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