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/seq_file.h>
  16 #include <net/ip.h>
  17 #include <net/checksum.h>
  18 #include <linux/netfilter.h>
  19 #include <linux/netfilter_ipv4.h>
  20 #include <linux/netfilter_ipv4/ip_conntrack.h>
  21 #include <linux/netfilter_ipv4/ip_conntrack_core.h>
  22 #include <linux/netfilter_ipv4/ip_conntrack_protocol.h>
  23
  24 unsigned long ip_ct_icmp_timeout = 30*HZ;
  25
  26 #if 0
  27 #define DEBUGP printk
  28 #else
  29 #define DEBUGP(format, args...)
  30 #endif
  31
  32 static int icmp_pkt_to_tuple(const struct sk_buff *skb,
  33                              unsigned int dataoff,
  34                              struct ip_conntrack_tuple *tuple)
  35 {
  36         struct icmphdr _hdr, *hp;
  37
  38         hp = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
  39         if (hp == NULL)
  40                 return 0;
  41
  42         tuple->dst.u.icmp.type = hp->type;
  43         tuple->src.u.icmp.id = hp->un.echo.id;
  44         tuple->dst.u.icmp.code = hp->code;
  45
  46         return 1;
  47 }
  48
  49 static int icmp_invert_tuple(struct ip_conntrack_tuple *tuple,
  50                              const struct ip_conntrack_tuple *orig)
  51 {
  52         /* Add 1; spaces filled with 0. */
  53         static u_int8_t invmap[]
  54                 = { [ICMP_ECHO] = ICMP_ECHOREPLY + 1,
  55                     [ICMP_ECHOREPLY] = ICMP_ECHO + 1,
  56                     [ICMP_TIMESTAMP] = ICMP_TIMESTAMPREPLY + 1,
  57                     [ICMP_TIMESTAMPREPLY] = ICMP_TIMESTAMP + 1,
  58                     [ICMP_INFO_REQUEST] = ICMP_INFO_REPLY + 1,
  59                     [ICMP_INFO_REPLY] = ICMP_INFO_REQUEST + 1,
  60                     [ICMP_ADDRESS] = ICMP_ADDRESSREPLY + 1,
  61                     [ICMP_ADDRESSREPLY] = ICMP_ADDRESS + 1};
  62
  63         if (orig->dst.u.icmp.type >= sizeof(invmap)
  64             || !invmap[orig->dst.u.icmp.type])
  65                 return 0;
  66
  67         tuple->src.u.icmp.id = orig->src.u.icmp.id;
  68         tuple->dst.u.icmp.type = invmap[orig->dst.u.icmp.type] - 1;
  69         tuple->dst.u.icmp.code = orig->dst.u.icmp.code;
  70         return 1;
  71 }
  72
  73 /* Print out the per-protocol part of the tuple. */
  74 static int icmp_print_tuple(struct seq_file *s,
  75                             const struct ip_conntrack_tuple *tuple)
  76 {
  77         return seq_printf(s, "type=%u code=%u id=%u ",
  78                           tuple->dst.u.icmp.type,
  79                           tuple->dst.u.icmp.code,
  80                           ntohs(tuple->src.u.icmp.id));
  81 }
  82
  83 /* Print out the private part of the conntrack. */
  84 static int icmp_print_conntrack(struct seq_file *s,
  85                                 const struct ip_conntrack *conntrack)
  86 {
  87         return 0;
  88 }
  89
  90 /* Returns verdict for packet, or -1 for invalid. */
  91 static int icmp_packet(struct ip_conntrack *ct,
  92                        const struct sk_buff *skb,
  93                        enum ip_conntrack_info ctinfo)
  94 {
  95         /* Try to delete connection immediately after all replies:
  96            won't actually vanish as we still have skb, and del_timer
  97            means this will only run once even if count hits zero twice
  98            (theoretically possible with SMP) */
  99         if (CTINFO2DIR(ctinfo) == IP_CT_DIR_REPLY) {
 100                 if (atomic_dec_and_test(&ct->proto.icmp.count)
 101                     && del_timer(&ct->timeout))
 102                         ct->timeout.function((unsigned long)ct);
 103         } else {
 104                 atomic_inc(&ct->proto.icmp.count);
 105                 ip_ct_refresh_acct(ct, ctinfo, skb, ip_ct_icmp_timeout);
 106         }
 107
 108         return NF_ACCEPT;
 109 }
 110
 111 /* Called when a new connection for this protocol found. */
 112 static int icmp_new(struct ip_conntrack *conntrack,
 113                     const struct sk_buff *skb)
 114 {
 115         static u_int8_t valid_new[]
 116                 = { [ICMP_ECHO] = 1,
 117                     [ICMP_TIMESTAMP] = 1,
 118                     [ICMP_INFO_REQUEST] = 1,
 119                     [ICMP_ADDRESS] = 1 };
 120
 121         if (conntrack->tuplehash[0].tuple.dst.u.icmp.type >= sizeof(valid_new)
 122             || !valid_new[conntrack->tuplehash[0].tuple.dst.u.icmp.type]) {
 123                 /* Can't create a new ICMP `conn' with this. */
 124                 DEBUGP("icmp: can't create new conn with type %u\n",
 125                        conntrack->tuplehash[0].tuple.dst.u.icmp.type);
 126                 DUMP_TUPLE(&conntrack->tuplehash[0].tuple);
 127                 return 0;
 128         }
 129         atomic_set(&conntrack->proto.icmp.count, 0);
 130         return 1;
 131 }
 132
 133 static int
 134 icmp_error_message(struct sk_buff *skb,
 135                    enum ip_conntrack_info *ctinfo,
 136                    unsigned int hooknum)
 137 {
 138         struct ip_conntrack_tuple innertuple, origtuple;
 139         struct {
 140                 struct icmphdr icmp;
 141                 struct iphdr ip;
 142         } _in, *inside;
 143         struct ip_conntrack_protocol *innerproto;
 144         struct ip_conntrack_tuple_hash *h;
 145         int dataoff;
 146
 147         IP_NF_ASSERT(skb->nfct == NULL);
 148
 149         /* Not enough header? */
 150         inside = skb_header_pointer(skb, skb->nh.iph->ihl*4, sizeof(_in), &_in);
 151         if (inside == NULL)
 152                 return NF_ACCEPT;
 153
 154         /* Ignore ICMP's containing fragments (shouldn't happen) */
 155         if (inside->ip.frag_off & htons(IP_OFFSET)) {
 156                 DEBUGP("icmp_error_track: fragment of proto %u\n",
 157                        inside->ip.protocol);
 158                 return NF_ACCEPT;
 159         }
 160
 161         innerproto = ip_ct_find_proto(inside->ip.protocol);
 162         dataoff = skb->nh.iph->ihl*4 + sizeof(inside->icmp) + inside->ip.ihl*4;
 163         /* Are they talking about one of our connections? */
 164         if (!ip_ct_get_tuple(&inside->ip, skb, dataoff, &origtuple, innerproto)) {
 165                 DEBUGP("icmp_error: ! get_tuple p=%u", inside->ip.protocol);
 166                 return NF_ACCEPT;
 167         }
 168
 169         /* Ordinarily, we'd expect the inverted tupleproto, but it's
 170            been preserved inside the ICMP. */
 171         if (!ip_ct_invert_tuple(&innertuple, &origtuple, innerproto)) {
 172                 DEBUGP("icmp_error_track: Can't invert tuple\n");
 173                 return NF_ACCEPT;
 174         }
 175
 176         *ctinfo = IP_CT_RELATED;
 177
 178         h = ip_conntrack_find_get(&innertuple, NULL);
 179         if (!h) {
 180                 /* Locally generated ICMPs will match inverted if they
 181                    haven't been SNAT'ed yet */
 182                 /* FIXME: NAT code has to handle half-done double NAT --RR */
 183                 if (hooknum == NF_IP_LOCAL_OUT)
 184                         h = ip_conntrack_find_get(&origtuple, NULL);
 185
 186                 if (!h) {
 187                         DEBUGP("icmp_error_track: no match\n");
 188                         return NF_ACCEPT;
 189                 }
 190                 /* Reverse direction from that found */
 191                 if (DIRECTION(h) != IP_CT_DIR_REPLY)
 192                         *ctinfo += IP_CT_IS_REPLY;
 193         } else {
 194                 if (DIRECTION(h) == IP_CT_DIR_REPLY)
 195                         *ctinfo += IP_CT_IS_REPLY;
 196         }
 197
 198         /* Update skb to refer to this connection */
 199         skb->nfct = &tuplehash_to_ctrack(h)->ct_general;
 200         skb->nfctinfo = *ctinfo;
 201         return -NF_ACCEPT;
 202 }
 203
 204 /* Small and modified version of icmp_rcv */
 205 static int
 206 icmp_error(struct sk_buff *skb, enum ip_conntrack_info *ctinfo,
 207            unsigned int hooknum)
 208 {
 209         struct icmphdr _ih, *icmph;
 210
 211         /* Not enough header? */
 212         icmph = skb_header_pointer(skb, skb->nh.iph->ihl*4, sizeof(_ih), &_ih);
 213         if (icmph == NULL) {
 214                 if (LOG_INVALID(IPPROTO_ICMP))
 215                         nf_log_packet(PF_INET, 0, skb, NULL, NULL,
 216                                       "ip_ct_icmp: short packet ");
 217                 return -NF_ACCEPT;
 218         }
 219
 220         /* See ip_conntrack_proto_tcp.c */
 221         if (hooknum != NF_IP_PRE_ROUTING)
 222                 goto checksum_skipped;
 223
 224         switch (skb->ip_summed) {
 225         case CHECKSUM_HW:
 226                 if (!(u16)csum_fold(skb->csum))
 227                         break;
 228                 if (LOG_INVALID(IPPROTO_ICMP))
 229                         nf_log_packet(PF_INET, 0, skb, NULL, NULL,
 230                                       "ip_ct_icmp: bad HW ICMP checksum ");
 231                 return -NF_ACCEPT;
 232         case CHECKSUM_NONE:
 233                 if ((u16)csum_fold(skb_checksum(skb, 0, skb->len, 0))) {
 234                         if (LOG_INVALID(IPPROTO_ICMP))
 235                                 nf_log_packet(PF_INET, 0, skb, NULL, NULL,
 236                                               "ip_ct_icmp: bad ICMP checksum ");
 237                         return -NF_ACCEPT;
 238                 }
 239         default:
 240                 break;
 241         }
 242
 243 checksum_skipped:
 244         /*
 245          *      18 is the highest 'known' ICMP type. Anything else is a mystery
 246          *
 247          *      RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
 248          *                discarded.
 249          */
 250         if (icmph->type > NR_ICMP_TYPES) {
 251                 if (LOG_INVALID(IPPROTO_ICMP))
 252                         nf_log_packet(PF_INET, 0, skb, NULL, NULL,
 253                                       "ip_ct_icmp: invalid ICMP type ");
 254                 return -NF_ACCEPT;
 255         }
 256
 257         /* Need to track icmp error message? */
 258         if (icmph->type != ICMP_DEST_UNREACH
 259             && icmph->type != ICMP_SOURCE_QUENCH
 260             && icmph->type != ICMP_TIME_EXCEEDED
 261             && icmph->type != ICMP_PARAMETERPROB
 262             && icmph->type != ICMP_REDIRECT)
 263                 return NF_ACCEPT;
 264
 265         return icmp_error_message(skb, ctinfo, hooknum);
 266 }
 267
 268 struct ip_conntrack_protocol ip_conntrack_protocol_icmp =
 269 {
 270         .proto                  = IPPROTO_ICMP,
 271         .name                   = "icmp",
 272         .pkt_to_tuple           = icmp_pkt_to_tuple,
 273         .invert_tuple           = icmp_invert_tuple,
 274         .print_tuple            = icmp_print_tuple,
 275         .print_conntrack        = icmp_print_conntrack,
 276         .packet                 = icmp_packet,
 277         .new                    = icmp_new,
 278         .error                  = icmp_error,
 279 };