2 * ip_conntrack_proto_gre.c - Version 2.0
4 * Connection tracking protocol helper module for GRE.
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.
9 * It has an optional key field, which may help us distinguishing two
10 * connections between the same two hosts.
12 * GRE is defined in RFC 1701 and RFC 1702, as well as RFC 2784
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
18 * Documentation about PPTP can be found in RFC 2637
20 * (C) 2000-2004 by Harald Welte <laforge@gnumonks.org>
22 * Development of this code funded by Astaro AG (http://www.astaro.com/)
26 #include <linux/config.h>
27 #include <linux/module.h>
28 #include <linux/types.h>
29 #include <linux/timer.h>
30 #include <linux/netfilter.h>
33 #include <linux/list.h>
35 #include <linux/netfilter_ipv4/lockhelp.h>
37 DECLARE_RWLOCK(ip_ct_gre_lock);
38 #define ASSERT_READ_LOCK(x) MUST_BE_READ_LOCKED(&ip_ct_gre_lock)
39 #define ASSERT_WRITE_LOCK(x) MUST_BE_WRITE_LOCKED(&ip_ct_gre_lock)
41 #include <linux/netfilter_ipv4/listhelp.h>
42 #include <linux/netfilter_ipv4/ip_conntrack_protocol.h>
43 #include <linux/netfilter_ipv4/ip_conntrack_helper.h>
44 #include <linux/netfilter_ipv4/ip_conntrack_core.h>
46 #include <linux/netfilter_ipv4/ip_conntrack_proto_gre.h>
47 #include <linux/netfilter_ipv4/ip_conntrack_pptp.h>
49 MODULE_LICENSE("GPL");
50 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
51 MODULE_DESCRIPTION("netfilter connection tracking protocol helper for GRE");
53 /* shamelessly stolen from ip_conntrack_proto_udp.c */
54 #define GRE_TIMEOUT (30*HZ)
55 #define GRE_STREAM_TIMEOUT (180*HZ)
58 #define DEBUGP(format, args...) printk(KERN_DEBUG "%s:%s: " format, __FILE__, __FUNCTION__, ## args)
59 #define DUMP_TUPLE_GRE(x) printk("%u.%u.%u.%u:0x%x -> %u.%u.%u.%u:0x%x\n", \
60 NIPQUAD((x)->src.ip), ntohl((x)->src.u.gre.key), \
61 NIPQUAD((x)->dst.ip), ntohl((x)->dst.u.gre.key))
63 #define DEBUGP(x, args...)
64 #define DUMP_TUPLE_GRE(x)
67 /* GRE KEYMAP HANDLING FUNCTIONS */
68 static LIST_HEAD(gre_keymap_list);
70 static inline int gre_key_cmpfn(const struct ip_ct_gre_keymap *km,
71 const struct ip_conntrack_tuple *t)
73 return ((km->tuple.src.ip == t->src.ip) &&
74 (km->tuple.dst.ip == t->dst.ip) &&
75 (km->tuple.dst.protonum == t->dst.protonum) &&
76 (km->tuple.dst.u.all == t->dst.u.all));
79 /* look up the source key for a given tuple */
80 static u_int32_t gre_keymap_lookup(struct ip_conntrack_tuple *t)
82 struct ip_ct_gre_keymap *km;
85 READ_LOCK(&ip_ct_gre_lock);
86 km = LIST_FIND(&gre_keymap_list, gre_key_cmpfn,
87 struct ip_ct_gre_keymap *, t);
89 READ_UNLOCK(&ip_ct_gre_lock);
93 key = km->tuple.src.u.gre.key;
94 READ_UNLOCK(&ip_ct_gre_lock);
99 /* add a single keymap entry, associate with specified expect */
100 int ip_ct_gre_keymap_add(struct ip_conntrack_expect *exp,
101 struct ip_conntrack_tuple *t, int reply)
103 struct ip_ct_gre_keymap *km;
105 km = kmalloc(sizeof(*km), GFP_ATOMIC);
109 /* initializing list head should be sufficient */
110 memset(km, 0, sizeof(*km));
112 memcpy(&km->tuple, t, sizeof(*t));
115 exp->proto.gre.keymap_orig = km;
117 exp->proto.gre.keymap_reply = km;
119 DEBUGP("adding new entry %p: ", km);
120 DUMP_TUPLE_GRE(&km->tuple);
122 WRITE_LOCK(&ip_ct_gre_lock);
123 list_append(&gre_keymap_list, km);
124 WRITE_UNLOCK(&ip_ct_gre_lock);
129 /* change the tuple of a keymap entry (used by nat helper) */
130 void ip_ct_gre_keymap_change(struct ip_ct_gre_keymap *km,
131 struct ip_conntrack_tuple *t)
136 "NULL GRE conntrack keymap change requested\n");
140 DEBUGP("changing entry %p to: ", km);
143 WRITE_LOCK(&ip_ct_gre_lock);
144 memcpy(&km->tuple, t, sizeof(km->tuple));
145 WRITE_UNLOCK(&ip_ct_gre_lock);
148 /* destroy the keymap entries associated with specified expect */
149 void ip_ct_gre_keymap_destroy(struct ip_conntrack_expect *exp)
151 DEBUGP("entering for exp %p\n", exp);
152 WRITE_LOCK(&ip_ct_gre_lock);
153 if (exp->proto.gre.keymap_orig) {
154 DEBUGP("removing %p from list\n", exp->proto.gre.keymap_orig);
155 list_del(&exp->proto.gre.keymap_orig->list);
156 kfree(exp->proto.gre.keymap_orig);
157 exp->proto.gre.keymap_orig = NULL;
159 if (exp->proto.gre.keymap_reply) {
160 DEBUGP("removing %p from list\n", exp->proto.gre.keymap_reply);
161 list_del(&exp->proto.gre.keymap_reply->list);
162 kfree(exp->proto.gre.keymap_reply);
163 exp->proto.gre.keymap_reply = NULL;
165 WRITE_UNLOCK(&ip_ct_gre_lock);
169 /* PUBLIC CONNTRACK PROTO HELPER FUNCTIONS */
171 /* invert gre part of tuple */
172 static int gre_invert_tuple(struct ip_conntrack_tuple *tuple,
173 const struct ip_conntrack_tuple *orig)
175 tuple->dst.u.gre.key = orig->src.u.gre.key;
176 tuple->src.u.gre.key = orig->dst.u.gre.key;
181 /* gre hdr info to tuple */
182 static int gre_pkt_to_tuple(const struct sk_buff *skb,
183 unsigned int dataoff,
184 struct ip_conntrack_tuple *tuple)
186 struct gre_hdr _grehdr, *grehdr;
187 struct gre_hdr_pptp _pgrehdr, *pgrehdr;
190 grehdr = skb_header_pointer(skb, dataoff, sizeof(_grehdr), &_grehdr);
191 /* PPTP header is variable length, only need up to the call_id field */
192 pgrehdr = skb_header_pointer(skb, dataoff, 8, &_pgrehdr);
194 if (!grehdr || !pgrehdr)
197 switch (grehdr->version) {
198 case GRE_VERSION_1701:
200 DEBUGP("Can't track GRE without key\n");
203 tuple->dst.u.gre.key = *(gre_key(grehdr));
206 case GRE_VERSION_PPTP:
207 if (ntohs(grehdr->protocol) != GRE_PROTOCOL_PPTP) {
208 DEBUGP("GRE_VERSION_PPTP but unknown proto\n");
211 tuple->dst.u.gre.key = htonl(ntohs(pgrehdr->call_id));
215 printk(KERN_WARNING "unknown GRE version %hu\n",
220 srckey = gre_keymap_lookup(tuple);
222 tuple->src.u.gre.key = srckey;
224 DEBUGP("found src key %x for tuple ", ntohl(srckey));
225 DUMP_TUPLE_GRE(tuple);
231 /* print gre part of tuple */
232 static unsigned int gre_print_tuple(char *buffer,
233 const struct ip_conntrack_tuple *tuple)
235 return sprintf(buffer, "srckey=0x%x dstkey=0x%x ",
236 ntohl(tuple->src.u.gre.key),
237 ntohl(tuple->dst.u.gre.key));
240 /* print private data for conntrack */
241 static unsigned int gre_print_conntrack(char *buffer,
242 const struct ip_conntrack *ct)
244 return sprintf(buffer, "timeout=%u, stream_timeout=%u ",
245 (ct->proto.gre.timeout / HZ),
246 (ct->proto.gre.stream_timeout / HZ));
249 /* Returns verdict for packet, and may modify conntrack */
250 static int gre_packet(struct ip_conntrack *ct,
251 const struct sk_buff *skb,
252 enum ip_conntrack_info conntrackinfo)
254 /* If we've seen traffic both ways, this is a GRE connection.
256 if (ct->status & IPS_SEEN_REPLY) {
257 ip_ct_refresh_acct(ct, conntrackinfo, skb,
258 ct->proto.gre.stream_timeout);
259 /* Also, more likely to be important, and not a probe. */
260 set_bit(IPS_ASSURED_BIT, &ct->status);
262 ip_ct_refresh_acct(ct, conntrackinfo, skb,
263 ct->proto.gre.timeout);
268 /* Called when a new connection for this protocol found. */
269 static int gre_new(struct ip_conntrack *ct,
270 const struct sk_buff *skb)
273 DUMP_TUPLE_GRE(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
275 /* initialize to sane value. Ideally a conntrack helper
276 * (e.g. in case of pptp) is increasing them */
277 ct->proto.gre.stream_timeout = GRE_STREAM_TIMEOUT;
278 ct->proto.gre.timeout = GRE_TIMEOUT;
283 /* Called when a conntrack entry has already been removed from the hashes
284 * and is about to be deleted from memory */
285 static void gre_destroy(struct ip_conntrack *ct)
287 struct ip_conntrack_expect *master = ct->master;
289 DEBUGP(" entering\n");
292 DEBUGP("no master exp for ct %p\n", ct);
296 ip_ct_gre_keymap_destroy(master);
299 /* protocol helper struct */
300 static struct ip_conntrack_protocol gre = {
301 .proto = IPPROTO_GRE,
303 .pkt_to_tuple = gre_pkt_to_tuple,
304 .invert_tuple = gre_invert_tuple,
305 .print_tuple = gre_print_tuple,
306 .print_conntrack = gre_print_conntrack,
307 .packet = gre_packet,
309 .destroy = gre_destroy,
310 .exp_matches_pkt = NULL,
314 /* ip_conntrack_proto_gre initialization */
315 static int __init init(void)
319 if ((retcode = ip_conntrack_protocol_register(&gre))) {
320 printk(KERN_ERR "Unable to register conntrack protocol "
321 "helper for gre: %d\n", retcode);
328 static void __exit fini(void)
330 struct list_head *pos, *n;
332 /* delete all keymap entries */
333 WRITE_LOCK(&ip_ct_gre_lock);
334 list_for_each_safe(pos, n, &gre_keymap_list) {
335 DEBUGP("deleting keymap %p at module unload time\n", pos);
339 WRITE_UNLOCK(&ip_ct_gre_lock);
341 ip_conntrack_protocol_unregister(&gre);
344 EXPORT_SYMBOL(ip_ct_gre_keymap_add);
345 EXPORT_SYMBOL(ip_ct_gre_keymap_change);
346 EXPORT_SYMBOL(ip_ct_gre_keymap_destroy);