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 <net/dst.h>
  35#include <net/net_namespace.h>
  36#include <net/netns/generic.h>
  37#include <net/netfilter/nf_conntrack_l4proto.h>
  38#include <net/netfilter/nf_conntrack_helper.h>
  39#include <net/netfilter/nf_conntrack_core.h>
  40#include <linux/netfilter/nf_conntrack_proto_gre.h>
  41#include <linux/netfilter/nf_conntrack_pptp.h>
  42
  43#define GRE_TIMEOUT             (30 * HZ)
  44#define GRE_STREAM_TIMEOUT      (180 * HZ)
  45
  46static int proto_gre_net_id;
  47struct netns_proto_gre {
  48        rwlock_t                keymap_lock;
  49        struct list_head        keymap_list;
  50};
  51
  52void nf_ct_gre_keymap_flush(struct net *net)
  53{
  54        struct netns_proto_gre *net_gre = net_generic(net, proto_gre_net_id);
  55        struct nf_ct_gre_keymap *km, *tmp;
  56
  57        write_lock_bh(&net_gre->keymap_lock);
  58        list_for_each_entry_safe(km, tmp, &net_gre->keymap_list, list) {
  59                list_del(&km->list);
  60                kfree(km);
  61        }
  62        write_unlock_bh(&net_gre->keymap_lock);
  63}
  64EXPORT_SYMBOL(nf_ct_gre_keymap_flush);
  65
  66static inline int gre_key_cmpfn(const struct nf_ct_gre_keymap *km,
  67                                const struct nf_conntrack_tuple *t)
  68{
  69        return km->tuple.src.l3num == t->src.l3num &&
  70               !memcmp(&km->tuple.src.u3, &t->src.u3, sizeof(t->src.u3)) &&
  71               !memcmp(&km->tuple.dst.u3, &t->dst.u3, sizeof(t->dst.u3)) &&
  72               km->tuple.dst.protonum == t->dst.protonum &&
  73               km->tuple.dst.u.all == t->dst.u.all;
  74}
  75
  76/* look up the source key for a given tuple */
  77static __be16 gre_keymap_lookup(struct net *net, struct nf_conntrack_tuple *t)
  78{
  79        struct netns_proto_gre *net_gre = net_generic(net, proto_gre_net_id);
  80        struct nf_ct_gre_keymap *km;
  81        __be16 key = 0;
  82
  83        read_lock_bh(&net_gre->keymap_lock);
  84        list_for_each_entry(km, &net_gre->keymap_list, list) {
  85                if (gre_key_cmpfn(km, t)) {
  86                        key = km->tuple.src.u.gre.key;
  87                        break;
  88                }
  89        }
  90        read_unlock_bh(&net_gre->keymap_lock);
  91
  92        pr_debug("lookup src key 0x%x for ", key);
  93        nf_ct_dump_tuple(t);
  94
  95        return key;
  96}
  97
  98/* add a single keymap entry, associate with specified master ct */
  99int nf_ct_gre_keymap_add(struct nf_conn *ct, enum ip_conntrack_dir dir,
 100                         struct nf_conntrack_tuple *t)
 101{
 102        struct net *net = nf_ct_net(ct);
 103        struct netns_proto_gre *net_gre = net_generic(net, proto_gre_net_id);
 104        struct nf_conn_help *help = nfct_help(ct);
 105        struct nf_ct_gre_keymap **kmp, *km;
 106
 107        kmp = &help->help.ct_pptp_info.keymap[dir];
 108        if (*kmp) {
 109                /* check whether it's a retransmission */
 110                read_lock_bh(&net_gre->keymap_lock);
 111                list_for_each_entry(km, &net_gre->keymap_list, list) {
 112                        if (gre_key_cmpfn(km, t) && km == *kmp) {
 113                                read_unlock_bh(&net_gre->keymap_lock);
 114                                return 0;
 115                        }
 116                }
 117                read_unlock_bh(&net_gre->keymap_lock);
 118                pr_debug("trying to override keymap_%s for ct %p\n",
 119                         dir == IP_CT_DIR_REPLY ? "reply" : "orig", ct);
 120                return -EEXIST;
 121        }
 122
 123        km = kmalloc(sizeof(*km), GFP_ATOMIC);
 124        if (!km)
 125                return -ENOMEM;
 126        memcpy(&km->tuple, t, sizeof(*t));
 127        *kmp = km;
 128
 129        pr_debug("adding new entry %p: ", km);
 130        nf_ct_dump_tuple(&km->tuple);
 131
 132        write_lock_bh(&net_gre->keymap_lock);
 133        list_add_tail(&km->list, &net_gre->keymap_list);
 134        write_unlock_bh(&net_gre->keymap_lock);
 135
 136        return 0;
 137}
 138EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_add);
 139
 140/* destroy the keymap entries associated with specified master ct */
 141void nf_ct_gre_keymap_destroy(struct nf_conn *ct)
 142{
 143        struct net *net = nf_ct_net(ct);
 144        struct netns_proto_gre *net_gre = net_generic(net, proto_gre_net_id);
 145        struct nf_conn_help *help = nfct_help(ct);
 146        enum ip_conntrack_dir dir;
 147
 148        pr_debug("entering for ct %p\n", ct);
 149
 150        write_lock_bh(&net_gre->keymap_lock);
 151        for (dir = IP_CT_DIR_ORIGINAL; dir < IP_CT_DIR_MAX; dir++) {
 152                if (help->help.ct_pptp_info.keymap[dir]) {
 153                        pr_debug("removing %p from list\n",
 154                                 help->help.ct_pptp_info.keymap[dir]);
 155                        list_del(&help->help.ct_pptp_info.keymap[dir]->list);
 156                        kfree(help->help.ct_pptp_info.keymap[dir]);
 157                        help->help.ct_pptp_info.keymap[dir] = NULL;
 158                }
 159        }
 160        write_unlock_bh(&net_gre->keymap_lock);
 161}
 162EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_destroy);
 163
 164/* PUBLIC CONNTRACK PROTO HELPER FUNCTIONS */
 165
 166/* invert gre part of tuple */
 167static bool gre_invert_tuple(struct nf_conntrack_tuple *tuple,
 168                             const struct nf_conntrack_tuple *orig)
 169{
 170        tuple->dst.u.gre.key = orig->src.u.gre.key;
 171        tuple->src.u.gre.key = orig->dst.u.gre.key;
 172        return true;
 173}
 174
 175/* gre hdr info to tuple */
 176static bool gre_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff,
 177                             struct nf_conntrack_tuple *tuple)
 178{
 179        struct net *net = dev_net(skb->dev ? skb->dev : skb->dst->dev);
 180        const struct gre_hdr_pptp *pgrehdr;
 181        struct gre_hdr_pptp _pgrehdr;
 182        __be16 srckey;
 183        const struct gre_hdr *grehdr;
 184        struct gre_hdr _grehdr;
 185
 186        /* first only delinearize old RFC1701 GRE header */
 187        grehdr = skb_header_pointer(skb, dataoff, sizeof(_grehdr), &_grehdr);
 188        if (!grehdr || grehdr->version != GRE_VERSION_PPTP) {
 189                /* try to behave like "nf_conntrack_proto_generic" */
 190                tuple->src.u.all = 0;
 191                tuple->dst.u.all = 0;
 192                return true;
 193        }
 194
 195        /* PPTP header is variable length, only need up to the call_id field */
 196        pgrehdr = skb_header_pointer(skb, dataoff, 8, &_pgrehdr);
 197        if (!pgrehdr)
 198                return true;
 199
 200        if (ntohs(grehdr->protocol) != GRE_PROTOCOL_PPTP) {
 201                pr_debug("GRE_VERSION_PPTP but unknown proto\n");
 202                return false;
 203        }
 204
 205        tuple->dst.u.gre.key = pgrehdr->call_id;
 206        srckey = gre_keymap_lookup(net, tuple);
 207        tuple->src.u.gre.key = srckey;
 208
 209        return true;
 210}
 211
 212/* print gre part of tuple */
 213static int gre_print_tuple(struct seq_file *s,
 214                           const struct nf_conntrack_tuple *tuple)
 215{
 216        return seq_printf(s, "srckey=0x%x dstkey=0x%x ",
 217                          ntohs(tuple->src.u.gre.key),
 218                          ntohs(tuple->dst.u.gre.key));
 219}
 220
 221/* print private data for conntrack */
 222static int gre_print_conntrack(struct seq_file *s,
 223                               const struct nf_conn *ct)
 224{
 225        return seq_printf(s, "timeout=%u, stream_timeout=%u ",
 226                          (ct->proto.gre.timeout / HZ),
 227                          (ct->proto.gre.stream_timeout / HZ));
 228}
 229
 230/* Returns verdict for packet, and may modify conntrack */
 231static int gre_packet(struct nf_conn *ct,
 232                      const struct sk_buff *skb,
 233                      unsigned int dataoff,
 234                      enum ip_conntrack_info ctinfo,
 235                      u_int8_t pf,
 236                      unsigned int hooknum)
 237{
 238        /* If we've seen traffic both ways, this is a GRE connection.
 239         * Extend timeout. */
 240        if (ct->status & IPS_SEEN_REPLY) {
 241                nf_ct_refresh_acct(ct, ctinfo, skb,
 242                                   ct->proto.gre.stream_timeout);
 243                /* Also, more likely to be important, and not a probe. */
 244                set_bit(IPS_ASSURED_BIT, &ct->status);
 245                nf_conntrack_event_cache(IPCT_STATUS, ct);
 246        } else
 247                nf_ct_refresh_acct(ct, ctinfo, skb,
 248                                   ct->proto.gre.timeout);
 249
 250        return NF_ACCEPT;
 251}
 252
 253/* Called when a new connection for this protocol found. */
 254static bool gre_new(struct nf_conn *ct, const struct sk_buff *skb,
 255                    unsigned int dataoff)
 256{
 257        pr_debug(": ");
 258        nf_ct_dump_tuple(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
 259
 260        /* initialize to sane value.  Ideally a conntrack helper
 261         * (e.g. in case of pptp) is increasing them */
 262        ct->proto.gre.stream_timeout = GRE_STREAM_TIMEOUT;
 263        ct->proto.gre.timeout = GRE_TIMEOUT;
 264
 265        return true;
 266}
 267
 268/* Called when a conntrack entry has already been removed from the hashes
 269 * and is about to be deleted from memory */
 270static void gre_destroy(struct nf_conn *ct)
 271{
 272        struct nf_conn *master = ct->master;
 273        pr_debug(" entering\n");
 274
 275        if (!master)
 276                pr_debug("no master !?!\n");
 277        else
 278                nf_ct_gre_keymap_destroy(master);
 279}
 280
 281/* protocol helper struct */
 282static struct nf_conntrack_l4proto nf_conntrack_l4proto_gre4 __read_mostly = {
 283        .l3proto         = AF_INET,
 284        .l4proto         = IPPROTO_GRE,
 285        .name            = "gre",
 286        .pkt_to_tuple    = gre_pkt_to_tuple,
 287        .invert_tuple    = gre_invert_tuple,
 288        .print_tuple     = gre_print_tuple,
 289        .print_conntrack = gre_print_conntrack,
 290        .packet          = gre_packet,
 291        .new             = gre_new,
 292        .destroy         = gre_destroy,
 293        .me              = THIS_MODULE,
 294#if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
 295        .tuple_to_nlattr = nf_ct_port_tuple_to_nlattr,
 296        .nlattr_tuple_size = nf_ct_port_nlattr_tuple_size,
 297        .nlattr_to_tuple = nf_ct_port_nlattr_to_tuple,
 298        .nla_policy      = nf_ct_port_nla_policy,
 299#endif
 300};
 301
 302static int proto_gre_net_init(struct net *net)
 303{
 304        struct netns_proto_gre *net_gre;
 305        int rv;
 306
 307        net_gre = kmalloc(sizeof(struct netns_proto_gre), GFP_KERNEL);
 308        if (!net_gre)
 309                return -ENOMEM;
 310        rwlock_init(&net_gre->keymap_lock);
 311        INIT_LIST_HEAD(&net_gre->keymap_list);
 312
 313        rv = net_assign_generic(net, proto_gre_net_id, net_gre);
 314        if (rv < 0)
 315                kfree(net_gre);
 316        return rv;
 317}
 318
 319static void proto_gre_net_exit(struct net *net)
 320{
 321        struct netns_proto_gre *net_gre = net_generic(net, proto_gre_net_id);
 322
 323        nf_ct_gre_keymap_flush(net);
 324        kfree(net_gre);
 325}
 326
 327static struct pernet_operations proto_gre_net_ops = {
 328        .init = proto_gre_net_init,
 329        .exit = proto_gre_net_exit,
 330};
 331
 332static int __init nf_ct_proto_gre_init(void)
 333{
 334        int rv;
 335
 336        rv = nf_conntrack_l4proto_register(&nf_conntrack_l4proto_gre4);
 337        if (rv < 0)
 338                return rv;
 339        rv = register_pernet_gen_subsys(&proto_gre_net_id, &proto_gre_net_ops);
 340        if (rv < 0)
 341                nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_gre4);
 342        return rv;
 343}
 344
 345static void __exit nf_ct_proto_gre_fini(void)
 346{
 347        nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_gre4);
 348        unregister_pernet_gen_subsys(proto_gre_net_id, &proto_gre_net_ops);
 349}
 350
 351module_init(nf_ct_proto_gre_init);
 352module_exit(nf_ct_proto_gre_fini);
 353
 354MODULE_LICENSE("GPL");
 355