Commit 93e68020 authored by Ilpo Järvinen's avatar Ilpo Järvinen Committed by David S. Miller
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[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: default avatarIlpo Järvinen <>
Signed-off-by: default avatarDavid S. Miller <>
parent a6963a6b
...@@ -1247,8 +1247,13 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_ ...@@ -1247,8 +1247,13 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
else else
} 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; continue;
} }
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