tcp: undo on DSACK during recovery
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>
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index c35b227..907311c 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2315,7 +2315,7 @@
}
/* 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 @@
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 @@
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);