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[TCP]: reno sacked_out count fix

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From: "Angelo P. Castellani" <angelo.castellani+lkml@gmail.com>

Using NewReno, if a sk_buff is timed out and is accounted as lost_out,
it should also be removed from the sacked_out.

This is necessary because recovery using NewReno fast retransmit could
take up to a lot RTTs and the sk_buff RTO can expire without actually
being really lost.

left_out = sacked_out + lost_out
in_flight = packets_out - left_out + retrans_out

Using NewReno without this patch, on very large network losses,
left_out becames bigger than packets_out + retrans_out (!!).

For this reason unsigned integer in_flight overflows to 2^32 - something.

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Angelo P. Castellani 2006-05-16 21:42:11 -07:00 committed by David S. Miller
parent d8fd0a7316
commit 8872d8e1c4
1 changed files with 2 additions and 0 deletions
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2
net/ipv4/tcp_input.c
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@ -1662,6 +1662,8 @@ static void tcp_update_scoreboard(struct sock *sk, struct tcp_sock *tp)
if (!(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) {
TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
tp->lost_out += tcp_skb_pcount(skb);
if (IsReno(tp))
tcp_remove_reno_sacks(sk, tp, tcp_skb_pcount(skb) + 1);
/* clear xmit_retrans hint */
if (tp->retransmit_skb_hint &&