release/src-rt/linux/linux-2.6/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  */
  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/skbuff.h>
  33
  34 #include <net/netfilter/nf_conntrack_l4proto.h>
  35 #include <net/netfilter/nf_conntrack_helper.h>
  36 #include <net/netfilter/nf_conntrack_core.h>
  37 #include <linux/netfilter/nf_conntrack_proto_gre.h>
  38 #include <linux/netfilter/nf_conntrack_pptp.h>
  39
  40 #define GRE_TIMEOUT             (30 * HZ)
  41 #define GRE_STREAM_TIMEOUT      (180 * HZ)
  42
  43 #if 0
  44 #define DEBUGP(format, args...) printk(KERN_DEBUG "%s:%s: " format, __FILE__, __FUNCTION__, ## args)
  45 #else
  46 #define DEBUGP(x, args...)
  47 #endif
  48
  49 static DEFINE_RWLOCK(nf_ct_gre_lock);
  50 static LIST_HEAD(gre_keymap_list);
  51
  52 void nf_ct_gre_keymap_flush(void)
  53 {
  54         struct nf_ct_gre_keymap *km, *tmp;
  55
  56         write_lock_bh(&nf_ct_gre_lock);
  57         list_for_each_entry_safe(km, tmp, &gre_keymap_list, list) {
  58                 list_del(&km->list);
  59                 kfree(km);
  60         }
  61         write_unlock_bh(&nf_ct_gre_lock);
  62 }
  63 EXPORT_SYMBOL(nf_ct_gre_keymap_flush);
  64
  65 static inline int gre_key_cmpfn(const struct nf_ct_gre_keymap *km,
  66                                 const struct nf_conntrack_tuple *t)
  67 {
  68         return km->tuple.src.l3num == t->src.l3num &&
  69                !memcmp(&km->tuple.src.u3, &t->src.u3, sizeof(t->src.u3)) &&
  70                !memcmp(&km->tuple.dst.u3, &t->dst.u3, sizeof(t->dst.u3)) &&
  71                km->tuple.dst.protonum == t->dst.protonum &&
  72                km->tuple.dst.u.all == t->dst.u.all;
  73 }
  74
  75 /* look up the source key for a given tuple */
  76 static __be16 gre_keymap_lookup(struct nf_conntrack_tuple *t)
  77 {
  78         struct nf_ct_gre_keymap *km;
  79         __be16 key = 0;
  80
  81         read_lock_bh(&nf_ct_gre_lock);
  82         list_for_each_entry(km, &gre_keymap_list, list) {
  83                 if (gre_key_cmpfn(km, t)) {
  84                         key = km->tuple.src.u.gre.key;
  85                         break;
  86                 }
  87         }
  88         read_unlock_bh(&nf_ct_gre_lock);
  89
  90         DEBUGP("lookup src key 0x%x for ", key);
  91         NF_CT_DUMP_TUPLE(t);
  92
  93         return key;
  94 }
  95
  96 /* add a single keymap entry, associate with specified master ct */
  97 int nf_ct_gre_keymap_add(struct nf_conn *ct, enum ip_conntrack_dir dir,
  98                          struct nf_conntrack_tuple *t)
  99 {
 100         struct nf_conn_help *help = nfct_help(ct);
 101         struct nf_ct_gre_keymap **kmp, *km;
 102
 103         kmp = &help->help.ct_pptp_info.keymap[dir];
 104         if (*kmp) {
 105                 /* check whether it's a retransmission */
 106                 read_lock_bh(&nf_ct_gre_lock);
 107                 list_for_each_entry(km, &gre_keymap_list, list) {
 108                         if (gre_key_cmpfn(km, t) && km == *kmp) {
 109                                 read_unlock_bh(&nf_ct_gre_lock);
 110                                 return 0;
 111                         }
 112                 }
 113                 read_unlock_bh(&nf_ct_gre_lock);
 114                 DEBUGP("trying to override keymap_%s for ct %p\n",
 115                         dir == IP_CT_DIR_REPLY ? "reply" : "orig", ct);
 116                 return -EEXIST;
 117         }
 118
 119         km = kmalloc(sizeof(*km), GFP_ATOMIC);
 120         if (!km)
 121                 return -ENOMEM;
 122         memcpy(&km->tuple, t, sizeof(*t));
 123         *kmp = km;
 124
 125         DEBUGP("adding new entry %p: ", km);
 126         NF_CT_DUMP_TUPLE(&km->tuple);
 127
 128         write_lock_bh(&nf_ct_gre_lock);
 129         list_add_tail(&km->list, &gre_keymap_list);
 130         write_unlock_bh(&nf_ct_gre_lock);
 131
 132         return 0;
 133 }
 134 EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_add);
 135
 136 /* destroy the keymap entries associated with specified master ct */
 137 void nf_ct_gre_keymap_destroy(struct nf_conn *ct)
 138 {
 139         struct nf_conn_help *help = nfct_help(ct);
 140         enum ip_conntrack_dir dir;
 141
 142         DEBUGP("entering for ct %p\n", ct);
 143
 144         write_lock_bh(&nf_ct_gre_lock);
 145         for (dir = IP_CT_DIR_ORIGINAL; dir < IP_CT_DIR_MAX; dir++) {
 146                 if (help->help.ct_pptp_info.keymap[dir]) {
 147                         DEBUGP("removing %p from list\n",
 148                                 help->help.ct_pptp_info.keymap[dir]);
 149                         list_del(&help->help.ct_pptp_info.keymap[dir]->list);
 150                         kfree(help->help.ct_pptp_info.keymap[dir]);
 151                         help->help.ct_pptp_info.keymap[dir] = NULL;
 152                 }
 153         }
 154         write_unlock_bh(&nf_ct_gre_lock);
 155 }
 156 EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_destroy);
 157
 158 /* PUBLIC CONNTRACK PROTO HELPER FUNCTIONS */
 159
 160 /* invert gre part of tuple */
 161 static int gre_invert_tuple(struct nf_conntrack_tuple *tuple,
 162                             const struct nf_conntrack_tuple *orig)
 163 {
 164         tuple->dst.u.gre.key = orig->src.u.gre.key;
 165         tuple->src.u.gre.key = orig->dst.u.gre.key;
 166         return 1;
 167 }
 168
 169 /* gre hdr info to tuple */
 170 static int gre_pkt_to_tuple(const struct sk_buff *skb,
 171                            unsigned int dataoff,
 172                            struct nf_conntrack_tuple *tuple)
 173 {
 174         struct gre_hdr_pptp _pgrehdr, *pgrehdr;
 175         __be16 srckey;
 176         struct gre_hdr _grehdr, *grehdr;
 177
 178         /* first only delinearize old RFC1701 GRE header */
 179         grehdr = skb_header_pointer(skb, dataoff, sizeof(_grehdr), &_grehdr);
 180         if (!grehdr || grehdr->version != GRE_VERSION_PPTP) {
 181                 /* try to behave like "nf_conntrack_proto_generic" */
 182                 tuple->src.u.all = 0;
 183                 tuple->dst.u.all = 0;
 184                 return 1;
 185         }
 186
 187         /* PPTP header is variable length, only need up to the call_id field */
 188         pgrehdr = skb_header_pointer(skb, dataoff, 8, &_pgrehdr);
 189         if (!pgrehdr)
 190                 return 1;
 191
 192         if (ntohs(grehdr->protocol) != GRE_PROTOCOL_PPTP) {
 193                 DEBUGP("GRE_VERSION_PPTP but unknown proto\n");
 194                 return 0;
 195         }
 196
 197         tuple->dst.u.gre.key = pgrehdr->call_id;
 198         srckey = gre_keymap_lookup(tuple);
 199         tuple->src.u.gre.key = srckey;
 200
 201         return 1;
 202 }
 203
 204 /* print gre part of tuple */
 205 static int gre_print_tuple(struct seq_file *s,
 206                            const struct nf_conntrack_tuple *tuple)
 207 {
 208         return seq_printf(s, "srckey=0x%x dstkey=0x%x ",
 209                           ntohs(tuple->src.u.gre.key),
 210                           ntohs(tuple->dst.u.gre.key));
 211 }
 212
 213 /* print private data for conntrack */
 214 static int gre_print_conntrack(struct seq_file *s,
 215                                const struct nf_conn *ct)
 216 {
 217         return seq_printf(s, "timeout=%u, stream_timeout=%u ",
 218                           (ct->proto.gre.timeout / HZ),
 219                           (ct->proto.gre.stream_timeout / HZ));
 220 }
 221
 222 /* Returns verdict for packet, and may modify conntrack */
 223 static int gre_packet(struct nf_conn *ct,
 224                       const struct sk_buff *skb,
 225                       unsigned int dataoff,
 226                       enum ip_conntrack_info ctinfo,
 227                       int pf,
 228                       unsigned int hooknum)
 229 {
 230         /* If we've seen traffic both ways, this is a GRE connection.
 231          * Extend timeout. */
 232         if (ct->status & IPS_SEEN_REPLY) {
 233                 nf_ct_refresh_acct(ct, ctinfo, skb,
 234                                    ct->proto.gre.stream_timeout);
 235                 /* Also, more likely to be important, and not a probe. */
 236                 if (!test_and_set_bit(IPS_ASSURED_BIT, &ct->status))
 237                         nf_conntrack_event_cache(IPCT_STATUS, skb);
 238         } else
 239                 nf_ct_refresh_acct(ct, ctinfo, skb,
 240                                    ct->proto.gre.timeout);
 241
 242         return NF_ACCEPT;
 243 }
 244
 245 /* Called when a new connection for this protocol found. */
 246 static int gre_new(struct nf_conn *ct, const struct sk_buff *skb,
 247                    unsigned int dataoff)
 248 {
 249         DEBUGP(": ");
 250         NF_CT_DUMP_TUPLE(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
 251
 252         /* initialize to sane value.  Ideally a conntrack helper
 253          * (e.g. in case of pptp) is increasing them */
 254         ct->proto.gre.stream_timeout = GRE_STREAM_TIMEOUT;
 255         ct->proto.gre.timeout = GRE_TIMEOUT;
 256
 257         return 1;
 258 }
 259
 260 /* Called when a conntrack entry has already been removed from the hashes
 261  * and is about to be deleted from memory */
 262 static void gre_destroy(struct nf_conn *ct)
 263 {
 264         struct nf_conn *master = ct->master;
 265         DEBUGP(" entering\n");
 266
 267         if (!master)
 268                 DEBUGP("no master !?!\n");
 269         else
 270                 nf_ct_gre_keymap_destroy(master);
 271 }
 272
 273 /* protocol helper struct */
 274 static struct nf_conntrack_l4proto nf_conntrack_l4proto_gre4 = {
 275         .l3proto         = AF_INET,
 276         .l4proto         = IPPROTO_GRE,
 277         .name            = "gre",
 278         .pkt_to_tuple    = gre_pkt_to_tuple,
 279         .invert_tuple    = gre_invert_tuple,
 280         .print_tuple     = gre_print_tuple,
 281         .print_conntrack = gre_print_conntrack,
 282         .packet          = gre_packet,
 283         .new             = gre_new,
 284         .destroy         = gre_destroy,
 285         .me              = THIS_MODULE,
 286 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
 287         .tuple_to_nfattr = nf_ct_port_tuple_to_nfattr,
 288         .nfattr_to_tuple = nf_ct_port_nfattr_to_tuple,
 289 #endif
 290 };
 291
 292 static int __init nf_ct_proto_gre_init(void)
 293 {
 294         return nf_conntrack_l4proto_register(&nf_conntrack_l4proto_gre4);
 295 }
 296
 297 static void nf_ct_proto_gre_fini(void)
 298 {
 299         nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_gre4);
 300         nf_ct_gre_keymap_flush();
 301 }
 302
 303 module_init(nf_ct_proto_gre_init);
 304 module_exit(nf_ct_proto_gre_fini);
 305
 306 MODULE_LICENSE("GPL");