netfilter 44/62: nf_nat: support mangling a single TCP packet multiple times

Patrick McHardy
2010-02-16T14:56:20Z

commit 010c0b9f34a4c567b431f8b49a58b7332ed42e47
Author: Patrick McHardy <kaber@trash.net>
Date: Thu Feb 11 12:27:09 2010 +0100

netfilter: nf_nat: support mangling a single TCP packet multiple times

nf_nat_mangle_tcp_packet() can currently only handle a single mangling
per window because it only maintains two sequence adjustment positions:
the one before the last adjustment and the one after.

This patch makes sequence number adjustment tracking in
nf_nat_mangle_tcp_packet() optional and allows a helper to manually
update the offsets after the packet has been fully handled.

Signed-off-by: Patrick McHardy <kaber@trash.net>

diff --git a/include/net/netfilter/nf_nat_helper.h b/include/net/netfilter/nf_nat_helper.h
index 4222220..02bb6c2 100644
--- a/include/net/netfilter/nf_nat_helper.h
+++ b/include/net/netfilter/nf_nat_helper.h
@@ -7,13 +7,27 @@
struct sk_buff;

/* These return true or false. */
-extern int nf_nat_mangle_tcp_packet(struct sk_buff *skb,
- struct nf_conn *ct,
- enum ip_conntrack_info ctinfo,
- unsigned int match_offset,
- unsigned int match_len,
- const char *rep_buffer,
- unsigned int rep_len);
+extern int __nf_nat_mangle_tcp_packet(struct sk_buff *skb,
+ struct nf_conn *ct,
+ enum ip_conntrack_info ctinfo,
+ unsigned int match_offset,
+ unsigned int match_len,
+ const char *rep_buffer,
+ unsigned int rep_len, bool adjust);
+
+static inline int nf_nat_mangle_tcp_packet(struct sk_buff *skb,
+ struct nf_conn *ct,
+ enum ip_conntrack_info ctinfo,
+ unsigned int match_offset,
+ unsigned int match_len,
+ const char *rep_buffer,
+ unsigned int rep_len)
+{
+ return __nf_nat_mangle_tcp_packet(skb, ct, ctinfo,
+ match_offset, match_len,
+ rep_buffer, rep_len, true);
+}
+
extern int nf_nat_mangle_udp_packet(struct sk_buff *skb,
struct nf_conn *ct,
enum ip_conntrack_info ctinfo,
@@ -21,6 +35,10 @@ extern int nf_nat_mangle_udp_packet(struct sk_buff *skb,
unsigned int match_len,
const char *rep_buffer,
unsigned int rep_len);
+
+extern void nf_nat_set_seq_adjust(struct nf_conn *ct,
+ enum ip_conntrack_info ctinfo,
+ __be32 seq, s16 off);
extern int nf_nat_seq_adjust(struct sk_buff *skb,
struct nf_conn *ct,
enum ip_conntrack_info ctinfo);
diff --git a/net/ipv4/netfilter/nf_nat_helper.c b/net/ipv4/netfilter/nf_nat_helper.c
index 7f10a6b..4b6af4b 100644
--- a/net/ipv4/netfilter/nf_nat_helper.c
+++ b/net/ipv4/netfilter/nf_nat_helper.c
@@ -141,6 +141,17 @@ static int enlarge_skb(struct sk_buff *skb, unsigned int extra)
return 1;
}

+void nf_nat_set_seq_adjust(struct nf_conn *ct, enum ip_conntrack_info ctinfo,
+ __be32 seq, s16 off)
+{
+ if (!off)
+ return;
+ set_bit(IPS_SEQ_ADJUST_BIT, &ct->status);
+ adjust_tcp_sequence(ntohl(seq), off, ct, ctinfo);
+ nf_conntrack_event_cache(IPCT_NATSEQADJ, ct);
+}
+EXPORT_SYMBOL_GPL(nf_nat_set_seq_adjust);
+
/* Generic function for mangling variable-length address changes inside
* NATed TCP connections (like the PORT XXX,XXX,XXX,XXX,XXX,XXX
* command in FTP).
@@ -149,14 +160,13 @@ static int enlarge_skb(struct sk_buff *skb, unsigned int extra)
* skb enlargement, ...
*
* */
-int
-nf_nat_mangle_tcp_packet(struct sk_buff *skb,
- struct nf_conn *ct,
- enum ip_conntrack_info ctinfo,
- unsigned int match_offset,
- unsigned int match_len,
- const char *rep_buffer,
- unsigned int rep_len)
+int __nf_nat_mangle_tcp_packet(struct sk_buff *skb,
+ struct nf_conn *ct,
+ enum ip_conntrack_info ctinfo,
+ unsigned int match_offset,
+ unsigned int match_len,
+ const char *rep_buffer,
+ unsigned int rep_len, bool adjust)
{
struct rtable *rt = skb_rtable(skb);
struct iphdr *iph;
@@ -202,16 +212,13 @@ nf_nat_mangle_tcp_packet(struct sk_buff *skb,
inet_proto_csum_replace2(&tcph->check, skb,
htons(oldlen), htons(datalen), 1);

- if (rep_len != match_len) {
- set_bit(IPS_SEQ_ADJUST_BIT, &ct->status);
- adjust_tcp_sequence(ntohl(tcph->seq),
- (int)rep_len - (int)match_len,
- ct, ctinfo);
- nf_conntrack_event_cache(IPCT_NATSEQADJ, ct);
- }
+ if (adjust && rep_len != match_len)
+ nf_nat_set_seq_adjust(ct, ctinfo, tcph->seq,
+ (int)rep_len - (int)match_len);
+
return 1;
}
-EXPORT_SYMBOL(nf_nat_mangle_tcp_packet);
+EXPORT_SYMBOL(__nf_nat_mangle_tcp_packet);

/* Generic function for mangling variable-length address changes inside
* NATed UDP connections (like the CONNECT DATA XXXXX MESG XXXXX INDEX XXXXX