net/netfilter/nf_conntrack_proto_gre.c

   1 /*
   2  * ip_conntrack_proto_gre.c - Version 3.0
   3  *
   4  * Connection tracking protocol helper module for GRE.
   5  *
   6  * GRE is a generic encapsulation protocol, which is generally not very
   7  * suited for NAT, as it has no protocol-specific part as port numbers.
   8  *
   9  * It has an optional key field, which may help us distinguishing two
  10  * connections between the same two hosts.
  11  *
  12  * GRE is defined in RFC 1701 and RFC 1702, as well as RFC 2784
  13  *
  14  * PPTP is built on top of a modified version of GRE, and has a mandatory
  15  * field called "CallID", which serves us for the same purpose as the key
  16  * field in plain GRE.
  17  *
  18  * Documentation about PPTP can be found in RFC 2637
  19  *
  20  * (C) 2000-2005 by Harald Welte <laforge@gnumonks.org>
  21  *
  22  * Development of this code funded by Astaro AG (http://www.astaro.com/)
  23  *
  24  */
  25
  26 #include <linux/module.h>
  27 #include <linux/types.h>
  28 #include <linux/timer.h>
  29 #include <linux/list.h>
  30 #include <linux/seq_file.h>
  31 #include <linux/in.h>
  32 #include <linux/netdevice.h>
  33 #include <linux/skbuff.h>
  34 #include <linux/slab.h>
  35 #include <net/dst.h>
  36 #include <net/net_namespace.h>
  37 #include <net/netns/generic.h>
  38 #include <net/netfilter/nf_conntrack_l4proto.h>
  39 #include <net/netfilter/nf_conntrack_helper.h>
  40 #include <net/netfilter/nf_conntrack_core.h>
  41 #include <linux/netfilter/nf_conntrack_proto_gre.h>
  42 #include <linux/netfilter/nf_conntrack_pptp.h>
  43
  44 enum grep_conntrack {
  45         GRE_CT_UNREPLIED,
  46         GRE_CT_REPLIED,
  47         GRE_CT_MAX
  48 };
  49
  50 static unsigned int gre_timeouts[GRE_CT_MAX] = {
  51         [GRE_CT_UNREPLIED]      = 30*HZ,
  52         [GRE_CT_REPLIED]        = 180*HZ,
  53 };
  54
  55 static int proto_gre_net_id __read_mostly;
  56 struct netns_proto_gre {
  57         rwlock_t                keymap_lock;
  58         struct list_head        keymap_list;
  59 };
  60
  61 void nf_ct_gre_keymap_flush(struct net *net)
  62 {
  63         struct netns_proto_gre *net_gre = net_generic(net, proto_gre_net_id);
  64         struct nf_ct_gre_keymap *km, *tmp;
  65
  66         write_lock_bh(&net_gre->keymap_lock);
  67         list_for_each_entry_safe(km, tmp, &net_gre->keymap_list, list) {
  68                 list_del(&km->list);
  69                 kfree(km);
  70         }
  71         write_unlock_bh(&net_gre->keymap_lock);
  72 }
  73 EXPORT_SYMBOL(nf_ct_gre_keymap_flush);
  74
  75 static inline int gre_key_cmpfn(const struct nf_ct_gre_keymap *km,
  76                                 const struct nf_conntrack_tuple *t)
  77 {
  78         return km->tuple.src.l3num == t->src.l3num &&
  79                !memcmp(&km->tuple.src.u3, &t->src.u3, sizeof(t->src.u3)) &&
  80                !memcmp(&km->tuple.dst.u3, &t->dst.u3, sizeof(t->dst.u3)) &&
  81                km->tuple.dst.protonum == t->dst.protonum &&
  82                km->tuple.dst.u.all == t->dst.u.all;
  83 }
  84
  85 /* look up the source key for a given tuple */
  86 static __be16 gre_keymap_lookup(struct net *net, struct nf_conntrack_tuple *t)
  87 {
  88         struct netns_proto_gre *net_gre = net_generic(net, proto_gre_net_id);
  89         struct nf_ct_gre_keymap *km;
  90         __be16 key = 0;
  91
  92         read_lock_bh(&net_gre->keymap_lock);
  93         list_for_each_entry(km, &net_gre->keymap_list, list) {
  94                 if (gre_key_cmpfn(km, t)) {
  95                         key = km->tuple.src.u.gre.key;
  96                         break;
  97                 }
  98         }
  99         read_unlock_bh(&net_gre->keymap_lock);
 100
 101         pr_debug("lookup src key 0x%x for ", key);
 102         nf_ct_dump_tuple(t);
 103
 104         return key;
 105 }
 106
 107 /* add a single keymap entry, associate with specified master ct */
 108 int nf_ct_gre_keymap_add(struct nf_conn *ct, enum ip_conntrack_dir dir,
 109                          struct nf_conntrack_tuple *t)
 110 {
 111         struct net *net = nf_ct_net(ct);
 112         struct netns_proto_gre *net_gre = net_generic(net, proto_gre_net_id);
 113         struct nf_conn_help *help = nfct_help(ct);
 114         struct nf_ct_gre_keymap **kmp, *km;
 115
 116         kmp = &help->help.ct_pptp_info.keymap[dir];
 117         if (*kmp) {
 118                 /* check whether it's a retransmission */
 119                 read_lock_bh(&net_gre->keymap_lock);
 120                 list_for_each_entry(km, &net_gre->keymap_list, list) {
 121                         if (gre_key_cmpfn(km, t) && km == *kmp) {
 122                                 read_unlock_bh(&net_gre->keymap_lock);
 123                                 return 0;
 124                         }
 125                 }
 126                 read_unlock_bh(&net_gre->keymap_lock);
 127                 pr_debug("trying to override keymap_%s for ct %p\n",
 128                          dir == IP_CT_DIR_REPLY ? "reply" : "orig", ct);
 129                 return -EEXIST;
 130         }
 131
 132         km = kmalloc(sizeof(*km), GFP_ATOMIC);
 133         if (!km)
 134                 return -ENOMEM;
 135         memcpy(&km->tuple, t, sizeof(*t));
 136         *kmp = km;
 137
 138         pr_debug("adding new entry %p: ", km);
 139         nf_ct_dump_tuple(&km->tuple);
 140
 141         write_lock_bh(&net_gre->keymap_lock);
 142         list_add_tail(&km->list, &net_gre->keymap_list);
 143         write_unlock_bh(&net_gre->keymap_lock);
 144
 145         return 0;
 146 }
 147 EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_add);
 148
 149 /* destroy the keymap entries associated with specified master ct */
 150 void nf_ct_gre_keymap_destroy(struct nf_conn *ct)
 151 {
 152         struct net *net = nf_ct_net(ct);
 153         struct netns_proto_gre *net_gre = net_generic(net, proto_gre_net_id);
 154         struct nf_conn_help *help = nfct_help(ct);
 155         enum ip_conntrack_dir dir;
 156
 157         pr_debug("entering for ct %p\n", ct);
 158
 159         write_lock_bh(&net_gre->keymap_lock);
 160         for (dir = IP_CT_DIR_ORIGINAL; dir < IP_CT_DIR_MAX; dir++) {
 161                 if (help->help.ct_pptp_info.keymap[dir]) {
 162                         pr_debug("removing %p from list\n",
 163                                  help->help.ct_pptp_info.keymap[dir]);
 164                         list_del(&help->help.ct_pptp_info.keymap[dir]->list);
 165                         kfree(help->help.ct_pptp_info.keymap[dir]);
 166                         help->help.ct_pptp_info.keymap[dir] = NULL;
 167                 }
 168         }
 169         write_unlock_bh(&net_gre->keymap_lock);
 170 }
 171 EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_destroy);
 172
 173 /* PUBLIC CONNTRACK PROTO HELPER FUNCTIONS */
 174
 175 /* invert gre part of tuple */
 176 static bool gre_invert_tuple(struct nf_conntrack_tuple *tuple,
 177                              const struct nf_conntrack_tuple *orig)
 178 {
 179         tuple->dst.u.gre.key = orig->src.u.gre.key;
 180         tuple->src.u.gre.key = orig->dst.u.gre.key;
 181         return true;
 182 }
 183
 184 /* gre hdr info to tuple */
 185 static bool gre_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff,
 186                              struct nf_conntrack_tuple *tuple)
 187 {
 188         struct net *net = dev_net(skb->dev ? skb->dev : skb_dst(skb)->dev);
 189         const struct gre_hdr_pptp *pgrehdr;
 190         struct gre_hdr_pptp _pgrehdr;
 191         __be16 srckey;
 192         const struct gre_hdr *grehdr;
 193         struct gre_hdr _grehdr;
 194
 195         /* first only delinearize old RFC1701 GRE header */
 196         grehdr = skb_header_pointer(skb, dataoff, sizeof(_grehdr), &_grehdr);
 197         if (!grehdr || grehdr->version != GRE_VERSION_PPTP) {
 198                 /* try to behave like "nf_conntrack_proto_generic" */
 199                 tuple->src.u.all = 0;
 200                 tuple->dst.u.all = 0;
 201                 return true;
 202         }
 203
 204         /* PPTP header is variable length, only need up to the call_id field */
 205         pgrehdr = skb_header_pointer(skb, dataoff, 8, &_pgrehdr);
 206         if (!pgrehdr)
 207                 return true;
 208
 209         if (ntohs(grehdr->protocol) != GRE_PROTOCOL_PPTP) {
 210                 pr_debug("GRE_VERSION_PPTP but unknown proto\n");
 211                 return false;
 212         }
 213
 214         tuple->dst.u.gre.key = pgrehdr->call_id;
 215         srckey = gre_keymap_lookup(net, tuple);
 216         tuple->src.u.gre.key = srckey;
 217
 218         return true;
 219 }
 220
 221 /* print gre part of tuple */
 222 static int gre_print_tuple(struct seq_file *s,
 223                            const struct nf_conntrack_tuple *tuple)
 224 {
 225         return seq_printf(s, "srckey=0x%x dstkey=0x%x ",
 226                           ntohs(tuple->src.u.gre.key),
 227                           ntohs(tuple->dst.u.gre.key));
 228 }
 229
 230 /* print private data for conntrack */
 231 static int gre_print_conntrack(struct seq_file *s, struct nf_conn *ct)
 232 {
 233         return seq_printf(s, "timeout=%u, stream_timeout=%u ",
 234                           (ct->proto.gre.timeout / HZ),
 235                           (ct->proto.gre.stream_timeout / HZ));
 236 }
 237
 238 static unsigned int *gre_get_timeouts(struct net *net)
 239 {
 240         return gre_timeouts;
 241 }
 242
 243 /* Returns verdict for packet, and may modify conntrack */
 244 static int gre_packet(struct nf_conn *ct,
 245                       const struct sk_buff *skb,
 246                       unsigned int dataoff,
 247                       enum ip_conntrack_info ctinfo,
 248                       u_int8_t pf,
 249                       unsigned int hooknum,
 250                       unsigned int *timeouts)
 251 {
 252         /* If we've seen traffic both ways, this is a GRE connection.
 253          * Extend timeout. */
 254         if (ct->status & IPS_SEEN_REPLY) {
 255                 nf_ct_refresh_acct(ct, ctinfo, skb,
 256                                    ct->proto.gre.stream_timeout);
 257                 /* Also, more likely to be important, and not a probe. */
 258                 if (!test_and_set_bit(IPS_ASSURED_BIT, &ct->status))
 259                         nf_conntrack_event_cache(IPCT_ASSURED, ct);
 260         } else
 261                 nf_ct_refresh_acct(ct, ctinfo, skb,
 262                                    ct->proto.gre.timeout);
 263
 264         return NF_ACCEPT;
 265 }
 266
 267 /* Called when a new connection for this protocol found. */
 268 static bool gre_new(struct nf_conn *ct, const struct sk_buff *skb,
 269                     unsigned int dataoff, unsigned int *timeouts)
 270 {
 271         pr_debug(": ");
 272         nf_ct_dump_tuple(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
 273
 274         /* initialize to sane value.  Ideally a conntrack helper
 275          * (e.g. in case of pptp) is increasing them */
 276         ct->proto.gre.stream_timeout = timeouts[GRE_CT_REPLIED];
 277         ct->proto.gre.timeout = timeouts[GRE_CT_UNREPLIED];
 278
 279         return true;
 280 }
 281
 282 /* Called when a conntrack entry has already been removed from the hashes
 283  * and is about to be deleted from memory */
 284 static void gre_destroy(struct nf_conn *ct)
 285 {
 286         struct nf_conn *master = ct->master;
 287         pr_debug(" entering\n");
 288
 289         if (!master)
 290                 pr_debug("no master !?!\n");
 291         else
 292                 nf_ct_gre_keymap_destroy(master);
 293 }
 294
 295 #if IS_ENABLED(CONFIG_NF_CT_NETLINK_TIMEOUT)
 296
 297 #include <linux/netfilter/nfnetlink.h>
 298 #include <linux/netfilter/nfnetlink_cttimeout.h>
 299
 300 static int gre_timeout_nlattr_to_obj(struct nlattr *tb[], void *data)
 301 {
 302         unsigned int *timeouts = data;
 303
 304         /* set default timeouts for GRE. */
 305         timeouts[GRE_CT_UNREPLIED] = gre_timeouts[GRE_CT_UNREPLIED];
 306         timeouts[GRE_CT_REPLIED] = gre_timeouts[GRE_CT_REPLIED];
 307
 308         if (tb[CTA_TIMEOUT_GRE_UNREPLIED]) {
 309                 timeouts[GRE_CT_UNREPLIED] =
 310                         ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_UNREPLIED])) * HZ;
 311         }
 312         if (tb[CTA_TIMEOUT_GRE_REPLIED]) {
 313                 timeouts[GRE_CT_REPLIED] =
 314                         ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_REPLIED])) * HZ;
 315         }
 316         return 0;
 317 }
 318
 319 static int
 320 gre_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
 321 {
 322         const unsigned int *timeouts = data;
 323
 324         if (nla_put_be32(skb, CTA_TIMEOUT_GRE_UNREPLIED,
 325                          htonl(timeouts[GRE_CT_UNREPLIED] / HZ)) ||
 326             nla_put_be32(skb, CTA_TIMEOUT_GRE_REPLIED,
 327                          htonl(timeouts[GRE_CT_REPLIED] / HZ)))
 328                 goto nla_put_failure;
 329         return 0;
 330
 331 nla_put_failure:
 332         return -ENOSPC;
 333 }
 334
 335 static const struct nla_policy
 336 gre_timeout_nla_policy[CTA_TIMEOUT_GRE_MAX+1] = {
 337         [CTA_TIMEOUT_GRE_UNREPLIED]     = { .type = NLA_U32 },
 338         [CTA_TIMEOUT_GRE_REPLIED]       = { .type = NLA_U32 },
 339 };
 340 #endif /* CONFIG_NF_CT_NETLINK_TIMEOUT */
 341
 342 /* protocol helper struct */
 343 static struct nf_conntrack_l4proto nf_conntrack_l4proto_gre4 __read_mostly = {
 344         .l3proto         = AF_INET,
 345         .l4proto         = IPPROTO_GRE,
 346         .name            = "gre",
 347         .pkt_to_tuple    = gre_pkt_to_tuple,
 348         .invert_tuple    = gre_invert_tuple,
 349         .print_tuple     = gre_print_tuple,
 350         .print_conntrack = gre_print_conntrack,
 351         .get_timeouts    = gre_get_timeouts,
 352         .packet          = gre_packet,
 353         .new             = gre_new,
 354         .destroy         = gre_destroy,
 355         .me              = THIS_MODULE,
 356 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
 357         .tuple_to_nlattr = nf_ct_port_tuple_to_nlattr,
 358         .nlattr_tuple_size = nf_ct_port_nlattr_tuple_size,
 359         .nlattr_to_tuple = nf_ct_port_nlattr_to_tuple,
 360         .nla_policy      = nf_ct_port_nla_policy,
 361 #endif
 362 #if IS_ENABLED(CONFIG_NF_CT_NETLINK_TIMEOUT)
 363         .ctnl_timeout    = {
 364                 .nlattr_to_obj  = gre_timeout_nlattr_to_obj,
 365                 .obj_to_nlattr  = gre_timeout_obj_to_nlattr,
 366                 .nlattr_max     = CTA_TIMEOUT_GRE_MAX,
 367                 .obj_size       = sizeof(unsigned int) * GRE_CT_MAX,
 368                 .nla_policy     = gre_timeout_nla_policy,
 369         },
 370 #endif /* CONFIG_NF_CT_NETLINK_TIMEOUT */
 371 };
 372
 373 static int proto_gre_net_init(struct net *net)
 374 {
 375         struct netns_proto_gre *net_gre = net_generic(net, proto_gre_net_id);
 376
 377         rwlock_init(&net_gre->keymap_lock);
 378         INIT_LIST_HEAD(&net_gre->keymap_list);
 379
 380         return 0;
 381 }
 382
 383 static void proto_gre_net_exit(struct net *net)
 384 {
 385         nf_ct_gre_keymap_flush(net);
 386 }
 387
 388 static struct pernet_operations proto_gre_net_ops = {
 389         .init = proto_gre_net_init,
 390         .exit = proto_gre_net_exit,
 391         .id   = &proto_gre_net_id,
 392         .size = sizeof(struct netns_proto_gre),
 393 };
 394
 395 static int __init nf_ct_proto_gre_init(void)
 396 {
 397         int rv;
 398
 399         rv = nf_conntrack_l4proto_register(&nf_conntrack_l4proto_gre4);
 400         if (rv < 0)
 401                 return rv;
 402         rv = register_pernet_subsys(&proto_gre_net_ops);
 403         if (rv < 0)
 404                 nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_gre4);
 405         return rv;
 406 }
 407
 408 static void __exit nf_ct_proto_gre_fini(void)
 409 {
 410         nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_gre4);
 411         unregister_pernet_subsys(&proto_gre_net_ops);
 412 }
 413
 414 module_init(nf_ct_proto_gre_init);
 415 module_exit(nf_ct_proto_gre_fini);
 416
 417 MODULE_LICENSE("GPL");