1 /* (C) 1999-2001 Paul `Rusty' Russell
2 * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License version 2 as
6 * published by the Free Software Foundation.
9 #include <linux/types.h>
10 #include <linux/init.h>
12 #include <linux/tcp.h>
14 #include <linux/netfilter.h>
15 #include <linux/netfilter/nfnetlink_conntrack.h>
16 #include <net/netfilter/nf_nat.h>
17 #include <net/netfilter/nf_nat_rule.h>
18 #include <net/netfilter/nf_nat_protocol.h>
19 #include <net/netfilter/nf_nat_core.h>
21 static u_int16_t tcp_port_rover
;
24 tcp_unique_tuple(struct nf_conntrack_tuple
*tuple
,
25 const struct nf_nat_range
*range
,
26 enum nf_nat_manip_type maniptype
,
27 const struct nf_conn
*ct
)
29 return nf_nat_proto_unique_tuple(tuple
, range
, maniptype
, ct
,
34 tcp_manip_pkt(struct sk_buff
*skb
,
35 unsigned int iphdroff
,
36 const struct nf_conntrack_tuple
*tuple
,
37 enum nf_nat_manip_type maniptype
)
39 const struct iphdr
*iph
= (struct iphdr
*)(skb
->data
+ iphdroff
);
41 unsigned int hdroff
= iphdroff
+ iph
->ihl
*4;
43 __be16
*portptr
, newport
, oldport
;
44 int hdrsize
= 8; /* TCP connection tracking guarantees this much */
46 /* this could be a inner header returned in icmp packet; in such
47 cases we cannot update the checksum field since it is outside of
48 the 8 bytes of transport layer headers we are guaranteed */
49 if (skb
->len
>= hdroff
+ sizeof(struct tcphdr
))
50 hdrsize
= sizeof(struct tcphdr
);
52 if (!skb_make_writable(skb
, hdroff
+ hdrsize
))
55 iph
= (struct iphdr
*)(skb
->data
+ iphdroff
);
56 hdr
= (struct tcphdr
*)(skb
->data
+ hdroff
);
58 if (maniptype
== IP_NAT_MANIP_SRC
) {
59 /* Get rid of src ip and src pt */
61 newip
= tuple
->src
.u3
.ip
;
62 newport
= tuple
->src
.u
.tcp
.port
;
63 portptr
= &hdr
->source
;
65 /* Get rid of dst ip and dst pt */
67 newip
= tuple
->dst
.u3
.ip
;
68 newport
= tuple
->dst
.u
.tcp
.port
;
75 if (hdrsize
< sizeof(*hdr
))
78 inet_proto_csum_replace4(&hdr
->check
, skb
, oldip
, newip
, 1);
79 inet_proto_csum_replace2(&hdr
->check
, skb
, oldport
, newport
, 0);
83 const struct nf_nat_protocol nf_nat_protocol_tcp
= {
84 .protonum
= IPPROTO_TCP
,
86 .manip_pkt
= tcp_manip_pkt
,
87 .in_range
= nf_nat_proto_in_range
,
88 .unique_tuple
= tcp_unique_tuple
,
89 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
90 .range_to_nlattr
= nf_nat_proto_range_to_nlattr
,
91 .nlattr_to_range
= nf_nat_proto_nlattr_to_range
,