From bd14b1b2e29bd6812597f896dde06eaf7c6d2f24 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 4 May 2012 05:14:02 +0000 Subject: tcp: be more strict before accepting ECN negociation MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit It appears some networks play bad games with the two bits reserved for ECN. This can trigger false congestion notifications and very slow transferts. Since RFC 3168 (6.1.1) forbids SYN packets to carry CT bits, we can disable TCP ECN negociation if it happens we receive mangled CT bits in the SYN packet. Signed-off-by: Eric Dumazet Cc: Perry Lorier Cc: Matt Mathis Cc: Yuchung Cheng Cc: Neal Cardwell Cc: Wilmer van der Gaast Cc: Ankur Jain Cc: Tom Herbert Cc: Dave Täht Acked-by: Neal Cardwell Signed-off-by: David S. Miller --- net/ipv4/tcp_ipv4.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'net/ipv4') diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index cf97e9821d7..4ff5e1f70d1 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -1368,7 +1368,7 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb) goto drop_and_free; if (!want_cookie || tmp_opt.tstamp_ok) - TCP_ECN_create_request(req, tcp_hdr(skb)); + TCP_ECN_create_request(req, skb); if (want_cookie) { isn = cookie_v4_init_sequence(sk, skb, &req->mss); -- cgit v1.2.3