From d1a54c6a0a3f9c2c4ef71982d89b8571bd9eaa51 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= Date: Wed, 21 Feb 2007 23:11:57 -0800 Subject: [TCP] FRTO: Reverse RETRANS bit clearing logic MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Previously RETRANS bits were cleared on the entry to FRTO. We postpone that into tcp_enter_frto_loss, which is really the place were the clearing should be done anyway. This allows simplification of the logic from a clearing loop to the head skb clearing only. Besides, the other changes made in the previous patches to tcp_use_frto made it impossible for the non-SACKed FRTO to be entered if other than the head has been rexmitted. With SACK-enhanced FRTO (and Appendix B), however, there can be a number retransmissions in flight when RTO expires (same thing could happen before this patchset also with non-SACK FRTO). To not introduce any jumpiness into the packet counting during FRTO, instead of clearing RETRANS bits from skbs during entry, do it later on. Signed-off-by: Ilpo Järvinen Signed-off-by: David S. Miller --- net/ipv4/tcp_input.c | 35 +++++++++++++++++++++++------------ 1 file changed, 23 insertions(+), 12 deletions(-) (limited to 'net/ipv4/tcp_input.c') diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index a283fc12186..3ef7e9e0796 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -1268,7 +1268,11 @@ int tcp_use_frto(struct sock *sk) /* RTO occurred, but do not yet enter Loss state. Instead, defer RTO * recovery a bit and use heuristics in tcp_process_frto() to detect if - * the RTO was spurious. + * the RTO was spurious. Only clear SACKED_RETRANS of the head here to + * keep retrans_out counting accurate (with SACK F-RTO, other than head + * may still have that bit set); TCPCB_LOST and remaining SACKED_RETRANS + * bits are handled if the Loss state is really to be entered (in + * tcp_enter_frto_loss). * * Do like tcp_enter_loss() would; when RTO expires the second time it * does: @@ -1289,17 +1293,13 @@ void tcp_enter_frto(struct sock *sk) tcp_ca_event(sk, CA_EVENT_FRTO); } - /* Have to clear retransmission markers here to keep the bookkeeping - * in shape, even though we are not yet in Loss state. - * If something was really lost, it is eventually caught up - * in tcp_enter_frto_loss. - */ - tp->retrans_out = 0; tp->undo_marker = tp->snd_una; tp->undo_retrans = 0; - sk_stream_for_retrans_queue(skb, sk) { + skb = skb_peek(&sk->sk_write_queue); + if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) { TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; + tp->retrans_out -= tcp_skb_pcount(skb); } tcp_sync_left_out(tp); @@ -1313,7 +1313,7 @@ void tcp_enter_frto(struct sock *sk) * which indicates that we should follow the traditional RTO recovery, * i.e. mark everything lost and do go-back-N retransmission. */ -static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments) +static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments, int flag) { struct tcp_sock *tp = tcp_sk(sk); struct sk_buff *skb; @@ -1322,10 +1322,21 @@ static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments) tp->sacked_out = 0; tp->lost_out = 0; tp->fackets_out = 0; + tp->retrans_out = 0; sk_stream_for_retrans_queue(skb, sk) { cnt += tcp_skb_pcount(skb); - TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST; + /* + * Count the retransmission made on RTO correctly (only when + * waiting for the first ACK and did not get it)... + */ + if ((tp->frto_counter == 1) && !(flag&FLAG_DATA_ACKED)) { + tp->retrans_out += tcp_skb_pcount(skb); + /* ...enter this if branch just for the first segment */ + flag |= FLAG_DATA_ACKED; + } else { + TCP_SKB_CB(skb)->sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS); + } if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED)) { /* Do not mark those segments lost that were @@ -2550,7 +2561,7 @@ static int tcp_process_frto(struct sock *sk, u32 prior_snd_una, int flag) inet_csk(sk)->icsk_retransmits = 0; if (!before(tp->snd_una, tp->frto_highmark)) { - tcp_enter_frto_loss(sk, tp->frto_counter + 1); + tcp_enter_frto_loss(sk, tp->frto_counter + 1, flag); return 1; } @@ -2562,7 +2573,7 @@ static int tcp_process_frto(struct sock *sk, u32 prior_snd_una, int flag) return 1; if (!(flag&FLAG_DATA_ACKED)) { - tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 0 : 3)); + tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 0 : 3), flag); return 1; } -- cgit v1.2.3