tcp_westwood_update_rtt(tp, tp->srtt >> 3);
+}
+
+/* Calculate rto without backoff. This is the second half of Van Jacobson's
+ * routine referred to above.
+ */
+static inline void tcp_set_rto(struct tcp_sock *tp)
+{
+ /* Old crap is replaced with new one. 8)
+ *
+ * More seriously:
+ * 1. If rtt variance happened to be less 50msec, it is hallucination.
+ * It cannot be less due to utterly erratic ACK generation made
+ * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
+ * to do with delayed acks, because at cwnd>2 true delack timeout
+ * is invisible. Actually, Linux-2.4 also generates erratic
+ * ACKs in some curcumstances.
+ */
+ tp->rto = (tp->srtt >> 3) + tp->rttvar;
+
+ /* 2. Fixups made earlier cannot be right.
+ * If we do not estimate RTO correctly without them,
+ * all the algo is pure shit and should be replaced
+ * with correct one. It is exaclty, which we pretend to do.
+ */
+}
+
+/* NOTE: clamping at TCP_RTO_MIN is not required, current algo
+ * guarantees that rto is higher.
+ */
+static inline void tcp_bound_rto(struct tcp_sock *tp)
+{
+ if (tp->rto > TCP_RTO_MAX)
+ tp->rto = TCP_RTO_MAX;
+}
+
+/* Save metrics learned by this TCP session.
+ This function is called only, when TCP finishes successfully
+ i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE.
+ */
+void tcp_update_metrics(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct dst_entry *dst = __sk_dst_get(sk);
+
+ if (sysctl_tcp_nometrics_save)
+ return;
+
+ dst_confirm(dst);
+
+ if (dst && (dst->flags&DST_HOST)) {
+ int m;
+
+ if (tp->backoff || !tp->srtt) {
+ /* This session failed to estimate rtt. Why?
+ * Probably, no packets returned in time.
+ * Reset our results.
+ */
+ if (!(dst_metric_locked(dst, RTAX_RTT)))
+ dst->metrics[RTAX_RTT-1] = 0;
+ return;
+ }
+
+ m = dst_metric(dst, RTAX_RTT) - tp->srtt;
+
+ /* If newly calculated rtt larger than stored one,
+ * store new one. Otherwise, use EWMA. Remember,
+ * rtt overestimation is always better than underestimation.
+ */
+ if (!(dst_metric_locked(dst, RTAX_RTT))) {
+ if (m <= 0)
+ dst->metrics[RTAX_RTT-1] = tp->srtt;
+ else
+ dst->metrics[RTAX_RTT-1] -= (m>>3);
+ }
+
+ if (!(dst_metric_locked(dst, RTAX_RTTVAR))) {
+ if (m < 0)
+ m = -m;
+
+ /* Scale deviation to rttvar fixed point */
+ m >>= 1;
+ if (m < tp->mdev)
+ m = tp->mdev;
+
+ if (m >= dst_metric(dst, RTAX_RTTVAR))
+ dst->metrics[RTAX_RTTVAR-1] = m;
+ else
+ dst->metrics[RTAX_RTTVAR-1] -=
+ (dst->metrics[RTAX_RTTVAR-1] - m)>>2;
+ }
+
+ if (tp->snd_ssthresh >= 0xFFFF) {
+ /* Slow start still did not finish. */
+ if (dst_metric(dst, RTAX_SSTHRESH) &&
+ !dst_metric_locked(dst, RTAX_SSTHRESH) &&
+ (tp->snd_cwnd >> 1) > dst_metric(dst, RTAX_SSTHRESH))
+ dst->metrics[RTAX_SSTHRESH-1] = tp->snd_cwnd >> 1;
+ if (!dst_metric_locked(dst, RTAX_CWND) &&
+ tp->snd_cwnd > dst_metric(dst, RTAX_CWND))
+ dst->metrics[RTAX_CWND-1] = tp->snd_cwnd;
+ } else if (tp->snd_cwnd > tp->snd_ssthresh &&
+ tp->ca_state == TCP_CA_Open) {
+ /* Cong. avoidance phase, cwnd is reliable. */
+ if (!dst_metric_locked(dst, RTAX_SSTHRESH))
+ dst->metrics[RTAX_SSTHRESH-1] =
+ max(tp->snd_cwnd >> 1, tp->snd_ssthresh);
+ if (!dst_metric_locked(dst, RTAX_CWND))
+ dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_cwnd) >> 1;
+ } else {
+ /* Else slow start did not finish, cwnd is non-sense,
+ ssthresh may be also invalid.
+ */
+ if (!dst_metric_locked(dst, RTAX_CWND))
+ dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_ssthresh) >> 1;
+ if (dst->metrics[RTAX_SSTHRESH-1] &&
+ !dst_metric_locked(dst, RTAX_SSTHRESH) &&
+ tp->snd_ssthresh > dst->metrics[RTAX_SSTHRESH-1])
+ dst->metrics[RTAX_SSTHRESH-1] = tp->snd_ssthresh;
+ }
+
+ if (!dst_metric_locked(dst, RTAX_REORDERING)) {
+ if (dst->metrics[RTAX_REORDERING-1] < tp->reordering &&
+ tp->reordering != sysctl_tcp_reordering)
+ dst->metrics[RTAX_REORDERING-1] = tp->reordering;
+ }
+ }
+}
+
+/* Numbers are taken from RFC2414. */
+__u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst)
+{
+ __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0);
+
+ if (!cwnd) {
+ if (tp->mss_cache_std > 1460)
+ cwnd = 2;
+ else
+ cwnd = (tp->mss_cache_std > 1095) ? 3 : 4;
+ }
+ return min_t(__u32, cwnd, tp->snd_cwnd_clamp);
+}
+
+/* Initialize metrics on socket. */
+
+static void tcp_init_metrics(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct dst_entry *dst = __sk_dst_get(sk);
+
+ if (dst == NULL)
+ goto reset;
+
+ dst_confirm(dst);
+
+ if (dst_metric_locked(dst, RTAX_CWND))
+ tp->snd_cwnd_clamp = dst_metric(dst, RTAX_CWND);
+ if (dst_metric(dst, RTAX_SSTHRESH)) {
+ tp->snd_ssthresh = dst_metric(dst, RTAX_SSTHRESH);
+ if (tp->snd_ssthresh > tp->snd_cwnd_clamp)
+ tp->snd_ssthresh = tp->snd_cwnd_clamp;
+ }
+ if (dst_metric(dst, RTAX_REORDERING) &&
+ tp->reordering != dst_metric(dst, RTAX_REORDERING)) {
+ tp->rx_opt.sack_ok &= ~2;
+ tp->reordering = dst_metric(dst, RTAX_REORDERING);
+ }
+
+ if (dst_metric(dst, RTAX_RTT) == 0)
+ goto reset;
+
+ if (!tp->srtt && dst_metric(dst, RTAX_RTT) < (TCP_TIMEOUT_INIT << 3))
+ goto reset;
+
+ /* Initial rtt is determined from SYN,SYN-ACK.
+ * The segment is small and rtt may appear much
+ * less than real one. Use per-dst memory
+ * to make it more realistic.
+ *
+ * A bit of theory. RTT is time passed after "normal" sized packet
+ * is sent until it is ACKed. In normal curcumstances sending small
+ * packets force peer to delay ACKs and calculation is correct too.
+ * The algorithm is adaptive and, provided we follow specs, it
+ * NEVER underestimate RTT. BUT! If peer tries to make some clever
+ * tricks sort of "quick acks" for time long enough to decrease RTT
+ * to low value, and then abruptly stops to do it and starts to delay
+ * ACKs, wait for troubles.
+ */
+ if (dst_metric(dst, RTAX_RTT) > tp->srtt) {
+ tp->srtt = dst_metric(dst, RTAX_RTT);
+ tp->rtt_seq = tp->snd_nxt;
+ }
+ if (dst_metric(dst, RTAX_RTTVAR) > tp->mdev) {
+ tp->mdev = dst_metric(dst, RTAX_RTTVAR);
+ tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN);
+ }
+ tcp_set_rto(tp);
+ tcp_bound_rto(tp);
+ if (tp->rto < TCP_TIMEOUT_INIT && !tp->rx_opt.saw_tstamp)
+ goto reset;
+ tp->snd_cwnd = tcp_init_cwnd(tp, dst);
+ tp->snd_cwnd_stamp = tcp_time_stamp;
+ return;
+
+reset:
+ /* Play conservative. If timestamps are not
+ * supported, TCP will fail to recalculate correct
+ * rtt, if initial rto is too small. FORGET ALL AND RESET!
+ */
+ if (!tp->rx_opt.saw_tstamp && tp->srtt) {
+ tp->srtt = 0;
+ tp->mdev = tp->mdev_max = tp->rttvar = TCP_TIMEOUT_INIT;
+ tp->rto = TCP_TIMEOUT_INIT;
+ }
+}
+
+static void tcp_update_reordering(struct tcp_sock *tp, int metric, int ts)
+{
+ if (metric > tp->reordering) {
+ tp->reordering = min(TCP_MAX_REORDERING, metric);
+
+ /* This exciting event is worth to be remembered. 8) */
+ if (ts)
+ NET_INC_STATS_BH(LINUX_MIB_TCPTSREORDER);
+ else if (IsReno(tp))
+ NET_INC_STATS_BH(LINUX_MIB_TCPRENOREORDER);
+ else if (IsFack(tp))
+ NET_INC_STATS_BH(LINUX_MIB_TCPFACKREORDER);
+ else
+ NET_INC_STATS_BH(LINUX_MIB_TCPSACKREORDER);
+#if FASTRETRANS_DEBUG > 1
+ printk(KERN_DEBUG "Disorder%d %d %u f%u s%u rr%d\n",
+ tp->rx_opt.sack_ok, tp->ca_state,
+ tp->reordering,
+ tp->fackets_out,
+ tp->sacked_out,
+ tp->undo_marker ? tp->undo_retrans : 0);
+#endif
+ /* Disable FACK yet. */
+ tp->rx_opt.sack_ok &= ~2;
+ }
+}
+
+/* This procedure tags the retransmission queue when SACKs arrive.
+ *
+ * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
+ * Packets in queue with these bits set are counted in variables
+ * sacked_out, retrans_out and lost_out, correspondingly.
+ *
+ * Valid combinations are:
+ * Tag InFlight Description
+ * 0 1 - orig segment is in flight.
+ * S 0 - nothing flies, orig reached receiver.
+ * L 0 - nothing flies, orig lost by net.
+ * R 2 - both orig and retransmit are in flight.
+ * L|R 1 - orig is lost, retransmit is in flight.
+ * S|R 1 - orig reached receiver, retrans is still in flight.
+ * (L|S|R is logically valid, it could occur when L|R is sacked,
+ * but it is equivalent to plain S and code short-curcuits it to S.
+ * L|S is logically invalid, it would mean -1 packet in flight 8))
+ *
+ * These 6 states form finite state machine, controlled by the following events:
+ * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
+ * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
+ * 3. Loss detection event of one of three flavors:
+ * A. Scoreboard estimator decided the packet is lost.
+ * A'. Reno "three dupacks" marks head of queue lost.
+ * A''. Its FACK modfication, head until snd.fack is lost.
+ * B. SACK arrives sacking data transmitted after never retransmitted
+ * hole was sent out.
+ * C. SACK arrives sacking SND.NXT at the moment, when the
+ * segment was retransmitted.
+ * 4. D-SACK added new rule: D-SACK changes any tag to S.
+ *
+ * It is pleasant to note, that state diagram turns out to be commutative,
+ * so that we are allowed not to be bothered by order of our actions,
+ * when multiple events arrive simultaneously. (see the function below).
+ *
+ * Reordering detection.
+ * --------------------
+ * Reordering metric is maximal distance, which a packet can be displaced
+ * in packet stream. With SACKs we can estimate it:
+ *
+ * 1. SACK fills old hole and the corresponding segment was not
+ * ever retransmitted -> reordering. Alas, we cannot use it
+ * when segment was retransmitted.
+ * 2. The last flaw is solved with D-SACK. D-SACK arrives
+ * for retransmitted and already SACKed segment -> reordering..
+ * Both of these heuristics are not used in Loss state, when we cannot
+ * account for retransmits accurately.
+ */
+static int
+tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_una)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ unsigned char *ptr = ack_skb->h.raw + TCP_SKB_CB(ack_skb)->sacked;
+ struct tcp_sack_block *sp = (struct tcp_sack_block *)(ptr+2);
+ int num_sacks = (ptr[1] - TCPOLEN_SACK_BASE)>>3;
+ int reord = tp->packets_out;
+ int prior_fackets;
+ u32 lost_retrans = 0;
+ int flag = 0;
+ int i;
+
+ /* So, SACKs for already sent large segments will be lost.
+ * Not good, but alternative is to resegment the queue. */
+ if (sk->sk_route_caps & NETIF_F_TSO) {
+ sk->sk_route_caps &= ~NETIF_F_TSO;
+ sock_set_flag(sk, SOCK_NO_LARGESEND);
+ tp->mss_cache = tp->mss_cache_std;
+ }
+
+ if (!tp->sacked_out)
+ tp->fackets_out = 0;
+ prior_fackets = tp->fackets_out;
+
+ for (i=0; i<num_sacks; i++, sp++) {
+ struct sk_buff *skb;
+ __u32 start_seq = ntohl(sp->start_seq);
+ __u32 end_seq = ntohl(sp->end_seq);
+ int fack_count = 0;
+ int dup_sack = 0;
+
+ /* Check for D-SACK. */
+ if (i == 0) {
+ u32 ack = TCP_SKB_CB(ack_skb)->ack_seq;
+
+ if (before(start_seq, ack)) {
+ dup_sack = 1;
+ tp->rx_opt.sack_ok |= 4;
+ NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV);
+ } else if (num_sacks > 1 &&
+ !after(end_seq, ntohl(sp[1].end_seq)) &&
+ !before(start_seq, ntohl(sp[1].start_seq))) {
+ dup_sack = 1;
+ tp->rx_opt.sack_ok |= 4;
+ NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV);
+ }
+
+ /* D-SACK for already forgotten data...
+ * Do dumb counting. */
+ if (dup_sack &&
+ !after(end_seq, prior_snd_una) &&
+ after(end_seq, tp->undo_marker))
+ tp->undo_retrans--;
+
+ /* Eliminate too old ACKs, but take into
+ * account more or less fresh ones, they can
+ * contain valid SACK info.
+ */
+ if (before(ack, prior_snd_una - tp->max_window))
+ return 0;
+ }
+
+ /* Event "B" in the comment above. */
+ if (after(end_seq, tp->high_seq))
+ flag |= FLAG_DATA_LOST;
+
+ sk_stream_for_retrans_queue(skb, sk) {
+ u8 sacked = TCP_SKB_CB(skb)->sacked;
+ int in_sack;
+
+ /* The retransmission queue is always in order, so
+ * we can short-circuit the walk early.
+ */
+ if(!before(TCP_SKB_CB(skb)->seq, end_seq))
+ break;
+
+ fack_count += tcp_skb_pcount(skb);
+
+ in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
+ !before(end_seq, TCP_SKB_CB(skb)->end_seq);
+
+ /* Account D-SACK for retransmitted packet. */
+ if ((dup_sack && in_sack) &&
+ (sacked & TCPCB_RETRANS) &&
+ after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker))
+ tp->undo_retrans--;
+
+ /* The frame is ACKed. */
+ if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) {
+ if (sacked&TCPCB_RETRANS) {
+ if ((dup_sack && in_sack) &&
+ (sacked&TCPCB_SACKED_ACKED))
+ reord = min(fack_count, reord);
+ } else {
+ /* If it was in a hole, we detected reordering. */
+ if (fack_count < prior_fackets &&
+ !(sacked&TCPCB_SACKED_ACKED))
+ reord = min(fack_count, reord);
+ }
+
+ /* Nothing to do; acked frame is about to be dropped. */
+ continue;
+ }
+
+ if ((sacked&TCPCB_SACKED_RETRANS) &&
+ after(end_seq, TCP_SKB_CB(skb)->ack_seq) &&
+ (!lost_retrans || after(end_seq, lost_retrans)))
+ lost_retrans = end_seq;
+
+ if (!in_sack)
+ continue;
+
+ if (!(sacked&TCPCB_SACKED_ACKED)) {
+ if (sacked & TCPCB_SACKED_RETRANS) {
+ /* If the segment is not tagged as lost,
+ * we do not clear RETRANS, believing
+ * that retransmission is still in flight.
+ */
+ if (sacked & TCPCB_LOST) {
+ TCP_SKB_CB(skb)->sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS);
+ tp->lost_out -= tcp_skb_pcount(skb);
+ tp->retrans_out -= tcp_skb_pcount(skb);
+ }
+ } else {
+ /* New sack for not retransmitted frame,
+ * which was in hole. It is reordering.
+ */
+ if (!(sacked & TCPCB_RETRANS) &&
+ fack_count < prior_fackets)
+ reord = min(fack_count, reord);
+
+ if (sacked & TCPCB_LOST) {
+ TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
+ tp->lost_out -= tcp_skb_pcount(skb);
+ }
+ }
+
+ TCP_SKB_CB(skb)->sacked |= TCPCB_SACKED_ACKED;
+ flag |= FLAG_DATA_SACKED;
+ tp->sacked_out += tcp_skb_pcount(skb);
+
+ if (fack_count > tp->fackets_out)
+ tp->fackets_out = fack_count;
+ } else {
+ if (dup_sack && (sacked&TCPCB_RETRANS))
+ reord = min(fack_count, reord);
+ }
+
+ /* D-SACK. We can detect redundant retransmission
+ * in S|R and plain R frames and clear it.
+ * undo_retrans is decreased above, L|R frames
+ * are accounted above as well.
+ */
+ if (dup_sack &&
+ (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS)) {
+ TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
+ tp->retrans_out -= tcp_skb_pcount(skb);
+ }
+ }
+ }
+
+ /* Check for lost retransmit. This superb idea is
+ * borrowed from "ratehalving". Event "C".
+ * Later note: FACK people cheated me again 8),
+ * we have to account for reordering! Ugly,
+ * but should help.
+ */
+ if (lost_retrans && tp->ca_state == TCP_CA_Recovery) {
+ struct sk_buff *skb;
+
+ sk_stream_for_retrans_queue(skb, sk) {
+ if (after(TCP_SKB_CB(skb)->seq, lost_retrans))
+ break;
+ if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
+ continue;
+ if ((TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) &&
+ after(lost_retrans, TCP_SKB_CB(skb)->ack_seq) &&
+ (IsFack(tp) ||
+ !before(lost_retrans,
+ TCP_SKB_CB(skb)->ack_seq + tp->reordering *
+ tp->mss_cache_std))) {
+ TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
+ tp->retrans_out -= tcp_skb_pcount(skb);
+
+ if (!(TCP_SKB_CB(skb)->sacked&(TCPCB_LOST|TCPCB_SACKED_ACKED))) {
+ tp->lost_out += tcp_skb_pcount(skb);
+ TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
+ flag |= FLAG_DATA_SACKED;
+ NET_INC_STATS_BH(LINUX_MIB_TCPLOSTRETRANSMIT);
+ }
+ }
+ }
+ }
+
+ tp->left_out = tp->sacked_out + tp->lost_out;
+
+ if ((reord < tp->fackets_out) && tp->ca_state != TCP_CA_Loss)
+ tcp_update_reordering(tp, ((tp->fackets_out + 1) - reord), 0);
+
+#if FASTRETRANS_DEBUG > 0
+ BUG_TRAP((int)tp->sacked_out >= 0);
+ BUG_TRAP((int)tp->lost_out >= 0);
+ BUG_TRAP((int)tp->retrans_out >= 0);
+ BUG_TRAP((int)tcp_packets_in_flight(tp) >= 0);
+#endif
+ return flag;
+}
+
+/* RTO occurred, but do not yet enter loss state. Instead, transmit two new
+ * segments to see from the next ACKs whether any data was really missing.
+ * If the RTO was spurious, new ACKs should arrive.
+ */
+void tcp_enter_frto(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct sk_buff *skb;
+
+ tp->frto_counter = 1;
+
+ if (tp->ca_state <= TCP_CA_Disorder ||
+ tp->snd_una == tp->high_seq ||
+ (tp->ca_state == TCP_CA_Loss && !tp->retransmits)) {
+ tp->prior_ssthresh = tcp_current_ssthresh(tp);
+ if (!tcp_westwood_ssthresh(tp))
+ tp->snd_ssthresh = tcp_recalc_ssthresh(tp);
+ }
+
+ /* Have to clear retransmission markers here to keep the bookkeeping
+ * in shape, even though we are not yet in Loss state.
+ * If something was really lost, it is eventually caught up
+ * in tcp_enter_frto_loss.
+ */
+ tp->retrans_out = 0;
+ tp->undo_marker = tp->snd_una;
+ tp->undo_retrans = 0;
+
+ sk_stream_for_retrans_queue(skb, sk) {
+ TCP_SKB_CB(skb)->sacked &= ~TCPCB_RETRANS;
+ }
+ tcp_sync_left_out(tp);
+
+ tcp_set_ca_state(tp, TCP_CA_Open);
+ tp->frto_highmark = tp->snd_nxt;
+}
+
+/* Enter Loss state after F-RTO was applied. Dupack arrived after RTO,
+ * which indicates that we should follow the traditional RTO recovery,
+ * i.e. mark everything lost and do go-back-N retransmission.
+ */
+static void tcp_enter_frto_loss(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct sk_buff *skb;
+ int cnt = 0;
+
+ tp->sacked_out = 0;
+ tp->lost_out = 0;
+ tp->fackets_out = 0;
+
+ sk_stream_for_retrans_queue(skb, sk) {
+ cnt += tcp_skb_pcount(skb);
+ TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
+ if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED)) {
+
+ /* Do not mark those segments lost that were
+ * forward transmitted after RTO
+ */
+ if (!after(TCP_SKB_CB(skb)->end_seq,
+ tp->frto_highmark)) {
+ TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
+ tp->lost_out += tcp_skb_pcount(skb);
+ }
+ } else {
+ tp->sacked_out += tcp_skb_pcount(skb);
+ tp->fackets_out = cnt;
+ }
+ }
+ tcp_sync_left_out(tp);
+
+ tp->snd_cwnd = tp->frto_counter + tcp_packets_in_flight(tp)+1;
+ tp->snd_cwnd_cnt = 0;
+ tp->snd_cwnd_stamp = tcp_time_stamp;
+ tp->undo_marker = 0;
+ tp->frto_counter = 0;
+
+ tp->reordering = min_t(unsigned int, tp->reordering,
+ sysctl_tcp_reordering);
+ tcp_set_ca_state(tp, TCP_CA_Loss);
+ tp->high_seq = tp->frto_highmark;
+ TCP_ECN_queue_cwr(tp);
+
+ init_bictcp(tp);
+}
+
+void tcp_clear_retrans(struct tcp_sock *tp)
+{
+ tp->left_out = 0;
+ tp->retrans_out = 0;
+
+ tp->fackets_out = 0;
+ tp->sacked_out = 0;
+ tp->lost_out = 0;
+
+ tp->undo_marker = 0;
+ tp->undo_retrans = 0;
+}
+
+/* Enter Loss state. If "how" is not zero, forget all SACK information
+ * and reset tags completely, otherwise preserve SACKs. If receiver
+ * dropped its ofo queue, we will know this due to reneging detection.
+ */
+void tcp_enter_loss(struct sock *sk, int how)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct sk_buff *skb;
+ int cnt = 0;
+
+ /* Reduce ssthresh if it has not yet been made inside this window. */
+ if (tp->ca_state <= TCP_CA_Disorder || tp->snd_una == tp->high_seq ||
+ (tp->ca_state == TCP_CA_Loss && !tp->retransmits)) {
+ tp->prior_ssthresh = tcp_current_ssthresh(tp);
+ tp->snd_ssthresh = tcp_recalc_ssthresh(tp);
+ }
+ tp->snd_cwnd = 1;
+ tp->snd_cwnd_cnt = 0;
+ tp->snd_cwnd_stamp = tcp_time_stamp;
+
+ tcp_clear_retrans(tp);
+
+ /* Push undo marker, if it was plain RTO and nothing
+ * was retransmitted. */
+ if (!how)
+ tp->undo_marker = tp->snd_una;
+
+ sk_stream_for_retrans_queue(skb, sk) {
+ cnt += tcp_skb_pcount(skb);
+ if (TCP_SKB_CB(skb)->sacked&TCPCB_RETRANS)
+ tp->undo_marker = 0;
+ TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED;
+ if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) || how) {
+ TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED;
+ TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
+ tp->lost_out += tcp_skb_pcount(skb);
+ } else {
+ tp->sacked_out += tcp_skb_pcount(skb);
+ tp->fackets_out = cnt;
+ }
+ }
+ tcp_sync_left_out(tp);
+
+ tp->reordering = min_t(unsigned int, tp->reordering,
+ sysctl_tcp_reordering);
+ tcp_set_ca_state(tp, TCP_CA_Loss);
+ tp->high_seq = tp->snd_nxt;
+ TCP_ECN_queue_cwr(tp);
+}
+
+static int tcp_check_sack_reneging(struct sock *sk, struct tcp_sock *tp)
+{
+ struct sk_buff *skb;
+
+ /* If ACK arrived pointing to a remembered SACK,
+ * it means that our remembered SACKs do not reflect
+ * real state of receiver i.e.
+ * receiver _host_ is heavily congested (or buggy).
+ * Do processing similar to RTO timeout.
+ */
+ if ((skb = skb_peek(&sk->sk_write_queue)) != NULL &&
+ (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) {
+ NET_INC_STATS_BH(LINUX_MIB_TCPSACKRENEGING);
+
+ tcp_enter_loss(sk, 1);
+ tp->retransmits++;
+ tcp_retransmit_skb(sk, skb_peek(&sk->sk_write_queue));
+ tcp_reset_xmit_timer(sk, TCP_TIME_RETRANS, tp->rto);
+ return 1;
+ }
+ return 0;
+}
+
+static inline int tcp_fackets_out(struct tcp_sock *tp)
+{
+ return IsReno(tp) ? tp->sacked_out+1 : tp->fackets_out;
+}
+
+static inline int tcp_skb_timedout(struct tcp_sock *tp, struct sk_buff *skb)
+{
+ return (tcp_time_stamp - TCP_SKB_CB(skb)->when > tp->rto);
+}
+
+static inline int tcp_head_timedout(struct sock *sk, struct tcp_sock *tp)
+{
+ return tp->packets_out &&
+ tcp_skb_timedout(tp, skb_peek(&sk->sk_write_queue));
+}
+
+/* Linux NewReno/SACK/FACK/ECN state machine.
+ * --------------------------------------
+ *
+ * "Open" Normal state, no dubious events, fast path.
+ * "Disorder" In all the respects it is "Open",
+ * but requires a bit more attention. It is entered when
+ * we see some SACKs or dupacks. It is split of "Open"
+ * mainly to move some processing from fast path to slow one.
+ * "CWR" CWND was reduced due to some Congestion Notification event.
+ * It can be ECN, ICMP source quench, local device congestion.
+ * "Recovery" CWND was reduced, we are fast-retransmitting.
+ * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
+ *
+ * tcp_fastretrans_alert() is entered:
+ * - each incoming ACK, if state is not "Open"
+ * - when arrived ACK is unusual, namely:
+ * * SACK
+ * * Duplicate ACK.
+ * * ECN ECE.
+ *
+ * Counting packets in flight is pretty simple.
+ *
+ * in_flight = packets_out - left_out + retrans_out
+ *
+ * packets_out is SND.NXT-SND.UNA counted in packets.
+ *
+ * retrans_out is number of retransmitted segments.
+ *
+ * left_out is number of segments left network, but not ACKed yet.
+ *
+ * left_out = sacked_out + lost_out
+ *
+ * sacked_out: Packets, which arrived to receiver out of order
+ * and hence not ACKed. With SACKs this number is simply
+ * amount of SACKed data. Even without SACKs
+ * it is easy to give pretty reliable estimate of this number,
+ * counting duplicate ACKs.
+ *
+ * lost_out: Packets lost by network. TCP has no explicit
+ * "loss notification" feedback from network (for now).
+ * It means that this number can be only _guessed_.
+ * Actually, it is the heuristics to predict lossage that
+ * distinguishes different algorithms.
+ *
+ * F.e. after RTO, when all the queue is considered as lost,
+ * lost_out = packets_out and in_flight = retrans_out.
+ *
+ * Essentially, we have now two algorithms counting
+ * lost packets.
+ *
+ * FACK: It is the simplest heuristics. As soon as we decided
+ * that something is lost, we decide that _all_ not SACKed
+ * packets until the most forward SACK are lost. I.e.
+ * lost_out = fackets_out - sacked_out and left_out = fackets_out.
+ * It is absolutely correct estimate, if network does not reorder
+ * packets. And it loses any connection to reality when reordering
+ * takes place. We use FACK by default until reordering
+ * is suspected on the path to this destination.
+ *
+ * NewReno: when Recovery is entered, we assume that one segment
+ * is lost (classic Reno). While we are in Recovery and
+ * a partial ACK arrives, we assume that one more packet
+ * is lost (NewReno). This heuristics are the same in NewReno
+ * and SACK.
+ *
+ * Imagine, that's all! Forget about all this shamanism about CWND inflation
+ * deflation etc. CWND is real congestion window, never inflated, changes
+ * only according to classic VJ rules.
+ *
+ * Really tricky (and requiring careful tuning) part of algorithm
+ * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
+ * The first determines the moment _when_ we should reduce CWND and,
+ * hence, slow down forward transmission. In fact, it determines the moment
+ * when we decide that hole is caused by loss, rather than by a reorder.
+ *
+ * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
+ * holes, caused by lost packets.
+ *
+ * And the most logically complicated part of algorithm is undo
+ * heuristics. We detect false retransmits due to both too early
+ * fast retransmit (reordering) and underestimated RTO, analyzing
+ * timestamps and D-SACKs. When we detect that some segments were
+ * retransmitted by mistake and CWND reduction was wrong, we undo
+ * window reduction and abort recovery phase. This logic is hidden
+ * inside several functions named tcp_try_undo_<something>.
+ */
+
+/* This function decides, when we should leave Disordered state
+ * and enter Recovery phase, reducing congestion window.
+ *
+ * Main question: may we further continue forward transmission
+ * with the same cwnd?
+ */
+static int tcp_time_to_recover(struct sock *sk, struct tcp_sock *tp)
+{
+ __u32 packets_out;
+
+ /* Trick#1: The loss is proven. */
+ if (tp->lost_out)
+ return 1;
+
+ /* Not-A-Trick#2 : Classic rule... */
+ if (tcp_fackets_out(tp) > tp->reordering)
+ return 1;
+
+ /* Trick#3 : when we use RFC2988 timer restart, fast
+ * retransmit can be triggered by timeout of queue head.
+ */
+ if (tcp_head_timedout(sk, tp))
+ return 1;
+
+ /* Trick#4: It is still not OK... But will it be useful to delay
+ * recovery more?
+ */
+ packets_out = tp->packets_out;
+ if (packets_out <= tp->reordering &&
+ tp->sacked_out >= max_t(__u32, packets_out/2, sysctl_tcp_reordering) &&
+ !tcp_may_send_now(sk, tp)) {
+ /* We have nothing to send. This connection is limited
+ * either by receiver window or by application.
+ */
+ return 1;
+ }
+
+ return 0;
+}
+
+/* If we receive more dupacks than we expected counting segments
+ * in assumption of absent reordering, interpret this as reordering.
+ * The only another reason could be bug in receiver TCP.
+ */
+static void tcp_check_reno_reordering(struct tcp_sock *tp, int addend)
+{
+ u32 holes;
+
+ holes = max(tp->lost_out, 1U);
+ holes = min(holes, tp->packets_out);
+
+ if ((tp->sacked_out + holes) > tp->packets_out) {
+ tp->sacked_out = tp->packets_out - holes;
+ tcp_update_reordering(tp, tp->packets_out+addend, 0);
+ }
+}
+
+/* Emulate SACKs for SACKless connection: account for a new dupack. */
+
+static void tcp_add_reno_sack(struct tcp_sock *tp)
+{
+ tp->sacked_out++;
+ tcp_check_reno_reordering(tp, 0);
+ tcp_sync_left_out(tp);
+}
+
+/* Account for ACK, ACKing some data in Reno Recovery phase. */
+
+static void tcp_remove_reno_sacks(struct sock *sk, struct tcp_sock *tp, int acked)
+{
+ if (acked > 0) {
+ /* One ACK acked hole. The rest eat duplicate ACKs. */
+ if (acked-1 >= tp->sacked_out)
+ tp->sacked_out = 0;
+ else
+ tp->sacked_out -= acked-1;
+ }
+ tcp_check_reno_reordering(tp, acked);
+ tcp_sync_left_out(tp);
+}
+
+static inline void tcp_reset_reno_sack(struct tcp_sock *tp)
+{
+ tp->sacked_out = 0;
+ tp->left_out = tp->lost_out;
+}
+
+/* Mark head of queue up as lost. */
+static void tcp_mark_head_lost(struct sock *sk, struct tcp_sock *tp,
+ int packets, u32 high_seq)
+{
+ struct sk_buff *skb;
+ int cnt = packets;
+
+ BUG_TRAP(cnt <= tp->packets_out);
+
+ sk_stream_for_retrans_queue(skb, sk) {
+ cnt -= tcp_skb_pcount(skb);
+ if (cnt < 0 || after(TCP_SKB_CB(skb)->end_seq, high_seq))
+ break;
+ if (!(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) {
+ TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
+ tp->lost_out += tcp_skb_pcount(skb);
+ }
+ }
+ tcp_sync_left_out(tp);
+}
+
+/* Account newly detected lost packet(s) */
+
+static void tcp_update_scoreboard(struct sock *sk, struct tcp_sock *tp)
+{
+ if (IsFack(tp)) {
+ int lost = tp->fackets_out - tp->reordering;
+ if (lost <= 0)
+ lost = 1;
+ tcp_mark_head_lost(sk, tp, lost, tp->high_seq);
+ } else {
+ tcp_mark_head_lost(sk, tp, 1, tp->high_seq);
+ }
+
+ /* New heuristics: it is possible only after we switched
+ * to restart timer each time when something is ACKed.
+ * Hence, we can detect timed out packets during fast
+ * retransmit without falling to slow start.
+ */
+ if (tcp_head_timedout(sk, tp)) {
+ struct sk_buff *skb;
+
+ sk_stream_for_retrans_queue(skb, sk) {
+ if (tcp_skb_timedout(tp, skb) &&
+ !(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) {
+ TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
+ tp->lost_out += tcp_skb_pcount(skb);
+ }
+ }
+ tcp_sync_left_out(tp);
+ }
+}
+
+/* CWND moderation, preventing bursts due to too big ACKs
+ * in dubious situations.
+ */
+static inline void tcp_moderate_cwnd(struct tcp_sock *tp)
+{
+ tp->snd_cwnd = min(tp->snd_cwnd,
+ tcp_packets_in_flight(tp)+tcp_max_burst(tp));
+ tp->snd_cwnd_stamp = tcp_time_stamp;
+}
+
+/* Decrease cwnd each second ack. */
+
+static void tcp_cwnd_down(struct tcp_sock *tp)
+{
+ int decr = tp->snd_cwnd_cnt + 1;
+ __u32 limit;
+
+ /*
+ * TCP Westwood
+ * Here limit is evaluated as BWestimation*RTTmin (for obtaining it
+ * in packets we use mss_cache). If sysctl_tcp_westwood is off
+ * tcp_westwood_bw_rttmin() returns 0. In such case snd_ssthresh is
+ * still used as usual. It prevents other strange cases in which
+ * BWE*RTTmin could assume value 0. It should not happen but...
+ */
+
+ if (!(limit = tcp_westwood_bw_rttmin(tp)))
+ limit = tp->snd_ssthresh/2;
+
+ tp->snd_cwnd_cnt = decr&1;
+ decr >>= 1;
+
+ if (decr && tp->snd_cwnd > limit)
+ tp->snd_cwnd -= decr;
+
+ tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp)+1);
+ tp->snd_cwnd_stamp = tcp_time_stamp;
+}
+
+/* Nothing was retransmitted or returned timestamp is less
+ * than timestamp of the first retransmission.
+ */
+static inline int tcp_packet_delayed(struct tcp_sock *tp)
+{
+ return !tp->retrans_stamp ||
+ (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
+ (__s32)(tp->rx_opt.rcv_tsecr - tp->retrans_stamp) < 0);
+}
+
+/* Undo procedures. */
+
+#if FASTRETRANS_DEBUG > 1
+static void DBGUNDO(struct sock *sk, struct tcp_sock *tp, const char *msg)
+{
+ struct inet_sock *inet = inet_sk(sk);
+ printk(KERN_DEBUG "Undo %s %u.%u.%u.%u/%u c%u l%u ss%u/%u p%u\n",
+ msg,
+ NIPQUAD(inet->daddr), ntohs(inet->dport),
+ tp->snd_cwnd, tp->left_out,
+ tp->snd_ssthresh, tp->prior_ssthresh,
+ tp->packets_out);
+}
+#else
+#define DBGUNDO(x...) do { } while (0)
+#endif
+
+static void tcp_undo_cwr(struct tcp_sock *tp, int undo)
+{
+ if (tp->prior_ssthresh) {
+ if (tcp_is_bic(tp))
+ tp->snd_cwnd = max(tp->snd_cwnd, tp->bictcp.last_max_cwnd);
+ else
+ tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh<<1);
+
+ if (undo && tp->prior_ssthresh > tp->snd_ssthresh) {
+ tp->snd_ssthresh = tp->prior_ssthresh;
+ TCP_ECN_withdraw_cwr(tp);
+ }
+ } else {
+ tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh);
+ }
+ tcp_moderate_cwnd(tp);
+ tp->snd_cwnd_stamp = tcp_time_stamp;
+}
+
+static inline int tcp_may_undo(struct tcp_sock *tp)
+{
+ return tp->undo_marker &&
+ (!tp->undo_retrans || tcp_packet_delayed(tp));
+}
+
+/* People celebrate: "We love our President!" */
+static int tcp_try_undo_recovery(struct sock *sk, struct tcp_sock *tp)
+{
+ if (tcp_may_undo(tp)) {
+ /* Happy end! We did not retransmit anything
+ * or our original transmission succeeded.
+ */
+ DBGUNDO(sk, tp, tp->ca_state == TCP_CA_Loss ? "loss" : "retrans");
+ tcp_undo_cwr(tp, 1);
+ if (tp->ca_state == TCP_CA_Loss)
+ NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO);
+ else
+ NET_INC_STATS_BH(LINUX_MIB_TCPFULLUNDO);
+ tp->undo_marker = 0;
+ }
+ if (tp->snd_una == tp->high_seq && IsReno(tp)) {
+ /* Hold old state until something *above* high_seq
+ * is ACKed. For Reno it is MUST to prevent false
+ * fast retransmits (RFC2582). SACK TCP is safe. */
+ tcp_moderate_cwnd(tp);
+ return 1;
+ }
+ tcp_set_ca_state(tp, TCP_CA_Open);
+ return 0;
+}
+
+/* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
+static void tcp_try_undo_dsack(struct sock *sk, struct tcp_sock *tp)
+{
+ if (tp->undo_marker && !tp->undo_retrans) {
+ DBGUNDO(sk, tp, "D-SACK");
+ tcp_undo_cwr(tp, 1);
+ tp->undo_marker = 0;
+ NET_INC_STATS_BH(LINUX_MIB_TCPDSACKUNDO);
+ }
+}
+
+/* Undo during fast recovery after partial ACK. */
+
+static int tcp_try_undo_partial(struct sock *sk, struct tcp_sock *tp,
+ int acked)
+{
+ /* Partial ACK arrived. Force Hoe's retransmit. */
+ int failed = IsReno(tp) || tp->fackets_out>tp->reordering;
+
+ if (tcp_may_undo(tp)) {
+ /* Plain luck! Hole if filled with delayed
+ * packet, rather than with a retransmit.
+ */
+ if (tp->retrans_out == 0)
+ tp->retrans_stamp = 0;
+
+ tcp_update_reordering(tp, tcp_fackets_out(tp)+acked, 1);
+
+ DBGUNDO(sk, tp, "Hoe");
+ tcp_undo_cwr(tp, 0);
+ NET_INC_STATS_BH(LINUX_MIB_TCPPARTIALUNDO);
+
+ /* So... Do not make Hoe's retransmit yet.
+ * If the first packet was delayed, the rest
+ * ones are most probably delayed as well.
+ */
+ failed = 0;
+ }
+ return failed;
+}
+
+/* Undo during loss recovery after partial ACK. */
+static int tcp_try_undo_loss(struct sock *sk, struct tcp_sock *tp)
+{
+ if (tcp_may_undo(tp)) {
+ struct sk_buff *skb;
+ sk_stream_for_retrans_queue(skb, sk) {
+ TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
+ }
+ DBGUNDO(sk, tp, "partial loss");
+ tp->lost_out = 0;
+ tp->left_out = tp->sacked_out;
+ tcp_undo_cwr(tp, 1);
+ NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO);
+ tp->retransmits = 0;
+ tp->undo_marker = 0;
+ if (!IsReno(tp))
+ tcp_set_ca_state(tp, TCP_CA_Open);
+ return 1;
+ }
+ return 0;
+}
+
+static inline void tcp_complete_cwr(struct tcp_sock *tp)
+{
+ if (tcp_westwood_cwnd(tp))
+ tp->snd_ssthresh = tp->snd_cwnd;
+ else
+ tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
+ tp->snd_cwnd_stamp = tcp_time_stamp;
+}
+
+static void tcp_try_to_open(struct sock *sk, struct tcp_sock *tp, int flag)
+{
+ tp->left_out = tp->sacked_out;
+
+ if (tp->retrans_out == 0)
+ tp->retrans_stamp = 0;
+
+ if (flag&FLAG_ECE)
+ tcp_enter_cwr(tp);
+
+ if (tp->ca_state != TCP_CA_CWR) {
+ int state = TCP_CA_Open;
+
+ if (tp->left_out || tp->retrans_out || tp->undo_marker)
+ state = TCP_CA_Disorder;
+
+ if (tp->ca_state != state) {
+ tcp_set_ca_state(tp, state);
+ tp->high_seq = tp->snd_nxt;
+ }
+ tcp_moderate_cwnd(tp);
+ } else {
+ tcp_cwnd_down(tp);
+ }
+}
+
+/* Process an event, which can update packets-in-flight not trivially.
+ * Main goal of this function is to calculate new estimate for left_out,
+ * taking into account both packets sitting in receiver's buffer and
+ * packets lost by network.
+ *
+ * Besides that it does CWND reduction, when packet loss is detected
+ * and changes state of machine.
+ *
+ * It does _not_ decide what to send, it is made in function
+ * tcp_xmit_retransmit_queue().
+ */
+static void
+tcp_fastretrans_alert(struct sock *sk, u32 prior_snd_una,
+ int prior_packets, int flag)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ int is_dupack = (tp->snd_una == prior_snd_una && !(flag&FLAG_NOT_DUP));
+
+ /* Some technical things:
+ * 1. Reno does not count dupacks (sacked_out) automatically. */
+ if (!tp->packets_out)
+ tp->sacked_out = 0;
+ /* 2. SACK counts snd_fack in packets inaccurately. */
+ if (tp->sacked_out == 0)
+ tp->fackets_out = 0;
+
+ /* Now state machine starts.
+ * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
+ if (flag&FLAG_ECE)
+ tp->prior_ssthresh = 0;
+
+ /* B. In all the states check for reneging SACKs. */
+ if (tp->sacked_out && tcp_check_sack_reneging(sk, tp))
+ return;
+
+ /* C. Process data loss notification, provided it is valid. */
+ if ((flag&FLAG_DATA_LOST) &&
+ before(tp->snd_una, tp->high_seq) &&
+ tp->ca_state != TCP_CA_Open &&
+ tp->fackets_out > tp->reordering) {
+ tcp_mark_head_lost(sk, tp, tp->fackets_out-tp->reordering, tp->high_seq);
+ NET_INC_STATS_BH(LINUX_MIB_TCPLOSS);
+ }
+
+ /* D. Synchronize left_out to current state. */
+ tcp_sync_left_out(tp);
+
+ /* E. Check state exit conditions. State can be terminated
+ * when high_seq is ACKed. */
+ if (tp->ca_state == TCP_CA_Open) {
+ if (!sysctl_tcp_frto)
+ BUG_TRAP(tp->retrans_out == 0);
+ tp->retrans_stamp = 0;
+ } else if (!before(tp->snd_una, tp->high_seq)) {
+ switch (tp->ca_state) {
+ case TCP_CA_Loss:
+ tp->retransmits = 0;
+ if (tcp_try_undo_recovery(sk, tp))
+ return;
+ break;
+
+ case TCP_CA_CWR:
+ /* CWR is to be held something *above* high_seq
+ * is ACKed for CWR bit to reach receiver. */
+ if (tp->snd_una != tp->high_seq) {
+ tcp_complete_cwr(tp);
+ tcp_set_ca_state(tp, TCP_CA_Open);
+ }
+ break;
+
+ case TCP_CA_Disorder:
+ tcp_try_undo_dsack(sk, tp);
+ if (!tp->undo_marker ||
+ /* For SACK case do not Open to allow to undo
+ * catching for all duplicate ACKs. */
+ IsReno(tp) || tp->snd_una != tp->high_seq) {
+ tp->undo_marker = 0;
+ tcp_set_ca_state(tp, TCP_CA_Open);
+ }
+ break;
+
+ case TCP_CA_Recovery:
+ if (IsReno(tp))
+ tcp_reset_reno_sack(tp);
+ if (tcp_try_undo_recovery(sk, tp))
+ return;
+ tcp_complete_cwr(tp);
+ break;
+ }
+ }
+
+ /* F. Process state. */
+ switch (tp->ca_state) {
+ case TCP_CA_Recovery:
+ if (prior_snd_una == tp->snd_una) {
+ if (IsReno(tp) && is_dupack)
+ tcp_add_reno_sack(tp);
+ } else {
+ int acked = prior_packets - tp->packets_out;
+ if (IsReno(tp))
+ tcp_remove_reno_sacks(sk, tp, acked);
+ is_dupack = tcp_try_undo_partial(sk, tp, acked);
+ }
+ break;
+ case TCP_CA_Loss:
+ if (flag&FLAG_DATA_ACKED)
+ tp->retransmits = 0;
+ if (!tcp_try_undo_loss(sk, tp)) {
+ tcp_moderate_cwnd(tp);
+ tcp_xmit_retransmit_queue(sk);
+ return;
+ }
+ if (tp->ca_state != TCP_CA_Open)
+ return;
+ /* Loss is undone; fall through to processing in Open state. */
+ default:
+ if (IsReno(tp)) {
+ if (tp->snd_una != prior_snd_una)
+ tcp_reset_reno_sack(tp);
+ if (is_dupack)
+ tcp_add_reno_sack(tp);
+ }
+
+ if (tp->ca_state == TCP_CA_Disorder)
+ tcp_try_undo_dsack(sk, tp);
+
+ if (!tcp_time_to_recover(sk, tp)) {
+ tcp_try_to_open(sk, tp, flag);
+ return;
+ }
+
+ /* Otherwise enter Recovery state */
+
+ if (IsReno(tp))
+ NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERY);
+ else
+ NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERY);
+
+ tp->high_seq = tp->snd_nxt;
+ tp->prior_ssthresh = 0;
+ tp->undo_marker = tp->snd_una;
+ tp->undo_retrans = tp->retrans_out;
+
+ if (tp->ca_state < TCP_CA_CWR) {
+ if (!(flag&FLAG_ECE))
+ tp->prior_ssthresh = tcp_current_ssthresh(tp);
+ tp->snd_ssthresh = tcp_recalc_ssthresh(tp);
+ TCP_ECN_queue_cwr(tp);
+ }
+
+ tp->snd_cwnd_cnt = 0;
+ tcp_set_ca_state(tp, TCP_CA_Recovery);
+ }
+
+ if (is_dupack || tcp_head_timedout(sk, tp))
+ tcp_update_scoreboard(sk, tp);
+ tcp_cwnd_down(tp);
+ tcp_xmit_retransmit_queue(sk);
+}
+
+/* Read draft-ietf-tcplw-high-performance before mucking
+ * with this code. (Superceeds RFC1323)
+ */
+static void tcp_ack_saw_tstamp(struct tcp_sock *tp, int flag)
+{
+ __u32 seq_rtt;
+
+ /* RTTM Rule: A TSecr value received in a segment is used to
+ * update the averaged RTT measurement only if the segment
+ * acknowledges some new data, i.e., only if it advances the
+ * left edge of the send window.
+ *
+ * See draft-ietf-tcplw-high-performance-00, section 3.3.
+ * 1998/04/10 Andrey V. Savochkin <saw@msu.ru>
+ *
+ * Changed: reset backoff as soon as we see the first valid sample.
+ * If we do not, we get strongly overstimated rto. With timestamps
+ * samples are accepted even from very old segments: f.e., when rtt=1
+ * increases to 8, we retransmit 5 times and after 8 seconds delayed
+ * answer arrives rto becomes 120 seconds! If at least one of segments
+ * in window is lost... Voila. --ANK (010210)
+ */
+ seq_rtt = tcp_time_stamp - tp->rx_opt.rcv_tsecr;
+ tcp_rtt_estimator(tp, seq_rtt);
+ tcp_set_rto(tp);
+ tp->backoff = 0;
+ tcp_bound_rto(tp);
+}
+
+static void tcp_ack_no_tstamp(struct tcp_sock *tp, u32 seq_rtt, int flag)
+{
+ /* We don't have a timestamp. Can only use
+ * packets that are not retransmitted to determine
+ * rtt estimates. Also, we must not reset the
+ * backoff for rto until we get a non-retransmitted
+ * packet. This allows us to deal with a situation
+ * where the network delay has increased suddenly.
+ * I.e. Karn's algorithm. (SIGCOMM '87, p5.)
+ */
+
+ if (flag & FLAG_RETRANS_DATA_ACKED)
+ return;
+
+ tcp_rtt_estimator(tp, seq_rtt);
+ tcp_set_rto(tp);
+ tp->backoff = 0;
+ tcp_bound_rto(tp);
+}
+
+static inline void tcp_ack_update_rtt(struct tcp_sock *tp,
+ int flag, s32 seq_rtt)
+{
+ /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */
+ if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr)
+ tcp_ack_saw_tstamp(tp, flag);
+ else if (seq_rtt >= 0)
+ tcp_ack_no_tstamp(tp, seq_rtt, flag);
+}
+
+/*
+ * Compute congestion window to use.
+ *
+ * This is from the implementation of BICTCP in
+ * Lison-Xu, Kahaled Harfoush, and Injog Rhee.
+ * "Binary Increase Congestion Control for Fast, Long Distance
+ * Networks" in InfoComm 2004
+ * Available from:
+ * http://www.csc.ncsu.edu/faculty/rhee/export/bitcp.pdf
+ *
+ * Unless BIC is enabled and congestion window is large
+ * this behaves the same as the original Reno.
+ */
+static inline __u32 bictcp_cwnd(struct tcp_sock *tp)
+{
+ /* orignal Reno behaviour */
+ if (!tcp_is_bic(tp))
+ return tp->snd_cwnd;
+
+ if (tp->bictcp.last_cwnd == tp->snd_cwnd &&
+ (s32)(tcp_time_stamp - tp->bictcp.last_stamp) <= (HZ>>5))
+ return tp->bictcp.cnt;
+
+ tp->bictcp.last_cwnd = tp->snd_cwnd;
+ tp->bictcp.last_stamp = tcp_time_stamp;
+
+ /* start off normal */
+ if (tp->snd_cwnd <= sysctl_tcp_bic_low_window)
+ tp->bictcp.cnt = tp->snd_cwnd;
+
+ /* binary increase */
+ else if (tp->snd_cwnd < tp->bictcp.last_max_cwnd) {
+ __u32 dist = (tp->bictcp.last_max_cwnd - tp->snd_cwnd)
+ / BICTCP_B;
+
+ if (dist > BICTCP_MAX_INCREMENT)
+ /* linear increase */
+ tp->bictcp.cnt = tp->snd_cwnd / BICTCP_MAX_INCREMENT;
+ else if (dist <= 1U)
+ /* binary search increase */
+ tp->bictcp.cnt = tp->snd_cwnd * BICTCP_FUNC_OF_MIN_INCR
+ / BICTCP_B;
+ else
+ /* binary search increase */
+ tp->bictcp.cnt = tp->snd_cwnd / dist;
+ } else {
+ /* slow start amd linear increase */
+ if (tp->snd_cwnd < tp->bictcp.last_max_cwnd + BICTCP_B)
+ /* slow start */
+ tp->bictcp.cnt = tp->snd_cwnd * BICTCP_FUNC_OF_MIN_INCR
+ / BICTCP_B;
+ else if (tp->snd_cwnd < tp->bictcp.last_max_cwnd
+ + BICTCP_MAX_INCREMENT*(BICTCP_B-1))
+ /* slow start */
+ tp->bictcp.cnt = tp->snd_cwnd * (BICTCP_B-1)
+ / (tp->snd_cwnd-tp->bictcp.last_max_cwnd);
+ else
+ /* linear increase */
+ tp->bictcp.cnt = tp->snd_cwnd / BICTCP_MAX_INCREMENT;
+ }
+ return tp->bictcp.cnt;
+}
+
+/* This is Jacobson's slow start and congestion avoidance.
+ * SIGCOMM '88, p. 328.
+ */
+static inline void reno_cong_avoid(struct tcp_sock *tp)
+{
+ if (tp->snd_cwnd <= tp->snd_ssthresh) {
+ /* In "safe" area, increase. */
+ if (tp->snd_cwnd < tp->snd_cwnd_clamp)
+ tp->snd_cwnd++;
+ } else {
+ /* In dangerous area, increase slowly.
+ * In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd
+ */
+ if (tp->snd_cwnd_cnt >= bictcp_cwnd(tp)) {
+ if (tp->snd_cwnd < tp->snd_cwnd_clamp)
+ tp->snd_cwnd++;
+ tp->snd_cwnd_cnt=0;
+ } else
+ tp->snd_cwnd_cnt++;
+ }
+ tp->snd_cwnd_stamp = tcp_time_stamp;
+}
+
+/* This is based on the congestion detection/avoidance scheme described in
+ * Lawrence S. Brakmo and Larry L. Peterson.
+ * "TCP Vegas: End to end congestion avoidance on a global internet."
+ * IEEE Journal on Selected Areas in Communication, 13(8):1465--1480,
+ * October 1995. Available from:
+ * ftp://ftp.cs.arizona.edu/xkernel/Papers/jsac.ps
+ *
+ * See http://www.cs.arizona.edu/xkernel/ for their implementation.
+ * The main aspects that distinguish this implementation from the
+ * Arizona Vegas implementation are:
+ * o We do not change the loss detection or recovery mechanisms of
+ * Linux in any way. Linux already recovers from losses quite well,
+ * using fine-grained timers, NewReno, and FACK.
+ * o To avoid the performance penalty imposed by increasing cwnd
+ * only every-other RTT during slow start, we increase during
+ * every RTT during slow start, just like Reno.
+ * o Largely to allow continuous cwnd growth during slow start,
+ * we use the rate at which ACKs come back as the "actual"
+ * rate, rather than the rate at which data is sent.
+ * o To speed convergence to the right rate, we set the cwnd
+ * to achieve the right ("actual") rate when we exit slow start.
+ * o To filter out the noise caused by delayed ACKs, we use the
+ * minimum RTT sample observed during the last RTT to calculate
+ * the actual rate.
+ * o When the sender re-starts from idle, it waits until it has
+ * received ACKs for an entire flight of new data before making
+ * a cwnd adjustment decision. The original Vegas implementation
+ * assumed senders never went idle.
+ */
+static void vegas_cong_avoid(struct tcp_sock *tp, u32 ack, u32 seq_rtt)
+{
+ /* The key players are v_beg_snd_una and v_beg_snd_nxt.
+ *
+ * These are so named because they represent the approximate values
+ * of snd_una and snd_nxt at the beginning of the current RTT. More
+ * precisely, they represent the amount of data sent during the RTT.
+ * At the end of the RTT, when we receive an ACK for v_beg_snd_nxt,
+ * we will calculate that (v_beg_snd_nxt - v_beg_snd_una) outstanding
+ * bytes of data have been ACKed during the course of the RTT, giving
+ * an "actual" rate of:
+ *
+ * (v_beg_snd_nxt - v_beg_snd_una) / (rtt duration)
+ *
+ * Unfortunately, v_beg_snd_una is not exactly equal to snd_una,
+ * because delayed ACKs can cover more than one segment, so they
+ * don't line up nicely with the boundaries of RTTs.
+ *
+ * Another unfortunate fact of life is that delayed ACKs delay the
+ * advance of the left edge of our send window, so that the number
+ * of bytes we send in an RTT is often less than our cwnd will allow.
+ * So we keep track of our cwnd separately, in v_beg_snd_cwnd.
+ */
+
+ if (after(ack, tp->vegas.beg_snd_nxt)) {
+ /* Do the Vegas once-per-RTT cwnd adjustment. */
+ u32 old_wnd, old_snd_cwnd;
+
+
+ /* Here old_wnd is essentially the window of data that was
+ * sent during the previous RTT, and has all
+ * been acknowledged in the course of the RTT that ended
+ * with the ACK we just received. Likewise, old_snd_cwnd
+ * is the cwnd during the previous RTT.
+ */
+ old_wnd = (tp->vegas.beg_snd_nxt - tp->vegas.beg_snd_una) /
+ tp->mss_cache_std;
+ old_snd_cwnd = tp->vegas.beg_snd_cwnd;
+
+ /* Save the extent of the current window so we can use this
+ * at the end of the next RTT.
+ */
+ tp->vegas.beg_snd_una = tp->vegas.beg_snd_nxt;
+ tp->vegas.beg_snd_nxt = tp->snd_nxt;
+ tp->vegas.beg_snd_cwnd = tp->snd_cwnd;
+
+ /* Take into account the current RTT sample too, to
+ * decrease the impact of delayed acks. This double counts
+ * this sample since we count it for the next window as well,
+ * but that's not too awful, since we're taking the min,
+ * rather than averaging.
+ */
+ vegas_rtt_calc(tp, seq_rtt);
+
+ /* We do the Vegas calculations only if we got enough RTT
+ * samples that we can be reasonably sure that we got
+ * at least one RTT sample that wasn't from a delayed ACK.
+ * If we only had 2 samples total,
+ * then that means we're getting only 1 ACK per RTT, which
+ * means they're almost certainly delayed ACKs.
+ * If we have 3 samples, we should be OK.
+ */
+
+ if (tp->vegas.cntRTT <= 2) {
+ /* We don't have enough RTT samples to do the Vegas
+ * calculation, so we'll behave like Reno.
+ */
+ if (tp->snd_cwnd > tp->snd_ssthresh)
+ tp->snd_cwnd++;
+ } else {
+ u32 rtt, target_cwnd, diff;
+
+ /* We have enough RTT samples, so, using the Vegas
+ * algorithm, we determine if we should increase or
+ * decrease cwnd, and by how much.
+ */
+
+ /* Pluck out the RTT we are using for the Vegas
+ * calculations. This is the min RTT seen during the
+ * last RTT. Taking the min filters out the effects
+ * of delayed ACKs, at the cost of noticing congestion
+ * a bit later.
+ */
+ rtt = tp->vegas.minRTT;
+
+ /* Calculate the cwnd we should have, if we weren't
+ * going too fast.
+ *
+ * This is:
+ * (actual rate in segments) * baseRTT
+ * We keep it as a fixed point number with
+ * V_PARAM_SHIFT bits to the right of the binary point.
+ */
+ target_cwnd = ((old_wnd * tp->vegas.baseRTT)
+ << V_PARAM_SHIFT) / rtt;
+
+ /* Calculate the difference between the window we had,
+ * and the window we would like to have. This quantity
+ * is the "Diff" from the Arizona Vegas papers.
+ *
+ * Again, this is a fixed point number with
+ * V_PARAM_SHIFT bits to the right of the binary
+ * point.
+ */
+ diff = (old_wnd << V_PARAM_SHIFT) - target_cwnd;
+
+ if (tp->snd_cwnd < tp->snd_ssthresh) {
+ /* Slow start. */
+ if (diff > sysctl_tcp_vegas_gamma) {
+ /* Going too fast. Time to slow down
+ * and switch to congestion avoidance.
+ */
+ tp->snd_ssthresh = 2;
+
+ /* Set cwnd to match the actual rate
+ * exactly:
+ * cwnd = (actual rate) * baseRTT
+ * Then we add 1 because the integer
+ * truncation robs us of full link
+ * utilization.
+ */
+ tp->snd_cwnd = min(tp->snd_cwnd,
+ (target_cwnd >>
+ V_PARAM_SHIFT)+1);
+
+ }
+ } else {
+ /* Congestion avoidance. */
+ u32 next_snd_cwnd;
+
+ /* Figure out where we would like cwnd
+ * to be.
+ */
+ if (diff > sysctl_tcp_vegas_beta) {
+ /* The old window was too fast, so
+ * we slow down.
+ */
+ next_snd_cwnd = old_snd_cwnd - 1;
+ } else if (diff < sysctl_tcp_vegas_alpha) {
+ /* We don't have enough extra packets
+ * in the network, so speed up.
+ */
+ next_snd_cwnd = old_snd_cwnd + 1;
+ } else {
+ /* Sending just as fast as we
+ * should be.
+ */
+ next_snd_cwnd = old_snd_cwnd;
+ }
+
+ /* Adjust cwnd upward or downward, toward the
+ * desired value.
+ */
+ if (next_snd_cwnd > tp->snd_cwnd)
+ tp->snd_cwnd++;
+ else if (next_snd_cwnd < tp->snd_cwnd)
+ tp->snd_cwnd--;
+ }
+ }
+
+ /* Wipe the slate clean for the next RTT. */
+ tp->vegas.cntRTT = 0;
+ tp->vegas.minRTT = 0x7fffffff;
+ }
+
+ /* The following code is executed for every ack we receive,
+ * except for conditions checked in should_advance_cwnd()
+ * before the call to tcp_cong_avoid(). Mainly this means that
+ * we only execute this code if the ack actually acked some
+ * data.
+ */
+
+ /* If we are in slow start, increase our cwnd in response to this ACK.
+ * (If we are not in slow start then we are in congestion avoidance,
+ * and adjust our congestion window only once per RTT. See the code
+ * above.)
+ */
+ if (tp->snd_cwnd <= tp->snd_ssthresh)
+ tp->snd_cwnd++;
+
+ /* to keep cwnd from growing without bound */
+ tp->snd_cwnd = min_t(u32, tp->snd_cwnd, tp->snd_cwnd_clamp);
+
+ /* Make sure that we are never so timid as to reduce our cwnd below
+ * 2 MSS.
+ *
+ * Going below 2 MSS would risk huge delayed ACKs from our receiver.
+ */
+ tp->snd_cwnd = max(tp->snd_cwnd, 2U);
+
+ tp->snd_cwnd_stamp = tcp_time_stamp;
+}
+
+static inline void tcp_cong_avoid(struct tcp_sock *tp, u32 ack, u32 seq_rtt)
+{
+ if (tcp_vegas_enabled(tp))
+ vegas_cong_avoid(tp, ack, seq_rtt);
+ else
+ reno_cong_avoid(tp);
+}
+
+/* Restart timer after forward progress on connection.
+ * RFC2988 recommends to restart timer to now+rto.
+ */
+
+static inline void tcp_ack_packets_out(struct sock *sk, struct tcp_sock *tp)
+{
+ if (!tp->packets_out) {
+ tcp_clear_xmit_timer(sk, TCP_TIME_RETRANS);
+ } else {
+ tcp_reset_xmit_timer(sk, TCP_TIME_RETRANS, tp->rto);
+ }
+}
+
+/* There is one downside to this scheme. Although we keep the
+ * ACK clock ticking, adjusting packet counters and advancing
+ * congestion window, we do not liberate socket send buffer
+ * space.
+ *
+ * Mucking with skb->truesize and sk->sk_wmem_alloc et al.
+ * then making a write space wakeup callback is a possible
+ * future enhancement. WARNING: it is not trivial to make.
+ */
+static int tcp_tso_acked(struct sock *sk, struct sk_buff *skb,
+ __u32 now, __s32 *seq_rtt)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct tcp_skb_cb *scb = TCP_SKB_CB(skb);
+ __u32 seq = tp->snd_una;
+ __u32 packets_acked;
+ int acked = 0;
+
+ /* If we get here, the whole TSO packet has not been
+ * acked.
+ */
+ BUG_ON(!after(scb->end_seq, seq));
+
+ packets_acked = tcp_skb_pcount(skb);
+ if (tcp_trim_head(sk, skb, seq - scb->seq))
+ return 0;
+ packets_acked -= tcp_skb_pcount(skb);
+
+ if (packets_acked) {
+ __u8 sacked = scb->sacked;
+
+ acked |= FLAG_DATA_ACKED;
+ if (sacked) {
+ if (sacked & TCPCB_RETRANS) {
+ if (sacked & TCPCB_SACKED_RETRANS)
+ tp->retrans_out -= packets_acked;
+ acked |= FLAG_RETRANS_DATA_ACKED;
+ *seq_rtt = -1;
+ } else if (*seq_rtt < 0)
+ *seq_rtt = now - scb->when;
+ if (sacked & TCPCB_SACKED_ACKED)
+ tp->sacked_out -= packets_acked;
+ if (sacked & TCPCB_LOST)
+ tp->lost_out -= packets_acked;
+ if (sacked & TCPCB_URG) {
+ if (tp->urg_mode &&
+ !before(seq, tp->snd_up))
+ tp->urg_mode = 0;
+ }
+ } else if (*seq_rtt < 0)
+ *seq_rtt = now - scb->when;
+
+ if (tp->fackets_out) {
+ __u32 dval = min(tp->fackets_out, packets_acked);
+ tp->fackets_out -= dval;
+ }
+ tp->packets_out -= packets_acked;
+
+ BUG_ON(tcp_skb_pcount(skb) == 0);
+ BUG_ON(!before(scb->seq, scb->end_seq));
+ }
+
+ return acked;
+}
+
+
+/* Remove acknowledged frames from the retransmission queue. */
+static int tcp_clean_rtx_queue(struct sock *sk, __s32 *seq_rtt_p)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct sk_buff *skb;
+ __u32 now = tcp_time_stamp;
+ int acked = 0;
+ __s32 seq_rtt = -1;
+
+ while ((skb = skb_peek(&sk->sk_write_queue)) &&
+ skb != sk->sk_send_head) {
+ struct tcp_skb_cb *scb = TCP_SKB_CB(skb);
+ __u8 sacked = scb->sacked;
+
+ /* If our packet is before the ack sequence we can
+ * discard it as it's confirmed to have arrived at
+ * the other end.
+ */
+ if (after(scb->end_seq, tp->snd_una)) {
+ if (tcp_skb_pcount(skb) > 1)
+ acked |= tcp_tso_acked(sk, skb,
+ now, &seq_rtt);
+ break;
+ }
+
+ /* Initial outgoing SYN's get put onto the write_queue
+ * just like anything else we transmit. It is not
+ * true data, and if we misinform our callers that
+ * this ACK acks real data, we will erroneously exit
+ * connection startup slow start one packet too
+ * quickly. This is severely frowned upon behavior.
+ */
+ if (!(scb->flags & TCPCB_FLAG_SYN)) {
+ acked |= FLAG_DATA_ACKED;
+ } else {
+ acked |= FLAG_SYN_ACKED;
+ tp->retrans_stamp = 0;
+ }
+
+ if (sacked) {
+ if (sacked & TCPCB_RETRANS) {
+ if(sacked & TCPCB_SACKED_RETRANS)
+ tp->retrans_out -= tcp_skb_pcount(skb);
+ acked |= FLAG_RETRANS_DATA_ACKED;
+ seq_rtt = -1;
+ } else if (seq_rtt < 0)
+ seq_rtt = now - scb->when;
+ if (sacked & TCPCB_SACKED_ACKED)
+ tp->sacked_out -= tcp_skb_pcount(skb);
+ if (sacked & TCPCB_LOST)
+ tp->lost_out -= tcp_skb_pcount(skb);
+ if (sacked & TCPCB_URG) {
+ if (tp->urg_mode &&
+ !before(scb->end_seq, tp->snd_up))
+ tp->urg_mode = 0;
+ }
+ } else if (seq_rtt < 0)
+ seq_rtt = now - scb->when;
+ tcp_dec_pcount_approx(&tp->fackets_out, skb);
+ tcp_packets_out_dec(tp, skb);
+ __skb_unlink(skb, skb->list);
+ sk_stream_free_skb(sk, skb);
+ }
+
+ if (acked&FLAG_ACKED) {
+ tcp_ack_update_rtt(tp, acked, seq_rtt);
+ tcp_ack_packets_out(sk, tp);
+ }
+
+#if FASTRETRANS_DEBUG > 0
+ BUG_TRAP((int)tp->sacked_out >= 0);
+ BUG_TRAP((int)tp->lost_out >= 0);
+ BUG_TRAP((int)tp->retrans_out >= 0);
+ if (!tp->packets_out && tp->rx_opt.sack_ok) {
+ if (tp->lost_out) {
+ printk(KERN_DEBUG "Leak l=%u %d\n",
+ tp->lost_out, tp->ca_state);
+ tp->lost_out = 0;
+ }
+ if (tp->sacked_out) {
+ printk(KERN_DEBUG "Leak s=%u %d\n",
+ tp->sacked_out, tp->ca_state);
+ tp->sacked_out = 0;
+ }
+ if (tp->retrans_out) {
+ printk(KERN_DEBUG "Leak r=%u %d\n",
+ tp->retrans_out, tp->ca_state);
+ tp->retrans_out = 0;
+ }
+ }
+#endif
+ *seq_rtt_p = seq_rtt;
+ return acked;
+}
+
+static void tcp_ack_probe(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ /* Was it a usable window open? */
+
+ if (!after(TCP_SKB_CB(sk->sk_send_head)->end_seq,
+ tp->snd_una + tp->snd_wnd)) {
+ tp->backoff = 0;
+ tcp_clear_xmit_timer(sk, TCP_TIME_PROBE0);
+ /* Socket must be waked up by subsequent tcp_data_snd_check().
+ * This function is not for random using!
+ */
+ } else {
+ tcp_reset_xmit_timer(sk, TCP_TIME_PROBE0,
+ min(tp->rto << tp->backoff, TCP_RTO_MAX));
+ }
+}
+
+static inline int tcp_ack_is_dubious(struct tcp_sock *tp, int flag)
+{
+ return (!(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) ||
+ tp->ca_state != TCP_CA_Open);
+}
+
+static inline int tcp_may_raise_cwnd(struct tcp_sock *tp, int flag)
+{
+ return (!(flag & FLAG_ECE) || tp->snd_cwnd < tp->snd_ssthresh) &&
+ !((1<<tp->ca_state)&(TCPF_CA_Recovery|TCPF_CA_CWR));
+}
+
+/* Check that window update is acceptable.
+ * The function assumes that snd_una<=ack<=snd_next.
+ */
+static inline int tcp_may_update_window(struct tcp_sock *tp, u32 ack,
+ u32 ack_seq, u32 nwin)
+{
+ return (after(ack, tp->snd_una) ||
+ after(ack_seq, tp->snd_wl1) ||
+ (ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd));
+}
+
+/* Update our send window.
+ *
+ * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
+ * and in FreeBSD. NetBSD's one is even worse.) is wrong.
+ */
+static int tcp_ack_update_window(struct sock *sk, struct tcp_sock *tp,
+ struct sk_buff *skb, u32 ack, u32 ack_seq)
+{
+ int flag = 0;
+ u32 nwin = ntohs(skb->h.th->window);
+
+ if (likely(!skb->h.th->syn))
+ nwin <<= tp->rx_opt.snd_wscale;
+
+ if (tcp_may_update_window(tp, ack, ack_seq, nwin)) {
+ flag |= FLAG_WIN_UPDATE;
+ tcp_update_wl(tp, ack, ack_seq);
+
+ if (tp->snd_wnd != nwin) {
+ tp->snd_wnd = nwin;
+
+ /* Note, it is the only place, where
+ * fast path is recovered for sending TCP.
+ */
+ tcp_fast_path_check(sk, tp);
+
+ if (nwin > tp->max_window) {
+ tp->max_window = nwin;
+ tcp_sync_mss(sk, tp->pmtu_cookie);
+ }
+ }
+ }
+
+ tp->snd_una = ack;
+
+ return flag;
+}
+
+static void tcp_process_frto(struct sock *sk, u32 prior_snd_una)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ tcp_sync_left_out(tp);
+
+ if (tp->snd_una == prior_snd_una ||
+ !before(tp->snd_una, tp->frto_highmark)) {
+ /* RTO was caused by loss, start retransmitting in
+ * go-back-N slow start
+ */
+ tcp_enter_frto_loss(sk);
+ return;
+ }
+
+ if (tp->frto_counter == 1) {
+ /* First ACK after RTO advances the window: allow two new
+ * segments out.
+ */
+ tp->snd_cwnd = tcp_packets_in_flight(tp) + 2;
+ } else {
+ /* Also the second ACK after RTO advances the window.
+ * The RTO was likely spurious. Reduce cwnd and continue
+ * in congestion avoidance
+ */
+ tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
+ tcp_moderate_cwnd(tp);
+ }
+
+ /* F-RTO affects on two new ACKs following RTO.
+ * At latest on third ACK the TCP behavor is back to normal.
+ */
+ tp->frto_counter = (tp->frto_counter + 1) % 3;
+}
+
+/*
+ * TCP Westwood+
+ */
+
+/*
+ * @init_westwood
+ * This function initializes fields used in TCP Westwood+. We can't
+ * get no information about RTTmin at this time so we simply set it to
+ * TCP_WESTWOOD_INIT_RTT. This value was chosen to be too conservative
+ * since in this way we're sure it will be updated in a consistent
+ * way as soon as possible. It will reasonably happen within the first
+ * RTT period of the connection lifetime.
+ */
+
+static void init_westwood(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ tp->westwood.bw_ns_est = 0;
+ tp->westwood.bw_est = 0;
+ tp->westwood.accounted = 0;
+ tp->westwood.cumul_ack = 0;
+ tp->westwood.rtt_win_sx = tcp_time_stamp;
+ tp->westwood.rtt = TCP_WESTWOOD_INIT_RTT;
+ tp->westwood.rtt_min = TCP_WESTWOOD_INIT_RTT;
+ tp->westwood.snd_una = tp->snd_una;
+}
+
+/*
+ * @westwood_do_filter
+ * Low-pass filter. Implemented using constant coeffients.
+ */
+
+static inline __u32 westwood_do_filter(__u32 a, __u32 b)
+{
+ return (((7 * a) + b) >> 3);
+}
+
+static void westwood_filter(struct sock *sk, __u32 delta)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ tp->westwood.bw_ns_est =
+ westwood_do_filter(tp->westwood.bw_ns_est,
+ tp->westwood.bk / delta);
+ tp->westwood.bw_est =
+ westwood_do_filter(tp->westwood.bw_est,
+ tp->westwood.bw_ns_est);
+}
+
+/*
+ * @westwood_update_rttmin
+ * It is used to update RTTmin. In this case we MUST NOT use
+ * WESTWOOD_RTT_MIN minimum bound since we could be on a LAN!
+ */
+
+static inline __u32 westwood_update_rttmin(const struct sock *sk)
+{
+ const struct tcp_sock *tp = tcp_sk(sk);
+ __u32 rttmin = tp->westwood.rtt_min;
+
+ if (tp->westwood.rtt != 0 &&
+ (tp->westwood.rtt < tp->westwood.rtt_min || !rttmin))
+ rttmin = tp->westwood.rtt;
+
+ return rttmin;
+}
+
+/*
+ * @westwood_acked
+ * Evaluate increases for dk.
+ */
+
+static inline __u32 westwood_acked(const struct sock *sk)
+{
+ const struct tcp_sock *tp = tcp_sk(sk);
+
+ return tp->snd_una - tp->westwood.snd_una;
+}
+
+/*
+ * @westwood_new_window
+ * It evaluates if we are receiving data inside the same RTT window as
+ * when we started.
+ * Return value:
+ * It returns 0 if we are still evaluating samples in the same RTT
+ * window, 1 if the sample has to be considered in the next window.
+ */
+
+static int westwood_new_window(const struct sock *sk)
+{
+ const struct tcp_sock *tp = tcp_sk(sk);
+ __u32 left_bound;
+ __u32 rtt;
+ int ret = 0;
+
+ left_bound = tp->westwood.rtt_win_sx;
+ rtt = max(tp->westwood.rtt, (u32) TCP_WESTWOOD_RTT_MIN);
+
+ /*
+ * A RTT-window has passed. Be careful since if RTT is less than
+ * 50ms we don't filter but we continue 'building the sample'.
+ * This minimum limit was choosen since an estimation on small
+ * time intervals is better to avoid...
+ * Obvioulsy on a LAN we reasonably will always have
+ * right_bound = left_bound + WESTWOOD_RTT_MIN
+ */
+
+ if ((left_bound + rtt) < tcp_time_stamp)
+ ret = 1;
+
+ return ret;
+}
+
+/*
+ * @westwood_update_window
+ * It updates RTT evaluation window if it is the right moment to do
+ * it. If so it calls filter for evaluating bandwidth.
+ */
+
+static void __westwood_update_window(struct sock *sk, __u32 now)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ __u32 delta = now - tp->westwood.rtt_win_sx;
+
+ if (delta) {
+ if (tp->westwood.rtt)
+ westwood_filter(sk, delta);
+
+ tp->westwood.bk = 0;
+ tp->westwood.rtt_win_sx = tcp_time_stamp;
+ }
+}
+
+
+static void westwood_update_window(struct sock *sk, __u32 now)
+{
+ if (westwood_new_window(sk))
+ __westwood_update_window(sk, now);
+}
+
+/*
+ * @__tcp_westwood_fast_bw
+ * It is called when we are in fast path. In particular it is called when
+ * header prediction is successfull. In such case infact update is
+ * straight forward and doesn't need any particular care.
+ */
+
+static void __tcp_westwood_fast_bw(struct sock *sk, struct sk_buff *skb)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ westwood_update_window(sk, tcp_time_stamp);
+
+ tp->westwood.bk += westwood_acked(sk);
+ tp->westwood.snd_una = tp->snd_una;
+ tp->westwood.rtt_min = westwood_update_rttmin(sk);
+}
+
+static inline void tcp_westwood_fast_bw(struct sock *sk, struct sk_buff *skb)
+{
+ if (tcp_is_westwood(tcp_sk(sk)))
+ __tcp_westwood_fast_bw(sk, skb);
+}
+
+
+/*
+ * @westwood_dupack_update
+ * It updates accounted and cumul_ack when receiving a dupack.
+ */
+
+static void westwood_dupack_update(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ tp->westwood.accounted += tp->mss_cache_std;
+ tp->westwood.cumul_ack = tp->mss_cache_std;
+}
+
+static inline int westwood_may_change_cumul(struct tcp_sock *tp)
+{
+ return (tp->westwood.cumul_ack > tp->mss_cache_std);
+}
+
+static inline void westwood_partial_update(struct tcp_sock *tp)
+{
+ tp->westwood.accounted -= tp->westwood.cumul_ack;
+ tp->westwood.cumul_ack = tp->mss_cache_std;
+}
+
+static inline void westwood_complete_update(struct tcp_sock *tp)
+{
+ tp->westwood.cumul_ack -= tp->westwood.accounted;
+ tp->westwood.accounted = 0;
+}
+
+/*
+ * @westwood_acked_count
+ * This function evaluates cumul_ack for evaluating dk in case of
+ * delayed or partial acks.
+ */
+
+static inline __u32 westwood_acked_count(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ tp->westwood.cumul_ack = westwood_acked(sk);
+
+ /* If cumul_ack is 0 this is a dupack since it's not moving
+ * tp->snd_una.
+ */
+ if (!(tp->westwood.cumul_ack))
+ westwood_dupack_update(sk);
+
+ if (westwood_may_change_cumul(tp)) {
+ /* Partial or delayed ack */
+ if (tp->westwood.accounted >= tp->westwood.cumul_ack)
+ westwood_partial_update(tp);
+ else
+ westwood_complete_update(tp);
+ }
+
+ tp->westwood.snd_una = tp->snd_una;
+
+ return tp->westwood.cumul_ack;
+}
+
+
+/*
+ * @__tcp_westwood_slow_bw
+ * It is called when something is going wrong..even if there could
+ * be no problems! Infact a simple delayed packet may trigger a
+ * dupack. But we need to be careful in such case.
+ */
+
+static void __tcp_westwood_slow_bw(struct sock *sk, struct sk_buff *skb)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ westwood_update_window(sk, tcp_time_stamp);
+
+ tp->westwood.bk += westwood_acked_count(sk);
+ tp->westwood.rtt_min = westwood_update_rttmin(sk);
+}
+
+static inline void tcp_westwood_slow_bw(struct sock *sk, struct sk_buff *skb)
+{
+ if (tcp_is_westwood(tcp_sk(sk)))
+ __tcp_westwood_slow_bw(sk, skb);
+}
+
+/* This routine deals with incoming acks, but not outgoing ones. */
+static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ u32 prior_snd_una = tp->snd_una;
+ u32 ack_seq = TCP_SKB_CB(skb)->seq;
+ u32 ack = TCP_SKB_CB(skb)->ack_seq;
+ u32 prior_in_flight;
+ s32 seq_rtt;
+ int prior_packets;
+
+ /* If the ack is newer than sent or older than previous acks
+ * then we can probably ignore it.
+ */
+ if (after(ack, tp->snd_nxt))
+ goto uninteresting_ack;
+
+ if (before(ack, prior_snd_una))
+ goto old_ack;
+
+ if (!(flag&FLAG_SLOWPATH) && after(ack, prior_snd_una)) {
+ /* Window is constant, pure forward advance.
+ * No more checks are required.
+ * Note, we use the fact that SND.UNA>=SND.WL2.
+ */
+ tcp_update_wl(tp, ack, ack_seq);
+ tp->snd_una = ack;
+ tcp_westwood_fast_bw(sk, skb);
+ flag |= FLAG_WIN_UPDATE;
+
+ NET_INC_STATS_BH(LINUX_MIB_TCPHPACKS);
+ } else {
+ if (ack_seq != TCP_SKB_CB(skb)->end_seq)
+ flag |= FLAG_DATA;
+ else
+ NET_INC_STATS_BH(LINUX_MIB_TCPPUREACKS);
+
+ flag |= tcp_ack_update_window(sk, tp, skb, ack, ack_seq);
+
+ if (TCP_SKB_CB(skb)->sacked)
+ flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una);
+
+ if (TCP_ECN_rcv_ecn_echo(tp, skb->h.th))
+ flag |= FLAG_ECE;
+
+ tcp_westwood_slow_bw(sk,skb);
+ }
+
+ /* We passed data and got it acked, remove any soft error
+ * log. Something worked...
+ */
+ sk->sk_err_soft = 0;
+ tp->rcv_tstamp = tcp_time_stamp;
+ prior_packets = tp->packets_out;
+ if (!prior_packets)
+ goto no_queue;
+
+ prior_in_flight = tcp_packets_in_flight(tp);
+
+ /* See if we can take anything off of the retransmit queue. */
+ flag |= tcp_clean_rtx_queue(sk, &seq_rtt);
+
+ if (tp->frto_counter)
+ tcp_process_frto(sk, prior_snd_una);
+
+ if (tcp_ack_is_dubious(tp, flag)) {
+ /* Advanve CWND, if state allows this. */
+ if ((flag & FLAG_DATA_ACKED) &&
+ (tcp_vegas_enabled(tp) || prior_in_flight >= tp->snd_cwnd) &&
+ tcp_may_raise_cwnd(tp, flag))
+ tcp_cong_avoid(tp, ack, seq_rtt);
+ tcp_fastretrans_alert(sk, prior_snd_una, prior_packets, flag);
+ } else {
+ if ((flag & FLAG_DATA_ACKED) &&
+ (tcp_vegas_enabled(tp) || prior_in_flight >= tp->snd_cwnd))
+ tcp_cong_avoid(tp, ack, seq_rtt);
+ }
+
+ if ((flag & FLAG_FORWARD_PROGRESS) || !(flag&FLAG_NOT_DUP))
+ dst_confirm(sk->sk_dst_cache);
+
+ return 1;
+
+no_queue:
+ tp->probes_out = 0;
+
+ /* If this ack opens up a zero window, clear backoff. It was
+ * being used to time the probes, and is probably far higher than
+ * it needs to be for normal retransmission.
+ */
+ if (sk->sk_send_head)
+ tcp_ack_probe(sk);
+ return 1;
+
+old_ack:
+ if (TCP_SKB_CB(skb)->sacked)
+ tcp_sacktag_write_queue(sk, skb, prior_snd_una);
+
+uninteresting_ack:
+ SOCK_DEBUG(sk, "Ack %u out of %u:%u\n", ack, tp->snd_una, tp->snd_nxt);
+ return 0;
+}
+
+
+/* Look for tcp options. Normally only called on SYN and SYNACK packets.
+ * But, this can also be called on packets in the established flow when
+ * the fast version below fails.
+ */
+void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx, int estab)
+{
+ unsigned char *ptr;
+ struct tcphdr *th = skb->h.th;
+ int length=(th->doff*4)-sizeof(struct tcphdr);
+
+ ptr = (unsigned char *)(th + 1);
+ opt_rx->saw_tstamp = 0;
+
+ while(length>0) {
+ int opcode=*ptr++;
+ int opsize;
+
+ switch (opcode) {
+ case TCPOPT_EOL:
+ return;
+ case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */
+ length--;
+ continue;
+ default:
+ opsize=*ptr++;
+ if (opsize < 2) /* "silly options" */
+ return;
+ if (opsize > length)
+ return; /* don't parse partial options */
+ switch(opcode) {
+ case TCPOPT_MSS:
+ if(opsize==TCPOLEN_MSS && th->syn && !estab) {
+ u16 in_mss = ntohs(get_unaligned((__u16 *)ptr));
+ if (in_mss) {
+ if (opt_rx->user_mss && opt_rx->user_mss < in_mss)
+ in_mss = opt_rx->user_mss;
+ opt_rx->mss_clamp = in_mss;
+ }
+ }
+ break;
+ case TCPOPT_WINDOW:
+ if(opsize==TCPOLEN_WINDOW && th->syn && !estab)
+ if (sysctl_tcp_window_scaling) {
+ __u8 snd_wscale = *(__u8 *) ptr;
+ opt_rx->wscale_ok = 1;
+ if (snd_wscale > 14) {
+ if(net_ratelimit())
+ printk(KERN_INFO "tcp_parse_options: Illegal window "
+ "scaling value %d >14 received.\n",
+ snd_wscale);
+ snd_wscale = 14;
+ }
+ opt_rx->snd_wscale = snd_wscale;
+ }
+ break;
+ case TCPOPT_TIMESTAMP:
+ if(opsize==TCPOLEN_TIMESTAMP) {
+ if ((estab && opt_rx->tstamp_ok) ||
+ (!estab && sysctl_tcp_timestamps)) {
+ opt_rx->saw_tstamp = 1;
+ opt_rx->rcv_tsval = ntohl(get_unaligned((__u32 *)ptr));
+ opt_rx->rcv_tsecr = ntohl(get_unaligned((__u32 *)(ptr+4)));
+ }
+ }
+ break;
+ case TCPOPT_SACK_PERM:
+ if(opsize==TCPOLEN_SACK_PERM && th->syn && !estab) {
+ if (sysctl_tcp_sack) {
+ opt_rx->sack_ok = 1;
+ tcp_sack_reset(opt_rx);
+ }
+ }
+ break;
+
+ case TCPOPT_SACK:
+ if((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) &&
+ !((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) &&
+ opt_rx->sack_ok) {
+ TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th;
+ }
+ };
+ ptr+=opsize-2;
+ length-=opsize;
+ };
+ }
+}
+
+/* Fast parse options. This hopes to only see timestamps.
+ * If it is wrong it falls back on tcp_parse_options().
+ */
+static inline int tcp_fast_parse_options(struct sk_buff *skb, struct tcphdr *th,
+ struct tcp_sock *tp)
+{
+ if (th->doff == sizeof(struct tcphdr)>>2) {
+ tp->rx_opt.saw_tstamp = 0;
+ return 0;
+ } else if (tp->rx_opt.tstamp_ok &&
+ th->doff == (sizeof(struct tcphdr)>>2)+(TCPOLEN_TSTAMP_ALIGNED>>2)) {
+ __u32 *ptr = (__u32 *)(th + 1);
+ if (*ptr == ntohl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
+ | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) {
+ tp->rx_opt.saw_tstamp = 1;
+ ++ptr;
+ tp->rx_opt.rcv_tsval = ntohl(*ptr);
+ ++ptr;
+ tp->rx_opt.rcv_tsecr = ntohl(*ptr);
+ return 1;
+ }
+ }
+ tcp_parse_options(skb, &tp->rx_opt, 1);
+ return 1;
+}
+
+static inline void tcp_store_ts_recent(struct tcp_sock *tp)
+{
+ tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval;
+ tp->rx_opt.ts_recent_stamp = xtime.tv_sec;
+}
+
+static inline void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq)
+{
+ if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) {
+ /* PAWS bug workaround wrt. ACK frames, the PAWS discard
+ * extra check below makes sure this can only happen
+ * for pure ACK frames. -DaveM
+ *
+ * Not only, also it occurs for expired timestamps.
+ */
+
+ if((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) >= 0 ||
+ xtime.tv_sec >= tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS)
+ tcp_store_ts_recent(tp);
+ }
+}
+
+/* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
+ *
+ * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
+ * it can pass through stack. So, the following predicate verifies that
+ * this segment is not used for anything but congestion avoidance or
+ * fast retransmit. Moreover, we even are able to eliminate most of such
+ * second order effects, if we apply some small "replay" window (~RTO)
+ * to timestamp space.
+ *
+ * All these measures still do not guarantee that we reject wrapped ACKs
+ * on networks with high bandwidth, when sequence space is recycled fastly,
+ * but it guarantees that such events will be very rare and do not affect
+ * connection seriously. This doesn't look nice, but alas, PAWS is really
+ * buggy extension.
+ *
+ * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
+ * states that events when retransmit arrives after original data are rare.
+ * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
+ * the biggest problem on large power networks even with minor reordering.
+ * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
+ * up to bandwidth of 18Gigabit/sec. 8) ]
+ */
+
+static int tcp_disordered_ack(struct tcp_sock *tp, struct sk_buff *skb)
+{
+ struct tcphdr *th = skb->h.th;
+ u32 seq = TCP_SKB_CB(skb)->seq;
+ u32 ack = TCP_SKB_CB(skb)->ack_seq;
+
+ return (/* 1. Pure ACK with correct sequence number. */
+ (th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) &&
+
+ /* 2. ... and duplicate ACK. */
+ ack == tp->snd_una &&
+
+ /* 3. ... and does not update window. */
+ !tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) &&
+
+ /* 4. ... and sits in replay window. */
+ (s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) <= (tp->rto*1024)/HZ);
+}
+
+static inline int tcp_paws_discard(struct tcp_sock *tp, struct sk_buff *skb)
+{
+ return ((s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) > TCP_PAWS_WINDOW &&
+ xtime.tv_sec < tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS &&
+ !tcp_disordered_ack(tp, skb));
+}
+
+/* Check segment sequence number for validity.
+ *
+ * Segment controls are considered valid, if the segment
+ * fits to the window after truncation to the window. Acceptability
+ * of data (and SYN, FIN, of course) is checked separately.
+ * See tcp_data_queue(), for example.
+ *
+ * Also, controls (RST is main one) are accepted using RCV.WUP instead
+ * of RCV.NXT. Peer still did not advance his SND.UNA when we
+ * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
+ * (borrowed from freebsd)
+ */
+
+static inline int tcp_sequence(struct tcp_sock *tp, u32 seq, u32 end_seq)
+{
+ return !before(end_seq, tp->rcv_wup) &&
+ !after(seq, tp->rcv_nxt + tcp_receive_window(tp));
+}
+
+/* When we get a reset we do this. */
+static void tcp_reset(struct sock *sk)
+{
+ /* We want the right error as BSD sees it (and indeed as we do). */
+ switch (sk->sk_state) {
+ case TCP_SYN_SENT:
+ sk->sk_err = ECONNREFUSED;
+ break;
+ case TCP_CLOSE_WAIT:
+ sk->sk_err = EPIPE;
+ break;
+ case TCP_CLOSE:
+ return;
+ default:
+ sk->sk_err = ECONNRESET;
+ }
+
+ if (!sock_flag(sk, SOCK_DEAD))
+ sk->sk_error_report(sk);
+
+ tcp_done(sk);
+}
+
+/*
+ * Process the FIN bit. This now behaves as it is supposed to work
+ * and the FIN takes effect when it is validly part of sequence
+ * space. Not before when we get holes.
+ *
+ * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
+ * (and thence onto LAST-ACK and finally, CLOSE, we never enter
+ * TIME-WAIT)
+ *
+ * If we are in FINWAIT-1, a received FIN indicates simultaneous
+ * close and we go into CLOSING (and later onto TIME-WAIT)
+ *
+ * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
+ */
+static void tcp_fin(struct sk_buff *skb, struct sock *sk, struct tcphdr *th)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ tcp_schedule_ack(tp);
+
+ sk->sk_shutdown |= RCV_SHUTDOWN;
+ sock_set_flag(sk, SOCK_DONE);
+
+ switch (sk->sk_state) {
+ case TCP_SYN_RECV:
+ case TCP_ESTABLISHED:
+ /* Move to CLOSE_WAIT */
+ tcp_set_state(sk, TCP_CLOSE_WAIT);
+ tp->ack.pingpong = 1;
+ break;
+
+ case TCP_CLOSE_WAIT:
+ case TCP_CLOSING:
+ /* Received a retransmission of the FIN, do
+ * nothing.
+ */
+ break;
+ case TCP_LAST_ACK:
+ /* RFC793: Remain in the LAST-ACK state. */
+ break;
+
+ case TCP_FIN_WAIT1:
+ /* This case occurs when a simultaneous close
+ * happens, we must ack the received FIN and
+ * enter the CLOSING state.
+ */
+ tcp_send_ack(sk);
+ tcp_set_state(sk, TCP_CLOSING);
+ break;
+ case TCP_FIN_WAIT2:
+ /* Received a FIN -- send ACK and enter TIME_WAIT. */
+ tcp_send_ack(sk);
+ tcp_time_wait(sk, TCP_TIME_WAIT, 0);
+ break;
+ default:
+ /* Only TCP_LISTEN and TCP_CLOSE are left, in these
+ * cases we should never reach this piece of code.
+ */
+ printk(KERN_ERR "%s: Impossible, sk->sk_state=%d\n",
+ __FUNCTION__, sk->sk_state);
+ break;
+ };
+
+ /* It _is_ possible, that we have something out-of-order _after_ FIN.
+ * Probably, we should reset in this case. For now drop them.
+ */
+ __skb_queue_purge(&tp->out_of_order_queue);
+ if (tp->rx_opt.sack_ok)
+ tcp_sack_reset(&tp->rx_opt);
+ sk_stream_mem_reclaim(sk);
+
+ if (!sock_flag(sk, SOCK_DEAD)) {
+ sk->sk_state_change(sk);
+
+ /* Do not send POLL_HUP for half duplex close. */
+ if (sk->sk_shutdown == SHUTDOWN_MASK ||
+ sk->sk_state == TCP_CLOSE)
+ sk_wake_async(sk, 1, POLL_HUP);
+ else
+ sk_wake_async(sk, 1, POLL_IN);
+ }
+}
+
+static __inline__ int
+tcp_sack_extend(struct tcp_sack_block *sp, u32 seq, u32 end_seq)
+{
+ if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) {
+ if (before(seq, sp->start_seq))
+ sp->start_seq = seq;
+ if (after(end_seq, sp->end_seq))
+ sp->end_seq = end_seq;
+ return 1;
+ }
+ return 0;
+}
+
+static inline void tcp_dsack_set(struct tcp_sock *tp, u32 seq, u32 end_seq)
+{
+ if (tp->rx_opt.sack_ok && sysctl_tcp_dsack) {
+ if (before(seq, tp->rcv_nxt))
+ NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOLDSENT);
+ else
+ NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFOSENT);
+
+ tp->rx_opt.dsack = 1;
+ tp->duplicate_sack[0].start_seq = seq;
+ tp->duplicate_sack[0].end_seq = end_seq;
+ tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + 1, 4 - tp->rx_opt.tstamp_ok);
+ }
+}
+
+static inline void tcp_dsack_extend(struct tcp_sock *tp, u32 seq, u32 end_seq)
+{
+ if (!tp->rx_opt.dsack)
+ tcp_dsack_set(tp, seq, end_seq);
+ else
+ tcp_sack_extend(tp->duplicate_sack, seq, end_seq);
+}
+
+static void tcp_send_dupack(struct sock *sk, struct sk_buff *skb)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
+ before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
+ NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST);
+ tcp_enter_quickack_mode(tp);
+
+ if (tp->rx_opt.sack_ok && sysctl_tcp_dsack) {
+ u32 end_seq = TCP_SKB_CB(skb)->end_seq;
+
+ if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt))
+ end_seq = tp->rcv_nxt;
+ tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, end_seq);
+ }
+ }
+
+ tcp_send_ack(sk);
+}
+
+/* These routines update the SACK block as out-of-order packets arrive or
+ * in-order packets close up the sequence space.
+ */
+static void tcp_sack_maybe_coalesce(struct tcp_sock *tp)
+{
+ int this_sack;
+ struct tcp_sack_block *sp = &tp->selective_acks[0];
+ struct tcp_sack_block *swalk = sp+1;
+
+ /* See if the recent change to the first SACK eats into
+ * or hits the sequence space of other SACK blocks, if so coalesce.
+ */
+ for (this_sack = 1; this_sack < tp->rx_opt.num_sacks; ) {
+ if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) {
+ int i;
+
+ /* Zap SWALK, by moving every further SACK up by one slot.
+ * Decrease num_sacks.
+ */
+ tp->rx_opt.num_sacks--;
+ tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok);
+ for(i=this_sack; i < tp->rx_opt.num_sacks; i++)
+ sp[i] = sp[i+1];
+ continue;
+ }
+ this_sack++, swalk++;
+ }
+}
+
+static __inline__ void tcp_sack_swap(struct tcp_sack_block *sack1, struct tcp_sack_block *sack2)
+{
+ __u32 tmp;
+
+ tmp = sack1->start_seq;
+ sack1->start_seq = sack2->start_seq;
+ sack2->start_seq = tmp;
+
+ tmp = sack1->end_seq;
+ sack1->end_seq = sack2->end_seq;
+ sack2->end_seq = tmp;
+}
+
+static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct tcp_sack_block *sp = &tp->selective_acks[0];
+ int cur_sacks = tp->rx_opt.num_sacks;
+ int this_sack;
+
+ if (!cur_sacks)
+ goto new_sack;
+
+ for (this_sack=0; this_sack<cur_sacks; this_sack++, sp++) {
+ if (tcp_sack_extend(sp, seq, end_seq)) {
+ /* Rotate this_sack to the first one. */
+ for (; this_sack>0; this_sack--, sp--)
+ tcp_sack_swap(sp, sp-1);
+ if (cur_sacks > 1)
+ tcp_sack_maybe_coalesce(tp);
+ return;
+ }
+ }
+
+ /* Could not find an adjacent existing SACK, build a new one,
+ * put it at the front, and shift everyone else down. We
+ * always know there is at least one SACK present already here.
+ *
+ * If the sack array is full, forget about the last one.
+ */
+ if (this_sack >= 4) {
+ this_sack--;
+ tp->rx_opt.num_sacks--;
+ sp--;
+ }
+ for(; this_sack > 0; this_sack--, sp--)
+ *sp = *(sp-1);
+
+new_sack:
+ /* Build the new head SACK, and we're done. */
+ sp->start_seq = seq;
+ sp->end_seq = end_seq;
+ tp->rx_opt.num_sacks++;
+ tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok);
+}
+
+/* RCV.NXT advances, some SACKs should be eaten. */
+
+static void tcp_sack_remove(struct tcp_sock *tp)
+{
+ struct tcp_sack_block *sp = &tp->selective_acks[0];
+ int num_sacks = tp->rx_opt.num_sacks;
+ int this_sack;
+
+ /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
+ if (skb_queue_len(&tp->out_of_order_queue) == 0) {
+ tp->rx_opt.num_sacks = 0;
+ tp->rx_opt.eff_sacks = tp->rx_opt.dsack;
+ return;
+ }
+
+ for(this_sack = 0; this_sack < num_sacks; ) {
+ /* Check if the start of the sack is covered by RCV.NXT. */
+ if (!before(tp->rcv_nxt, sp->start_seq)) {
+ int i;
+
+ /* RCV.NXT must cover all the block! */
+ BUG_TRAP(!before(tp->rcv_nxt, sp->end_seq));
+
+ /* Zap this SACK, by moving forward any other SACKS. */
+ for (i=this_sack+1; i < num_sacks; i++)
+ tp->selective_acks[i-1] = tp->selective_acks[i];
+ num_sacks--;
+ continue;
+ }
+ this_sack++;
+ sp++;
+ }
+ if (num_sacks != tp->rx_opt.num_sacks) {
+ tp->rx_opt.num_sacks = num_sacks;
+ tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok);
+ }
+}
+
+/* This one checks to see if we can put data from the
+ * out_of_order queue into the receive_queue.
+ */
+static void tcp_ofo_queue(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ __u32 dsack_high = tp->rcv_nxt;
+ struct sk_buff *skb;
+
+ while ((skb = skb_peek(&tp->out_of_order_queue)) != NULL) {
+ if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
+ break;
+
+ if (before(TCP_SKB_CB(skb)->seq, dsack_high)) {
+ __u32 dsack = dsack_high;
+ if (before(TCP_SKB_CB(skb)->end_seq, dsack_high))
+ dsack_high = TCP_SKB_CB(skb)->end_seq;
+ tcp_dsack_extend(tp, TCP_SKB_CB(skb)->seq, dsack);
+ }
+
+ if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
+ SOCK_DEBUG(sk, "ofo packet was already received \n");
+ __skb_unlink(skb, skb->list);
+ __kfree_skb(skb);
+ continue;
+ }
+ SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n",
+ tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
+ TCP_SKB_CB(skb)->end_seq);
+
+ __skb_unlink(skb, skb->list);
+ __skb_queue_tail(&sk->sk_receive_queue, skb);
+ tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
+ if(skb->h.th->fin)
+ tcp_fin(skb, sk, skb->h.th);
+ }
+}
+
+static int tcp_prune_queue(struct sock *sk);
+
+static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
+{
+ struct tcphdr *th = skb->h.th;
+ struct tcp_sock *tp = tcp_sk(sk);
+ int eaten = -1;
+
+ if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq)
+ goto drop;
+
+ th = skb->h.th;
+ __skb_pull(skb, th->doff*4);
+
+ TCP_ECN_accept_cwr(tp, skb);
+
+ if (tp->rx_opt.dsack) {
+ tp->rx_opt.dsack = 0;
+ tp->rx_opt.eff_sacks = min_t(unsigned int, tp->rx_opt.num_sacks,
+ 4 - tp->rx_opt.tstamp_ok);
+ }
+
+ /* Queue data for delivery to the user.
+ * Packets in sequence go to the receive queue.
+ * Out of sequence packets to the out_of_order_queue.
+ */
+ if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
+ if (tcp_receive_window(tp) == 0)
+ goto out_of_window;
+
+ /* Ok. In sequence. In window. */
+ if (tp->ucopy.task == current &&
+ tp->copied_seq == tp->rcv_nxt && tp->ucopy.len &&
+ sock_owned_by_user(sk) && !tp->urg_data) {
+ int chunk = min_t(unsigned int, skb->len,
+ tp->ucopy.len);
+
+ __set_current_state(TASK_RUNNING);
+
+ local_bh_enable();
+ if (!skb_copy_datagram_iovec(skb, 0, tp->ucopy.iov, chunk)) {
+ tp->ucopy.len -= chunk;
+ tp->copied_seq += chunk;
+ eaten = (chunk == skb->len && !th->fin);
+ tcp_rcv_space_adjust(sk);
+ }
+ local_bh_disable();
+ }
+
+ if (eaten <= 0) {
+queue_and_out:
+ if (eaten < 0 &&
+ (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
+ !sk_stream_rmem_schedule(sk, skb))) {
+ if (tcp_prune_queue(sk) < 0 ||
+ !sk_stream_rmem_schedule(sk, skb))
+ goto drop;
+ }
+ sk_stream_set_owner_r(skb, sk);
+ __skb_queue_tail(&sk->sk_receive_queue, skb);
+ }
+ tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
+ if(skb->len)
+ tcp_event_data_recv(sk, tp, skb);
+ if(th->fin)
+ tcp_fin(skb, sk, th);
+
+ if (skb_queue_len(&tp->out_of_order_queue)) {
+ tcp_ofo_queue(sk);
+
+ /* RFC2581. 4.2. SHOULD send immediate ACK, when
+ * gap in queue is filled.
+ */
+ if (!skb_queue_len(&tp->out_of_order_queue))
+ tp->ack.pingpong = 0;
+ }
+
+ if (tp->rx_opt.num_sacks)
+ tcp_sack_remove(tp);
+
+ tcp_fast_path_check(sk, tp);
+
+ if (eaten > 0)
+ __kfree_skb(skb);
+ else if (!sock_flag(sk, SOCK_DEAD))
+ sk->sk_data_ready(sk, 0);
+ return;
+ }
+
+ if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
+ /* A retransmit, 2nd most common case. Force an immediate ack. */
+ NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST);
+ tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
+
+out_of_window:
+ tcp_enter_quickack_mode(tp);
+ tcp_schedule_ack(tp);
+drop:
+ __kfree_skb(skb);
+ return;
+ }
+
+ /* Out of window. F.e. zero window probe. */
+ if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp)))
+ goto out_of_window;
+
+ tcp_enter_quickack_mode(tp);
+
+ if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
+ /* Partial packet, seq < rcv_next < end_seq */
+ SOCK_DEBUG(sk, "partial packet: rcv_next %X seq %X - %X\n",
+ tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
+ TCP_SKB_CB(skb)->end_seq);
+
+ tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, tp->rcv_nxt);
+
+ /* If window is closed, drop tail of packet. But after
+ * remembering D-SACK for its head made in previous line.
+ */
+ if (!tcp_receive_window(tp))
+ goto out_of_window;
+ goto queue_and_out;
+ }
+
+ TCP_ECN_check_ce(tp, skb);
+
+ if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
+ !sk_stream_rmem_schedule(sk, skb)) {
+ if (tcp_prune_queue(sk) < 0 ||
+ !sk_stream_rmem_schedule(sk, skb))
+ goto drop;
+ }
+
+ /* Disable header prediction. */
+ tp->pred_flags = 0;
+ tcp_schedule_ack(tp);
+
+ SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n",
+ tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
+
+ sk_stream_set_owner_r(skb, sk);
+
+ if (!skb_peek(&tp->out_of_order_queue)) {
+ /* Initial out of order segment, build 1 SACK. */
+ if (tp->rx_opt.sack_ok) {
+ tp->rx_opt.num_sacks = 1;
+ tp->rx_opt.dsack = 0;
+ tp->rx_opt.eff_sacks = 1;
+ tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq;
+ tp->selective_acks[0].end_seq =
+ TCP_SKB_CB(skb)->end_seq;
+ }
+ __skb_queue_head(&tp->out_of_order_queue,skb);
+ } else {
+ struct sk_buff *skb1 = tp->out_of_order_queue.prev;
+ u32 seq = TCP_SKB_CB(skb)->seq;
+ u32 end_seq = TCP_SKB_CB(skb)->end_seq;
+
+ if (seq == TCP_SKB_CB(skb1)->end_seq) {
+ __skb_append(skb1, skb);
+
+ if (!tp->rx_opt.num_sacks ||
+ tp->selective_acks[0].end_seq != seq)
+ goto add_sack;
+
+ /* Common case: data arrive in order after hole. */
+ tp->selective_acks[0].end_seq = end_seq;
+ return;
+ }
+
+ /* Find place to insert this segment. */
+ do {
+ if (!after(TCP_SKB_CB(skb1)->seq, seq))
+ break;
+ } while ((skb1 = skb1->prev) !=
+ (struct sk_buff*)&tp->out_of_order_queue);
+
+ /* Do skb overlap to previous one? */
+ if (skb1 != (struct sk_buff*)&tp->out_of_order_queue &&
+ before(seq, TCP_SKB_CB(skb1)->end_seq)) {
+ if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
+ /* All the bits are present. Drop. */
+ __kfree_skb(skb);
+ tcp_dsack_set(tp, seq, end_seq);
+ goto add_sack;
+ }
+ if (after(seq, TCP_SKB_CB(skb1)->seq)) {
+ /* Partial overlap. */
+ tcp_dsack_set(tp, seq, TCP_SKB_CB(skb1)->end_seq);
+ } else {
+ skb1 = skb1->prev;
+ }
+ }
+ __skb_insert(skb, skb1, skb1->next, &tp->out_of_order_queue);
+
+ /* And clean segments covered by new one as whole. */
+ while ((skb1 = skb->next) !=
+ (struct sk_buff*)&tp->out_of_order_queue &&
+ after(end_seq, TCP_SKB_CB(skb1)->seq)) {
+ if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
+ tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, end_seq);
+ break;
+ }
+ __skb_unlink(skb1, skb1->list);
+ tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, TCP_SKB_CB(skb1)->end_seq);
+ __kfree_skb(skb1);
+ }
+
+add_sack:
+ if (tp->rx_opt.sack_ok)
+ tcp_sack_new_ofo_skb(sk, seq, end_seq);
+ }
+}
+
+/* Collapse contiguous sequence of skbs head..tail with
+ * sequence numbers start..end.
+ * Segments with FIN/SYN are not collapsed (only because this
+ * simplifies code)
+ */
+static void
+tcp_collapse(struct sock *sk, struct sk_buff *head,
+ struct sk_buff *tail, u32 start, u32 end)
+{
+ struct sk_buff *skb;
+
+ /* First, check that queue is collapsable and find
+ * the point where collapsing can be useful. */
+ for (skb = head; skb != tail; ) {
+ /* No new bits? It is possible on ofo queue. */
+ if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
+ struct sk_buff *next = skb->next;
+ __skb_unlink(skb, skb->list);
+ __kfree_skb(skb);
+ NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED);
+ skb = next;
+ continue;
+ }
+
+ /* The first skb to collapse is:
+ * - not SYN/FIN and
+ * - bloated or contains data before "start" or
+ * overlaps to the next one.
+ */
+ if (!skb->h.th->syn && !skb->h.th->fin &&
+ (tcp_win_from_space(skb->truesize) > skb->len ||
+ before(TCP_SKB_CB(skb)->seq, start) ||
+ (skb->next != tail &&
+ TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb->next)->seq)))
+ break;
+
+ /* Decided to skip this, advance start seq. */
+ start = TCP_SKB_CB(skb)->end_seq;
+ skb = skb->next;
+ }
+ if (skb == tail || skb->h.th->syn || skb->h.th->fin)
+ return;
+
+ while (before(start, end)) {
+ struct sk_buff *nskb;
+ int header = skb_headroom(skb);
+ int copy = SKB_MAX_ORDER(header, 0);
+
+ /* Too big header? This can happen with IPv6. */
+ if (copy < 0)
+ return;
+ if (end-start < copy)
+ copy = end-start;
+ nskb = alloc_skb(copy+header, GFP_ATOMIC);
+ if (!nskb)
+ return;
+ skb_reserve(nskb, header);
+ memcpy(nskb->head, skb->head, header);
+ nskb->nh.raw = nskb->head + (skb->nh.raw-skb->head);
+ nskb->h.raw = nskb->head + (skb->h.raw-skb->head);
+ nskb->mac.raw = nskb->head + (skb->mac.raw-skb->head);
+ memcpy(nskb->cb, skb->cb, sizeof(skb->cb));
+ TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start;
+ __skb_insert(nskb, skb->prev, skb, skb->list);
+ sk_stream_set_owner_r(nskb, sk);
+
+ /* Copy data, releasing collapsed skbs. */
+ while (copy > 0) {
+ int offset = start - TCP_SKB_CB(skb)->seq;
+ int size = TCP_SKB_CB(skb)->end_seq - start;
+
+ if (offset < 0) BUG();
+ if (size > 0) {
+ size = min(copy, size);
+ if (skb_copy_bits(skb, offset, skb_put(nskb, size), size))
+ BUG();
+ TCP_SKB_CB(nskb)->end_seq += size;
+ copy -= size;
+ start += size;
+ }
+ if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
+ struct sk_buff *next = skb->next;
+ __skb_unlink(skb, skb->list);
+ __kfree_skb(skb);
+ NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED);
+ skb = next;
+ if (skb == tail || skb->h.th->syn || skb->h.th->fin)
+ return;
+ }
+ }
+ }
+}
+
+/* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
+ * and tcp_collapse() them until all the queue is collapsed.
+ */
+static void tcp_collapse_ofo_queue(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct sk_buff *skb = skb_peek(&tp->out_of_order_queue);
+ struct sk_buff *head;
+ u32 start, end;
+
+ if (skb == NULL)
+ return;
+
+ start = TCP_SKB_CB(skb)->seq;
+ end = TCP_SKB_CB(skb)->end_seq;
+ head = skb;
+
+ for (;;) {
+ skb = skb->next;
+
+ /* Segment is terminated when we see gap or when
+ * we are at the end of all the queue. */
+ if (skb == (struct sk_buff *)&tp->out_of_order_queue ||
+ after(TCP_SKB_CB(skb)->seq, end) ||
+ before(TCP_SKB_CB(skb)->end_seq, start)) {
+ tcp_collapse(sk, head, skb, start, end);
+ head = skb;
+ if (skb == (struct sk_buff *)&tp->out_of_order_queue)
+ break;
+ /* Start new segment */
+ start = TCP_SKB_CB(skb)->seq;
+ end = TCP_SKB_CB(skb)->end_seq;
+ } else {
+ if (before(TCP_SKB_CB(skb)->seq, start))
+ start = TCP_SKB_CB(skb)->seq;
+ if (after(TCP_SKB_CB(skb)->end_seq, end))
+ end = TCP_SKB_CB(skb)->end_seq;
+ }
+ }
+}
+
+/* Reduce allocated memory if we can, trying to get
+ * the socket within its memory limits again.
+ *
+ * Return less than zero if we should start dropping frames
+ * until the socket owning process reads some of the data
+ * to stabilize the situation.
+ */
+static int tcp_prune_queue(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ SOCK_DEBUG(sk, "prune_queue: c=%x\n", tp->copied_seq);
+
+ NET_INC_STATS_BH(LINUX_MIB_PRUNECALLED);
+
+ if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf)
+ tcp_clamp_window(sk, tp);
+ else if (tcp_memory_pressure)
+ tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss);
+
+ tcp_collapse_ofo_queue(sk);
+ tcp_collapse(sk, sk->sk_receive_queue.next,
+ (struct sk_buff*)&sk->sk_receive_queue,
+ tp->copied_seq, tp->rcv_nxt);
+ sk_stream_mem_reclaim(sk);
+
+ if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
+ return 0;
+
+ /* Collapsing did not help, destructive actions follow.
+ * This must not ever occur. */
+
+ /* First, purge the out_of_order queue. */
+ if (skb_queue_len(&tp->out_of_order_queue)) {
+ NET_ADD_STATS_BH(LINUX_MIB_OFOPRUNED,
+ skb_queue_len(&tp->out_of_order_queue));
+ __skb_queue_purge(&tp->out_of_order_queue);
+
+ /* Reset SACK state. A conforming SACK implementation will
+ * do the same at a timeout based retransmit. When a connection
+ * is in a sad state like this, we care only about integrity
+ * of the connection not performance.
+ */
+ if (tp->rx_opt.sack_ok)
+ tcp_sack_reset(&tp->rx_opt);
+ sk_stream_mem_reclaim(sk);
+ }
+
+ if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
+ return 0;
+
+ /* If we are really being abused, tell the caller to silently
+ * drop receive data on the floor. It will get retransmitted
+ * and hopefully then we'll have sufficient space.
+ */
+ NET_INC_STATS_BH(LINUX_MIB_RCVPRUNED);
+
+ /* Massive buffer overcommit. */
+ tp->pred_flags = 0;
+ return -1;
+}
+
+
+/* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
+ * As additional protections, we do not touch cwnd in retransmission phases,
+ * and if application hit its sndbuf limit recently.
+ */
+void tcp_cwnd_application_limited(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ if (tp->ca_state == TCP_CA_Open &&
+ sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
+ /* Limited by application or receiver window. */
+ u32 win_used = max(tp->snd_cwnd_used, 2U);
+ if (win_used < tp->snd_cwnd) {
+ tp->snd_ssthresh = tcp_current_ssthresh(tp);
+ tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1;
+ }
+ tp->snd_cwnd_used = 0;
+ }
+ tp->snd_cwnd_stamp = tcp_time_stamp;
+}
+
+
+/* When incoming ACK allowed to free some skb from write_queue,
+ * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
+ * on the exit from tcp input handler.
+ *
+ * PROBLEM: sndbuf expansion does not work well with largesend.
+ */
+static void tcp_new_space(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ if (tp->packets_out < tp->snd_cwnd &&
+ !(sk->sk_userlocks & SOCK_SNDBUF_LOCK) &&
+ !tcp_memory_pressure &&
+ atomic_read(&tcp_memory_allocated) < sysctl_tcp_mem[0]) {
+ int sndmem = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache_std) +
+ MAX_TCP_HEADER + 16 + sizeof(struct sk_buff),
+ demanded = max_t(unsigned int, tp->snd_cwnd,
+ tp->reordering + 1);
+ sndmem *= 2*demanded;
+ if (sndmem > sk->sk_sndbuf)
+ sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]);
+ tp->snd_cwnd_stamp = tcp_time_stamp;
+ }
+
+ sk->sk_write_space(sk);
+}
+
+static inline void tcp_check_space(struct sock *sk)
+{
+ if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) {
+ sock_reset_flag(sk, SOCK_QUEUE_SHRUNK);
+ if (sk->sk_socket &&
+ test_bit(SOCK_NOSPACE, &sk->sk_socket->flags))
+ tcp_new_space(sk);
+ }
+}
+
+static void __tcp_data_snd_check(struct sock *sk, struct sk_buff *skb)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ if (after(TCP_SKB_CB(skb)->end_seq, tp->snd_una + tp->snd_wnd) ||
+ tcp_packets_in_flight(tp) >= tp->snd_cwnd ||
+ tcp_write_xmit(sk, tp->nonagle))
+ tcp_check_probe_timer(sk, tp);
+}
+
+static __inline__ void tcp_data_snd_check(struct sock *sk)
+{
+ struct sk_buff *skb = sk->sk_send_head;
+
+ if (skb != NULL)
+ __tcp_data_snd_check(sk, skb);
+ tcp_check_space(sk);
+}
+
+/*
+ * Check if sending an ack is needed.
+ */
+static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ /* More than one full frame received... */
+ if (((tp->rcv_nxt - tp->rcv_wup) > tp->ack.rcv_mss
+ /* ... and right edge of window advances far enough.
+ * (tcp_recvmsg() will send ACK otherwise). Or...
+ */
+ && __tcp_select_window(sk) >= tp->rcv_wnd) ||
+ /* We ACK each frame or... */
+ tcp_in_quickack_mode(tp) ||
+ /* We have out of order data. */
+ (ofo_possible &&
+ skb_peek(&tp->out_of_order_queue))) {
+ /* Then ack it now */
+ tcp_send_ack(sk);
+ } else {
+ /* Else, send delayed ack. */
+ tcp_send_delayed_ack(sk);
+ }
+}
+
+static __inline__ void tcp_ack_snd_check(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ if (!tcp_ack_scheduled(tp)) {
+ /* We sent a data segment already. */
+ return;
+ }
+ __tcp_ack_snd_check(sk, 1);
+}
+
+/*
+ * This routine is only called when we have urgent data
+ * signalled. Its the 'slow' part of tcp_urg. It could be
+ * moved inline now as tcp_urg is only called from one
+ * place. We handle URGent data wrong. We have to - as
+ * BSD still doesn't use the correction from RFC961.
+ * For 1003.1g we should support a new option TCP_STDURG to permit
+ * either form (or just set the sysctl tcp_stdurg).
+ */
+
+static void tcp_check_urg(struct sock * sk, struct tcphdr * th)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ u32 ptr = ntohs(th->urg_ptr);
+
+ if (ptr && !sysctl_tcp_stdurg)
+ ptr--;
+ ptr += ntohl(th->seq);
+
+ /* Ignore urgent data that we've already seen and read. */
+ if (after(tp->copied_seq, ptr))
+ return;
+
+ /* Do not replay urg ptr.
+ *
+ * NOTE: interesting situation not covered by specs.
+ * Misbehaving sender may send urg ptr, pointing to segment,
+ * which we already have in ofo queue. We are not able to fetch
+ * such data and will stay in TCP_URG_NOTYET until will be eaten
+ * by recvmsg(). Seems, we are not obliged to handle such wicked
+ * situations. But it is worth to think about possibility of some
+ * DoSes using some hypothetical application level deadlock.
+ */
+ if (before(ptr, tp->rcv_nxt))
+ return;
+
+ /* Do we already have a newer (or duplicate) urgent pointer? */
+ if (tp->urg_data && !after(ptr, tp->urg_seq))
+ return;
+
+ /* Tell the world about our new urgent pointer. */
+ sk_send_sigurg(sk);
+
+ /* We may be adding urgent data when the last byte read was
+ * urgent. To do this requires some care. We cannot just ignore
+ * tp->copied_seq since we would read the last urgent byte again
+ * as data, nor can we alter copied_seq until this data arrives
+ * or we break the sematics of SIOCATMARK (and thus sockatmark())
+ *
+ * NOTE. Double Dutch. Rendering to plain English: author of comment
+ * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
+ * and expect that both A and B disappear from stream. This is _wrong_.
+ * Though this happens in BSD with high probability, this is occasional.
+ * Any application relying on this is buggy. Note also, that fix "works"
+ * only in this artificial test. Insert some normal data between A and B and we will
+ * decline of BSD again. Verdict: it is better to remove to trap
+ * buggy users.
+ */
+ if (tp->urg_seq == tp->copied_seq && tp->urg_data &&
+ !sock_flag(sk, SOCK_URGINLINE) &&
+ tp->copied_seq != tp->rcv_nxt) {
+ struct sk_buff *skb = skb_peek(&sk->sk_receive_queue);
+ tp->copied_seq++;
+ if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) {
+ __skb_unlink(skb, skb->list);
+ __kfree_skb(skb);
+ }
+ }
+
+ tp->urg_data = TCP_URG_NOTYET;
+ tp->urg_seq = ptr;
+
+ /* Disable header prediction. */
+ tp->pred_flags = 0;
+}
+
+/* This is the 'fast' part of urgent handling. */
+static void tcp_urg(struct sock *sk, struct sk_buff *skb, struct tcphdr *th)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ /* Check if we get a new urgent pointer - normally not. */
+ if (th->urg)
+ tcp_check_urg(sk,th);
+
+ /* Do we wait for any urgent data? - normally not... */
+ if (tp->urg_data == TCP_URG_NOTYET) {
+ u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) -
+ th->syn;
+
+ /* Is the urgent pointer pointing into this packet? */
+ if (ptr < skb->len) {
+ u8 tmp;
+ if (skb_copy_bits(skb, ptr, &tmp, 1))
+ BUG();
+ tp->urg_data = TCP_URG_VALID | tmp;
+ if (!sock_flag(sk, SOCK_DEAD))
+ sk->sk_data_ready(sk, 0);
+ }
+ }
+}
+
+static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ int chunk = skb->len - hlen;
+ int err;
+
+ local_bh_enable();
+ if (skb->ip_summed==CHECKSUM_UNNECESSARY)
+ err = skb_copy_datagram_iovec(skb, hlen, tp->ucopy.iov, chunk);
+ else
+ err = skb_copy_and_csum_datagram_iovec(skb, hlen,
+ tp->ucopy.iov);
+
+ if (!err) {
+ tp->ucopy.len -= chunk;
+ tp->copied_seq += chunk;
+ tcp_rcv_space_adjust(sk);
+ }
+
+ local_bh_disable();
+ return err;
+}
+
+static int __tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb)
+{
+ int result;
+
+ if (sock_owned_by_user(sk)) {
+ local_bh_enable();
+ result = __tcp_checksum_complete(skb);
+ local_bh_disable();
+ } else {
+ result = __tcp_checksum_complete(skb);
+ }
+ return result;
+}
+
+static __inline__ int
+tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb)
+{
+ return skb->ip_summed != CHECKSUM_UNNECESSARY &&
+ __tcp_checksum_complete_user(sk, skb);
+}
+
+/*
+ * TCP receive function for the ESTABLISHED state.
+ *
+ * It is split into a fast path and a slow path. The fast path is
+ * disabled when:
+ * - A zero window was announced from us - zero window probing
+ * is only handled properly in the slow path.
+ * - Out of order segments arrived.
+ * - Urgent data is expected.
+ * - There is no buffer space left
+ * - Unexpected TCP flags/window values/header lengths are received
+ * (detected by checking the TCP header against pred_flags)
+ * - Data is sent in both directions. Fast path only supports pure senders
+ * or pure receivers (this means either the sequence number or the ack
+ * value must stay constant)
+ * - Unexpected TCP option.
+ *
+ * When these conditions are not satisfied it drops into a standard
+ * receive procedure patterned after RFC793 to handle all cases.
+ * The first three cases are guaranteed by proper pred_flags setting,
+ * the rest is checked inline. Fast processing is turned on in
+ * tcp_data_queue when everything is OK.
+ */
+int tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
+ struct tcphdr *th, unsigned len)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ /*
+ * Header prediction.
+ * The code loosely follows the one in the famous
+ * "30 instruction TCP receive" Van Jacobson mail.
+ *
+ * Van's trick is to deposit buffers into socket queue
+ * on a device interrupt, to call tcp_recv function
+ * on the receive process context and checksum and copy
+ * the buffer to user space. smart...
+ *
+ * Our current scheme is not silly either but we take the
+ * extra cost of the net_bh soft interrupt processing...
+ * We do checksum and copy also but from device to kernel.
+ */
+
+ tp->rx_opt.saw_tstamp = 0;
+
+ /* pred_flags is 0xS?10 << 16 + snd_wnd
+ * if header_predition is to be made
+ * 'S' will always be tp->tcp_header_len >> 2
+ * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
+ * turn it off (when there are holes in the receive
+ * space for instance)
+ * PSH flag is ignored.
+ */
+
+ if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags &&
+ TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
+ int tcp_header_len = tp->tcp_header_len;
+
+ /* Timestamp header prediction: tcp_header_len
+ * is automatically equal to th->doff*4 due to pred_flags
+ * match.
+ */
+
+ /* Check timestamp */
+ if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) {
+ __u32 *ptr = (__u32 *)(th + 1);
+
+ /* No? Slow path! */
+ if (*ptr != ntohl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
+ | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP))
+ goto slow_path;
+
+ tp->rx_opt.saw_tstamp = 1;
+ ++ptr;
+ tp->rx_opt.rcv_tsval = ntohl(*ptr);
+ ++ptr;
+ tp->rx_opt.rcv_tsecr = ntohl(*ptr);
+
+ /* If PAWS failed, check it more carefully in slow path */
+ if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0)
+ goto slow_path;
+
+ /* DO NOT update ts_recent here, if checksum fails
+ * and timestamp was corrupted part, it will result
+ * in a hung connection since we will drop all
+ * future packets due to the PAWS test.
+ */
+ }
+
+ if (len <= tcp_header_len) {
+ /* Bulk data transfer: sender */
+ if (len == tcp_header_len) {
+ /* Predicted packet is in window by definition.
+ * seq == rcv_nxt and rcv_wup <= rcv_nxt.
+ * Hence, check seq<=rcv_wup reduces to:
+ */
+ if (tcp_header_len ==
+ (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
+ tp->rcv_nxt == tp->rcv_wup)
+ tcp_store_ts_recent(tp);
+
+ tcp_rcv_rtt_measure_ts(tp, skb);
+
+ /* We know that such packets are checksummed
+ * on entry.
+ */
+ tcp_ack(sk, skb, 0);
+ __kfree_skb(skb);
+ tcp_data_snd_check(sk);
+ return 0;
+ } else { /* Header too small */
+ TCP_INC_STATS_BH(TCP_MIB_INERRS);
+ goto discard;
+ }
+ } else {
+ int eaten = 0;
+
+ if (tp->ucopy.task == current &&
+ tp->copied_seq == tp->rcv_nxt &&
+ len - tcp_header_len <= tp->ucopy.len &&
+ sock_owned_by_user(sk)) {
+ __set_current_state(TASK_RUNNING);
+
+ if (!tcp_copy_to_iovec(sk, skb, tcp_header_len)) {
+ /* Predicted packet is in window by definition.
+ * seq == rcv_nxt and rcv_wup <= rcv_nxt.
+ * Hence, check seq<=rcv_wup reduces to:
+ */
+ if (tcp_header_len ==
+ (sizeof(struct tcphdr) +
+ TCPOLEN_TSTAMP_ALIGNED) &&
+ tp->rcv_nxt == tp->rcv_wup)
+ tcp_store_ts_recent(tp);
+
+ tcp_rcv_rtt_measure_ts(tp, skb);
+
+ __skb_pull(skb, tcp_header_len);
+ tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
+ NET_INC_STATS_BH(LINUX_MIB_TCPHPHITSTOUSER);
+ eaten = 1;
+ }
+ }
+ if (!eaten) {
+ if (tcp_checksum_complete_user(sk, skb))
+ goto csum_error;
+
+ /* Predicted packet is in window by definition.
+ * seq == rcv_nxt and rcv_wup <= rcv_nxt.
+ * Hence, check seq<=rcv_wup reduces to:
+ */
+ if (tcp_header_len ==
+ (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
+ tp->rcv_nxt == tp->rcv_wup)
+ tcp_store_ts_recent(tp);
+
+ tcp_rcv_rtt_measure_ts(tp, skb);
+
+ if ((int)skb->truesize > sk->sk_forward_alloc)
+ goto step5;
+
+ NET_INC_STATS_BH(LINUX_MIB_TCPHPHITS);
+
+ /* Bulk data transfer: receiver */
+ __skb_pull(skb,tcp_header_len);
+ __skb_queue_tail(&sk->sk_receive_queue, skb);
+ sk_stream_set_owner_r(skb, sk);
+ tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
+ }
+
+ tcp_event_data_recv(sk, tp, skb);
+
+ if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) {
+ /* Well, only one small jumplet in fast path... */
+ tcp_ack(sk, skb, FLAG_DATA);
+ tcp_data_snd_check(sk);
+ if (!tcp_ack_scheduled(tp))
+ goto no_ack;
+ }
+
+ if (eaten) {
+ if (tcp_in_quickack_mode(tp)) {
+ tcp_send_ack(sk);
+ } else {
+ tcp_send_delayed_ack(sk);
+ }
+ } else {
+ __tcp_ack_snd_check(sk, 0);
+ }
+
+no_ack:
+ if (eaten)
+ __kfree_skb(skb);
+ else
+ sk->sk_data_ready(sk, 0);
+ return 0;
+ }
+ }
+
+slow_path:
+ if (len < (th->doff<<2) || tcp_checksum_complete_user(sk, skb))
+ goto csum_error;
+
+ /*
+ * RFC1323: H1. Apply PAWS check first.
+ */
+ if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
+ tcp_paws_discard(tp, skb)) {
+ if (!th->rst) {
+ NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
+ tcp_send_dupack(sk, skb);
+ goto discard;
+ }
+ /* Resets are accepted even if PAWS failed.
+
+ ts_recent update must be made after we are sure
+ that the packet is in window.
+ */
+ }
+
+ /*
+ * Standard slow path.
+ */
+
+ if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
+ /* RFC793, page 37: "In all states except SYN-SENT, all reset
+ * (RST) segments are validated by checking their SEQ-fields."
+ * And page 69: "If an incoming segment is not acceptable,
+ * an acknowledgment should be sent in reply (unless the RST bit
+ * is set, if so drop the segment and return)".
+ */
+ if (!th->rst)
+ tcp_send_dupack(sk, skb);
+ goto discard;
+ }
+
+ if(th->rst) {
+ tcp_reset(sk);
+ goto discard;
+ }
+
+ tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
+
+ if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
+ TCP_INC_STATS_BH(TCP_MIB_INERRS);
+ NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN);
+ tcp_reset(sk);
+ return 1;
+ }
+
+step5:
+ if(th->ack)
+ tcp_ack(sk, skb, FLAG_SLOWPATH);
+
+ tcp_rcv_rtt_measure_ts(tp, skb);
+
+ /* Process urgent data. */
+ tcp_urg(sk, skb, th);
+
+ /* step 7: process the segment text */
+ tcp_data_queue(sk, skb);
+
+ tcp_data_snd_check(sk);
+ tcp_ack_snd_check(sk);
+ return 0;
+
+csum_error:
+ TCP_INC_STATS_BH(TCP_MIB_INERRS);
+
+discard:
+ __kfree_skb(skb);
+ return 0;
+}
+
+static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
+ struct tcphdr *th, unsigned len)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ int saved_clamp = tp->rx_opt.mss_clamp;
+
+ tcp_parse_options(skb, &tp->rx_opt, 0);
+
+ if (th->ack) {
+ /* rfc793:
+ * "If the state is SYN-SENT then
+ * first check the ACK bit
+ * If the ACK bit is set
+ * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
+ * a reset (unless the RST bit is set, if so drop
+ * the segment and return)"
+ *
+ * We do not send data with SYN, so that RFC-correct
+ * test reduces to:
+ */
+ if (TCP_SKB_CB(skb)->ack_seq != tp->snd_nxt)
+ goto reset_and_undo;
+
+ if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
+ !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp,
+ tcp_time_stamp)) {
+ NET_INC_STATS_BH(LINUX_MIB_PAWSACTIVEREJECTED);
+ goto reset_and_undo;
+ }
+
+ /* Now ACK is acceptable.
+ *
+ * "If the RST bit is set
+ * If the ACK was acceptable then signal the user "error:
+ * connection reset", drop the segment, enter CLOSED state,
+ * delete TCB, and return."
+ */
+
+ if (th->rst) {
+ tcp_reset(sk);
+ goto discard;
+ }
+
+ /* rfc793:
+ * "fifth, if neither of the SYN or RST bits is set then
+ * drop the segment and return."
+ *
+ * See note below!
+ * --ANK(990513)
+ */
+ if (!th->syn)
+ goto discard_and_undo;
+
+ /* rfc793:
+ * "If the SYN bit is on ...
+ * are acceptable then ...
+ * (our SYN has been ACKed), change the connection
+ * state to ESTABLISHED..."
+ */
+
+ TCP_ECN_rcv_synack(tp, th);
+ if (tp->ecn_flags&TCP_ECN_OK)
+ sock_set_flag(sk, SOCK_NO_LARGESEND);
+
+ tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
+ tcp_ack(sk, skb, FLAG_SLOWPATH);
+
+ /* Ok.. it's good. Set up sequence numbers and
+ * move to established.
+ */
+ tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
+ tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
+
+ /* RFC1323: The window in SYN & SYN/ACK segments is
+ * never scaled.
+ */
+ tp->snd_wnd = ntohs(th->window);
+ tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq, TCP_SKB_CB(skb)->seq);
+
+ if (!tp->rx_opt.wscale_ok) {
+ tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0;
+ tp->window_clamp = min(tp->window_clamp, 65535U);
+ }
+
+ if (tp->rx_opt.saw_tstamp) {
+ tp->rx_opt.tstamp_ok = 1;
+ tp->tcp_header_len =
+ sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
+ tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
+ tcp_store_ts_recent(tp);
+ } else {
+ tp->tcp_header_len = sizeof(struct tcphdr);
+ }
+
+ if (tp->rx_opt.sack_ok && sysctl_tcp_fack)
+ tp->rx_opt.sack_ok |= 2;
+
+ tcp_sync_mss(sk, tp->pmtu_cookie);
+ tcp_initialize_rcv_mss(sk);
+
+ /* Remember, tcp_poll() does not lock socket!
+ * Change state from SYN-SENT only after copied_seq
+ * is initialized. */
+ tp->copied_seq = tp->rcv_nxt;
+ mb();
+ tcp_set_state(sk, TCP_ESTABLISHED);
+
+ /* Make sure socket is routed, for correct metrics. */
+ tp->af_specific->rebuild_header(sk);
+
+ tcp_init_metrics(sk);
+
+ /* Prevent spurious tcp_cwnd_restart() on first data
+ * packet.
+ */
+ tp->lsndtime = tcp_time_stamp;
+
+ tcp_init_buffer_space(sk);
+
+ if (sock_flag(sk, SOCK_KEEPOPEN))
+ tcp_reset_keepalive_timer(sk, keepalive_time_when(tp));
+
+ if (!tp->rx_opt.snd_wscale)
+ __tcp_fast_path_on(tp, tp->snd_wnd);
+ else
+ tp->pred_flags = 0;
+
+ if (!sock_flag(sk, SOCK_DEAD)) {
+ sk->sk_state_change(sk);
+ sk_wake_async(sk, 0, POLL_OUT);
+ }
+
+ if (sk->sk_write_pending || tp->defer_accept || tp->ack.pingpong) {
+ /* Save one ACK. Data will be ready after
+ * several ticks, if write_pending is set.
+ *
+ * It may be deleted, but with this feature tcpdumps
+ * look so _wonderfully_ clever, that I was not able
+ * to stand against the temptation 8) --ANK
+ */
+ tcp_schedule_ack(tp);
+ tp->ack.lrcvtime = tcp_time_stamp;
+ tp->ack.ato = TCP_ATO_MIN;
+ tcp_incr_quickack(tp);
+ tcp_enter_quickack_mode(tp);
+ tcp_reset_xmit_timer(sk, TCP_TIME_DACK, TCP_DELACK_MAX);
+
+discard:
+ __kfree_skb(skb);
+ return 0;
+ } else {
+ tcp_send_ack(sk);
+ }
+ return -1;
+ }
+
+ /* No ACK in the segment */
+
+ if (th->rst) {
+ /* rfc793:
+ * "If the RST bit is set
+ *
+ * Otherwise (no ACK) drop the segment and return."
+ */
+
+ goto discard_and_undo;
+ }
+
+ /* PAWS check. */
+ if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp && tcp_paws_check(&tp->rx_opt, 0))
+ goto discard_and_undo;
+
+ if (th->syn) {
+ /* We see SYN without ACK. It is attempt of
+ * simultaneous connect with crossed SYNs.
+ * Particularly, it can be connect to self.
+ */
+ tcp_set_state(sk, TCP_SYN_RECV);
+
+ if (tp->rx_opt.saw_tstamp) {
+ tp->rx_opt.tstamp_ok = 1;
+ tcp_store_ts_recent(tp);
+ tp->tcp_header_len =
+ sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
+ } else {
+ tp->tcp_header_len = sizeof(struct tcphdr);
+ }
+
+ tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
+ tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
+
+ /* RFC1323: The window in SYN & SYN/ACK segments is
+ * never scaled.
+ */
+ tp->snd_wnd = ntohs(th->window);
+ tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
+ tp->max_window = tp->snd_wnd;
+
+ TCP_ECN_rcv_syn(tp, th);
+ if (tp->ecn_flags&TCP_ECN_OK)
+ sock_set_flag(sk, SOCK_NO_LARGESEND);
+
+ tcp_sync_mss(sk, tp->pmtu_cookie);
+ tcp_initialize_rcv_mss(sk);
+
+
+ tcp_send_synack(sk);
+#if 0
+ /* Note, we could accept data and URG from this segment.
+ * There are no obstacles to make this.
+ *
+ * However, if we ignore data in ACKless segments sometimes,
+ * we have no reasons to accept it sometimes.
+ * Also, seems the code doing it in step6 of tcp_rcv_state_process
+ * is not flawless. So, discard packet for sanity.
+ * Uncomment this return to process the data.
+ */
+ return -1;
+#else
+ goto discard;
+#endif
+ }
+ /* "fifth, if neither of the SYN or RST bits is set then
+ * drop the segment and return."
+ */
+
+discard_and_undo:
+ tcp_clear_options(&tp->rx_opt);
+ tp->rx_opt.mss_clamp = saved_clamp;
+ goto discard;
+
+reset_and_undo:
+ tcp_clear_options(&tp->rx_opt);
+ tp->rx_opt.mss_clamp = saved_clamp;
+ return 1;
+}
+
+
+/*
+ * This function implements the receiving procedure of RFC 793 for
+ * all states except ESTABLISHED and TIME_WAIT.
+ * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
+ * address independent.
+ */
+
+int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
+ struct tcphdr *th, unsigned len)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ int queued = 0;
+
+ tp->rx_opt.saw_tstamp = 0;
+
+ switch (sk->sk_state) {
+ case TCP_CLOSE:
+ goto discard;
+
+ case TCP_LISTEN:
+ if(th->ack)
+ return 1;
+
+ if(th->rst)
+ goto discard;
+
+ if(th->syn) {
+ if(tp->af_specific->conn_request(sk, skb) < 0)
+ return 1;
+
+ init_westwood(sk);
+ init_bictcp(tp);
+
+ /* Now we have several options: In theory there is
+ * nothing else in the frame. KA9Q has an option to
+ * send data with the syn, BSD accepts data with the
+ * syn up to the [to be] advertised window and
+ * Solaris 2.1 gives you a protocol error. For now
+ * we just ignore it, that fits the spec precisely
+ * and avoids incompatibilities. It would be nice in
+ * future to drop through and process the data.
+ *
+ * Now that TTCP is starting to be used we ought to
+ * queue this data.
+ * But, this leaves one open to an easy denial of
+ * service attack, and SYN cookies can't defend
+ * against this problem. So, we drop the data
+ * in the interest of security over speed.
+ */
+ goto discard;
+ }
+ goto discard;
+
+ case TCP_SYN_SENT:
+ init_westwood(sk);
+ init_bictcp(tp);
+
+ queued = tcp_rcv_synsent_state_process(sk, skb, th, len);
+ if (queued >= 0)
+ return queued;
+
+ /* Do step6 onward by hand. */
+ tcp_urg(sk, skb, th);
+ __kfree_skb(skb);
+ tcp_data_snd_check(sk);
+ return 0;
+ }
+
+ if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
+ tcp_paws_discard(tp, skb)) {
+ if (!th->rst) {
+ NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
+ tcp_send_dupack(sk, skb);
+ goto discard;
+ }
+ /* Reset is accepted even if it did not pass PAWS. */
+ }
+
+ /* step 1: check sequence number */
+ if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
+ if (!th->rst)
+ tcp_send_dupack(sk, skb);
+ goto discard;
+ }
+
+ /* step 2: check RST bit */
+ if(th->rst) {
+ tcp_reset(sk);
+ goto discard;
+ }
+
+ tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
+
+ /* step 3: check security and precedence [ignored] */
+
+ /* step 4:
+ *
+ * Check for a SYN in window.
+ */
+ if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
+ NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN);
+ tcp_reset(sk);
+ return 1;
+ }
+
+ /* step 5: check the ACK field */
+ if (th->ack) {
+ int acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH);
+
+ switch(sk->sk_state) {
+ case TCP_SYN_RECV:
+ if (acceptable) {
+ tp->copied_seq = tp->rcv_nxt;
+ mb();
+ tcp_set_state(sk, TCP_ESTABLISHED);
+ sk->sk_state_change(sk);
+
+ /* Note, that this wakeup is only for marginal
+ * crossed SYN case. Passively open sockets
+ * are not waked up, because sk->sk_sleep ==
+ * NULL and sk->sk_socket == NULL.
+ */
+ if (sk->sk_socket) {
+ sk_wake_async(sk,0,POLL_OUT);
+ }
+
+ tp->snd_una = TCP_SKB_CB(skb)->ack_seq;
+ tp->snd_wnd = ntohs(th->window) <<
+ tp->rx_opt.snd_wscale;
+ tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq,
+ TCP_SKB_CB(skb)->seq);
+
+ /* tcp_ack considers this ACK as duplicate
+ * and does not calculate rtt.
+ * Fix it at least with timestamps.
+ */
+ if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
+ !tp->srtt)
+ tcp_ack_saw_tstamp(tp, 0);
+
+ if (tp->rx_opt.tstamp_ok)
+ tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
+
+ /* Make sure socket is routed, for
+ * correct metrics.
+ */
+ tp->af_specific->rebuild_header(sk);
+
+ tcp_init_metrics(sk);
+
+ /* Prevent spurious tcp_cwnd_restart() on
+ * first data packet.
+ */
+ tp->lsndtime = tcp_time_stamp;
+
+ tcp_initialize_rcv_mss(sk);
+ tcp_init_buffer_space(sk);
+ tcp_fast_path_on(tp);
+ } else {
+ return 1;
+ }
+ break;
+
+ case TCP_FIN_WAIT1:
+ if (tp->snd_una == tp->write_seq) {
+ tcp_set_state(sk, TCP_FIN_WAIT2);
+ sk->sk_shutdown |= SEND_SHUTDOWN;
+ dst_confirm(sk->sk_dst_cache);
+
+ if (!sock_flag(sk, SOCK_DEAD))
+ /* Wake up lingering close() */
+ sk->sk_state_change(sk);
+ else {
+ int tmo;
+
+ if (tp->linger2 < 0 ||
+ (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
+ after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt))) {
+ tcp_done(sk);
+ NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA);
+ return 1;
+ }
+
+ tmo = tcp_fin_time(tp);
+ if (tmo > TCP_TIMEWAIT_LEN) {
+ tcp_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN);
+ } else if (th->fin || sock_owned_by_user(sk)) {
+ /* Bad case. We could lose such FIN otherwise.
+ * It is not a big problem, but it looks confusing
+ * and not so rare event. We still can lose it now,
+ * if it spins in bh_lock_sock(), but it is really
+ * marginal case.
+ */
+ tcp_reset_keepalive_timer(sk, tmo);
+ } else {
+ tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
+ goto discard;
+ }
+ }
+ }
+ break;
+
+ case TCP_CLOSING:
+ if (tp->snd_una == tp->write_seq) {
+ tcp_time_wait(sk, TCP_TIME_WAIT, 0);
+ goto discard;
+ }
+ break;
+
+ case TCP_LAST_ACK:
+ if (tp->snd_una == tp->write_seq) {
+ tcp_update_metrics(sk);
+ tcp_done(sk);
+ goto discard;
+ }
+ break;
+ }
+ } else
+ goto discard;
+
+ /* step 6: check the URG bit */
+ tcp_urg(sk, skb, th);
+
+ /* step 7: process the segment text */
+ switch (sk->sk_state) {
+ case TCP_CLOSE_WAIT:
+ case TCP_CLOSING:
+ case TCP_LAST_ACK:
+ if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
+ break;
+ case TCP_FIN_WAIT1:
+ case TCP_FIN_WAIT2:
+ /* RFC 793 says to queue data in these states,
+ * RFC 1122 says we MUST send a reset.
+ * BSD 4.4 also does reset.
+ */
+ if (sk->sk_shutdown & RCV_SHUTDOWN) {
+ if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
+ after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) {
+ NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA);
+ tcp_reset(sk);
+ return 1;
+ }
+ }
+ /* Fall through */
+ case TCP_ESTABLISHED:
+ tcp_data_queue(sk, skb);
+ queued = 1;
+ break;
+ }
+
+ /* tcp_data could move socket to TIME-WAIT */
+ if (sk->sk_state != TCP_CLOSE) {
+ tcp_data_snd_check(sk);
+ tcp_ack_snd_check(sk);
+ }
+
+ if (!queued) {
+discard:
+ __kfree_skb(skb);
+ }
+ return 0;
+}
+
+EXPORT_SYMBOL(sysctl_tcp_ecn);
+EXPORT_SYMBOL(sysctl_tcp_reordering);
+EXPORT_SYMBOL(tcp_parse_options);
+EXPORT_SYMBOL(tcp_rcv_established);
+EXPORT_SYMBOL(tcp_rcv_state_process);
