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/export.h>
  12#include <linux/ip.h>
  13#include <linux/icmp.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_l4proto.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(const struct nf_nat_l3proto *l3proto,
  32                  struct nf_conntrack_tuple *tuple,
  33                  const struct nf_nat_range *range,
  34                  enum nf_nat_manip_type maniptype,
  35                  const struct nf_conn *ct)
  36{
  37        static u_int16_t id;
  38        unsigned int range_size;
  39        unsigned int i;
  40
  41        range_size = ntohs(range->max_proto.icmp.id) -
  42                     ntohs(range->min_proto.icmp.id) + 1;
  43        /* If no range specified... */
  44        if (!(range->flags & NF_NAT_RANGE_PROTO_SPECIFIED))
  45                range_size = 0xFFFF;
  46
  47        for (i = 0; ; ++id) {
  48                tuple->src.u.icmp.id = htons(ntohs(range->min_proto.icmp.id) +
  49                                             (id % range_size));
  50                if (++i == range_size || !nf_nat_used_tuple(tuple, ct))
  51                        return;
  52        }
  53        return;
  54}
  55
  56static bool
  57icmp_manip_pkt(struct sk_buff *skb,
  58               const struct nf_nat_l3proto *l3proto,
  59               unsigned int iphdroff, unsigned int hdroff,
  60               const struct nf_conntrack_tuple *tuple,
  61               enum nf_nat_manip_type maniptype)
  62{
  63        struct icmphdr *hdr;
  64
  65        if (!skb_make_writable(skb, hdroff + sizeof(*hdr)))
  66                return false;
  67
  68        hdr = (struct icmphdr *)(skb->data + hdroff);
  69        inet_proto_csum_replace2(&hdr->checksum, skb,
  70                                 hdr->un.echo.id, tuple->src.u.icmp.id, 0);
  71        hdr->un.echo.id = tuple->src.u.icmp.id;
  72        return true;
  73}
  74
  75const struct nf_nat_l4proto nf_nat_l4proto_icmp = {
  76        .l4proto                = IPPROTO_ICMP,
  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        .nlattr_to_range        = nf_nat_l4proto_nlattr_to_range,
  82#endif
  83};
  84