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>
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 9faf775..243d674 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2710,9 +2710,9 @@
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),
