From 6adb4f733e9996b4fd68a6db50dd51bd2463ccac Mon Sep 17 00:00:00 2001 From: =?utf8?q?Ilpo=20J=C3=A4rvinen?= Date: Mon, 7 Apr 2008 22:33:57 -0700 Subject: [PATCH] [TCP]: Don't allow FRTO to take place while MTU is being probed MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit MTU probe can cause some remedies for FRTO because the normal packet ordering may be violated allowing FRTO to make a wrong decision (it might not be that serious threat for anything though). Thus it's safer to not run FRTO while MTU probe is underway. It seems that the basic FRTO variant should also look for an skb at probe_seq.start to check if that's retransmitted one but I didn't implement it now (plain seqno in window check isn't robust against wraparounds). Signed-off-by: Ilpo Järvinen Signed-off-by: David S. Miller --- net/ipv4/tcp_input.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index b4812c3cbbcf..5119856017ab 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -1691,11 +1691,16 @@ static inline void tcp_reset_reno_sack(struct tcp_sock *tp) int tcp_use_frto(struct sock *sk) { const struct tcp_sock *tp = tcp_sk(sk); + const struct inet_connection_sock *icsk = inet_csk(sk); struct sk_buff *skb; if (!sysctl_tcp_frto) return 0; + /* MTU probe and F-RTO won't really play nicely along currently */ + if (icsk->icsk_mtup.probe_size) + return 0; + if (IsSackFrto()) return 1; -- 2.20.1