net/ipv4/netfilter/nf_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/timer.h>
  11 #include <linux/netfilter.h>
  12 #include <linux/in.h>
  13 #include <linux/icmp.h>
  14 #include <linux/seq_file.h>
  15 #include <net/ip.h>
  16 #include <net/checksum.h>
  17 #include <linux/netfilter_ipv4.h>
  18 #include <net/netfilter/nf_conntrack_tuple.h>
  19 #include <net/netfilter/nf_conntrack_l4proto.h>
  20 #include <net/netfilter/nf_conntrack_core.h>
  21
  22 static unsigned long nf_ct_icmp_timeout __read_mostly = 30*HZ;
  23
  24 static int icmp_pkt_to_tuple(const struct sk_buff *skb,
  25                              unsigned int dataoff,
  26                              struct nf_conntrack_tuple *tuple)
  27 {
  28         struct icmphdr _hdr, *hp;
  29
  30         hp = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
  31         if (hp == NULL)
  32                 return 0;
  33
  34         tuple->dst.u.icmp.type = hp->type;
  35         tuple->src.u.icmp.id = hp->un.echo.id;
  36         tuple->dst.u.icmp.code = hp->code;
  37
  38         return 1;
  39 }
  40
  41 /* Add 1; spaces filled with 0. */
  42 static const u_int8_t invmap[] = {
  43         [ICMP_ECHO] = ICMP_ECHOREPLY + 1,
  44         [ICMP_ECHOREPLY] = ICMP_ECHO + 1,
  45         [ICMP_TIMESTAMP] = ICMP_TIMESTAMPREPLY + 1,
  46         [ICMP_TIMESTAMPREPLY] = ICMP_TIMESTAMP + 1,
  47         [ICMP_INFO_REQUEST] = ICMP_INFO_REPLY + 1,
  48         [ICMP_INFO_REPLY] = ICMP_INFO_REQUEST + 1,
  49         [ICMP_ADDRESS] = ICMP_ADDRESSREPLY + 1,
  50         [ICMP_ADDRESSREPLY] = ICMP_ADDRESS + 1
  51 };
  52
  53 static int icmp_invert_tuple(struct nf_conntrack_tuple *tuple,
  54                              const struct nf_conntrack_tuple *orig)
  55 {
  56         if (orig->dst.u.icmp.type >= sizeof(invmap)
  57             || !invmap[orig->dst.u.icmp.type])
  58                 return 0;
  59
  60         tuple->src.u.icmp.id = orig->src.u.icmp.id;
  61         tuple->dst.u.icmp.type = invmap[orig->dst.u.icmp.type] - 1;
  62         tuple->dst.u.icmp.code = orig->dst.u.icmp.code;
  63         return 1;
  64 }
  65
  66 /* Print out the per-protocol part of the tuple. */
  67 static int icmp_print_tuple(struct seq_file *s,
  68                             const struct nf_conntrack_tuple *tuple)
  69 {
  70         return seq_printf(s, "type=%u code=%u id=%u ",
  71                           tuple->dst.u.icmp.type,
  72                           tuple->dst.u.icmp.code,
  73                           ntohs(tuple->src.u.icmp.id));
  74 }
  75
  76 /* Print out the private part of the conntrack. */
  77 static int icmp_print_conntrack(struct seq_file *s,
  78                                 const struct nf_conn *conntrack)
  79 {
  80         return 0;
  81 }
  82
  83 /* Returns verdict for packet, or -1 for invalid. */
  84 static int icmp_packet(struct nf_conn *ct,
  85                        const struct sk_buff *skb,
  86                        unsigned int dataoff,
  87                        enum ip_conntrack_info ctinfo,
  88                        int pf,
  89                        unsigned int hooknum)
  90 {
  91         /* Try to delete connection immediately after all replies:
  92            won't actually vanish as we still have skb, and del_timer
  93            means this will only run once even if count hits zero twice
  94            (theoretically possible with SMP) */
  95         if (CTINFO2DIR(ctinfo) == IP_CT_DIR_REPLY) {
  96                 if (atomic_dec_and_test(&ct->proto.icmp.count)
  97                     && del_timer(&ct->timeout))
  98                         ct->timeout.function((unsigned long)ct);
  99         } else {
 100                 atomic_inc(&ct->proto.icmp.count);
 101                 nf_conntrack_event_cache(IPCT_PROTOINFO_VOLATILE, skb);
 102                 nf_ct_refresh_acct(ct, ctinfo, skb, nf_ct_icmp_timeout);
 103         }
 104
 105         return NF_ACCEPT;
 106 }
 107
 108 /* Called when a new connection for this protocol found. */
 109 static int icmp_new(struct nf_conn *conntrack,
 110                     const struct sk_buff *skb, unsigned int dataoff)
 111 {
 112         static const 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         if (conntrack->tuplehash[0].tuple.dst.u.icmp.type >= sizeof(valid_new)
 120             || !valid_new[conntrack->tuplehash[0].tuple.dst.u.icmp.type]) {
 121                 /* Can't create a new ICMP `conn' with this. */
 122                 pr_debug("icmp: can't create new conn with type %u\n",
 123                          conntrack->tuplehash[0].tuple.dst.u.icmp.type);
 124                 NF_CT_DUMP_TUPLE(&conntrack->tuplehash[0].tuple);
 125                 return 0;
 126         }
 127         atomic_set(&conntrack->proto.icmp.count, 0);
 128         return 1;
 129 }
 130
 131 extern struct nf_conntrack_l3proto nf_conntrack_l3proto_ipv4;
 132 /* Returns conntrack if it dealt with ICMP, and filled in skb fields */
 133 static int
 134 icmp_error_message(struct sk_buff *skb,
 135                  enum ip_conntrack_info *ctinfo,
 136                  unsigned int hooknum)
 137 {
 138         struct nf_conntrack_tuple innertuple, origtuple;
 139         struct {
 140                 struct icmphdr icmp;
 141                 struct iphdr ip;
 142         } _in, *inside;
 143         struct nf_conntrack_l4proto *innerproto;
 144         struct nf_conntrack_tuple_hash *h;
 145         int dataoff;
 146
 147         NF_CT_ASSERT(skb->nfct == NULL);
 148
 149         /* Not enough header? */
 150         inside = skb_header_pointer(skb, ip_hdrlen(skb), 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                 pr_debug("icmp_error_message: fragment of proto %u\n",
 157                          inside->ip.protocol);
 158                 return -NF_ACCEPT;
 159         }
 160
 161         /* rcu_read_lock()ed by nf_hook_slow */
 162         innerproto = __nf_ct_l4proto_find(PF_INET, inside->ip.protocol);
 163
 164         dataoff = ip_hdrlen(skb) + sizeof(inside->icmp);
 165         /* Are they talking about one of our connections? */
 166         if (!nf_ct_get_tuple(skb, dataoff, dataoff + inside->ip.ihl*4, PF_INET,
 167                              inside->ip.protocol, &origtuple,
 168                              &nf_conntrack_l3proto_ipv4, innerproto)) {
 169                 pr_debug("icmp_error_message: ! get_tuple p=%u",
 170                          inside->ip.protocol);
 171                 return -NF_ACCEPT;
 172         }
 173
 174         /* Ordinarily, we'd expect the inverted tupleproto, but it's
 175            been preserved inside the ICMP. */
 176         if (!nf_ct_invert_tuple(&innertuple, &origtuple,
 177                                 &nf_conntrack_l3proto_ipv4, innerproto)) {
 178                 pr_debug("icmp_error_message: no match\n");
 179                 return -NF_ACCEPT;
 180         }
 181
 182         *ctinfo = IP_CT_RELATED;
 183
 184         h = nf_conntrack_find_get(&innertuple);
 185         if (!h) {
 186                 /* Locally generated ICMPs will match inverted if they
 187                    haven't been SNAT'ed yet */
 188                 /* FIXME: NAT code has to handle half-done double NAT --RR */
 189                 if (hooknum == NF_IP_LOCAL_OUT)
 190                         h = nf_conntrack_find_get(&origtuple);
 191
 192                 if (!h) {
 193                         pr_debug("icmp_error_message: no match\n");
 194                         return -NF_ACCEPT;
 195                 }
 196
 197                 /* Reverse direction from that found */
 198                 if (NF_CT_DIRECTION(h) == IP_CT_DIR_REPLY)
 199                         *ctinfo += IP_CT_IS_REPLY;
 200         } else {
 201                 if (NF_CT_DIRECTION(h) == IP_CT_DIR_REPLY)
 202                         *ctinfo += IP_CT_IS_REPLY;
 203         }
 204
 205         /* Update skb to refer to this connection */
 206         skb->nfct = &nf_ct_tuplehash_to_ctrack(h)->ct_general;
 207         skb->nfctinfo = *ctinfo;
 208         return -NF_ACCEPT;
 209 }
 210
 211 /* Small and modified version of icmp_rcv */
 212 static int
 213 icmp_error(struct sk_buff *skb, unsigned int dataoff,
 214            enum ip_conntrack_info *ctinfo, int pf, unsigned int hooknum)
 215 {
 216         struct icmphdr _ih, *icmph;
 217
 218         /* Not enough header? */
 219         icmph = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_ih), &_ih);
 220         if (icmph == NULL) {
 221                 if (LOG_INVALID(IPPROTO_ICMP))
 222                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 223                                       "nf_ct_icmp: short packet ");
 224                 return -NF_ACCEPT;
 225         }
 226
 227         /* See ip_conntrack_proto_tcp.c */
 228         if (nf_conntrack_checksum && hooknum == NF_IP_PRE_ROUTING &&
 229             nf_ip_checksum(skb, hooknum, dataoff, 0)) {
 230                 if (LOG_INVALID(IPPROTO_ICMP))
 231                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 232                                       "nf_ct_icmp: bad HW ICMP checksum ");
 233                 return -NF_ACCEPT;
 234         }
 235
 236         /*
 237          *      18 is the highest 'known' ICMP type. Anything else is a mystery
 238          *
 239          *      RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
 240          *                discarded.
 241          */
 242         if (icmph->type > NR_ICMP_TYPES) {
 243                 if (LOG_INVALID(IPPROTO_ICMP))
 244                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 245                                       "nf_ct_icmp: invalid ICMP type ");
 246                 return -NF_ACCEPT;
 247         }
 248
 249         /* Need to track icmp error message? */
 250         if (icmph->type != ICMP_DEST_UNREACH
 251             && icmph->type != ICMP_SOURCE_QUENCH
 252             && icmph->type != ICMP_TIME_EXCEEDED
 253             && icmph->type != ICMP_PARAMETERPROB
 254             && icmph->type != ICMP_REDIRECT)
 255                 return NF_ACCEPT;
 256
 257         return icmp_error_message(skb, ctinfo, hooknum);
 258 }
 259
 260 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
 261
 262 #include <linux/netfilter/nfnetlink.h>
 263 #include <linux/netfilter/nfnetlink_conntrack.h>
 264
 265 static int icmp_tuple_to_nfattr(struct sk_buff *skb,
 266                                 const struct nf_conntrack_tuple *t)
 267 {
 268         NFA_PUT(skb, CTA_PROTO_ICMP_ID, sizeof(u_int16_t),
 269                 &t->src.u.icmp.id);
 270         NFA_PUT(skb, CTA_PROTO_ICMP_TYPE, sizeof(u_int8_t),
 271                 &t->dst.u.icmp.type);
 272         NFA_PUT(skb, CTA_PROTO_ICMP_CODE, sizeof(u_int8_t),
 273                 &t->dst.u.icmp.code);
 274
 275         return 0;
 276
 277 nfattr_failure:
 278         return -1;
 279 }
 280
 281 static const size_t cta_min_proto[CTA_PROTO_MAX] = {
 282         [CTA_PROTO_ICMP_TYPE-1] = sizeof(u_int8_t),
 283         [CTA_PROTO_ICMP_CODE-1] = sizeof(u_int8_t),
 284         [CTA_PROTO_ICMP_ID-1]   = sizeof(u_int16_t)
 285 };
 286
 287 static int icmp_nfattr_to_tuple(struct nfattr *tb[],
 288                                 struct nf_conntrack_tuple *tuple)
 289 {
 290         if (!tb[CTA_PROTO_ICMP_TYPE-1]
 291             || !tb[CTA_PROTO_ICMP_CODE-1]
 292             || !tb[CTA_PROTO_ICMP_ID-1])
 293                 return -EINVAL;
 294
 295         if (nfattr_bad_size(tb, CTA_PROTO_MAX, cta_min_proto))
 296                 return -EINVAL;
 297
 298         tuple->dst.u.icmp.type =
 299                         *(u_int8_t *)NFA_DATA(tb[CTA_PROTO_ICMP_TYPE-1]);
 300         tuple->dst.u.icmp.code =
 301                         *(u_int8_t *)NFA_DATA(tb[CTA_PROTO_ICMP_CODE-1]);
 302         tuple->src.u.icmp.id =
 303                         *(__be16 *)NFA_DATA(tb[CTA_PROTO_ICMP_ID-1]);
 304
 305         if (tuple->dst.u.icmp.type >= sizeof(invmap)
 306             || !invmap[tuple->dst.u.icmp.type])
 307                 return -EINVAL;
 308
 309         return 0;
 310 }
 311 #endif
 312
 313 #ifdef CONFIG_SYSCTL
 314 static struct ctl_table_header *icmp_sysctl_header;
 315 static struct ctl_table icmp_sysctl_table[] = {
 316         {
 317                 .ctl_name       = NET_NF_CONNTRACK_ICMP_TIMEOUT,
 318                 .procname       = "nf_conntrack_icmp_timeout",
 319                 .data           = &nf_ct_icmp_timeout,
 320                 .maxlen         = sizeof(unsigned int),
 321                 .mode           = 0644,
 322                 .proc_handler   = &proc_dointvec_jiffies,
 323         },
 324         {
 325                 .ctl_name = 0
 326         }
 327 };
 328 #ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
 329 static struct ctl_table icmp_compat_sysctl_table[] = {
 330         {
 331                 .ctl_name       = NET_IPV4_NF_CONNTRACK_ICMP_TIMEOUT,
 332                 .procname       = "ip_conntrack_icmp_timeout",
 333                 .data           = &nf_ct_icmp_timeout,
 334                 .maxlen         = sizeof(unsigned int),
 335                 .mode           = 0644,
 336                 .proc_handler   = &proc_dointvec_jiffies,
 337         },
 338         {
 339                 .ctl_name = 0
 340         }
 341 };
 342 #endif /* CONFIG_NF_CONNTRACK_PROC_COMPAT */
 343 #endif /* CONFIG_SYSCTL */
 344
 345 struct nf_conntrack_l4proto nf_conntrack_l4proto_icmp =
 346 {
 347         .l3proto                = PF_INET,
 348         .l4proto                = IPPROTO_ICMP,
 349         .name                   = "icmp",
 350         .pkt_to_tuple           = icmp_pkt_to_tuple,
 351         .invert_tuple           = icmp_invert_tuple,
 352         .print_tuple            = icmp_print_tuple,
 353         .print_conntrack        = icmp_print_conntrack,
 354         .packet                 = icmp_packet,
 355         .new                    = icmp_new,
 356         .error                  = icmp_error,
 357         .destroy                = NULL,
 358         .me                     = NULL,
 359 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
 360         .tuple_to_nfattr        = icmp_tuple_to_nfattr,
 361         .nfattr_to_tuple        = icmp_nfattr_to_tuple,
 362 #endif
 363 #ifdef CONFIG_SYSCTL
 364         .ctl_table_header       = &icmp_sysctl_header,
 365         .ctl_table              = icmp_sysctl_table,
 366 #ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
 367         .ctl_compat_table       = icmp_compat_sysctl_table,
 368 #endif
 369 #endif
 370 };
 371 EXPORT_SYMBOL_GPL(nf_conntrack_l4proto_icmp);