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tcp: consolidate SYNACK RTT sampling

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The first patch consolidates SYNACK and other RTT measurement to use a
central function tcp_ack_update_rtt(). A (small) bonus is now SYNACK
RTT measurement happens after PAWS check, potentially reducing the
impact of RTO seeding on bad TCP timestamps values.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Yuchung Cheng
2013-07-22 16:20:45 -07:00
committed by David S. Miller
parent c3f51d5f38
commit 375fe02c91
5 changed files with 14 additions and 21 deletions
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14
net/ipv4/tcp_input.c
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@@ -2853,6 +2853,17 @@ static inline void tcp_ack_update_rtt(struct sock *sk, const int flag,
tcp_ack_no_tstamp(sk, seq_rtt, flag);
}
/* Compute time elapsed between (last) SYNACK and the ACK completing 3WHS. */
static void tcp_synack_rtt_meas(struct sock *sk, struct request_sock *req)
{
struct tcp_sock *tp = tcp_sk(sk);
s32 seq_rtt = -1;
if (tp->lsndtime && !tp->total_retrans)
seq_rtt = tcp_time_stamp - tp->lsndtime;
tcp_ack_update_rtt(sk, FLAG_SYN_ACKED, seq_rtt);
}
static void tcp_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
{
const struct inet_connection_sock *icsk = inet_csk(sk);
@@ -5624,9 +5635,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
* so release it.
*/
if (req) {
tcp_synack_rtt_meas(sk, req);
tp->total_retrans = req->num_retrans;
reqsk_fastopen_remove(sk, req, false);
} else {
/* Make sure socket is routed, for correct metrics. */
@@ -5651,6 +5660,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
tp->snd_una = TCP_SKB_CB(skb)->ack_seq;
tp->snd_wnd = ntohs(th->window) << tp->rx_opt.snd_wscale;
tcp_init_wl(tp, TCP_SKB_CB(skb)->seq);
tcp_synack_rtt_meas(sk, req);
if (tp->rx_opt.tstamp_ok)
tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;