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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>
This commit is contained in:
Patrick McHardy 2009-06-29 14:07:56 +02:00
parent 308ff823eb
commit a3a9f79e36
3 changed files with 16 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
include/net/netfilter/nf_conntrack.h
View File

@ -258,8 +258,8 @@ static inline bool nf_ct_kill(struct nf_conn *ct)
/* Update TCP window tracking data when NAT mangles the packet */
extern void nf_conntrack_tcp_update(const struct sk_buff *skb,
unsigned int dataoff,
struct nf_conn *ct,
int dir);
struct nf_conn *ct, int dir,
s16 offset);
/* Fake conntrack entry for untracked connections */
extern struct nf_conn nf_conntrack_untracked;

17
net/ipv4/netfilter/nf_nat_helper.c
View File

@ -191,7 +191,8 @@ nf_nat_mangle_tcp_packet(struct sk_buff *skb,
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 @@ nf_nat_seq_adjust(struct sk_buff *skb,
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 @@ nf_nat_seq_adjust(struct sk_buff *skb,
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 @@ nf_nat_seq_adjust(struct sk_buff *skb,
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;
}

6
net/netfilter/nf_conntrack_proto_tcp.c
View File

@ -720,8 +720,8 @@ static bool tcp_in_window(const struct nf_conn *ct,
/* Caller must linearize skb at tcp header. */
void nf_conntrack_tcp_update(const struct sk_buff *skb,
unsigned int dataoff,
struct nf_conn *ct,
int dir)
struct nf_conn *ct, int dir,
s16 offset)
{
const struct tcphdr *tcph = (const void *)skb->data + dataoff;
const struct ip_ct_tcp_state *sender = &ct->proto.tcp.seen[dir];
@ -734,7 +734,7 @@ void nf_conntrack_tcp_update(const struct sk_buff *skb,
/*
* We have to worry for the ack in the reply packet only...
*/
if (after(end, ct->proto.tcp.seen[dir].td_end))
if (ct->proto.tcp.seen[dir].td_end + offset == end)
ct->proto.tcp.seen[dir].td_end = end;
ct->proto.tcp.last_end = end;
spin_unlock_bh(&ct->lock);