| Message ID | 1348323537-30310-3-git-send-email-ncardwell@google.com |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
From: Neal Cardwell <ncardwell@google.com> Date: Sat, 22 Sep 2012 10:18:56 -0400 > Previously, when using TCP Fast Open a server would return from > tcp_check_req() before updating snt_synack based on TCP timestamp echo > replies and whether or not we've retransmitted the SYNACK. The result > was that (a) for TFO connections using timestamps we used an incorrect > baseline SYNACK send time (tcp_time_stamp of SYNACK send instead of > rcv_tsecr), and (b) for TFO connections that do not have TCP > timestamps but retransmit the SYNACK we took a SYNACK RTT sample when > we should not take a sample. > > This fix merely moves the snt_synack update logic a bit earlier in the > function, so that connections using TCP Fast Open will properly do > these updates when the ACK for the SYNACK arrives. > > Moving this snt_synack update logic means that with TCP_DEFER_ACCEPT > enabled we do a few instructions of wasted work on each bare ACK, but > that seems OK. > > Signed-off-by: Neal Cardwell <ncardwell@google.com> Applied. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c index 5792577..27536ba 100644 --- a/net/ipv4/tcp_minisocks.c +++ b/net/ipv4/tcp_minisocks.c @@ -692,6 +692,12 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb, if (!(flg & TCP_FLAG_ACK)) return NULL; + /* Got ACK for our SYNACK, so update baseline for SYNACK RTT sample. */ + if (tmp_opt.saw_tstamp && tmp_opt.rcv_tsecr) + tcp_rsk(req)->snt_synack = tmp_opt.rcv_tsecr; + else if (req->retrans) /* don't take RTT sample if retrans && ~TS */ + tcp_rsk(req)->snt_synack = 0; + /* For Fast Open no more processing is needed (sk is the * child socket). */ @@ -705,10 +711,6 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb, NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPDEFERACCEPTDROP); return NULL; } - if (tmp_opt.saw_tstamp && tmp_opt.rcv_tsecr) - tcp_rsk(req)->snt_synack = tmp_opt.rcv_tsecr; - else if (req->retrans) /* don't take RTT sample if retrans && ~TS */ - tcp_rsk(req)->snt_synack = 0; /* OK, ACK is valid, create big socket and * feed this segment to it. It will repeat all
Previously, when using TCP Fast Open a server would return from tcp_check_req() before updating snt_synack based on TCP timestamp echo replies and whether or not we've retransmitted the SYNACK. The result was that (a) for TFO connections using timestamps we used an incorrect baseline SYNACK send time (tcp_time_stamp of SYNACK send instead of rcv_tsecr), and (b) for TFO connections that do not have TCP timestamps but retransmit the SYNACK we took a SYNACK RTT sample when we should not take a sample. This fix merely moves the snt_synack update logic a bit earlier in the function, so that connections using TCP Fast Open will properly do these updates when the ACK for the SYNACK arrives. Moving this snt_synack update logic means that with TCP_DEFER_ACCEPT enabled we do a few instructions of wasted work on each bare ACK, but that seems OK. Signed-off-by: Neal Cardwell <ncardwell@google.com> --- net/ipv4/tcp_minisocks.c | 10 ++++++---- 1 files changed, 6 insertions(+), 4 deletions(-)