Patrick McHardy | f09943f | 2006-12-02 22:09:41 -0800 | [diff] [blame] | 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 list_head *pos, *n; |
| 55 | |
| 56 | write_lock_bh(&nf_ct_gre_lock); |
| 57 | list_for_each_safe(pos, n, &gre_keymap_list) { |
| 58 | list_del(pos); |
| 59 | kfree(pos); |
| 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 | BUG_ON(strcmp(help->helper->name, "pptp")); |
| 104 | kmp = &help->help.ct_pptp_info.keymap[dir]; |
| 105 | if (*kmp) { |
| 106 | /* check whether it's a retransmission */ |
| 107 | list_for_each_entry(km, &gre_keymap_list, list) { |
| 108 | if (gre_key_cmpfn(km, t) && km == *kmp) |
| 109 | return 0; |
| 110 | } |
| 111 | DEBUGP("trying to override keymap_%s for ct %p\n", |
| 112 | dir == IP_CT_DIR_REPLY ? "reply" : "orig", ct); |
| 113 | return -EEXIST; |
| 114 | } |
| 115 | |
| 116 | km = kmalloc(sizeof(*km), GFP_ATOMIC); |
| 117 | if (!km) |
| 118 | return -ENOMEM; |
| 119 | memcpy(&km->tuple, t, sizeof(*t)); |
| 120 | *kmp = km; |
| 121 | |
| 122 | DEBUGP("adding new entry %p: ", km); |
| 123 | NF_CT_DUMP_TUPLE(&km->tuple); |
| 124 | |
| 125 | write_lock_bh(&nf_ct_gre_lock); |
| 126 | list_add_tail(&km->list, &gre_keymap_list); |
| 127 | write_unlock_bh(&nf_ct_gre_lock); |
| 128 | |
| 129 | return 0; |
| 130 | } |
| 131 | EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_add); |
| 132 | |
| 133 | /* destroy the keymap entries associated with specified master ct */ |
| 134 | void nf_ct_gre_keymap_destroy(struct nf_conn *ct) |
| 135 | { |
| 136 | struct nf_conn_help *help = nfct_help(ct); |
| 137 | enum ip_conntrack_dir dir; |
| 138 | |
| 139 | DEBUGP("entering for ct %p\n", ct); |
| 140 | BUG_ON(strcmp(help->helper->name, "pptp")); |
| 141 | |
| 142 | write_lock_bh(&nf_ct_gre_lock); |
| 143 | for (dir = IP_CT_DIR_ORIGINAL; dir < IP_CT_DIR_MAX; dir++) { |
| 144 | if (help->help.ct_pptp_info.keymap[dir]) { |
| 145 | DEBUGP("removing %p from list\n", |
| 146 | help->help.ct_pptp_info.keymap[dir]); |
| 147 | list_del(&help->help.ct_pptp_info.keymap[dir]->list); |
| 148 | kfree(help->help.ct_pptp_info.keymap[dir]); |
| 149 | help->help.ct_pptp_info.keymap[dir] = NULL; |
| 150 | } |
| 151 | } |
| 152 | write_unlock_bh(&nf_ct_gre_lock); |
| 153 | } |
| 154 | EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_destroy); |
| 155 | |
| 156 | /* PUBLIC CONNTRACK PROTO HELPER FUNCTIONS */ |
| 157 | |
| 158 | /* invert gre part of tuple */ |
| 159 | static int gre_invert_tuple(struct nf_conntrack_tuple *tuple, |
| 160 | const struct nf_conntrack_tuple *orig) |
| 161 | { |
| 162 | tuple->dst.u.gre.key = orig->src.u.gre.key; |
| 163 | tuple->src.u.gre.key = orig->dst.u.gre.key; |
| 164 | return 1; |
| 165 | } |
| 166 | |
| 167 | /* gre hdr info to tuple */ |
| 168 | static int gre_pkt_to_tuple(const struct sk_buff *skb, |
| 169 | unsigned int dataoff, |
| 170 | struct nf_conntrack_tuple *tuple) |
| 171 | { |
| 172 | struct gre_hdr_pptp _pgrehdr, *pgrehdr; |
| 173 | __be16 srckey; |
| 174 | struct gre_hdr _grehdr, *grehdr; |
| 175 | |
| 176 | /* first only delinearize old RFC1701 GRE header */ |
| 177 | grehdr = skb_header_pointer(skb, dataoff, sizeof(_grehdr), &_grehdr); |
| 178 | if (!grehdr || grehdr->version != GRE_VERSION_PPTP) { |
| 179 | /* try to behave like "nf_conntrack_proto_generic" */ |
| 180 | tuple->src.u.all = 0; |
| 181 | tuple->dst.u.all = 0; |
| 182 | return 1; |
| 183 | } |
| 184 | |
| 185 | /* PPTP header is variable length, only need up to the call_id field */ |
| 186 | pgrehdr = skb_header_pointer(skb, dataoff, 8, &_pgrehdr); |
| 187 | if (!pgrehdr) |
| 188 | return 1; |
| 189 | |
| 190 | if (ntohs(grehdr->protocol) != GRE_PROTOCOL_PPTP) { |
| 191 | DEBUGP("GRE_VERSION_PPTP but unknown proto\n"); |
| 192 | return 0; |
| 193 | } |
| 194 | |
| 195 | tuple->dst.u.gre.key = pgrehdr->call_id; |
| 196 | srckey = gre_keymap_lookup(tuple); |
| 197 | tuple->src.u.gre.key = srckey; |
| 198 | |
| 199 | return 1; |
| 200 | } |
| 201 | |
| 202 | /* print gre part of tuple */ |
| 203 | static int gre_print_tuple(struct seq_file *s, |
| 204 | const struct nf_conntrack_tuple *tuple) |
| 205 | { |
| 206 | return seq_printf(s, "srckey=0x%x dstkey=0x%x ", |
| 207 | ntohs(tuple->src.u.gre.key), |
| 208 | ntohs(tuple->dst.u.gre.key)); |
| 209 | } |
| 210 | |
| 211 | /* print private data for conntrack */ |
| 212 | static int gre_print_conntrack(struct seq_file *s, |
| 213 | const struct nf_conn *ct) |
| 214 | { |
| 215 | return seq_printf(s, "timeout=%u, stream_timeout=%u ", |
| 216 | (ct->proto.gre.timeout / HZ), |
| 217 | (ct->proto.gre.stream_timeout / HZ)); |
| 218 | } |
| 219 | |
| 220 | /* Returns verdict for packet, and may modify conntrack */ |
| 221 | static int gre_packet(struct nf_conn *ct, |
| 222 | const struct sk_buff *skb, |
| 223 | unsigned int dataoff, |
| 224 | enum ip_conntrack_info ctinfo, |
| 225 | int pf, |
| 226 | unsigned int hooknum) |
| 227 | { |
| 228 | /* If we've seen traffic both ways, this is a GRE connection. |
| 229 | * Extend timeout. */ |
| 230 | if (ct->status & IPS_SEEN_REPLY) { |
| 231 | nf_ct_refresh_acct(ct, ctinfo, skb, |
| 232 | ct->proto.gre.stream_timeout); |
| 233 | /* Also, more likely to be important, and not a probe. */ |
| 234 | set_bit(IPS_ASSURED_BIT, &ct->status); |
| 235 | nf_conntrack_event_cache(IPCT_STATUS, skb); |
| 236 | } else |
| 237 | nf_ct_refresh_acct(ct, ctinfo, skb, |
| 238 | ct->proto.gre.timeout); |
| 239 | |
| 240 | return NF_ACCEPT; |
| 241 | } |
| 242 | |
| 243 | /* Called when a new connection for this protocol found. */ |
| 244 | static int gre_new(struct nf_conn *ct, const struct sk_buff *skb, |
| 245 | unsigned int dataoff) |
| 246 | { |
| 247 | DEBUGP(": "); |
| 248 | NF_CT_DUMP_TUPLE(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple); |
| 249 | |
| 250 | /* initialize to sane value. Ideally a conntrack helper |
| 251 | * (e.g. in case of pptp) is increasing them */ |
| 252 | ct->proto.gre.stream_timeout = GRE_STREAM_TIMEOUT; |
| 253 | ct->proto.gre.timeout = GRE_TIMEOUT; |
| 254 | |
| 255 | return 1; |
| 256 | } |
| 257 | |
| 258 | /* Called when a conntrack entry has already been removed from the hashes |
| 259 | * and is about to be deleted from memory */ |
| 260 | static void gre_destroy(struct nf_conn *ct) |
| 261 | { |
| 262 | struct nf_conn *master = ct->master; |
| 263 | DEBUGP(" entering\n"); |
| 264 | |
| 265 | if (!master) |
| 266 | DEBUGP("no master !?!\n"); |
| 267 | else |
| 268 | nf_ct_gre_keymap_destroy(master); |
| 269 | } |
| 270 | |
| 271 | /* protocol helper struct */ |
| 272 | static struct nf_conntrack_l4proto nf_conntrack_l4proto_gre4 = { |
| 273 | .l3proto = AF_INET, |
| 274 | .l4proto = IPPROTO_GRE, |
| 275 | .name = "gre", |
| 276 | .pkt_to_tuple = gre_pkt_to_tuple, |
| 277 | .invert_tuple = gre_invert_tuple, |
| 278 | .print_tuple = gre_print_tuple, |
| 279 | .print_conntrack = gre_print_conntrack, |
| 280 | .packet = gre_packet, |
| 281 | .new = gre_new, |
| 282 | .destroy = gre_destroy, |
| 283 | .me = THIS_MODULE, |
Patrick McHardy | e281db5c | 2007-03-04 15:57:25 -0800 | [diff] [blame] | 284 | #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE) |
Patrick McHardy | f09943f | 2006-12-02 22:09:41 -0800 | [diff] [blame] | 285 | .tuple_to_nfattr = nf_ct_port_tuple_to_nfattr, |
| 286 | .nfattr_to_tuple = nf_ct_port_nfattr_to_tuple, |
| 287 | #endif |
| 288 | }; |
| 289 | |
| 290 | static int __init nf_ct_proto_gre_init(void) |
| 291 | { |
| 292 | return nf_conntrack_l4proto_register(&nf_conntrack_l4proto_gre4); |
| 293 | } |
| 294 | |
| 295 | static void nf_ct_proto_gre_fini(void) |
| 296 | { |
| 297 | nf_conntrack_l4proto_unregister(&nf_conntrack_l4proto_gre4); |
| 298 | nf_ct_gre_keymap_flush(); |
| 299 | } |
| 300 | |
| 301 | module_init(nf_ct_proto_gre_init); |
| 302 | module_exit(nf_ct_proto_gre_fini); |
| 303 | |
| 304 | MODULE_LICENSE("GPL"); |