It is going to replace the sack fastpath hint quite soon... :-)

Signed-off-by: Ilpo Järvinen <[EMAIL PROTECTED]>
---
 include/linux/tcp.h   |    6 ++++--
 include/net/tcp.h     |   13 +++++++++++++
 net/ipv4/tcp_input.c  |   11 ++++++-----
 net/ipv4/tcp_output.c |   19 ++++++++++---------
 4 files changed, 33 insertions(+), 16 deletions(-)

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index c5b94c1..0ec6bb6 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -332,8 +332,10 @@ struct tcp_sock {
 
        struct tcp_sack_block_wire recv_sack_cache[4];
 
-       u32     highest_sack;   /* Start seq of globally highest revd SACK
-                                * (validity guaranteed only if sacked_out > 0) 
*/
+       struct sk_buff *highest_sack;   /* highest skb with SACK received
+                                        * (validity guaranteed only if
+                                        * sacked_out > 0)
+                                        */
 
        /* from STCP, retrans queue hinting */
        struct sk_buff* lost_skb_hint;
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 92049e6..aead90a 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1306,6 +1306,19 @@ static inline int tcp_write_queue_empty(struct sock *sk)
        return skb_queue_empty(&sk->sk_write_queue);
 }
 
+/* Start sequence of the highest skb with SACKed bit, valid only if
+ * sacked > 0 or when the caller has ensured validity by itself.
+ */
+static inline u32 tcp_highest_sack_seq(struct sock *sk)
+{
+       struct tcp_sock *tp = tcp_sk(sk);
+
+       if (WARN_ON(!tp->sacked_out &&
+           tp->highest_sack != tcp_write_queue_head(sk)))
+               return tp->snd_una;
+       return TCP_SKB_CB(tp->highest_sack)->seq;
+}
+
 /* /proc */
 enum tcp_seq_states {
        TCP_SEQ_STATE_LISTENING,
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 9d3d390..39d6a6a 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1238,10 +1238,11 @@ int tcp_match_skb_to_sack(struct sock *sk, struct 
sk_buff *skb,
        return in_sack;
 }
 
-static void tcp_sacktag_one(struct sk_buff *skb, struct tcp_sock *tp,
+static void tcp_sacktag_one(struct sk_buff *skb, struct sock *sk,
                            struct tcp_sacktag_state *state, int in_sack,
                            int dup_sack, int fack_count, u32 end_seq)
 {
+       struct tcp_sock *tp = tcp_sk(sk);
        u8 sacked = TCP_SKB_CB(skb)->sacked;
 
        /* Account D-SACK for retransmitted packet. */
@@ -1321,8 +1322,8 @@ static void tcp_sacktag_one(struct sk_buff *skb, struct 
tcp_sock *tp,
                if (fack_count > tp->fackets_out)
                        tp->fackets_out = fack_count;
 
-               if (after(TCP_SKB_CB(skb)->seq, tp->highest_sack)) {
-                       tp->highest_sack = TCP_SKB_CB(skb)->seq;
+               if (after(TCP_SKB_CB(skb)->seq, tcp_highest_sack_seq(sk))) {
+                       tp->highest_sack = skb;
                        state->highest_sack_end_seq = TCP_SKB_CB(skb)->end_seq;
                }
        } else {
@@ -1363,7 +1364,7 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff 
*ack_skb, u32 prior_snd_
        if (!tp->sacked_out) {
                if (WARN_ON(tp->fackets_out))
                        tp->fackets_out = 0;
-               tp->highest_sack = tp->snd_una;
+               tp->highest_sack = tcp_write_queue_head(sk);
        }
 
        found_dup_sack = tcp_check_dsack(tp, ack_skb, sp, num_sacks, 
prior_snd_una);
@@ -1497,7 +1498,7 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff 
*ack_skb, u32 prior_snd_
 
                        fack_count += tcp_skb_pcount(skb);
 
-                       tcp_sacktag_one(skb, tp, &state, in_sack,
+                       tcp_sacktag_one(skb, sk, &state, in_sack,
                                        dup_sack, fack_count, end_seq);
                }
        }
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 324b420..9603de8 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -657,13 +657,15 @@ static void tcp_set_skb_tso_segs(struct sock *sk, struct 
sk_buff *skb, unsigned
  * tweak SACK fastpath hint too as it would overwrite all changes unless
  * hint is also changed.
  */
-static void tcp_adjust_fackets_out(struct tcp_sock *tp, struct sk_buff *skb,
+static void tcp_adjust_fackets_out(struct sock *sk, struct sk_buff *skb,
                                   int decr)
 {
+       struct tcp_sock *tp = tcp_sk(sk);
+
        if (!tp->sacked_out || tcp_is_reno(tp))
                return;
 
-       if (!before(tp->highest_sack, TCP_SKB_CB(skb)->seq))
+       if (!before(tcp_highest_sack_seq(sk), TCP_SKB_CB(skb)->seq))
                tp->fackets_out -= decr;
 
        /* cnt_hint is "off-by-one" compared with fackets_out (see sacktag) */
@@ -712,9 +714,8 @@ int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 
len, unsigned int mss
        TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
        TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
 
-       if (tcp_is_sack(tp) && tp->sacked_out &&
-           (TCP_SKB_CB(skb)->seq == tp->highest_sack))
-               tp->highest_sack = TCP_SKB_CB(buff)->seq;
+       if (tcp_is_sack(tp) && tp->sacked_out && (skb == tp->highest_sack))
+               tp->highest_sack = buff;
 
        /* PSH and FIN should only be set in the second packet. */
        flags = TCP_SKB_CB(skb)->flags;
@@ -772,7 +773,7 @@ int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 
len, unsigned int mss
                        tcp_dec_pcount_approx_int(&tp->sacked_out, diff);
                        tcp_verify_left_out(tp);
                }
-               tcp_adjust_fackets_out(tp, skb, diff);
+               tcp_adjust_fackets_out(sk, skb, diff);
        }
 
        /* Link BUFF into the send queue. */
@@ -1720,7 +1721,7 @@ static void tcp_retrans_try_collapse(struct sock *sk, 
struct sk_buff *skb, int m
                       tcp_skb_pcount(next_skb) != 1);
 
                if (WARN_ON(tcp_is_sack(tp) && tp->sacked_out &&
-                   (TCP_SKB_CB(next_skb)->seq == tp->highest_sack)))
+                   (next_skb == tp->highest_sack)))
                        return;
 
                /* Ok.  We will be able to collapse the packet. */
@@ -1755,7 +1756,7 @@ static void tcp_retrans_try_collapse(struct sock *sk, 
struct sk_buff *skb, int m
                if (tcp_is_reno(tp) && tp->sacked_out)
                        tcp_dec_pcount_approx(&tp->sacked_out, next_skb);
 
-               tcp_adjust_fackets_out(tp, next_skb, tcp_skb_pcount(next_skb));
+               tcp_adjust_fackets_out(sk, next_skb, tcp_skb_pcount(next_skb));
                tp->packets_out -= tcp_skb_pcount(next_skb);
 
                /* changed transmit queue under us so clear hints */
@@ -2036,7 +2037,7 @@ void tcp_xmit_retransmit_queue(struct sock *sk)
                        break;
                tp->forward_skb_hint = skb;
 
-               if (after(TCP_SKB_CB(skb)->seq, tp->highest_sack))
+               if (after(TCP_SKB_CB(skb)->seq, tcp_highest_sack_seq(sk)))
                        break;
 
                if (tcp_packets_in_flight(tp) >= tp->snd_cwnd)
-- 
1.5.0.6

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