diff options
| -rw-r--r-- | net/ipv4/tcp_input.c | 33 |
1 files changed, 19 insertions, 14 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 4ad75b8c4fee..9469ce384d3b 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -1939,7 +1939,6 @@ void tcp_enter_loss(struct sock *sk) struct tcp_sock *tp = tcp_sk(sk); struct net *net = sock_net(sk); struct sk_buff *skb; - bool new_recovery = icsk->icsk_ca_state < TCP_CA_Recovery; bool is_reneg; /* is receiver reneging on SACKs? */ bool mark_lost; @@ -2000,13 +1999,15 @@ void tcp_enter_loss(struct sock *sk) tp->high_seq = tp->snd_nxt; tcp_ecn_queue_cwr(tp); - /* F-RTO RFC5682 sec 3.1 step 1: retransmit SND.UNA if no previous - * loss recovery is underway except recurring timeout(s) on - * the same SND.UNA (sec 3.2). Disable F-RTO on path MTU probing + /* F-RTO RFC5682 sec 3.1 step 1 mandates to disable F-RTO + * if a previous recovery is underway, otherwise it may incorrectly + * call a timeout spurious if some previously retransmitted packets + * are s/acked (sec 3.2). We do not apply that retriction since + * retransmitted skbs are permanently tagged with TCPCB_EVER_RETRANS + * so FLAG_ORIG_SACK_ACKED is always correct. But we do disable F-RTO + * on PTMU discovery to avoid sending new data. */ - tp->frto = sysctl_tcp_frto && - (new_recovery || icsk->icsk_retransmits) && - !inet_csk(sk)->icsk_mtup.probe_size; + tp->frto = sysctl_tcp_frto && !inet_csk(sk)->icsk_mtup.probe_size; } /* If ACK arrived pointing to a remembered SACK, it means that our @@ -2740,14 +2741,18 @@ static void tcp_process_loss(struct sock *sk, int flag, bool is_dupack, tcp_try_undo_loss(sk, false)) return; - if (tp->frto) { /* F-RTO RFC5682 sec 3.1 (sack enhanced version). */ - /* Step 3.b. A timeout is spurious if not all data are - * lost, i.e., never-retransmitted data are (s)acked. - */ - if ((flag & FLAG_ORIG_SACK_ACKED) && - tcp_try_undo_loss(sk, true)) - return; + /* The ACK (s)acks some never-retransmitted data meaning not all + * the data packets before the timeout were lost. Therefore we + * undo the congestion window and state. This is essentially + * the operation in F-RTO (RFC5682 section 3.1 step 3.b). Since + * a retransmitted skb is permantly marked, we can apply such an + * operation even if F-RTO was not used. + */ + if ((flag & FLAG_ORIG_SACK_ACKED) && + tcp_try_undo_loss(sk, tp->undo_marker)) + return; + if (tp->frto) { /* F-RTO RFC5682 sec 3.1 (sack enhanced version). */ if (after(tp->snd_nxt, tp->high_seq)) { if (flag & FLAG_DATA_SACKED || is_dupack) tp->frto = 0; /* Step 3.a. loss was real */ |