LXR linux/net/ipv4/netfilter/nf_nat_proto

   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 void
  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; ; ++id) {
  46                tuple->src.u.icmp.id = htons(ntohs(range->min.icmp.id) +
  47                                             (id % range_size));
  48                if (++i == range_size || !nf_nat_used_tuple(tuple, ct))
  49                        return;
  50        }
  51        return;
  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};
  85