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authorYuchung Cheng <ycheng@google.com>2017-08-04 06:38:51 +0300
committerDavid S. Miller <davem@davemloft.net>2017-08-07 07:25:10 +0300
commit4faf783998b8cb88294e9df89032f473f8771b78 (patch)
tree0ad450f18cbf6c23f23e9f181a4d4ee5c6a99b7a /include/linux/tcp.h
parent10377ba7673d19e28d92846955d51f49acd25c35 (diff)
downloadlinux-4faf783998b8cb88294e9df89032f473f8771b78.tar.xz
tcp: fix cwnd undo in Reno and HTCP congestion controls
Using ssthresh to revert cwnd is less reliable when ssthresh is bounded to 2 packets. This patch uses an existing variable in TCP "prior_cwnd" that snapshots the cwnd right before entering fast recovery and RTO recovery in Reno. This fixes the issue discussed in netdev thread: "A buggy behavior for Linux TCP Reno and HTCP" https://www.spinics.net/lists/netdev/msg444955.html Suggested-by: Neal Cardwell <ncardwell@google.com> Reported-by: Wei Sun <unlcsewsun@gmail.com> Signed-off-by: Yuchung Cheng <ncardwell@google.com> Signed-off-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/linux/tcp.h')
-rw-r--r--include/linux/tcp.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index d7389ea36e10..267164a1d559 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -258,7 +258,7 @@ struct tcp_sock {
u32 snd_cwnd_clamp; /* Do not allow snd_cwnd to grow above this */
u32 snd_cwnd_used;
u32 snd_cwnd_stamp;
- u32 prior_cwnd; /* Congestion window at start of Recovery. */
+ u32 prior_cwnd; /* cwnd right before starting loss recovery */
u32 prr_delivered; /* Number of newly delivered packets to
* receiver in Recovery. */
u32 prr_out; /* Total number of pkts sent during Recovery. */