Commit f82b681a authored Jul 13, 2015 by Yuchung Cheng Committed by David S. Miller Jul 15, 2015

tcp: don't use F-RTO on non-recurring timeouts



Currently F-RTO may repeatedly send new data packets on non-recurring
timeouts in CA_Loss mode. This is a bug because F-RTO (RFC5682)
should only be used on either new recovery or recurring timeouts.

This exacerbates the recovery progress during frequent timeout &
repair, because we prioritize sending new data packets instead of
repairing the holes when the bandwidth is already scarce.

Fix it by correcting the test of a new recovery episode.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 5ebc7846

net/ipv4/tcp_input.c

+1 −2

Original line number	Diff line number	Diff line
		@@ -1917,14 +1917,13 @@ void tcp_enter_loss(struct sock *sk)
		const struct inet_connection_sock *icsk = inet_csk(sk);
		struct tcp_sock *tp = tcp_sk(sk);
		struct sk_buff *skb;
		bool new_recovery = false;
		bool new_recovery = icsk->icsk_ca_state < TCP_CA_Recovery;
		bool is_reneg; /* is receiver reneging on SACKs? */

		/* Reduce ssthresh if it has not yet been made inside this window. */
		if (icsk->icsk_ca_state <= TCP_CA_Disorder \|\|
		!after(tp->high_seq, tp->snd_una) \|\|
		(icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) {
		new_recovery = true;
		tp->prior_ssthresh = tcp_current_ssthresh(sk);
		tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
		tcp_ca_event(sk, CA_EVENT_LOSS);

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