From: Yuchung Cheng Date: Thu, 31 Jan 2013 19:16:46 +0000 (-0800) Subject: tcp: detect SYN/data drop when F-RTO is disabled X-Git-Tag: v3.7.8~10 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3005cf62aac8c1b68c0201ead876b30a6c0f9ddd;p=thirdparty%2Fkernel%2Fstable.git tcp: detect SYN/data drop when F-RTO is disabled [ Upstream commit 66555e92fb7a619188c02cceae4bbc414f15f96d ] On receiving the SYN-ACK, Fast Open checks icsk_retransmit for SYN retransmission to detect SYN/data drops. But if F-RTO is disabled, icsk_retransmit is reset at step D of tcp_fastretrans_alert() ( under tcp_ack()) before tcp_rcv_fastopen_synack(). The fix is to use total_retrans instead which accounts for SYN retransmission regardless the use of F-RTO. Signed-off-by: Yuchung Cheng Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 181fc8234a529..765db33e60454 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -5639,8 +5639,7 @@ static bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack, * the remote receives only the retransmitted (regular) SYNs: either * the original SYN-data or the corresponding SYN-ACK is lost. */ - syn_drop = (cookie->len <= 0 && data && - inet_csk(sk)->icsk_retransmits); + syn_drop = (cookie->len <= 0 && data && tp->total_retrans); tcp_fastopen_cache_set(sk, mss, cookie, syn_drop);