From d4761754b4fb2ef8d9a1e9d121c4bec84e1fe292 Mon Sep 17 00:00:00 2001 From: Yousuk Seung Date: Thu, 7 Dec 2017 13:41:34 -0800 Subject: tcp: invalidate rate samples during SACK reneging Mark tcp_sock during a SACK reneging event and invalidate rate samples while marked. Such rate samples may overestimate bw by including packets that were SACKed before reneging. < ack 6001 win 10000 sack 7001:38001 < ack 7001 win 0 sack 8001:38001 // Reneg detected > seq 7001:8001 // RTO, SACK cleared. < ack 38001 win 10000 In above example the rate sample taken after the last ack will count 7001-38001 as delivered while the actual delivery rate likely could be much lower i.e. 7001-8001. This patch adds a new field tcp_sock.sack_reneg and marks it when we declare SACK reneging and entering TCP_CA_Loss, and unmarks it after the last rate sample was taken before moving back to TCP_CA_Open. This patch also invalidates rate samples taken while tcp_sock.is_sack_reneg is set. Fixes: b9f64820fb22 ("tcp: track data delivery rate for a TCP connection") Signed-off-by: Yousuk Seung Signed-off-by: Neal Cardwell Signed-off-by: Yuchung Cheng Acked-by: Soheil Hassas Yeganeh Acked-by: Eric Dumazet Acked-by: Priyaranjan Jha Signed-off-by: David S. Miller --- net/ipv4/tcp_rate.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) (limited to 'net/ipv4/tcp_rate.c') diff --git a/net/ipv4/tcp_rate.c b/net/ipv4/tcp_rate.c index 3330a370d306..c61240e43923 100644 --- a/net/ipv4/tcp_rate.c +++ b/net/ipv4/tcp_rate.c @@ -106,7 +106,7 @@ void tcp_rate_skb_delivered(struct sock *sk, struct sk_buff *skb, /* Update the connection delivery information and generate a rate sample. */ void tcp_rate_gen(struct sock *sk, u32 delivered, u32 lost, - struct rate_sample *rs) + bool is_sack_reneg, struct rate_sample *rs) { struct tcp_sock *tp = tcp_sk(sk); u32 snd_us, ack_us; @@ -124,8 +124,12 @@ void tcp_rate_gen(struct sock *sk, u32 delivered, u32 lost, rs->acked_sacked = delivered; /* freshly ACKed or SACKed */ rs->losses = lost; /* freshly marked lost */ - /* Return an invalid sample if no timing information is available. */ - if (!rs->prior_mstamp) { + /* Return an invalid sample if no timing information is available or + * in recovery from loss with SACK reneging. Rate samples taken during + * a SACK reneging event may overestimate bw by including packets that + * were SACKed before the reneg. + */ + if (!rs->prior_mstamp || is_sack_reneg) { rs->delivered = -1; rs->interval_us = -1; return; -- cgit v1.2.3