Commit 5628adf1 authored by Neal Cardwell's avatar Neal Cardwell Committed by David S. Miller

tcp: use DSACKs that arrive when packets_out is 0

The bug: Senders ignored DSACKs after recovery when there were no
outstanding packets (a common scenario for HTTP servers).

The change: when there are no outstanding packets (the "no_queue" goto
label), call tcp_fastretrans_alert() in order to use DSACKs to undo
congestion window reductions.

Other patches in this series will provide other changes that are
necessary to fully fix this problem.
Signed-off-by: default avatarNeal Cardwell <ncardwell@google.com>
Acked-by: default avatarIlpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 7d2b55f8
...@@ -3788,6 +3788,10 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag) ...@@ -3788,6 +3788,10 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
return 1; return 1;
no_queue: no_queue:
/* If data was DSACKed, see if we can undo a cwnd reduction. */
if (flag & FLAG_DSACKING_ACK)
tcp_fastretrans_alert(sk, pkts_acked, newly_acked_sacked,
is_dupack, flag);
/* If this ack opens up a zero window, clear backoff. It was /* If this ack opens up a zero window, clear backoff. It was
* being used to time the probes, and is probably far higher than * being used to time the probes, and is probably far higher than
* it needs to be for normal retransmission. * it needs to be for normal retransmission.
......
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