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: Neal Cardwell <ncardwell@google.com>
Acked-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index f772aaa..b49e418 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3788,6 +3788,10 @@
return 1;
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
* being used to time the probes, and is probably far higher than
* it needs to be for normal retransmission.