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  * 16 Dec 2003: Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
   9  *      - enable working with Layer 3 protocol independent connection tracking.
  10  *
  11  * Derived from net/ipv4/netfilter/ip_conntrack_proto_icmp.c
  12  */
  13
  14 #include <linux/types.h>
  15 #include <linux/timer.h>
  16 #include <linux/netfilter.h>
  17 #include <linux/in.h>
  18 #include <linux/icmp.h>
  19 #include <linux/seq_file.h>
  20 #include <net/ip.h>
  21 #include <net/checksum.h>
  22 #include <linux/netfilter_ipv4.h>
  23 #include <net/netfilter/nf_conntrack_tuple.h>
  24 #include <net/netfilter/nf_conntrack_l4proto.h>
  25 #include <net/netfilter/nf_conntrack_core.h>
  26
  27 static unsigned long nf_ct_icmp_timeout __read_mostly = 30*HZ;
  28
  29 #if 0
  30 #define DEBUGP printk
  31 #else
  32 #define DEBUGP(format, args...)
  33 #endif
  34
  35 static int icmp_pkt_to_tuple(const struct sk_buff *skb,
  36                              unsigned int dataoff,
  37                              struct nf_conntrack_tuple *tuple)
  38 {
  39         struct icmphdr _hdr, *hp;
  40
  41         hp = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
  42         if (hp == NULL)
  43                 return 0;
  44
  45         tuple->dst.u.icmp.type = hp->type;
  46         tuple->src.u.icmp.id = hp->un.echo.id;
  47         tuple->dst.u.icmp.code = hp->code;
  48
  49         return 1;
  50 }
  51
  52 /* Add 1; spaces filled with 0. */
  53 static const 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
  64 static int icmp_invert_tuple(struct nf_conntrack_tuple *tuple,
  65                              const struct nf_conntrack_tuple *orig)
  66 {
  67         if (orig->dst.u.icmp.type >= sizeof(invmap)
  68             || !invmap[orig->dst.u.icmp.type])
  69                 return 0;
  70
  71         tuple->src.u.icmp.id = orig->src.u.icmp.id;
  72         tuple->dst.u.icmp.type = invmap[orig->dst.u.icmp.type] - 1;
  73         tuple->dst.u.icmp.code = orig->dst.u.icmp.code;
  74         return 1;
  75 }
  76
  77 /* Print out the per-protocol part of the tuple. */
  78 static int icmp_print_tuple(struct seq_file *s,
  79                             const struct nf_conntrack_tuple *tuple)
  80 {
  81         return seq_printf(s, "type=%u code=%u id=%u ",
  82                           tuple->dst.u.icmp.type,
  83                           tuple->dst.u.icmp.code,
  84                           ntohs(tuple->src.u.icmp.id));
  85 }
  86
  87 /* Print out the private part of the conntrack. */
  88 static int icmp_print_conntrack(struct seq_file *s,
  89                                 const struct nf_conn *conntrack)
  90 {
  91         return 0;
  92 }
  93
  94 /* Returns verdict for packet, or -1 for invalid. */
  95 static int icmp_packet(struct nf_conn *ct,
  96                        const struct sk_buff *skb,
  97                        unsigned int dataoff,
  98                        enum ip_conntrack_info ctinfo,
  99                        int pf,
 100                        unsigned int hooknum)
 101 {
 102         /* Try to delete connection immediately after all replies:
 103            won't actually vanish as we still have skb, and del_timer
 104            means this will only run once even if count hits zero twice
 105            (theoretically possible with SMP) */
 106         if (CTINFO2DIR(ctinfo) == IP_CT_DIR_REPLY) {
 107                 if (atomic_dec_and_test(&ct->proto.icmp.count)
 108                     && del_timer(&ct->timeout))
 109                         ct->timeout.function((unsigned long)ct);
 110         } else {
 111                 atomic_inc(&ct->proto.icmp.count);
 112                 nf_conntrack_event_cache(IPCT_PROTOINFO_VOLATILE, skb);
 113                 nf_ct_refresh_acct(ct, ctinfo, skb, nf_ct_icmp_timeout);
 114         }
 115
 116         return NF_ACCEPT;
 117 }
 118
 119 /* Called when a new connection for this protocol found. */
 120 static int icmp_new(struct nf_conn *conntrack,
 121                     const struct sk_buff *skb, unsigned int dataoff)
 122 {
 123         static const u_int8_t valid_new[] = {
 124                 [ICMP_ECHO] = 1,
 125                 [ICMP_TIMESTAMP] = 1,
 126                 [ICMP_INFO_REQUEST] = 1,
 127                 [ICMP_ADDRESS] = 1
 128         };
 129
 130         if (conntrack->tuplehash[0].tuple.dst.u.icmp.type >= sizeof(valid_new)
 131             || !valid_new[conntrack->tuplehash[0].tuple.dst.u.icmp.type]) {
 132                 /* Can't create a new ICMP `conn' with this. */
 133                 DEBUGP("icmp: can't create new conn with type %u\n",
 134                        conntrack->tuplehash[0].tuple.dst.u.icmp.type);
 135                 NF_CT_DUMP_TUPLE(&conntrack->tuplehash[0].tuple);
 136                 return 0;
 137         }
 138         atomic_set(&conntrack->proto.icmp.count, 0);
 139         return 1;
 140 }
 141
 142 extern struct nf_conntrack_l3proto nf_conntrack_l3proto_ipv4;
 143 /* Returns conntrack if it dealt with ICMP, and filled in skb fields */
 144 static int
 145 icmp_error_message(struct sk_buff *skb,
 146                  enum ip_conntrack_info *ctinfo,
 147                  unsigned int hooknum)
 148 {
 149         struct nf_conntrack_tuple innertuple, origtuple;
 150         struct {
 151                 struct icmphdr icmp;
 152                 struct iphdr ip;
 153         } _in, *inside;
 154         struct nf_conntrack_l4proto *innerproto;
 155         struct nf_conntrack_tuple_hash *h;
 156         int dataoff;
 157
 158         NF_CT_ASSERT(skb->nfct == NULL);
 159
 160         /* Not enough header? */
 161         inside = skb_header_pointer(skb, skb->nh.iph->ihl*4, sizeof(_in), &_in);
 162         if (inside == NULL)
 163                 return -NF_ACCEPT;
 164
 165         /* Ignore ICMP's containing fragments (shouldn't happen) */
 166         if (inside->ip.frag_off & htons(IP_OFFSET)) {
 167                 DEBUGP("icmp_error_message: fragment of proto %u\n",
 168                        inside->ip.protocol);
 169                 return -NF_ACCEPT;
 170         }
 171
 172         /* rcu_read_lock()ed by nf_hook_slow */
 173         innerproto = __nf_ct_l4proto_find(PF_INET, inside->ip.protocol);
 174
 175         dataoff = skb->nh.iph->ihl*4 + sizeof(inside->icmp);
 176         /* Are they talking about one of our connections? */
 177         if (!nf_ct_get_tuple(skb, dataoff, dataoff + inside->ip.ihl*4, PF_INET,
 178                              inside->ip.protocol, &origtuple,
 179                              &nf_conntrack_l3proto_ipv4, innerproto)) {
 180                 DEBUGP("icmp_error_message: ! get_tuple p=%u",
 181                        inside->ip.protocol);
 182                 return -NF_ACCEPT;
 183         }
 184
 185         /* Ordinarily, we'd expect the inverted tupleproto, but it's
 186            been preserved inside the ICMP. */
 187         if (!nf_ct_invert_tuple(&innertuple, &origtuple,
 188                                 &nf_conntrack_l3proto_ipv4, innerproto)) {
 189                 DEBUGP("icmp_error_message: no match\n");
 190                 return -NF_ACCEPT;
 191         }
 192
 193         *ctinfo = IP_CT_RELATED;
 194
 195         h = nf_conntrack_find_get(&innertuple, NULL);
 196         if (!h) {
 197                 /* Locally generated ICMPs will match inverted if they
 198                    haven't been SNAT'ed yet */
 199                 /* FIXME: NAT code has to handle half-done double NAT --RR */
 200                 if (hooknum == NF_IP_LOCAL_OUT)
 201                         h = nf_conntrack_find_get(&origtuple, NULL);
 202
 203                 if (!h) {
 204                         DEBUGP("icmp_error_message: no match\n");
 205                         return -NF_ACCEPT;
 206                 }
 207
 208                 /* Reverse direction from that found */
 209                 if (NF_CT_DIRECTION(h) == IP_CT_DIR_REPLY)
 210                         *ctinfo += IP_CT_IS_REPLY;
 211         } else {
 212                 if (NF_CT_DIRECTION(h) == IP_CT_DIR_REPLY)
 213                         *ctinfo += IP_CT_IS_REPLY;
 214         }
 215
 216         /* Update skb to refer to this connection */
 217         skb->nfct = &nf_ct_tuplehash_to_ctrack(h)->ct_general;
 218         skb->nfctinfo = *ctinfo;
 219         return -NF_ACCEPT;
 220 }
 221
 222 /* Small and modified version of icmp_rcv */
 223 static int
 224 icmp_error(struct sk_buff *skb, unsigned int dataoff,
 225            enum ip_conntrack_info *ctinfo, int pf, unsigned int hooknum)
 226 {
 227         struct icmphdr _ih, *icmph;
 228
 229         /* Not enough header? */
 230         icmph = skb_header_pointer(skb, skb->nh.iph->ihl*4, sizeof(_ih), &_ih);
 231         if (icmph == NULL) {
 232                 if (LOG_INVALID(IPPROTO_ICMP))
 233                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 234                                       "nf_ct_icmp: short packet ");
 235                 return -NF_ACCEPT;
 236         }
 237
 238         /* See ip_conntrack_proto_tcp.c */
 239         if (nf_conntrack_checksum && hooknum == NF_IP_PRE_ROUTING &&
 240             nf_ip_checksum(skb, hooknum, dataoff, 0)) {
 241                 if (LOG_INVALID(IPPROTO_ICMP))
 242                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 243                                       "nf_ct_icmp: bad HW ICMP checksum ");
 244                 return -NF_ACCEPT;
 245         }
 246
 247         /*
 248          *      18 is the highest 'known' ICMP type. Anything else is a mystery
 249          *
 250          *      RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
 251          *                discarded.
 252          */
 253         if (icmph->type > NR_ICMP_TYPES) {
 254                 if (LOG_INVALID(IPPROTO_ICMP))
 255                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 256                                       "nf_ct_icmp: invalid ICMP type ");
 257                 return -NF_ACCEPT;
 258         }
 259
 260         /* Need to track icmp error message? */
 261         if (icmph->type != ICMP_DEST_UNREACH
 262             && icmph->type != ICMP_SOURCE_QUENCH
 263             && icmph->type != ICMP_TIME_EXCEEDED
 264             && icmph->type != ICMP_PARAMETERPROB
 265             && icmph->type != ICMP_REDIRECT)
 266                 return NF_ACCEPT;
 267
 268         return icmp_error_message(skb, ctinfo, hooknum);
 269 }
 270
 271 #if defined(CONFIG_NF_CT_NETLINK) || \
 272     defined(CONFIG_NF_CT_NETLINK_MODULE)
 273
 274 #include <linux/netfilter/nfnetlink.h>
 275 #include <linux/netfilter/nfnetlink_conntrack.h>
 276
 277 static int icmp_tuple_to_nfattr(struct sk_buff *skb,
 278                                 const struct nf_conntrack_tuple *t)
 279 {
 280         NFA_PUT(skb, CTA_PROTO_ICMP_ID, sizeof(u_int16_t),
 281                 &t->src.u.icmp.id);
 282         NFA_PUT(skb, CTA_PROTO_ICMP_TYPE, sizeof(u_int8_t),
 283                 &t->dst.u.icmp.type);
 284         NFA_PUT(skb, CTA_PROTO_ICMP_CODE, sizeof(u_int8_t),
 285                 &t->dst.u.icmp.code);
 286
 287         return 0;
 288
 289 nfattr_failure:
 290         return -1;
 291 }
 292
 293 static const size_t cta_min_proto[CTA_PROTO_MAX] = {
 294         [CTA_PROTO_ICMP_TYPE-1] = sizeof(u_int8_t),
 295         [CTA_PROTO_ICMP_CODE-1] = sizeof(u_int8_t),
 296         [CTA_PROTO_ICMP_ID-1]   = sizeof(u_int16_t)
 297 };
 298
 299 static int icmp_nfattr_to_tuple(struct nfattr *tb[],
 300                                 struct nf_conntrack_tuple *tuple)
 301 {
 302         if (!tb[CTA_PROTO_ICMP_TYPE-1]
 303             || !tb[CTA_PROTO_ICMP_CODE-1]
 304             || !tb[CTA_PROTO_ICMP_ID-1])
 305                 return -EINVAL;
 306
 307         if (nfattr_bad_size(tb, CTA_PROTO_MAX, cta_min_proto))
 308                 return -EINVAL;
 309
 310         tuple->dst.u.icmp.type =
 311                         *(u_int8_t *)NFA_DATA(tb[CTA_PROTO_ICMP_TYPE-1]);
 312         tuple->dst.u.icmp.code =
 313                         *(u_int8_t *)NFA_DATA(tb[CTA_PROTO_ICMP_CODE-1]);
 314         tuple->src.u.icmp.id =
 315                         *(__be16 *)NFA_DATA(tb[CTA_PROTO_ICMP_ID-1]);
 316
 317         if (tuple->dst.u.icmp.type >= sizeof(invmap)
 318             || !invmap[tuple->dst.u.icmp.type])
 319                 return -EINVAL;
 320
 321         return 0;
 322 }
 323 #endif
 324
 325 #ifdef CONFIG_SYSCTL
 326 static struct ctl_table_header *icmp_sysctl_header;
 327 static struct ctl_table icmp_sysctl_table[] = {
 328         {
 329                 .ctl_name       = NET_NF_CONNTRACK_ICMP_TIMEOUT,
 330                 .procname       = "nf_conntrack_icmp_timeout",
 331                 .data           = &nf_ct_icmp_timeout,
 332                 .maxlen         = sizeof(unsigned int),
 333                 .mode           = 0644,
 334                 .proc_handler   = &proc_dointvec_jiffies,
 335         },
 336         {
 337                 .ctl_name = 0
 338         }
 339 };
 340 #ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
 341 static struct ctl_table icmp_compat_sysctl_table[] = {
 342         {
 343                 .ctl_name       = NET_IPV4_NF_CONNTRACK_ICMP_TIMEOUT,
 344                 .procname       = "ip_conntrack_icmp_timeout",
 345                 .data           = &nf_ct_icmp_timeout,
 346                 .maxlen         = sizeof(unsigned int),
 347                 .mode           = 0644,
 348                 .proc_handler   = &proc_dointvec_jiffies,
 349         },
 350         {
 351                 .ctl_name = 0
 352         }
 353 };
 354 #endif /* CONFIG_NF_CONNTRACK_PROC_COMPAT */
 355 #endif /* CONFIG_SYSCTL */
 356
 357 struct nf_conntrack_l4proto nf_conntrack_l4proto_icmp =
 358 {
 359         .l3proto                = PF_INET,
 360         .l4proto                = IPPROTO_ICMP,
 361         .name                   = "icmp",
 362         .pkt_to_tuple           = icmp_pkt_to_tuple,
 363         .invert_tuple           = icmp_invert_tuple,
 364         .print_tuple            = icmp_print_tuple,
 365         .print_conntrack        = icmp_print_conntrack,
 366         .packet                 = icmp_packet,
 367         .new                    = icmp_new,
 368         .error                  = icmp_error,
 369         .destroy                = NULL,
 370         .me                     = NULL,
 371 #if defined(CONFIG_NF_CT_NETLINK) || \
 372     defined(CONFIG_NF_CT_NETLINK_MODULE)
 373         .tuple_to_nfattr        = icmp_tuple_to_nfattr,
 374         .nfattr_to_tuple        = icmp_nfattr_to_tuple,
 375 #endif
 376 #ifdef CONFIG_SYSCTL
 377         .ctl_table_header       = &icmp_sysctl_header,
 378         .ctl_table              = icmp_sysctl_table,
 379 #ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
 380         .ctl_compat_table       = icmp_compat_sysctl_table,
 381 #endif
 382 #endif
 383 };
 384 EXPORT_SYMBOL_GPL(nf_conntrack_l4proto_icmp);