From 3d0d26c7976bf190c3f1d2efbc31462db8246bc0 Mon Sep 17 00:00:00 2001 From: Kenneth Klette Jonassen Date: Sat, 11 Apr 2015 02:17:49 +0200 Subject: [PATCH] tcp: fix bogus RTT for CC when retransmissions are acked Since retransmitted segments are not used for RTT estimation, previously SACKed segments present in the rtx queue are used. This estimation can be several times larger than the actual RTT. When a cumulative ack covers both previously SACKed and retransmitted segments, CC may thus get a bogus RTT. Such segments previously had an RTT estimation in tcp_sacktag_one(), so it seems reasonable to not reuse them in tcp_clean_rtx_queue() at all. Afaik, this has had no effect on SRTT/RTO because of Karn's check. Signed-off-by: Kenneth Klette Jonassen Acked-by: Neal Cardwell Tested-by: Neal Cardwell Acked-by: Yuchung Cheng Signed-off-by: David S. Miller --- net/ipv4/tcp_input.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 031cf72cd05c..a7ef679dd3ea 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -3099,17 +3099,15 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets, if (sacked & TCPCB_SACKED_RETRANS) tp->retrans_out -= acked_pcount; flag |= FLAG_RETRANS_DATA_ACKED; - } else { + } else if (!(sacked & TCPCB_SACKED_ACKED)) { last_ackt = skb->skb_mstamp; WARN_ON_ONCE(last_ackt.v64 == 0); if (!first_ackt.v64) first_ackt = last_ackt; - if (!(sacked & TCPCB_SACKED_ACKED)) { - reord = min(pkts_acked, reord); - if (!after(scb->end_seq, tp->high_seq)) - flag |= FLAG_ORIG_SACK_ACKED; - } + reord = min(pkts_acked, reord); + if (!after(scb->end_seq, tp->high_seq)) + flag |= FLAG_ORIG_SACK_ACKED; } if (sacked & TCPCB_SACKED_ACKED) -- 2.30.2