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/udp.h>
13
14 #include <linux/netfilter.h>
15 #include <net/netfilter/nf_nat.h>
16 #include <net/netfilter/nf_nat_core.h>
17 #include <net/netfilter/nf_nat_l3proto.h>
18 #include <net/netfilter/nf_nat_l4proto.h>
19
20 static u16 udp_port_rover;
21
22 static void
udp_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)23 udp_unique_tuple(const struct nf_nat_l3proto *l3proto,
24 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)
28 {
29 nf_nat_l4proto_unique_tuple(l3proto, tuple, range, maniptype, ct,
30 &udp_port_rover);
31 }
32
33 static bool
udp_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)34 udp_manip_pkt(struct sk_buff *skb,
35 const struct nf_nat_l3proto *l3proto,
36 unsigned int iphdroff, unsigned int hdroff,
37 const struct nf_conntrack_tuple *tuple,
38 enum nf_nat_manip_type maniptype)
39 {
40 struct udphdr *hdr;
41 __be16 *portptr, newport;
42
43 if (!skb_make_writable(skb, hdroff + sizeof(*hdr)))
44 return false;
45 hdr = (struct udphdr *)(skb->data + hdroff);
46
47 if (maniptype == NF_NAT_MANIP_SRC) {
48 /* Get rid of src port */
49 newport = tuple->src.u.udp.port;
50 portptr = &hdr->source;
51 } else {
52 /* Get rid of dst port */
53 newport = tuple->dst.u.udp.port;
54 portptr = &hdr->dest;
55 }
56 if (hdr->check || skb->ip_summed == CHECKSUM_PARTIAL) {
57 l3proto->csum_update(skb, iphdroff, &hdr->check,
58 tuple, maniptype);
59 inet_proto_csum_replace2(&hdr->check, skb, *portptr, newport,
60 0);
61 if (!hdr->check)
62 hdr->check = CSUM_MANGLED_0;
63 }
64 *portptr = newport;
65 return true;
66 }
67
68 const struct nf_nat_l4proto nf_nat_l4proto_udp = {
69 .l4proto = IPPROTO_UDP,
70 .manip_pkt = udp_manip_pkt,
71 .in_range = nf_nat_l4proto_in_range,
72 .unique_tuple = udp_unique_tuple,
73 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
74 .nlattr_to_range = nf_nat_l4proto_nlattr_to_range,
75 #endif
76 };
77