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/sched.h>
  16 #include <linux/timer.h>
  17 #include <linux/netfilter.h>
  18 #include <linux/in.h>
  19 #include <linux/icmp.h>
  20 #include <linux/seq_file.h>
  21 #include <net/ip.h>
  22 #include <net/checksum.h>
  23 #include <linux/netfilter_ipv4.h>
  24 #include <net/netfilter/nf_conntrack_tuple.h>
  25 #include <net/netfilter/nf_conntrack_protocol.h>
  26 #include <net/netfilter/nf_conntrack_core.h>
  27
  28 unsigned long nf_ct_icmp_timeout = 30*HZ;
  29
  30 #if 0
  31 #define DEBUGP printk
  32 #else
  33 #define DEBUGP(format, args...)
  34 #endif
  35
  36 static int icmp_pkt_to_tuple(const struct sk_buff *skb,
  37                              unsigned int dataoff,
  38                              struct nf_conntrack_tuple *tuple)
  39 {
  40         struct icmphdr _hdr, *hp;
  41
  42         hp = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
  43         if (hp == NULL)
  44                 return 0;
  45
  46         tuple->dst.u.icmp.type = hp->type;
  47         tuple->src.u.icmp.id = hp->un.echo.id;
  48         tuple->dst.u.icmp.code = hp->code;
  49
  50         return 1;
  51 }
  52
  53 /* Add 1; spaces filled with 0. */
  54 static const u_int8_t invmap[] = {
  55         [ICMP_ECHO] = ICMP_ECHOREPLY + 1,
  56         [ICMP_ECHOREPLY] = ICMP_ECHO + 1,
  57         [ICMP_TIMESTAMP] = ICMP_TIMESTAMPREPLY + 1,
  58         [ICMP_TIMESTAMPREPLY] = ICMP_TIMESTAMP + 1,
  59         [ICMP_INFO_REQUEST] = ICMP_INFO_REPLY + 1,
  60         [ICMP_INFO_REPLY] = ICMP_INFO_REQUEST + 1,
  61         [ICMP_ADDRESS] = ICMP_ADDRESSREPLY + 1,
  62         [ICMP_ADDRESSREPLY] = ICMP_ADDRESS + 1
  63 };
  64
  65 static int icmp_invert_tuple(struct nf_conntrack_tuple *tuple,
  66                              const struct nf_conntrack_tuple *orig)
  67 {
  68         if (orig->dst.u.icmp.type >= sizeof(invmap)
  69             || !invmap[orig->dst.u.icmp.type])
  70                 return 0;
  71
  72         tuple->src.u.icmp.id = orig->src.u.icmp.id;
  73         tuple->dst.u.icmp.type = invmap[orig->dst.u.icmp.type] - 1;
  74         tuple->dst.u.icmp.code = orig->dst.u.icmp.code;
  75         return 1;
  76 }
  77
  78 /* Print out the per-protocol part of the tuple. */
  79 static int icmp_print_tuple(struct seq_file *s,
  80                             const struct nf_conntrack_tuple *tuple)
  81 {
  82         return seq_printf(s, "type=%u code=%u id=%u ",
  83                           tuple->dst.u.icmp.type,
  84                           tuple->dst.u.icmp.code,
  85                           ntohs(tuple->src.u.icmp.id));
  86 }
  87
  88 /* Print out the private part of the conntrack. */
  89 static int icmp_print_conntrack(struct seq_file *s,
  90                                 const struct nf_conn *conntrack)
  91 {
  92         return 0;
  93 }
  94
  95 /* Returns verdict for packet, or -1 for invalid. */
  96 static int icmp_packet(struct nf_conn *ct,
  97                        const struct sk_buff *skb,
  98                        unsigned int dataoff,
  99                        enum ip_conntrack_info ctinfo,
 100                        int pf,
 101                        unsigned int hooknum)
 102 {
 103         /* Try to delete connection immediately after all replies:
 104            won't actually vanish as we still have skb, and del_timer
 105            means this will only run once even if count hits zero twice
 106            (theoretically possible with SMP) */
 107         if (CTINFO2DIR(ctinfo) == IP_CT_DIR_REPLY) {
 108                 if (atomic_dec_and_test(&ct->proto.icmp.count)
 109                     && del_timer(&ct->timeout))
 110                         ct->timeout.function((unsigned long)ct);
 111         } else {
 112                 atomic_inc(&ct->proto.icmp.count);
 113                 nf_conntrack_event_cache(IPCT_PROTOINFO_VOLATILE, skb);
 114                 nf_ct_refresh_acct(ct, ctinfo, skb, nf_ct_icmp_timeout);
 115         }
 116
 117         return NF_ACCEPT;
 118 }
 119
 120 /* Called when a new connection for this protocol found. */
 121 static int icmp_new(struct nf_conn *conntrack,
 122                     const struct sk_buff *skb, unsigned int dataoff)
 123 {
 124         static const u_int8_t valid_new[] = {
 125                 [ICMP_ECHO] = 1,
 126                 [ICMP_TIMESTAMP] = 1,
 127                 [ICMP_INFO_REQUEST] = 1,
 128                 [ICMP_ADDRESS] = 1
 129         };
 130
 131         if (conntrack->tuplehash[0].tuple.dst.u.icmp.type >= sizeof(valid_new)
 132             || !valid_new[conntrack->tuplehash[0].tuple.dst.u.icmp.type]) {
 133                 /* Can't create a new ICMP `conn' with this. */
 134                 DEBUGP("icmp: can't create new conn with type %u\n",
 135                        conntrack->tuplehash[0].tuple.dst.u.icmp.type);
 136                 NF_CT_DUMP_TUPLE(&conntrack->tuplehash[0].tuple);
 137                 return 0;
 138         }
 139         atomic_set(&conntrack->proto.icmp.count, 0);
 140         return 1;
 141 }
 142
 143 extern struct nf_conntrack_l3proto nf_conntrack_l3proto_ipv4;
 144 /* Returns conntrack if it dealt with ICMP, and filled in skb fields */
 145 static int
 146 icmp_error_message(struct sk_buff *skb,
 147                  enum ip_conntrack_info *ctinfo,
 148                  unsigned int hooknum)
 149 {
 150         struct nf_conntrack_tuple innertuple, origtuple;
 151         struct {
 152                 struct icmphdr icmp;
 153                 struct iphdr ip;
 154         } _in, *inside;
 155         struct nf_conntrack_protocol *innerproto;
 156         struct nf_conntrack_tuple_hash *h;
 157         int dataoff;
 158
 159         NF_CT_ASSERT(skb->nfct == NULL);
 160
 161         /* Not enough header? */
 162         inside = skb_header_pointer(skb, skb->nh.iph->ihl*4, sizeof(_in), &_in);
 163         if (inside == NULL)
 164                 return -NF_ACCEPT;
 165
 166         /* Ignore ICMP's containing fragments (shouldn't happen) */
 167         if (inside->ip.frag_off & htons(IP_OFFSET)) {
 168                 DEBUGP("icmp_error_message: fragment of proto %u\n",
 169                        inside->ip.protocol);
 170                 return -NF_ACCEPT;
 171         }
 172
 173         innerproto = __nf_ct_proto_find(PF_INET, inside->ip.protocol);
 174         dataoff = skb->nh.iph->ihl*4 + sizeof(inside->icmp);
 175         /* Are they talking about one of our connections? */
 176         if (!nf_ct_get_tuple(skb, dataoff, dataoff + inside->ip.ihl*4, PF_INET,
 177                              inside->ip.protocol, &origtuple,
 178                              &nf_conntrack_l3proto_ipv4, innerproto)) {
 179                 DEBUGP("icmp_error_message: ! get_tuple p=%u",
 180                        inside->ip.protocol);
 181                 return -NF_ACCEPT;
 182         }
 183
 184         /* Ordinarily, we'd expect the inverted tupleproto, but it's
 185            been preserved inside the ICMP. */
 186         if (!nf_ct_invert_tuple(&innertuple, &origtuple,
 187                                 &nf_conntrack_l3proto_ipv4, innerproto)) {
 188                 DEBUGP("icmp_error_message: no match\n");
 189                 return -NF_ACCEPT;
 190         }
 191
 192         *ctinfo = IP_CT_RELATED;
 193
 194         h = nf_conntrack_find_get(&innertuple, NULL);
 195         if (!h) {
 196                 /* Locally generated ICMPs will match inverted if they
 197                    haven't been SNAT'ed yet */
 198                 /* FIXME: NAT code has to handle half-done double NAT --RR */
 199                 if (hooknum == NF_IP_LOCAL_OUT)
 200                         h = nf_conntrack_find_get(&origtuple, NULL);
 201
 202                 if (!h) {
 203                         DEBUGP("icmp_error_message: no match\n");
 204                         return -NF_ACCEPT;
 205                 }
 206
 207                 /* Reverse direction from that found */
 208                 if (NF_CT_DIRECTION(h) == IP_CT_DIR_REPLY)
 209                         *ctinfo += IP_CT_IS_REPLY;
 210         } else {
 211                 if (NF_CT_DIRECTION(h) == IP_CT_DIR_REPLY)
 212                         *ctinfo += IP_CT_IS_REPLY;
 213         }
 214
 215         /* Update skb to refer to this connection */
 216         skb->nfct = &nf_ct_tuplehash_to_ctrack(h)->ct_general;
 217         skb->nfctinfo = *ctinfo;
 218         return -NF_ACCEPT;
 219 }
 220
 221 /* Small and modified version of icmp_rcv */
 222 static int
 223 icmp_error(struct sk_buff *skb, unsigned int dataoff,
 224            enum ip_conntrack_info *ctinfo, int pf, unsigned int hooknum)
 225 {
 226         struct icmphdr _ih, *icmph;
 227
 228         /* Not enough header? */
 229         icmph = skb_header_pointer(skb, skb->nh.iph->ihl*4, sizeof(_ih), &_ih);
 230         if (icmph == NULL) {
 231                 if (LOG_INVALID(IPPROTO_ICMP))
 232                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 233                                       "nf_ct_icmp: short packet ");
 234                 return -NF_ACCEPT;
 235         }
 236
 237         /* See ip_conntrack_proto_tcp.c */
 238         if (hooknum != NF_IP_PRE_ROUTING)
 239                 goto checksum_skipped;
 240
 241         switch (skb->ip_summed) {
 242         case CHECKSUM_HW:
 243                 if (!(u16)csum_fold(skb->csum))
 244                         break;
 245                 if (LOG_INVALID(IPPROTO_ICMP))
 246                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 247                                       "nf_ct_icmp: bad HW ICMP checksum ");
 248                 return -NF_ACCEPT;
 249         case CHECKSUM_NONE:
 250                 if ((u16)csum_fold(skb_checksum(skb, 0, skb->len, 0))) {
 251                         if (LOG_INVALID(IPPROTO_ICMP))
 252                                 nf_log_packet(PF_INET, 0, skb, NULL, NULL,
 253                                               NULL,
 254                                               "nf_ct_icmp: bad ICMP checksum ");
 255                         return -NF_ACCEPT;
 256                 }
 257         default:
 258                 break;
 259         }
 260
 261 checksum_skipped:
 262         /*
 263          *      18 is the highest 'known' ICMP type. Anything else is a mystery
 264          *
 265          *      RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
 266          *                discarded.
 267          */
 268         if (icmph->type > NR_ICMP_TYPES) {
 269                 if (LOG_INVALID(IPPROTO_ICMP))
 270                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 271                                       "nf_ct_icmp: invalid ICMP type ");
 272                 return -NF_ACCEPT;
 273         }
 274
 275         /* Need to track icmp error message? */
 276         if (icmph->type != ICMP_DEST_UNREACH
 277             && icmph->type != ICMP_SOURCE_QUENCH
 278             && icmph->type != ICMP_TIME_EXCEEDED
 279             && icmph->type != ICMP_PARAMETERPROB
 280             && icmph->type != ICMP_REDIRECT)
 281                 return NF_ACCEPT;
 282
 283         return icmp_error_message(skb, ctinfo, hooknum);
 284 }
 285
 286 #if defined(CONFIG_NF_CT_NETLINK) || \
 287     defined(CONFIG_NF_CT_NETLINK_MODULE)
 288
 289 #include <linux/netfilter/nfnetlink.h>
 290 #include <linux/netfilter/nfnetlink_conntrack.h>
 291
 292 static int icmp_tuple_to_nfattr(struct sk_buff *skb,
 293                                 const struct nf_conntrack_tuple *t)
 294 {
 295         NFA_PUT(skb, CTA_PROTO_ICMP_ID, sizeof(u_int16_t),
 296                 &t->src.u.icmp.id);
 297         NFA_PUT(skb, CTA_PROTO_ICMP_TYPE, sizeof(u_int8_t),
 298                 &t->dst.u.icmp.type);
 299         NFA_PUT(skb, CTA_PROTO_ICMP_CODE, sizeof(u_int8_t),
 300                 &t->dst.u.icmp.code);
 301
 302         return 0;
 303
 304 nfattr_failure:
 305         return -1;
 306 }
 307
 308 static const size_t cta_min_proto[CTA_PROTO_MAX] = {
 309         [CTA_PROTO_ICMP_TYPE-1] = sizeof(u_int8_t),
 310         [CTA_PROTO_ICMP_CODE-1] = sizeof(u_int8_t),
 311         [CTA_PROTO_ICMP_ID-1]   = sizeof(u_int16_t)
 312 };
 313
 314 static int icmp_nfattr_to_tuple(struct nfattr *tb[],
 315                                 struct nf_conntrack_tuple *tuple)
 316 {
 317         if (!tb[CTA_PROTO_ICMP_TYPE-1]
 318             || !tb[CTA_PROTO_ICMP_CODE-1]
 319             || !tb[CTA_PROTO_ICMP_ID-1])
 320                 return -EINVAL;
 321
 322         if (nfattr_bad_size(tb, CTA_PROTO_MAX, cta_min_proto))
 323                 return -EINVAL;
 324
 325         tuple->dst.u.icmp.type =
 326                         *(u_int8_t *)NFA_DATA(tb[CTA_PROTO_ICMP_TYPE-1]);
 327         tuple->dst.u.icmp.code =
 328                         *(u_int8_t *)NFA_DATA(tb[CTA_PROTO_ICMP_CODE-1]);
 329         tuple->src.u.icmp.id =
 330                         *(u_int16_t *)NFA_DATA(tb[CTA_PROTO_ICMP_ID-1]);
 331
 332         if (tuple->dst.u.icmp.type >= sizeof(invmap)
 333             || !invmap[tuple->dst.u.icmp.type])
 334                 return -EINVAL;
 335
 336         return 0;
 337 }
 338 #endif
 339
 340 struct nf_conntrack_protocol nf_conntrack_protocol_icmp =
 341 {
 342         .list                   = { NULL, NULL },
 343         .l3proto                = PF_INET,
 344         .proto                  = IPPROTO_ICMP,
 345         .name                   = "icmp",
 346         .pkt_to_tuple           = icmp_pkt_to_tuple,
 347         .invert_tuple           = icmp_invert_tuple,
 348         .print_tuple            = icmp_print_tuple,
 349         .print_conntrack        = icmp_print_conntrack,
 350         .packet                 = icmp_packet,
 351         .new                    = icmp_new,
 352         .error                  = icmp_error,
 353         .destroy                = NULL,
 354         .me                     = NULL,
 355 #if defined(CONFIG_NF_CT_NETLINK) || \
 356     defined(CONFIG_NF_CT_NETLINK_MODULE)
 357         .tuple_to_nfattr        = icmp_tuple_to_nfattr,
 358         .nfattr_to_tuple        = icmp_nfattr_to_tuple,
 359 #endif
 360 };
 361
 362 EXPORT_SYMBOL(nf_conntrack_protocol_icmp);