tcp: back retransmit_high when it over-estimated

If lost skb is sacked, we might have nothing to retransmit
as high as the retransmit_high is pointing to, so place
it lower to avoid unnecessary walking.

This is mainly for the case where high L'ed skbs gets sacked.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 239cea7b6c0e85469f381a2be6bfa865a3cc03d1..8f9793a37b618540d27ec965b5489a3d1ff7a171 100644 (file)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2035,16 +2035,22 @@ void tcp_xmit_retransmit_queue(struct sock *sk)
        struct tcp_sock *tp = tcp_sk(sk);
        struct sk_buff *skb;
        struct sk_buff *hole = NULL;
+       u32 last_lost;
        int mib_idx;
        int fwd_rexmitting = 0;
 
        if (!tp->lost_out)
                tp->retransmit_high = tp->snd_una;
 
-       if (tp->retransmit_skb_hint)
+       if (tp->retransmit_skb_hint) {
                skb = tp->retransmit_skb_hint;
-       else
+               last_lost = TCP_SKB_CB(skb)->end_seq;
+               if (after(last_lost, tp->retransmit_high))
+                       last_lost = tp->retransmit_high;
+       } else {
                skb = tcp_write_queue_head(sk);
+               last_lost = tp->snd_una;
+       }
 
        /* First pass: retransmit lost packets. */
        tcp_for_write_queue_from(skb, sk) {
@@ -2073,6 +2079,7 @@ begin_fwd:
                        mib_idx = LINUX_MIB_TCPFORWARDRETRANS;
 
                } else if (!before(TCP_SKB_CB(skb)->seq, tp->retransmit_high)) {
+                       tp->retransmit_high = last_lost;
                        if (!tcp_can_forward_retransmit(sk))
                                break;
                        /* Backtrack if necessary to non-L'ed skb */
@@ -2089,6 +2096,7 @@ begin_fwd:
                        continue;
 
                } else {
+                       last_lost = TCP_SKB_CB(skb)->end_seq;
                        if (icsk->icsk_ca_state != TCP_CA_Loss)
                                mib_idx = LINUX_MIB_TCPFASTRETRANS;
                        else