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netfilter: nf_nat: avoid double seq_adjust for loopback

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Avoid double seq adjustment for loopback traffic
because it causes silent repetition of TCP data. One
example is passive FTP with DNAT rule and difference in the
length of IP addresses.

	This patch adds check if packet is sent and
received via loopback device. As the same conntrack is
used both for outgoing and incoming direction, we restrict
seq adjustment to happen only in POSTROUTING.

Signed-off-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Patrick McHardy <kaber@trash.net>
This commit is contained in:
Julian Anastasov
2011-06-16 17:29:22 +02:00
committed by Patrick McHardy
parent 2c38de4c1f
commit 42c1edd345
2 changed files with 9 additions and 1 deletions
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4
net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c
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@@ -121,7 +121,9 @@ static unsigned int ipv4_confirm(unsigned int hooknum,
return ret;
}
if (test_bit(IPS_SEQ_ADJUST_BIT, &ct->status)) {
/* adjust seqs for loopback traffic only in outgoing direction */
if (test_bit(IPS_SEQ_ADJUST_BIT, &ct->status) &&
!nf_is_loopback_packet(skb)) {
typeof(nf_nat_seq_adjust_hook) seq_adjust;
seq_adjust = rcu_dereference(nf_nat_seq_adjust_hook);