/net/ipv4/netfilter/nf_nat_proto_icmp.c

 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/init.h>
11#include <linux/ip.h>
12#include <linux/icmp.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_rule.h>
18#include <net/netfilter/nf_nat_protocol.h>
19
20static bool
21icmp_in_range(const struct nf_conntrack_tuple *tuple,
22	      enum nf_nat_manip_type maniptype,
23	      const union nf_conntrack_man_proto *min,
24	      const union nf_conntrack_man_proto *max)
25{
26	return ntohs(tuple->src.u.icmp.id) >= ntohs(min->icmp.id) &&
27	       ntohs(tuple->src.u.icmp.id) <= ntohs(max->icmp.id);
28}
29
30static bool
31icmp_unique_tuple(struct nf_conntrack_tuple *tuple,
32		  const struct nf_nat_range *range,
33		  enum nf_nat_manip_type maniptype,
34		  const struct nf_conn *ct)
35{
36	static u_int16_t id;
37	unsigned int range_size;
38	unsigned int i;
39
40	range_size = ntohs(range->max.icmp.id) - ntohs(range->min.icmp.id) + 1;
41	/* If no range specified... */
42	if (!(range->flags & IP_NAT_RANGE_PROTO_SPECIFIED))
43		range_size = 0xFFFF;
44
45	for (i = 0; i < range_size; i++, id++) {
46		tuple->src.u.icmp.id = htons(ntohs(range->min.icmp.id) +
47					     (id % range_size));
48		if (!nf_nat_used_tuple(tuple, ct))
49			return true;
50	}
51	return false;
52}
53
54static bool
55icmp_manip_pkt(struct sk_buff *skb,
56	       unsigned int iphdroff,
57	       const struct nf_conntrack_tuple *tuple,
58	       enum nf_nat_manip_type maniptype)
59{
60	const struct iphdr *iph = (struct iphdr *)(skb->data + iphdroff);
61	struct icmphdr *hdr;
62	unsigned int hdroff = iphdroff + iph->ihl*4;
63
64	if (!skb_make_writable(skb, hdroff + sizeof(*hdr)))
65		return false;
66
67	hdr = (struct icmphdr *)(skb->data + hdroff);
68	inet_proto_csum_replace2(&hdr->checksum, skb,
69				 hdr->un.echo.id, tuple->src.u.icmp.id, 0);
70	hdr->un.echo.id = tuple->src.u.icmp.id;
71	return true;
72}
73
74const struct nf_nat_protocol nf_nat_protocol_icmp = {
75	.protonum		= IPPROTO_ICMP,
76	.me			= THIS_MODULE,
77	.manip_pkt		= icmp_manip_pkt,
78	.in_range		= icmp_in_range,
79	.unique_tuple		= icmp_unique_tuple,
80#if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
81	.range_to_nlattr	= nf_nat_proto_range_to_nlattr,
82	.nlattr_to_range	= nf_nat_proto_nlattr_to_range,
83#endif
84};