| From | Greg Kroah-Hartman <> | Subject | [ 52/61] tcp: detect SYN/data drop when F-RTO is disabled | Date | Tue, 12 Feb 2013 12:35:12 -0800 |
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3.7-stable review patch. If anyone has any objections, please let me know.
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From: Yuchung Cheng <ycheng@google.com>
[ 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 <ycheng@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- net/ipv4/tcp_input.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
--- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -5639,8 +5639,7 @@ static bool tcp_rcv_fastopen_synack(stru * 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);
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