path: root/net/ipv4/tcp_timer.c
diff options
authorYuchung Cheng <ycheng@google.com>2019-04-29 15:46:17 -0700
committerDavid S. Miller <davem@davemloft.net>2019-05-01 11:47:54 -0400
commit8c3cfe19feac41065bb88bc14b36c318b26847a9 (patch)
tree6351df311bfcfeb02f6a45ef549d62aa0062263a /net/ipv4/tcp_timer.c
parenttcp: undo init congestion window on false SYNACK timeout (diff)
tcp: lower congestion window on Fast Open SYNACK timeout
TCP sender would use congestion window of 1 packet on the second SYN and SYNACK timeout except passive TCP Fast Open. This makes passive TFO too aggressive and unfair during congestion at handshake. This patch fixes this issue so TCP (fast open or not, passive or active) always conforms to the RFC6298. Note that tcp_enter_loss() is called only once during recurring timeouts. This is because during handshake, high_seq and snd_una are the same so tcp_enter_loss() would incorrect set the undo state variables multiple times. Signed-off-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to '')
1 files changed, 3 insertions, 0 deletions
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index f0c86398e6a7..2ac23da42dd2 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -393,6 +393,9 @@ static void tcp_fastopen_synack_timer(struct sock *sk)
+ /* Lower cwnd after certain SYNACK timeout like tcp_init_transfer() */
+ if (icsk->icsk_retransmits == 1)
+ tcp_enter_loss(sk);
/* XXX (TFO) - Unlike regular SYN-ACK retransmit, we ignore error
* returned from rtx_syn_ack() to make it more persistent like
* regular retransmit because if the child socket has been accepted