From: Ilpo Järvinen Date: Wed, 26 Sep 2007 05:46:50 +0000 (-0700) Subject: [TCP]: Reordered ACK's (old) SACKs not included to discarded MIB X-Git-Tag: v2.6.24-rc1~1454^2~358 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=93e680202929802558f783fbd96c41697ae65472;p=linux-2.6 [TCP]: Reordered ACK's (old) SACKs not included to discarded MIB In case of ACK reordering, the SACK block might be valid in it's time but is already obsoleted since we've received another kind of confirmation about arrival of the segments through snd_una advancement of an earlier packet. I didn't bother to build distinguishing of valid and invalid SACK blocks but simply made reordered SACK blocks that are too old always not counted regardless of their "real" validity which could be determined by using the ack field of the reordered packet (won't be significant IMHO). DSACKs can very well be considered useful even in this situation, so won't do any of this for them. Signed-off-by: Ilpo Järvinen Signed-off-by: David S. Miller --- diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 4c10d9cad2..4866e75e98 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -1247,8 +1247,13 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_ NET_INC_STATS_BH(LINUX_MIB_TCPDSACKIGNOREDNOUNDO); else NET_INC_STATS_BH(LINUX_MIB_TCPDSACKIGNOREDOLD); - } else + } else { + /* Don't count olds caused by ACK reordering */ + if ((TCP_SKB_CB(ack_skb)->ack_seq != tp->snd_una) && + !after(end_seq, tp->snd_una)) + continue; NET_INC_STATS_BH(LINUX_MIB_TCPSACKDISCARD); + } continue; }