From 3acf3ec3f4b0fd4263989f2e4227bbd1c42b5fe1 Mon Sep 17 00:00:00 2001 From: Lawrence Brakmo Date: Tue, 27 Sep 2016 19:03:37 -0700 Subject: [PATCH] tcp: Change txhash on every SYN and RTO retransmit The current code changes txhash (flowlables) on every retransmitted SYN/ACK, but only after the 2nd retransmitted SYN and only after tcp_retries1 RTO retransmits. With this patch: 1) txhash is changed with every SYN retransmits 2) txhash is changed with every RTO. The result is that we can start re-routing around failed (or very congested paths) as soon as possible. Otherwise application health checks may fail and the connection may be terminated before we start to change txhash. v4: Removed sysctl, txhash is changed for all RTOs v3: Removed text saying default value of sysctl is 0 (it is 100) v2: Added sysctl documentation and cleaned code Tested with packetdrill tests Signed-off-by: Lawrence Brakmo Signed-off-by: David S. Miller --- net/ipv4/tcp_timer.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c index f712b411f6ed..3ea1cf804748 100644 --- a/net/ipv4/tcp_timer.c +++ b/net/ipv4/tcp_timer.c @@ -192,6 +192,8 @@ static int tcp_write_timeout(struct sock *sk) if (tp->syn_data && icsk->icsk_retransmits == 1) NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENACTIVEFAIL); + } else if (!tp->syn_data && !tp->syn_fastopen) { + sk_rethink_txhash(sk); } retry_until = icsk->icsk_syn_retries ? : net->ipv4.sysctl_tcp_syn_retries; syn_set = true; @@ -213,6 +215,8 @@ static int tcp_write_timeout(struct sock *sk) tcp_mtu_probing(icsk, sk); dst_negative_advice(sk); + } else { + sk_rethink_txhash(sk); } retry_until = net->ipv4.sysctl_tcp_retries2; -- 2.11.0