This is a note to let you know that I've just added the patch titled
tcp: fix false reordering signal in tcp_shifted_skb
to the 3.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tcp-fix-false-reordering-signal-in-tcp_shifted_skb.patch
and it can be found in the queue-3.0 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From bd31d3812b91196b37c5fecb280b9b1d8338367a Mon Sep 17 00:00:00 2001
From: Neal Cardwell <[email protected]>
Date: Sun, 26 Feb 2012 10:06:19 +0000
Subject: tcp: fix false reordering signal in tcp_shifted_skb
From: Neal Cardwell <[email protected]>
[ Upstream commit 4c90d3b30334833450ccbb02f452d4972a3c3c3f ]
When tcp_shifted_skb() shifts bytes from the skb that is currently
pointed to by 'highest_sack' then the increment of
TCP_SKB_CB(skb)->seq implicitly advances tcp_highest_sack_seq(). This
implicit advancement, combined with the recent fix to pass the correct
SACKed range into tcp_sacktag_one(), caused tcp_sacktag_one() to think
that the newly SACKed range was before the tcp_highest_sack_seq(),
leading to a call to tcp_update_reordering() with a degree of
reordering matching the size of the newly SACKed range (typically just
1 packet, which is a NOP, but potentially larger).
This commit fixes this by simply calling tcp_sacktag_one() before the
TCP_SKB_CB(skb)->seq advancement that can advance our notion of the
highest SACKed sequence.
Correspondingly, we can simplify the code a little now that
tcp_shifted_skb() should update the lost_cnt_hint in all cases where
skb == tp->lost_skb_hint.
Signed-off-by: Neal Cardwell <[email protected]>
Acked-by: Yuchung Cheng <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
net/ipv4/tcp_input.c | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1385,8 +1385,16 @@ static int tcp_shifted_skb(struct sock *
BUG_ON(!pcount);
- /* Adjust hint for FACK. Non-FACK is handled in tcp_sacktag_one(). */
- if (tcp_is_fack(tp) && (skb == tp->lost_skb_hint))
+ /* Adjust counters and hints for the newly sacked sequence
+ * range but discard the return value since prev is already
+ * marked. We must tag the range first because the seq
+ * advancement below implicitly advances
+ * tcp_highest_sack_seq() when skb is highest_sack.
+ */
+ tcp_sacktag_one(sk, state, TCP_SKB_CB(skb)->sacked,
+ start_seq, end_seq, dup_sack, pcount);
+
+ if (skb == tp->lost_skb_hint)
tp->lost_cnt_hint += pcount;
TCP_SKB_CB(prev)->end_seq += shifted;
@@ -1412,12 +1420,6 @@ static int tcp_shifted_skb(struct sock *
skb_shinfo(skb)->gso_type = 0;
}
- /* Adjust counters and hints for the newly sacked sequence range but
- * discard the return value since prev is already marked.
- */
- tcp_sacktag_one(sk, state, TCP_SKB_CB(skb)->sacked,
- start_seq, end_seq, dup_sack, pcount);
-
/* Difference in this won't matter, both ACKed by the same cumul. ACK */
TCP_SKB_CB(prev)->sacked |= (TCP_SKB_CB(skb)->sacked &
TCPCB_EVER_RETRANS);
Patches currently in stable-queue which might be from [email protected] are
queue-3.0/tcp-fix-tcp_shift_skb_data-to-not-shift-sacked-data-below-snd_una.patch
queue-3.0/tcp-don-t-fragment-sacked-skbs-in-tcp_mark_head_lost.patch
queue-3.0/tcp-fix-false-reordering-signal-in-tcp_shifted_skb.patch
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