1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Connection tracking protocol helper module for GRE.
4 *
5 * GRE is a generic encapsulation protocol, which is generally not very
6 * suited for NAT, as it has no protocol-specific part as port numbers.
7 *
8 * It has an optional key field, which may help us distinguishing two
9 * connections between the same two hosts.
10 *
11 * GRE is defined in RFC 1701 and RFC 1702, as well as RFC 2784
12 *
13 * PPTP is built on top of a modified version of GRE, and has a mandatory
14 * field called "CallID", which serves us for the same purpose as the key
15 * field in plain GRE.
16 *
17 * Documentation about PPTP can be found in RFC 2637
18 *
19 * (C) 2000-2005 by Harald Welte <laforge@gnumonks.org>
20 *
21 * Development of this code funded by Astaro AG (http://www.astaro.com/)
22 *
23 * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
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/netdevice.h>
33 #include <linux/skbuff.h>
34 #include <linux/slab.h>
35 #include <net/dst.h>
36 #include <net/net_namespace.h>
37 #include <net/netns/generic.h>
38 #include <net/netfilter/nf_conntrack_l4proto.h>
39 #include <net/netfilter/nf_conntrack_helper.h>
40 #include <net/netfilter/nf_conntrack_core.h>
41 #include <net/netfilter/nf_conntrack_timeout.h>
42 #include <linux/netfilter/nf_conntrack_proto_gre.h>
43 #include <linux/netfilter/nf_conntrack_pptp.h>
44
45 static const unsigned int gre_timeouts[GRE_CT_MAX] = {
46 [GRE_CT_UNREPLIED] = 30*HZ,
47 [GRE_CT_REPLIED] = 180*HZ,
48 };
49
50 /* used when expectation is added */
51 static DEFINE_SPINLOCK(keymap_lock);
52
gre_pernet(struct net * net)53 static inline struct nf_gre_net *gre_pernet(struct net *net)
54 {
55 return &net->ct.nf_ct_proto.gre;
56 }
57
gre_key_cmpfn(const struct nf_ct_gre_keymap * km,const struct nf_conntrack_tuple * t)58 static inline int gre_key_cmpfn(const struct nf_ct_gre_keymap *km,
59 const struct nf_conntrack_tuple *t)
60 {
61 return km->tuple.src.l3num == t->src.l3num &&
62 !memcmp(&km->tuple.src.u3, &t->src.u3, sizeof(t->src.u3)) &&
63 !memcmp(&km->tuple.dst.u3, &t->dst.u3, sizeof(t->dst.u3)) &&
64 km->tuple.dst.protonum == t->dst.protonum &&
65 km->tuple.dst.u.all == t->dst.u.all;
66 }
67
68 /* look up the source key for a given tuple */
gre_keymap_lookup(struct net * net,struct nf_conntrack_tuple * t)69 static __be16 gre_keymap_lookup(struct net *net, struct nf_conntrack_tuple *t)
70 {
71 struct nf_gre_net *net_gre = gre_pernet(net);
72 struct nf_ct_gre_keymap *km;
73 __be16 key = 0;
74
75 list_for_each_entry_rcu(km, &net_gre->keymap_list, list) {
76 if (gre_key_cmpfn(km, t)) {
77 key = km->tuple.src.u.gre.key;
78 break;
79 }
80 }
81
82 pr_debug("lookup src key 0x%x for ", key);
83 nf_ct_dump_tuple(t);
84
85 return key;
86 }
87
88 /* add a single keymap entry, associate with specified master ct */
nf_ct_gre_keymap_add(struct nf_conn * ct,enum ip_conntrack_dir dir,struct nf_conntrack_tuple * t)89 int nf_ct_gre_keymap_add(struct nf_conn *ct, enum ip_conntrack_dir dir,
90 struct nf_conntrack_tuple *t)
91 {
92 struct net *net = nf_ct_net(ct);
93 struct nf_gre_net *net_gre = gre_pernet(net);
94 struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
95 struct nf_ct_gre_keymap **kmp, *km;
96
97 kmp = &ct_pptp_info->keymap[dir];
98 if (*kmp) {
99 /* check whether it's a retransmission */
100 list_for_each_entry_rcu(km, &net_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 spin_lock_bh(&keymap_lock);
119 list_add_tail(&km->list, &net_gre->keymap_list);
120 spin_unlock_bh(&keymap_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 */
nf_ct_gre_keymap_destroy(struct nf_conn * ct)127 void nf_ct_gre_keymap_destroy(struct nf_conn *ct)
128 {
129 struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
130 enum ip_conntrack_dir dir;
131
132 pr_debug("entering for ct %p\n", ct);
133
134 spin_lock_bh(&keymap_lock);
135 for (dir = IP_CT_DIR_ORIGINAL; dir < IP_CT_DIR_MAX; dir++) {
136 if (ct_pptp_info->keymap[dir]) {
137 pr_debug("removing %p from list\n",
138 ct_pptp_info->keymap[dir]);
139 list_del_rcu(&ct_pptp_info->keymap[dir]->list);
140 kfree_rcu(ct_pptp_info->keymap[dir], rcu);
141 ct_pptp_info->keymap[dir] = NULL;
142 }
143 }
144 spin_unlock_bh(&keymap_lock);
145 }
146 EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_destroy);
147
148 /* PUBLIC CONNTRACK PROTO HELPER FUNCTIONS */
149
150 /* gre hdr info to tuple */
gre_pkt_to_tuple(const struct sk_buff * skb,unsigned int dataoff,struct net * net,struct nf_conntrack_tuple * tuple)151 bool gre_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff,
152 struct net *net, struct nf_conntrack_tuple *tuple)
153 {
154 const struct pptp_gre_header *pgrehdr;
155 struct pptp_gre_header _pgrehdr;
156 __be16 srckey;
157 const struct gre_base_hdr *grehdr;
158 struct gre_base_hdr _grehdr;
159
160 /* first only delinearize old RFC1701 GRE header */
161 grehdr = skb_header_pointer(skb, dataoff, sizeof(_grehdr), &_grehdr);
162 if (!grehdr || (grehdr->flags & GRE_VERSION) != GRE_VERSION_1) {
163 /* try to behave like "nf_conntrack_proto_generic" */
164 tuple->src.u.all = 0;
165 tuple->dst.u.all = 0;
166 return true;
167 }
168
169 /* PPTP header is variable length, only need up to the call_id field */
170 pgrehdr = skb_header_pointer(skb, dataoff, 8, &_pgrehdr);
171 if (!pgrehdr)
172 return true;
173
174 if (grehdr->protocol != GRE_PROTO_PPP) {
175 pr_debug("Unsupported GRE proto(0x%x)\n", ntohs(grehdr->protocol));
176 return false;
177 }
178
179 tuple->dst.u.gre.key = pgrehdr->call_id;
180 srckey = gre_keymap_lookup(net, tuple);
181 tuple->src.u.gre.key = srckey;
182
183 return true;
184 }
185
186 #ifdef CONFIG_NF_CONNTRACK_PROCFS
187 /* print private data for conntrack */
gre_print_conntrack(struct seq_file * s,struct nf_conn * ct)188 static void gre_print_conntrack(struct seq_file *s, struct nf_conn *ct)
189 {
190 seq_printf(s, "timeout=%u, stream_timeout=%u ",
191 (ct->proto.gre.timeout / HZ),
192 (ct->proto.gre.stream_timeout / HZ));
193 }
194 #endif
195
gre_get_timeouts(struct net * net)196 static unsigned int *gre_get_timeouts(struct net *net)
197 {
198 return gre_pernet(net)->timeouts;
199 }
200
201 /* Returns verdict for packet, and may modify conntrack */
nf_conntrack_gre_packet(struct nf_conn * ct,struct sk_buff * skb,unsigned int dataoff,enum ip_conntrack_info ctinfo,const struct nf_hook_state * state)202 int nf_conntrack_gre_packet(struct nf_conn *ct,
203 struct sk_buff *skb,
204 unsigned int dataoff,
205 enum ip_conntrack_info ctinfo,
206 const struct nf_hook_state *state)
207 {
208 if (!nf_ct_is_confirmed(ct)) {
209 unsigned int *timeouts = nf_ct_timeout_lookup(ct);
210
211 if (!timeouts)
212 timeouts = gre_get_timeouts(nf_ct_net(ct));
213
214 /* initialize to sane value. Ideally a conntrack helper
215 * (e.g. in case of pptp) is increasing them */
216 ct->proto.gre.stream_timeout = timeouts[GRE_CT_REPLIED];
217 ct->proto.gre.timeout = timeouts[GRE_CT_UNREPLIED];
218 }
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 if (!test_and_set_bit(IPS_ASSURED_BIT, &ct->status))
227 nf_conntrack_event_cache(IPCT_ASSURED, ct);
228 } else
229 nf_ct_refresh_acct(ct, ctinfo, skb,
230 ct->proto.gre.timeout);
231
232 return NF_ACCEPT;
233 }
234
235 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
236
237 #include <linux/netfilter/nfnetlink.h>
238 #include <linux/netfilter/nfnetlink_cttimeout.h>
239
gre_timeout_nlattr_to_obj(struct nlattr * tb[],struct net * net,void * data)240 static int gre_timeout_nlattr_to_obj(struct nlattr *tb[],
241 struct net *net, void *data)
242 {
243 unsigned int *timeouts = data;
244 struct nf_gre_net *net_gre = gre_pernet(net);
245
246 if (!timeouts)
247 timeouts = gre_get_timeouts(net);
248 /* set default timeouts for GRE. */
249 timeouts[GRE_CT_UNREPLIED] = net_gre->timeouts[GRE_CT_UNREPLIED];
250 timeouts[GRE_CT_REPLIED] = net_gre->timeouts[GRE_CT_REPLIED];
251
252 if (tb[CTA_TIMEOUT_GRE_UNREPLIED]) {
253 timeouts[GRE_CT_UNREPLIED] =
254 ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_UNREPLIED])) * HZ;
255 }
256 if (tb[CTA_TIMEOUT_GRE_REPLIED]) {
257 timeouts[GRE_CT_REPLIED] =
258 ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_REPLIED])) * HZ;
259 }
260 return 0;
261 }
262
263 static int
gre_timeout_obj_to_nlattr(struct sk_buff * skb,const void * data)264 gre_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
265 {
266 const unsigned int *timeouts = data;
267
268 if (nla_put_be32(skb, CTA_TIMEOUT_GRE_UNREPLIED,
269 htonl(timeouts[GRE_CT_UNREPLIED] / HZ)) ||
270 nla_put_be32(skb, CTA_TIMEOUT_GRE_REPLIED,
271 htonl(timeouts[GRE_CT_REPLIED] / HZ)))
272 goto nla_put_failure;
273 return 0;
274
275 nla_put_failure:
276 return -ENOSPC;
277 }
278
279 static const struct nla_policy
280 gre_timeout_nla_policy[CTA_TIMEOUT_GRE_MAX+1] = {
281 [CTA_TIMEOUT_GRE_UNREPLIED] = { .type = NLA_U32 },
282 [CTA_TIMEOUT_GRE_REPLIED] = { .type = NLA_U32 },
283 };
284 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
285
nf_conntrack_gre_init_net(struct net * net)286 void nf_conntrack_gre_init_net(struct net *net)
287 {
288 struct nf_gre_net *net_gre = gre_pernet(net);
289 int i;
290
291 INIT_LIST_HEAD(&net_gre->keymap_list);
292 for (i = 0; i < GRE_CT_MAX; i++)
293 net_gre->timeouts[i] = gre_timeouts[i];
294 }
295
296 /* protocol helper struct */
297 const struct nf_conntrack_l4proto nf_conntrack_l4proto_gre = {
298 .l4proto = IPPROTO_GRE,
299 #ifdef CONFIG_NF_CONNTRACK_PROCFS
300 .print_conntrack = gre_print_conntrack,
301 #endif
302 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
303 .tuple_to_nlattr = nf_ct_port_tuple_to_nlattr,
304 .nlattr_tuple_size = nf_ct_port_nlattr_tuple_size,
305 .nlattr_to_tuple = nf_ct_port_nlattr_to_tuple,
306 .nla_policy = nf_ct_port_nla_policy,
307 #endif
308 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
309 .ctnl_timeout = {
310 .nlattr_to_obj = gre_timeout_nlattr_to_obj,
311 .obj_to_nlattr = gre_timeout_obj_to_nlattr,
312 .nlattr_max = CTA_TIMEOUT_GRE_MAX,
313 .obj_size = sizeof(unsigned int) * GRE_CT_MAX,
314 .nla_policy = gre_timeout_nla_policy,
315 },
316 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
317 };
318