[PATCH 1/2] [TCP]: Add highest_sack seqno, points to globally highest SACK

[Ilpo Järvinen]

It is maintained only in during slowpath of tcp_ack(). In most
cases this seqno is available in the last ACK but there is no
guarantee for that. The new fast recovery loss marking algorithm
needs this as entry point.

Signed-off-by: Ilpo Järvinen <[EMAIL PROTECTED]>
---
 include/linux/tcp.h      |    2 ++
 net/ipv4/tcp_input.c     |   10 ++++++++++
 net/ipv4/tcp_minisocks.c |    1 +
 3 files changed, 13 insertions(+), 0 deletions(-)

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index b73687a..807fc96 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -320,6 +320,8 @@ #endif
 
        struct tcp_sack_block_wire recv_sack_cache[4];
 
+       u32     highest_sack;   /* Start seq of globally highest revd SACK 
(valid only in slowpath) */
+
        /* from STCP, retrans queue hinting */
        struct sk_buff* lost_skb_hint;
 
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 22d0bb0..827171a 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1188,6 +1188,10 @@ tcp_sacktag_write_queue(struct sock *sk,
 
                                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;
                        } else {
                                if (dup_sack && (sacked&TCPCB_RETRANS))
                                        reord = min(fack_count, reord);
@@ -2762,10 +2766,16 @@ static int tcp_ack(struct sock *sk, stru
                else
                        NET_INC_STATS_BH(LINUX_MIB_TCPPUREACKS);
 
+               /* Transition from fast to slow path, is this correct way? */
+               if (tp->pred_flags)
+                       tp->highest_sack = tp->snd_una;
+
                flag |= tcp_ack_update_window(sk, tp, skb, ack, ack_seq);
 
                if (TCP_SKB_CB(skb)->sacked)
                        flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una);
+               else if (before(tp->highest_sack, tp->snd_una))
+                       tp->highest_sack = tp->snd_una;
 
                if (TCP_ECN_rcv_ecn_echo(tp, skb->h.th))
                        flag |= FLAG_ECE;
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 0a57c36..68d0000 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -389,6 +389,7 @@ struct sock *tcp_create_openreq_child(st
                newtp->pred_flags = 0;
                newtp->rcv_wup = newtp->copied_seq = newtp->rcv_nxt = 
treq->rcv_isn + 1;
                newtp->snd_sml = newtp->snd_una = newtp->snd_nxt = 
treq->snt_isn + 1;
+               newtp->highest_sack = treq->snt_isn + 1;
 
                tcp_prequeue_init(newtp);
 
-- 
1.4.2