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[TCP]: Allow minimum RTO to be configurable via routing metrics.

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Cell phone networks do link layer retransmissions and other
things that cause unnecessary timeout retransmits.  So allow
the minimum RTO to be inflated per-route to deal with this.

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2007-08-30 22:10:28 -07:00
parent 378be2c083
commit 05bb1fad1c
2 changed files with 14 additions and 2 deletions
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2
include/linux/rtnetlink.h
View file

@ -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
};

14
net/ipv4/tcp_input.c
View file

@ -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;
}
}