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_rule.h>
  19 #include <net/netfilter/nf_nat_protocol.h>
  20
  21 static bool
  22 icmp_in_range(const struct nf_conntrack_tuple *tuple,
  23               enum nf_nat_manip_type maniptype,
  24               const union nf_conntrack_man_proto *min,
  25               const union nf_conntrack_man_proto *max)
  26 {
  27         return ntohs(tuple->src.u.icmp.id) >= ntohs(min->icmp.id) &&
  28                ntohs(tuple->src.u.icmp.id) <= ntohs(max->icmp.id);
  29 }
  30
  31 static void
  32 icmp_unique_tuple(struct nf_conntrack_tuple *tuple,
  33                   const struct nf_nat_ipv4_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.icmp.id) - ntohs(range->min.icmp.id) + 1;
  42         /* If no range specified... */
  43         if (!(range->flags & NF_NAT_RANGE_PROTO_SPECIFIED))
  44                 range_size = 0xFFFF;
  45
  46         for (i = 0; ; ++id) {
  47                 tuple->src.u.icmp.id = htons(ntohs(range->min.icmp.id) +
  48                                              (id % range_size));
  49                 if (++i == range_size || !nf_nat_used_tuple(tuple, ct))
  50                         return;
  51         }
  52         return;
  53 }
  54
  55 static bool
  56 icmp_manip_pkt(struct sk_buff *skb,
  57                unsigned int iphdroff,
  58                const struct nf_conntrack_tuple *tuple,
  59                enum nf_nat_manip_type maniptype)
  60 {
  61         const struct iphdr *iph = (struct iphdr *)(skb->data + iphdroff);
  62         struct icmphdr *hdr;
  63         unsigned int hdroff = iphdroff + iph->ihl*4;
  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_protocol nf_nat_protocol_icmp = {
  76         .protonum               = 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_proto_nlattr_to_range,
  82 #endif
  83 };