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/module.h>
14 #include <linux/init.h>
15 #include <linux/skbuff.h>
16 #include <linux/dccp.h>
17
18 #include <net/netfilter/nf_conntrack.h>
19 #include <net/netfilter/nf_nat.h>
20 #include <net/netfilter/nf_nat_l3proto.h>
21 #include <net/netfilter/nf_nat_l4proto.h>
22
23 static u_int16_t dccp_port_rover;
24
25 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)26 dccp_unique_tuple(const struct nf_nat_l3proto *l3proto,
27 struct nf_conntrack_tuple *tuple,
28 const struct nf_nat_range *range,
29 enum nf_nat_manip_type maniptype,
30 const struct nf_conn *ct)
31 {
32 nf_nat_l4proto_unique_tuple(l3proto, tuple, range, maniptype, ct,
33 &dccp_port_rover);
34 }
35
36 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)37 dccp_manip_pkt(struct sk_buff *skb,
38 const struct nf_nat_l3proto *l3proto,
39 unsigned int iphdroff, unsigned int hdroff,
40 const struct nf_conntrack_tuple *tuple,
41 enum nf_nat_manip_type maniptype)
42 {
43 struct dccp_hdr *hdr;
44 __be16 *portptr, oldport, newport;
45 int hdrsize = 8; /* DCCP connection tracking guarantees this much */
46
47 if (skb->len >= hdroff + sizeof(struct dccp_hdr))
48 hdrsize = sizeof(struct dccp_hdr);
49
50 if (!skb_make_writable(skb, hdroff + hdrsize))
51 return false;
52
53 hdr = (struct dccp_hdr *)(skb->data + hdroff);
54
55 if (maniptype == NF_NAT_MANIP_SRC) {
56 newport = tuple->src.u.dccp.port;
57 portptr = &hdr->dccph_sport;
58 } else {
59 newport = tuple->dst.u.dccp.port;
60 portptr = &hdr->dccph_dport;
61 }
62
63 oldport = *portptr;
64 *portptr = newport;
65
66 if (hdrsize < sizeof(*hdr))
67 return true;
68
69 l3proto->csum_update(skb, iphdroff, &hdr->dccph_checksum,
70 tuple, maniptype);
71 inet_proto_csum_replace2(&hdr->dccph_checksum, skb, oldport, newport,
72 false);
73 return true;
74 }
75
76 static const struct nf_nat_l4proto nf_nat_l4proto_dccp = {
77 .l4proto = IPPROTO_DCCP,
78 .manip_pkt = dccp_manip_pkt,
79 .in_range = nf_nat_l4proto_in_range,
80 .unique_tuple = dccp_unique_tuple,
81 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
82 .nlattr_to_range = nf_nat_l4proto_nlattr_to_range,
83 #endif
84 };
85
nf_nat_proto_dccp_init(void)86 static int __init nf_nat_proto_dccp_init(void)
87 {
88 int err;
89
90 err = nf_nat_l4proto_register(NFPROTO_IPV4, &nf_nat_l4proto_dccp);
91 if (err < 0)
92 goto err1;
93 err = nf_nat_l4proto_register(NFPROTO_IPV6, &nf_nat_l4proto_dccp);
94 if (err < 0)
95 goto err2;
96 return 0;
97
98 err2:
99 nf_nat_l4proto_unregister(NFPROTO_IPV4, &nf_nat_l4proto_dccp);
100 err1:
101 return err;
102 }
103
nf_nat_proto_dccp_fini(void)104 static void __exit nf_nat_proto_dccp_fini(void)
105 {
106 nf_nat_l4proto_unregister(NFPROTO_IPV6, &nf_nat_l4proto_dccp);
107 nf_nat_l4proto_unregister(NFPROTO_IPV4, &nf_nat_l4proto_dccp);
108
109 }
110
111 module_init(nf_nat_proto_dccp_init);
112 module_exit(nf_nat_proto_dccp_fini);
113
114 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
115 MODULE_DESCRIPTION("DCCP NAT protocol helper");
116 MODULE_LICENSE("GPL");
117