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/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
  20 static bool
  21 icmp_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
  30 static void
  31 icmp_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
  56 static bool
  57 icmp_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
  75 const 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 };