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 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 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 EXPORT_SYMBOL(nf_ct_gre_keymap_flush);
  82
  83 static inline int gre_key_cmpfn(const struct nf_ct_gre_keymap *km,
  84                                 const struct nf_conntrack_tuple *t)
  85 {
  86         return km->tuple.src.l3num == t->src.l3num &&
  87                !memcmp(&km->tuple.src.u3, &t->src.u3, sizeof(t->src.u3)) &&
  88                !memcmp(&km->tuple.dst.u3, &t->dst.u3, sizeof(t->dst.u3)) &&
  89                km->tuple.dst.protonum == t->dst.protonum &&
  90                km->tuple.dst.u.all == t->dst.u.all;
  91 }
  92
  93 /* look up the source key for a given tuple */
  94 static __be16 gre_keymap_lookup(struct net *net, struct nf_conntrack_tuple *t)
  95 {
  96         struct netns_proto_gre *net_gre = gre_pernet(net);
  97         struct nf_ct_gre_keymap *km;
  98         __be16 key = 0;
  99
 100         read_lock_bh(&net_gre->keymap_lock);
 101         list_for_each_entry(km, &net_gre->keymap_list, list) {
 102                 if (gre_key_cmpfn(km, t)) {
 103                         key = km->tuple.src.u.gre.key;
 104                         break;
 105                 }
 106         }
 107         read_unlock_bh(&net_gre->keymap_lock);
 108
 109         pr_debug("lookup src key 0x%x for ", key);
 110         nf_ct_dump_tuple(t);
 111
 112         return key;
 113 }
 114
 115 /* add a single keymap entry, associate with specified master ct */
 116 int nf_ct_gre_keymap_add(struct nf_conn *ct, enum ip_conntrack_dir dir,
 117                          struct nf_conntrack_tuple *t)
 118 {
 119         struct net *net = nf_ct_net(ct);
 120         struct netns_proto_gre *net_gre = gre_pernet(net);
 121         struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
 122         struct nf_ct_gre_keymap **kmp, *km;
 123
 124         kmp = &ct_pptp_info->keymap[dir];
 125         if (*kmp) {
 126                 /* check whether it's a retransmission */
 127                 read_lock_bh(&net_gre->keymap_lock);
 128                 list_for_each_entry(km, &net_gre->keymap_list, list) {
 129                         if (gre_key_cmpfn(km, t) && km == *kmp) {
 130                                 read_unlock_bh(&net_gre->keymap_lock);
 131                                 return 0;
 132                         }
 133                 }
 134                 read_unlock_bh(&net_gre->keymap_lock);
 135                 pr_debug("trying to override keymap_%s for ct %p\n",
 136                          dir == IP_CT_DIR_REPLY ? "reply" : "orig", ct);
 137                 return -EEXIST;
 138         }
 139
 140         km = kmalloc(sizeof(*km), GFP_ATOMIC);
 141         if (!km)
 142                 return -ENOMEM;
 143         memcpy(&km->tuple, t, sizeof(*t));
 144         *kmp = km;
 145
 146         pr_debug("adding new entry %p: ", km);
 147         nf_ct_dump_tuple(&km->tuple);
 148
 149         write_lock_bh(&net_gre->keymap_lock);
 150         list_add_tail(&km->list, &net_gre->keymap_list);
 151         write_unlock_bh(&net_gre->keymap_lock);
 152
 153         return 0;
 154 }
 155 EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_add);
 156
 157 /* destroy the keymap entries associated with specified master ct */
 158 void nf_ct_gre_keymap_destroy(struct nf_conn *ct)
 159 {
 160         struct net *net = nf_ct_net(ct);
 161         struct netns_proto_gre *net_gre = gre_pernet(net);
 162         struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
 163         enum ip_conntrack_dir dir;
 164
 165         pr_debug("entering for ct %p\n", ct);
 166
 167         write_lock_bh(&net_gre->keymap_lock);
 168         for (dir = IP_CT_DIR_ORIGINAL; dir < IP_CT_DIR_MAX; dir++) {
 169                 if (ct_pptp_info->keymap[dir]) {
 170                         pr_debug("removing %p from list\n",
 171                                  ct_pptp_info->keymap[dir]);
 172                         list_del(&ct_pptp_info->keymap[dir]->list);
 173                         kfree(ct_pptp_info->keymap[dir]);
 174                         ct_pptp_info->keymap[dir] = NULL;
 175                 }
 176         }
 177         write_unlock_bh(&net_gre->keymap_lock);
 178 }
 179 EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_destroy);
 180
 181 /* PUBLIC CONNTRACK PROTO HELPER FUNCTIONS */
 182
 183 /* invert gre part of tuple */
 184 static bool gre_invert_tuple(struct nf_conntrack_tuple *tuple,
 185                              const struct nf_conntrack_tuple *orig)
 186 {
 187         tuple->dst.u.gre.key = orig->src.u.gre.key;
 188         tuple->src.u.gre.key = orig->dst.u.gre.key;
 189         return true;
 190 }
 191
 192 /* gre hdr info to tuple */
 193 static bool gre_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff,
 194                              struct nf_conntrack_tuple *tuple)
 195 {
 196         struct net *net = dev_net(skb->dev ? skb->dev : skb_dst(skb)->dev);
 197         const struct gre_hdr_pptp *pgrehdr;
 198         struct gre_hdr_pptp _pgrehdr;
 199         __be16 srckey;
 200         const struct gre_hdr *grehdr;
 201         struct gre_hdr _grehdr;
 202
 203         /* first only delinearize old RFC1701 GRE header */
 204         grehdr = skb_header_pointer(skb, dataoff, sizeof(_grehdr), &_grehdr);
 205         if (!grehdr || grehdr->version != GRE_VERSION_PPTP) {
 206                 /* try to behave like "nf_conntrack_proto_generic" */
 207                 tuple->src.u.all = 0;
 208                 tuple->dst.u.all = 0;
 209                 return true;
 210         }
 211
 212         /* PPTP header is variable length, only need up to the call_id field */
 213         pgrehdr = skb_header_pointer(skb, dataoff, 8, &_pgrehdr);
 214         if (!pgrehdr)
 215                 return true;
 216
 217         if (ntohs(grehdr->protocol) != GRE_PROTOCOL_PPTP) {
 218                 pr_debug("GRE_VERSION_PPTP but unknown proto\n");
 219                 return false;
 220         }
 221
 222         tuple->dst.u.gre.key = pgrehdr->call_id;
 223         srckey = gre_keymap_lookup(net, tuple);
 224         tuple->src.u.gre.key = srckey;
 225
 226         return true;
 227 }
 228
 229 /* print gre part of tuple */
 230 static int gre_print_tuple(struct seq_file *s,
 231                            const struct nf_conntrack_tuple *tuple)
 232 {
 233         return seq_printf(s, "srckey=0x%x dstkey=0x%x ",
 234                           ntohs(tuple->src.u.gre.key),
 235                           ntohs(tuple->dst.u.gre.key));
 236 }
 237
 238 /* print private data for conntrack */
 239 static int gre_print_conntrack(struct seq_file *s, struct nf_conn *ct)
 240 {
 241         return seq_printf(s, "timeout=%u, stream_timeout=%u ",
 242                           (ct->proto.gre.timeout / HZ),
 243                           (ct->proto.gre.stream_timeout / HZ));
 244 }
 245
 246 static unsigned int *gre_get_timeouts(struct net *net)
 247 {
 248         return gre_pernet(net)->gre_timeouts;
 249 }
 250
 251 /* Returns verdict for packet, and may modify conntrack */
 252 static int gre_packet(struct nf_conn *ct,
 253                       const struct sk_buff *skb,
 254                       unsigned int dataoff,
 255                       enum ip_conntrack_info ctinfo,
 256                       u_int8_t pf,
 257                       unsigned int hooknum,
 258                       unsigned int *timeouts)
 259 {
 260         /* If we've seen traffic both ways, this is a GRE connection.
 261          * Extend timeout. */
 262         if (ct->status & IPS_SEEN_REPLY) {
 263                 nf_ct_refresh_acct(ct, ctinfo, skb,
 264                                    ct->proto.gre.stream_timeout);
 265                 /* Also, more likely to be important, and not a probe. */
 266                 if (!test_and_set_bit(IPS_ASSURED_BIT, &ct->status))
 267                         nf_conntrack_event_cache(IPCT_ASSURED, ct);
 268         } else
 269                 nf_ct_refresh_acct(ct, ctinfo, skb,
 270                                    ct->proto.gre.timeout);
 271
 272         return NF_ACCEPT;
 273 }
 274
 275 /* Called when a new connection for this protocol found. */
 276 static bool gre_new(struct nf_conn *ct, const struct sk_buff *skb,
 277                     unsigned int dataoff, unsigned int *timeouts)
 278 {
 279         pr_debug(": ");
 280         nf_ct_dump_tuple(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
 281
 282         /* initialize to sane value.  Ideally a conntrack helper
 283          * (e.g. in case of pptp) is increasing them */
 284         ct->proto.gre.stream_timeout = timeouts[GRE_CT_REPLIED];
 285         ct->proto.gre.timeout = timeouts[GRE_CT_UNREPLIED];
 286
 287         return true;
 288 }
 289
 290 /* Called when a conntrack entry has already been removed from the hashes
 291  * and is about to be deleted from memory */
 292 static void gre_destroy(struct nf_conn *ct)
 293 {
 294         struct nf_conn *master = ct->master;
 295         pr_debug(" entering\n");
 296
 297         if (!master)
 298                 pr_debug("no master !?!\n");
 299         else
 300                 nf_ct_gre_keymap_destroy(master);
 301 }
 302
 303 #if IS_ENABLED(CONFIG_NF_CT_NETLINK_TIMEOUT)
 304
 305 #include <linux/netfilter/nfnetlink.h>
 306 #include <linux/netfilter/nfnetlink_cttimeout.h>
 307
 308 static int gre_timeout_nlattr_to_obj(struct nlattr *tb[],
 309                                      struct net *net, void *data)
 310 {
 311         unsigned int *timeouts = data;
 312         struct netns_proto_gre *net_gre = gre_pernet(net);
 313
 314         /* set default timeouts for GRE. */
 315         timeouts[GRE_CT_UNREPLIED] = net_gre->gre_timeouts[GRE_CT_UNREPLIED];
 316         timeouts[GRE_CT_REPLIED] = net_gre->gre_timeouts[GRE_CT_REPLIED];
 317
 318         if (tb[CTA_TIMEOUT_GRE_UNREPLIED]) {
 319                 timeouts[GRE_CT_UNREPLIED] =
 320                         ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_UNREPLIED])) * HZ;
 321         }
 322         if (tb[CTA_TIMEOUT_GRE_REPLIED]) {
 323                 timeouts[GRE_CT_REPLIED] =
 324                         ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_REPLIED])) * HZ;
 325         }
 326         return 0;
 327 }
 328
 329 static int
 330 gre_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
 331 {
 332         const unsigned int *timeouts = data;
 333
 334         if (nla_put_be32(skb, CTA_TIMEOUT_GRE_UNREPLIED,
 335                          htonl(timeouts[GRE_CT_UNREPLIED] / HZ)) ||
 336             nla_put_be32(skb, CTA_TIMEOUT_GRE_REPLIED,
 337                          htonl(timeouts[GRE_CT_REPLIED] / HZ)))
 338                 goto nla_put_failure;
 339         return 0;
 340
 341 nla_put_failure:
 342         return -ENOSPC;
 343 }
 344
 345 static const struct nla_policy
 346 gre_timeout_nla_policy[CTA_TIMEOUT_GRE_MAX+1] = {
 347         [CTA_TIMEOUT_GRE_UNREPLIED]     = { .type = NLA_U32 },
 348         [CTA_TIMEOUT_GRE_REPLIED]       = { .type = NLA_U32 },
 349 };
 350 #endif /* CONFIG_NF_CT_NETLINK_TIMEOUT */
 351
 352 static int gre_init_net(struct net *net, u_int16_t proto)
 353 {
 354         struct netns_proto_gre *net_gre = gre_pernet(net);
 355         int i;
 356
 357         rwlock_init(&net_gre->keymap_lock);
 358         INIT_LIST_HEAD(&net_gre->keymap_list);
 359         for (i = 0; i < GRE_CT_MAX; i++)
 360                 net_gre->gre_timeouts[i] = gre_timeouts[i];
 361
 362         return 0;
 363 }
 364
 365 /* protocol helper struct */
 366 static struct nf_conntrack_l4proto nf_conntrack_l4proto_gre4 __read_mostly = {
 367         .l3proto         = AF_INET,
 368         .l4proto         = IPPROTO_GRE,
 369         .name            = "gre",
 370         .pkt_to_tuple    = gre_pkt_to_tuple,
 371         .invert_tuple    = gre_invert_tuple,
 372         .print_tuple     = gre_print_tuple,
 373         .print_conntrack = gre_print_conntrack,
 374         .get_timeouts    = gre_get_timeouts,
 375         .packet          = gre_packet,
 376         .new             = gre_new,
 377         .destroy         = gre_destroy,
 378         .me              = THIS_MODULE,
 379 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
 380         .tuple_to_nlattr = nf_ct_port_tuple_to_nlattr,
 381         .nlattr_tuple_size = nf_ct_port_nlattr_tuple_size,
 382         .nlattr_to_tuple = nf_ct_port_nlattr_to_tuple,
 383         .nla_policy      = nf_ct_port_nla_policy,
 384 #endif
 385 #if IS_ENABLED(CONFIG_NF_CT_NETLINK_TIMEOUT)
 386         .ctnl_timeout    = {
 387                 .nlattr_to_obj  = gre_timeout_nlattr_to_obj,
 388                 .obj_to_nlattr  = gre_timeout_obj_to_nlattr,
 389                 .nlattr_max     = CTA_TIMEOUT_GRE_MAX,
 390                 .obj_size       = sizeof(unsigned int) * GRE_CT_MAX,
 391                 .nla_policy     = gre_timeout_nla_policy,
 392         },
 393 #endif /* CONFIG_NF_CT_NETLINK_TIMEOUT */
 394         .net_id         = &proto_gre_net_id,
 395         .init_net       = gre_init_net,
 396 };
 397
 398 static int proto_gre_net_init(struct net *net)
 399 {
 400         int ret = 0;
 401         ret = nf_ct_l4proto_pernet_register(net, &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(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
 428         ret = nf_ct_l4proto_register(&nf_conntrack_l4proto_gre4);
 429         if (ret < 0)
 430                 goto out_gre4;
 431
 432         return 0;
 433 out_gre4:
 434         unregister_pernet_subsys(&proto_gre_net_ops);
 435 out_pernet:
 436         return ret;
 437 }
 438
 439 static void __exit nf_ct_proto_gre_fini(void)
 440 {
 441         nf_ct_l4proto_unregister(&nf_conntrack_l4proto_gre4);
 442         unregister_pernet_subsys(&proto_gre_net_ops);
 443 }
 444
 445 module_init(nf_ct_proto_gre_init);
 446 module_exit(nf_ct_proto_gre_fini);
 447
 448 MODULE_LICENSE("GPL");