netfilter: tcp conntrack: fix unacknowledged data detection with NAT
When NAT helpers change the TCP packet size, the highest seen sequence
number needs to be corrected. This is currently only done upwards, when
the packet size is reduced the sequence number is unchanged. This causes
TCP conntrack to falsely detect unacknowledged data and decrease the
timeout.
Fix by updating the highest seen sequence number in both directions after
packet mangling.
Tested-by: Krzysztof Piotr Oledzki <ole@ans.pl>
Signed-off-by: Patrick McHardy <kaber@trash.net>
diff --git a/net/ipv4/netfilter/nf_nat_helper.c b/net/ipv4/netfilter/nf_nat_helper.c
index 155c008..09172a6 100644
--- a/net/ipv4/netfilter/nf_nat_helper.c
+++ b/net/ipv4/netfilter/nf_nat_helper.c
@@ -191,7 +191,8 @@
ct, ctinfo);
/* Tell TCP window tracking about seq change */
nf_conntrack_tcp_update(skb, ip_hdrlen(skb),
- ct, CTINFO2DIR(ctinfo));
+ ct, CTINFO2DIR(ctinfo),
+ (int)rep_len - (int)match_len);
nf_conntrack_event_cache(IPCT_NATSEQADJ, ct);
}
@@ -377,6 +378,7 @@
struct tcphdr *tcph;
int dir;
__be32 newseq, newack;
+ s16 seqoff, ackoff;
struct nf_conn_nat *nat = nfct_nat(ct);
struct nf_nat_seq *this_way, *other_way;
@@ -390,15 +392,18 @@
tcph = (void *)skb->data + ip_hdrlen(skb);
if (after(ntohl(tcph->seq), this_way->correction_pos))
- newseq = htonl(ntohl(tcph->seq) + this_way->offset_after);
+ seqoff = this_way->offset_after;
else
- newseq = htonl(ntohl(tcph->seq) + this_way->offset_before);
+ seqoff = this_way->offset_before;
if (after(ntohl(tcph->ack_seq) - other_way->offset_before,
other_way->correction_pos))
- newack = htonl(ntohl(tcph->ack_seq) - other_way->offset_after);
+ ackoff = other_way->offset_after;
else
- newack = htonl(ntohl(tcph->ack_seq) - other_way->offset_before);
+ ackoff = other_way->offset_before;
+
+ newseq = htonl(ntohl(tcph->seq) + seqoff);
+ newack = htonl(ntohl(tcph->ack_seq) - ackoff);
inet_proto_csum_replace4(&tcph->check, skb, tcph->seq, newseq, 0);
inet_proto_csum_replace4(&tcph->check, skb, tcph->ack_seq, newack, 0);
@@ -413,7 +418,7 @@
if (!nf_nat_sack_adjust(skb, tcph, ct, ctinfo))
return 0;
- nf_conntrack_tcp_update(skb, ip_hdrlen(skb), ct, dir);
+ nf_conntrack_tcp_update(skb, ip_hdrlen(skb), ct, dir, seqoff);
return 1;
}