diff --git a/net/dccp/ccids/Kconfig b/net/dccp/ccids/Kconfig
index fb168be..1227594 100644
--- a/net/dccp/ccids/Kconfig
+++ b/net/dccp/ccids/Kconfig
@@ -1,8 +1,10 @@
 menu "DCCP CCIDs Configuration (EXPERIMENTAL)"
+	depends on EXPERIMENTAL
 
 config IP_DCCP_CCID2
-	tristate "CCID2 (TCP-Like)"
+	tristate "CCID2 (TCP-Like) (EXPERIMENTAL)"
 	def_tristate IP_DCCP
+	select IP_DCCP_ACKVEC
 	---help---
 	  CCID 2, TCP-like Congestion Control, denotes Additive Increase,
 	  Multiplicative Decrease (AIMD) congestion control with behavior
@@ -34,7 +36,7 @@
 	    If in doubt, say N.
 
 config IP_DCCP_CCID3
-	tristate "CCID3 (TCP-Friendly)"
+	tristate "CCID3 (TCP-Friendly) (EXPERIMENTAL)"
 	def_tristate IP_DCCP
 	select IP_DCCP_TFRC_LIB
 	---help---
@@ -62,9 +64,9 @@
 
 	  If in doubt, say M.
 
-if IP_DCCP_CCID3
 config IP_DCCP_CCID3_DEBUG
 	  bool "CCID3 debugging messages"
+	  depends on IP_DCCP_CCID3
 	  ---help---
 	    Enable CCID3-specific debugging messages.
 
@@ -74,29 +76,10 @@
 
 	    If in doubt, say N.
 
-choice
-	  prompt "Select method for measuring the packet size s"
-	  default IP_DCCP_CCID3_MEASURE_S_AS_MPS
-
-config IP_DCCP_CCID3_MEASURE_S_AS_MPS
-	  bool "Always use MPS in place of s"
-	  ---help---
-	    This use is recommended as it is consistent with the initialisation
-	    of X and suggested when s varies (rfc3448bis, (1) in section 4.1).
-config IP_DCCP_CCID3_MEASURE_S_AS_AVG
-	  bool "Use moving average"
-	  ---help---
-	    An alternative way of tracking s, also supported by rfc3448bis.
-	    This used to be the default for CCID-3 in previous kernels.
-config IP_DCCP_CCID3_MEASURE_S_AS_MAX
-	  bool "Track the maximum payload length"
-	  ---help---
-	    An experimental method based on tracking the maximum packet size.
-endchoice
-
 config IP_DCCP_CCID3_RTO
 	  int "Use higher bound for nofeedback timer"
 	  default 100
+	  depends on IP_DCCP_CCID3 && EXPERIMENTAL
 	  ---help---
 	    Use higher lower bound for nofeedback timer expiration.
 
@@ -123,7 +106,6 @@
 	    The purpose of the nofeedback timer is to slow DCCP down when there
 	    is serious network congestion: experimenting with larger values should
 	    therefore not be performed on WANs.
-endif	# IP_DCCP_CCID3
 
 config IP_DCCP_TFRC_LIB
 	tristate
diff --git a/net/dccp/ccids/ccid2.c b/net/dccp/ccids/ccid2.c
index fa71322..9a43073 100644
--- a/net/dccp/ccids/ccid2.c
+++ b/net/dccp/ccids/ccid2.c
@@ -25,7 +25,7 @@
 /*
  * This implementation should follow RFC 4341
  */
-#include "../feat.h"
+
 #include "../ccid.h"
 #include "../dccp.h"
 #include "ccid2.h"
@@ -34,8 +34,51 @@
 #ifdef CONFIG_IP_DCCP_CCID2_DEBUG
 static int ccid2_debug;
 #define ccid2_pr_debug(format, a...)	DCCP_PR_DEBUG(ccid2_debug, format, ##a)
+
+static void ccid2_hc_tx_check_sanity(const struct ccid2_hc_tx_sock *hctx)
+{
+	int len = 0;
+	int pipe = 0;
+	struct ccid2_seq *seqp = hctx->ccid2hctx_seqh;
+
+	/* there is data in the chain */
+	if (seqp != hctx->ccid2hctx_seqt) {
+		seqp = seqp->ccid2s_prev;
+		len++;
+		if (!seqp->ccid2s_acked)
+			pipe++;
+
+		while (seqp != hctx->ccid2hctx_seqt) {
+			struct ccid2_seq *prev = seqp->ccid2s_prev;
+
+			len++;
+			if (!prev->ccid2s_acked)
+				pipe++;
+
+			/* packets are sent sequentially */
+			BUG_ON(dccp_delta_seqno(seqp->ccid2s_seq,
+						prev->ccid2s_seq ) >= 0);
+			BUG_ON(time_before(seqp->ccid2s_sent,
+					   prev->ccid2s_sent));
+
+			seqp = prev;
+		}
+	}
+
+	BUG_ON(pipe != hctx->ccid2hctx_pipe);
+	ccid2_pr_debug("len of chain=%d\n", len);
+
+	do {
+		seqp = seqp->ccid2s_prev;
+		len++;
+	} while (seqp != hctx->ccid2hctx_seqh);
+
+	ccid2_pr_debug("total len=%d\n", len);
+	BUG_ON(len != hctx->ccid2hctx_seqbufc * CCID2_SEQBUF_LEN);
+}
 #else
 #define ccid2_pr_debug(format, a...)
+#define ccid2_hc_tx_check_sanity(hctx)
 #endif
 
 static int ccid2_hc_tx_alloc_seq(struct ccid2_hc_tx_sock *hctx)
@@ -44,7 +87,8 @@
 	int i;
 
 	/* check if we have space to preserve the pointer to the buffer */
-	if (hctx->seqbufc >= sizeof(hctx->seqbuf) / sizeof(struct ccid2_seq *))
+	if (hctx->ccid2hctx_seqbufc >= (sizeof(hctx->ccid2hctx_seqbuf) /
+					sizeof(struct ccid2_seq*)))
 		return -ENOMEM;
 
 	/* allocate buffer and initialize linked list */
@@ -60,35 +104,38 @@
 	seqp->ccid2s_prev = &seqp[CCID2_SEQBUF_LEN - 1];
 
 	/* This is the first allocation.  Initiate the head and tail.  */
-	if (hctx->seqbufc == 0)
-		hctx->seqh = hctx->seqt = seqp;
+	if (hctx->ccid2hctx_seqbufc == 0)
+		hctx->ccid2hctx_seqh = hctx->ccid2hctx_seqt = seqp;
 	else {
 		/* link the existing list with the one we just created */
-		hctx->seqh->ccid2s_next = seqp;
-		seqp->ccid2s_prev = hctx->seqh;
+		hctx->ccid2hctx_seqh->ccid2s_next = seqp;
+		seqp->ccid2s_prev = hctx->ccid2hctx_seqh;
 
-		hctx->seqt->ccid2s_prev = &seqp[CCID2_SEQBUF_LEN - 1];
-		seqp[CCID2_SEQBUF_LEN - 1].ccid2s_next = hctx->seqt;
+		hctx->ccid2hctx_seqt->ccid2s_prev = &seqp[CCID2_SEQBUF_LEN - 1];
+		seqp[CCID2_SEQBUF_LEN - 1].ccid2s_next = hctx->ccid2hctx_seqt;
 	}
 
 	/* store the original pointer to the buffer so we can free it */
-	hctx->seqbuf[hctx->seqbufc] = seqp;
-	hctx->seqbufc++;
+	hctx->ccid2hctx_seqbuf[hctx->ccid2hctx_seqbufc] = seqp;
+	hctx->ccid2hctx_seqbufc++;
 
 	return 0;
 }
 
 static int ccid2_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb)
 {
-	if (ccid2_cwnd_network_limited(ccid2_hc_tx_sk(sk)))
-		return CCID_PACKET_WILL_DEQUEUE_LATER;
-	return CCID_PACKET_SEND_AT_ONCE;
+	struct ccid2_hc_tx_sock *hctx = ccid2_hc_tx_sk(sk);
+
+	if (hctx->ccid2hctx_pipe < hctx->ccid2hctx_cwnd)
+		return 0;
+
+	return 1; /* XXX CCID should dequeue when ready instead of polling */
 }
 
 static void ccid2_change_l_ack_ratio(struct sock *sk, u32 val)
 {
 	struct dccp_sock *dp = dccp_sk(sk);
-	u32 max_ratio = DIV_ROUND_UP(ccid2_hc_tx_sk(sk)->cwnd, 2);
+	u32 max_ratio = DIV_ROUND_UP(ccid2_hc_tx_sk(sk)->ccid2hctx_cwnd, 2);
 
 	/*
 	 * Ensure that Ack Ratio does not exceed ceil(cwnd/2), which is (2) from
@@ -100,8 +147,8 @@
 		DCCP_WARN("Limiting Ack Ratio (%u) to %u\n", val, max_ratio);
 		val = max_ratio;
 	}
-	if (val > DCCPF_ACK_RATIO_MAX)
-		val = DCCPF_ACK_RATIO_MAX;
+	if (val > 0xFFFF)		/* RFC 4340, 11.3 */
+		val = 0xFFFF;
 
 	if (val == dp->dccps_l_ack_ratio)
 		return;
@@ -110,77 +157,99 @@
 	dp->dccps_l_ack_ratio = val;
 }
 
+static void ccid2_change_srtt(struct ccid2_hc_tx_sock *hctx, long val)
+{
+	ccid2_pr_debug("change SRTT to %ld\n", val);
+	hctx->ccid2hctx_srtt = val;
+}
+
+static void ccid2_start_rto_timer(struct sock *sk);
+
 static void ccid2_hc_tx_rto_expire(unsigned long data)
 {
 	struct sock *sk = (struct sock *)data;
 	struct ccid2_hc_tx_sock *hctx = ccid2_hc_tx_sk(sk);
-	const bool sender_was_blocked = ccid2_cwnd_network_limited(hctx);
+	long s;
 
 	bh_lock_sock(sk);
 	if (sock_owned_by_user(sk)) {
-		sk_reset_timer(sk, &hctx->rtotimer, jiffies + HZ / 5);
+		sk_reset_timer(sk, &hctx->ccid2hctx_rtotimer,
+			       jiffies + HZ / 5);
 		goto out;
 	}
 
 	ccid2_pr_debug("RTO_EXPIRE\n");
 
+	ccid2_hc_tx_check_sanity(hctx);
+
 	/* back-off timer */
-	hctx->rto <<= 1;
-	if (hctx->rto > DCCP_RTO_MAX)
-		hctx->rto = DCCP_RTO_MAX;
+	hctx->ccid2hctx_rto <<= 1;
+
+	s = hctx->ccid2hctx_rto / HZ;
+	if (s > 60)
+		hctx->ccid2hctx_rto = 60 * HZ;
+
+	ccid2_start_rto_timer(sk);
 
 	/* adjust pipe, cwnd etc */
-	hctx->ssthresh = hctx->cwnd / 2;
-	if (hctx->ssthresh < 2)
-		hctx->ssthresh = 2;
-	hctx->cwnd = 1;
-	hctx->pipe = 0;
+	hctx->ccid2hctx_ssthresh = hctx->ccid2hctx_cwnd / 2;
+	if (hctx->ccid2hctx_ssthresh < 2)
+		hctx->ccid2hctx_ssthresh = 2;
+	hctx->ccid2hctx_cwnd	 = 1;
+	hctx->ccid2hctx_pipe	 = 0;
 
 	/* clear state about stuff we sent */
-	hctx->seqt = hctx->seqh;
-	hctx->packets_acked = 0;
+	hctx->ccid2hctx_seqt = hctx->ccid2hctx_seqh;
+	hctx->ccid2hctx_packets_acked = 0;
 
 	/* clear ack ratio state. */
-	hctx->rpseq    = 0;
-	hctx->rpdupack = -1;
+	hctx->ccid2hctx_rpseq	 = 0;
+	hctx->ccid2hctx_rpdupack = -1;
 	ccid2_change_l_ack_ratio(sk, 1);
-
-	/* if we were blocked before, we may now send cwnd=1 packet */
-	if (sender_was_blocked)
-		tasklet_schedule(&dccp_sk(sk)->dccps_xmitlet);
-	/* restart backed-off timer */
-	sk_reset_timer(sk, &hctx->rtotimer, jiffies + hctx->rto);
+	ccid2_hc_tx_check_sanity(hctx);
 out:
 	bh_unlock_sock(sk);
 	sock_put(sk);
 }
 
-static void ccid2_hc_tx_packet_sent(struct sock *sk, unsigned int len)
+static void ccid2_start_rto_timer(struct sock *sk)
+{
+	struct ccid2_hc_tx_sock *hctx = ccid2_hc_tx_sk(sk);
+
+	ccid2_pr_debug("setting RTO timeout=%ld\n", hctx->ccid2hctx_rto);
+
+	BUG_ON(timer_pending(&hctx->ccid2hctx_rtotimer));
+	sk_reset_timer(sk, &hctx->ccid2hctx_rtotimer,
+		       jiffies + hctx->ccid2hctx_rto);
+}
+
+static void ccid2_hc_tx_packet_sent(struct sock *sk, int more, unsigned int len)
 {
 	struct dccp_sock *dp = dccp_sk(sk);
 	struct ccid2_hc_tx_sock *hctx = ccid2_hc_tx_sk(sk);
 	struct ccid2_seq *next;
 
-	hctx->pipe++;
+	hctx->ccid2hctx_pipe++;
 
-	hctx->seqh->ccid2s_seq   = dp->dccps_gss;
-	hctx->seqh->ccid2s_acked = 0;
-	hctx->seqh->ccid2s_sent  = jiffies;
+	hctx->ccid2hctx_seqh->ccid2s_seq   = dp->dccps_gss;
+	hctx->ccid2hctx_seqh->ccid2s_acked = 0;
+	hctx->ccid2hctx_seqh->ccid2s_sent  = jiffies;
 
-	next = hctx->seqh->ccid2s_next;
+	next = hctx->ccid2hctx_seqh->ccid2s_next;
 	/* check if we need to alloc more space */
-	if (next == hctx->seqt) {
+	if (next == hctx->ccid2hctx_seqt) {
 		if (ccid2_hc_tx_alloc_seq(hctx)) {
 			DCCP_CRIT("packet history - out of memory!");
 			/* FIXME: find a more graceful way to bail out */
 			return;
 		}
-		next = hctx->seqh->ccid2s_next;
-		BUG_ON(next == hctx->seqt);
+		next = hctx->ccid2hctx_seqh->ccid2s_next;
+		BUG_ON(next == hctx->ccid2hctx_seqt);
 	}
-	hctx->seqh = next;
+	hctx->ccid2hctx_seqh = next;
 
-	ccid2_pr_debug("cwnd=%d pipe=%d\n", hctx->cwnd, hctx->pipe);
+	ccid2_pr_debug("cwnd=%d pipe=%d\n", hctx->ccid2hctx_cwnd,
+		       hctx->ccid2hctx_pipe);
 
 	/*
 	 * FIXME: The code below is broken and the variables have been removed
@@ -203,12 +272,12 @@
 	 */
 #if 0
 	/* Ack Ratio.  Need to maintain a concept of how many windows we sent */
-	hctx->arsent++;
+	hctx->ccid2hctx_arsent++;
 	/* We had an ack loss in this window... */
-	if (hctx->ackloss) {
-		if (hctx->arsent >= hctx->cwnd) {
-			hctx->arsent  = 0;
-			hctx->ackloss = 0;
+	if (hctx->ccid2hctx_ackloss) {
+		if (hctx->ccid2hctx_arsent >= hctx->ccid2hctx_cwnd) {
+			hctx->ccid2hctx_arsent	= 0;
+			hctx->ccid2hctx_ackloss	= 0;
 		}
 	} else {
 		/* No acks lost up to now... */
@@ -218,28 +287,28 @@
 			int denom = dp->dccps_l_ack_ratio * dp->dccps_l_ack_ratio -
 				    dp->dccps_l_ack_ratio;
 
-			denom = hctx->cwnd * hctx->cwnd / denom;
+			denom = hctx->ccid2hctx_cwnd * hctx->ccid2hctx_cwnd / denom;
 
-			if (hctx->arsent >= denom) {
+			if (hctx->ccid2hctx_arsent >= denom) {
 				ccid2_change_l_ack_ratio(sk, dp->dccps_l_ack_ratio - 1);
-				hctx->arsent = 0;
+				hctx->ccid2hctx_arsent = 0;
 			}
 		} else {
 			/* we can't increase ack ratio further [1] */
-			hctx->arsent = 0; /* or maybe set it to cwnd*/
+			hctx->ccid2hctx_arsent = 0; /* or maybe set it to cwnd*/
 		}
 	}
 #endif
 
 	/* setup RTO timer */
-	if (!timer_pending(&hctx->rtotimer))
-		sk_reset_timer(sk, &hctx->rtotimer, jiffies + hctx->rto);
+	if (!timer_pending(&hctx->ccid2hctx_rtotimer))
+		ccid2_start_rto_timer(sk);
 
 #ifdef CONFIG_IP_DCCP_CCID2_DEBUG
 	do {
-		struct ccid2_seq *seqp = hctx->seqt;
+		struct ccid2_seq *seqp = hctx->ccid2hctx_seqt;
 
-		while (seqp != hctx->seqh) {
+		while (seqp != hctx->ccid2hctx_seqh) {
 			ccid2_pr_debug("out seq=%llu acked=%d time=%lu\n",
 				       (unsigned long long)seqp->ccid2s_seq,
 				       seqp->ccid2s_acked, seqp->ccid2s_sent);
@@ -247,158 +316,205 @@
 		}
 	} while (0);
 	ccid2_pr_debug("=========\n");
+	ccid2_hc_tx_check_sanity(hctx);
 #endif
 }
 
-/**
- * ccid2_rtt_estimator - Sample RTT and compute RTO using RFC2988 algorithm
- * This code is almost identical with TCP's tcp_rtt_estimator(), since
- * - it has a higher sampling frequency (recommended by RFC 1323),
- * - the RTO does not collapse into RTT due to RTTVAR going towards zero,
- * - it is simple (cf. more complex proposals such as Eifel timer or research
- *   which suggests that the gain should be set according to window size),
- * - in tests it was found to work well with CCID2 [gerrit].
+/* XXX Lame code duplication!
+ * returns -1 if none was found.
+ * else returns the next offset to use in the function call.
  */
-static void ccid2_rtt_estimator(struct sock *sk, const long mrtt)
+static int ccid2_ackvector(struct sock *sk, struct sk_buff *skb, int offset,
+			   unsigned char **vec, unsigned char *veclen)
 {
-	struct ccid2_hc_tx_sock *hctx = ccid2_hc_tx_sk(sk);
-	long m = mrtt ? : 1;
+	const struct dccp_hdr *dh = dccp_hdr(skb);
+	unsigned char *options = (unsigned char *)dh + dccp_hdr_len(skb);
+	unsigned char *opt_ptr;
+	const unsigned char *opt_end = (unsigned char *)dh +
+					(dh->dccph_doff * 4);
+	unsigned char opt, len;
+	unsigned char *value;
 
-	if (hctx->srtt == 0) {
-		/* First measurement m */
-		hctx->srtt = m << 3;
-		hctx->mdev = m << 1;
+	BUG_ON(offset < 0);
+	options += offset;
+	opt_ptr = options;
+	if (opt_ptr >= opt_end)
+		return -1;
 
-		hctx->mdev_max = max(TCP_RTO_MIN, hctx->mdev);
-		hctx->rttvar   = hctx->mdev_max;
-		hctx->rtt_seq  = dccp_sk(sk)->dccps_gss;
-	} else {
-		/* Update scaled SRTT as SRTT += 1/8 * (m - SRTT) */
-		m -= (hctx->srtt >> 3);
-		hctx->srtt += m;
+	while (opt_ptr != opt_end) {
+		opt   = *opt_ptr++;
+		len   = 0;
+		value = NULL;
 
-		/* Similarly, update scaled mdev with regard to |m| */
-		if (m < 0) {
-			m = -m;
-			m -= (hctx->mdev >> 2);
+		/* Check if this isn't a single byte option */
+		if (opt > DCCPO_MAX_RESERVED) {
+			if (opt_ptr == opt_end)
+				goto out_invalid_option;
+
+			len = *opt_ptr++;
+			if (len < 3)
+				goto out_invalid_option;
 			/*
-			 * This neutralises RTO increase when RTT < SRTT - mdev
-			 * (see P. Sarolahti, A. Kuznetsov,"Congestion Control
-			 * in Linux TCP", USENIX 2002, pp. 49-62).
+			 * Remove the type and len fields, leaving
+			 * just the value size
 			 */
-			if (m > 0)
-				m >>= 3;
-		} else {
-			m -= (hctx->mdev >> 2);
-		}
-		hctx->mdev += m;
+			len     -= 2;
+			value   = opt_ptr;
+			opt_ptr += len;
 
-		if (hctx->mdev > hctx->mdev_max) {
-			hctx->mdev_max = hctx->mdev;
-			if (hctx->mdev_max > hctx->rttvar)
-				hctx->rttvar = hctx->mdev_max;
+			if (opt_ptr > opt_end)
+				goto out_invalid_option;
 		}
 
-		/*
-		 * Decay RTTVAR at most once per flight, exploiting that
-		 *  1) pipe <= cwnd <= Sequence_Window = W  (RFC 4340, 7.5.2)
-		 *  2) AWL = GSS-W+1 <= GAR <= GSS          (RFC 4340, 7.5.1)
-		 * GAR is a useful bound for FlightSize = pipe, AWL is probably
-		 * too low as it over-estimates pipe.
-		 */
-		if (after48(dccp_sk(sk)->dccps_gar, hctx->rtt_seq)) {
-			if (hctx->mdev_max < hctx->rttvar)
-				hctx->rttvar -= (hctx->rttvar -
-						 hctx->mdev_max) >> 2;
-			hctx->rtt_seq  = dccp_sk(sk)->dccps_gss;
-			hctx->mdev_max = TCP_RTO_MIN;
+		switch (opt) {
+		case DCCPO_ACK_VECTOR_0:
+		case DCCPO_ACK_VECTOR_1:
+			*vec	= value;
+			*veclen = len;
+			return offset + (opt_ptr - options);
 		}
 	}
 
-	/*
-	 * Set RTO from SRTT and RTTVAR
-	 * Clock granularity is ignored since the minimum error for RTTVAR is
-	 * clamped to 50msec (corresponding to HZ=20). This leads to a minimum
-	 * RTO of 200msec. This agrees with TCP and RFC 4341, 5.: "Because DCCP
-	 * does not retransmit data, DCCP does not require TCP's recommended
-	 * minimum timeout of one second".
-	 */
-	hctx->rto = (hctx->srtt >> 3) + hctx->rttvar;
+	return -1;
 
-	if (hctx->rto > DCCP_RTO_MAX)
-		hctx->rto = DCCP_RTO_MAX;
+out_invalid_option:
+	DCCP_BUG("Invalid option - this should not happen (previous parsing)!");
+	return -1;
 }
 
-static void ccid2_new_ack(struct sock *sk, struct ccid2_seq *seqp,
-			  unsigned int *maxincr)
+static void ccid2_hc_tx_kill_rto_timer(struct sock *sk)
 {
 	struct ccid2_hc_tx_sock *hctx = ccid2_hc_tx_sk(sk);
 
-	if (hctx->cwnd < hctx->ssthresh) {
-		if (*maxincr > 0 && ++hctx->packets_acked == 2) {
-			hctx->cwnd += 1;
-			*maxincr   -= 1;
-			hctx->packets_acked = 0;
+	sk_stop_timer(sk, &hctx->ccid2hctx_rtotimer);
+	ccid2_pr_debug("deleted RTO timer\n");
+}
+
+static inline void ccid2_new_ack(struct sock *sk,
+				 struct ccid2_seq *seqp,
+				 unsigned int *maxincr)
+{
+	struct ccid2_hc_tx_sock *hctx = ccid2_hc_tx_sk(sk);
+
+	if (hctx->ccid2hctx_cwnd < hctx->ccid2hctx_ssthresh) {
+		if (*maxincr > 0 && ++hctx->ccid2hctx_packets_acked == 2) {
+			hctx->ccid2hctx_cwnd += 1;
+			*maxincr	     -= 1;
+			hctx->ccid2hctx_packets_acked = 0;
 		}
-	} else if (++hctx->packets_acked >= hctx->cwnd) {
-			hctx->cwnd += 1;
-			hctx->packets_acked = 0;
+	} else if (++hctx->ccid2hctx_packets_acked >= hctx->ccid2hctx_cwnd) {
+			hctx->ccid2hctx_cwnd += 1;
+			hctx->ccid2hctx_packets_acked = 0;
 	}
-	/*
-	 * FIXME: RTT is sampled several times per acknowledgment (for each
-	 * entry in the Ack Vector), instead of once per Ack (as in TCP SACK).
-	 * This causes the RTT to be over-estimated, since the older entries
-	 * in the Ack Vector have earlier sending times.
-	 * The cleanest solution is to not use the ccid2s_sent field at all
-	 * and instead use DCCP timestamps - need to be resolved at some time.
-	 */
-	ccid2_rtt_estimator(sk, jiffies - seqp->ccid2s_sent);
+
+	/* update RTO */
+	if (hctx->ccid2hctx_srtt == -1 ||
+	    time_after(jiffies, hctx->ccid2hctx_lastrtt + hctx->ccid2hctx_srtt)) {
+		unsigned long r = (long)jiffies - (long)seqp->ccid2s_sent;
+		int s;
+
+		/* first measurement */
+		if (hctx->ccid2hctx_srtt == -1) {
+			ccid2_pr_debug("R: %lu Time=%lu seq=%llu\n",
+				       r, jiffies,
+				       (unsigned long long)seqp->ccid2s_seq);
+			ccid2_change_srtt(hctx, r);
+			hctx->ccid2hctx_rttvar = r >> 1;
+		} else {
+			/* RTTVAR */
+			long tmp = hctx->ccid2hctx_srtt - r;
+			long srtt;
+
+			if (tmp < 0)
+				tmp *= -1;
+
+			tmp >>= 2;
+			hctx->ccid2hctx_rttvar *= 3;
+			hctx->ccid2hctx_rttvar >>= 2;
+			hctx->ccid2hctx_rttvar += tmp;
+
+			/* SRTT */
+			srtt = hctx->ccid2hctx_srtt;
+			srtt *= 7;
+			srtt >>= 3;
+			tmp = r >> 3;
+			srtt += tmp;
+			ccid2_change_srtt(hctx, srtt);
+		}
+		s = hctx->ccid2hctx_rttvar << 2;
+		/* clock granularity is 1 when based on jiffies */
+		if (!s)
+			s = 1;
+		hctx->ccid2hctx_rto = hctx->ccid2hctx_srtt + s;
+
+		/* must be at least a second */
+		s = hctx->ccid2hctx_rto / HZ;
+		/* DCCP doesn't require this [but I like it cuz my code sux] */
+#if 1
+		if (s < 1)
+			hctx->ccid2hctx_rto = HZ;
+#endif
+		/* max 60 seconds */
+		if (s > 60)
+			hctx->ccid2hctx_rto = HZ * 60;
+
+		hctx->ccid2hctx_lastrtt = jiffies;
+
+		ccid2_pr_debug("srtt: %ld rttvar: %ld rto: %ld (HZ=%d) R=%lu\n",
+			       hctx->ccid2hctx_srtt, hctx->ccid2hctx_rttvar,
+			       hctx->ccid2hctx_rto, HZ, r);
+	}
+
+	/* we got a new ack, so re-start RTO timer */
+	ccid2_hc_tx_kill_rto_timer(sk);
+	ccid2_start_rto_timer(sk);
+}
+
+static void ccid2_hc_tx_dec_pipe(struct sock *sk)
+{
+	struct ccid2_hc_tx_sock *hctx = ccid2_hc_tx_sk(sk);
+
+	if (hctx->ccid2hctx_pipe == 0)
+		DCCP_BUG("pipe == 0");
+	else
+		hctx->ccid2hctx_pipe--;
+
+	if (hctx->ccid2hctx_pipe == 0)
+		ccid2_hc_tx_kill_rto_timer(sk);
 }
 
 static void ccid2_congestion_event(struct sock *sk, struct ccid2_seq *seqp)
 {
 	struct ccid2_hc_tx_sock *hctx = ccid2_hc_tx_sk(sk);
 
-	if (time_before(seqp->ccid2s_sent, hctx->last_cong)) {
+	if (time_before(seqp->ccid2s_sent, hctx->ccid2hctx_last_cong)) {
 		ccid2_pr_debug("Multiple losses in an RTT---treating as one\n");
 		return;
 	}
 
-	hctx->last_cong = jiffies;
+	hctx->ccid2hctx_last_cong = jiffies;
 
-	hctx->cwnd     = hctx->cwnd / 2 ? : 1U;
-	hctx->ssthresh = max(hctx->cwnd, 2U);
+	hctx->ccid2hctx_cwnd     = hctx->ccid2hctx_cwnd / 2 ? : 1U;
+	hctx->ccid2hctx_ssthresh = max(hctx->ccid2hctx_cwnd, 2U);
 
 	/* Avoid spurious timeouts resulting from Ack Ratio > cwnd */
-	if (dccp_sk(sk)->dccps_l_ack_ratio > hctx->cwnd)
-		ccid2_change_l_ack_ratio(sk, hctx->cwnd);
-}
-
-static int ccid2_hc_tx_parse_options(struct sock *sk, u8 packet_type,
-				     u8 option, u8 *optval, u8 optlen)
-{
-	struct ccid2_hc_tx_sock *hctx = ccid2_hc_tx_sk(sk);
-
-	switch (option) {
-	case DCCPO_ACK_VECTOR_0:
-	case DCCPO_ACK_VECTOR_1:
-		return dccp_ackvec_parsed_add(&hctx->av_chunks, optval, optlen,
-					      option - DCCPO_ACK_VECTOR_0);
-	}
-	return 0;
+	if (dccp_sk(sk)->dccps_l_ack_ratio > hctx->ccid2hctx_cwnd)
+		ccid2_change_l_ack_ratio(sk, hctx->ccid2hctx_cwnd);
 }
 
 static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
 {
 	struct dccp_sock *dp = dccp_sk(sk);
 	struct ccid2_hc_tx_sock *hctx = ccid2_hc_tx_sk(sk);
-	const bool sender_was_blocked = ccid2_cwnd_network_limited(hctx);
-	struct dccp_ackvec_parsed *avp;
 	u64 ackno, seqno;
 	struct ccid2_seq *seqp;
+	unsigned char *vector;
+	unsigned char veclen;
+	int offset = 0;
 	int done = 0;
 	unsigned int maxincr = 0;
 
+	ccid2_hc_tx_check_sanity(hctx);
 	/* check reverse path congestion */
 	seqno = DCCP_SKB_CB(skb)->dccpd_seq;
 
@@ -407,21 +523,21 @@
 	 * -sorbo.
 	 */
 	/* need to bootstrap */
-	if (hctx->rpdupack == -1) {
-		hctx->rpdupack = 0;
-		hctx->rpseq = seqno;
+	if (hctx->ccid2hctx_rpdupack == -1) {
+		hctx->ccid2hctx_rpdupack = 0;
+		hctx->ccid2hctx_rpseq = seqno;
 	} else {
 		/* check if packet is consecutive */
-		if (dccp_delta_seqno(hctx->rpseq, seqno) == 1)
-			hctx->rpseq = seqno;
+		if (dccp_delta_seqno(hctx->ccid2hctx_rpseq, seqno) == 1)
+			hctx->ccid2hctx_rpseq = seqno;
 		/* it's a later packet */
-		else if (after48(seqno, hctx->rpseq)) {
-			hctx->rpdupack++;
+		else if (after48(seqno, hctx->ccid2hctx_rpseq)) {
+			hctx->ccid2hctx_rpdupack++;
 
 			/* check if we got enough dupacks */
-			if (hctx->rpdupack >= NUMDUPACK) {
-				hctx->rpdupack = -1; /* XXX lame */
-				hctx->rpseq = 0;
+			if (hctx->ccid2hctx_rpdupack >= NUMDUPACK) {
+				hctx->ccid2hctx_rpdupack = -1; /* XXX lame */
+				hctx->ccid2hctx_rpseq = 0;
 
 				ccid2_change_l_ack_ratio(sk, 2 * dp->dccps_l_ack_ratio);
 			}
@@ -429,22 +545,27 @@
 	}
 
 	/* check forward path congestion */
-	if (dccp_packet_without_ack(skb))
+	/* still didn't send out new data packets */
+	if (hctx->ccid2hctx_seqh == hctx->ccid2hctx_seqt)
 		return;
 
-	/* still didn't send out new data packets */
-	if (hctx->seqh == hctx->seqt)
-		goto done;
+	switch (DCCP_SKB_CB(skb)->dccpd_type) {
+	case DCCP_PKT_ACK:
+	case DCCP_PKT_DATAACK:
+		break;
+	default:
+		return;
+	}
 
 	ackno = DCCP_SKB_CB(skb)->dccpd_ack_seq;
-	if (after48(ackno, hctx->high_ack))
-		hctx->high_ack = ackno;
+	if (after48(ackno, hctx->ccid2hctx_high_ack))
+		hctx->ccid2hctx_high_ack = ackno;
 
-	seqp = hctx->seqt;
+	seqp = hctx->ccid2hctx_seqt;
 	while (before48(seqp->ccid2s_seq, ackno)) {
 		seqp = seqp->ccid2s_next;
-		if (seqp == hctx->seqh) {
-			seqp = hctx->seqh->ccid2s_prev;
+		if (seqp == hctx->ccid2hctx_seqh) {
+			seqp = hctx->ccid2hctx_seqh->ccid2s_prev;
 			break;
 		}
 	}
@@ -454,26 +575,26 @@
 	 * packets per acknowledgement. Rounding up avoids that cwnd is not
 	 * advanced when Ack Ratio is 1 and gives a slight edge otherwise.
 	 */
-	if (hctx->cwnd < hctx->ssthresh)
+	if (hctx->ccid2hctx_cwnd < hctx->ccid2hctx_ssthresh)
 		maxincr = DIV_ROUND_UP(dp->dccps_l_ack_ratio, 2);
 
 	/* go through all ack vectors */
-	list_for_each_entry(avp, &hctx->av_chunks, node) {
+	while ((offset = ccid2_ackvector(sk, skb, offset,
+					 &vector, &veclen)) != -1) {
 		/* go through this ack vector */
-		for (; avp->len--; avp->vec++) {
-			u64 ackno_end_rl = SUB48(ackno,
-						 dccp_ackvec_runlen(avp->vec));
+		while (veclen--) {
+			const u8 rl = *vector & DCCP_ACKVEC_LEN_MASK;
+			u64 ackno_end_rl = SUB48(ackno, rl);
 
-			ccid2_pr_debug("ackvec %llu |%u,%u|\n",
+			ccid2_pr_debug("ackvec start:%llu end:%llu\n",
 				       (unsigned long long)ackno,
-				       dccp_ackvec_state(avp->vec) >> 6,
-				       dccp_ackvec_runlen(avp->vec));
+				       (unsigned long long)ackno_end_rl);
 			/* if the seqno we are analyzing is larger than the
 			 * current ackno, then move towards the tail of our
 			 * seqnos.
 			 */
 			while (after48(seqp->ccid2s_seq, ackno)) {
-				if (seqp == hctx->seqt) {
+				if (seqp == hctx->ccid2hctx_seqt) {
 					done = 1;
 					break;
 				}
@@ -486,24 +607,26 @@
 			 * run length
 			 */
 			while (between48(seqp->ccid2s_seq,ackno_end_rl,ackno)) {
-				const u8 state = dccp_ackvec_state(avp->vec);
+				const u8 state = *vector &
+						 DCCP_ACKVEC_STATE_MASK;
 
 				/* new packet received or marked */
-				if (state != DCCPAV_NOT_RECEIVED &&
+				if (state != DCCP_ACKVEC_STATE_NOT_RECEIVED &&
 				    !seqp->ccid2s_acked) {
-					if (state == DCCPAV_ECN_MARKED)
+					if (state ==
+					    DCCP_ACKVEC_STATE_ECN_MARKED) {
 						ccid2_congestion_event(sk,
 								       seqp);
-					else
+					} else
 						ccid2_new_ack(sk, seqp,
 							      &maxincr);
 
 					seqp->ccid2s_acked = 1;
 					ccid2_pr_debug("Got ack for %llu\n",
 						       (unsigned long long)seqp->ccid2s_seq);
-					hctx->pipe--;
+					ccid2_hc_tx_dec_pipe(sk);
 				}
-				if (seqp == hctx->seqt) {
+				if (seqp == hctx->ccid2hctx_seqt) {
 					done = 1;
 					break;
 				}
@@ -513,6 +636,7 @@
 				break;
 
 			ackno = SUB48(ackno_end_rl, 1);
+			vector++;
 		}
 		if (done)
 			break;
@@ -521,11 +645,11 @@
 	/* The state about what is acked should be correct now
 	 * Check for NUMDUPACK
 	 */
-	seqp = hctx->seqt;
-	while (before48(seqp->ccid2s_seq, hctx->high_ack)) {
+	seqp = hctx->ccid2hctx_seqt;
+	while (before48(seqp->ccid2s_seq, hctx->ccid2hctx_high_ack)) {
 		seqp = seqp->ccid2s_next;
-		if (seqp == hctx->seqh) {
-			seqp = hctx->seqh->ccid2s_prev;
+		if (seqp == hctx->ccid2hctx_seqh) {
+			seqp = hctx->ccid2hctx_seqh->ccid2s_prev;
 			break;
 		}
 	}
@@ -536,7 +660,7 @@
 			if (done == NUMDUPACK)
 				break;
 		}
-		if (seqp == hctx->seqt)
+		if (seqp == hctx->ccid2hctx_seqt)
 			break;
 		seqp = seqp->ccid2s_prev;
 	}
@@ -557,34 +681,25 @@
 				 * one ack vector.
 				 */
 				ccid2_congestion_event(sk, seqp);
-				hctx->pipe--;
+				ccid2_hc_tx_dec_pipe(sk);
 			}
-			if (seqp == hctx->seqt)
+			if (seqp == hctx->ccid2hctx_seqt)
 				break;
 			seqp = seqp->ccid2s_prev;
 		}
 
-		hctx->seqt = last_acked;
+		hctx->ccid2hctx_seqt = last_acked;
 	}
 
 	/* trim acked packets in tail */
-	while (hctx->seqt != hctx->seqh) {
-		if (!hctx->seqt->ccid2s_acked)
+	while (hctx->ccid2hctx_seqt != hctx->ccid2hctx_seqh) {
+		if (!hctx->ccid2hctx_seqt->ccid2s_acked)
 			break;
 
-		hctx->seqt = hctx->seqt->ccid2s_next;
+		hctx->ccid2hctx_seqt = hctx->ccid2hctx_seqt->ccid2s_next;
 	}
 
-	/* restart RTO timer if not all outstanding data has been acked */
-	if (hctx->pipe == 0)
-		sk_stop_timer(sk, &hctx->rtotimer);
-	else
-		sk_reset_timer(sk, &hctx->rtotimer, jiffies + hctx->rto);
-done:
-	/* check if incoming Acks allow pending packets to be sent */
-	if (sender_was_blocked && !ccid2_cwnd_network_limited(hctx))
-		tasklet_schedule(&dccp_sk(sk)->dccps_xmitlet);
-	dccp_ackvec_parsed_cleanup(&hctx->av_chunks);
+	ccid2_hc_tx_check_sanity(hctx);
 }
 
 static int ccid2_hc_tx_init(struct ccid *ccid, struct sock *sk)
@@ -594,13 +709,17 @@
 	u32 max_ratio;
 
 	/* RFC 4341, 5: initialise ssthresh to arbitrarily high (max) value */
-	hctx->ssthresh = ~0U;
+	hctx->ccid2hctx_ssthresh  = ~0U;
 
-	/* Use larger initial windows (RFC 3390, rfc2581bis) */
-	hctx->cwnd = rfc3390_bytes_to_packets(dp->dccps_mss_cache);
+	/*
+	 * RFC 4341, 5: "The cwnd parameter is initialized to at most four
+	 * packets for new connections, following the rules from [RFC3390]".
+	 * We need to convert the bytes of RFC3390 into the packets of RFC 4341.
+	 */
+	hctx->ccid2hctx_cwnd = clamp(4380U / dp->dccps_mss_cache, 2U, 4U);
 
 	/* Make sure that Ack Ratio is enabled and within bounds. */
-	max_ratio = DIV_ROUND_UP(hctx->cwnd, 2);
+	max_ratio = DIV_ROUND_UP(hctx->ccid2hctx_cwnd, 2);
 	if (dp->dccps_l_ack_ratio == 0 || dp->dccps_l_ack_ratio > max_ratio)
 		dp->dccps_l_ack_ratio = max_ratio;
 
@@ -608,11 +727,15 @@
 	if (ccid2_hc_tx_alloc_seq(hctx))
 		return -ENOMEM;
 
-	hctx->rto	= DCCP_TIMEOUT_INIT;
-	hctx->rpdupack  = -1;
-	hctx->last_cong = jiffies;
-	setup_timer(&hctx->rtotimer, ccid2_hc_tx_rto_expire, (unsigned long)sk);
-	INIT_LIST_HEAD(&hctx->av_chunks);
+	hctx->ccid2hctx_rto	 = 3 * HZ;
+	ccid2_change_srtt(hctx, -1);
+	hctx->ccid2hctx_rttvar	 = -1;
+	hctx->ccid2hctx_rpdupack = -1;
+	hctx->ccid2hctx_last_cong = jiffies;
+	setup_timer(&hctx->ccid2hctx_rtotimer, ccid2_hc_tx_rto_expire,
+			(unsigned long)sk);
+
+	ccid2_hc_tx_check_sanity(hctx);
 	return 0;
 }
 
@@ -621,11 +744,11 @@
 	struct ccid2_hc_tx_sock *hctx = ccid2_hc_tx_sk(sk);
 	int i;
 
-	sk_stop_timer(sk, &hctx->rtotimer);
+	ccid2_hc_tx_kill_rto_timer(sk);
 
-	for (i = 0; i < hctx->seqbufc; i++)
-		kfree(hctx->seqbuf[i]);
-	hctx->seqbufc = 0;
+	for (i = 0; i < hctx->ccid2hctx_seqbufc; i++)
+		kfree(hctx->ccid2hctx_seqbuf[i]);
+	hctx->ccid2hctx_seqbufc = 0;
 }
 
 static void ccid2_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
@@ -636,28 +759,27 @@
 	switch (DCCP_SKB_CB(skb)->dccpd_type) {
 	case DCCP_PKT_DATA:
 	case DCCP_PKT_DATAACK:
-		hcrx->data++;
-		if (hcrx->data >= dp->dccps_r_ack_ratio) {
+		hcrx->ccid2hcrx_data++;
+		if (hcrx->ccid2hcrx_data >= dp->dccps_r_ack_ratio) {
 			dccp_send_ack(sk);
-			hcrx->data = 0;
+			hcrx->ccid2hcrx_data = 0;
 		}
 		break;
 	}
 }
 
 static struct ccid_operations ccid2 = {
-	.ccid_id		  = DCCPC_CCID2,
-	.ccid_name		  = "TCP-like",
-	.ccid_owner		  = THIS_MODULE,
-	.ccid_hc_tx_obj_size	  = sizeof(struct ccid2_hc_tx_sock),
-	.ccid_hc_tx_init	  = ccid2_hc_tx_init,
-	.ccid_hc_tx_exit	  = ccid2_hc_tx_exit,
-	.ccid_hc_tx_send_packet	  = ccid2_hc_tx_send_packet,
-	.ccid_hc_tx_packet_sent	  = ccid2_hc_tx_packet_sent,
-	.ccid_hc_tx_parse_options = ccid2_hc_tx_parse_options,
-	.ccid_hc_tx_packet_recv	  = ccid2_hc_tx_packet_recv,
-	.ccid_hc_rx_obj_size	  = sizeof(struct ccid2_hc_rx_sock),
-	.ccid_hc_rx_packet_recv	  = ccid2_hc_rx_packet_recv,
+	.ccid_id		= DCCPC_CCID2,
+	.ccid_name		= "TCP-like",
+	.ccid_owner		= THIS_MODULE,
+	.ccid_hc_tx_obj_size	= sizeof(struct ccid2_hc_tx_sock),
+	.ccid_hc_tx_init	= ccid2_hc_tx_init,
+	.ccid_hc_tx_exit	= ccid2_hc_tx_exit,
+	.ccid_hc_tx_send_packet	= ccid2_hc_tx_send_packet,
+	.ccid_hc_tx_packet_sent	= ccid2_hc_tx_packet_sent,
+	.ccid_hc_tx_packet_recv	= ccid2_hc_tx_packet_recv,
+	.ccid_hc_rx_obj_size	= sizeof(struct ccid2_hc_rx_sock),
+	.ccid_hc_rx_packet_recv	= ccid2_hc_rx_packet_recv,
 };
 
 #ifdef CONFIG_IP_DCCP_CCID2_DEBUG
diff --git a/net/dccp/ccids/ccid2.h b/net/dccp/ccids/ccid2.h
index 8b7a2de..2c94ca0 100644
--- a/net/dccp/ccids/ccid2.h
+++ b/net/dccp/ccids/ccid2.h
@@ -42,49 +42,34 @@
 
 /** struct ccid2_hc_tx_sock - CCID2 TX half connection
  *
- * @{cwnd,ssthresh,pipe}: as per RFC 4341, section 5
- * @packets_acked: Ack counter for deriving cwnd growth (RFC 3465)
- * @srtt: smoothed RTT estimate, scaled by 2^3
- * @mdev: smoothed RTT variation, scaled by 2^2
- * @mdev_max: maximum of @mdev during one flight
- * @rttvar: moving average/maximum of @mdev_max
- * @rto: RTO value deriving from SRTT and RTTVAR (RFC 2988)
- * @rtt_seq: to decay RTTVAR at most once per flight
- * @rpseq: last consecutive seqno
- * @rpdupack: dupacks since rpseq
- * @av_chunks: list of Ack Vectors received on current skb
- */
+ * @ccid2hctx_{cwnd,ssthresh,pipe}: as per RFC 4341, section 5
+ * @ccid2hctx_packets_acked - Ack counter for deriving cwnd growth (RFC 3465)
+ * @ccid2hctx_lastrtt -time RTT was last measured
+ * @ccid2hctx_rpseq - last consecutive seqno
+ * @ccid2hctx_rpdupack - dupacks since rpseq
+*/
 struct ccid2_hc_tx_sock {
-	u32			cwnd;
-	u32			ssthresh;
-	u32			pipe;
-	u32			packets_acked;
-	struct ccid2_seq	*seqbuf[CCID2_SEQBUF_MAX];
-	int			seqbufc;
-	struct ccid2_seq	*seqh;
-	struct ccid2_seq	*seqt;
-	/* RTT measurement: variables/principles are the same as in TCP */
-	u32			srtt,
-				mdev,
-				mdev_max,
-				rttvar,
-				rto;
-	u64			rtt_seq:48;
-	struct timer_list	rtotimer;
-	u64			rpseq;
-	int			rpdupack;
-	unsigned long		last_cong;
-	u64			high_ack;
-	struct list_head	av_chunks;
+	u32			ccid2hctx_cwnd;
+	u32			ccid2hctx_ssthresh;
+	u32			ccid2hctx_pipe;
+	u32			ccid2hctx_packets_acked;
+	struct ccid2_seq	*ccid2hctx_seqbuf[CCID2_SEQBUF_MAX];
+	int			ccid2hctx_seqbufc;
+	struct ccid2_seq	*ccid2hctx_seqh;
+	struct ccid2_seq	*ccid2hctx_seqt;
+	long			ccid2hctx_rto;
+	long			ccid2hctx_srtt;
+	long			ccid2hctx_rttvar;
+	unsigned long		ccid2hctx_lastrtt;
+	struct timer_list	ccid2hctx_rtotimer;
+	u64			ccid2hctx_rpseq;
+	int			ccid2hctx_rpdupack;
+	unsigned long		ccid2hctx_last_cong;
+	u64			ccid2hctx_high_ack;
 };
 
-static inline bool ccid2_cwnd_network_limited(struct ccid2_hc_tx_sock *hctx)
-{
-	return (hctx->pipe >= hctx->cwnd);
-}
-
 struct ccid2_hc_rx_sock {
-	int			data;
+	int	ccid2hcrx_data;
 };
 
 static inline struct ccid2_hc_tx_sock *ccid2_hc_tx_sk(const struct sock *sk)
diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index 06cfdad..3b8bd7c 100644
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -49,41 +49,75 @@
 /*
  *	Transmitter Half-Connection Routines
  */
-/* Oscillation Prevention/Reduction: recommended by rfc3448bis, on by default */
-static int do_osc_prev = true;
+#ifdef CONFIG_IP_DCCP_CCID3_DEBUG
+static const char *ccid3_tx_state_name(enum ccid3_hc_tx_states state)
+{
+	static char *ccid3_state_names[] = {
+	[TFRC_SSTATE_NO_SENT]  = "NO_SENT",
+	[TFRC_SSTATE_NO_FBACK] = "NO_FBACK",
+	[TFRC_SSTATE_FBACK]    = "FBACK",
+	[TFRC_SSTATE_TERM]     = "TERM",
+	};
+
+	return ccid3_state_names[state];
+}
+#endif
+
+static void ccid3_hc_tx_set_state(struct sock *sk,
+				  enum ccid3_hc_tx_states state)
+{
+	struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
+	enum ccid3_hc_tx_states oldstate = hctx->ccid3hctx_state;
+
+	ccid3_pr_debug("%s(%p) %-8.8s -> %s\n",
+		       dccp_role(sk), sk, ccid3_tx_state_name(oldstate),
+		       ccid3_tx_state_name(state));
+	WARN_ON(state == oldstate);
+	hctx->ccid3hctx_state = state;
+}
 
 /*
  * Compute the initial sending rate X_init in the manner of RFC 3390:
  *
- *	X_init  =  min(4 * MPS, max(2 * MPS, 4380 bytes)) / RTT
+ *	X_init  =  min(4 * s, max(2 * s, 4380 bytes)) / RTT
  *
+ * Note that RFC 3390 uses MSS, RFC 4342 refers to RFC 3390, and rfc3448bis
+ * (rev-02) clarifies the use of RFC 3390 with regard to the above formula.
  * For consistency with other parts of the code, X_init is scaled by 2^6.
  */
 static inline u64 rfc3390_initial_rate(struct sock *sk)
 {
-	const u32 mps = dccp_sk(sk)->dccps_mss_cache,
-	       w_init = clamp(4380U, 2 * mps, 4 * mps);
+	const struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
+	const __u32 w_init = clamp_t(__u32, 4380U,
+			2 * hctx->ccid3hctx_s, 4 * hctx->ccid3hctx_s);
 
-	return scaled_div(w_init << 6, ccid3_hc_tx_sk(sk)->rtt);
+	return scaled_div(w_init << 6, hctx->ccid3hctx_rtt);
 }
 
-/**
- * ccid3_update_send_interval  -  Calculate new t_ipi = s / X
- * This respects the granularity of X (64 * bytes/second) and enforces the
- * scaled minimum of s * 64 / t_mbi = `s' bytes/second as per RFC 3448/4342.
+/*
+ * Recalculate t_ipi and delta (should be called whenever X changes)
  */
 static void ccid3_update_send_interval(struct ccid3_hc_tx_sock *hctx)
 {
-	if (unlikely(hctx->x <= hctx->s))
-		hctx->x	= hctx->s;
-	hctx->t_ipi = scaled_div32(((u64)hctx->s) << 6, hctx->x);
+	/* Calculate new t_ipi = s / X_inst (X_inst is in 64 * bytes/second) */
+	hctx->ccid3hctx_t_ipi = scaled_div32(((u64)hctx->ccid3hctx_s) << 6,
+					     hctx->ccid3hctx_x);
+
+	/* Calculate new delta by delta = min(t_ipi / 2, t_gran / 2) */
+	hctx->ccid3hctx_delta = min_t(u32, hctx->ccid3hctx_t_ipi / 2,
+					   TFRC_OPSYS_HALF_TIME_GRAN);
+
+	ccid3_pr_debug("t_ipi=%u, delta=%u, s=%u, X=%u\n",
+		       hctx->ccid3hctx_t_ipi, hctx->ccid3hctx_delta,
+		       hctx->ccid3hctx_s, (unsigned)(hctx->ccid3hctx_x >> 6));
+
 }
 
 static u32 ccid3_hc_tx_idle_rtt(struct ccid3_hc_tx_sock *hctx, ktime_t now)
 {
-	u32 delta = ktime_us_delta(now, hctx->t_last_win_count);
+	u32 delta = ktime_us_delta(now, hctx->ccid3hctx_t_last_win_count);
 
-	return delta / hctx->rtt;
+	return delta / hctx->ccid3hctx_rtt;
 }
 
 /**
@@ -99,8 +133,8 @@
 static void ccid3_hc_tx_update_x(struct sock *sk, ktime_t *stamp)
 {
 	struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
-	u64 min_rate = 2 * hctx->x_recv;
-	const u64 old_x = hctx->x;
+	__u64 min_rate = 2 * hctx->ccid3hctx_x_recv;
+	const  __u64 old_x = hctx->ccid3hctx_x;
 	ktime_t now = stamp ? *stamp : ktime_get_real();
 
 	/*
@@ -111,44 +145,50 @@
 	 */
 	if (ccid3_hc_tx_idle_rtt(hctx, now) >= 2) {
 		min_rate = rfc3390_initial_rate(sk);
-		min_rate = max(min_rate, 2 * hctx->x_recv);
+		min_rate = max(min_rate, 2 * hctx->ccid3hctx_x_recv);
 	}
 
-	if (hctx->p > 0) {
+	if (hctx->ccid3hctx_p > 0) {
 
-		hctx->x = min(((u64)hctx->x_calc) << 6, min_rate);
+		hctx->ccid3hctx_x = min(((__u64)hctx->ccid3hctx_x_calc) << 6,
+					min_rate);
+		hctx->ccid3hctx_x = max(hctx->ccid3hctx_x,
+					(((__u64)hctx->ccid3hctx_s) << 6) /
+								TFRC_T_MBI);
 
-	} else if (ktime_us_delta(now, hctx->t_ld) - (s64)hctx->rtt >= 0) {
+	} else if (ktime_us_delta(now, hctx->ccid3hctx_t_ld)
+				- (s64)hctx->ccid3hctx_rtt >= 0) {
 
-		hctx->x = min(2 * hctx->x, min_rate);
-		hctx->x = max(hctx->x,
-			      scaled_div(((u64)hctx->s) << 6, hctx->rtt));
-		hctx->t_ld = now;
+		hctx->ccid3hctx_x = min(2 * hctx->ccid3hctx_x, min_rate);
+		hctx->ccid3hctx_x = max(hctx->ccid3hctx_x,
+			    scaled_div(((__u64)hctx->ccid3hctx_s) << 6,
+				       hctx->ccid3hctx_rtt));
+		hctx->ccid3hctx_t_ld = now;
 	}
 
-	if (hctx->x != old_x) {
+	if (hctx->ccid3hctx_x != old_x) {
 		ccid3_pr_debug("X_prev=%u, X_now=%u, X_calc=%u, "
 			       "X_recv=%u\n", (unsigned)(old_x >> 6),
-			       (unsigned)(hctx->x >> 6), hctx->x_calc,
-			       (unsigned)(hctx->x_recv >> 6));
+			       (unsigned)(hctx->ccid3hctx_x >> 6),
+			       hctx->ccid3hctx_x_calc,
+			       (unsigned)(hctx->ccid3hctx_x_recv >> 6));
 
 		ccid3_update_send_interval(hctx);
 	}
 }
 
 /*
- * ccid3_hc_tx_measure_packet_size  -  Measuring the packet size `s' (sec 4.1)
- * @new_len: DCCP payload size in bytes (not used by all methods)
+ *	Track the mean packet size `s' (cf. RFC 4342, 5.3 and  RFC 3448, 4.1)
+ *	@len: DCCP packet payload size in bytes
  */
-static u32 ccid3_hc_tx_measure_packet_size(struct sock *sk, const u16 new_len)
+static inline void ccid3_hc_tx_update_s(struct ccid3_hc_tx_sock *hctx, int len)
 {
-#if   defined(CONFIG_IP_DCCP_CCID3_MEASURE_S_AS_AVG)
-	return tfrc_ewma(ccid3_hc_tx_sk(sk)->s, new_len, 9);
-#elif defined(CONFIG_IP_DCCP_CCID3_MEASURE_S_AS_MAX)
-	return max(ccid3_hc_tx_sk(sk)->s, new_len);
-#else /* CONFIG_IP_DCCP_CCID3_MEASURE_S_AS_MPS	*/
-	return dccp_sk(sk)->dccps_mss_cache;
-#endif
+	const u16 old_s = hctx->ccid3hctx_s;
+
+	hctx->ccid3hctx_s = tfrc_ewma(hctx->ccid3hctx_s, len, 9);
+
+	if (hctx->ccid3hctx_s != old_s)
+		ccid3_update_send_interval(hctx);
 }
 
 /*
@@ -158,13 +198,13 @@
 static inline void ccid3_hc_tx_update_win_count(struct ccid3_hc_tx_sock *hctx,
 						ktime_t now)
 {
-	u32 delta = ktime_us_delta(now, hctx->t_last_win_count),
-	    quarter_rtts = (4 * delta) / hctx->rtt;
+	u32 delta = ktime_us_delta(now, hctx->ccid3hctx_t_last_win_count),
+	    quarter_rtts = (4 * delta) / hctx->ccid3hctx_rtt;
 
 	if (quarter_rtts > 0) {
-		hctx->t_last_win_count = now;
-		hctx->last_win_count  += min(quarter_rtts, 5U);
-		hctx->last_win_count  &= 0xF;		/* mod 16 */
+		hctx->ccid3hctx_t_last_win_count = now;
+		hctx->ccid3hctx_last_win_count  += min(quarter_rtts, 5U);
+		hctx->ccid3hctx_last_win_count	&= 0xF;		/* mod 16 */
 	}
 }
 
@@ -181,26 +221,25 @@
 		goto restart_timer;
 	}
 
-	ccid3_pr_debug("%s(%p) entry with%s feedback\n", dccp_role(sk), sk,
-		       hctx->feedback ? "" : "out");
+	ccid3_pr_debug("%s(%p, state=%s) - entry \n", dccp_role(sk), sk,
+		       ccid3_tx_state_name(hctx->ccid3hctx_state));
 
-	/* Ignore and do not restart after leaving the established state */
-	if ((1 << sk->sk_state) & ~(DCCPF_OPEN | DCCPF_PARTOPEN))
+	if (hctx->ccid3hctx_state == TFRC_SSTATE_FBACK)
+		ccid3_hc_tx_set_state(sk, TFRC_SSTATE_NO_FBACK);
+	else if (hctx->ccid3hctx_state != TFRC_SSTATE_NO_FBACK)
 		goto out;
 
-	/* Reset feedback state to "no feedback received" */
-	hctx->feedback = false;
-
 	/*
 	 * Determine new allowed sending rate X as per draft rfc3448bis-00, 4.4
-	 * RTO is 0 if and only if no feedback has been received yet.
 	 */
-	if (hctx->t_rto == 0 || hctx->p == 0) {
+	if (hctx->ccid3hctx_t_rto == 0 ||	/* no feedback received yet */
+	    hctx->ccid3hctx_p == 0) {
 
 		/* halve send rate directly */
-		hctx->x /= 2;
+		hctx->ccid3hctx_x = max(hctx->ccid3hctx_x / 2,
+					(((__u64)hctx->ccid3hctx_s) << 6) /
+								    TFRC_T_MBI);
 		ccid3_update_send_interval(hctx);
-
 	} else {
 		/*
 		 *  Modify the cached value of X_recv
@@ -212,41 +251,44 @@
 		 *
 		 *  Note that X_recv is scaled by 2^6 while X_calc is not
 		 */
-		BUG_ON(hctx->p && !hctx->x_calc);
+		BUG_ON(hctx->ccid3hctx_p && !hctx->ccid3hctx_x_calc);
 
-		if (hctx->x_calc > (hctx->x_recv >> 5))
-			hctx->x_recv /= 2;
+		if (hctx->ccid3hctx_x_calc > (hctx->ccid3hctx_x_recv >> 5))
+			hctx->ccid3hctx_x_recv =
+				max(hctx->ccid3hctx_x_recv / 2,
+				    (((__u64)hctx->ccid3hctx_s) << 6) /
+							      (2 * TFRC_T_MBI));
 		else {
-			hctx->x_recv = hctx->x_calc;
-			hctx->x_recv <<= 4;
+			hctx->ccid3hctx_x_recv = hctx->ccid3hctx_x_calc;
+			hctx->ccid3hctx_x_recv <<= 4;
 		}
 		ccid3_hc_tx_update_x(sk, NULL);
 	}
 	ccid3_pr_debug("Reduced X to %llu/64 bytes/sec\n",
-			(unsigned long long)hctx->x);
+			(unsigned long long)hctx->ccid3hctx_x);
 
 	/*
 	 * Set new timeout for the nofeedback timer.
 	 * See comments in packet_recv() regarding the value of t_RTO.
 	 */
-	if (unlikely(hctx->t_rto == 0))		/* no feedback received yet */
+	if (unlikely(hctx->ccid3hctx_t_rto == 0))	/* no feedback yet */
 		t_nfb = TFRC_INITIAL_TIMEOUT;
 	else
-		t_nfb = max(hctx->t_rto, 2 * hctx->t_ipi);
+		t_nfb = max(hctx->ccid3hctx_t_rto, 2 * hctx->ccid3hctx_t_ipi);
 
 restart_timer:
-	sk_reset_timer(sk, &hctx->no_feedback_timer,
+	sk_reset_timer(sk, &hctx->ccid3hctx_no_feedback_timer,
 			   jiffies + usecs_to_jiffies(t_nfb));
 out:
 	bh_unlock_sock(sk);
 	sock_put(sk);
 }
 
-/**
- * ccid3_hc_tx_send_packet  -  Delay-based dequeueing of TX packets
- * @skb: next packet candidate to send on @sk
- * This function uses the convention of ccid_packet_dequeue_eval() and
- * returns a millisecond-delay value between 0 and t_mbi = 64000 msec.
+/*
+ * returns
+ *   > 0: delay (in msecs) that should pass before actually sending
+ *   = 0: can send immediately
+ *   < 0: error condition; do not send packet
  */
 static int ccid3_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb)
 {
@@ -263,14 +305,18 @@
 	if (unlikely(skb->len == 0))
 		return -EBADMSG;
 
-	if (hctx->s == 0) {
-		sk_reset_timer(sk, &hctx->no_feedback_timer, (jiffies +
+	switch (hctx->ccid3hctx_state) {
+	case TFRC_SSTATE_NO_SENT:
+		sk_reset_timer(sk, &hctx->ccid3hctx_no_feedback_timer,
+			       (jiffies +
 				usecs_to_jiffies(TFRC_INITIAL_TIMEOUT)));
-		hctx->last_win_count   = 0;
-		hctx->t_last_win_count = now;
+		hctx->ccid3hctx_last_win_count	 = 0;
+		hctx->ccid3hctx_t_last_win_count = now;
 
 		/* Set t_0 for initial packet */
-		hctx->t_nom = now;
+		hctx->ccid3hctx_t_nom = now;
+
+		hctx->ccid3hctx_s = skb->len;
 
 		/*
 		 * Use initial RTT sample when available: recommended by erratum
@@ -279,9 +325,9 @@
 		 */
 		if (dp->dccps_syn_rtt) {
 			ccid3_pr_debug("SYN RTT = %uus\n", dp->dccps_syn_rtt);
-			hctx->rtt  = dp->dccps_syn_rtt;
-			hctx->x    = rfc3390_initial_rate(sk);
-			hctx->t_ld = now;
+			hctx->ccid3hctx_rtt  = dp->dccps_syn_rtt;
+			hctx->ccid3hctx_x    = rfc3390_initial_rate(sk);
+			hctx->ccid3hctx_t_ld = now;
 		} else {
 			/*
 			 * Sender does not have RTT sample:
@@ -289,20 +335,17 @@
 			 *   is needed in several parts (e.g.  window counter);
 			 * - set sending rate X_pps = 1pps as per RFC 3448, 4.2.
 			 */
-			hctx->rtt = DCCP_FALLBACK_RTT;
-			hctx->x	  = dp->dccps_mss_cache;
-			hctx->x <<= 6;
+			hctx->ccid3hctx_rtt = DCCP_FALLBACK_RTT;
+			hctx->ccid3hctx_x   = hctx->ccid3hctx_s;
+			hctx->ccid3hctx_x <<= 6;
 		}
-
-		/* Compute t_ipi = s / X */
-		hctx->s = ccid3_hc_tx_measure_packet_size(sk, skb->len);
 		ccid3_update_send_interval(hctx);
 
-		/* Seed value for Oscillation Prevention (sec. 4.5) */
-		hctx->r_sqmean = tfrc_scaled_sqrt(hctx->rtt);
-
-	} else {
-		delay = ktime_us_delta(hctx->t_nom, now);
+		ccid3_hc_tx_set_state(sk, TFRC_SSTATE_NO_FBACK);
+		break;
+	case TFRC_SSTATE_NO_FBACK:
+	case TFRC_SSTATE_FBACK:
+		delay = ktime_us_delta(hctx->ccid3hctx_t_nom, now);
 		ccid3_pr_debug("delay=%ld\n", (long)delay);
 		/*
 		 *	Scheduling of packet transmissions [RFC 3448, 4.6]
@@ -312,80 +355,99 @@
 		 * else
 		 *       // send the packet in (t_nom - t_now) milliseconds.
 		 */
-		if (delay >= TFRC_T_DELTA)
-			return (u32)delay / USEC_PER_MSEC;
+		if (delay - (s64)hctx->ccid3hctx_delta >= 1000)
+			return (u32)delay / 1000L;
 
 		ccid3_hc_tx_update_win_count(hctx, now);
+		break;
+	case TFRC_SSTATE_TERM:
+		DCCP_BUG("%s(%p) - Illegal state TERM", dccp_role(sk), sk);
+		return -EINVAL;
 	}
 
 	/* prepare to send now (add options etc.) */
 	dp->dccps_hc_tx_insert_options = 1;
-	DCCP_SKB_CB(skb)->dccpd_ccval  = hctx->last_win_count;
+	DCCP_SKB_CB(skb)->dccpd_ccval = hctx->ccid3hctx_last_win_count;
 
 	/* set the nominal send time for the next following packet */
-	hctx->t_nom = ktime_add_us(hctx->t_nom, hctx->t_ipi);
-	return CCID_PACKET_SEND_AT_ONCE;
+	hctx->ccid3hctx_t_nom = ktime_add_us(hctx->ccid3hctx_t_nom,
+					     hctx->ccid3hctx_t_ipi);
+	return 0;
 }
 
-static void ccid3_hc_tx_packet_sent(struct sock *sk, unsigned int len)
+static void ccid3_hc_tx_packet_sent(struct sock *sk, int more,
+				    unsigned int len)
 {
 	struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
 
-	/* Changes to s will become effective the next time X is computed */
-	hctx->s = ccid3_hc_tx_measure_packet_size(sk, len);
+	ccid3_hc_tx_update_s(hctx, len);
 
-	if (tfrc_tx_hist_add(&hctx->hist, dccp_sk(sk)->dccps_gss))
+	if (tfrc_tx_hist_add(&hctx->ccid3hctx_hist, dccp_sk(sk)->dccps_gss))
 		DCCP_CRIT("packet history - out of memory!");
 }
 
 static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
 {
 	struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
-	struct tfrc_tx_hist_entry *acked;
+	struct ccid3_options_received *opt_recv;
 	ktime_t now;
 	unsigned long t_nfb;
-	u32 r_sample;
+	u32 pinv, r_sample;
 
 	/* we are only interested in ACKs */
 	if (!(DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_ACK ||
 	      DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_DATAACK))
 		return;
-	/*
-	 * Locate the acknowledged packet in the TX history.
-	 *
-	 * Returning "entry not found" here can for instance happen when
-	 *  - the host has not sent out anything (e.g. a passive server),
-	 *  - the Ack is outdated (packet with higher Ack number was received),
-	 *  - it is a bogus Ack (for a packet not sent on this connection).
-	 */
-	acked = tfrc_tx_hist_find_entry(hctx->hist, dccp_hdr_ack_seq(skb));
-	if (acked == NULL)
+	/* ... and only in the established state */
+	if (hctx->ccid3hctx_state != TFRC_SSTATE_FBACK &&
+	    hctx->ccid3hctx_state != TFRC_SSTATE_NO_FBACK)
 		return;
-	/* For the sake of RTT sampling, ignore/remove all older entries */
-	tfrc_tx_hist_purge(&acked->next);
 
-	/* Update the moving average for the RTT estimate (RFC 3448, 4.3) */
-	now	  = ktime_get_real();
-	r_sample  = dccp_sample_rtt(sk, ktime_us_delta(now, acked->stamp));
-	hctx->rtt = tfrc_ewma(hctx->rtt, r_sample, 9);
+	opt_recv = &hctx->ccid3hctx_options_received;
+	now = ktime_get_real();
 
+	/* Estimate RTT from history if ACK number is valid */
+	r_sample = tfrc_tx_hist_rtt(hctx->ccid3hctx_hist,
+				    DCCP_SKB_CB(skb)->dccpd_ack_seq, now);
+	if (r_sample == 0) {
+		DCCP_WARN("%s(%p): %s with bogus ACK-%llu\n", dccp_role(sk), sk,
+			  dccp_packet_name(DCCP_SKB_CB(skb)->dccpd_type),
+			  (unsigned long long)DCCP_SKB_CB(skb)->dccpd_ack_seq);
+		return;
+	}
+
+	/* Update receive rate in units of 64 * bytes/second */
+	hctx->ccid3hctx_x_recv = opt_recv->ccid3or_receive_rate;
+	hctx->ccid3hctx_x_recv <<= 6;
+
+	/* Update loss event rate (which is scaled by 1e6) */
+	pinv = opt_recv->ccid3or_loss_event_rate;
+	if (pinv == ~0U || pinv == 0)	       /* see RFC 4342, 8.5   */
+		hctx->ccid3hctx_p = 0;
+	else				       /* can not exceed 100% */
+		hctx->ccid3hctx_p = scaled_div(1, pinv);
+	/*
+	 * Validate new RTT sample and update moving average
+	 */
+	r_sample = dccp_sample_rtt(sk, r_sample);
+	hctx->ccid3hctx_rtt = tfrc_ewma(hctx->ccid3hctx_rtt, r_sample, 9);
 	/*
 	 * Update allowed sending rate X as per draft rfc3448bis-00, 4.2/3
 	 */
-	if (!hctx->feedback) {
-		hctx->feedback = true;
+	if (hctx->ccid3hctx_state == TFRC_SSTATE_NO_FBACK) {
+		ccid3_hc_tx_set_state(sk, TFRC_SSTATE_FBACK);
 
-		if (hctx->t_rto == 0) {
+		if (hctx->ccid3hctx_t_rto == 0) {
 			/*
 			 * Initial feedback packet: Larger Initial Windows (4.2)
 			 */
-			hctx->x    = rfc3390_initial_rate(sk);
-			hctx->t_ld = now;
+			hctx->ccid3hctx_x    = rfc3390_initial_rate(sk);
+			hctx->ccid3hctx_t_ld = now;
 
 			ccid3_update_send_interval(hctx);
 
 			goto done_computing_x;
-		} else if (hctx->p == 0) {
+		} else if (hctx->ccid3hctx_p == 0) {
 			/*
 			 * First feedback after nofeedback timer expiry (4.3)
 			 */
@@ -394,52 +456,25 @@
 	}
 
 	/* Update sending rate (step 4 of [RFC 3448, 4.3]) */
-	if (hctx->p > 0)
-		hctx->x_calc = tfrc_calc_x(hctx->s, hctx->rtt, hctx->p);
+	if (hctx->ccid3hctx_p > 0)
+		hctx->ccid3hctx_x_calc =
+				tfrc_calc_x(hctx->ccid3hctx_s,
+					    hctx->ccid3hctx_rtt,
+					    hctx->ccid3hctx_p);
 	ccid3_hc_tx_update_x(sk, &now);
 
 done_computing_x:
 	ccid3_pr_debug("%s(%p), RTT=%uus (sample=%uus), s=%u, "
 			       "p=%u, X_calc=%u, X_recv=%u, X=%u\n",
-			       dccp_role(sk), sk, hctx->rtt, r_sample,
-			       hctx->s, hctx->p, hctx->x_calc,
-			       (unsigned)(hctx->x_recv >> 6),
-			       (unsigned)(hctx->x >> 6));
-	/*
-	 * Oscillation Reduction (RFC 3448, 4.5) - modifying t_ipi according to
-	 * RTT changes, multiplying by X/X_inst = sqrt(R_sample)/R_sqmean. This
-	 * can be useful if few connections share a link, avoiding that buffer
-	 * fill levels (RTT) oscillate as a result of frequent adjustments to X.
-	 * A useful presentation with background information is in
-	 *    Joerg Widmer, "Equation-Based Congestion Control",
-	 *    MSc Thesis, University of Mannheim, Germany, 2000
-	 * (sec. 3.6.4), who calls this ISM ("Inter-packet Space Modulation").
-	 */
-	if (do_osc_prev) {
-		r_sample = tfrc_scaled_sqrt(r_sample);
-		/*
-		 * The modulation can work in both ways: increase/decrease t_ipi
-		 * according to long-term increases/decreases of the RTT. The
-		 * former is a useful measure, since it works against queue
-		 * build-up. The latter temporarily increases the sending rate,
-		 * so that buffers fill up more quickly. This in turn causes
-		 * the RTT to increase, so that either later reduction becomes
-		 * necessary or the RTT stays at a very high level. Decreasing
-		 * t_ipi is therefore not supported.
-		 * Furthermore, during the initial slow-start phase the RTT
-		 * naturally increases, where using the algorithm would cause
-		 * delays. Hence it is disabled during the initial slow-start.
-		 */
-		if (r_sample > hctx->r_sqmean && hctx->p > 0)
-			hctx->t_ipi = div_u64((u64)hctx->t_ipi * (u64)r_sample,
-					      hctx->r_sqmean);
-		hctx->t_ipi = min_t(u32, hctx->t_ipi, TFRC_T_MBI);
-		/* update R_sqmean _after_ computing the modulation factor */
-		hctx->r_sqmean = tfrc_ewma(hctx->r_sqmean, r_sample, 9);
-	}
+			       dccp_role(sk),
+			       sk, hctx->ccid3hctx_rtt, r_sample,
+			       hctx->ccid3hctx_s, hctx->ccid3hctx_p,
+			       hctx->ccid3hctx_x_calc,
+			       (unsigned)(hctx->ccid3hctx_x_recv >> 6),
+			       (unsigned)(hctx->ccid3hctx_x >> 6));
 
 	/* unschedule no feedback timer */
-	sk_stop_timer(sk, &hctx->no_feedback_timer);
+	sk_stop_timer(sk, &hctx->ccid3hctx_no_feedback_timer);
 
 	/*
 	 * As we have calculated new ipi, delta, t_nom it is possible
@@ -453,66 +488,95 @@
 	 * This can help avoid triggering the nofeedback timer too
 	 * often ('spinning') on LANs with small RTTs.
 	 */
-	hctx->t_rto = max_t(u32, 4 * hctx->rtt, (CONFIG_IP_DCCP_CCID3_RTO *
-						 (USEC_PER_SEC / 1000)));
+	hctx->ccid3hctx_t_rto = max_t(u32, 4 * hctx->ccid3hctx_rtt,
+					   (CONFIG_IP_DCCP_CCID3_RTO *
+					    (USEC_PER_SEC / 1000)));
 	/*
 	 * Schedule no feedback timer to expire in
 	 * max(t_RTO, 2 * s/X)  =  max(t_RTO, 2 * t_ipi)
 	 */
-	t_nfb = max(hctx->t_rto, 2 * hctx->t_ipi);
+	t_nfb = max(hctx->ccid3hctx_t_rto, 2 * hctx->ccid3hctx_t_ipi);
 
 	ccid3_pr_debug("%s(%p), Scheduled no feedback timer to "
 		       "expire in %lu jiffies (%luus)\n",
-		       dccp_role(sk), sk, usecs_to_jiffies(t_nfb), t_nfb);
+		       dccp_role(sk),
+		       sk, usecs_to_jiffies(t_nfb), t_nfb);
 
-	sk_reset_timer(sk, &hctx->no_feedback_timer,
+	sk_reset_timer(sk, &hctx->ccid3hctx_no_feedback_timer,
 			   jiffies + usecs_to_jiffies(t_nfb));
 }
 
-static int ccid3_hc_tx_parse_options(struct sock *sk, u8 packet_type,
-				     u8 option, u8 *optval, u8 optlen)
+static int ccid3_hc_tx_parse_options(struct sock *sk, unsigned char option,
+				     unsigned char len, u16 idx,
+				     unsigned char *value)
 {
+	int rc = 0;
+	const struct dccp_sock *dp = dccp_sk(sk);
 	struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
+	struct ccid3_options_received *opt_recv;
 	__be32 opt_val;
 
-	switch (option) {
-	case TFRC_OPT_RECEIVE_RATE:
-	case TFRC_OPT_LOSS_EVENT_RATE:
-		/* Must be ignored on Data packets, cf. RFC 4342 8.3 and 8.5 */
-		if (packet_type == DCCP_PKT_DATA)
-			break;
-		if (unlikely(optlen != 4)) {
-			DCCP_WARN("%s(%p), invalid len %d for %u\n",
-				  dccp_role(sk), sk, optlen, option);
-			return -EINVAL;
-		}
-		opt_val = ntohl(get_unaligned((__be32 *)optval));
+	opt_recv = &hctx->ccid3hctx_options_received;
 
-		if (option == TFRC_OPT_RECEIVE_RATE) {
-			/* Receive Rate is kept in units of 64 bytes/second */
-			hctx->x_recv = opt_val;
-			hctx->x_recv <<= 6;
-
-			ccid3_pr_debug("%s(%p), RECEIVE_RATE=%u\n",
-				       dccp_role(sk), sk, opt_val);
-		} else {
-			/* Update the fixpoint Loss Event Rate fraction */
-			hctx->p = tfrc_invert_loss_event_rate(opt_val);
-
-			ccid3_pr_debug("%s(%p), LOSS_EVENT_RATE=%u\n",
-				       dccp_role(sk), sk, opt_val);
-		}
+	if (opt_recv->ccid3or_seqno != dp->dccps_gsr) {
+		opt_recv->ccid3or_seqno		     = dp->dccps_gsr;
+		opt_recv->ccid3or_loss_event_rate    = ~0;
+		opt_recv->ccid3or_loss_intervals_idx = 0;
+		opt_recv->ccid3or_loss_intervals_len = 0;
+		opt_recv->ccid3or_receive_rate	     = 0;
 	}
-	return 0;
+
+	switch (option) {
+	case TFRC_OPT_LOSS_EVENT_RATE:
+		if (unlikely(len != 4)) {
+			DCCP_WARN("%s(%p), invalid len %d "
+				  "for TFRC_OPT_LOSS_EVENT_RATE\n",
+				  dccp_role(sk), sk, len);
+			rc = -EINVAL;
+		} else {
+			opt_val = get_unaligned((__be32 *)value);
+			opt_recv->ccid3or_loss_event_rate = ntohl(opt_val);
+			ccid3_pr_debug("%s(%p), LOSS_EVENT_RATE=%u\n",
+				       dccp_role(sk), sk,
+				       opt_recv->ccid3or_loss_event_rate);
+		}
+		break;
+	case TFRC_OPT_LOSS_INTERVALS:
+		opt_recv->ccid3or_loss_intervals_idx = idx;
+		opt_recv->ccid3or_loss_intervals_len = len;
+		ccid3_pr_debug("%s(%p), LOSS_INTERVALS=(%u, %u)\n",
+			       dccp_role(sk), sk,
+			       opt_recv->ccid3or_loss_intervals_idx,
+			       opt_recv->ccid3or_loss_intervals_len);
+		break;
+	case TFRC_OPT_RECEIVE_RATE:
+		if (unlikely(len != 4)) {
+			DCCP_WARN("%s(%p), invalid len %d "
+				  "for TFRC_OPT_RECEIVE_RATE\n",
+				  dccp_role(sk), sk, len);
+			rc = -EINVAL;
+		} else {
+			opt_val = get_unaligned((__be32 *)value);
+			opt_recv->ccid3or_receive_rate = ntohl(opt_val);
+			ccid3_pr_debug("%s(%p), RECEIVE_RATE=%u\n",
+				       dccp_role(sk), sk,
+				       opt_recv->ccid3or_receive_rate);
+		}
+		break;
+	}
+
+	return rc;
 }
 
 static int ccid3_hc_tx_init(struct ccid *ccid, struct sock *sk)
 {
 	struct ccid3_hc_tx_sock *hctx = ccid_priv(ccid);
 
-	hctx->hist  = NULL;
-	setup_timer(&hctx->no_feedback_timer,
-		    ccid3_hc_tx_no_feedback_timer, (unsigned long)sk);
+	hctx->ccid3hctx_state = TFRC_SSTATE_NO_SENT;
+	hctx->ccid3hctx_hist = NULL;
+	setup_timer(&hctx->ccid3hctx_no_feedback_timer,
+			ccid3_hc_tx_no_feedback_timer, (unsigned long)sk);
+
 	return 0;
 }
 
@@ -520,36 +584,42 @@
 {
 	struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
 
-	sk_stop_timer(sk, &hctx->no_feedback_timer);
-	tfrc_tx_hist_purge(&hctx->hist);
+	ccid3_hc_tx_set_state(sk, TFRC_SSTATE_TERM);
+	sk_stop_timer(sk, &hctx->ccid3hctx_no_feedback_timer);
+
+	tfrc_tx_hist_purge(&hctx->ccid3hctx_hist);
 }
 
 static void ccid3_hc_tx_get_info(struct sock *sk, struct tcp_info *info)
 {
-	info->tcpi_rto = ccid3_hc_tx_sk(sk)->t_rto;
-	info->tcpi_rtt = ccid3_hc_tx_sk(sk)->rtt;
+	struct ccid3_hc_tx_sock *hctx;
+
+	/* Listen socks doesn't have a private CCID block */
+	if (sk->sk_state == DCCP_LISTEN)
+		return;
+
+	hctx = ccid3_hc_tx_sk(sk);
+	info->tcpi_rto = hctx->ccid3hctx_t_rto;
+	info->tcpi_rtt = hctx->ccid3hctx_rtt;
 }
 
 static int ccid3_hc_tx_getsockopt(struct sock *sk, const int optname, int len,
 				  u32 __user *optval, int __user *optlen)
 {
-	const struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
-	struct tfrc_tx_info tfrc;
+	const struct ccid3_hc_tx_sock *hctx;
 	const void *val;
 
+	/* Listen socks doesn't have a private CCID block */
+	if (sk->sk_state == DCCP_LISTEN)
+		return -EINVAL;
+
+	hctx = ccid3_hc_tx_sk(sk);
 	switch (optname) {
 	case DCCP_SOCKOPT_CCID_TX_INFO:
-		if (len < sizeof(tfrc))
+		if (len < sizeof(hctx->ccid3hctx_tfrc))
 			return -EINVAL;
-		tfrc.tfrctx_x	   = hctx->x;
-		tfrc.tfrctx_x_recv = hctx->x_recv;
-		tfrc.tfrctx_x_calc = hctx->x_calc;
-		tfrc.tfrctx_rtt	   = hctx->rtt;
-		tfrc.tfrctx_p	   = hctx->p;
-		tfrc.tfrctx_rto	   = hctx->t_rto;
-		tfrc.tfrctx_ipi	   = hctx->t_ipi;
-		len = sizeof(tfrc);
-		val = &tfrc;
+		len = sizeof(hctx->ccid3hctx_tfrc);
+		val = &hctx->ccid3hctx_tfrc;
 		break;
 	default:
 		return -ENOPROTOOPT;
@@ -564,82 +634,112 @@
 /*
  *	Receiver Half-Connection Routines
  */
+
+/* CCID3 feedback types */
+enum ccid3_fback_type {
+	CCID3_FBACK_NONE = 0,
+	CCID3_FBACK_INITIAL,
+	CCID3_FBACK_PERIODIC,
+	CCID3_FBACK_PARAM_CHANGE
+};
+
+#ifdef CONFIG_IP_DCCP_CCID3_DEBUG
+static const char *ccid3_rx_state_name(enum ccid3_hc_rx_states state)
+{
+	static char *ccid3_rx_state_names[] = {
+	[TFRC_RSTATE_NO_DATA] = "NO_DATA",
+	[TFRC_RSTATE_DATA]    = "DATA",
+	[TFRC_RSTATE_TERM]    = "TERM",
+	};
+
+	return ccid3_rx_state_names[state];
+}
+#endif
+
+static void ccid3_hc_rx_set_state(struct sock *sk,
+				  enum ccid3_hc_rx_states state)
+{
+	struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
+	enum ccid3_hc_rx_states oldstate = hcrx->ccid3hcrx_state;
+
+	ccid3_pr_debug("%s(%p) %-8.8s -> %s\n",
+		       dccp_role(sk), sk, ccid3_rx_state_name(oldstate),
+		       ccid3_rx_state_name(state));
+	WARN_ON(state == oldstate);
+	hcrx->ccid3hcrx_state = state;
+}
+
 static void ccid3_hc_rx_send_feedback(struct sock *sk,
 				      const struct sk_buff *skb,
 				      enum ccid3_fback_type fbtype)
 {
 	struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
+	struct dccp_sock *dp = dccp_sk(sk);
+	ktime_t now;
+	s64 delta = 0;
+
+	if (unlikely(hcrx->ccid3hcrx_state == TFRC_RSTATE_TERM))
+		return;
+
+	now = ktime_get_real();
 
 	switch (fbtype) {
 	case CCID3_FBACK_INITIAL:
-		hcrx->x_recv = 0;
-		hcrx->p_inverse = ~0U;   /* see RFC 4342, 8.5 */
+		hcrx->ccid3hcrx_x_recv = 0;
+		hcrx->ccid3hcrx_pinv   = ~0U;   /* see RFC 4342, 8.5 */
 		break;
 	case CCID3_FBACK_PARAM_CHANGE:
-		if (unlikely(hcrx->feedback == CCID3_FBACK_NONE)) {
-			/*
-			 * rfc3448bis-06, 6.3.1: First packet(s) lost or marked
-			 * FIXME: in rfc3448bis the receiver returns X_recv=0
-			 * here as it normally would in the first feedback packet.
-			 * However this is not possible yet, since the code still
-			 * uses RFC 3448, i.e.
-			 *    If (p > 0)
-			 *      Calculate X_calc using the TCP throughput equation.
-			 *      X = max(min(X_calc, 2*X_recv), s/t_mbi);
-			 * would bring X down to s/t_mbi. That is why we return
-			 * X_recv according to rfc3448bis-06 for the moment.
-			 */
-			u32 s = tfrc_rx_hist_packet_size(&hcrx->hist),
-			    rtt = tfrc_rx_hist_rtt(&hcrx->hist);
-
-			hcrx->x_recv = scaled_div32(s, 2 * rtt);
-			break;
-		}
 		/*
 		 * When parameters change (new loss or p > p_prev), we do not
 		 * have a reliable estimate for R_m of [RFC 3448, 6.2] and so
-		 * always check whether at least RTT time units were covered.
+		 * need to  reuse the previous value of X_recv. However, when
+		 * X_recv was 0 (due to early loss), this would kill X down to
+		 * s/t_mbi (i.e. one packet in 64 seconds).
+		 * To avoid such drastic reduction, we approximate X_recv as
+		 * the number of bytes since last feedback.
+		 * This is a safe fallback, since X is bounded above by X_calc.
 		 */
-		hcrx->x_recv = tfrc_rx_hist_x_recv(&hcrx->hist, hcrx->x_recv);
-		break;
+		if (hcrx->ccid3hcrx_x_recv > 0)
+			break;
+		/* fall through */
 	case CCID3_FBACK_PERIODIC:
-		/*
-		 * Step (2) of rfc3448bis-06, 6.2:
-		 * - if no data packets have been received, just restart timer
-		 * - if data packets have been received, re-compute X_recv
-		 */
-		if (hcrx->hist.bytes_recvd == 0)
-			goto prepare_for_next_time;
-		hcrx->x_recv = tfrc_rx_hist_x_recv(&hcrx->hist, hcrx->x_recv);
+		delta = ktime_us_delta(now, hcrx->ccid3hcrx_tstamp_last_feedback);
+		if (delta <= 0)
+			DCCP_BUG("delta (%ld) <= 0", (long)delta);
+		else
+			hcrx->ccid3hcrx_x_recv =
+				scaled_div32(hcrx->ccid3hcrx_bytes_recv, delta);
 		break;
 	default:
 		return;
 	}
 
-	ccid3_pr_debug("X_recv=%u, 1/p=%u\n", hcrx->x_recv, hcrx->p_inverse);
+	ccid3_pr_debug("Interval %ldusec, X_recv=%u, 1/p=%u\n", (long)delta,
+		       hcrx->ccid3hcrx_x_recv, hcrx->ccid3hcrx_pinv);
 
-	dccp_sk(sk)->dccps_hc_rx_insert_options = 1;
+	hcrx->ccid3hcrx_tstamp_last_feedback = now;
+	hcrx->ccid3hcrx_last_counter	     = dccp_hdr(skb)->dccph_ccval;
+	hcrx->ccid3hcrx_bytes_recv	     = 0;
+
+	dp->dccps_hc_rx_insert_options = 1;
 	dccp_send_ack(sk);
-
-prepare_for_next_time:
-	tfrc_rx_hist_restart_byte_counter(&hcrx->hist);
-	hcrx->last_counter = dccp_hdr(skb)->dccph_ccval;
-	hcrx->feedback	   = fbtype;
 }
 
 static int ccid3_hc_rx_insert_options(struct sock *sk, struct sk_buff *skb)
 {
-	const struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
+	const struct ccid3_hc_rx_sock *hcrx;
 	__be32 x_recv, pinv;
 
 	if (!(sk->sk_state == DCCP_OPEN || sk->sk_state == DCCP_PARTOPEN))
 		return 0;
 
+	hcrx = ccid3_hc_rx_sk(sk);
+
 	if (dccp_packet_without_ack(skb))
 		return 0;
 
-	x_recv = htonl(hcrx->x_recv);
-	pinv   = htonl(hcrx->p_inverse);
+	x_recv = htonl(hcrx->ccid3hcrx_x_recv);
+	pinv   = htonl(hcrx->ccid3hcrx_pinv);
 
 	if (dccp_insert_option(sk, skb, TFRC_OPT_LOSS_EVENT_RATE,
 			       &pinv, sizeof(pinv)) ||
@@ -662,95 +762,171 @@
 static u32 ccid3_first_li(struct sock *sk)
 {
 	struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
-	u32 s = tfrc_rx_hist_packet_size(&hcrx->hist),
-	    rtt = tfrc_rx_hist_rtt(&hcrx->hist), x_recv, p;
+	u32 x_recv, p, delta;
 	u64 fval;
 
-	/*
-	 * rfc3448bis-06, 6.3.1: First data packet(s) are marked or lost. Set p
-	 * to give the equivalent of X_target = s/(2*R). Thus fval = 2 and so p
-	 * is about 20.64%. This yields an interval length of 4.84 (rounded up).
-	 */
-	if (unlikely(hcrx->feedback == CCID3_FBACK_NONE))
-		return 5;
+	if (hcrx->ccid3hcrx_rtt == 0) {
+		DCCP_WARN("No RTT estimate available, using fallback RTT\n");
+		hcrx->ccid3hcrx_rtt = DCCP_FALLBACK_RTT;
+	}
 
-	x_recv = tfrc_rx_hist_x_recv(&hcrx->hist, hcrx->x_recv);
-	if (x_recv == 0)
-		goto failed;
+	delta = ktime_to_us(net_timedelta(hcrx->ccid3hcrx_tstamp_last_feedback));
+	x_recv = scaled_div32(hcrx->ccid3hcrx_bytes_recv, delta);
+	if (x_recv == 0) {		/* would also trigger divide-by-zero */
+		DCCP_WARN("X_recv==0\n");
+		if ((x_recv = hcrx->ccid3hcrx_x_recv) == 0) {
+			DCCP_BUG("stored value of X_recv is zero");
+			return ~0U;
+		}
+	}
 
-	fval = scaled_div32(scaled_div(s, rtt), x_recv);
+	fval = scaled_div(hcrx->ccid3hcrx_s, hcrx->ccid3hcrx_rtt);
+	fval = scaled_div32(fval, x_recv);
 	p = tfrc_calc_x_reverse_lookup(fval);
 
 	ccid3_pr_debug("%s(%p), receive rate=%u bytes/s, implied "
 		       "loss rate=%u\n", dccp_role(sk), sk, x_recv, p);
 
-	if (p > 0)
-		return scaled_div(1, p);
-failed:
-	return UINT_MAX;
+	return p == 0 ? ~0U : scaled_div(1, p);
 }
 
 static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
 {
 	struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
+	enum ccid3_fback_type do_feedback = CCID3_FBACK_NONE;
 	const u64 ndp = dccp_sk(sk)->dccps_options_received.dccpor_ndp;
 	const bool is_data_packet = dccp_data_packet(skb);
 
+	if (unlikely(hcrx->ccid3hcrx_state == TFRC_RSTATE_NO_DATA)) {
+		if (is_data_packet) {
+			const u32 payload = skb->len - dccp_hdr(skb)->dccph_doff * 4;
+			do_feedback = CCID3_FBACK_INITIAL;
+			ccid3_hc_rx_set_state(sk, TFRC_RSTATE_DATA);
+			hcrx->ccid3hcrx_s = payload;
+			/*
+			 * Not necessary to update ccid3hcrx_bytes_recv here,
+			 * since X_recv = 0 for the first feedback packet (cf.
+			 * RFC 3448, 6.3) -- gerrit
+			 */
+		}
+		goto update_records;
+	}
+
+	if (tfrc_rx_hist_duplicate(&hcrx->ccid3hcrx_hist, skb))
+		return; /* done receiving */
+
+	if (is_data_packet) {
+		const u32 payload = skb->len - dccp_hdr(skb)->dccph_doff * 4;
+		/*
+		 * Update moving-average of s and the sum of received payload bytes
+		 */
+		hcrx->ccid3hcrx_s = tfrc_ewma(hcrx->ccid3hcrx_s, payload, 9);
+		hcrx->ccid3hcrx_bytes_recv += payload;
+	}
+
 	/*
 	 * Perform loss detection and handle pending losses
 	 */
-	if (tfrc_rx_congestion_event(&hcrx->hist, &hcrx->li_hist,
-				     skb, ndp, ccid3_first_li, sk))
-		ccid3_hc_rx_send_feedback(sk, skb, CCID3_FBACK_PARAM_CHANGE);
+	if (tfrc_rx_handle_loss(&hcrx->ccid3hcrx_hist, &hcrx->ccid3hcrx_li_hist,
+				skb, ndp, ccid3_first_li, sk)) {
+		do_feedback = CCID3_FBACK_PARAM_CHANGE;
+		goto done_receiving;
+	}
+
+	if (tfrc_rx_hist_loss_pending(&hcrx->ccid3hcrx_hist))
+		return; /* done receiving */
+
 	/*
-	 * Feedback for first non-empty data packet (RFC 3448, 6.3)
+	 * Handle data packets: RTT sampling and monitoring p
 	 */
-	else if (unlikely(hcrx->feedback == CCID3_FBACK_NONE && is_data_packet))
-		ccid3_hc_rx_send_feedback(sk, skb, CCID3_FBACK_INITIAL);
+	if (unlikely(!is_data_packet))
+		goto update_records;
+
+	if (!tfrc_lh_is_initialised(&hcrx->ccid3hcrx_li_hist)) {
+		const u32 sample = tfrc_rx_hist_sample_rtt(&hcrx->ccid3hcrx_hist, skb);
+		/*
+		 * Empty loss history: no loss so far, hence p stays 0.
+		 * Sample RTT values, since an RTT estimate is required for the
+		 * computation of p when the first loss occurs; RFC 3448, 6.3.1.
+		 */
+		if (sample != 0)
+			hcrx->ccid3hcrx_rtt = tfrc_ewma(hcrx->ccid3hcrx_rtt, sample, 9);
+
+	} else if (tfrc_lh_update_i_mean(&hcrx->ccid3hcrx_li_hist, skb)) {
+		/*
+		 * Step (3) of [RFC 3448, 6.1]: Recompute I_mean and, if I_mean
+		 * has decreased (resp. p has increased), send feedback now.
+		 */
+		do_feedback = CCID3_FBACK_PARAM_CHANGE;
+	}
+
 	/*
 	 * Check if the periodic once-per-RTT feedback is due; RFC 4342, 10.3
 	 */
-	else if (!tfrc_rx_hist_loss_pending(&hcrx->hist) && is_data_packet &&
-		 SUB16(dccp_hdr(skb)->dccph_ccval, hcrx->last_counter) > 3)
-		ccid3_hc_rx_send_feedback(sk, skb, CCID3_FBACK_PERIODIC);
+	if (SUB16(dccp_hdr(skb)->dccph_ccval, hcrx->ccid3hcrx_last_counter) > 3)
+		do_feedback = CCID3_FBACK_PERIODIC;
+
+update_records:
+	tfrc_rx_hist_add_packet(&hcrx->ccid3hcrx_hist, skb, ndp);
+
+done_receiving:
+	if (do_feedback)
+		ccid3_hc_rx_send_feedback(sk, skb, do_feedback);
 }
 
 static int ccid3_hc_rx_init(struct ccid *ccid, struct sock *sk)
 {
 	struct ccid3_hc_rx_sock *hcrx = ccid_priv(ccid);
 
-	tfrc_lh_init(&hcrx->li_hist);
-	return tfrc_rx_hist_init(&hcrx->hist, sk);
+	hcrx->ccid3hcrx_state = TFRC_RSTATE_NO_DATA;
+	tfrc_lh_init(&hcrx->ccid3hcrx_li_hist);
+	return tfrc_rx_hist_alloc(&hcrx->ccid3hcrx_hist);
 }
 
 static void ccid3_hc_rx_exit(struct sock *sk)
 {
 	struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
 
-	tfrc_rx_hist_purge(&hcrx->hist);
-	tfrc_lh_cleanup(&hcrx->li_hist);
+	ccid3_hc_rx_set_state(sk, TFRC_RSTATE_TERM);
+
+	tfrc_rx_hist_purge(&hcrx->ccid3hcrx_hist);
+	tfrc_lh_cleanup(&hcrx->ccid3hcrx_li_hist);
 }
 
 static void ccid3_hc_rx_get_info(struct sock *sk, struct tcp_info *info)
 {
+	const struct ccid3_hc_rx_sock *hcrx;
+
+	/* Listen socks doesn't have a private CCID block */
+	if (sk->sk_state == DCCP_LISTEN)
+		return;
+
+	hcrx = ccid3_hc_rx_sk(sk);
+	info->tcpi_ca_state = hcrx->ccid3hcrx_state;
 	info->tcpi_options  |= TCPI_OPT_TIMESTAMPS;
-	info->tcpi_rcv_rtt  = tfrc_rx_hist_rtt(&ccid3_hc_rx_sk(sk)->hist);
+	info->tcpi_rcv_rtt  = hcrx->ccid3hcrx_rtt;
 }
 
 static int ccid3_hc_rx_getsockopt(struct sock *sk, const int optname, int len,
 				  u32 __user *optval, int __user *optlen)
 {
-	const struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
+	const struct ccid3_hc_rx_sock *hcrx;
 	struct tfrc_rx_info rx_info;
 	const void *val;
 
+	/* Listen socks doesn't have a private CCID block */
+	if (sk->sk_state == DCCP_LISTEN)
+		return -EINVAL;
+
+	hcrx = ccid3_hc_rx_sk(sk);
 	switch (optname) {
 	case DCCP_SOCKOPT_CCID_RX_INFO:
 		if (len < sizeof(rx_info))
 			return -EINVAL;
-		rx_info.tfrcrx_x_recv = hcrx->x_recv;
-		rx_info.tfrcrx_rtt    = tfrc_rx_hist_rtt(&hcrx->hist);
-		rx_info.tfrcrx_p      = tfrc_invert_loss_event_rate(hcrx->p_inverse);
+		rx_info.tfrcrx_x_recv = hcrx->ccid3hcrx_x_recv;
+		rx_info.tfrcrx_rtt    = hcrx->ccid3hcrx_rtt;
+		rx_info.tfrcrx_p      = hcrx->ccid3hcrx_pinv == 0 ? ~0U :
+					   scaled_div(1, hcrx->ccid3hcrx_pinv);
 		len = sizeof(rx_info);
 		val = &rx_info;
 		break;
@@ -786,9 +962,6 @@
 	.ccid_hc_tx_getsockopt	   = ccid3_hc_tx_getsockopt,
 };
 
-module_param(do_osc_prev, bool, 0644);
-MODULE_PARM_DESC(do_osc_prev, "Use Oscillation Prevention (RFC 3448, 4.5)");
-
 #ifdef CONFIG_IP_DCCP_CCID3_DEBUG
 module_param(ccid3_debug, bool, 0644);
 MODULE_PARM_DESC(ccid3_debug, "Enable debug messages");
@@ -796,19 +969,6 @@
 
 static __init int ccid3_module_init(void)
 {
-	struct timespec tp;
-
-	/*
-	 * Without a fine-grained clock resolution, RTTs/X_recv are not sampled
-	 * correctly and feedback is sent either too early or too late.
-	 */
-	hrtimer_get_res(CLOCK_MONOTONIC, &tp);
-	if (tp.tv_sec || tp.tv_nsec > DCCP_TIME_RESOLUTION * NSEC_PER_USEC) {
-		printk(KERN_ERR "%s: Timer too coarse (%ld usec), need %u-usec"
-		       " resolution - check your clocksource.\n", __func__,
-		       tp.tv_nsec/NSEC_PER_USEC, DCCP_TIME_RESOLUTION);
-		return -ESOCKTNOSUPPORT;
-	}
 	return ccid_register(&ccid3);
 }
 module_init(ccid3_module_init);
diff --git a/net/dccp/ccids/ccid3.h b/net/dccp/ccids/ccid3.h
index af6e1bf..49ca32b 100644
--- a/net/dccp/ccids/ccid3.h
+++ b/net/dccp/ccids/ccid3.h
@@ -47,22 +47,11 @@
 /* Two seconds as per RFC 3448 4.2 */
 #define TFRC_INITIAL_TIMEOUT	   (2 * USEC_PER_SEC)
 
-/* Maximum backoff interval t_mbi (RFC 3448, 4.3) */
-#define TFRC_T_MBI		   (64 * USEC_PER_SEC)
+/* In usecs - half the scheduling granularity as per RFC3448 4.6 */
+#define TFRC_OPSYS_HALF_TIME_GRAN  (USEC_PER_SEC / (2 * HZ))
 
-/*
- * The t_delta parameter (RFC 3448, 4.6): delays of less than %USEC_PER_MSEC are
- * rounded down to 0, since sk_reset_timer() here uses millisecond granularity.
- * Hence we can use a constant t_delta = %USEC_PER_MSEC when HZ >= 500. A coarse
- * resolution of HZ < 500 means that the error is below one timer tick (t_gran)
- * when using the constant t_delta  =  t_gran / 2  =  %USEC_PER_SEC / (2 * HZ).
- */
-#if (HZ >= 500)
-# define TFRC_T_DELTA		   USEC_PER_MSEC
-#else
-# define TFRC_T_DELTA		   (USEC_PER_SEC / (2 * HZ))
-#warning Coarse CONFIG_HZ resolution -- higher value recommended for TFRC.
-#endif
+/* Parameter t_mbi from [RFC 3448, 4.3]: backoff interval in seconds */
+#define TFRC_T_MBI		   64
 
 enum ccid3_options {
 	TFRC_OPT_LOSS_EVENT_RATE = 192,
@@ -70,43 +59,62 @@
 	TFRC_OPT_RECEIVE_RATE	 = 194,
 };
 
+struct ccid3_options_received {
+	u64 ccid3or_seqno:48,
+	    ccid3or_loss_intervals_idx:16;
+	u16 ccid3or_loss_intervals_len;
+	u32 ccid3or_loss_event_rate;
+	u32 ccid3or_receive_rate;
+};
+
+/* TFRC sender states */
+enum ccid3_hc_tx_states {
+	TFRC_SSTATE_NO_SENT = 1,
+	TFRC_SSTATE_NO_FBACK,
+	TFRC_SSTATE_FBACK,
+	TFRC_SSTATE_TERM,
+};
+
 /** struct ccid3_hc_tx_sock - CCID3 sender half-connection socket
  *
- * @x - Current sending rate in 64 * bytes per second
- * @x_recv - Receive rate    in 64 * bytes per second
- * @x_calc - Calculated rate in bytes per second
- * @rtt - Estimate of current round trip time in usecs
- * @r_sqmean - Estimate of long-term RTT (RFC 3448, 4.5)
- * @p - Current loss event rate (0-1) scaled by 1000000
- * @s - Packet size in bytes
- * @t_rto - Nofeedback Timer setting in usecs
- * @t_ipi - Interpacket (send) interval (RFC 3448, 4.6) in usecs
- * @feedback - Whether feedback has been received or not
- * @last_win_count - Last window counter sent
- * @t_last_win_count - Timestamp of earliest packet with
- *                     last_win_count value sent
- * @no_feedback_timer - Handle to no feedback timer
- * @t_ld - Time last doubled during slow start
- * @t_nom - Nominal send time of next packet
- * @hist - Packet history
+ * @ccid3hctx_x - Current sending rate in 64 * bytes per second
+ * @ccid3hctx_x_recv - Receive rate    in 64 * bytes per second
+ * @ccid3hctx_x_calc - Calculated rate in bytes per second
+ * @ccid3hctx_rtt - Estimate of current round trip time in usecs
+ * @ccid3hctx_p - Current loss event rate (0-1) scaled by 1000000
+ * @ccid3hctx_s - Packet size in bytes
+ * @ccid3hctx_t_rto - Nofeedback Timer setting in usecs
+ * @ccid3hctx_t_ipi - Interpacket (send) interval (RFC 3448, 4.6) in usecs
+ * @ccid3hctx_state - Sender state, one of %ccid3_hc_tx_states
+ * @ccid3hctx_last_win_count - Last window counter sent
+ * @ccid3hctx_t_last_win_count - Timestamp of earliest packet
+ *				 with last_win_count value sent
+ * @ccid3hctx_no_feedback_timer - Handle to no feedback timer
+ * @ccid3hctx_t_ld - Time last doubled during slow start
+ * @ccid3hctx_t_nom - Nominal send time of next packet
+ * @ccid3hctx_delta - Send timer delta (RFC 3448, 4.6) in usecs
+ * @ccid3hctx_hist - Packet history
+ * @ccid3hctx_options_received - Parsed set of retrieved options
  */
 struct ccid3_hc_tx_sock {
-	u64				x;
-	u64				x_recv;
-	u32				x_calc;
-	u32				rtt;
-	u16				r_sqmean;
-	u32				p;
-	u32				t_rto;
-	u32				t_ipi;
-	u16				s;
-	bool				feedback:1;
-	u8				last_win_count;
-	ktime_t				t_last_win_count;
-	struct timer_list		no_feedback_timer;
-	ktime_t				t_ld;
-	ktime_t				t_nom;
-	struct tfrc_tx_hist_entry	*hist;
+	struct tfrc_tx_info		ccid3hctx_tfrc;
+#define ccid3hctx_x			ccid3hctx_tfrc.tfrctx_x
+#define ccid3hctx_x_recv		ccid3hctx_tfrc.tfrctx_x_recv
+#define ccid3hctx_x_calc		ccid3hctx_tfrc.tfrctx_x_calc
+#define ccid3hctx_rtt			ccid3hctx_tfrc.tfrctx_rtt
+#define ccid3hctx_p			ccid3hctx_tfrc.tfrctx_p
+#define ccid3hctx_t_rto			ccid3hctx_tfrc.tfrctx_rto
+#define ccid3hctx_t_ipi			ccid3hctx_tfrc.tfrctx_ipi
+	u16				ccid3hctx_s;
+	enum ccid3_hc_tx_states		ccid3hctx_state:8;
+	u8				ccid3hctx_last_win_count;
+	ktime_t				ccid3hctx_t_last_win_count;
+	struct timer_list		ccid3hctx_no_feedback_timer;
+	ktime_t				ccid3hctx_t_ld;
+	ktime_t				ccid3hctx_t_nom;
+	u32				ccid3hctx_delta;
+	struct tfrc_tx_hist_entry	*ccid3hctx_hist;
+	struct ccid3_options_received	ccid3hctx_options_received;
 };
 
 static inline struct ccid3_hc_tx_sock *ccid3_hc_tx_sk(const struct sock *sk)
@@ -116,32 +124,41 @@
     return hctx;
 }
 
-
-enum ccid3_fback_type {
-	CCID3_FBACK_NONE = 0,
-	CCID3_FBACK_INITIAL,
-	CCID3_FBACK_PERIODIC,
-	CCID3_FBACK_PARAM_CHANGE
+/* TFRC receiver states */
+enum ccid3_hc_rx_states {
+	TFRC_RSTATE_NO_DATA = 1,
+	TFRC_RSTATE_DATA,
+	TFRC_RSTATE_TERM    = 127,
 };
 
 /** struct ccid3_hc_rx_sock - CCID3 receiver half-connection socket
  *
- *  @last_counter  -  Tracks window counter (RFC 4342, 8.1)
- *  @feedback  -  The type of the feedback last sent
- *  @x_recv  -  Receiver estimate of send rate (RFC 3448, sec. 4.3)
- *  @tstamp_last_feedback  -  Time at which last feedback was sent
- *  @hist  -  Packet history (loss detection + RTT sampling)
- *  @li_hist  -  Loss Interval database
- *  @p_inverse  -  Inverse of Loss Event Rate (RFC 4342, sec. 8.5)
+ *  @ccid3hcrx_x_recv  -  Receiver estimate of send rate (RFC 3448 4.3)
+ *  @ccid3hcrx_rtt  -  Receiver estimate of rtt (non-standard)
+ *  @ccid3hcrx_p  -  Current loss event rate (RFC 3448 5.4)
+ *  @ccid3hcrx_last_counter  -  Tracks window counter (RFC 4342, 8.1)
+ *  @ccid3hcrx_state  -  Receiver state, one of %ccid3_hc_rx_states
+ *  @ccid3hcrx_bytes_recv  -  Total sum of DCCP payload bytes
+ *  @ccid3hcrx_x_recv  -  Receiver estimate of send rate (RFC 3448, sec. 4.3)
+ *  @ccid3hcrx_rtt  -  Receiver estimate of RTT
+ *  @ccid3hcrx_tstamp_last_feedback  -  Time at which last feedback was sent
+ *  @ccid3hcrx_tstamp_last_ack  -  Time at which last feedback was sent
+ *  @ccid3hcrx_hist  -  Packet history (loss detection + RTT sampling)
+ *  @ccid3hcrx_li_hist  -  Loss Interval database
+ *  @ccid3hcrx_s  -  Received packet size in bytes
+ *  @ccid3hcrx_pinv  -  Inverse of Loss Event Rate (RFC 4342, sec. 8.5)
  */
 struct ccid3_hc_rx_sock {
-	u8				last_counter:4;
-	enum ccid3_fback_type		feedback:4;
-	u32				x_recv;
-	ktime_t				tstamp_last_feedback;
-	struct tfrc_rx_hist		hist;
-	struct tfrc_loss_hist		li_hist;
-#define p_inverse			li_hist.i_mean
+	u8				ccid3hcrx_last_counter:4;
+	enum ccid3_hc_rx_states		ccid3hcrx_state:8;
+	u32				ccid3hcrx_bytes_recv;
+	u32				ccid3hcrx_x_recv;
+	u32				ccid3hcrx_rtt;
+	ktime_t				ccid3hcrx_tstamp_last_feedback;
+	struct tfrc_rx_hist		ccid3hcrx_hist;
+	struct tfrc_loss_hist		ccid3hcrx_li_hist;
+	u16				ccid3hcrx_s;
+#define ccid3hcrx_pinv			ccid3hcrx_li_hist.i_mean
 };
 
 static inline struct ccid3_hc_rx_sock *ccid3_hc_rx_sk(const struct sock *sk)
diff --git a/net/dccp/ccids/lib/loss_interval.c b/net/dccp/ccids/lib/loss_interval.c
index b1ae8f8..5b3ce06 100644
--- a/net/dccp/ccids/lib/loss_interval.c
+++ b/net/dccp/ccids/lib/loss_interval.c
@@ -86,26 +86,21 @@
 
 /**
  * tfrc_lh_update_i_mean  -  Update the `open' loss interval I_0
- * This updates I_mean as the sequence numbers increase. As a consequence, the
- * open loss interval I_0 increases, hence p = W_tot/max(I_tot0, I_tot1)
- * decreases, and thus there is no need to send renewed feedback.
+ * For recomputing p: returns `true' if p > p_prev  <=>  1/p < 1/p_prev
  */
-void tfrc_lh_update_i_mean(struct tfrc_loss_hist *lh, struct sk_buff *skb)
+u8 tfrc_lh_update_i_mean(struct tfrc_loss_hist *lh, struct sk_buff *skb)
 {
 	struct tfrc_loss_interval *cur = tfrc_lh_peek(lh);
+	u32 old_i_mean = lh->i_mean;
 	s64 len;
 
 	if (cur == NULL)			/* not initialised */
-		return;
-
-	/* FIXME: should probably also count non-data packets (RFC 4342, 6.1) */
-	if (!dccp_data_packet(skb))
-		return;
+		return 0;
 
 	len = dccp_delta_seqno(cur->li_seqno, DCCP_SKB_CB(skb)->dccpd_seq) + 1;
 
 	if (len - (s64)cur->li_length <= 0)	/* duplicate or reordered */
-		return;
+		return 0;
 
 	if (SUB16(dccp_hdr(skb)->dccph_ccval, cur->li_ccval) > 4)
 		/*
@@ -119,11 +114,14 @@
 		cur->li_is_closed = 1;
 
 	if (tfrc_lh_length(lh) == 1)		/* due to RFC 3448, 6.3.1 */
-		return;
+		return 0;
 
 	cur->li_length = len;
 	tfrc_lh_calc_i_mean(lh);
+
+	return (lh->i_mean < old_i_mean);
 }
+EXPORT_SYMBOL_GPL(tfrc_lh_update_i_mean);
 
 /* Determine if `new_loss' does begin a new loss interval [RFC 4342, 10.2] */
 static inline u8 tfrc_lh_is_new_loss(struct tfrc_loss_interval *cur,
@@ -140,18 +138,18 @@
  * @sk:		   Used by @calc_first_li in caller-specific way (subtyping)
  * Updates I_mean and returns 1 if a new interval has in fact been added to @lh.
  */
-bool tfrc_lh_interval_add(struct tfrc_loss_hist *lh, struct tfrc_rx_hist *rh,
-			  u32 (*calc_first_li)(struct sock *), struct sock *sk)
+int tfrc_lh_interval_add(struct tfrc_loss_hist *lh, struct tfrc_rx_hist *rh,
+			 u32 (*calc_first_li)(struct sock *), struct sock *sk)
 {
 	struct tfrc_loss_interval *cur = tfrc_lh_peek(lh), *new;
 
 	if (cur != NULL && !tfrc_lh_is_new_loss(cur, tfrc_rx_hist_loss_prev(rh)))
-		return false;
+		return 0;
 
 	new = tfrc_lh_demand_next(lh);
 	if (unlikely(new == NULL)) {
 		DCCP_CRIT("Cannot allocate/add loss record.");
-		return false;
+		return 0;
 	}
 
 	new->li_seqno	  = tfrc_rx_hist_loss_prev(rh)->tfrchrx_seqno;
@@ -169,7 +167,7 @@
 
 		tfrc_lh_calc_i_mean(lh);
 	}
-	return true;
+	return 1;
 }
 EXPORT_SYMBOL_GPL(tfrc_lh_interval_add);
 
diff --git a/net/dccp/ccids/lib/loss_interval.h b/net/dccp/ccids/lib/loss_interval.h
index d08a226..246018a 100644
--- a/net/dccp/ccids/lib/loss_interval.h
+++ b/net/dccp/ccids/lib/loss_interval.h
@@ -67,9 +67,9 @@
 
 struct tfrc_rx_hist;
 
-extern bool tfrc_lh_interval_add(struct tfrc_loss_hist *, struct tfrc_rx_hist *,
+extern int  tfrc_lh_interval_add(struct tfrc_loss_hist *, struct tfrc_rx_hist *,
 				 u32 (*first_li)(struct sock *), struct sock *);
-extern void tfrc_lh_update_i_mean(struct tfrc_loss_hist *lh, struct sk_buff *);
+extern u8   tfrc_lh_update_i_mean(struct tfrc_loss_hist *lh, struct sk_buff *);
 extern void tfrc_lh_cleanup(struct tfrc_loss_hist *lh);
 
 #endif /* _DCCP_LI_HIST_ */
diff --git a/net/dccp/ccids/lib/packet_history.c b/net/dccp/ccids/lib/packet_history.c
index cce9f03..6cc108a 100644
--- a/net/dccp/ccids/lib/packet_history.c
+++ b/net/dccp/ccids/lib/packet_history.c
@@ -40,6 +40,18 @@
 #include "packet_history.h"
 #include "../../dccp.h"
 
+/**
+ *  tfrc_tx_hist_entry  -  Simple singly-linked TX history list
+ *  @next:  next oldest entry (LIFO order)
+ *  @seqno: sequence number of this entry
+ *  @stamp: send time of packet with sequence number @seqno
+ */
+struct tfrc_tx_hist_entry {
+	struct tfrc_tx_hist_entry *next;
+	u64			  seqno;
+	ktime_t			  stamp;
+};
+
 /*
  * Transmitter History Routines
  */
@@ -61,6 +73,15 @@
 	}
 }
 
+static struct tfrc_tx_hist_entry *
+	tfrc_tx_hist_find_entry(struct tfrc_tx_hist_entry *head, u64 seqno)
+{
+	while (head != NULL && head->seqno != seqno)
+		head = head->next;
+
+	return head;
+}
+
 int tfrc_tx_hist_add(struct tfrc_tx_hist_entry **headp, u64 seqno)
 {
 	struct tfrc_tx_hist_entry *entry = kmem_cache_alloc(tfrc_tx_hist_slab, gfp_any());
@@ -90,6 +111,25 @@
 }
 EXPORT_SYMBOL_GPL(tfrc_tx_hist_purge);
 
+u32 tfrc_tx_hist_rtt(struct tfrc_tx_hist_entry *head, const u64 seqno,
+		     const ktime_t now)
+{
+	u32 rtt = 0;
+	struct tfrc_tx_hist_entry *packet = tfrc_tx_hist_find_entry(head, seqno);
+
+	if (packet != NULL) {
+		rtt = ktime_us_delta(now, packet->stamp);
+		/*
+		 * Garbage-collect older (irrelevant) entries:
+		 */
+		tfrc_tx_hist_purge(&packet->next);
+	}
+
+	return rtt;
+}
+EXPORT_SYMBOL_GPL(tfrc_tx_hist_rtt);
+
+
 /*
  * 	Receiver History Routines
  */
@@ -151,31 +191,14 @@
 }
 EXPORT_SYMBOL_GPL(tfrc_rx_hist_duplicate);
 
-
-static void __tfrc_rx_hist_swap(struct tfrc_rx_hist *h, const u8 a, const u8 b)
-{
-	struct tfrc_rx_hist_entry *tmp = h->ring[a];
-
-	h->ring[a] = h->ring[b];
-	h->ring[b] = tmp;
-}
-
 static void tfrc_rx_hist_swap(struct tfrc_rx_hist *h, const u8 a, const u8 b)
 {
-	__tfrc_rx_hist_swap(h, tfrc_rx_hist_index(h, a),
-			       tfrc_rx_hist_index(h, b));
-}
+	const u8 idx_a = tfrc_rx_hist_index(h, a),
+		 idx_b = tfrc_rx_hist_index(h, b);
+	struct tfrc_rx_hist_entry *tmp = h->ring[idx_a];
 
-/**
- * tfrc_rx_hist_resume_rtt_sampling  -  Prepare RX history for RTT sampling
- * This is called after loss detection has finished, when the history entry
- * with the index of `loss_count' holds the highest-received sequence number.
- * RTT sampling requires this information at ring[0] (tfrc_rx_hist_sample_rtt).
- */
-static inline void tfrc_rx_hist_resume_rtt_sampling(struct tfrc_rx_hist *h)
-{
-	__tfrc_rx_hist_swap(h, 0, tfrc_rx_hist_index(h, h->loss_count));
-	h->loss_count = h->loss_start = 0;
+	h->ring[idx_a] = h->ring[idx_b];
+	h->ring[idx_b] = tmp;
 }
 
 /*
@@ -192,8 +215,10 @@
 	u64 s0 = tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno,
 	    s1 = DCCP_SKB_CB(skb)->dccpd_seq;
 
-	if (!dccp_loss_free(s0, s1, n1))	/* gap between S0 and S1 */
+	if (!dccp_loss_free(s0, s1, n1)) {	/* gap between S0 and S1 */
 		h->loss_count = 1;
+		tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 1), skb, n1);
+	}
 }
 
 static void __one_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n2)
@@ -215,7 +240,8 @@
 
 		if (dccp_loss_free(s2, s1, n1)) {
 			/* hole is filled: S0, S2, and S1 are consecutive */
-			tfrc_rx_hist_resume_rtt_sampling(h);
+			h->loss_count = 0;
+			h->loss_start = tfrc_rx_hist_index(h, 1);
 		} else
 			/* gap between S2 and S1: just update loss_prev */
 			tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_loss_prev(h), skb, n2);
@@ -268,7 +294,8 @@
 
 			if (dccp_loss_free(s1, s2, n2)) {
 				/* entire hole filled by S0, S3, S1, S2 */
-				tfrc_rx_hist_resume_rtt_sampling(h);
+				h->loss_start = tfrc_rx_hist_index(h, 2);
+				h->loss_count = 0;
 			} else {
 				/* gap remains between S1 and S2 */
 				h->loss_start = tfrc_rx_hist_index(h, 1);
@@ -312,7 +339,8 @@
 
 		if (dccp_loss_free(s2, s3, n3)) {
 			/* no gap between S2 and S3: entire hole is filled */
-			tfrc_rx_hist_resume_rtt_sampling(h);
+			h->loss_start = tfrc_rx_hist_index(h, 3);
+			h->loss_count = 0;
 		} else {
 			/* gap between S2 and S3 */
 			h->loss_start = tfrc_rx_hist_index(h, 2);
@@ -326,13 +354,13 @@
 }
 
 /**
- *  tfrc_rx_congestion_event  -  Loss detection and further processing
- *  @h:		The non-empty RX history object
- *  @lh:	Loss Intervals database to update
- *  @skb:	Currently received packet
- *  @ndp:	The NDP count belonging to @skb
- *  @first_li:	Caller-dependent computation of first loss interval in @lh
- *  @sk:	Used by @calc_first_li (see tfrc_lh_interval_add)
+ *  tfrc_rx_handle_loss  -  Loss detection and further processing
+ *  @h:		    The non-empty RX history object
+ *  @lh:	    Loss Intervals database to update
+ *  @skb:	    Currently received packet
+ *  @ndp:	    The NDP count belonging to @skb
+ *  @calc_first_li: Caller-dependent computation of first loss interval in @lh
+ *  @sk:	    Used by @calc_first_li (see tfrc_lh_interval_add)
  *  Chooses action according to pending loss, updates LI database when a new
  *  loss was detected, and does required post-processing. Returns 1 when caller
  *  should send feedback, 0 otherwise.
@@ -340,20 +368,15 @@
  *  records accordingly, the caller should not perform any more RX history
  *  operations when loss_count is greater than 0 after calling this function.
  */
-bool tfrc_rx_congestion_event(struct tfrc_rx_hist *h,
-			      struct tfrc_loss_hist *lh,
-			      struct sk_buff *skb, const u64 ndp,
-			      u32 (*first_li)(struct sock *), struct sock *sk)
+int tfrc_rx_handle_loss(struct tfrc_rx_hist *h,
+			struct tfrc_loss_hist *lh,
+			struct sk_buff *skb, const u64 ndp,
+			u32 (*calc_first_li)(struct sock *), struct sock *sk)
 {
-	bool new_event = false;
-
-	if (tfrc_rx_hist_duplicate(h, skb))
-		return 0;
+	int is_new_loss = 0;
 
 	if (h->loss_count == 0) {
 		__do_track_loss(h, skb, ndp);
-		tfrc_rx_hist_sample_rtt(h, skb);
-		tfrc_rx_hist_add_packet(h, skb, ndp);
 	} else if (h->loss_count == 1) {
 		__one_after_loss(h, skb, ndp);
 	} else if (h->loss_count != 2) {
@@ -362,57 +385,34 @@
 		/*
 		 * Update Loss Interval database and recycle RX records
 		 */
-		new_event = tfrc_lh_interval_add(lh, h, first_li, sk);
+		is_new_loss = tfrc_lh_interval_add(lh, h, calc_first_li, sk);
 		__three_after_loss(h);
 	}
-
-	/*
-	 * Update moving-average of `s' and the sum of received payload bytes.
-	 */
-	if (dccp_data_packet(skb)) {
-		const u32 payload = skb->len - dccp_hdr(skb)->dccph_doff * 4;
-
-		h->packet_size = tfrc_ewma(h->packet_size, payload, 9);
-		h->bytes_recvd += payload;
-	}
-
-	/* RFC 3448, 6.1: update I_0, whose growth implies p <= p_prev */
-	if (!new_event)
-		tfrc_lh_update_i_mean(lh, skb);
-
-	return new_event;
+	return is_new_loss;
 }
-EXPORT_SYMBOL_GPL(tfrc_rx_congestion_event);
+EXPORT_SYMBOL_GPL(tfrc_rx_handle_loss);
 
-/* Compute the sending rate X_recv measured between feedback intervals */
-u32 tfrc_rx_hist_x_recv(struct tfrc_rx_hist *h, const u32 last_x_recv)
+int tfrc_rx_hist_alloc(struct tfrc_rx_hist *h)
 {
-	u64 bytes = h->bytes_recvd, last_rtt = h->rtt_estimate;
-	s64 delta = ktime_to_us(net_timedelta(h->bytes_start));
+	int i;
 
-	WARN_ON(delta <= 0);
-	/*
-	 * Ensure that the sampling interval for X_recv is at least one RTT,
-	 * by extending the sampling interval backwards in time, over the last
-	 * R_(m-1) seconds, as per rfc3448bis-06, 6.2.
-	 * To reduce noise (e.g. when the RTT changes often), this is only
-	 * done when delta is smaller than RTT/2.
-	 */
-	if (last_x_recv > 0 && delta < last_rtt/2) {
-		tfrc_pr_debug("delta < RTT ==> %ld us < %u us\n",
-			      (long)delta, (unsigned)last_rtt);
-
-		delta = (bytes ? delta : 0) + last_rtt;
-		bytes += div_u64((u64)last_x_recv * last_rtt, USEC_PER_SEC);
+	for (i = 0; i <= TFRC_NDUPACK; i++) {
+		h->ring[i] = kmem_cache_alloc(tfrc_rx_hist_slab, GFP_ATOMIC);
+		if (h->ring[i] == NULL)
+			goto out_free;
 	}
 
-	if (unlikely(bytes == 0)) {
-		DCCP_WARN("X_recv == 0, using old value of %u\n", last_x_recv);
-		return last_x_recv;
+	h->loss_count = h->loss_start = 0;
+	return 0;
+
+out_free:
+	while (i-- != 0) {
+		kmem_cache_free(tfrc_rx_hist_slab, h->ring[i]);
+		h->ring[i] = NULL;
 	}
-	return scaled_div32(bytes, delta);
+	return -ENOBUFS;
 }
-EXPORT_SYMBOL_GPL(tfrc_rx_hist_x_recv);
+EXPORT_SYMBOL_GPL(tfrc_rx_hist_alloc);
 
 void tfrc_rx_hist_purge(struct tfrc_rx_hist *h)
 {
@@ -426,81 +426,73 @@
 }
 EXPORT_SYMBOL_GPL(tfrc_rx_hist_purge);
 
-static int tfrc_rx_hist_alloc(struct tfrc_rx_hist *h)
+/**
+ * tfrc_rx_hist_rtt_last_s - reference entry to compute RTT samples against
+ */
+static inline struct tfrc_rx_hist_entry *
+			tfrc_rx_hist_rtt_last_s(const struct tfrc_rx_hist *h)
 {
-	int i;
-
-	memset(h, 0, sizeof(*h));
-
-	for (i = 0; i <= TFRC_NDUPACK; i++) {
-		h->ring[i] = kmem_cache_alloc(tfrc_rx_hist_slab, GFP_ATOMIC);
-		if (h->ring[i] == NULL) {
-			tfrc_rx_hist_purge(h);
-			return -ENOBUFS;
-		}
-	}
-	return 0;
+	return h->ring[0];
 }
 
-int tfrc_rx_hist_init(struct tfrc_rx_hist *h, struct sock *sk)
+/**
+ * tfrc_rx_hist_rtt_prev_s: previously suitable (wrt rtt_last_s) RTT-sampling entry
+ */
+static inline struct tfrc_rx_hist_entry *
+			tfrc_rx_hist_rtt_prev_s(const struct tfrc_rx_hist *h)
 {
-	if (tfrc_rx_hist_alloc(h))
-		return -ENOBUFS;
-	/*
-	 * Initialise first entry with GSR to start loss detection as early as
-	 * possible. Code using this must not use any other fields. The entry
-	 * will be overwritten once the CCID updates its received packets.
-	 */
-	tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno = dccp_sk(sk)->dccps_gsr;
-	return 0;
+	return h->ring[h->rtt_sample_prev];
 }
-EXPORT_SYMBOL_GPL(tfrc_rx_hist_init);
 
 /**
  * tfrc_rx_hist_sample_rtt  -  Sample RTT from timestamp / CCVal
- * Based on ideas presented in RFC 4342, 8.1. This function expects that no loss
- * is pending and uses the following history entries (via rtt_sample_prev):
- * - h->ring[0]  contains the most recent history entry prior to @skb;
- * - h->ring[1]  is an unused `dummy' entry when the current difference is 0;
+ * Based on ideas presented in RFC 4342, 8.1. Returns 0 if it was not able
+ * to compute a sample with given data - calling function should check this.
  */
-void tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h, const struct sk_buff *skb)
+u32 tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h, const struct sk_buff *skb)
 {
-	struct tfrc_rx_hist_entry *last = h->ring[0];
-	u32 sample, delta_v;
+	u32 sample = 0,
+	    delta_v = SUB16(dccp_hdr(skb)->dccph_ccval,
+			    tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
 
-	/*
-	 * When not to sample:
-	 * - on non-data packets
-	 *   (RFC 4342, 8.1: CCVal only fully defined for data packets);
-	 * - when no data packets have been received yet
-	 *   (FIXME: using sampled packet size as indicator here);
-	 * - as long as there are gaps in the sequence space (pending loss).
-	 */
-	if (!dccp_data_packet(skb) || h->packet_size == 0 ||
-	    tfrc_rx_hist_loss_pending(h))
-		return;
+	if (delta_v < 1 || delta_v > 4) {	/* unsuitable CCVal delta */
+		if (h->rtt_sample_prev == 2) {	/* previous candidate stored */
+			sample = SUB16(tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_ccval,
+				       tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
+			if (sample)
+				sample = 4 / sample *
+				         ktime_us_delta(tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_tstamp,
+							tfrc_rx_hist_rtt_last_s(h)->tfrchrx_tstamp);
+			else    /*
+				 * FIXME: This condition is in principle not
+				 * possible but occurs when CCID is used for
+				 * two-way data traffic. I have tried to trace
+				 * it, but the cause does not seem to be here.
+				 */
+				DCCP_BUG("please report to dccp@vger.kernel.org"
+					 " => prev = %u, last = %u",
+					 tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_ccval,
+					 tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
+		} else if (delta_v < 1) {
+			h->rtt_sample_prev = 1;
+			goto keep_ref_for_next_time;
+		}
 
-	h->rtt_sample_prev = 0;		/* reset previous candidate */
-
-	delta_v = SUB16(dccp_hdr(skb)->dccph_ccval, last->tfrchrx_ccval);
-	if (delta_v == 0) {		/* less than RTT/4 difference */
-		h->rtt_sample_prev = 1;
-		return;
+	} else if (delta_v == 4) /* optimal match */
+		sample = ktime_to_us(net_timedelta(tfrc_rx_hist_rtt_last_s(h)->tfrchrx_tstamp));
+	else {			 /* suboptimal match */
+		h->rtt_sample_prev = 2;
+		goto keep_ref_for_next_time;
 	}
-	sample = dccp_sane_rtt(ktime_to_us(net_timedelta(last->tfrchrx_tstamp)));
 
-	if (delta_v <= 4)		/* between RTT/4 and RTT */
-		sample *= 4 / delta_v;
-	else if (!(sample < h->rtt_estimate && sample > h->rtt_estimate/2))
-		/*
-		* Optimisation: CCVal difference is greater than 1 RTT, yet the
-		* sample is less than the local RTT estimate; which means that
-		* the RTT estimate is too high.
-		* To avoid noise, it is not done if the sample is below RTT/2.
-		*/
-		return;
+	if (unlikely(sample > DCCP_SANE_RTT_MAX)) {
+		DCCP_WARN("RTT sample %u too large, using max\n", sample);
+		sample = DCCP_SANE_RTT_MAX;
+	}
 
-	/* Use a lower weight than usual to increase responsiveness */
-	h->rtt_estimate = tfrc_ewma(h->rtt_estimate, sample, 5);
+	h->rtt_sample_prev = 0;	       /* use current entry as next reference */
+keep_ref_for_next_time:
+
+	return sample;
 }
 EXPORT_SYMBOL_GPL(tfrc_rx_hist_sample_rtt);
diff --git a/net/dccp/ccids/lib/packet_history.h b/net/dccp/ccids/lib/packet_history.h
index 555e65c..461cc91 100644
--- a/net/dccp/ccids/lib/packet_history.h
+++ b/net/dccp/ccids/lib/packet_history.h
@@ -40,28 +40,12 @@
 #include <linux/slab.h>
 #include "tfrc.h"
 
-/**
- *  tfrc_tx_hist_entry  -  Simple singly-linked TX history list
- *  @next:  next oldest entry (LIFO order)
- *  @seqno: sequence number of this entry
- *  @stamp: send time of packet with sequence number @seqno
- */
-struct tfrc_tx_hist_entry {
-	struct tfrc_tx_hist_entry *next;
-	u64			  seqno;
-	ktime_t			  stamp;
-};
-
-static inline struct tfrc_tx_hist_entry *
-	tfrc_tx_hist_find_entry(struct tfrc_tx_hist_entry *head, u64 seqno)
-{
-	while (head != NULL && head->seqno != seqno)
-		head = head->next;
-	return head;
-}
+struct tfrc_tx_hist_entry;
 
 extern int  tfrc_tx_hist_add(struct tfrc_tx_hist_entry **headp, u64 seqno);
 extern void tfrc_tx_hist_purge(struct tfrc_tx_hist_entry **headp);
+extern u32  tfrc_tx_hist_rtt(struct tfrc_tx_hist_entry *head,
+			     const u64 seqno, const ktime_t now);
 
 /* Subtraction a-b modulo-16, respects circular wrap-around */
 #define SUB16(a, b) (((a) + 16 - (b)) & 0xF)
@@ -91,22 +75,12 @@
  * @loss_count:		Number of entries in circular history
  * @loss_start:		Movable index (for loss detection)
  * @rtt_sample_prev:	Used during RTT sampling, points to candidate entry
- * @rtt_estimate:	Receiver RTT estimate
- * @packet_size:	Packet size in bytes (as per RFC 3448, 3.1)
- * @bytes_recvd:	Number of bytes received since @bytes_start
- * @bytes_start:	Start time for counting @bytes_recvd
  */
 struct tfrc_rx_hist {
 	struct tfrc_rx_hist_entry *ring[TFRC_NDUPACK + 1];
 	u8			  loss_count:2,
 				  loss_start:2;
-	/* Receiver RTT sampling */
 #define rtt_sample_prev		  loss_start
-	u32			  rtt_estimate;
-	/* Receiver sampling of application payload lengths */
-	u32			  packet_size,
-				  bytes_recvd;
-	ktime_t			  bytes_start;
 };
 
 /**
@@ -150,50 +124,20 @@
 	return h->loss_count > 0;
 }
 
-/*
- * Accessor functions to retrieve parameters sampled by the RX history
- */
-static inline u32 tfrc_rx_hist_packet_size(const struct tfrc_rx_hist *h)
-{
-	if (h->packet_size == 0) {
-		DCCP_WARN("No sample for s, using fallback\n");
-		return TCP_MIN_RCVMSS;
-	}
-	return h->packet_size;
-
-}
-static inline u32 tfrc_rx_hist_rtt(const struct tfrc_rx_hist *h)
-{
-	if (h->rtt_estimate == 0) {
-		DCCP_WARN("No RTT estimate available, using fallback RTT\n");
-		return  DCCP_FALLBACK_RTT;
-	}
-	return h->rtt_estimate;
-}
-
-static inline void tfrc_rx_hist_restart_byte_counter(struct tfrc_rx_hist *h)
-{
-	h->bytes_recvd = 0;
-	h->bytes_start = ktime_get_real();
-}
-
-extern u32  tfrc_rx_hist_x_recv(struct tfrc_rx_hist *h, const u32 last_x_recv);
-
-
 extern void tfrc_rx_hist_add_packet(struct tfrc_rx_hist *h,
 				    const struct sk_buff *skb, const u64 ndp);
 
 extern int tfrc_rx_hist_duplicate(struct tfrc_rx_hist *h, struct sk_buff *skb);
 
 struct tfrc_loss_hist;
-extern bool tfrc_rx_congestion_event(struct tfrc_rx_hist *h,
-				     struct tfrc_loss_hist *lh,
-				     struct sk_buff *skb, const u64 ndp,
-				     u32 (*first_li)(struct sock *sk),
-				     struct sock *sk);
-extern void tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h,
-				    const struct sk_buff *skb);
-extern int  tfrc_rx_hist_init(struct tfrc_rx_hist *h, struct sock *sk);
+extern int  tfrc_rx_handle_loss(struct tfrc_rx_hist *h,
+				struct tfrc_loss_hist *lh,
+				struct sk_buff *skb, const u64 ndp,
+				u32 (*first_li)(struct sock *sk),
+				struct sock *sk);
+extern u32 tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h,
+				   const struct sk_buff *skb);
+extern int tfrc_rx_hist_alloc(struct tfrc_rx_hist *h);
 extern void tfrc_rx_hist_purge(struct tfrc_rx_hist *h);
 
 #endif /* _DCCP_PKT_HIST_ */
diff --git a/net/dccp/ccids/lib/tfrc.h b/net/dccp/ccids/lib/tfrc.h
index ede12f5..ed98575 100644
--- a/net/dccp/ccids/lib/tfrc.h
+++ b/net/dccp/ccids/lib/tfrc.h
@@ -48,21 +48,6 @@
 }
 
 /**
- * tfrc_scaled_sqrt  -  Compute scaled integer sqrt(x) for 0 < x < 2^22-1
- * Uses scaling to improve accuracy of the integer approximation of sqrt(). The
- * scaling factor of 2^10 limits the maximum @sample to 4e6; this is okay for
- * clamped RTT samples (dccp_sample_rtt).
- * Should best be used for expressions of type sqrt(x)/sqrt(y), since then the
- * scaling factor is neutralised. For this purpose, it avoids returning zero.
- */
-static inline u16 tfrc_scaled_sqrt(const u32 sample)
-{
-	const unsigned long non_zero_sample = sample ? : 1;
-
-	return int_sqrt(non_zero_sample << 10);
-}
-
-/**
  * tfrc_ewma  -  Exponentially weighted moving average
  * @weight: Weight to be used as damping factor, in units of 1/10
  */
@@ -73,7 +58,6 @@
 
 extern u32  tfrc_calc_x(u16 s, u32 R, u32 p);
 extern u32  tfrc_calc_x_reverse_lookup(u32 fvalue);
-extern u32  tfrc_invert_loss_event_rate(u32 loss_event_rate);
 
 extern int  tfrc_tx_packet_history_init(void);
 extern void tfrc_tx_packet_history_exit(void);
diff --git a/net/dccp/ccids/lib/tfrc_equation.c b/net/dccp/ccids/lib/tfrc_equation.c
index 38239c4..2f20a29c 100644
--- a/net/dccp/ccids/lib/tfrc_equation.c
+++ b/net/dccp/ccids/lib/tfrc_equation.c
@@ -632,16 +632,8 @@
 
 	if (p <= TFRC_CALC_X_SPLIT) 		{     /* 0.0000 < p <= 0.05   */
 		if (p < TFRC_SMALLEST_P) {	      /* 0.0000 < p <  0.0001 */
-			/*
-			 * In the congestion-avoidance phase p decays towards 0
-			 * when there are no further losses, so this case is
-			 * natural. Truncating to p_min = 0.01% means that the
-			 * maximum achievable throughput is limited to about
-			 * X_calc_max = 122.4 * s/RTT (see RFC 3448, 3.1); e.g.
-			 * with s=1500 bytes, RTT=0.01 s: X_calc_max = 147 Mbps.
-			 */
-			tfrc_pr_debug("Value of p (%d) below resolution. "
-				      "Substituting %d\n", p, TFRC_SMALLEST_P);
+			DCCP_WARN("Value of p (%d) below resolution. "
+				  "Substituting %d\n", p, TFRC_SMALLEST_P);
 			index = 0;
 		} else 				      /* 0.0001 <= p <= 0.05  */
 			index =  p/TFRC_SMALLEST_P - 1;
@@ -666,6 +658,7 @@
 	result = scaled_div(s, R);
 	return scaled_div32(result, f);
 }
+
 EXPORT_SYMBOL_GPL(tfrc_calc_x);
 
 /**
@@ -700,19 +693,5 @@
 	index = tfrc_binsearch(fvalue, 0);
 	return (index + 1) * 1000000 / TFRC_CALC_X_ARRSIZE;
 }
-EXPORT_SYMBOL_GPL(tfrc_calc_x_reverse_lookup);
 
-/**
- * tfrc_invert_loss_event_rate  -  Compute p so that 10^6 corresponds to 100%
- * When @loss_event_rate is large, there is a chance that p is truncated to 0.
- * To avoid re-entering slow-start in that case, we set p = TFRC_SMALLEST_P > 0.
- */
-u32 tfrc_invert_loss_event_rate(u32 loss_event_rate)
-{
-	if (loss_event_rate == UINT_MAX)		/* see RFC 4342, 8.5 */
-		return 0;
-	if (unlikely(loss_event_rate == 0))		/* map 1/0 into 100% */
-		return 1000000;
-	return max_t(u32, scaled_div(1, loss_event_rate), TFRC_SMALLEST_P);
-}
-EXPORT_SYMBOL_GPL(tfrc_invert_loss_event_rate);
+EXPORT_SYMBOL_GPL(tfrc_calc_x_reverse_lookup);