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>
11 #include <linux/export.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_l3proto.h>
18 #include <net/netfilter/nf_nat_l4proto.h>
19 #include <net/netfilter/nf_nat_core.h>
22 tcp_unique_tuple(const struct nf_nat_l3proto *l3proto,
23 struct nf_conntrack_tuple *tuple,
24 const struct nf_nat_range *range,
25 enum nf_nat_manip_type maniptype,
26 const struct nf_conn *ct)
28 nf_nat_l4proto_unique_tuple(l3proto, tuple, range, maniptype, ct);
32 tcp_manip_pkt(struct sk_buff *skb,
33 const struct nf_nat_l3proto *l3proto,
34 unsigned int iphdroff, unsigned int hdroff,
35 const struct nf_conntrack_tuple *tuple,
36 enum nf_nat_manip_type maniptype)
39 __be16 *portptr, newport, oldport;
40 int hdrsize = 8; /* TCP connection tracking guarantees this much */
42 /* this could be a inner header returned in icmp packet; in such
43 cases we cannot update the checksum field since it is outside of
44 the 8 bytes of transport layer headers we are guaranteed */
45 if (skb->len >= hdroff + sizeof(struct tcphdr))
46 hdrsize = sizeof(struct tcphdr);
48 if (!skb_make_writable(skb, hdroff + hdrsize))
51 hdr = (struct tcphdr *)(skb->data + hdroff);
53 if (maniptype == NF_NAT_MANIP_SRC) {
54 /* Get rid of src port */
55 newport = tuple->src.u.tcp.port;
56 portptr = &hdr->source;
58 /* Get rid of dst port */
59 newport = tuple->dst.u.tcp.port;
66 if (hdrsize < sizeof(*hdr))
69 l3proto->csum_update(skb, iphdroff, &hdr->check, tuple, maniptype);
70 inet_proto_csum_replace2(&hdr->check, skb, oldport, newport, false);
74 const struct nf_nat_l4proto nf_nat_l4proto_tcp = {
75 .l4proto = IPPROTO_TCP,
76 .manip_pkt = tcp_manip_pkt,
77 .in_range = nf_nat_l4proto_in_range,
78 .unique_tuple = tcp_unique_tuple,
79 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
80 .nlattr_to_range = nf_nat_l4proto_nlattr_to_range,