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tcp: TCP Fast Open Server - record retransmits after 3WHS

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When recording the number of SYNACK retransmits for servers using TCP
Fast Open, fix the code to ensure that we copy over the retransmit
count from the request_sock after we receive the ACK that completes
the 3-way handshake.

The story here is similar to that of SYNACK RTT
measurements. Previously we were always doing this in
tcp_v4_syn_recv_sock(). However, for TCP Fast Open connections
tcp_v4_conn_req_fastopen() calls tcp_v4_syn_recv_sock() at the time we
receive the SYN. So for TFO we must copy the final SYNACK retransmit
count in tcp_rcv_state_process().

Note that copying over the SYNACK retransmit count will give us the
correct count since, as is mentioned in a comment in
tcp_retransmit_timer(), before we receive an ACK for our SYN-ACK a TFO
passive connection does not retransmit anything else (e.g., data or
FIN segments).

Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Neal Cardwell 2012-09-22 17:03:47 +00:00 committed by David S. Miller
parent 5894bab7f4
commit 30099b2e9b
1 changed files with 2 additions and 0 deletions
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2
net/ipv4/tcp_input.c
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@ -5985,6 +5985,8 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
*/
if (req) {
tcp_synack_rtt_meas(sk, req);
tp->total_retrans = req->retrans;
reqsk_fastopen_remove(sk, req, false);
} else {
/* Make sure socket is routed, for