net/ipv4/netfilter/ip_conntrack_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/sched.h>
  11 #include <linux/timer.h>
  12 #include <linux/netfilter.h>
  13 #include <linux/in.h>
  14 #include <linux/icmp.h>
  15 #include <linux/netfilter_ipv4/ip_conntrack_protocol.h>
  16
  17 unsigned long ip_ct_icmp_timeout = 30*HZ;
  18
  19 #if 0
  20 #define DEBUGP printk
  21 #else
  22 #define DEBUGP(format, args...)
  23 #endif
  24
  25 static int icmp_pkt_to_tuple(const struct sk_buff *skb,
  26                              unsigned int dataoff,
  27                              struct ip_conntrack_tuple *tuple)
  28 {
  29         struct icmphdr hdr;
  30
  31         if (skb_copy_bits(skb, dataoff, &hdr, sizeof(hdr)) != 0)
  32                 return 0;
  33
  34         tuple->dst.u.icmp.type = hdr.type;
  35         tuple->src.u.icmp.id = hdr.un.echo.id;
  36         tuple->dst.u.icmp.code = hdr.code;
  37
  38         return 1;
  39 }
  40
  41 static int icmp_invert_tuple(struct ip_conntrack_tuple *tuple,
  42                              const struct ip_conntrack_tuple *orig)
  43 {
  44         /* Add 1; spaces filled with 0. */
  45         static u_int8_t invmap[]
  46                 = { [ICMP_ECHO] = ICMP_ECHOREPLY + 1,
  47                     [ICMP_ECHOREPLY] = ICMP_ECHO + 1,
  48                     [ICMP_TIMESTAMP] = ICMP_TIMESTAMPREPLY + 1,
  49                     [ICMP_TIMESTAMPREPLY] = ICMP_TIMESTAMP + 1,
  50                     [ICMP_INFO_REQUEST] = ICMP_INFO_REPLY + 1,
  51                     [ICMP_INFO_REPLY] = ICMP_INFO_REQUEST + 1,
  52                     [ICMP_ADDRESS] = ICMP_ADDRESSREPLY + 1,
  53                     [ICMP_ADDRESSREPLY] = ICMP_ADDRESS + 1};
  54
  55         if (orig->dst.u.icmp.type >= sizeof(invmap)
  56             || !invmap[orig->dst.u.icmp.type])
  57                 return 0;
  58
  59         tuple->src.u.icmp.id = orig->src.u.icmp.id;
  60         tuple->dst.u.icmp.type = invmap[orig->dst.u.icmp.type] - 1;
  61         tuple->dst.u.icmp.code = orig->dst.u.icmp.code;
  62         return 1;
  63 }
  64
  65 /* Print out the per-protocol part of the tuple. */
  66 static unsigned int icmp_print_tuple(char *buffer,
  67                                      const struct ip_conntrack_tuple *tuple)
  68 {
  69         return sprintf(buffer, "type=%u code=%u id=%u ",
  70                        tuple->dst.u.icmp.type,
  71                        tuple->dst.u.icmp.code,
  72                        ntohs(tuple->src.u.icmp.id));
  73 }
  74
  75 /* Print out the private part of the conntrack. */
  76 static unsigned int icmp_print_conntrack(char *buffer,
  77                                      const struct ip_conntrack *conntrack)
  78 {
  79         return 0;
  80 }
  81
  82 /* Returns verdict for packet, or -1 for invalid. */
  83 static int icmp_packet(struct ip_conntrack *ct,
  84                        const struct sk_buff *skb,
  85                        enum ip_conntrack_info ctinfo)
  86 {
  87         /* Try to delete connection immediately after all replies:
  88            won't actually vanish as we still have skb, and del_timer
  89            means this will only run once even if count hits zero twice
  90            (theoretically possible with SMP) */
  91         if (CTINFO2DIR(ctinfo) == IP_CT_DIR_REPLY) {
  92                 if (atomic_dec_and_test(&ct->proto.icmp.count)
  93                     && del_timer(&ct->timeout))
  94                         ct->timeout.function((unsigned long)ct);
  95         } else {
  96                 atomic_inc(&ct->proto.icmp.count);
  97                 ip_ct_refresh(ct, ip_ct_icmp_timeout);
  98         }
  99
 100         return NF_ACCEPT;
 101 }
 102
 103 /* Called when a new connection for this protocol found. */
 104 static int icmp_new(struct ip_conntrack *conntrack,
 105                     const struct sk_buff *skb)
 106 {
 107         static u_int8_t valid_new[]
 108                 = { [ICMP_ECHO] = 1,
 109                     [ICMP_TIMESTAMP] = 1,
 110                     [ICMP_INFO_REQUEST] = 1,
 111                     [ICMP_ADDRESS] = 1 };
 112
 113         if (conntrack->tuplehash[0].tuple.dst.u.icmp.type >= sizeof(valid_new)
 114             || !valid_new[conntrack->tuplehash[0].tuple.dst.u.icmp.type]) {
 115                 /* Can't create a new ICMP `conn' with this. */
 116                 DEBUGP("icmp: can't create new conn with type %u\n",
 117                        conntrack->tuplehash[0].tuple.dst.u.icmp.type);
 118                 DUMP_TUPLE(&conntrack->tuplehash[0].tuple);
 119                 return 0;
 120         }
 121         atomic_set(&conntrack->proto.icmp.count, 0);
 122         return 1;
 123 }
 124
 125 struct ip_conntrack_protocol ip_conntrack_protocol_icmp
 126 = { { NULL, NULL }, IPPROTO_ICMP, "icmp",
 127     icmp_pkt_to_tuple, icmp_invert_tuple, icmp_print_tuple,
 128     icmp_print_conntrack, icmp_packet, icmp_new, NULL, NULL, NULL };