1 /* (C) 1999-2001 Paul `Rusty' Russell
2 * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
3 *
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.
7 */
8
9 #include <linux/types.h>
10 #include <linux/export.h>
11 #include <linux/init.h>
12 #include <linux/ip.h>
13 #include <linux/udp.h>
14
15 #include <linux/netfilter.h>
16 #include <net/netfilter/nf_nat.h>
17 #include <net/netfilter/nf_nat_core.h>
18 #include <net/netfilter/nf_nat_rule.h>
19 #include <net/netfilter/nf_nat_protocol.h>
20
21 static u_int16_t udp_port_rover;
22
23 static void
udp_unique_tuple(struct nf_conntrack_tuple * tuple,const struct nf_nat_ipv4_range * range,enum nf_nat_manip_type maniptype,const struct nf_conn * ct)24 udp_unique_tuple(struct nf_conntrack_tuple *tuple,
25 const struct nf_nat_ipv4_range *range,
26 enum nf_nat_manip_type maniptype,
27 const struct nf_conn *ct)
28 {
29 nf_nat_proto_unique_tuple(tuple, range, maniptype, ct, &udp_port_rover);
30 }
31
32 static bool
udp_manip_pkt(struct sk_buff * skb,unsigned int iphdroff,const struct nf_conntrack_tuple * tuple,enum nf_nat_manip_type maniptype)33 udp_manip_pkt(struct sk_buff *skb,
34 unsigned int iphdroff,
35 const struct nf_conntrack_tuple *tuple,
36 enum nf_nat_manip_type maniptype)
37 {
38 const struct iphdr *iph = (struct iphdr *)(skb->data + iphdroff);
39 struct udphdr *hdr;
40 unsigned int hdroff = iphdroff + iph->ihl*4;
41 __be32 oldip, newip;
42 __be16 *portptr, newport;
43
44 if (!skb_make_writable(skb, hdroff + sizeof(*hdr)))
45 return false;
46
47 iph = (struct iphdr *)(skb->data + iphdroff);
48 hdr = (struct udphdr *)(skb->data + hdroff);
49
50 if (maniptype == NF_NAT_MANIP_SRC) {
51 /* Get rid of src ip and src pt */
52 oldip = iph->saddr;
53 newip = tuple->src.u3.ip;
54 newport = tuple->src.u.udp.port;
55 portptr = &hdr->source;
56 } else {
57 /* Get rid of dst ip and dst pt */
58 oldip = iph->daddr;
59 newip = tuple->dst.u3.ip;
60 newport = tuple->dst.u.udp.port;
61 portptr = &hdr->dest;
62 }
63 if (hdr->check || skb->ip_summed == CHECKSUM_PARTIAL) {
64 inet_proto_csum_replace4(&hdr->check, skb, oldip, newip, 1);
65 inet_proto_csum_replace2(&hdr->check, skb, *portptr, newport,
66 0);
67 if (!hdr->check)
68 hdr->check = CSUM_MANGLED_0;
69 }
70 *portptr = newport;
71 return true;
72 }
73
74 const struct nf_nat_protocol nf_nat_protocol_udp = {
75 .protonum = IPPROTO_UDP,
76 .manip_pkt = udp_manip_pkt,
77 .in_range = nf_nat_proto_in_range,
78 .unique_tuple = udp_unique_tuple,
79 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
80 .nlattr_to_range = nf_nat_proto_nlattr_to_range,
81 #endif
82 };
83