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 nf_nat_proto_unique_tuple(tuple
, range
, maniptype
, ct
, &tcp_port_rover
);
33 tcp_manip_pkt(struct sk_buff
*skb
,
34 unsigned int iphdroff
,
35 const struct nf_conntrack_tuple
*tuple
,
36 enum nf_nat_manip_type maniptype
)
38 const struct iphdr
*iph
= (struct iphdr
*)(skb
->data
+ iphdroff
);
40 unsigned int hdroff
= iphdroff
+ iph
->ihl
*4;
42 __be16
*portptr
, newport
, oldport
;
43 int hdrsize
= 8; /* TCP connection tracking guarantees this much */
45 /* this could be a inner header returned in icmp packet; in such
46 cases we cannot update the checksum field since it is outside of
47 the 8 bytes of transport layer headers we are guaranteed */
48 if (skb
->len
>= hdroff
+ sizeof(struct tcphdr
))
49 hdrsize
= sizeof(struct tcphdr
);
51 if (!skb_make_writable(skb
, hdroff
+ hdrsize
))
54 iph
= (struct iphdr
*)(skb
->data
+ iphdroff
);
55 hdr
= (struct tcphdr
*)(skb
->data
+ hdroff
);
57 if (maniptype
== IP_NAT_MANIP_SRC
) {
58 /* Get rid of src ip and src pt */
60 newip
= tuple
->src
.u3
.ip
;
61 newport
= tuple
->src
.u
.tcp
.port
;
62 portptr
= &hdr
->source
;
64 /* Get rid of dst ip and dst pt */
66 newip
= tuple
->dst
.u3
.ip
;
67 newport
= tuple
->dst
.u
.tcp
.port
;
74 if (hdrsize
< sizeof(*hdr
))
77 inet_proto_csum_replace4(&hdr
->check
, skb
, oldip
, newip
, 1);
78 inet_proto_csum_replace2(&hdr
->check
, skb
, oldport
, newport
, 0);
82 const struct nf_nat_protocol nf_nat_protocol_tcp
= {
83 .protonum
= IPPROTO_TCP
,
85 .manip_pkt
= tcp_manip_pkt
,
86 .in_range
= nf_nat_proto_in_range
,
87 .unique_tuple
= tcp_unique_tuple
,
88 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
89 .range_to_nlattr
= nf_nat_proto_range_to_nlattr
,
90 .nlattr_to_range
= nf_nat_proto_nlattr_to_range
,