tcp: fix infinite cwnd in tcp_complete_cwr() (1cebce36) · Commits · e / devices / android_kernel_xiaomi_markw

When the cwnd reduction is done, ssthresh may be infinite if TCP enters CWR via ECN or F-RTO. If cwnd is not undone, i.e., undo_marker is set, tcp_complete_cwr() falsely set cwnd to the infinite ssthresh value. The correct operation is to keep cwnd intact because it has been updated in ECN or F-RTO. Signed-off-by:

Yuchung Cheng <ycheng@google.com> Acked-by:

Neal Cardwell <ncardwell@google.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

net/ipv4/tcp_input.c

+6 −3

Original line number	Diff line number	Diff line
		@@ -2868,12 +2868,15 @@ static inline void tcp_complete_cwr(struct sock *sk)

		/* Do not moderate cwnd if it's already undone in cwr or recovery. */
		if (tp->undo_marker) {
		if (inet_csk(sk)->icsk_ca_state == TCP_CA_CWR)
		if (inet_csk(sk)->icsk_ca_state == TCP_CA_CWR) {
		tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
		else /* PRR */
		tp->snd_cwnd_stamp = tcp_time_stamp;
		} else if (tp->snd_ssthresh < TCP_INFINITE_SSTHRESH) {
		/* PRR algorithm. */
		tp->snd_cwnd = tp->snd_ssthresh;
		tp->snd_cwnd_stamp = tcp_time_stamp;
		}
		}
		tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR);
		}