1 files changed, 417 insertions, 94 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index d77c0d29e239..99b7ecbe8893 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -701,13 +701,10 @@ static inline void tcp_set_rto(struct sock *sk)
 	 *    all the algo is pure shit and should be replaced
 	 *    with correct one. It is exactly, which we pretend to do.
 	 */
-}
 
-/* NOTE: clamping at TCP_RTO_MIN is not required, current algo
- * guarantees that rto is higher.
- */
-static inline void tcp_bound_rto(struct sock *sk)
-{
+	/* NOTE: clamping at TCP_RTO_MIN is not required, current algo
+	 * guarantees that rto is higher.
+	 */
 	if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX)
 		inet_csk(sk)->icsk_rto = TCP_RTO_MAX;
 }
@@ -928,7 +925,6 @@ static void tcp_init_metrics(struct sock *sk)
 		tp->mdev_max = tp->rttvar = max(tp->mdev, tcp_rto_min(sk));
 	}
 	tcp_set_rto(sk);
-	tcp_bound_rto(sk);
 	if (inet_csk(sk)->icsk_rto < TCP_TIMEOUT_INIT && !tp->rx_opt.saw_tstamp)
 		goto reset;
 	tp->snd_cwnd = tcp_init_cwnd(tp, dst);
@@ -1002,7 +998,8 @@ static void tcp_skb_mark_lost(struct tcp_sock *tp, struct sk_buff *skb)
 	}
 }
 
-void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp, struct sk_buff *skb)
+static void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp,
+					    struct sk_buff *skb)
 {
 	tcp_verify_retransmit_hint(tp, skb);
 
@@ -1236,31 +1233,58 @@ static int tcp_check_dsack(struct sock *sk, struct sk_buff *ack_skb,
 	return dup_sack;
 }
 
+struct tcp_sacktag_state {
+	int reord;
+	int fack_count;
+	int flag;
+};
+
 /* Check if skb is fully within the SACK block. In presence of GSO skbs,
  * the incoming SACK may not exactly match but we can find smaller MSS
  * aligned portion of it that matches. Therefore we might need to fragment
  * which may fail and creates some hassle (caller must handle error case
  * returns).
+ *
+ * FIXME: this could be merged to shift decision code
  */
 static int tcp_match_skb_to_sack(struct sock *sk, struct sk_buff *skb,
 				 u32 start_seq, u32 end_seq)
 {
 	int in_sack, err;
 	unsigned int pkt_len;
+	unsigned int mss;
 
 	in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
 		  !before(end_seq, TCP_SKB_CB(skb)->end_seq);
 
 	if (tcp_skb_pcount(skb) > 1 && !in_sack &&
 	    after(TCP_SKB_CB(skb)->end_seq, start_seq)) {
-
+		mss = tcp_skb_mss(skb);
 		in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq);
 
-		if (!in_sack)
+		if (!in_sack) {
 			pkt_len = start_seq - TCP_SKB_CB(skb)->seq;
-		else
+			if (pkt_len < mss)
+				pkt_len = mss;
+		} else {
 			pkt_len = end_seq - TCP_SKB_CB(skb)->seq;
-		err = tcp_fragment(sk, skb, pkt_len, skb_shinfo(skb)->gso_size);
+			if (pkt_len < mss)
+				return -EINVAL;
+		}
+
+		/* Round if necessary so that SACKs cover only full MSSes
+		 * and/or the remaining small portion (if present)
+		 */
+		if (pkt_len > mss) {
+			unsigned int new_len = (pkt_len / mss) * mss;
+			if (!in_sack && new_len < pkt_len) {
+				new_len += mss;
+				if (new_len > skb->len)
+					return 0;
+			}
+			pkt_len = new_len;
+		}
+		err = tcp_fragment(sk, skb, pkt_len, mss);
 		if (err < 0)
 			return err;
 	}
@@ -1268,24 +1292,25 @@ static int tcp_match_skb_to_sack(struct sock *sk, struct sk_buff *skb,
 	return in_sack;
 }
 
-static int tcp_sacktag_one(struct sk_buff *skb, struct sock *sk,
-			   int *reord, int dup_sack, int fack_count)
+static u8 tcp_sacktag_one(struct sk_buff *skb, struct sock *sk,
+			  struct tcp_sacktag_state *state,
+			  int dup_sack, int pcount)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 	u8 sacked = TCP_SKB_CB(skb)->sacked;
-	int flag = 0;
+	int fack_count = state->fack_count;
 
 	/* Account D-SACK for retransmitted packet. */
 	if (dup_sack && (sacked & TCPCB_RETRANS)) {
 		if (after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker))
 			tp->undo_retrans--;
 		if (sacked & TCPCB_SACKED_ACKED)
-			*reord = min(fack_count, *reord);
+			state->reord = min(fack_count, state->reord);
 	}
 
 	/* Nothing to do; acked frame is about to be dropped (was ACKed). */
 	if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
-		return flag;
+		return sacked;
 
 	if (!(sacked & TCPCB_SACKED_ACKED)) {
 		if (sacked & TCPCB_SACKED_RETRANS) {
@@ -1294,10 +1319,9 @@ static int tcp_sacktag_one(struct sk_buff *skb, struct sock *sk,
 			 * that retransmission is still in flight.
 			 */
 			if (sacked & TCPCB_LOST) {
-				TCP_SKB_CB(skb)->sacked &=
-					~(TCPCB_LOST|TCPCB_SACKED_RETRANS);
-				tp->lost_out -= tcp_skb_pcount(skb);
-				tp->retrans_out -= tcp_skb_pcount(skb);
+				sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS);
+				tp->lost_out -= pcount;
+				tp->retrans_out -= pcount;
 			}
 		} else {
 			if (!(sacked & TCPCB_RETRANS)) {
@@ -1306,56 +1330,280 @@ static int tcp_sacktag_one(struct sk_buff *skb, struct sock *sk,
 				 */
 				if (before(TCP_SKB_CB(skb)->seq,
 					   tcp_highest_sack_seq(tp)))
-					*reord = min(fack_count, *reord);
+					state->reord = min(fack_count,
+							   state->reord);
 
 				/* SACK enhanced F-RTO (RFC4138; Appendix B) */
 				if (!after(TCP_SKB_CB(skb)->end_seq, tp->frto_highmark))
-					flag |= FLAG_ONLY_ORIG_SACKED;
+					state->flag |= FLAG_ONLY_ORIG_SACKED;
 			}
 
 			if (sacked & TCPCB_LOST) {
-				TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
-				tp->lost_out -= tcp_skb_pcount(skb);
+				sacked &= ~TCPCB_LOST;
+				tp->lost_out -= pcount;
 			}
 		}
 
-		TCP_SKB_CB(skb)->sacked |= TCPCB_SACKED_ACKED;
-		flag |= FLAG_DATA_SACKED;
-		tp->sacked_out += tcp_skb_pcount(skb);
+		sacked |= TCPCB_SACKED_ACKED;
+		state->flag |= FLAG_DATA_SACKED;
+		tp->sacked_out += pcount;
 
-		fack_count += tcp_skb_pcount(skb);
+		fack_count += pcount;
 
 		/* Lost marker hint past SACKed? Tweak RFC3517 cnt */
 		if (!tcp_is_fack(tp) && (tp->lost_skb_hint != NULL) &&
 		    before(TCP_SKB_CB(skb)->seq,
 			   TCP_SKB_CB(tp->lost_skb_hint)->seq))
-			tp->lost_cnt_hint += tcp_skb_pcount(skb);
+			tp->lost_cnt_hint += pcount;
 
 		if (fack_count > tp->fackets_out)
 			tp->fackets_out = fack_count;
-
-		if (!before(TCP_SKB_CB(skb)->seq, tcp_highest_sack_seq(tp)))
-			tcp_advance_highest_sack(sk, skb);
 	}
 
 	/* D-SACK. We can detect redundant retransmission in S|R and plain R
 	 * frames and clear it. undo_retrans is decreased above, L|R frames
 	 * are accounted above as well.
 	 */
-	if (dup_sack && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)) {
-		TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
-		tp->retrans_out -= tcp_skb_pcount(skb);
+	if (dup_sack && (sacked & TCPCB_SACKED_RETRANS)) {
+		sacked &= ~TCPCB_SACKED_RETRANS;
+		tp->retrans_out -= pcount;
 	}
 
-	return flag;
+	return sacked;
+}
+
+static int tcp_shifted_skb(struct sock *sk, struct sk_buff *skb,
+			   struct tcp_sacktag_state *state,
+			   unsigned int pcount, int shifted, int mss)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct sk_buff *prev = tcp_write_queue_prev(sk, skb);
+
+	BUG_ON(!pcount);
+
+	/* Tweak before seqno plays */
+	if (!tcp_is_fack(tp) && tcp_is_sack(tp) && tp->lost_skb_hint &&
+	    !before(TCP_SKB_CB(tp->lost_skb_hint)->seq, TCP_SKB_CB(skb)->seq))
+		tp->lost_cnt_hint += pcount;
+
+	TCP_SKB_CB(prev)->end_seq += shifted;
+	TCP_SKB_CB(skb)->seq += shifted;
+
+	skb_shinfo(prev)->gso_segs += pcount;
+	BUG_ON(skb_shinfo(skb)->gso_segs < pcount);
+	skb_shinfo(skb)->gso_segs -= pcount;
+
+	/* When we're adding to gso_segs == 1, gso_size will be zero,
+	 * in theory this shouldn't be necessary but as long as DSACK
+	 * code can come after this skb later on it's better to keep
+	 * setting gso_size to something.
+	 */
+	if (!skb_shinfo(prev)->gso_size) {
+		skb_shinfo(prev)->gso_size = mss;
+		skb_shinfo(prev)->gso_type = sk->sk_gso_type;
+	}
+
+	/* CHECKME: To clear or not to clear? Mimics normal skb currently */
+	if (skb_shinfo(skb)->gso_segs <= 1) {
+		skb_shinfo(skb)->gso_size = 0;
+		skb_shinfo(skb)->gso_type = 0;
+	}
+
+	/* We discard results */
+	tcp_sacktag_one(skb, sk, state, 0, pcount);
+
+	/* Difference in this won't matter, both ACKed by the same cumul. ACK */
+	TCP_SKB_CB(prev)->sacked |= (TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS);
+
+	if (skb->len > 0) {
+		BUG_ON(!tcp_skb_pcount(skb));
+		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKSHIFTED);
+		return 0;
+	}
+
+	/* Whole SKB was eaten :-) */
+
+	if (skb == tp->retransmit_skb_hint)
+		tp->retransmit_skb_hint = prev;
+	if (skb == tp->scoreboard_skb_hint)
+		tp->scoreboard_skb_hint = prev;
+	if (skb == tp->lost_skb_hint) {
+		tp->lost_skb_hint = prev;
+		tp->lost_cnt_hint -= tcp_skb_pcount(prev);
+	}
+
+	TCP_SKB_CB(skb)->flags |= TCP_SKB_CB(prev)->flags;
+	if (skb == tcp_highest_sack(sk))
+		tcp_advance_highest_sack(sk, skb);
+
+	tcp_unlink_write_queue(skb, sk);
+	sk_wmem_free_skb(sk, skb);
+
+	NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKMERGED);
+
+	return 1;
+}
+
+/* I wish gso_size would have a bit more sane initialization than
+ * something-or-zero which complicates things
+ */
+static int tcp_skb_seglen(struct sk_buff *skb)
+{
+	return tcp_skb_pcount(skb) == 1 ? skb->len : tcp_skb_mss(skb);
+}
+
+/* Shifting pages past head area doesn't work */
+static int skb_can_shift(struct sk_buff *skb)
+{
+	return !skb_headlen(skb) && skb_is_nonlinear(skb);
+}
+
+/* Try collapsing SACK blocks spanning across multiple skbs to a single
+ * skb.
+ */
+static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb,
+					  struct tcp_sacktag_state *state,
+					  u32 start_seq, u32 end_seq,
+					  int dup_sack)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct sk_buff *prev;
+	int mss;
+	int pcount = 0;
+	int len;
+	int in_sack;
+
+	if (!sk_can_gso(sk))
+		goto fallback;
+
+	/* Normally R but no L won't result in plain S */
+	if (!dup_sack &&
+	    (TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_RETRANS)) == TCPCB_SACKED_RETRANS)
+		goto fallback;
+	if (!skb_can_shift(skb))
+		goto fallback;
+	/* This frame is about to be dropped (was ACKed). */
+	if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
+		goto fallback;
+
+	/* Can only happen with delayed DSACK + discard craziness */
+	if (unlikely(skb == tcp_write_queue_head(sk)))
+		goto fallback;
+	prev = tcp_write_queue_prev(sk, skb);
+
+	if ((TCP_SKB_CB(prev)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED)
+		goto fallback;
+
+	in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
+		  !before(end_seq, TCP_SKB_CB(skb)->end_seq);
+
+	if (in_sack) {
+		len = skb->len;
+		pcount = tcp_skb_pcount(skb);
+		mss = tcp_skb_seglen(skb);
+
+		/* TODO: Fix DSACKs to not fragment already SACKed and we can
+		 * drop this restriction as unnecessary
+		 */
+		if (mss != tcp_skb_seglen(prev))
+			goto fallback;
+	} else {
+		if (!after(TCP_SKB_CB(skb)->end_seq, start_seq))
+			goto noop;
+		/* CHECKME: This is non-MSS split case only?, this will
+		 * cause skipped skbs due to advancing loop btw, original
+		 * has that feature too
+		 */
+		if (tcp_skb_pcount(skb) <= 1)
+			goto noop;
+
+		in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq);
+		if (!in_sack) {
+			/* TODO: head merge to next could be attempted here
+			 * if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)),
+			 * though it might not be worth of the additional hassle
+			 *
+			 * ...we can probably just fallback to what was done
+			 * previously. We could try merging non-SACKed ones
+			 * as well but it probably isn't going to buy off
+			 * because later SACKs might again split them, and
+			 * it would make skb timestamp tracking considerably
+			 * harder problem.
+			 */
+			goto fallback;
+		}
+
+		len = end_seq - TCP_SKB_CB(skb)->seq;
+		BUG_ON(len < 0);
+		BUG_ON(len > skb->len);
+
+		/* MSS boundaries should be honoured or else pcount will
+		 * severely break even though it makes things bit trickier.
+		 * Optimize common case to avoid most of the divides
+		 */
+		mss = tcp_skb_mss(skb);
+
+		/* TODO: Fix DSACKs to not fragment already SACKed and we can
+		 * drop this restriction as unnecessary
+		 */
+		if (mss != tcp_skb_seglen(prev))
+			goto fallback;
+
+		if (len == mss) {
+			pcount = 1;
+		} else if (len < mss) {
+			goto noop;
+		} else {
+			pcount = len / mss;
+			len = pcount * mss;
+		}
+	}
+
+	if (!skb_shift(prev, skb, len))
+		goto fallback;
+	if (!tcp_shifted_skb(sk, skb, state, pcount, len, mss))
+		goto out;
+
+	/* Hole filled allows collapsing with the next as well, this is very
+	 * useful when hole on every nth skb pattern happens
+	 */
+	if (prev == tcp_write_queue_tail(sk))
+		goto out;
+	skb = tcp_write_queue_next(sk, prev);
+
+	if (!skb_can_shift(skb) ||
+	    (skb == tcp_send_head(sk)) ||
+	    ((TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED) ||
+	    (mss != tcp_skb_seglen(skb)))
+		goto out;
+
+	len = skb->len;
+	if (skb_shift(prev, skb, len)) {
+		pcount += tcp_skb_pcount(skb);
+		tcp_shifted_skb(sk, skb, state, tcp_skb_pcount(skb), len, mss);
+	}
+
+out:
+	state->fack_count += pcount;
+	return prev;
+
+noop:
+	return skb;
+
+fallback:
+	NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKSHIFTFALLBACK);
+	return NULL;
 }
 
 static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk,
 					struct tcp_sack_block *next_dup,
+					struct tcp_sacktag_state *state,
 					u32 start_seq, u32 end_seq,
-					int dup_sack_in, int *fack_count,
-					int *reord, int *flag)
+					int dup_sack_in)
 {
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct sk_buff *tmp;
+
 	tcp_for_write_queue_from(skb, sk) {
 		int in_sack = 0;
 		int dup_sack = dup_sack_in;
@@ -1376,17 +1624,42 @@ static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk,
 				dup_sack = 1;
 		}
 
-		if (in_sack <= 0)
-			in_sack = tcp_match_skb_to_sack(sk, skb, start_seq,
-							end_seq);
+		/* skb reference here is a bit tricky to get right, since
+		 * shifting can eat and free both this skb and the next,
+		 * so not even _safe variant of the loop is enough.
+		 */
+		if (in_sack <= 0) {
+			tmp = tcp_shift_skb_data(sk, skb, state,
+						 start_seq, end_seq, dup_sack);
+			if (tmp != NULL) {
+				if (tmp != skb) {
+					skb = tmp;
+					continue;
+				}
+
+				in_sack = 0;
+			} else {
+				in_sack = tcp_match_skb_to_sack(sk, skb,
+								start_seq,
+								end_seq);
+			}
+		}
+
 		if (unlikely(in_sack < 0))
 			break;
 
-		if (in_sack)
-			*flag |= tcp_sacktag_one(skb, sk, reord, dup_sack,
-						 *fack_count);
+		if (in_sack) {
+			TCP_SKB_CB(skb)->sacked = tcp_sacktag_one(skb, sk,
+								  state,
+								  dup_sack,
+								  tcp_skb_pcount(skb));
+
+			if (!before(TCP_SKB_CB(skb)->seq,
+				    tcp_highest_sack_seq(tp)))
+				tcp_advance_highest_sack(sk, skb);
+		}
 
-		*fack_count += tcp_skb_pcount(skb);
+		state->fack_count += tcp_skb_pcount(skb);
 	}
 	return skb;
 }
@@ -1395,16 +1668,17 @@ static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk,
  * a normal way
  */
 static struct sk_buff *tcp_sacktag_skip(struct sk_buff *skb, struct sock *sk,
-					u32 skip_to_seq, int *fack_count)
+					struct tcp_sacktag_state *state,
+					u32 skip_to_seq)
 {
 	tcp_for_write_queue_from(skb, sk) {
 		if (skb == tcp_send_head(sk))
 			break;
 
-		if (!before(TCP_SKB_CB(skb)->end_seq, skip_to_seq))
+		if (after(TCP_SKB_CB(skb)->end_seq, skip_to_seq))
 			break;
 
-		*fack_count += tcp_skb_pcount(skb);
+		state->fack_count += tcp_skb_pcount(skb);
 	}
 	return skb;
 }
@@ -1412,18 +1686,17 @@ static struct sk_buff *tcp_sacktag_skip(struct sk_buff *skb, struct sock *sk,
 static struct sk_buff *tcp_maybe_skipping_dsack(struct sk_buff *skb,
 						struct sock *sk,
 						struct tcp_sack_block *next_dup,
-						u32 skip_to_seq,
-						int *fack_count, int *reord,
-						int *flag)
+						struct tcp_sacktag_state *state,
+						u32 skip_to_seq)
 {
 	if (next_dup == NULL)
 		return skb;
 
 	if (before(next_dup->start_seq, skip_to_seq)) {
-		skb = tcp_sacktag_skip(skb, sk, next_dup->start_seq, fack_count);
-		skb = tcp_sacktag_walk(skb, sk, NULL,
-				     next_dup->start_seq, next_dup->end_seq,
-				     1, fack_count, reord, flag);
+		skb = tcp_sacktag_skip(skb, sk, state, next_dup->start_seq);
+		skb = tcp_sacktag_walk(skb, sk, NULL, state,
+				       next_dup->start_seq, next_dup->end_seq,
+				       1);
 	}
 
 	return skb;
@@ -1445,16 +1718,17 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb,
 	struct tcp_sack_block_wire *sp_wire = (struct tcp_sack_block_wire *)(ptr+2);
 	struct tcp_sack_block sp[TCP_NUM_SACKS];
 	struct tcp_sack_block *cache;
+	struct tcp_sacktag_state state;
 	struct sk_buff *skb;
 	int num_sacks = min(TCP_NUM_SACKS, (ptr[1] - TCPOLEN_SACK_BASE) >> 3);
 	int used_sacks;
-	int reord = tp->packets_out;
-	int flag = 0;
 	int found_dup_sack = 0;
-	int fack_count;
 	int i, j;
 	int first_sack_index;
 
+	state.flag = 0;
+	state.reord = tp->packets_out;
+
 	if (!tp->sacked_out) {
 		if (WARN_ON(tp->fackets_out))
 			tp->fackets_out = 0;
@@ -1464,7 +1738,7 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb,
 	found_dup_sack = tcp_check_dsack(sk, ack_skb, sp_wire,
 					 num_sacks, prior_snd_una);
 	if (found_dup_sack)
-		flag |= FLAG_DSACKING_ACK;
+		state.flag |= FLAG_DSACKING_ACK;
 
 	/* Eliminate too old ACKs, but take into
 	 * account more or less fresh ones, they can
@@ -1533,7 +1807,7 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb,
 	}
 
 	skb = tcp_write_queue_head(sk);
-	fack_count = 0;
+	state.fack_count = 0;
 	i = 0;
 
 	if (!tp->sacked_out) {
@@ -1558,7 +1832,7 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb,
 
 		/* Event "B" in the comment above. */
 		if (after(end_seq, tp->high_seq))
-			flag |= FLAG_DATA_LOST;
+			state.flag |= FLAG_DATA_LOST;
 
 		/* Skip too early cached blocks */
 		while (tcp_sack_cache_ok(tp, cache) &&
@@ -1571,13 +1845,13 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb,
 
 			/* Head todo? */
 			if (before(start_seq, cache->start_seq)) {
-				skb = tcp_sacktag_skip(skb, sk, start_seq,
-						       &fack_count);
+				skb = tcp_sacktag_skip(skb, sk, &state,
+						       start_seq);
 				skb = tcp_sacktag_walk(skb, sk, next_dup,
+						       &state,
 						       start_seq,
 						       cache->start_seq,
-						       dup_sack, &fack_count,
-						       &reord, &flag);
+						       dup_sack);
 			}
 
 			/* Rest of the block already fully processed? */
@@ -1585,9 +1859,8 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb,
 				goto advance_sp;
 
 			skb = tcp_maybe_skipping_dsack(skb, sk, next_dup,
-						       cache->end_seq,
-						       &fack_count, &reord,
-						       &flag);
+						       &state,
+						       cache->end_seq);
 
 			/* ...tail remains todo... */
 			if (tcp_highest_sack_seq(tp) == cache->end_seq) {
@@ -1595,13 +1868,12 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb,
 				skb = tcp_highest_sack(sk);
 				if (skb == NULL)
 					break;
-				fack_count = tp->fackets_out;
+				state.fack_count = tp->fackets_out;
 				cache++;
 				goto walk;
 			}
 
-			skb = tcp_sacktag_skip(skb, sk, cache->end_seq,
-					       &fack_count);
+			skb = tcp_sacktag_skip(skb, sk, &state, cache->end_seq);
 			/* Check overlap against next cached too (past this one already) */
 			cache++;
 			continue;
@@ -1611,20 +1883,20 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb,
 			skb = tcp_highest_sack(sk);
 			if (skb == NULL)
 				break;
-			fack_count = tp->fackets_out;
+			state.fack_count = tp->fackets_out;
 		}
-		skb = tcp_sacktag_skip(skb, sk, start_seq, &fack_count);
+		skb = tcp_sacktag_skip(skb, sk, &state, start_seq);
 
 walk:
-		skb = tcp_sacktag_walk(skb, sk, next_dup, start_seq, end_seq,
-				       dup_sack, &fack_count, &reord, &flag);
+		skb = tcp_sacktag_walk(skb, sk, next_dup, &state,
+				       start_seq, end_seq, dup_sack);
 
 advance_sp:
 		/* SACK enhanced FRTO (RFC4138, Appendix B): Clearing correct
 		 * due to in-order walk
 		 */
 		if (after(end_seq, tp->frto_highmark))
-			flag &= ~FLAG_ONLY_ORIG_SACKED;
+			state.flag &= ~FLAG_ONLY_ORIG_SACKED;
 
 		i++;
 	}
@@ -1641,10 +1913,10 @@ advance_sp:
 
 	tcp_verify_left_out(tp);
 
-	if ((reord < tp->fackets_out) &&
+	if ((state.reord < tp->fackets_out) &&
 	    ((icsk->icsk_ca_state != TCP_CA_Loss) || tp->undo_marker) &&
 	    (!tp->frto_highmark || after(tp->snd_una, tp->frto_highmark)))
-		tcp_update_reordering(sk, tp->fackets_out - reord, 0);
+		tcp_update_reordering(sk, tp->fackets_out - state.reord, 0);
 
 out:
 
@@ -1654,13 +1926,13 @@ out:
 	WARN_ON((int)tp->retrans_out < 0);
 	WARN_ON((int)tcp_packets_in_flight(tp) < 0);
 #endif
-	return flag;
+	return state.flag;
 }
 
 /* Limits sacked_out so that sum with lost_out isn't ever larger than
  * packets_out. Returns zero if sacked_out adjustement wasn't necessary.
  */
-int tcp_limit_reno_sacked(struct tcp_sock *tp)
+static int tcp_limit_reno_sacked(struct tcp_sock *tp)
 {
 	u32 holes;
 
@@ -2336,9 +2608,9 @@ static void DBGUNDO(struct sock *sk, const char *msg)
 	struct inet_sock *inet = inet_sk(sk);
 
 	if (sk->sk_family == AF_INET) {
-		printk(KERN_DEBUG "Undo %s " NIPQUAD_FMT "/%u c%u l%u ss%u/%u p%u\n",
+		printk(KERN_DEBUG "Undo %s %pI4/%u c%u l%u ss%u/%u p%u\n",
 		       msg,
-		       NIPQUAD(inet->daddr), ntohs(inet->dport),
+		       &inet->daddr, ntohs(inet->dport),
 		       tp->snd_cwnd, tcp_left_out(tp),
 		       tp->snd_ssthresh, tp->prior_ssthresh,
 		       tp->packets_out);
@@ -2346,9 +2618,9 @@ static void DBGUNDO(struct sock *sk, const char *msg)
 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
 	else if (sk->sk_family == AF_INET6) {
 		struct ipv6_pinfo *np = inet6_sk(sk);
-		printk(KERN_DEBUG "Undo %s " NIP6_FMT "/%u c%u l%u ss%u/%u p%u\n",
+		printk(KERN_DEBUG "Undo %s %pI6/%u c%u l%u ss%u/%u p%u\n",
 		       msg,
-		       NIP6(np->daddr), ntohs(inet->dport),
+		       &np->daddr, ntohs(inet->dport),
 		       tp->snd_cwnd, tcp_left_out(tp),
 		       tp->snd_ssthresh, tp->prior_ssthresh,
 		       tp->packets_out);
@@ -2559,6 +2831,56 @@ static void tcp_mtup_probe_success(struct sock *sk, struct sk_buff *skb)
 	tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
 }
 
+/* Do a simple retransmit without using the backoff mechanisms in
+ * tcp_timer. This is used for path mtu discovery.
+ * The socket is already locked here.
+ */
+void tcp_simple_retransmit(struct sock *sk)
+{
+	const struct inet_connection_sock *icsk = inet_csk(sk);
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct sk_buff *skb;
+	unsigned int mss = tcp_current_mss(sk, 0);
+	u32 prior_lost = tp->lost_out;
+
+	tcp_for_write_queue(skb, sk) {
+		if (skb == tcp_send_head(sk))
+			break;
+		if (tcp_skb_seglen(skb) > mss &&
+		    !(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) {
+			if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
+				TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
+				tp->retrans_out -= tcp_skb_pcount(skb);
+			}
+			tcp_skb_mark_lost_uncond_verify(tp, skb);
+		}
+	}
+
+	tcp_clear_retrans_hints_partial(tp);
+
+	if (prior_lost == tp->lost_out)
+		return;
+
+	if (tcp_is_reno(tp))
+		tcp_limit_reno_sacked(tp);
+
+	tcp_verify_left_out(tp);
+
+	/* Don't muck with the congestion window here.
+	 * Reason is that we do not increase amount of _data_
+	 * in network, but units changed and effective
+	 * cwnd/ssthresh really reduced now.
+	 */
+	if (icsk->icsk_ca_state != TCP_CA_Loss) {
+		tp->high_seq = tp->snd_nxt;
+		tp->snd_ssthresh = tcp_current_ssthresh(sk);
+		tp->prior_ssthresh = 0;
+		tp->undo_marker = 0;
+		tcp_set_ca_state(sk, TCP_CA_Loss);
+	}
+	tcp_xmit_retransmit_queue(sk);
+}
+
 /* Process an event, which can update packets-in-flight not trivially.
  * Main goal of this function is to calculate new estimate for left_out,
  * taking into account both packets sitting in receiver's buffer and
@@ -2730,6 +3052,13 @@ static void tcp_fastretrans_alert(struct sock *sk, int pkts_acked, int flag)
 	tcp_xmit_retransmit_queue(sk);
 }
 
+static void tcp_valid_rtt_meas(struct sock *sk, u32 seq_rtt)
+{
+	tcp_rtt_estimator(sk, seq_rtt);
+	tcp_set_rto(sk);
+	inet_csk(sk)->icsk_backoff = 0;
+}
+
 /* Read draft-ietf-tcplw-high-performance before mucking
  * with this code. (Supersedes RFC1323)
  */
@@ -2751,11 +3080,8 @@ static void tcp_ack_saw_tstamp(struct sock *sk, int flag)
 	 * in window is lost... Voila.	 			--ANK (010210)
 	 */
 	struct tcp_sock *tp = tcp_sk(sk);
-	const __u32 seq_rtt = tcp_time_stamp - tp->rx_opt.rcv_tsecr;
-	tcp_rtt_estimator(sk, seq_rtt);
-	tcp_set_rto(sk);
-	inet_csk(sk)->icsk_backoff = 0;
-	tcp_bound_rto(sk);
+
+	tcp_valid_rtt_meas(sk, tcp_time_stamp - tp->rx_opt.rcv_tsecr);
 }
 
 static void tcp_ack_no_tstamp(struct sock *sk, u32 seq_rtt, int flag)
@@ -2772,10 +3098,7 @@ static void tcp_ack_no_tstamp(struct sock *sk, u32 seq_rtt, int flag)
 	if (flag & FLAG_RETRANS_DATA_ACKED)
 		return;
 
-	tcp_rtt_estimator(sk, seq_rtt);
-	tcp_set_rto(sk);
-	inet_csk(sk)->icsk_backoff = 0;
-	tcp_bound_rto(sk);
+	tcp_valid_rtt_meas(sk, seq_rtt);
 }
 
 static inline void tcp_ack_update_rtt(struct sock *sk, const int flag,