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[TCP]: Adjust Reno SACK estimate in tcp_fragment

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Since the introduction of TSO pcount a year ago, it has been possible
for tcp_fragment() to cause packets_out to decrease.  Prior to that,
tcp_retrans_try_collapse() was the only way for that to happen on the
retransmission path.

When this happens with Reno, it is possible for sasked_out to become
invalid because it is only an estimate and not tied to any particular
packet on the retransmission queue.

Therefore we need to adjust sacked_out as well as left_out in the Reno
case.  The following patch does exactly that.

This bug is pretty difficult to trigger in practice though since you
need a SACKless peer with a retransmission that occurs just as the
cached MTU value expires.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Herbert Xu 2005-09-22 23:32:56 -07:00 committed by David S. Miller
parent e484585ec3
commit 83ca28befc
1 changed files with 9 additions and 0 deletions
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9
net/ipv4/tcp_output.c
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@ -509,7 +509,16 @@ int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len, unsigned int mss
tp->lost_out -= diff;
tp->left_out -= diff;
}
if (diff > 0) {
/* Adjust Reno SACK estimate. */
if (!tp->rx_opt.sack_ok) {
tp->sacked_out -= diff;
if ((int)tp->sacked_out < 0)
tp->sacked_out = 0;
tcp_sync_left_out(tp);
}
tp->fackets_out -= diff;
if ((int)tp->fackets_out < 0)
tp->fackets_out = 0;