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 * (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
  45enum grep_conntrack {
  46        GRE_CT_UNREPLIED,
  47        GRE_CT_REPLIED,
  48        GRE_CT_MAX
  49};
  50
  51static unsigned int gre_timeouts[GRE_CT_MAX] = {
  52        [GRE_CT_UNREPLIED]      = 30*HZ,
  53        [GRE_CT_REPLIED]        = 180*HZ,
  54};
  55
  56static int proto_gre_net_id __read_mostly;
  57struct 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
  64static inline struct netns_proto_gre *gre_pernet(struct net *net)
  65{
  66        return net_generic(net, proto_gre_net_id);
  67}
  68
  69void 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}
  81EXPORT_SYMBOL(nf_ct_gre_keymap_flush);
  82
  83static 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 */
  94static __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 */
 116int 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}
 155EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_add);
 156
 157/* destroy the keymap entries associated with specified master ct */
 158void 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}
 179EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_destroy);
 180
 181/* PUBLIC CONNTRACK PROTO HELPER FUNCTIONS */
 182
 183/* invert gre part of tuple */
 184static 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 */
 193static 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 */
 230static 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 */
 239static 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
 246static 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 */
 252static 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. */
 276static 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 */
 292static 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
 308static 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
 329static int
 330gre_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
 341nla_put_failure:
 342        return -ENOSPC;
 343}
 344
 345static const struct nla_policy
 346gre_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
 352static 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 */
 366static 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
 398static 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
 407static 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
 413static 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
 420static 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;
 433out_gre4:
 434        unregister_pernet_subsys(&proto_gre_net_ops);
 435out_pernet:
 436        return ret;
 437}
 438
 439static 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
 445module_init(nf_ct_proto_gre_init);
 446module_exit(nf_ct_proto_gre_fini);
 447
 448MODULE_LICENSE("GPL");
 449
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