Commit b7b0ed91 authored May 18, 2015 by Yuchung Cheng Committed by David S. Miller May 19, 2015

tcp: don't over-send F-RTO probes



After sending the new data packets to probe (step 2), F-RTO may
incorrectly send more probes if the next ACK advances SND_UNA and
does not sack new packet. However F-RTO RFC 5682 probes at most
once. This bug may cause sender to always send new data instead of
repairing holes, inducing longer HoL blocking on the receiver for
the application.

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 da34ac76

net/ipv4/tcp_input.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -2710,9 +2710,9 @@ static void tcp_process_loss(struct sock *sk, int flag, bool is_dupack)
		tcp_try_undo_loss(sk, true))
		return;

		if (after(tp->snd_nxt, tp->high_seq) &&
		(flag & FLAG_DATA_SACKED \|\| is_dupack)) {
		tp->frto = 0; /* Loss was real: 2nd part of step 3.a */
		if (after(tp->snd_nxt, tp->high_seq)) {
		if (flag & FLAG_DATA_SACKED \|\| is_dupack)
		tp->frto = 0; /* Step 3.a. loss was real */
		} else if (flag & FLAG_SND_UNA_ADVANCED && !recovered) {
		tp->high_seq = tp->snd_nxt;
		__tcp_push_pending_frames(sk, tcp_current_mss(sk),

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