From f34d1955dff5a5769d24614d137003f0316406f3 Mon Sep 17 00:00:00 2001 From: Stephen Hemminger Date: Tue, 7 Aug 2007 18:29:05 -0700 Subject: [PATCH] [TCP]: H-TCP maxRTT estimation at startup Small patch to H-TCP from Douglas Leith. Fix estimation of maxRTT. The original code ignores rtt measurements during slow start (via the check tp->snd_ssthresh < 0xFFFF) yet this is probably a good time to try to estimate max rtt as delayed acking is disabled and slow start will only exit on a loss which presumably corresponds to a maxrtt measurement. Second, the original code (via the check htcp_ccount(ca) > 3) ignores rtt data during what it estimates to be the first 3 round-trip times. This seems like an unnecessary check now that the RCV timestamp are no longer used for rtt estimation. Signed-off-by: Stephen Hemminger Signed-off-by: David S. Miller --- net/ipv4/tcp_htcp.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/net/ipv4/tcp_htcp.c b/net/ipv4/tcp_htcp.c index b66556c..5215691 100644 --- a/net/ipv4/tcp_htcp.c +++ b/net/ipv4/tcp_htcp.c @@ -79,7 +79,6 @@ static u32 htcp_cwnd_undo(struct sock *sk) static inline void measure_rtt(struct sock *sk, u32 srtt) { const struct inet_connection_sock *icsk = inet_csk(sk); - const struct tcp_sock *tp = tcp_sk(sk); struct htcp *ca = inet_csk_ca(sk); /* keep track of minimum RTT seen so far, minRTT is zero at first */ @@ -87,8 +86,7 @@ static inline void measure_rtt(struct sock *sk, u32 srtt) ca->minRTT = srtt; /* max RTT */ - if (icsk->icsk_ca_state == TCP_CA_Open - && tp->snd_ssthresh < 0xFFFF && htcp_ccount(ca) > 3) { + if (icsk->icsk_ca_state == TCP_CA_Open) { if (ca->maxRTT < ca->minRTT) ca->maxRTT = ca->minRTT; if (ca->maxRTT < srtt -- 2.7.4