From 6065fd0d179b96ddc488c76542349bcb148a95fd Mon Sep 17 00:00:00 2001 From: Yuchung Cheng Date: Thu, 7 Dec 2017 11:33:33 -0800 Subject: tcp: evaluate packet losses upon RTT change RACK skips an ACK unless it advances the most recently delivered TX timestamp (rack.mstamp). Since RACK also uses the most recent RTT to decide if a packet is lost, RACK should still run the loss detection whenever the most recent RTT changes. For example, an ACK that does not advance the timestamp but triggers the cwnd undo due to reordering, would then use the most recent (higher) RTT measurement to detect further losses. Signed-off-by: Yuchung Cheng Reviewed-by: Neal Cardwell Reviewed-by: Priyaranjan Jha Reviewed-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/tcp_recovery.c | 19 ++++++++----------- 1 file changed, 8 insertions(+), 11 deletions(-) (limited to 'net/ipv4/tcp_recovery.c') diff --git a/net/ipv4/tcp_recovery.c b/net/ipv4/tcp_recovery.c index 0c182303e62e..3a81720ac0c4 100644 --- a/net/ipv4/tcp_recovery.c +++ b/net/ipv4/tcp_recovery.c @@ -117,13 +117,8 @@ void tcp_rack_advance(struct tcp_sock *tp, u8 sacked, u32 end_seq, { u32 rtt_us; - if (tp->rack.mstamp && - !tcp_rack_sent_after(xmit_time, tp->rack.mstamp, - end_seq, tp->rack.end_seq)) - return; - rtt_us = tcp_stamp_us_delta(tp->tcp_mstamp, xmit_time); - if (sacked & TCPCB_RETRANS) { + if (rtt_us < tcp_min_rtt(tp) && (sacked & TCPCB_RETRANS)) { /* If the sacked packet was retransmitted, it's ambiguous * whether the retransmission or the original (or the prior * retransmission) was sacked. @@ -134,13 +129,15 @@ void tcp_rack_advance(struct tcp_sock *tp, u8 sacked, u32 end_seq, * so it's at least one RTT (i.e., retransmission is at least * an RTT later). */ - if (rtt_us < tcp_min_rtt(tp)) - return; + return; } - tp->rack.rtt_us = rtt_us; - tp->rack.mstamp = xmit_time; - tp->rack.end_seq = end_seq; tp->rack.advanced = 1; + tp->rack.rtt_us = rtt_us; + if (tcp_rack_sent_after(xmit_time, tp->rack.mstamp, + end_seq, tp->rack.end_seq)) { + tp->rack.mstamp = xmit_time; + tp->rack.end_seq = end_seq; + } } /* We have waited long enough to accommodate reordering. Mark the expired -- cgit v1.2.3