netfilter: nf_nat: fix NAT issue in 2.6.30.4+
Vitezslav Samel discovered that since 2.6.30.4+ active FTP can not work
over NAT. The "cause" of the problem was a fix of unacknowledged data
detection with NAT (commit a3a9f79e361e864f0e9d75ebe2a0cb43d17c4272).
However, actually, that fix uncovered a long standing bug in TCP conntrack:
when NAT was enabled, we simply updated the max of the right edge of
the segments we have seen (td_end), by the offset NAT produced with
changing IP/port in the data. However, we did not update the other parameter
(td_maxend) which is affected by the NAT offset. Thus that could drift
away from the correct value and thus resulted breaking active FTP.
The patch below fixes the issue by *not* updating the conntrack parameters
from NAT, but instead taking into account the NAT offsets in conntrack in a
consistent way. (Updating from NAT would be more harder and expensive because
it'd need to re-calculate parameters we already calculated in conntrack.)
Signed-off-by: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/netfilter/nf_nat_helper.c b/net/ipv4/netfilter/nf_nat_helper.c
index 09172a6..f9520fa 100644
--- a/net/ipv4/netfilter/nf_nat_helper.c
+++ b/net/ipv4/netfilter/nf_nat_helper.c
@@ -73,6 +73,28 @@
DUMP_OFFSET(this_way);
}
+/* Get the offset value, for conntrack */
+s16 nf_nat_get_offset(const struct nf_conn *ct,
+ enum ip_conntrack_dir dir,
+ u32 seq)
+{
+ struct nf_conn_nat *nat = nfct_nat(ct);
+ struct nf_nat_seq *this_way;
+ s16 offset;
+
+ if (!nat)
+ return 0;
+
+ this_way = &nat->seq[dir];
+ spin_lock_bh(&nf_nat_seqofs_lock);
+ offset = after(seq, this_way->correction_pos)
+ ? this_way->offset_after : this_way->offset_before;
+ spin_unlock_bh(&nf_nat_seqofs_lock);
+
+ return offset;
+}
+EXPORT_SYMBOL_GPL(nf_nat_get_offset);
+
/* Frobs data inside this packet, which is linear. */
static void mangle_contents(struct sk_buff *skb,
unsigned int dataoff,
@@ -189,11 +211,6 @@
adjust_tcp_sequence(ntohl(tcph->seq),
(int)rep_len - (int)match_len,
ct, ctinfo);
- /* Tell TCP window tracking about seq change */
- nf_conntrack_tcp_update(skb, ip_hdrlen(skb),
- ct, CTINFO2DIR(ctinfo),
- (int)rep_len - (int)match_len);
-
nf_conntrack_event_cache(IPCT_NATSEQADJ, ct);
}
return 1;
@@ -415,12 +432,7 @@
tcph->seq = newseq;
tcph->ack_seq = newack;
- if (!nf_nat_sack_adjust(skb, tcph, ct, ctinfo))
- return 0;
-
- nf_conntrack_tcp_update(skb, ip_hdrlen(skb), ct, dir, seqoff);
-
- return 1;
+ return nf_nat_sack_adjust(skb, tcph, ct, ctinfo);
}
/* Setup NAT on this expected conntrack so it follows master. */