3 files changed, 16 insertions, 11 deletions

diff --git a/include/net/netfilter/nf_conntrack.h b/include/net/netfilter/nf_conntrack.h
index a632689b61b4..cbdd6284996d 100644
--- a/include/net/netfilter/nf_conntrack.h
+++ b/include/net/netfilter/nf_conntrack.h
@@ -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;
diff --git a/net/ipv4/netfilter/nf_nat_helper.c b/net/ipv4/netfilter/nf_nat_helper.c
index 155c008626c8..09172a65d9b6 100644
--- a/net/ipv4/netfilter/nf_nat_helper.c
+++ b/net/ipv4/netfilter/nf_nat_helper.c
@@ -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;
 }
diff --git a/net/netfilter/nf_conntrack_proto_tcp.c b/net/netfilter/nf_conntrack_proto_tcp.c
index 33fc0a443f3d..97a82ba75376 100644
--- a/net/netfilter/nf_conntrack_proto_tcp.c
+++ b/net/netfilter/nf_conntrack_proto_tcp.c
@@ -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);