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tcp: undo on DSACK during recovery

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If the receiver supports DSACK, sender can detect false recoveries and
revert cwnd reductions triggered by either severe network reordering or
concurrent reordering and loss event.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Yuchung Cheng 2013-05-29 14:20:14 +00:00 committed by David S. Miller
parent 7026b912f9
commit c7d9d6a185
1 changed files with 7 additions and 1 deletions
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8
net/ipv4/tcp_input.c
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@ -2315,7 +2315,7 @@ static bool tcp_try_undo_recovery(struct sock *sk)
}
/* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
static void tcp_try_undo_dsack(struct sock *sk)
static bool tcp_try_undo_dsack(struct sock *sk)
{
struct tcp_sock *tp = tcp_sk(sk);
@ -2323,7 +2323,9 @@ static void tcp_try_undo_dsack(struct sock *sk)
DBGUNDO(sk, "D-SACK");
tcp_undo_cwnd_reduction(sk, false);
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPDSACKUNDO);
return true;
}
return false;
}
/* We can clear retrans_stamp when there are no retransmissions in the
@ -2751,6 +2753,10 @@ static void tcp_fastretrans_alert(struct sock *sk, const int acked,
do_lost = tcp_is_reno(tp) ||
tcp_fackets_out(tp) > tp->reordering;
}
if (tcp_try_undo_dsack(sk)) {
tcp_try_keep_open(sk);
return;
}
break;
case TCP_CA_Loss:
tcp_process_loss(sk, flag, is_dupack);