linux/net/netfilter/nf_conntrack_proto_gre.c
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   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
  44enum grep_conntrack {
  45        GRE_CT_UNREPLIED,
  46        GRE_CT_REPLIED,
  47        GRE_CT_MAX
  48};
  49
  50static unsigned int gre_timeouts[GRE_CT_MAX] = {
  51        [GRE_CT_UNREPLIED]      = 30*HZ,
  52        [GRE_CT_REPLIED]        = 180*HZ,
  53};
  54
  55static int proto_gre_net_id __read_mostly;
  56struct netns_proto_gre {
  57        struct nf_proto_net     nf;
  58        rwlock_t                keymap_lock;
  59        struct list_head        keymap_list;
  60        unsigned int            gre_timeouts[GRE_CT_MAX];
  61};
  62
  63static inline struct netns_proto_gre *gre_pernet(struct net *net)
  64{
  65        return net_generic(net, proto_gre_net_id);
  66}
  67
  68void nf_ct_gre_keymap_flush(struct net *net)
  69{
  70        struct netns_proto_gre *net_gre = gre_pernet(net);
  71        struct nf_ct_gre_keymap *km, *tmp;
  72
  73        write_lock_bh(&net_gre->keymap_lock);
  74        list_for_each_entry_safe(km, tmp, &net_gre->keymap_list, list) {
  75                list_del(&km->list);
  76                kfree(km);
  77        }
  78        write_unlock_bh(&net_gre->keymap_lock);
  79}
  80EXPORT_SYMBOL(nf_ct_gre_keymap_flush);
  81
  82static 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 */
  93static __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 */
 115int 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}
 154EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_add);
 155
 156/* destroy the keymap entries associated with specified master ct */
 157void 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}
 178EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_destroy);
 179
 180/* PUBLIC CONNTRACK PROTO HELPER FUNCTIONS */
 181
 182/* invert gre part of tuple */
 183static 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 */
 192static bool gre_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff,
 193                             struct nf_conntrack_tuple *tuple)
 194{
 195        struct net *net = dev_net(skb->dev ? skb->dev : skb_dst(skb)->dev);
 196        const struct gre_hdr_pptp *pgrehdr;
 197        struct gre_hdr_pptp _pgrehdr;
 198        __be16 srckey;
 199        const struct gre_hdr *grehdr;
 200        struct gre_hdr _grehdr;
 201
 202        /* first only delinearize old RFC1701 GRE header */
 203        grehdr = skb_header_pointer(skb, dataoff, sizeof(_grehdr), &_grehdr);
 204        if (!grehdr || grehdr->version != GRE_VERSION_PPTP) {
 205                /* try to behave like "nf_conntrack_proto_generic" */
 206                tuple->src.u.all = 0;
 207                tuple->dst.u.all = 0;
 208                return true;
 209        }
 210
 211        /* PPTP header is variable length, only need up to the call_id field */
 212        pgrehdr = skb_header_pointer(skb, dataoff, 8, &_pgrehdr);
 213        if (!pgrehdr)
 214                return true;
 215
 216        if (ntohs(grehdr->protocol) != GRE_PROTOCOL_PPTP) {
 217                pr_debug("GRE_VERSION_PPTP but unknown proto\n");
 218                return false;
 219        }
 220
 221        tuple->dst.u.gre.key = pgrehdr->call_id;
 222        srckey = gre_keymap_lookup(net, tuple);
 223        tuple->src.u.gre.key = srckey;
 224
 225        return true;
 226}
 227
 228/* print gre part of tuple */
 229static int gre_print_tuple(struct seq_file *s,
 230                           const struct nf_conntrack_tuple *tuple)
 231{
 232        return seq_printf(s, "srckey=0x%x dstkey=0x%x ",
 233                          ntohs(tuple->src.u.gre.key),
 234                          ntohs(tuple->dst.u.gre.key));
 235}
 236
 237/* print private data for conntrack */
 238static int gre_print_conntrack(struct seq_file *s, struct nf_conn *ct)
 239{
 240        return seq_printf(s, "timeout=%u, stream_timeout=%u ",
 241                          (ct->proto.gre.timeout / HZ),
 242                          (ct->proto.gre.stream_timeout / HZ));
 243}
 244
 245static unsigned int *gre_get_timeouts(struct net *net)
 246{
 247        return gre_pernet(net)->gre_timeouts;
 248}
 249
 250/* Returns verdict for packet, and may modify conntrack */
 251static int gre_packet(struct nf_conn *ct,
 252                      const struct sk_buff *skb,
 253                      unsigned int dataoff,
 254                      enum ip_conntrack_info ctinfo,
 255                      u_int8_t pf,
 256                      unsigned int hooknum,
 257                      unsigned int *timeouts)
 258{
 259        /* If we've seen traffic both ways, this is a GRE connection.
 260         * Extend timeout. */
 261        if (ct->status & IPS_SEEN_REPLY) {
 262                nf_ct_refresh_acct(ct, ctinfo, skb,
 263                                   ct->proto.gre.stream_timeout);
 264                /* Also, more likely to be important, and not a probe. */
 265                if (!test_and_set_bit(IPS_ASSURED_BIT, &ct->status))
 266                        nf_conntrack_event_cache(IPCT_ASSURED, ct);
 267        } else
 268                nf_ct_refresh_acct(ct, ctinfo, skb,
 269                                   ct->proto.gre.timeout);
 270
 271        return NF_ACCEPT;
 272}
 273
 274/* Called when a new connection for this protocol found. */
 275static bool gre_new(struct nf_conn *ct, const struct sk_buff *skb,
 276                    unsigned int dataoff, unsigned int *timeouts)
 277{
 278        pr_debug(": ");
 279        nf_ct_dump_tuple(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
 280
 281        /* initialize to sane value.  Ideally a conntrack helper
 282         * (e.g. in case of pptp) is increasing them */
 283        ct->proto.gre.stream_timeout = timeouts[GRE_CT_REPLIED];
 284        ct->proto.gre.timeout = timeouts[GRE_CT_UNREPLIED];
 285
 286        return true;
 287}
 288
 289/* Called when a conntrack entry has already been removed from the hashes
 290 * and is about to be deleted from memory */
 291static void gre_destroy(struct nf_conn *ct)
 292{
 293        struct nf_conn *master = ct->master;
 294        pr_debug(" entering\n");
 295
 296        if (!master)
 297                pr_debug("no master !?!\n");
 298        else
 299                nf_ct_gre_keymap_destroy(master);
 300}
 301
 302#if IS_ENABLED(CONFIG_NF_CT_NETLINK_TIMEOUT)
 303
 304#include <linux/netfilter/nfnetlink.h>
 305#include <linux/netfilter/nfnetlink_cttimeout.h>
 306
 307static int gre_timeout_nlattr_to_obj(struct nlattr *tb[],
 308                                     struct net *net, void *data)
 309{
 310        unsigned int *timeouts = data;
 311        struct netns_proto_gre *net_gre = gre_pernet(net);
 312
 313        /* set default timeouts for GRE. */
 314        timeouts[GRE_CT_UNREPLIED] = net_gre->gre_timeouts[GRE_CT_UNREPLIED];
 315        timeouts[GRE_CT_REPLIED] = net_gre->gre_timeouts[GRE_CT_REPLIED];
 316
 317        if (tb[CTA_TIMEOUT_GRE_UNREPLIED]) {
 318                timeouts[GRE_CT_UNREPLIED] =
 319                        ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_UNREPLIED])) * HZ;
 320        }
 321        if (tb[CTA_TIMEOUT_GRE_REPLIED]) {
 322                timeouts[GRE_CT_REPLIED] =
 323                        ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_REPLIED])) * HZ;
 324        }
 325        return 0;
 326}
 327
 328static int
 329gre_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
 330{
 331        const unsigned int *timeouts = data;
 332
 333        if (nla_put_be32(skb, CTA_TIMEOUT_GRE_UNREPLIED,
 334                         htonl(timeouts[GRE_CT_UNREPLIED] / HZ)) ||
 335            nla_put_be32(skb, CTA_TIMEOUT_GRE_REPLIED,
 336                         htonl(timeouts[GRE_CT_REPLIED] / HZ)))
 337                goto nla_put_failure;
 338        return 0;
 339
 340nla_put_failure:
 341        return -ENOSPC;
 342}
 343
 344static const struct nla_policy
 345gre_timeout_nla_policy[CTA_TIMEOUT_GRE_MAX+1] = {
 346        [CTA_TIMEOUT_GRE_UNREPLIED]     = { .type = NLA_U32 },
 347        [CTA_TIMEOUT_GRE_REPLIED]       = { .type = NLA_U32 },
 348};
 349#endif /* CONFIG_NF_CT_NETLINK_TIMEOUT */
 350
 351static int gre_init_net(struct net *net, u_int16_t proto)
 352{
 353        struct netns_proto_gre *net_gre = gre_pernet(net);
 354        int i;
 355
 356        rwlock_init(&net_gre->keymap_lock);
 357        INIT_LIST_HEAD(&net_gre->keymap_list);
 358        for (i = 0; i < GRE_CT_MAX; i++)
 359                net_gre->gre_timeouts[i] = gre_timeouts[i];
 360
 361        return 0;
 362}
 363
 364/* protocol helper struct */
 365static struct nf_conntrack_l4proto nf_conntrack_l4proto_gre4 __read_mostly = {
 366        .l3proto         = AF_INET,
 367        .l4proto         = IPPROTO_GRE,
 368        .name            = "gre",
 369        .pkt_to_tuple    = gre_pkt_to_tuple,
 370        .invert_tuple    = gre_invert_tuple,
 371        .print_tuple     = gre_print_tuple,
 372        .print_conntrack = gre_print_conntrack,
 373        .get_timeouts    = gre_get_timeouts,
 374        .packet          = gre_packet,
 375        .new             = gre_new,
 376        .destroy         = gre_destroy,
 377        .me              = THIS_MODULE,
 378#if IS_ENABLED(CONFIG_NF_CT_NETLINK)
 379        .tuple_to_nlattr = nf_ct_port_tuple_to_nlattr,
 380        .nlattr_tuple_size = nf_ct_port_nlattr_tuple_size,
 381        .nlattr_to_tuple = nf_ct_port_nlattr_to_tuple,
 382        .nla_policy      = nf_ct_port_nla_policy,
 383#endif
 384#if IS_ENABLED(CONFIG_NF_CT_NETLINK_TIMEOUT)
 385        .ctnl_timeout    = {
 386                .nlattr_to_obj  = gre_timeout_nlattr_to_obj,
 387                .obj_to_nlattr  = gre_timeout_obj_to_nlattr,
 388                .nlattr_max     = CTA_TIMEOUT_GRE_MAX,
 389                .obj_size       = sizeof(unsigned int) * GRE_CT_MAX,
 390                .nla_policy     = gre_timeout_nla_policy,
 391        },
 392#endif /* CONFIG_NF_CT_NETLINK_TIMEOUT */
 393        .net_id         = &proto_gre_net_id,
 394        .init_net       = gre_init_net,
 395};
 396
 397static int proto_gre_net_init(struct net *net)
 398{
 399        int ret = 0;
 400        ret = nf_conntrack_l4proto_register(net, &nf_conntrack_l4proto_gre4);
 401        if (ret < 0)
 402                pr_err("nf_conntrack_l4proto_gre4 :protocol register failed.\n");
 403        return ret;
 404}
 405
 406static void proto_gre_net_exit(struct net *net)
 407{
 408        nf_conntrack_l4proto_unregister(net, &nf_conntrack_l4proto_gre4);
 409        nf_ct_gre_keymap_flush(net);
 410}
 411
 412static struct pernet_operations proto_gre_net_ops = {
 413        .init = proto_gre_net_init,
 414        .exit = proto_gre_net_exit,
 415        .id   = &proto_gre_net_id,
 416        .size = sizeof(struct netns_proto_gre),
 417};
 418
 419static int __init nf_ct_proto_gre_init(void)
 420{
 421        return register_pernet_subsys(&proto_gre_net_ops);
 422}
 423
 424static void __exit nf_ct_proto_gre_fini(void)
 425{
 426        unregister_pernet_subsys(&proto_gre_net_ops);
 427}
 428
 429module_init(nf_ct_proto_gre_init);
 430module_exit(nf_ct_proto_gre_fini);
 431
 432MODULE_LICENSE("GPL");
 433
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