From 59a08cba6a604a265e45e9b970e372554cf46627 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Ilpo=20J=C3=A4rvinen?= Date: Sat, 28 Feb 2009 04:44:28 +0000 Subject: [PATCH] tcp: fix lost_cnt_hint miscounts MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit It is possible that lost_cnt_hint gets underflow in tcp_clean_rtx_queue because the cumulative ACK can cover the segment where lost_skb_hint points to only partially, which means that the hint is not cleared, opposite to what my (earlier) comment claimed. Also I don't agree what I ended up writing about non-trivial case there to be what I intented to say. It was not supposed to happen that the hint won't get cleared and we underflow in any scenario. In general, this is quite hard to trigger in practice. Signed-off-by: Ilpo Järvinen Signed-off-by: David S. Miller --- net/ipv4/tcp_input.c | 13 +++++-------- 1 file changed, 5 insertions(+), 8 deletions(-) diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index c28976a7e596..3f2f09091bcf 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -3273,18 +3273,15 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets, if (tcp_is_reno(tp)) { tcp_remove_reno_sacks(sk, pkts_acked); } else { + int delta; + /* Non-retransmitted hole got filled? That's reordering */ if (reord < prior_fackets) tcp_update_reordering(sk, tp->fackets_out - reord, 0); - /* No need to care for underflows here because - * the lost_skb_hint gets NULLed if we're past it - * (or something non-trivial happened) - */ - if (tcp_is_fack(tp)) - tp->lost_cnt_hint -= pkts_acked; - else - tp->lost_cnt_hint -= prior_sacked - tp->sacked_out; + delta = tcp_is_fack(tp) ? pkts_acked : + prior_sacked - tp->sacked_out; + tp->lost_cnt_hint -= min(tp->lost_cnt_hint, delta); } tp->fackets_out -= min(pkts_acked, tp->fackets_out); -- 2.20.1