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_conntrack_event_cache(IPCT_PROTOINFO_VOLATILE, skb);
 106                 ip_ct_refresh_acct(ct, ctinfo, skb, ip_ct_icmp_timeout);
 107         }
 108
 109         return NF_ACCEPT;
 110 }
 111
 112 static u_int8_t valid_new[] = {
 113         [ICMP_ECHO] = 1,
 114         [ICMP_TIMESTAMP] = 1,
 115         [ICMP_INFO_REQUEST] = 1,
 116         [ICMP_ADDRESS] = 1
 117 };
 118
 119 /* Called when a new connection for this protocol found. */
 120 static int icmp_new(struct ip_conntrack *conntrack,
 121                     const struct sk_buff *skb)
 122 {
 123         if (conntrack->tuplehash[0].tuple.dst.u.icmp.type >= sizeof(valid_new)
 124             || !valid_new[conntrack->tuplehash[0].tuple.dst.u.icmp.type]) {
 125                 /* Can't create a new ICMP `conn' with this. */
 126                 DEBUGP("icmp: can't create new conn with type %u\n",
 127                        conntrack->tuplehash[0].tuple.dst.u.icmp.type);
 128                 DUMP_TUPLE(&conntrack->tuplehash[0].tuple);
 129                 return 0;
 130         }
 131         atomic_set(&conntrack->proto.icmp.count, 0);
 132         return 1;
 133 }
 134
 135 static int
 136 icmp_error_message(struct sk_buff *skb,
 137                    enum ip_conntrack_info *ctinfo,
 138                    unsigned int hooknum)
 139 {
 140         struct ip_conntrack_tuple innertuple, origtuple;
 141         struct {
 142                 struct icmphdr icmp;
 143                 struct iphdr ip;
 144         } _in, *inside;
 145         struct ip_conntrack_protocol *innerproto;
 146         struct ip_conntrack_tuple_hash *h;
 147         int dataoff;
 148
 149         IP_NF_ASSERT(skb->nfct == NULL);
 150
 151         /* Not enough header? */
 152         inside = skb_header_pointer(skb, skb->nh.iph->ihl*4, sizeof(_in), &_in);
 153         if (inside == NULL)
 154                 return -NF_ACCEPT;
 155
 156         /* Ignore ICMP's containing fragments (shouldn't happen) */
 157         if (inside->ip.frag_off & htons(IP_OFFSET)) {
 158                 DEBUGP("icmp_error_track: fragment of proto %u\n",
 159                        inside->ip.protocol);
 160                 return -NF_ACCEPT;
 161         }
 162
 163         innerproto = ip_conntrack_proto_find_get(inside->ip.protocol);
 164         dataoff = skb->nh.iph->ihl*4 + sizeof(inside->icmp) + inside->ip.ihl*4;
 165         /* Are they talking about one of our connections? */
 166         if (!ip_ct_get_tuple(&inside->ip, skb, dataoff, &origtuple, innerproto)) {
 167                 DEBUGP("icmp_error: ! get_tuple p=%u", inside->ip.protocol);
 168                 ip_conntrack_proto_put(innerproto);
 169                 return -NF_ACCEPT;
 170         }
 171
 172         /* Ordinarily, we'd expect the inverted tupleproto, but it's
 173            been preserved inside the ICMP. */
 174         if (!ip_ct_invert_tuple(&innertuple, &origtuple, innerproto)) {
 175                 DEBUGP("icmp_error_track: Can't invert tuple\n");
 176                 ip_conntrack_proto_put(innerproto);
 177                 return -NF_ACCEPT;
 178         }
 179         ip_conntrack_proto_put(innerproto);
 180
 181         *ctinfo = IP_CT_RELATED;
 182
 183         h = ip_conntrack_find_get(&innertuple, NULL);
 184         if (!h) {
 185                 /* Locally generated ICMPs will match inverted if they
 186                    haven't been SNAT'ed yet */
 187                 /* FIXME: NAT code has to handle half-done double NAT --RR */
 188                 if (hooknum == NF_IP_LOCAL_OUT)
 189                         h = ip_conntrack_find_get(&origtuple, NULL);
 190
 191                 if (!h) {
 192                         DEBUGP("icmp_error_track: no match\n");
 193                         return -NF_ACCEPT;
 194                 }
 195                 /* Reverse direction from that found */
 196                 if (DIRECTION(h) != IP_CT_DIR_REPLY)
 197                         *ctinfo += IP_CT_IS_REPLY;
 198         } else {
 199                 if (DIRECTION(h) == IP_CT_DIR_REPLY)
 200                         *ctinfo += IP_CT_IS_REPLY;
 201         }
 202
 203         /* Update skb to refer to this connection */
 204         skb->nfct = &tuplehash_to_ctrack(h)->ct_general;
 205         skb->nfctinfo = *ctinfo;
 206         return -NF_ACCEPT;
 207 }
 208
 209 /* Small and modified version of icmp_rcv */
 210 static int
 211 icmp_error(struct sk_buff *skb, enum ip_conntrack_info *ctinfo,
 212            unsigned int hooknum)
 213 {
 214         struct icmphdr _ih, *icmph;
 215
 216         /* Not enough header? */
 217         icmph = skb_header_pointer(skb, skb->nh.iph->ihl*4, sizeof(_ih), &_ih);
 218         if (icmph == NULL) {
 219                 if (LOG_INVALID(IPPROTO_ICMP))
 220                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 221                                       "ip_ct_icmp: short packet ");
 222                 return -NF_ACCEPT;
 223         }
 224
 225         /* See ip_conntrack_proto_tcp.c */
 226         if (hooknum != NF_IP_PRE_ROUTING)
 227                 goto checksum_skipped;
 228
 229         switch (skb->ip_summed) {
 230         case CHECKSUM_HW:
 231                 if (!(u16)csum_fold(skb->csum))
 232                         break;
 233                 if (LOG_INVALID(IPPROTO_ICMP))
 234                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 235                                       "ip_ct_icmp: bad HW ICMP checksum ");
 236                 return -NF_ACCEPT;
 237         case CHECKSUM_NONE:
 238                 if ((u16)csum_fold(skb_checksum(skb, 0, skb->len, 0))) {
 239                         if (LOG_INVALID(IPPROTO_ICMP))
 240                                 nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 241                                               "ip_ct_icmp: bad ICMP checksum ");
 242                         return -NF_ACCEPT;
 243                 }
 244         default:
 245                 break;
 246         }
 247
 248 checksum_skipped:
 249         /*
 250          *      18 is the highest 'known' ICMP type. Anything else is a mystery
 251          *
 252          *      RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
 253          *                discarded.
 254          */
 255         if (icmph->type > NR_ICMP_TYPES) {
 256                 if (LOG_INVALID(IPPROTO_ICMP))
 257                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 258                                       "ip_ct_icmp: invalid ICMP type ");
 259                 return -NF_ACCEPT;
 260         }
 261
 262         /* Need to track icmp error message? */
 263         if (icmph->type != ICMP_DEST_UNREACH
 264             && icmph->type != ICMP_SOURCE_QUENCH
 265             && icmph->type != ICMP_TIME_EXCEEDED
 266             && icmph->type != ICMP_PARAMETERPROB
 267             && icmph->type != ICMP_REDIRECT)
 268                 return NF_ACCEPT;
 269
 270         return icmp_error_message(skb, ctinfo, hooknum);
 271 }
 272
 273 #if defined(CONFIG_IP_NF_CONNTRACK_NETLINK) || \
 274     defined(CONFIG_IP_NF_CONNTRACK_NETLINK_MODULE)
 275 static int icmp_tuple_to_nfattr(struct sk_buff *skb,
 276                                 const struct ip_conntrack_tuple *t)
 277 {
 278         NFA_PUT(skb, CTA_PROTO_ICMP_ID, sizeof(u_int16_t),
 279                 &t->src.u.icmp.id);
 280         NFA_PUT(skb, CTA_PROTO_ICMP_TYPE, sizeof(u_int8_t),
 281                 &t->dst.u.icmp.type);
 282         NFA_PUT(skb, CTA_PROTO_ICMP_CODE, sizeof(u_int8_t),
 283                 &t->dst.u.icmp.code);
 284
 285         if (t->dst.u.icmp.type >= sizeof(valid_new)
 286             || !valid_new[t->dst.u.icmp.type])
 287                 return -EINVAL;
 288
 289         return 0;
 290
 291 nfattr_failure:
 292         return -1;
 293 }
 294
 295 static int icmp_nfattr_to_tuple(struct nfattr *tb[],
 296                                 struct ip_conntrack_tuple *tuple)
 297 {
 298         if (!tb[CTA_PROTO_ICMP_TYPE-1]
 299             || !tb[CTA_PROTO_ICMP_CODE-1]
 300             || !tb[CTA_PROTO_ICMP_ID-1])
 301                 return -1;
 302
 303         tuple->dst.u.icmp.type =
 304                         *(u_int8_t *)NFA_DATA(tb[CTA_PROTO_ICMP_TYPE-1]);
 305         tuple->dst.u.icmp.code =
 306                         *(u_int8_t *)NFA_DATA(tb[CTA_PROTO_ICMP_CODE-1]);
 307         tuple->src.u.icmp.id =
 308                         *(u_int16_t *)NFA_DATA(tb[CTA_PROTO_ICMP_ID-1]);
 309
 310         return 0;
 311 }
 312 #endif
 313
 314 struct ip_conntrack_protocol ip_conntrack_protocol_icmp =
 315 {
 316         .proto                  = IPPROTO_ICMP,
 317         .name                   = "icmp",
 318         .pkt_to_tuple           = icmp_pkt_to_tuple,
 319         .invert_tuple           = icmp_invert_tuple,
 320         .print_tuple            = icmp_print_tuple,
 321         .print_conntrack        = icmp_print_conntrack,
 322         .packet                 = icmp_packet,
 323         .new                    = icmp_new,
 324         .error                  = icmp_error,
 325 #if defined(CONFIG_IP_NF_CONNTRACK_NETLINK) || \
 326     defined(CONFIG_IP_NF_CONNTRACK_NETLINK_MODULE)
 327         .tuple_to_nfattr        = icmp_tuple_to_nfattr,
 328         .nfattr_to_tuple        = icmp_nfattr_to_tuple,
 329 #endif
 330 };