| // SPDX-License-Identifier: GPL-2.0-only |
| /* (C) 1999-2001 Paul `Rusty' Russell |
| * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org> |
| * (C) 2002-2013 Jozsef Kadlecsik <kadlec@netfilter.org> |
| * (C) 2006-2012 Patrick McHardy <kaber@trash.net> |
| */ |
| |
| #include <linux/types.h> |
| #include <linux/timer.h> |
| #include <linux/module.h> |
| #include <linux/in.h> |
| #include <linux/tcp.h> |
| #include <linux/spinlock.h> |
| #include <linux/skbuff.h> |
| #include <linux/ipv6.h> |
| #include <net/ip6_checksum.h> |
| #include <asm/unaligned.h> |
| |
| #include <net/tcp.h> |
| |
| #include <linux/netfilter.h> |
| #include <linux/netfilter_ipv4.h> |
| #include <linux/netfilter_ipv6.h> |
| #include <net/netfilter/nf_conntrack.h> |
| #include <net/netfilter/nf_conntrack_l4proto.h> |
| #include <net/netfilter/nf_conntrack_ecache.h> |
| #include <net/netfilter/nf_conntrack_seqadj.h> |
| #include <net/netfilter/nf_conntrack_synproxy.h> |
| #include <net/netfilter/nf_conntrack_timeout.h> |
| #include <net/netfilter/nf_log.h> |
| #include <net/netfilter/ipv4/nf_conntrack_ipv4.h> |
| #include <net/netfilter/ipv6/nf_conntrack_ipv6.h> |
| |
| /* FIXME: Examine ipfilter's timeouts and conntrack transitions more |
| closely. They're more complex. --RR */ |
| |
| static const char *const tcp_conntrack_names[] = { |
| "NONE", |
| "SYN_SENT", |
| "SYN_RECV", |
| "ESTABLISHED", |
| "FIN_WAIT", |
| "CLOSE_WAIT", |
| "LAST_ACK", |
| "TIME_WAIT", |
| "CLOSE", |
| "SYN_SENT2", |
| }; |
| |
| enum nf_ct_tcp_action { |
| NFCT_TCP_IGNORE, |
| NFCT_TCP_INVALID, |
| NFCT_TCP_ACCEPT, |
| }; |
| |
| #define SECS * HZ |
| #define MINS * 60 SECS |
| #define HOURS * 60 MINS |
| #define DAYS * 24 HOURS |
| |
| static const unsigned int tcp_timeouts[TCP_CONNTRACK_TIMEOUT_MAX] = { |
| [TCP_CONNTRACK_SYN_SENT] = 2 MINS, |
| [TCP_CONNTRACK_SYN_RECV] = 60 SECS, |
| [TCP_CONNTRACK_ESTABLISHED] = 5 DAYS, |
| [TCP_CONNTRACK_FIN_WAIT] = 2 MINS, |
| [TCP_CONNTRACK_CLOSE_WAIT] = 60 SECS, |
| [TCP_CONNTRACK_LAST_ACK] = 30 SECS, |
| [TCP_CONNTRACK_TIME_WAIT] = 2 MINS, |
| [TCP_CONNTRACK_CLOSE] = 10 SECS, |
| [TCP_CONNTRACK_SYN_SENT2] = 2 MINS, |
| /* RFC1122 says the R2 limit should be at least 100 seconds. |
| Linux uses 15 packets as limit, which corresponds |
| to ~13-30min depending on RTO. */ |
| [TCP_CONNTRACK_RETRANS] = 5 MINS, |
| [TCP_CONNTRACK_UNACK] = 5 MINS, |
| }; |
| |
| #define sNO TCP_CONNTRACK_NONE |
| #define sSS TCP_CONNTRACK_SYN_SENT |
| #define sSR TCP_CONNTRACK_SYN_RECV |
| #define sES TCP_CONNTRACK_ESTABLISHED |
| #define sFW TCP_CONNTRACK_FIN_WAIT |
| #define sCW TCP_CONNTRACK_CLOSE_WAIT |
| #define sLA TCP_CONNTRACK_LAST_ACK |
| #define sTW TCP_CONNTRACK_TIME_WAIT |
| #define sCL TCP_CONNTRACK_CLOSE |
| #define sS2 TCP_CONNTRACK_SYN_SENT2 |
| #define sIV TCP_CONNTRACK_MAX |
| #define sIG TCP_CONNTRACK_IGNORE |
| |
| /* What TCP flags are set from RST/SYN/FIN/ACK. */ |
| enum tcp_bit_set { |
| TCP_SYN_SET, |
| TCP_SYNACK_SET, |
| TCP_FIN_SET, |
| TCP_ACK_SET, |
| TCP_RST_SET, |
| TCP_NONE_SET, |
| }; |
| |
| /* |
| * The TCP state transition table needs a few words... |
| * |
| * We are the man in the middle. All the packets go through us |
| * but might get lost in transit to the destination. |
| * It is assumed that the destinations can't receive segments |
| * we haven't seen. |
| * |
| * The checked segment is in window, but our windows are *not* |
| * equivalent with the ones of the sender/receiver. We always |
| * try to guess the state of the current sender. |
| * |
| * The meaning of the states are: |
| * |
| * NONE: initial state |
| * SYN_SENT: SYN-only packet seen |
| * SYN_SENT2: SYN-only packet seen from reply dir, simultaneous open |
| * SYN_RECV: SYN-ACK packet seen |
| * ESTABLISHED: ACK packet seen |
| * FIN_WAIT: FIN packet seen |
| * CLOSE_WAIT: ACK seen (after FIN) |
| * LAST_ACK: FIN seen (after FIN) |
| * TIME_WAIT: last ACK seen |
| * CLOSE: closed connection (RST) |
| * |
| * Packets marked as IGNORED (sIG): |
| * if they may be either invalid or valid |
| * and the receiver may send back a connection |
| * closing RST or a SYN/ACK. |
| * |
| * Packets marked as INVALID (sIV): |
| * if we regard them as truly invalid packets |
| */ |
| static const u8 tcp_conntracks[2][6][TCP_CONNTRACK_MAX] = { |
| { |
| /* ORIGINAL */ |
| /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */ |
| /*syn*/ { sSS, sSS, sIG, sIG, sIG, sIG, sIG, sSS, sSS, sS2 }, |
| /* |
| * sNO -> sSS Initialize a new connection |
| * sSS -> sSS Retransmitted SYN |
| * sS2 -> sS2 Late retransmitted SYN |
| * sSR -> sIG |
| * sES -> sIG Error: SYNs in window outside the SYN_SENT state |
| * are errors. Receiver will reply with RST |
| * and close the connection. |
| * Or we are not in sync and hold a dead connection. |
| * sFW -> sIG |
| * sCW -> sIG |
| * sLA -> sIG |
| * sTW -> sSS Reopened connection (RFC 1122). |
| * sCL -> sSS |
| */ |
| /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */ |
| /*synack*/ { sIV, sIV, sSR, sIV, sIV, sIV, sIV, sIV, sIV, sSR }, |
| /* |
| * sNO -> sIV Too late and no reason to do anything |
| * sSS -> sIV Client can't send SYN and then SYN/ACK |
| * sS2 -> sSR SYN/ACK sent to SYN2 in simultaneous open |
| * sSR -> sSR Late retransmitted SYN/ACK in simultaneous open |
| * sES -> sIV Invalid SYN/ACK packets sent by the client |
| * sFW -> sIV |
| * sCW -> sIV |
| * sLA -> sIV |
| * sTW -> sIV |
| * sCL -> sIV |
| */ |
| /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */ |
| /*fin*/ { sIV, sIV, sFW, sFW, sLA, sLA, sLA, sTW, sCL, sIV }, |
| /* |
| * sNO -> sIV Too late and no reason to do anything... |
| * sSS -> sIV Client migth not send FIN in this state: |
| * we enforce waiting for a SYN/ACK reply first. |
| * sS2 -> sIV |
| * sSR -> sFW Close started. |
| * sES -> sFW |
| * sFW -> sLA FIN seen in both directions, waiting for |
| * the last ACK. |
| * Migth be a retransmitted FIN as well... |
| * sCW -> sLA |
| * sLA -> sLA Retransmitted FIN. Remain in the same state. |
| * sTW -> sTW |
| * sCL -> sCL |
| */ |
| /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */ |
| /*ack*/ { sES, sIV, sES, sES, sCW, sCW, sTW, sTW, sCL, sIV }, |
| /* |
| * sNO -> sES Assumed. |
| * sSS -> sIV ACK is invalid: we haven't seen a SYN/ACK yet. |
| * sS2 -> sIV |
| * sSR -> sES Established state is reached. |
| * sES -> sES :-) |
| * sFW -> sCW Normal close request answered by ACK. |
| * sCW -> sCW |
| * sLA -> sTW Last ACK detected (RFC5961 challenged) |
| * sTW -> sTW Retransmitted last ACK. Remain in the same state. |
| * sCL -> sCL |
| */ |
| /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */ |
| /*rst*/ { sIV, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL }, |
| /*none*/ { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV } |
| }, |
| { |
| /* REPLY */ |
| /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */ |
| /*syn*/ { sIV, sS2, sIV, sIV, sIV, sIV, sIV, sSS, sIV, sS2 }, |
| /* |
| * sNO -> sIV Never reached. |
| * sSS -> sS2 Simultaneous open |
| * sS2 -> sS2 Retransmitted simultaneous SYN |
| * sSR -> sIV Invalid SYN packets sent by the server |
| * sES -> sIV |
| * sFW -> sIV |
| * sCW -> sIV |
| * sLA -> sIV |
| * sTW -> sSS Reopened connection, but server may have switched role |
| * sCL -> sIV |
| */ |
| /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */ |
| /*synack*/ { sIV, sSR, sIG, sIG, sIG, sIG, sIG, sIG, sIG, sSR }, |
| /* |
| * sSS -> sSR Standard open. |
| * sS2 -> sSR Simultaneous open |
| * sSR -> sIG Retransmitted SYN/ACK, ignore it. |
| * sES -> sIG Late retransmitted SYN/ACK? |
| * sFW -> sIG Might be SYN/ACK answering ignored SYN |
| * sCW -> sIG |
| * sLA -> sIG |
| * sTW -> sIG |
| * sCL -> sIG |
| */ |
| /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */ |
| /*fin*/ { sIV, sIV, sFW, sFW, sLA, sLA, sLA, sTW, sCL, sIV }, |
| /* |
| * sSS -> sIV Server might not send FIN in this state. |
| * sS2 -> sIV |
| * sSR -> sFW Close started. |
| * sES -> sFW |
| * sFW -> sLA FIN seen in both directions. |
| * sCW -> sLA |
| * sLA -> sLA Retransmitted FIN. |
| * sTW -> sTW |
| * sCL -> sCL |
| */ |
| /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */ |
| /*ack*/ { sIV, sIG, sSR, sES, sCW, sCW, sTW, sTW, sCL, sIG }, |
| /* |
| * sSS -> sIG Might be a half-open connection. |
| * sS2 -> sIG |
| * sSR -> sSR Might answer late resent SYN. |
| * sES -> sES :-) |
| * sFW -> sCW Normal close request answered by ACK. |
| * sCW -> sCW |
| * sLA -> sTW Last ACK detected (RFC5961 challenged) |
| * sTW -> sTW Retransmitted last ACK. |
| * sCL -> sCL |
| */ |
| /* sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2 */ |
| /*rst*/ { sIV, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL }, |
| /*none*/ { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV } |
| } |
| }; |
| |
| #ifdef CONFIG_NF_CONNTRACK_PROCFS |
| /* Print out the private part of the conntrack. */ |
| static void tcp_print_conntrack(struct seq_file *s, struct nf_conn *ct) |
| { |
| if (test_bit(IPS_OFFLOAD_BIT, &ct->status)) |
| return; |
| |
| seq_printf(s, "%s ", tcp_conntrack_names[ct->proto.tcp.state]); |
| } |
| #endif |
| |
| static unsigned int get_conntrack_index(const struct tcphdr *tcph) |
| { |
| if (tcph->rst) return TCP_RST_SET; |
| else if (tcph->syn) return (tcph->ack ? TCP_SYNACK_SET : TCP_SYN_SET); |
| else if (tcph->fin) return TCP_FIN_SET; |
| else if (tcph->ack) return TCP_ACK_SET; |
| else return TCP_NONE_SET; |
| } |
| |
| /* TCP connection tracking based on 'Real Stateful TCP Packet Filtering |
| in IP Filter' by Guido van Rooij. |
| |
| http://www.sane.nl/events/sane2000/papers.html |
| http://www.darkart.com/mirrors/www.obfuscation.org/ipf/ |
| |
| The boundaries and the conditions are changed according to RFC793: |
| the packet must intersect the window (i.e. segments may be |
| after the right or before the left edge) and thus receivers may ACK |
| segments after the right edge of the window. |
| |
| td_maxend = max(sack + max(win,1)) seen in reply packets |
| td_maxwin = max(max(win, 1)) + (sack - ack) seen in sent packets |
| td_maxwin += seq + len - sender.td_maxend |
| if seq + len > sender.td_maxend |
| td_end = max(seq + len) seen in sent packets |
| |
| I. Upper bound for valid data: seq <= sender.td_maxend |
| II. Lower bound for valid data: seq + len >= sender.td_end - receiver.td_maxwin |
| III. Upper bound for valid (s)ack: sack <= receiver.td_end |
| IV. Lower bound for valid (s)ack: sack >= receiver.td_end - MAXACKWINDOW |
| |
| where sack is the highest right edge of sack block found in the packet |
| or ack in the case of packet without SACK option. |
| |
| The upper bound limit for a valid (s)ack is not ignored - |
| we doesn't have to deal with fragments. |
| */ |
| |
| static inline __u32 segment_seq_plus_len(__u32 seq, |
| size_t len, |
| unsigned int dataoff, |
| const struct tcphdr *tcph) |
| { |
| /* XXX Should I use payload length field in IP/IPv6 header ? |
| * - YK */ |
| return (seq + len - dataoff - tcph->doff*4 |
| + (tcph->syn ? 1 : 0) + (tcph->fin ? 1 : 0)); |
| } |
| |
| /* Fixme: what about big packets? */ |
| #define MAXACKWINCONST 66000 |
| #define MAXACKWINDOW(sender) \ |
| ((sender)->td_maxwin > MAXACKWINCONST ? (sender)->td_maxwin \ |
| : MAXACKWINCONST) |
| |
| /* |
| * Simplified tcp_parse_options routine from tcp_input.c |
| */ |
| static void tcp_options(const struct sk_buff *skb, |
| unsigned int dataoff, |
| const struct tcphdr *tcph, |
| struct ip_ct_tcp_state *state) |
| { |
| unsigned char buff[(15 * 4) - sizeof(struct tcphdr)]; |
| const unsigned char *ptr; |
| int length = (tcph->doff*4) - sizeof(struct tcphdr); |
| |
| if (!length) |
| return; |
| |
| ptr = skb_header_pointer(skb, dataoff + sizeof(struct tcphdr), |
| length, buff); |
| if (!ptr) |
| return; |
| |
| state->td_scale = 0; |
| state->flags &= IP_CT_TCP_FLAG_BE_LIBERAL; |
| |
| 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: |
| if (length < 2) |
| return; |
| opsize=*ptr++; |
| if (opsize < 2) /* "silly options" */ |
| return; |
| if (opsize > length) |
| return; /* don't parse partial options */ |
| |
| if (opcode == TCPOPT_SACK_PERM |
| && opsize == TCPOLEN_SACK_PERM) |
| state->flags |= IP_CT_TCP_FLAG_SACK_PERM; |
| else if (opcode == TCPOPT_WINDOW |
| && opsize == TCPOLEN_WINDOW) { |
| state->td_scale = *(u_int8_t *)ptr; |
| |
| if (state->td_scale > TCP_MAX_WSCALE) |
| state->td_scale = TCP_MAX_WSCALE; |
| |
| state->flags |= |
| IP_CT_TCP_FLAG_WINDOW_SCALE; |
| } |
| ptr += opsize - 2; |
| length -= opsize; |
| } |
| } |
| } |
| |
| static void tcp_sack(const struct sk_buff *skb, unsigned int dataoff, |
| const struct tcphdr *tcph, __u32 *sack) |
| { |
| unsigned char buff[(15 * 4) - sizeof(struct tcphdr)]; |
| const unsigned char *ptr; |
| int length = (tcph->doff*4) - sizeof(struct tcphdr); |
| __u32 tmp; |
| |
| if (!length) |
| return; |
| |
| ptr = skb_header_pointer(skb, dataoff + sizeof(struct tcphdr), |
| length, buff); |
| if (!ptr) |
| return; |
| |
| /* Fast path for timestamp-only option */ |
| if (length == TCPOLEN_TSTAMP_ALIGNED |
| && *(__be32 *)ptr == htonl((TCPOPT_NOP << 24) |
| | (TCPOPT_NOP << 16) |
| | (TCPOPT_TIMESTAMP << 8) |
| | TCPOLEN_TIMESTAMP)) |
| return; |
| |
| while (length > 0) { |
| int opcode = *ptr++; |
| int opsize, i; |
| |
| switch (opcode) { |
| case TCPOPT_EOL: |
| return; |
| case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */ |
| length--; |
| continue; |
| default: |
| if (length < 2) |
| return; |
| opsize = *ptr++; |
| if (opsize < 2) /* "silly options" */ |
| return; |
| if (opsize > length) |
| return; /* don't parse partial options */ |
| |
| if (opcode == TCPOPT_SACK |
| && opsize >= (TCPOLEN_SACK_BASE |
| + TCPOLEN_SACK_PERBLOCK) |
| && !((opsize - TCPOLEN_SACK_BASE) |
| % TCPOLEN_SACK_PERBLOCK)) { |
| for (i = 0; |
| i < (opsize - TCPOLEN_SACK_BASE); |
| i += TCPOLEN_SACK_PERBLOCK) { |
| tmp = get_unaligned_be32((__be32 *)(ptr+i)+1); |
| |
| if (after(tmp, *sack)) |
| *sack = tmp; |
| } |
| return; |
| } |
| ptr += opsize - 2; |
| length -= opsize; |
| } |
| } |
| } |
| |
| static void tcp_init_sender(struct ip_ct_tcp_state *sender, |
| struct ip_ct_tcp_state *receiver, |
| const struct sk_buff *skb, |
| unsigned int dataoff, |
| const struct tcphdr *tcph, |
| u32 end, u32 win) |
| { |
| /* SYN-ACK in reply to a SYN |
| * or SYN from reply direction in simultaneous open. |
| */ |
| sender->td_end = |
| sender->td_maxend = end; |
| sender->td_maxwin = (win == 0 ? 1 : win); |
| |
| tcp_options(skb, dataoff, tcph, sender); |
| /* RFC 1323: |
| * Both sides must send the Window Scale option |
| * to enable window scaling in either direction. |
| */ |
| if (!(sender->flags & IP_CT_TCP_FLAG_WINDOW_SCALE && |
| receiver->flags & IP_CT_TCP_FLAG_WINDOW_SCALE)) { |
| sender->td_scale = 0; |
| receiver->td_scale = 0; |
| } |
| } |
| |
| __printf(6, 7) |
| static enum nf_ct_tcp_action nf_tcp_log_invalid(const struct sk_buff *skb, |
| const struct nf_conn *ct, |
| const struct nf_hook_state *state, |
| const struct ip_ct_tcp_state *sender, |
| enum nf_ct_tcp_action ret, |
| const char *fmt, ...) |
| { |
| const struct nf_tcp_net *tn = nf_tcp_pernet(nf_ct_net(ct)); |
| struct va_format vaf; |
| va_list args; |
| bool be_liberal; |
| |
| be_liberal = sender->flags & IP_CT_TCP_FLAG_BE_LIBERAL || tn->tcp_be_liberal; |
| if (be_liberal) |
| return NFCT_TCP_ACCEPT; |
| |
| va_start(args, fmt); |
| vaf.fmt = fmt; |
| vaf.va = &args; |
| nf_ct_l4proto_log_invalid(skb, ct, state, "%pV", &vaf); |
| va_end(args); |
| |
| return ret; |
| } |
| |
| static enum nf_ct_tcp_action |
| tcp_in_window(struct nf_conn *ct, enum ip_conntrack_dir dir, |
| unsigned int index, const struct sk_buff *skb, |
| unsigned int dataoff, const struct tcphdr *tcph, |
| const struct nf_hook_state *hook_state) |
| { |
| struct ip_ct_tcp *state = &ct->proto.tcp; |
| struct ip_ct_tcp_state *sender = &state->seen[dir]; |
| struct ip_ct_tcp_state *receiver = &state->seen[!dir]; |
| __u32 seq, ack, sack, end, win, swin; |
| bool in_recv_win, seq_ok; |
| s32 receiver_offset; |
| u16 win_raw; |
| |
| /* |
| * Get the required data from the packet. |
| */ |
| seq = ntohl(tcph->seq); |
| ack = sack = ntohl(tcph->ack_seq); |
| win_raw = ntohs(tcph->window); |
| win = win_raw; |
| end = segment_seq_plus_len(seq, skb->len, dataoff, tcph); |
| |
| if (receiver->flags & IP_CT_TCP_FLAG_SACK_PERM) |
| tcp_sack(skb, dataoff, tcph, &sack); |
| |
| /* Take into account NAT sequence number mangling */ |
| receiver_offset = nf_ct_seq_offset(ct, !dir, ack - 1); |
| ack -= receiver_offset; |
| sack -= receiver_offset; |
| |
| if (sender->td_maxwin == 0) { |
| /* |
| * Initialize sender data. |
| */ |
| if (tcph->syn) { |
| tcp_init_sender(sender, receiver, |
| skb, dataoff, tcph, |
| end, win); |
| if (!tcph->ack) |
| /* Simultaneous open */ |
| return NFCT_TCP_ACCEPT; |
| } else { |
| /* |
| * We are in the middle of a connection, |
| * its history is lost for us. |
| * Let's try to use the data from the packet. |
| */ |
| sender->td_end = end; |
| swin = win << sender->td_scale; |
| sender->td_maxwin = (swin == 0 ? 1 : swin); |
| sender->td_maxend = end + sender->td_maxwin; |
| if (receiver->td_maxwin == 0) { |
| /* We haven't seen traffic in the other |
| * direction yet but we have to tweak window |
| * tracking to pass III and IV until that |
| * happens. |
| */ |
| receiver->td_end = receiver->td_maxend = sack; |
| } else if (sack == receiver->td_end + 1) { |
| /* Likely a reply to a keepalive. |
| * Needed for III. |
| */ |
| receiver->td_end++; |
| } |
| |
| } |
| } else if (tcph->syn && |
| after(end, sender->td_end) && |
| (state->state == TCP_CONNTRACK_SYN_SENT || |
| state->state == TCP_CONNTRACK_SYN_RECV)) { |
| /* |
| * RFC 793: "if a TCP is reinitialized ... then it need |
| * not wait at all; it must only be sure to use sequence |
| * numbers larger than those recently used." |
| * |
| * Re-init state for this direction, just like for the first |
| * syn(-ack) reply, it might differ in seq, ack or tcp options. |
| */ |
| tcp_init_sender(sender, receiver, |
| skb, dataoff, tcph, |
| end, win); |
| |
| if (dir == IP_CT_DIR_REPLY && !tcph->ack) |
| return NFCT_TCP_ACCEPT; |
| } |
| |
| if (!(tcph->ack)) { |
| /* |
| * If there is no ACK, just pretend it was set and OK. |
| */ |
| ack = sack = receiver->td_end; |
| } else if (((tcp_flag_word(tcph) & (TCP_FLAG_ACK|TCP_FLAG_RST)) == |
| (TCP_FLAG_ACK|TCP_FLAG_RST)) |
| && (ack == 0)) { |
| /* |
| * Broken TCP stacks, that set ACK in RST packets as well |
| * with zero ack value. |
| */ |
| ack = sack = receiver->td_end; |
| } |
| |
| if (tcph->rst && seq == 0 && state->state == TCP_CONNTRACK_SYN_SENT) |
| /* |
| * RST sent answering SYN. |
| */ |
| seq = end = sender->td_end; |
| |
| seq_ok = before(seq, sender->td_maxend + 1); |
| if (!seq_ok) { |
| u32 overshot = end - sender->td_maxend + 1; |
| bool ack_ok; |
| |
| ack_ok = after(sack, receiver->td_end - MAXACKWINDOW(sender) - 1); |
| in_recv_win = receiver->td_maxwin && |
| after(end, sender->td_end - receiver->td_maxwin - 1); |
| |
| if (in_recv_win && |
| ack_ok && |
| overshot <= receiver->td_maxwin && |
| before(sack, receiver->td_end + 1)) { |
| /* Work around TCPs that send more bytes than allowed by |
| * the receive window. |
| * |
| * If the (marked as invalid) packet is allowed to pass by |
| * the ruleset and the peer acks this data, then its possible |
| * all future packets will trigger 'ACK is over upper bound' check. |
| * |
| * Thus if only the sequence check fails then do update td_end so |
| * possible ACK for this data can update internal state. |
| */ |
| sender->td_end = end; |
| sender->flags |= IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED; |
| |
| return nf_tcp_log_invalid(skb, ct, hook_state, sender, NFCT_TCP_IGNORE, |
| "%u bytes more than expected", overshot); |
| } |
| |
| return nf_tcp_log_invalid(skb, ct, hook_state, sender, NFCT_TCP_INVALID, |
| "SEQ is over upper bound %u (over the window of the receiver)", |
| sender->td_maxend + 1); |
| } |
| |
| if (!before(sack, receiver->td_end + 1)) |
| return nf_tcp_log_invalid(skb, ct, hook_state, sender, NFCT_TCP_INVALID, |
| "ACK is over upper bound %u (ACKed data not seen yet)", |
| receiver->td_end + 1); |
| |
| /* Is the ending sequence in the receive window (if available)? */ |
| in_recv_win = !receiver->td_maxwin || |
| after(end, sender->td_end - receiver->td_maxwin - 1); |
| if (!in_recv_win) |
| return nf_tcp_log_invalid(skb, ct, hook_state, sender, NFCT_TCP_IGNORE, |
| "SEQ is under lower bound %u (already ACKed data retransmitted)", |
| sender->td_end - receiver->td_maxwin - 1); |
| if (!after(sack, receiver->td_end - MAXACKWINDOW(sender) - 1)) |
| return nf_tcp_log_invalid(skb, ct, hook_state, sender, NFCT_TCP_IGNORE, |
| "ignored ACK under lower bound %u (possible overly delayed)", |
| receiver->td_end - MAXACKWINDOW(sender) - 1); |
| |
| /* Take into account window scaling (RFC 1323). */ |
| if (!tcph->syn) |
| win <<= sender->td_scale; |
| |
| /* Update sender data. */ |
| swin = win + (sack - ack); |
| if (sender->td_maxwin < swin) |
| sender->td_maxwin = swin; |
| if (after(end, sender->td_end)) { |
| sender->td_end = end; |
| sender->flags |= IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED; |
| } |
| if (tcph->ack) { |
| if (!(sender->flags & IP_CT_TCP_FLAG_MAXACK_SET)) { |
| sender->td_maxack = ack; |
| sender->flags |= IP_CT_TCP_FLAG_MAXACK_SET; |
| } else if (after(ack, sender->td_maxack)) { |
| sender->td_maxack = ack; |
| } |
| } |
| |
| /* Update receiver data. */ |
| if (receiver->td_maxwin != 0 && after(end, sender->td_maxend)) |
| receiver->td_maxwin += end - sender->td_maxend; |
| if (after(sack + win, receiver->td_maxend - 1)) { |
| receiver->td_maxend = sack + win; |
| if (win == 0) |
| receiver->td_maxend++; |
| } |
| if (ack == receiver->td_end) |
| receiver->flags &= ~IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED; |
| |
| /* Check retransmissions. */ |
| if (index == TCP_ACK_SET) { |
| if (state->last_dir == dir && |
| state->last_seq == seq && |
| state->last_ack == ack && |
| state->last_end == end && |
| state->last_win == win_raw) { |
| state->retrans++; |
| } else { |
| state->last_dir = dir; |
| state->last_seq = seq; |
| state->last_ack = ack; |
| state->last_end = end; |
| state->last_win = win_raw; |
| state->retrans = 0; |
| } |
| } |
| |
| return NFCT_TCP_ACCEPT; |
| } |
| |
| static void __cold nf_tcp_handle_invalid(struct nf_conn *ct, |
| enum ip_conntrack_dir dir, |
| int index, |
| const struct sk_buff *skb, |
| const struct nf_hook_state *hook_state) |
| { |
| const unsigned int *timeouts; |
| const struct nf_tcp_net *tn; |
| unsigned int timeout; |
| u32 expires; |
| |
| if (!test_bit(IPS_ASSURED_BIT, &ct->status) || |
| test_bit(IPS_FIXED_TIMEOUT_BIT, &ct->status)) |
| return; |
| |
| /* We don't want to have connections hanging around in ESTABLISHED |
| * state for long time 'just because' conntrack deemed a FIN/RST |
| * out-of-window. |
| * |
| * Shrink the timeout just like when there is unacked data. |
| * This speeds up eviction of 'dead' connections where the |
| * connection and conntracks internal state are out of sync. |
| */ |
| switch (index) { |
| case TCP_RST_SET: |
| case TCP_FIN_SET: |
| break; |
| default: |
| return; |
| } |
| |
| if (ct->proto.tcp.last_dir != dir && |
| (ct->proto.tcp.last_index == TCP_FIN_SET || |
| ct->proto.tcp.last_index == TCP_RST_SET)) { |
| expires = nf_ct_expires(ct); |
| if (expires < 120 * HZ) |
| return; |
| |
| tn = nf_tcp_pernet(nf_ct_net(ct)); |
| timeouts = nf_ct_timeout_lookup(ct); |
| if (!timeouts) |
| timeouts = tn->timeouts; |
| |
| timeout = READ_ONCE(timeouts[TCP_CONNTRACK_UNACK]); |
| if (expires > timeout) { |
| nf_ct_l4proto_log_invalid(skb, ct, hook_state, |
| "packet (index %d, dir %d) response for index %d lower timeout to %u", |
| index, dir, ct->proto.tcp.last_index, timeout); |
| |
| WRITE_ONCE(ct->timeout, timeout + nfct_time_stamp); |
| } |
| } else { |
| ct->proto.tcp.last_index = index; |
| ct->proto.tcp.last_dir = dir; |
| } |
| } |
| |
| /* table of valid flag combinations - PUSH, ECE and CWR are always valid */ |
| static const u8 tcp_valid_flags[(TCPHDR_FIN|TCPHDR_SYN|TCPHDR_RST|TCPHDR_ACK| |
| TCPHDR_URG) + 1] = |
| { |
| [TCPHDR_SYN] = 1, |
| [TCPHDR_SYN|TCPHDR_URG] = 1, |
| [TCPHDR_SYN|TCPHDR_ACK] = 1, |
| [TCPHDR_RST] = 1, |
| [TCPHDR_RST|TCPHDR_ACK] = 1, |
| [TCPHDR_FIN|TCPHDR_ACK] = 1, |
| [TCPHDR_FIN|TCPHDR_ACK|TCPHDR_URG] = 1, |
| [TCPHDR_ACK] = 1, |
| [TCPHDR_ACK|TCPHDR_URG] = 1, |
| }; |
| |
| static void tcp_error_log(const struct sk_buff *skb, |
| const struct nf_hook_state *state, |
| const char *msg) |
| { |
| nf_l4proto_log_invalid(skb, state, IPPROTO_TCP, "%s", msg); |
| } |
| |
| /* Protect conntrack agaist broken packets. Code taken from ipt_unclean.c. */ |
| static bool tcp_error(const struct tcphdr *th, |
| struct sk_buff *skb, |
| unsigned int dataoff, |
| const struct nf_hook_state *state) |
| { |
| unsigned int tcplen = skb->len - dataoff; |
| u8 tcpflags; |
| |
| /* Not whole TCP header or malformed packet */ |
| if (th->doff*4 < sizeof(struct tcphdr) || tcplen < th->doff*4) { |
| tcp_error_log(skb, state, "truncated packet"); |
| return true; |
| } |
| |
| /* Checksum invalid? Ignore. |
| * We skip checking packets on the outgoing path |
| * because the checksum is assumed to be correct. |
| */ |
| /* FIXME: Source route IP option packets --RR */ |
| if (state->net->ct.sysctl_checksum && |
| state->hook == NF_INET_PRE_ROUTING && |
| nf_checksum(skb, state->hook, dataoff, IPPROTO_TCP, state->pf)) { |
| tcp_error_log(skb, state, "bad checksum"); |
| return true; |
| } |
| |
| /* Check TCP flags. */ |
| tcpflags = (tcp_flag_byte(th) & ~(TCPHDR_ECE|TCPHDR_CWR|TCPHDR_PSH)); |
| if (!tcp_valid_flags[tcpflags]) { |
| tcp_error_log(skb, state, "invalid tcp flag combination"); |
| return true; |
| } |
| |
| return false; |
| } |
| |
| static noinline bool tcp_new(struct nf_conn *ct, const struct sk_buff *skb, |
| unsigned int dataoff, |
| const struct tcphdr *th) |
| { |
| enum tcp_conntrack new_state; |
| struct net *net = nf_ct_net(ct); |
| const struct nf_tcp_net *tn = nf_tcp_pernet(net); |
| |
| /* Don't need lock here: this conntrack not in circulation yet */ |
| new_state = tcp_conntracks[0][get_conntrack_index(th)][TCP_CONNTRACK_NONE]; |
| |
| /* Invalid: delete conntrack */ |
| if (new_state >= TCP_CONNTRACK_MAX) { |
| pr_debug("nf_ct_tcp: invalid new deleting.\n"); |
| return false; |
| } |
| |
| if (new_state == TCP_CONNTRACK_SYN_SENT) { |
| memset(&ct->proto.tcp, 0, sizeof(ct->proto.tcp)); |
| /* SYN packet */ |
| ct->proto.tcp.seen[0].td_end = |
| segment_seq_plus_len(ntohl(th->seq), skb->len, |
| dataoff, th); |
| ct->proto.tcp.seen[0].td_maxwin = ntohs(th->window); |
| if (ct->proto.tcp.seen[0].td_maxwin == 0) |
| ct->proto.tcp.seen[0].td_maxwin = 1; |
| ct->proto.tcp.seen[0].td_maxend = |
| ct->proto.tcp.seen[0].td_end; |
| |
| tcp_options(skb, dataoff, th, &ct->proto.tcp.seen[0]); |
| } else if (tn->tcp_loose == 0) { |
| /* Don't try to pick up connections. */ |
| return false; |
| } else { |
| memset(&ct->proto.tcp, 0, sizeof(ct->proto.tcp)); |
| /* |
| * We are in the middle of a connection, |
| * its history is lost for us. |
| * Let's try to use the data from the packet. |
| */ |
| ct->proto.tcp.seen[0].td_end = |
| segment_seq_plus_len(ntohl(th->seq), skb->len, |
| dataoff, th); |
| ct->proto.tcp.seen[0].td_maxwin = ntohs(th->window); |
| if (ct->proto.tcp.seen[0].td_maxwin == 0) |
| ct->proto.tcp.seen[0].td_maxwin = 1; |
| ct->proto.tcp.seen[0].td_maxend = |
| ct->proto.tcp.seen[0].td_end + |
| ct->proto.tcp.seen[0].td_maxwin; |
| |
| /* We assume SACK and liberal window checking to handle |
| * window scaling */ |
| ct->proto.tcp.seen[0].flags = |
| ct->proto.tcp.seen[1].flags = IP_CT_TCP_FLAG_SACK_PERM | |
| IP_CT_TCP_FLAG_BE_LIBERAL; |
| } |
| |
| /* tcp_packet will set them */ |
| ct->proto.tcp.last_index = TCP_NONE_SET; |
| return true; |
| } |
| |
| static bool tcp_can_early_drop(const struct nf_conn *ct) |
| { |
| switch (ct->proto.tcp.state) { |
| case TCP_CONNTRACK_FIN_WAIT: |
| case TCP_CONNTRACK_LAST_ACK: |
| case TCP_CONNTRACK_TIME_WAIT: |
| case TCP_CONNTRACK_CLOSE: |
| case TCP_CONNTRACK_CLOSE_WAIT: |
| return true; |
| default: |
| break; |
| } |
| |
| return false; |
| } |
| |
| void nf_conntrack_tcp_set_closing(struct nf_conn *ct) |
| { |
| enum tcp_conntrack old_state; |
| const unsigned int *timeouts; |
| u32 timeout; |
| |
| if (!nf_ct_is_confirmed(ct)) |
| return; |
| |
| spin_lock_bh(&ct->lock); |
| old_state = ct->proto.tcp.state; |
| ct->proto.tcp.state = TCP_CONNTRACK_CLOSE; |
| |
| if (old_state == TCP_CONNTRACK_CLOSE || |
| test_bit(IPS_FIXED_TIMEOUT_BIT, &ct->status)) { |
| spin_unlock_bh(&ct->lock); |
| return; |
| } |
| |
| timeouts = nf_ct_timeout_lookup(ct); |
| if (!timeouts) { |
| const struct nf_tcp_net *tn; |
| |
| tn = nf_tcp_pernet(nf_ct_net(ct)); |
| timeouts = tn->timeouts; |
| } |
| |
| timeout = timeouts[TCP_CONNTRACK_CLOSE]; |
| WRITE_ONCE(ct->timeout, timeout + nfct_time_stamp); |
| |
| spin_unlock_bh(&ct->lock); |
| |
| nf_conntrack_event_cache(IPCT_PROTOINFO, ct); |
| } |
| |
| static void nf_ct_tcp_state_reset(struct ip_ct_tcp_state *state) |
| { |
| state->td_end = 0; |
| state->td_maxend = 0; |
| state->td_maxwin = 0; |
| state->td_maxack = 0; |
| state->td_scale = 0; |
| state->flags &= IP_CT_TCP_FLAG_BE_LIBERAL; |
| } |
| |
| /* Returns verdict for packet, or -1 for invalid. */ |
| int nf_conntrack_tcp_packet(struct nf_conn *ct, |
| struct sk_buff *skb, |
| unsigned int dataoff, |
| enum ip_conntrack_info ctinfo, |
| const struct nf_hook_state *state) |
| { |
| struct net *net = nf_ct_net(ct); |
| struct nf_tcp_net *tn = nf_tcp_pernet(net); |
| enum tcp_conntrack new_state, old_state; |
| unsigned int index, *timeouts; |
| enum nf_ct_tcp_action res; |
| enum ip_conntrack_dir dir; |
| const struct tcphdr *th; |
| struct tcphdr _tcph; |
| unsigned long timeout; |
| |
| th = skb_header_pointer(skb, dataoff, sizeof(_tcph), &_tcph); |
| if (th == NULL) |
| return -NF_ACCEPT; |
| |
| if (tcp_error(th, skb, dataoff, state)) |
| return -NF_ACCEPT; |
| |
| if (!nf_ct_is_confirmed(ct) && !tcp_new(ct, skb, dataoff, th)) |
| return -NF_ACCEPT; |
| |
| spin_lock_bh(&ct->lock); |
| old_state = ct->proto.tcp.state; |
| dir = CTINFO2DIR(ctinfo); |
| index = get_conntrack_index(th); |
| new_state = tcp_conntracks[dir][index][old_state]; |
| |
| switch (new_state) { |
| case TCP_CONNTRACK_SYN_SENT: |
| if (old_state < TCP_CONNTRACK_TIME_WAIT) |
| break; |
| /* RFC 1122: "When a connection is closed actively, |
| * it MUST linger in TIME-WAIT state for a time 2xMSL |
| * (Maximum Segment Lifetime). However, it MAY accept |
| * a new SYN from the remote TCP to reopen the connection |
| * directly from TIME-WAIT state, if..." |
| * We ignore the conditions because we are in the |
| * TIME-WAIT state anyway. |
| * |
| * Handle aborted connections: we and the server |
| * think there is an existing connection but the client |
| * aborts it and starts a new one. |
| */ |
| if (((ct->proto.tcp.seen[dir].flags |
| | ct->proto.tcp.seen[!dir].flags) |
| & IP_CT_TCP_FLAG_CLOSE_INIT) |
| || (ct->proto.tcp.last_dir == dir |
| && ct->proto.tcp.last_index == TCP_RST_SET)) { |
| /* Attempt to reopen a closed/aborted connection. |
| * Delete this connection and look up again. */ |
| spin_unlock_bh(&ct->lock); |
| |
| /* Only repeat if we can actually remove the timer. |
| * Destruction may already be in progress in process |
| * context and we must give it a chance to terminate. |
| */ |
| if (nf_ct_kill(ct)) |
| return -NF_REPEAT; |
| return NF_DROP; |
| } |
| fallthrough; |
| case TCP_CONNTRACK_IGNORE: |
| /* Ignored packets: |
| * |
| * Our connection entry may be out of sync, so ignore |
| * packets which may signal the real connection between |
| * the client and the server. |
| * |
| * a) SYN in ORIGINAL |
| * b) SYN/ACK in REPLY |
| * c) ACK in reply direction after initial SYN in original. |
| * |
| * If the ignored packet is invalid, the receiver will send |
| * a RST we'll catch below. |
| */ |
| if (index == TCP_SYNACK_SET |
| && ct->proto.tcp.last_index == TCP_SYN_SET |
| && ct->proto.tcp.last_dir != dir |
| && ntohl(th->ack_seq) == ct->proto.tcp.last_end) { |
| /* b) This SYN/ACK acknowledges a SYN that we earlier |
| * ignored as invalid. This means that the client and |
| * the server are both in sync, while the firewall is |
| * not. We get in sync from the previously annotated |
| * values. |
| */ |
| old_state = TCP_CONNTRACK_SYN_SENT; |
| new_state = TCP_CONNTRACK_SYN_RECV; |
| ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_end = |
| ct->proto.tcp.last_end; |
| ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_maxend = |
| ct->proto.tcp.last_end; |
| ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_maxwin = |
| ct->proto.tcp.last_win == 0 ? |
| 1 : ct->proto.tcp.last_win; |
| ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_scale = |
| ct->proto.tcp.last_wscale; |
| ct->proto.tcp.last_flags &= ~IP_CT_EXP_CHALLENGE_ACK; |
| ct->proto.tcp.seen[ct->proto.tcp.last_dir].flags = |
| ct->proto.tcp.last_flags; |
| nf_ct_tcp_state_reset(&ct->proto.tcp.seen[dir]); |
| break; |
| } |
| ct->proto.tcp.last_index = index; |
| ct->proto.tcp.last_dir = dir; |
| ct->proto.tcp.last_seq = ntohl(th->seq); |
| ct->proto.tcp.last_end = |
| segment_seq_plus_len(ntohl(th->seq), skb->len, dataoff, th); |
| ct->proto.tcp.last_win = ntohs(th->window); |
| |
| /* a) This is a SYN in ORIGINAL. The client and the server |
| * may be in sync but we are not. In that case, we annotate |
| * the TCP options and let the packet go through. If it is a |
| * valid SYN packet, the server will reply with a SYN/ACK, and |
| * then we'll get in sync. Otherwise, the server potentially |
| * responds with a challenge ACK if implementing RFC5961. |
| */ |
| if (index == TCP_SYN_SET && dir == IP_CT_DIR_ORIGINAL) { |
| struct ip_ct_tcp_state seen = {}; |
| |
| ct->proto.tcp.last_flags = |
| ct->proto.tcp.last_wscale = 0; |
| tcp_options(skb, dataoff, th, &seen); |
| if (seen.flags & IP_CT_TCP_FLAG_WINDOW_SCALE) { |
| ct->proto.tcp.last_flags |= |
| IP_CT_TCP_FLAG_WINDOW_SCALE; |
| ct->proto.tcp.last_wscale = seen.td_scale; |
| } |
| if (seen.flags & IP_CT_TCP_FLAG_SACK_PERM) { |
| ct->proto.tcp.last_flags |= |
| IP_CT_TCP_FLAG_SACK_PERM; |
| } |
| /* Mark the potential for RFC5961 challenge ACK, |
| * this pose a special problem for LAST_ACK state |
| * as ACK is intrepretated as ACKing last FIN. |
| */ |
| if (old_state == TCP_CONNTRACK_LAST_ACK) |
| ct->proto.tcp.last_flags |= |
| IP_CT_EXP_CHALLENGE_ACK; |
| } |
| |
| /* possible challenge ack reply to syn */ |
| if (old_state == TCP_CONNTRACK_SYN_SENT && |
| index == TCP_ACK_SET && |
| dir == IP_CT_DIR_REPLY) |
| ct->proto.tcp.last_ack = ntohl(th->ack_seq); |
| |
| spin_unlock_bh(&ct->lock); |
| nf_ct_l4proto_log_invalid(skb, ct, state, |
| "packet (index %d) in dir %d ignored, state %s", |
| index, dir, |
| tcp_conntrack_names[old_state]); |
| return NF_ACCEPT; |
| case TCP_CONNTRACK_MAX: |
| /* Special case for SYN proxy: when the SYN to the server or |
| * the SYN/ACK from the server is lost, the client may transmit |
| * a keep-alive packet while in SYN_SENT state. This needs to |
| * be associated with the original conntrack entry in order to |
| * generate a new SYN with the correct sequence number. |
| */ |
| if (nfct_synproxy(ct) && old_state == TCP_CONNTRACK_SYN_SENT && |
| index == TCP_ACK_SET && dir == IP_CT_DIR_ORIGINAL && |
| ct->proto.tcp.last_dir == IP_CT_DIR_ORIGINAL && |
| ct->proto.tcp.seen[dir].td_end - 1 == ntohl(th->seq)) { |
| pr_debug("nf_ct_tcp: SYN proxy client keep alive\n"); |
| spin_unlock_bh(&ct->lock); |
| return NF_ACCEPT; |
| } |
| |
| /* Invalid packet */ |
| spin_unlock_bh(&ct->lock); |
| nf_ct_l4proto_log_invalid(skb, ct, state, |
| "packet (index %d) in dir %d invalid, state %s", |
| index, dir, |
| tcp_conntrack_names[old_state]); |
| return -NF_ACCEPT; |
| case TCP_CONNTRACK_TIME_WAIT: |
| /* RFC5961 compliance cause stack to send "challenge-ACK" |
| * e.g. in response to spurious SYNs. Conntrack MUST |
| * not believe this ACK is acking last FIN. |
| */ |
| if (old_state == TCP_CONNTRACK_LAST_ACK && |
| index == TCP_ACK_SET && |
| ct->proto.tcp.last_dir != dir && |
| ct->proto.tcp.last_index == TCP_SYN_SET && |
| (ct->proto.tcp.last_flags & IP_CT_EXP_CHALLENGE_ACK)) { |
| /* Detected RFC5961 challenge ACK */ |
| ct->proto.tcp.last_flags &= ~IP_CT_EXP_CHALLENGE_ACK; |
| spin_unlock_bh(&ct->lock); |
| nf_ct_l4proto_log_invalid(skb, ct, state, "challenge-ack ignored"); |
| return NF_ACCEPT; /* Don't change state */ |
| } |
| break; |
| case TCP_CONNTRACK_SYN_SENT2: |
| /* tcp_conntracks table is not smart enough to handle |
| * simultaneous open. |
| */ |
| ct->proto.tcp.last_flags |= IP_CT_TCP_SIMULTANEOUS_OPEN; |
| break; |
| case TCP_CONNTRACK_SYN_RECV: |
| if (dir == IP_CT_DIR_REPLY && index == TCP_ACK_SET && |
| ct->proto.tcp.last_flags & IP_CT_TCP_SIMULTANEOUS_OPEN) |
| new_state = TCP_CONNTRACK_ESTABLISHED; |
| break; |
| case TCP_CONNTRACK_CLOSE: |
| if (index != TCP_RST_SET) |
| break; |
| |
| /* If we are closing, tuple might have been re-used already. |
| * last_index, last_ack, and all other ct fields used for |
| * sequence/window validation are outdated in that case. |
| * |
| * As the conntrack can already be expired by GC under pressure, |
| * just skip validation checks. |
| */ |
| if (tcp_can_early_drop(ct)) |
| goto in_window; |
| |
| /* td_maxack might be outdated if we let a SYN through earlier */ |
| if ((ct->proto.tcp.seen[!dir].flags & IP_CT_TCP_FLAG_MAXACK_SET) && |
| ct->proto.tcp.last_index != TCP_SYN_SET) { |
| u32 seq = ntohl(th->seq); |
| |
| /* If we are not in established state and SEQ=0 this is most |
| * likely an answer to a SYN we let go through above (last_index |
| * can be updated due to out-of-order ACKs). |
| */ |
| if (seq == 0 && !nf_conntrack_tcp_established(ct)) |
| break; |
| |
| if (before(seq, ct->proto.tcp.seen[!dir].td_maxack) && |
| !tn->tcp_ignore_invalid_rst) { |
| /* Invalid RST */ |
| spin_unlock_bh(&ct->lock); |
| nf_ct_l4proto_log_invalid(skb, ct, state, "invalid rst"); |
| return -NF_ACCEPT; |
| } |
| |
| if (!nf_conntrack_tcp_established(ct) || |
| seq == ct->proto.tcp.seen[!dir].td_maxack) |
| break; |
| |
| /* Check if rst is part of train, such as |
| * foo:80 > bar:4379: P, 235946583:235946602(19) ack 42 |
| * foo:80 > bar:4379: R, 235946602:235946602(0) ack 42 |
| */ |
| if (ct->proto.tcp.last_index == TCP_ACK_SET && |
| ct->proto.tcp.last_dir == dir && |
| seq == ct->proto.tcp.last_end) |
| break; |
| |
| /* ... RST sequence number doesn't match exactly, keep |
| * established state to allow a possible challenge ACK. |
| */ |
| new_state = old_state; |
| } |
| if (((test_bit(IPS_SEEN_REPLY_BIT, &ct->status) |
| && ct->proto.tcp.last_index == TCP_SYN_SET) |
| || (!test_bit(IPS_ASSURED_BIT, &ct->status) |
| && ct->proto.tcp.last_index == TCP_ACK_SET)) |
| && ntohl(th->ack_seq) == ct->proto.tcp.last_end) { |
| /* RST sent to invalid SYN or ACK we had let through |
| * at a) and c) above: |
| * |
| * a) SYN was in window then |
| * c) we hold a half-open connection. |
| * |
| * Delete our connection entry. |
| * We skip window checking, because packet might ACK |
| * segments we ignored. */ |
| goto in_window; |
| } |
| |
| /* Reset in response to a challenge-ack we let through earlier */ |
| if (old_state == TCP_CONNTRACK_SYN_SENT && |
| ct->proto.tcp.last_index == TCP_ACK_SET && |
| ct->proto.tcp.last_dir == IP_CT_DIR_REPLY && |
| ntohl(th->seq) == ct->proto.tcp.last_ack) |
| goto in_window; |
| |
| break; |
| default: |
| /* Keep compilers happy. */ |
| break; |
| } |
| |
| res = tcp_in_window(ct, dir, index, |
| skb, dataoff, th, state); |
| switch (res) { |
| case NFCT_TCP_IGNORE: |
| spin_unlock_bh(&ct->lock); |
| return NF_ACCEPT; |
| case NFCT_TCP_INVALID: |
| nf_tcp_handle_invalid(ct, dir, index, skb, state); |
| spin_unlock_bh(&ct->lock); |
| return -NF_ACCEPT; |
| case NFCT_TCP_ACCEPT: |
| break; |
| } |
| in_window: |
| /* From now on we have got in-window packets */ |
| ct->proto.tcp.last_index = index; |
| ct->proto.tcp.last_dir = dir; |
| |
| ct->proto.tcp.state = new_state; |
| if (old_state != new_state |
| && new_state == TCP_CONNTRACK_FIN_WAIT) |
| ct->proto.tcp.seen[dir].flags |= IP_CT_TCP_FLAG_CLOSE_INIT; |
| |
| timeouts = nf_ct_timeout_lookup(ct); |
| if (!timeouts) |
| timeouts = tn->timeouts; |
| |
| if (ct->proto.tcp.retrans >= tn->tcp_max_retrans && |
| timeouts[new_state] > timeouts[TCP_CONNTRACK_RETRANS]) |
| timeout = timeouts[TCP_CONNTRACK_RETRANS]; |
| else if (unlikely(index == TCP_RST_SET)) |
| timeout = timeouts[TCP_CONNTRACK_CLOSE]; |
| else if ((ct->proto.tcp.seen[0].flags | ct->proto.tcp.seen[1].flags) & |
| IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED && |
| timeouts[new_state] > timeouts[TCP_CONNTRACK_UNACK]) |
| timeout = timeouts[TCP_CONNTRACK_UNACK]; |
| else if (ct->proto.tcp.last_win == 0 && |
| timeouts[new_state] > timeouts[TCP_CONNTRACK_RETRANS]) |
| timeout = timeouts[TCP_CONNTRACK_RETRANS]; |
| else |
| timeout = timeouts[new_state]; |
| spin_unlock_bh(&ct->lock); |
| |
| if (new_state != old_state) |
| nf_conntrack_event_cache(IPCT_PROTOINFO, ct); |
| |
| if (!test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) { |
| /* If only reply is a RST, we can consider ourselves not to |
| have an established connection: this is a fairly common |
| problem case, so we can delete the conntrack |
| immediately. --RR */ |
| if (th->rst) { |
| nf_ct_kill_acct(ct, ctinfo, skb); |
| return NF_ACCEPT; |
| } |
| |
| if (index == TCP_SYN_SET && old_state == TCP_CONNTRACK_SYN_SENT) { |
| /* do not renew timeout on SYN retransmit. |
| * |
| * Else port reuse by client or NAT middlebox can keep |
| * entry alive indefinitely (including nat info). |
| */ |
| return NF_ACCEPT; |
| } |
| |
| /* ESTABLISHED without SEEN_REPLY, i.e. mid-connection |
| * pickup with loose=1. Avoid large ESTABLISHED timeout. |
| */ |
| if (new_state == TCP_CONNTRACK_ESTABLISHED && |
| timeout > timeouts[TCP_CONNTRACK_UNACK]) |
| timeout = timeouts[TCP_CONNTRACK_UNACK]; |
| } else if (!test_bit(IPS_ASSURED_BIT, &ct->status) |
| && (old_state == TCP_CONNTRACK_SYN_RECV |
| || old_state == TCP_CONNTRACK_ESTABLISHED) |
| && new_state == TCP_CONNTRACK_ESTABLISHED) { |
| /* Set ASSURED if we see valid ack in ESTABLISHED |
| after SYN_RECV or a valid answer for a picked up |
| connection. */ |
| set_bit(IPS_ASSURED_BIT, &ct->status); |
| nf_conntrack_event_cache(IPCT_ASSURED, ct); |
| } |
| nf_ct_refresh_acct(ct, ctinfo, skb, timeout); |
| |
| return NF_ACCEPT; |
| } |
| |
| #if IS_ENABLED(CONFIG_NF_CT_NETLINK) |
| |
| #include <linux/netfilter/nfnetlink.h> |
| #include <linux/netfilter/nfnetlink_conntrack.h> |
| |
| static int tcp_to_nlattr(struct sk_buff *skb, struct nlattr *nla, |
| struct nf_conn *ct, bool destroy) |
| { |
| struct nlattr *nest_parms; |
| struct nf_ct_tcp_flags tmp = {}; |
| |
| spin_lock_bh(&ct->lock); |
| nest_parms = nla_nest_start(skb, CTA_PROTOINFO_TCP); |
| if (!nest_parms) |
| goto nla_put_failure; |
| |
| if (nla_put_u8(skb, CTA_PROTOINFO_TCP_STATE, ct->proto.tcp.state)) |
| goto nla_put_failure; |
| |
| if (destroy) |
| goto skip_state; |
| |
| if (nla_put_u8(skb, CTA_PROTOINFO_TCP_WSCALE_ORIGINAL, |
| ct->proto.tcp.seen[0].td_scale) || |
| nla_put_u8(skb, CTA_PROTOINFO_TCP_WSCALE_REPLY, |
| ct->proto.tcp.seen[1].td_scale)) |
| goto nla_put_failure; |
| |
| tmp.flags = ct->proto.tcp.seen[0].flags; |
| if (nla_put(skb, CTA_PROTOINFO_TCP_FLAGS_ORIGINAL, |
| sizeof(struct nf_ct_tcp_flags), &tmp)) |
| goto nla_put_failure; |
| |
| tmp.flags = ct->proto.tcp.seen[1].flags; |
| if (nla_put(skb, CTA_PROTOINFO_TCP_FLAGS_REPLY, |
| sizeof(struct nf_ct_tcp_flags), &tmp)) |
| goto nla_put_failure; |
| skip_state: |
| spin_unlock_bh(&ct->lock); |
| nla_nest_end(skb, nest_parms); |
| |
| return 0; |
| |
| nla_put_failure: |
| spin_unlock_bh(&ct->lock); |
| return -1; |
| } |
| |
| static const struct nla_policy tcp_nla_policy[CTA_PROTOINFO_TCP_MAX+1] = { |
| [CTA_PROTOINFO_TCP_STATE] = { .type = NLA_U8 }, |
| [CTA_PROTOINFO_TCP_WSCALE_ORIGINAL] = { .type = NLA_U8 }, |
| [CTA_PROTOINFO_TCP_WSCALE_REPLY] = { .type = NLA_U8 }, |
| [CTA_PROTOINFO_TCP_FLAGS_ORIGINAL] = { .len = sizeof(struct nf_ct_tcp_flags) }, |
| [CTA_PROTOINFO_TCP_FLAGS_REPLY] = { .len = sizeof(struct nf_ct_tcp_flags) }, |
| }; |
| |
| #define TCP_NLATTR_SIZE ( \ |
| NLA_ALIGN(NLA_HDRLEN + 1) + \ |
| NLA_ALIGN(NLA_HDRLEN + 1) + \ |
| NLA_ALIGN(NLA_HDRLEN + sizeof(struct nf_ct_tcp_flags)) + \ |
| NLA_ALIGN(NLA_HDRLEN + sizeof(struct nf_ct_tcp_flags))) |
| |
| static int nlattr_to_tcp(struct nlattr *cda[], struct nf_conn *ct) |
| { |
| struct nlattr *pattr = cda[CTA_PROTOINFO_TCP]; |
| struct nlattr *tb[CTA_PROTOINFO_TCP_MAX+1]; |
| int err; |
| |
| /* updates could not contain anything about the private |
| * protocol info, in that case skip the parsing */ |
| if (!pattr) |
| return 0; |
| |
| err = nla_parse_nested_deprecated(tb, CTA_PROTOINFO_TCP_MAX, pattr, |
| tcp_nla_policy, NULL); |
| if (err < 0) |
| return err; |
| |
| if (tb[CTA_PROTOINFO_TCP_STATE] && |
| nla_get_u8(tb[CTA_PROTOINFO_TCP_STATE]) >= TCP_CONNTRACK_MAX) |
| return -EINVAL; |
| |
| spin_lock_bh(&ct->lock); |
| if (tb[CTA_PROTOINFO_TCP_STATE]) |
| ct->proto.tcp.state = nla_get_u8(tb[CTA_PROTOINFO_TCP_STATE]); |
| |
| if (tb[CTA_PROTOINFO_TCP_FLAGS_ORIGINAL]) { |
| struct nf_ct_tcp_flags *attr = |
| nla_data(tb[CTA_PROTOINFO_TCP_FLAGS_ORIGINAL]); |
| ct->proto.tcp.seen[0].flags &= ~attr->mask; |
| ct->proto.tcp.seen[0].flags |= attr->flags & attr->mask; |
| } |
| |
| if (tb[CTA_PROTOINFO_TCP_FLAGS_REPLY]) { |
| struct nf_ct_tcp_flags *attr = |
| nla_data(tb[CTA_PROTOINFO_TCP_FLAGS_REPLY]); |
| ct->proto.tcp.seen[1].flags &= ~attr->mask; |
| ct->proto.tcp.seen[1].flags |= attr->flags & attr->mask; |
| } |
| |
| if (tb[CTA_PROTOINFO_TCP_WSCALE_ORIGINAL] && |
| tb[CTA_PROTOINFO_TCP_WSCALE_REPLY] && |
| ct->proto.tcp.seen[0].flags & IP_CT_TCP_FLAG_WINDOW_SCALE && |
| ct->proto.tcp.seen[1].flags & IP_CT_TCP_FLAG_WINDOW_SCALE) { |
| ct->proto.tcp.seen[0].td_scale = |
| nla_get_u8(tb[CTA_PROTOINFO_TCP_WSCALE_ORIGINAL]); |
| ct->proto.tcp.seen[1].td_scale = |
| nla_get_u8(tb[CTA_PROTOINFO_TCP_WSCALE_REPLY]); |
| } |
| spin_unlock_bh(&ct->lock); |
| |
| return 0; |
| } |
| |
| static unsigned int tcp_nlattr_tuple_size(void) |
| { |
| static unsigned int size __read_mostly; |
| |
| if (!size) |
| size = nla_policy_len(nf_ct_port_nla_policy, CTA_PROTO_MAX + 1); |
| |
| return size; |
| } |
| #endif |
| |
| #ifdef CONFIG_NF_CONNTRACK_TIMEOUT |
| |
| #include <linux/netfilter/nfnetlink.h> |
| #include <linux/netfilter/nfnetlink_cttimeout.h> |
| |
| static int tcp_timeout_nlattr_to_obj(struct nlattr *tb[], |
| struct net *net, void *data) |
| { |
| struct nf_tcp_net *tn = nf_tcp_pernet(net); |
| unsigned int *timeouts = data; |
| int i; |
| |
| if (!timeouts) |
| timeouts = tn->timeouts; |
| /* set default TCP timeouts. */ |
| for (i=0; i<TCP_CONNTRACK_TIMEOUT_MAX; i++) |
| timeouts[i] = tn->timeouts[i]; |
| |
| if (tb[CTA_TIMEOUT_TCP_SYN_SENT]) { |
| timeouts[TCP_CONNTRACK_SYN_SENT] = |
| ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_SYN_SENT]))*HZ; |
| } |
| |
| if (tb[CTA_TIMEOUT_TCP_SYN_RECV]) { |
| timeouts[TCP_CONNTRACK_SYN_RECV] = |
| ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_SYN_RECV]))*HZ; |
| } |
| if (tb[CTA_TIMEOUT_TCP_ESTABLISHED]) { |
| timeouts[TCP_CONNTRACK_ESTABLISHED] = |
| ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_ESTABLISHED]))*HZ; |
| } |
| if (tb[CTA_TIMEOUT_TCP_FIN_WAIT]) { |
| timeouts[TCP_CONNTRACK_FIN_WAIT] = |
| ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_FIN_WAIT]))*HZ; |
| } |
| if (tb[CTA_TIMEOUT_TCP_CLOSE_WAIT]) { |
| timeouts[TCP_CONNTRACK_CLOSE_WAIT] = |
| ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_CLOSE_WAIT]))*HZ; |
| } |
| if (tb[CTA_TIMEOUT_TCP_LAST_ACK]) { |
| timeouts[TCP_CONNTRACK_LAST_ACK] = |
| ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_LAST_ACK]))*HZ; |
| } |
| if (tb[CTA_TIMEOUT_TCP_TIME_WAIT]) { |
| timeouts[TCP_CONNTRACK_TIME_WAIT] = |
| ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_TIME_WAIT]))*HZ; |
| } |
| if (tb[CTA_TIMEOUT_TCP_CLOSE]) { |
| timeouts[TCP_CONNTRACK_CLOSE] = |
| ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_CLOSE]))*HZ; |
| } |
| if (tb[CTA_TIMEOUT_TCP_SYN_SENT2]) { |
| timeouts[TCP_CONNTRACK_SYN_SENT2] = |
| ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_SYN_SENT2]))*HZ; |
| } |
| if (tb[CTA_TIMEOUT_TCP_RETRANS]) { |
| timeouts[TCP_CONNTRACK_RETRANS] = |
| ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_RETRANS]))*HZ; |
| } |
| if (tb[CTA_TIMEOUT_TCP_UNACK]) { |
| timeouts[TCP_CONNTRACK_UNACK] = |
| ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_UNACK]))*HZ; |
| } |
| |
| timeouts[CTA_TIMEOUT_TCP_UNSPEC] = timeouts[CTA_TIMEOUT_TCP_SYN_SENT]; |
| return 0; |
| } |
| |
| static int |
| tcp_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data) |
| { |
| const unsigned int *timeouts = data; |
| |
| if (nla_put_be32(skb, CTA_TIMEOUT_TCP_SYN_SENT, |
| htonl(timeouts[TCP_CONNTRACK_SYN_SENT] / HZ)) || |
| nla_put_be32(skb, CTA_TIMEOUT_TCP_SYN_RECV, |
| htonl(timeouts[TCP_CONNTRACK_SYN_RECV] / HZ)) || |
| nla_put_be32(skb, CTA_TIMEOUT_TCP_ESTABLISHED, |
| htonl(timeouts[TCP_CONNTRACK_ESTABLISHED] / HZ)) || |
| nla_put_be32(skb, CTA_TIMEOUT_TCP_FIN_WAIT, |
| htonl(timeouts[TCP_CONNTRACK_FIN_WAIT] / HZ)) || |
| nla_put_be32(skb, CTA_TIMEOUT_TCP_CLOSE_WAIT, |
| htonl(timeouts[TCP_CONNTRACK_CLOSE_WAIT] / HZ)) || |
| nla_put_be32(skb, CTA_TIMEOUT_TCP_LAST_ACK, |
| htonl(timeouts[TCP_CONNTRACK_LAST_ACK] / HZ)) || |
| nla_put_be32(skb, CTA_TIMEOUT_TCP_TIME_WAIT, |
| htonl(timeouts[TCP_CONNTRACK_TIME_WAIT] / HZ)) || |
| nla_put_be32(skb, CTA_TIMEOUT_TCP_CLOSE, |
| htonl(timeouts[TCP_CONNTRACK_CLOSE] / HZ)) || |
| nla_put_be32(skb, CTA_TIMEOUT_TCP_SYN_SENT2, |
| htonl(timeouts[TCP_CONNTRACK_SYN_SENT2] / HZ)) || |
| nla_put_be32(skb, CTA_TIMEOUT_TCP_RETRANS, |
| htonl(timeouts[TCP_CONNTRACK_RETRANS] / HZ)) || |
| nla_put_be32(skb, CTA_TIMEOUT_TCP_UNACK, |
| htonl(timeouts[TCP_CONNTRACK_UNACK] / HZ))) |
| goto nla_put_failure; |
| return 0; |
| |
| nla_put_failure: |
| return -ENOSPC; |
| } |
| |
| static const struct nla_policy tcp_timeout_nla_policy[CTA_TIMEOUT_TCP_MAX+1] = { |
| [CTA_TIMEOUT_TCP_SYN_SENT] = { .type = NLA_U32 }, |
| [CTA_TIMEOUT_TCP_SYN_RECV] = { .type = NLA_U32 }, |
| [CTA_TIMEOUT_TCP_ESTABLISHED] = { .type = NLA_U32 }, |
| [CTA_TIMEOUT_TCP_FIN_WAIT] = { .type = NLA_U32 }, |
| [CTA_TIMEOUT_TCP_CLOSE_WAIT] = { .type = NLA_U32 }, |
| [CTA_TIMEOUT_TCP_LAST_ACK] = { .type = NLA_U32 }, |
| [CTA_TIMEOUT_TCP_TIME_WAIT] = { .type = NLA_U32 }, |
| [CTA_TIMEOUT_TCP_CLOSE] = { .type = NLA_U32 }, |
| [CTA_TIMEOUT_TCP_SYN_SENT2] = { .type = NLA_U32 }, |
| [CTA_TIMEOUT_TCP_RETRANS] = { .type = NLA_U32 }, |
| [CTA_TIMEOUT_TCP_UNACK] = { .type = NLA_U32 }, |
| }; |
| #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */ |
| |
| void nf_conntrack_tcp_init_net(struct net *net) |
| { |
| struct nf_tcp_net *tn = nf_tcp_pernet(net); |
| int i; |
| |
| for (i = 0; i < TCP_CONNTRACK_TIMEOUT_MAX; i++) |
| tn->timeouts[i] = tcp_timeouts[i]; |
| |
| /* timeouts[0] is unused, make it same as SYN_SENT so |
| * ->timeouts[0] contains 'new' timeout, like udp or icmp. |
| */ |
| tn->timeouts[0] = tcp_timeouts[TCP_CONNTRACK_SYN_SENT]; |
| |
| /* If it is set to zero, we disable picking up already established |
| * connections. |
| */ |
| tn->tcp_loose = 1; |
| |
| /* "Be conservative in what you do, |
| * be liberal in what you accept from others." |
| * If it's non-zero, we mark only out of window RST segments as INVALID. |
| */ |
| tn->tcp_be_liberal = 0; |
| |
| /* If it's non-zero, we turn off RST sequence number check */ |
| tn->tcp_ignore_invalid_rst = 0; |
| |
| /* Max number of the retransmitted packets without receiving an (acceptable) |
| * ACK from the destination. If this number is reached, a shorter timer |
| * will be started. |
| */ |
| tn->tcp_max_retrans = 3; |
| |
| #if IS_ENABLED(CONFIG_NF_FLOW_TABLE) |
| tn->offload_timeout = 30 * HZ; |
| #endif |
| } |
| |
| const struct nf_conntrack_l4proto nf_conntrack_l4proto_tcp = |
| { |
| .l4proto = IPPROTO_TCP, |
| #ifdef CONFIG_NF_CONNTRACK_PROCFS |
| .print_conntrack = tcp_print_conntrack, |
| #endif |
| .can_early_drop = tcp_can_early_drop, |
| #if IS_ENABLED(CONFIG_NF_CT_NETLINK) |
| .to_nlattr = tcp_to_nlattr, |
| .from_nlattr = nlattr_to_tcp, |
| .tuple_to_nlattr = nf_ct_port_tuple_to_nlattr, |
| .nlattr_to_tuple = nf_ct_port_nlattr_to_tuple, |
| .nlattr_tuple_size = tcp_nlattr_tuple_size, |
| .nlattr_size = TCP_NLATTR_SIZE, |
| .nla_policy = nf_ct_port_nla_policy, |
| #endif |
| #ifdef CONFIG_NF_CONNTRACK_TIMEOUT |
| .ctnl_timeout = { |
| .nlattr_to_obj = tcp_timeout_nlattr_to_obj, |
| .obj_to_nlattr = tcp_timeout_obj_to_nlattr, |
| .nlattr_max = CTA_TIMEOUT_TCP_MAX, |
| .obj_size = sizeof(unsigned int) * |
| TCP_CONNTRACK_TIMEOUT_MAX, |
| .nla_policy = tcp_timeout_nla_policy, |
| }, |
| #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */ |
| }; |