2 * ip_conntrack_proto_gre.c - Version 3.0
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) 2000-2005 by Harald Welte <laforge@gnumonks.org>
22 * Development of this code funded by Astaro AG (http://www.astaro.com/)
26 #include <linux/module.h>
27 #include <linux/types.h>
28 #include <linux/timer.h>
29 #include <linux/netfilter.h>
32 #include <linux/list.h>
33 #include <linux/seq_file.h>
34 #include <linux/interrupt.h>
36 static DEFINE_RWLOCK(ip_ct_gre_lock);
37 #define ASSERT_READ_LOCK(x)
38 #define ASSERT_WRITE_LOCK(x)
40 #include <linux/netfilter_ipv4/ip_conntrack_protocol.h>
41 #include <linux/netfilter_ipv4/ip_conntrack_helper.h>
42 #include <linux/netfilter_ipv4/ip_conntrack_core.h>
44 #include <linux/netfilter_ipv4/ip_conntrack_proto_gre.h>
45 #include <linux/netfilter_ipv4/ip_conntrack_pptp.h>
47 MODULE_LICENSE("GPL");
48 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
49 MODULE_DESCRIPTION("netfilter connection tracking protocol helper for GRE");
51 /* shamelessly stolen from ip_conntrack_proto_udp.c */
52 #define GRE_TIMEOUT (30*HZ)
53 #define GRE_STREAM_TIMEOUT (180*HZ)
56 #define DEBUGP(format, args...) printk(KERN_DEBUG "%s:%s: " format, __FILE__, __FUNCTION__, ## args)
57 #define DUMP_TUPLE_GRE(x) printk("%u.%u.%u.%u:0x%x -> %u.%u.%u.%u:0x%x\n", \
58 NIPQUAD((x)->src.ip), ntohs((x)->src.u.gre.key), \
59 NIPQUAD((x)->dst.ip), ntohs((x)->dst.u.gre.key))
61 #define DEBUGP(x, args...)
62 #define DUMP_TUPLE_GRE(x)
65 /* GRE KEYMAP HANDLING FUNCTIONS */
66 static LIST_HEAD(gre_keymap_list);
68 static inline int gre_key_cmpfn(const struct ip_ct_gre_keymap *km,
69 const struct ip_conntrack_tuple *t)
71 return ((km->tuple.src.ip == t->src.ip) &&
72 (km->tuple.dst.ip == t->dst.ip) &&
73 (km->tuple.dst.protonum == t->dst.protonum) &&
74 (km->tuple.dst.u.all == t->dst.u.all));
77 /* look up the source key for a given tuple */
78 static __be16 gre_keymap_lookup(struct ip_conntrack_tuple *t)
80 struct ip_ct_gre_keymap *km;
83 read_lock_bh(&ip_ct_gre_lock);
84 list_for_each_entry(km, &gre_keymap_list, list) {
85 if (gre_key_cmpfn(km, t)) {
86 key = km->tuple.src.u.gre.key;
90 read_unlock_bh(&ip_ct_gre_lock);
92 DEBUGP("lookup src key 0x%x up key for ", key);
98 /* add a single keymap entry, associate with specified master ct */
100 ip_ct_gre_keymap_add(struct ip_conntrack *ct,
101 struct ip_conntrack_tuple *t, int reply)
103 struct ip_ct_gre_keymap **exist_km, *km;
105 if (!ct->helper || strcmp(ct->helper->name, "pptp")) {
106 DEBUGP("refusing to add GRE keymap to non-pptp session\n");
111 exist_km = &ct->help.ct_pptp_info.keymap_orig;
113 exist_km = &ct->help.ct_pptp_info.keymap_reply;
116 /* check whether it's a retransmission */
117 list_for_each_entry(km, &gre_keymap_list, list) {
118 if (gre_key_cmpfn(km, t) && km == *exist_km)
121 DEBUGP("trying to override keymap_%s for ct %p\n",
122 reply? "reply":"orig", ct);
126 km = kmalloc(sizeof(*km), GFP_ATOMIC);
130 memcpy(&km->tuple, t, sizeof(*t));
133 DEBUGP("adding new entry %p: ", km);
134 DUMP_TUPLE_GRE(&km->tuple);
136 write_lock_bh(&ip_ct_gre_lock);
137 list_add_tail(&km->list, &gre_keymap_list);
138 write_unlock_bh(&ip_ct_gre_lock);
143 /* destroy the keymap entries associated with specified master ct */
144 void ip_ct_gre_keymap_destroy(struct ip_conntrack *ct)
146 DEBUGP("entering for ct %p\n", ct);
148 if (!ct->helper || strcmp(ct->helper->name, "pptp")) {
149 DEBUGP("refusing to destroy GRE keymap to non-pptp session\n");
153 write_lock_bh(&ip_ct_gre_lock);
154 if (ct->help.ct_pptp_info.keymap_orig) {
155 DEBUGP("removing %p from list\n",
156 ct->help.ct_pptp_info.keymap_orig);
157 list_del(&ct->help.ct_pptp_info.keymap_orig->list);
158 kfree(ct->help.ct_pptp_info.keymap_orig);
159 ct->help.ct_pptp_info.keymap_orig = NULL;
161 if (ct->help.ct_pptp_info.keymap_reply) {
162 DEBUGP("removing %p from list\n",
163 ct->help.ct_pptp_info.keymap_reply);
164 list_del(&ct->help.ct_pptp_info.keymap_reply->list);
165 kfree(ct->help.ct_pptp_info.keymap_reply);
166 ct->help.ct_pptp_info.keymap_reply = NULL;
168 write_unlock_bh(&ip_ct_gre_lock);
172 /* PUBLIC CONNTRACK PROTO HELPER FUNCTIONS */
174 /* invert gre part of tuple */
175 static int gre_invert_tuple(struct ip_conntrack_tuple *tuple,
176 const struct ip_conntrack_tuple *orig)
178 tuple->dst.u.gre.key = orig->src.u.gre.key;
179 tuple->src.u.gre.key = orig->dst.u.gre.key;
184 /* gre hdr info to tuple */
185 static int gre_pkt_to_tuple(const struct sk_buff *skb,
186 unsigned int dataoff,
187 struct ip_conntrack_tuple *tuple)
189 struct gre_hdr_pptp _pgrehdr, *pgrehdr;
191 struct gre_hdr _grehdr, *grehdr;
193 /* first only delinearize old RFC1701 GRE header */
194 grehdr = skb_header_pointer(skb, dataoff, sizeof(_grehdr), &_grehdr);
195 if (!grehdr || grehdr->version != GRE_VERSION_PPTP) {
196 /* try to behave like "ip_conntrack_proto_generic" */
197 tuple->src.u.all = 0;
198 tuple->dst.u.all = 0;
202 /* PPTP header is variable length, only need up to the call_id field */
203 pgrehdr = skb_header_pointer(skb, dataoff, 8, &_pgrehdr);
207 if (ntohs(grehdr->protocol) != GRE_PROTOCOL_PPTP) {
208 DEBUGP("GRE_VERSION_PPTP but unknown proto\n");
212 tuple->dst.u.gre.key = pgrehdr->call_id;
213 srckey = gre_keymap_lookup(tuple);
214 tuple->src.u.gre.key = srckey;
219 /* print gre part of tuple */
220 static int gre_print_tuple(struct seq_file *s,
221 const struct ip_conntrack_tuple *tuple)
223 return seq_printf(s, "srckey=0x%x dstkey=0x%x ",
224 ntohs(tuple->src.u.gre.key),
225 ntohs(tuple->dst.u.gre.key));
228 /* print private data for conntrack */
229 static int gre_print_conntrack(struct seq_file *s,
230 const struct ip_conntrack *ct)
232 return seq_printf(s, "timeout=%u, stream_timeout=%u ",
233 (ct->proto.gre.timeout / HZ),
234 (ct->proto.gre.stream_timeout / HZ));
237 /* Returns verdict for packet, and may modify conntrack */
238 static int gre_packet(struct ip_conntrack *ct,
239 const struct sk_buff *skb,
240 enum ip_conntrack_info conntrackinfo)
242 /* If we've seen traffic both ways, this is a GRE connection.
244 if (ct->status & IPS_SEEN_REPLY) {
245 ip_ct_refresh_acct(ct, conntrackinfo, skb,
246 ct->proto.gre.stream_timeout);
247 /* Also, more likely to be important, and not a probe. */
248 set_bit(IPS_ASSURED_BIT, &ct->status);
249 ip_conntrack_event_cache(IPCT_STATUS, skb);
251 ip_ct_refresh_acct(ct, conntrackinfo, skb,
252 ct->proto.gre.timeout);
257 /* Called when a new connection for this protocol found. */
258 static int gre_new(struct ip_conntrack *ct,
259 const struct sk_buff *skb)
262 DUMP_TUPLE_GRE(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
264 /* initialize to sane value. Ideally a conntrack helper
265 * (e.g. in case of pptp) is increasing them */
266 ct->proto.gre.stream_timeout = GRE_STREAM_TIMEOUT;
267 ct->proto.gre.timeout = GRE_TIMEOUT;
272 /* Called when a conntrack entry has already been removed from the hashes
273 * and is about to be deleted from memory */
274 static void gre_destroy(struct ip_conntrack *ct)
276 struct ip_conntrack *master = ct->master;
277 DEBUGP(" entering\n");
280 DEBUGP("no master !?!\n");
282 ip_ct_gre_keymap_destroy(master);
285 /* protocol helper struct */
286 static struct ip_conntrack_protocol gre = {
287 .proto = IPPROTO_GRE,
289 .pkt_to_tuple = gre_pkt_to_tuple,
290 .invert_tuple = gre_invert_tuple,
291 .print_tuple = gre_print_tuple,
292 .print_conntrack = gre_print_conntrack,
293 .packet = gre_packet,
295 .destroy = gre_destroy,
297 #if defined(CONFIG_IP_NF_CONNTRACK_NETLINK) || \
298 defined(CONFIG_IP_NF_CONNTRACK_NETLINK_MODULE)
299 .tuple_to_nfattr = ip_ct_port_tuple_to_nfattr,
300 .nfattr_to_tuple = ip_ct_port_nfattr_to_tuple,
304 /* ip_conntrack_proto_gre initialization */
305 int __init ip_ct_proto_gre_init(void)
307 return ip_conntrack_protocol_register(&gre);
310 /* This cannot be __exit, as it is invoked from ip_conntrack_helper_pptp.c's
311 * init() code on errors.
313 void ip_ct_proto_gre_fini(void)
315 struct list_head *pos, *n;
317 /* delete all keymap entries */
318 write_lock_bh(&ip_ct_gre_lock);
319 list_for_each_safe(pos, n, &gre_keymap_list) {
320 DEBUGP("deleting keymap %p at module unload time\n", pos);
324 write_unlock_bh(&ip_ct_gre_lock);
326 ip_conntrack_protocol_unregister(&gre);
329 EXPORT_SYMBOL(ip_ct_gre_keymap_add);
330 EXPORT_SYMBOL(ip_ct_gre_keymap_destroy);