Merge branch 'tcp-revert-a-F-RTO-extension-due-to-broken-middle-boxes'
Yuchung Cheng says: ==================== tcp: revert a F-RTO extension due to broken middle-boxes This patch series reverts a (non-standard) TCP F-RTO extension that aimed to detect more spurious timeouts. Unfortunately it could result in poor performance due to broken middle-boxes that modify TCP packets. E.g. https://www.spinics.net/lists/netdev/msg484154.html We believe the best and simplest solution is to just revert the change. ==================== Signed-off-by: David S. Miller <davem@davemloft.net>
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55e84dd7ec
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@ -1971,11 +1971,6 @@ void tcp_enter_loss(struct sock *sk)
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/* F-RTO RFC5682 sec 3.1 step 1: retransmit SND.UNA if no previous
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* loss recovery is underway except recurring timeout(s) on
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* the same SND.UNA (sec 3.2). Disable F-RTO on path MTU probing
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*
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* In theory F-RTO can be used repeatedly during loss recovery.
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* In practice this interacts badly with broken middle-boxes that
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* falsely raise the receive window, which results in repeated
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* timeouts and stop-and-go behavior.
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*/
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tp->frto = net->ipv4.sysctl_tcp_frto &&
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(new_recovery || icsk->icsk_retransmits) &&
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@ -2631,18 +2626,14 @@ static void tcp_process_loss(struct sock *sk, int flag, bool is_dupack,
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tcp_try_undo_loss(sk, false))
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return;
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/* The ACK (s)acks some never-retransmitted data meaning not all
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* the data packets before the timeout were lost. Therefore we
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* undo the congestion window and state. This is essentially
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* the operation in F-RTO (RFC5682 section 3.1 step 3.b). Since
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* a retransmitted skb is permantly marked, we can apply such an
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* operation even if F-RTO was not used.
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if (tp->frto) { /* F-RTO RFC5682 sec 3.1 (sack enhanced version). */
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/* Step 3.b. A timeout is spurious if not all data are
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* lost, i.e., never-retransmitted data are (s)acked.
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*/
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if ((flag & FLAG_ORIG_SACK_ACKED) &&
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tcp_try_undo_loss(sk, tp->undo_marker))
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tcp_try_undo_loss(sk, true))
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return;
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if (tp->frto) { /* F-RTO RFC5682 sec 3.1 (sack enhanced version). */
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if (after(tp->snd_nxt, tp->high_seq)) {
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if (flag & FLAG_DATA_SACKED || is_dupack)
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tp->frto = 0; /* Step 3.a. loss was real */
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