net/ipv4/netfilter/ip_nat_proto_icmp.c

   1 /* (C) 1999-2001 Paul `Rusty' Russell
   2  * (C) 2002-2004 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/netfilter.h>
  12 #include <linux/ip.h>
  13 #include <linux/icmp.h>
  14 #include <linux/if.h>
  15
  16 #include <linux/netfilter_ipv4/ip_nat.h>
  17 #include <linux/netfilter_ipv4/ip_nat_core.h>
  18 #include <linux/netfilter_ipv4/ip_nat_rule.h>
  19 #include <linux/netfilter_ipv4/ip_nat_protocol.h>
  20
  21 static int
  22 icmp_in_range(const struct ip_conntrack_tuple *tuple,
  23               enum ip_nat_manip_type maniptype,
  24               const union ip_conntrack_manip_proto *min,
  25               const union ip_conntrack_manip_proto *max)
  26 {
  27         return (tuple->src.u.icmp.id >= min->icmp.id
  28                 && tuple->src.u.icmp.id <= max->icmp.id);
  29 }
  30
  31 static int
  32 icmp_unique_tuple(struct ip_conntrack_tuple *tuple,
  33                   const struct ip_nat_range *range,
  34                   enum ip_nat_manip_type maniptype,
  35                   const struct ip_conntrack *conntrack)
  36 {
  37         static u_int16_t id;
  38         unsigned int range_size
  39                 = (unsigned int)range->max.icmp.id - range->min.icmp.id + 1;
  40         unsigned int i;
  41
  42         /* If no range specified... */
  43         if (!(range->flags & IP_NAT_RANGE_PROTO_SPECIFIED))
  44                 range_size = 0xFFFF;
  45
  46         for (i = 0; i < range_size; i++, id++) {
  47                 tuple->src.u.icmp.id = range->min.icmp.id + (id % range_size);
  48                 if (!ip_nat_used_tuple(tuple, conntrack))
  49                         return 1;
  50         }
  51         return 0;
  52 }
  53
  54 static int
  55 icmp_manip_pkt(struct sk_buff **pskb,
  56                unsigned int iphdroff,
  57                const struct ip_conntrack_tuple *tuple,
  58                enum ip_nat_manip_type maniptype)
  59 {
  60         struct iphdr *iph = (struct iphdr *)((*pskb)->data + iphdroff);
  61         struct icmphdr *hdr;
  62         unsigned int hdroff = iphdroff + iph->ihl*4;
  63
  64         if (!skb_ip_make_writable(pskb, hdroff + sizeof(*hdr)))
  65                 return 0;
  66
  67         hdr = (struct icmphdr *)((*pskb)->data + hdroff);
  68
  69         hdr->checksum = ip_nat_cheat_check(hdr->un.echo.id ^ 0xFFFF,
  70                                             tuple->src.u.icmp.id,
  71                                             hdr->checksum);
  72         hdr->un.echo.id = tuple->src.u.icmp.id;
  73         return 1;
  74 }
  75
  76 static unsigned int
  77 icmp_print(char *buffer,
  78            const struct ip_conntrack_tuple *match,
  79            const struct ip_conntrack_tuple *mask)
  80 {
  81         unsigned int len = 0;
  82
  83         if (mask->src.u.icmp.id)
  84                 len += sprintf(buffer + len, "id=%u ",
  85                                ntohs(match->src.u.icmp.id));
  86
  87         if (mask->dst.u.icmp.type)
  88                 len += sprintf(buffer + len, "type=%u ",
  89                                ntohs(match->dst.u.icmp.type));
  90
  91         if (mask->dst.u.icmp.code)
  92                 len += sprintf(buffer + len, "code=%u ",
  93                                ntohs(match->dst.u.icmp.code));
  94
  95         return len;
  96 }
  97
  98 static unsigned int
  99 icmp_print_range(char *buffer, const struct ip_nat_range *range)
 100 {
 101         if (range->min.icmp.id != 0 || range->max.icmp.id != 0xFFFF)
 102                 return sprintf(buffer, "id %u-%u ",
 103                                ntohs(range->min.icmp.id),
 104                                ntohs(range->max.icmp.id));
 105         else return 0;
 106 }
 107
 108 struct ip_nat_protocol ip_nat_protocol_icmp
 109 = { "ICMP", IPPROTO_ICMP,
 110     icmp_manip_pkt,
 111     icmp_in_range,
 112     icmp_unique_tuple,
 113     icmp_print,
 114     icmp_print_range
 115 };