1 /*
2 * DCCP NAT protocol helper
3 *
4 * Copyright (c) 2005, 2006, 2008 Patrick McHardy <kaber@trash.net>
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
9 *
10 */
11
12 #include <linux/kernel.h>
13 #include <linux/skbuff.h>
14 #include <linux/dccp.h>
15
16 #include <net/netfilter/nf_conntrack.h>
17 #include <net/netfilter/nf_nat.h>
18 #include <net/netfilter/nf_nat_l3proto.h>
19 #include <net/netfilter/nf_nat_l4proto.h>
20
21 static u_int16_t dccp_port_rover;
22
23 static void
dccp_unique_tuple(const struct nf_nat_l3proto * l3proto,struct nf_conntrack_tuple * tuple,const struct nf_nat_range * range,enum nf_nat_manip_type maniptype,const struct nf_conn * ct)24 dccp_unique_tuple(const struct nf_nat_l3proto *l3proto,
25 struct nf_conntrack_tuple *tuple,
26 const struct nf_nat_range *range,
27 enum nf_nat_manip_type maniptype,
28 const struct nf_conn *ct)
29 {
30 nf_nat_l4proto_unique_tuple(l3proto, tuple, range, maniptype, ct,
31 &dccp_port_rover);
32 }
33
34 static bool
dccp_manip_pkt(struct sk_buff * skb,const struct nf_nat_l3proto * l3proto,unsigned int iphdroff,unsigned int hdroff,const struct nf_conntrack_tuple * tuple,enum nf_nat_manip_type maniptype)35 dccp_manip_pkt(struct sk_buff *skb,
36 const struct nf_nat_l3proto *l3proto,
37 unsigned int iphdroff, unsigned int hdroff,
38 const struct nf_conntrack_tuple *tuple,
39 enum nf_nat_manip_type maniptype)
40 {
41 struct dccp_hdr *hdr;
42 __be16 *portptr, oldport, newport;
43 int hdrsize = 8; /* DCCP connection tracking guarantees this much */
44
45 if (skb->len >= hdroff + sizeof(struct dccp_hdr))
46 hdrsize = sizeof(struct dccp_hdr);
47
48 if (!skb_make_writable(skb, hdroff + hdrsize))
49 return false;
50
51 hdr = (struct dccp_hdr *)(skb->data + hdroff);
52
53 if (maniptype == NF_NAT_MANIP_SRC) {
54 newport = tuple->src.u.dccp.port;
55 portptr = &hdr->dccph_sport;
56 } else {
57 newport = tuple->dst.u.dccp.port;
58 portptr = &hdr->dccph_dport;
59 }
60
61 oldport = *portptr;
62 *portptr = newport;
63
64 if (hdrsize < sizeof(*hdr))
65 return true;
66
67 l3proto->csum_update(skb, iphdroff, &hdr->dccph_checksum,
68 tuple, maniptype);
69 inet_proto_csum_replace2(&hdr->dccph_checksum, skb, oldport, newport,
70 false);
71 return true;
72 }
73
74 const struct nf_nat_l4proto nf_nat_l4proto_dccp = {
75 .l4proto = IPPROTO_DCCP,
76 .manip_pkt = dccp_manip_pkt,
77 .in_range = nf_nat_l4proto_in_range,
78 .unique_tuple = dccp_unique_tuple,
79 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
80 .nlattr_to_range = nf_nat_l4proto_nlattr_to_range,
81 #endif
82 };
83