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  * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
  25  */
  26
  27 #include <linux/module.h>
  28 #include <linux/types.h>
  29 #include <linux/timer.h>
  30 #include <linux/list.h>
  31 #include <linux/seq_file.h>
  32 #include <linux/in.h>
  33 #include <linux/netdevice.h>
  34 #include <linux/skbuff.h>
  35 #include <linux/slab.h>
  36 #include <net/dst.h>
  37 #include <net/net_namespace.h>
  38 #include <net/netns/generic.h>
  39 #include <net/netfilter/nf_conntrack_l4proto.h>
  40 #include <net/netfilter/nf_conntrack_helper.h>
  41 #include <net/netfilter/nf_conntrack_core.h>
  42 #include <linux/netfilter/nf_conntrack_proto_gre.h>
  43 #include <linux/netfilter/nf_conntrack_pptp.h>
  44
  45 enum grep_conntrack {
  46         GRE_CT_UNREPLIED,
  47         GRE_CT_REPLIED,
  48         GRE_CT_MAX
  49 };
  50
  51 static unsigned int gre_timeouts[GRE_CT_MAX] = {
  52         [GRE_CT_UNREPLIED]      = 30*HZ,
  53         [GRE_CT_REPLIED]        = 180*HZ,
  54 };
  55
  56 static unsigned int proto_gre_net_id __read_mostly;
  57 struct netns_proto_gre {
  58         struct nf_proto_net     nf;
  59         rwlock_t                keymap_lock;
  60         struct list_head        keymap_list;
  61         unsigned int            gre_timeouts[GRE_CT_MAX];
  62 };
  63
  64 static inline struct netns_proto_gre *gre_pernet(struct net *net)
  65 {
  66         return net_generic(net, proto_gre_net_id);
  67 }
  68
  69 static void nf_ct_gre_keymap_flush(struct net *net)
  70 {
  71         struct netns_proto_gre *net_gre = gre_pernet(net);
  72         struct nf_ct_gre_keymap *km, *tmp;
  73
  74         write_lock_bh(&net_gre->keymap_lock);
  75         list_for_each_entry_safe(km, tmp, &net_gre->keymap_list, list) {
  76                 list_del(&km->list);
  77                 kfree(km);
  78         }
  79         write_unlock_bh(&net_gre->keymap_lock);
  80 }
  81
  82 static inline int gre_key_cmpfn(const struct nf_ct_gre_keymap *km,
  83                                 const struct nf_conntrack_tuple *t)
  84 {
  85         return km->tuple.src.l3num == t->src.l3num &&
  86                !memcmp(&km->tuple.src.u3, &t->src.u3, sizeof(t->src.u3)) &&
  87                !memcmp(&km->tuple.dst.u3, &t->dst.u3, sizeof(t->dst.u3)) &&
  88                km->tuple.dst.protonum == t->dst.protonum &&
  89                km->tuple.dst.u.all == t->dst.u.all;
  90 }
  91
  92 /* look up the source key for a given tuple */
  93 static __be16 gre_keymap_lookup(struct net *net, struct nf_conntrack_tuple *t)
  94 {
  95         struct netns_proto_gre *net_gre = gre_pernet(net);
  96         struct nf_ct_gre_keymap *km;
  97         __be16 key = 0;
  98
  99         read_lock_bh(&net_gre->keymap_lock);
 100         list_for_each_entry(km, &net_gre->keymap_list, list) {
 101                 if (gre_key_cmpfn(km, t)) {
 102                         key = km->tuple.src.u.gre.key;
 103                         break;
 104                 }
 105         }
 106         read_unlock_bh(&net_gre->keymap_lock);
 107
 108         pr_debug("lookup src key 0x%x for ", key);
 109         nf_ct_dump_tuple(t);
 110
 111         return key;
 112 }
 113
 114 /* add a single keymap entry, associate with specified master ct */
 115 int nf_ct_gre_keymap_add(struct nf_conn *ct, enum ip_conntrack_dir dir,
 116                          struct nf_conntrack_tuple *t)
 117 {
 118         struct net *net = nf_ct_net(ct);
 119         struct netns_proto_gre *net_gre = gre_pernet(net);
 120         struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
 121         struct nf_ct_gre_keymap **kmp, *km;
 122
 123         kmp = &ct_pptp_info->keymap[dir];
 124         if (*kmp) {
 125                 /* check whether it's a retransmission */
 126                 read_lock_bh(&net_gre->keymap_lock);
 127                 list_for_each_entry(km, &net_gre->keymap_list, list) {
 128                         if (gre_key_cmpfn(km, t) && km == *kmp) {
 129                                 read_unlock_bh(&net_gre->keymap_lock);
 130                                 return 0;
 131                         }
 132                 }
 133                 read_unlock_bh(&net_gre->keymap_lock);
 134                 pr_debug("trying to override keymap_%s for ct %p\n",
 135                          dir == IP_CT_DIR_REPLY ? "reply" : "orig", ct);
 136                 return -EEXIST;
 137         }
 138
 139         km = kmalloc(sizeof(*km), GFP_ATOMIC);
 140         if (!km)
 141                 return -ENOMEM;
 142         memcpy(&km->tuple, t, sizeof(*t));
 143         *kmp = km;
 144
 145         pr_debug("adding new entry %p: ", km);
 146         nf_ct_dump_tuple(&km->tuple);
 147
 148         write_lock_bh(&net_gre->keymap_lock);
 149         list_add_tail(&km->list, &net_gre->keymap_list);
 150         write_unlock_bh(&net_gre->keymap_lock);
 151
 152         return 0;
 153 }
 154 EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_add);
 155
 156 /* destroy the keymap entries associated with specified master ct */
 157 void nf_ct_gre_keymap_destroy(struct nf_conn *ct)
 158 {
 159         struct net *net = nf_ct_net(ct);
 160         struct netns_proto_gre *net_gre = gre_pernet(net);
 161         struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
 162         enum ip_conntrack_dir dir;
 163
 164         pr_debug("entering for ct %p\n", ct);
 165
 166         write_lock_bh(&net_gre->keymap_lock);
 167         for (dir = IP_CT_DIR_ORIGINAL; dir < IP_CT_DIR_MAX; dir++) {
 168                 if (ct_pptp_info->keymap[dir]) {
 169                         pr_debug("removing %p from list\n",
 170                                  ct_pptp_info->keymap[dir]);
 171                         list_del(&ct_pptp_info->keymap[dir]->list);
 172                         kfree(ct_pptp_info->keymap[dir]);
 173                         ct_pptp_info->keymap[dir] = NULL;
 174                 }
 175         }
 176         write_unlock_bh(&net_gre->keymap_lock);
 177 }
 178 EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_destroy);
 179
 180 /* PUBLIC CONNTRACK PROTO HELPER FUNCTIONS */
 181
 182 /* invert gre part of tuple */
 183 static bool gre_invert_tuple(struct nf_conntrack_tuple *tuple,
 184                              const struct nf_conntrack_tuple *orig)
 185 {
 186         tuple->dst.u.gre.key = orig->src.u.gre.key;
 187         tuple->src.u.gre.key = orig->dst.u.gre.key;
 188         return true;
 189 }
 190
 191 /* gre hdr info to tuple */
 192 static bool gre_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff,
 193                              struct net *net, struct nf_conntrack_tuple *tuple)
 194 {
 195         const struct pptp_gre_header *pgrehdr;
 196         struct pptp_gre_header _pgrehdr;
 197         __be16 srckey;
 198         const struct gre_base_hdr *grehdr;
 199         struct gre_base_hdr _grehdr;
 200
 201         /* first only delinearize old RFC1701 GRE header */
 202         grehdr = skb_header_pointer(skb, dataoff, sizeof(_grehdr), &_grehdr);
 203         if (!grehdr || (grehdr->flags & GRE_VERSION) != GRE_VERSION_1) {
 204                 /* try to behave like "nf_conntrack_proto_generic" */
 205                 tuple->src.u.all = 0;
 206                 tuple->dst.u.all = 0;
 207                 return true;
 208         }
 209
 210         /* PPTP header is variable length, only need up to the call_id field */
 211         pgrehdr = skb_header_pointer(skb, dataoff, 8, &_pgrehdr);
 212         if (!pgrehdr)
 213                 return true;
 214
 215         if (grehdr->protocol != GRE_PROTO_PPP) {
 216                 pr_debug("Unsupported GRE proto(0x%x)\n", ntohs(grehdr->protocol));
 217                 return false;
 218         }
 219
 220         tuple->dst.u.gre.key = pgrehdr->call_id;
 221         srckey = gre_keymap_lookup(net, tuple);
 222         tuple->src.u.gre.key = srckey;
 223
 224         return true;
 225 }
 226
 227 /* print gre part of tuple */
 228 static void gre_print_tuple(struct seq_file *s,
 229                             const struct nf_conntrack_tuple *tuple)
 230 {
 231         seq_printf(s, "srckey=0x%x dstkey=0x%x ",
 232                    ntohs(tuple->src.u.gre.key),
 233                    ntohs(tuple->dst.u.gre.key));
 234 }
 235
 236 /* print private data for conntrack */
 237 static void gre_print_conntrack(struct seq_file *s, struct nf_conn *ct)
 238 {
 239         seq_printf(s, "timeout=%u, stream_timeout=%u ",
 240                    (ct->proto.gre.timeout / HZ),
 241                    (ct->proto.gre.stream_timeout / HZ));
 242 }
 243
 244 static unsigned int *gre_get_timeouts(struct net *net)
 245 {
 246         return gre_pernet(net)->gre_timeouts;
 247 }
 248
 249 /* Returns verdict for packet, and may modify conntrack */
 250 static int gre_packet(struct nf_conn *ct,
 251                       const struct sk_buff *skb,
 252                       unsigned int dataoff,
 253                       enum ip_conntrack_info ctinfo,
 254                       u_int8_t pf,
 255                       unsigned int hooknum,
 256                       unsigned int *timeouts)
 257 {
 258         /* If we've seen traffic both ways, this is a GRE connection.
 259          * Extend timeout. */
 260         if (ct->status & IPS_SEEN_REPLY) {
 261                 nf_ct_refresh_acct(ct, ctinfo, skb,
 262                                    ct->proto.gre.stream_timeout);
 263                 /* Also, more likely to be important, and not a probe. */
 264                 if (!test_and_set_bit(IPS_ASSURED_BIT, &ct->status))
 265                         nf_conntrack_event_cache(IPCT_ASSURED, ct);
 266         } else
 267                 nf_ct_refresh_acct(ct, ctinfo, skb,
 268                                    ct->proto.gre.timeout);
 269
 270         return NF_ACCEPT;
 271 }
 272
 273 /* Called when a new connection for this protocol found. */
 274 static bool gre_new(struct nf_conn *ct, const struct sk_buff *skb,
 275                     unsigned int dataoff, unsigned int *timeouts)
 276 {
 277         pr_debug(": ");
 278         nf_ct_dump_tuple(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
 279
 280         /* initialize to sane value.  Ideally a conntrack helper
 281          * (e.g. in case of pptp) is increasing them */
 282         ct->proto.gre.stream_timeout = timeouts[GRE_CT_REPLIED];
 283         ct->proto.gre.timeout = timeouts[GRE_CT_UNREPLIED];
 284
 285         return true;
 286 }
 287
 288 /* Called when a conntrack entry has already been removed from the hashes
 289  * and is about to be deleted from memory */
 290 static void gre_destroy(struct nf_conn *ct)
 291 {
 292         struct nf_conn *master = ct->master;
 293         pr_debug(" entering\n");
 294
 295         if (!master)
 296                 pr_debug("no master !?!\n");
 297         else
 298                 nf_ct_gre_keymap_destroy(master);
 299 }
 300
 301 #if IS_ENABLED(CONFIG_NF_CT_NETLINK_TIMEOUT)
 302
 303 #include <linux/netfilter/nfnetlink.h>
 304 #include <linux/netfilter/nfnetlink_cttimeout.h>
 305
 306 static int gre_timeout_nlattr_to_obj(struct nlattr *tb[],
 307                                      struct net *net, void *data)
 308 {
 309         unsigned int *timeouts = data;
 310         struct netns_proto_gre *net_gre = gre_pernet(net);
 311
 312         /* set default timeouts for GRE. */
 313         timeouts[GRE_CT_UNREPLIED] = net_gre->gre_timeouts[GRE_CT_UNREPLIED];
 314         timeouts[GRE_CT_REPLIED] = net_gre->gre_timeouts[GRE_CT_REPLIED];
 315
 316         if (tb[CTA_TIMEOUT_GRE_UNREPLIED]) {
 317                 timeouts[GRE_CT_UNREPLIED] =
 318                         ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_UNREPLIED])) * HZ;
 319         }
 320         if (tb[CTA_TIMEOUT_GRE_REPLIED]) {
 321                 timeouts[GRE_CT_REPLIED] =
 322                         ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_REPLIED])) * HZ;
 323         }
 324         return 0;
 325 }
 326
 327 static int
 328 gre_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
 329 {
 330         const unsigned int *timeouts = data;
 331
 332         if (nla_put_be32(skb, CTA_TIMEOUT_GRE_UNREPLIED,
 333                          htonl(timeouts[GRE_CT_UNREPLIED] / HZ)) ||
 334             nla_put_be32(skb, CTA_TIMEOUT_GRE_REPLIED,
 335                          htonl(timeouts[GRE_CT_REPLIED] / HZ)))
 336                 goto nla_put_failure;
 337         return 0;
 338
 339 nla_put_failure:
 340         return -ENOSPC;
 341 }
 342
 343 static const struct nla_policy
 344 gre_timeout_nla_policy[CTA_TIMEOUT_GRE_MAX+1] = {
 345         [CTA_TIMEOUT_GRE_UNREPLIED]     = { .type = NLA_U32 },
 346         [CTA_TIMEOUT_GRE_REPLIED]       = { .type = NLA_U32 },
 347 };
 348 #endif /* CONFIG_NF_CT_NETLINK_TIMEOUT */
 349
 350 static int gre_init_net(struct net *net, u_int16_t proto)
 351 {
 352         struct netns_proto_gre *net_gre = gre_pernet(net);
 353         int i;
 354
 355         rwlock_init(&net_gre->keymap_lock);
 356         INIT_LIST_HEAD(&net_gre->keymap_list);
 357         for (i = 0; i < GRE_CT_MAX; i++)
 358                 net_gre->gre_timeouts[i] = gre_timeouts[i];
 359
 360         return 0;
 361 }
 362
 363 /* protocol helper struct */
 364 static struct nf_conntrack_l4proto nf_conntrack_l4proto_gre4 __read_mostly = {
 365         .l3proto         = AF_INET,
 366         .l4proto         = IPPROTO_GRE,
 367         .name            = "gre",
 368         .pkt_to_tuple    = gre_pkt_to_tuple,
 369         .invert_tuple    = gre_invert_tuple,
 370         .print_tuple     = gre_print_tuple,
 371         .print_conntrack = gre_print_conntrack,
 372         .get_timeouts    = gre_get_timeouts,
 373         .packet          = gre_packet,
 374         .new             = gre_new,
 375         .destroy         = gre_destroy,
 376         .me              = THIS_MODULE,
 377 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
 378         .tuple_to_nlattr = nf_ct_port_tuple_to_nlattr,
 379         .nlattr_tuple_size = nf_ct_port_nlattr_tuple_size,
 380         .nlattr_to_tuple = nf_ct_port_nlattr_to_tuple,
 381         .nla_policy      = nf_ct_port_nla_policy,
 382 #endif
 383 #if IS_ENABLED(CONFIG_NF_CT_NETLINK_TIMEOUT)
 384         .ctnl_timeout    = {
 385                 .nlattr_to_obj  = gre_timeout_nlattr_to_obj,
 386                 .obj_to_nlattr  = gre_timeout_obj_to_nlattr,
 387                 .nlattr_max     = CTA_TIMEOUT_GRE_MAX,
 388                 .obj_size       = sizeof(unsigned int) * GRE_CT_MAX,
 389                 .nla_policy     = gre_timeout_nla_policy,
 390         },
 391 #endif /* CONFIG_NF_CT_NETLINK_TIMEOUT */
 392         .net_id         = &proto_gre_net_id,
 393         .init_net       = gre_init_net,
 394 };
 395
 396 static int proto_gre_net_init(struct net *net)
 397 {
 398         int ret = 0;
 399
 400         ret = nf_ct_l4proto_pernet_register_one(net,
 401                                                 &nf_conntrack_l4proto_gre4);
 402         if (ret < 0)
 403                 pr_err("nf_conntrack_gre4: pernet registration failed.\n");
 404         return ret;
 405 }
 406
 407 static void proto_gre_net_exit(struct net *net)
 408 {
 409         nf_ct_l4proto_pernet_unregister_one(net, &nf_conntrack_l4proto_gre4);
 410         nf_ct_gre_keymap_flush(net);
 411 }
 412
 413 static struct pernet_operations proto_gre_net_ops = {
 414         .init = proto_gre_net_init,
 415         .exit = proto_gre_net_exit,
 416         .id   = &proto_gre_net_id,
 417         .size = sizeof(struct netns_proto_gre),
 418 };
 419
 420 static int __init nf_ct_proto_gre_init(void)
 421 {
 422         int ret;
 423
 424         ret = register_pernet_subsys(&proto_gre_net_ops);
 425         if (ret < 0)
 426                 goto out_pernet;
 427         ret = nf_ct_l4proto_register_one(&nf_conntrack_l4proto_gre4);
 428         if (ret < 0)
 429                 goto out_gre4;
 430
 431         return 0;
 432 out_gre4:
 433         unregister_pernet_subsys(&proto_gre_net_ops);
 434 out_pernet:
 435         return ret;
 436 }
 437
 438 static void __exit nf_ct_proto_gre_fini(void)
 439 {
 440         nf_ct_l4proto_unregister_one(&nf_conntrack_l4proto_gre4);
 441         unregister_pernet_subsys(&proto_gre_net_ops);
 442 }
 443
 444 module_init(nf_ct_proto_gre_init);
 445 module_exit(nf_ct_proto_gre_fini);
 446
 447 MODULE_LICENSE("GPL");