Commit 0ce294d8 authored Dec 07, 2017 by Yuchung Cheng Committed by David S. Miller Dec 08, 2017

tcp: correctly test congestion state in RACK



RACK does not test the loss recovery state correctly to compute
the reordering window. It assumes if lost_out is zero then TCP is
not in loss recovery. But it can be zero during recovery before
calling tcp_rack_detect_loss(): when an ACK acknowledges all
packets marked lost before receiving this ACK, but has not yet
to discover new ones by tcp_rack_detect_loss(). The fix is to
simply test the congestion state directly.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Reviewed-by: Neal Cardwell <ncardwell@google.com>
Reviewed-by: Priyaranjan Jha <priyarjha@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 2edbdb31

net/ipv4/tcp_recovery.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -55,7 +55,8 @@ static void tcp_rack_detect_loss(struct sock sk, u32 reo_timeout)
		* to queuing or delayed ACKs.
		*/
		reo_wnd = 1000;
		if ((tp->rack.reord \|\| !tp->lost_out) && min_rtt != ~0U) {
		if ((tp->rack.reord \|\| inet_csk(sk)->icsk_ca_state < TCP_CA_Recovery) &&
		min_rtt != ~0U) {
		reo_wnd = max((min_rtt >> 2) * tp->rack.reo_wnd_steps, reo_wnd);
		reo_wnd = min(reo_wnd, tp->srtt_us >> 3);
		}