Re: [PATCH] make _minimum_ TCP retransmission timeout configurable take 2
From: David Miller <davem@davemloft.net>
Date: 2007-08-31 05:09:13
Subsystem:
networking [general], networking [tcp], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Neal Cardwell, Linus Torvalds
From: Rick Jones <redacted> Date: Thu, 30 Aug 2007 18:07:13 -0700
Anyhow, I'll try grubbing around the source code (already doing that to see about writing a pet tcp cong module) but if pointers to the likely relevant files were available I could try to help thrash-out the routing metric version. Like I said the consumers of this are a triffle well, "anxious" :)
The change is actually a lot simpler than the sysctl version. In fact it borders on trivial :-) Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/rtnetlink.h b/include/linux/rtnetlink.h
index c91476c..dff3192 100644
--- a/include/linux/rtnetlink.h
+++ b/include/linux/rtnetlink.h@@ -351,6 +351,8 @@ enum #define RTAX_INITCWND RTAX_INITCWND RTAX_FEATURES, #define RTAX_FEATURES RTAX_FEATURES + RTAX_RTO_MIN, +#define RTAX_RTO_MIN RTAX_RTO_MIN __RTAX_MAX };
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 9785df3..1ee7212 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c@@ -555,6 +555,16 @@ static void tcp_event_data_recv(struct sock *sk, struct sk_buff *skb) tcp_grow_window(sk, skb); } +static u32 tcp_rto_min(struct sock *sk) +{ + struct dst_entry *dst = __sk_dst_get(sk); + u32 rto_min = TCP_RTO_MIN; + + if (dst_metric_locked(dst, RTAX_RTO_MIN)) + rto_min = dst->metrics[RTAX_RTO_MIN-1]; + return rto_min; +} + /* Called to compute a smoothed rtt estimate. The data fed to this * routine either comes from timestamps, or from segments that were * known _not_ to have been retransmitted [see Karn/Partridge
@@ -616,13 +626,13 @@ static void tcp_rtt_estimator(struct sock *sk, const __u32 mrtt) if (tp->mdev_max < tp->rttvar) tp->rttvar -= (tp->rttvar-tp->mdev_max)>>2; tp->rtt_seq = tp->snd_nxt; - tp->mdev_max = TCP_RTO_MIN; + tp->mdev_max = tcp_rto_min(sk); } } else { /* no previous measure. */ tp->srtt = m<<3; /* take the measured time to be rtt */ tp->mdev = m<<1; /* make sure rto = 3*rtt */ - tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN); + tp->mdev_max = tp->rttvar = max(tp->mdev, tcp_rto_min(sk)); tp->rtt_seq = tp->snd_nxt; } }