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authorYuchung Cheng <ycheng@google.com>2017-08-03 20:38:51 -0700
committerDavid S. Miller <davem@davemloft.net>2017-08-06 21:25:10 -0700
commit4faf783998b8cb88294e9df89032f473f8771b78 (patch)
tree0ad450f18cbf6c23f23e9f181a4d4ee5c6a99b7a /net/ipv4/tcp_cong.c
parent10377ba7673d19e28d92846955d51f49acd25c35 (diff)
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 'net/ipv4/tcp_cong.c')
-rw-r--r--net/ipv4/tcp_cong.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
index fde983f6376b..c2b174469645 100644
--- a/net/ipv4/tcp_cong.c
+++ b/net/ipv4/tcp_cong.c
@@ -456,7 +456,7 @@ u32 tcp_reno_undo_cwnd(struct sock *sk)
{
const struct tcp_sock *tp = tcp_sk(sk);
- return max(tp->snd_cwnd, tp->snd_ssthresh << 1);
+ return max(tp->snd_cwnd, tp->prior_cwnd);
}
EXPORT_SYMBOL_GPL(tcp_reno_undo_cwnd);