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
nf_ct_gre_keymap_flush(struct net * net)58 void nf_ct_gre_keymap_flush(struct net *net)
59 {
60 struct nf_gre_net *net_gre = gre_pernet(net);
61 struct nf_ct_gre_keymap *km, *tmp;
62
63 spin_lock_bh(&keymap_lock);
64 list_for_each_entry_safe(km, tmp, &net_gre->keymap_list, list) {
65 list_del_rcu(&km->list);
66 kfree_rcu(km, rcu);
67 }
68 spin_unlock_bh(&keymap_lock);
69 }
70
gre_key_cmpfn(const struct nf_ct_gre_keymap * km,const struct nf_conntrack_tuple * t)71 static inline int gre_key_cmpfn(const struct nf_ct_gre_keymap *km,
72 const struct nf_conntrack_tuple *t)
73 {
74 return km->tuple.src.l3num == t->src.l3num &&
75 !memcmp(&km->tuple.src.u3, &t->src.u3, sizeof(t->src.u3)) &&
76 !memcmp(&km->tuple.dst.u3, &t->dst.u3, sizeof(t->dst.u3)) &&
77 km->tuple.dst.protonum == t->dst.protonum &&
78 km->tuple.dst.u.all == t->dst.u.all;
79 }
80
81 /* look up the source key for a given tuple */
gre_keymap_lookup(struct net * net,struct nf_conntrack_tuple * t)82 static __be16 gre_keymap_lookup(struct net *net, struct nf_conntrack_tuple *t)
83 {
84 struct nf_gre_net *net_gre = gre_pernet(net);
85 struct nf_ct_gre_keymap *km;
86 __be16 key = 0;
87
88 list_for_each_entry_rcu(km, &net_gre->keymap_list, list) {
89 if (gre_key_cmpfn(km, t)) {
90 key = km->tuple.src.u.gre.key;
91 break;
92 }
93 }
94
95 pr_debug("lookup src key 0x%x for ", key);
96 nf_ct_dump_tuple(t);
97
98 return key;
99 }
100
101 /* 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)102 int nf_ct_gre_keymap_add(struct nf_conn *ct, enum ip_conntrack_dir dir,
103 struct nf_conntrack_tuple *t)
104 {
105 struct net *net = nf_ct_net(ct);
106 struct nf_gre_net *net_gre = gre_pernet(net);
107 struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
108 struct nf_ct_gre_keymap **kmp, *km;
109
110 kmp = &ct_pptp_info->keymap[dir];
111 if (*kmp) {
112 /* check whether it's a retransmission */
113 list_for_each_entry_rcu(km, &net_gre->keymap_list, list) {
114 if (gre_key_cmpfn(km, t) && km == *kmp)
115 return 0;
116 }
117 pr_debug("trying to override keymap_%s for ct %p\n",
118 dir == IP_CT_DIR_REPLY ? "reply" : "orig", ct);
119 return -EEXIST;
120 }
121
122 km = kmalloc(sizeof(*km), GFP_ATOMIC);
123 if (!km)
124 return -ENOMEM;
125 memcpy(&km->tuple, t, sizeof(*t));
126 *kmp = km;
127
128 pr_debug("adding new entry %p: ", km);
129 nf_ct_dump_tuple(&km->tuple);
130
131 spin_lock_bh(&keymap_lock);
132 list_add_tail(&km->list, &net_gre->keymap_list);
133 spin_unlock_bh(&keymap_lock);
134
135 return 0;
136 }
137 EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_add);
138
139 /* destroy the keymap entries associated with specified master ct */
nf_ct_gre_keymap_destroy(struct nf_conn * ct)140 void nf_ct_gre_keymap_destroy(struct nf_conn *ct)
141 {
142 struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
143 enum ip_conntrack_dir dir;
144
145 pr_debug("entering for ct %p\n", ct);
146
147 spin_lock_bh(&keymap_lock);
148 for (dir = IP_CT_DIR_ORIGINAL; dir < IP_CT_DIR_MAX; dir++) {
149 if (ct_pptp_info->keymap[dir]) {
150 pr_debug("removing %p from list\n",
151 ct_pptp_info->keymap[dir]);
152 list_del_rcu(&ct_pptp_info->keymap[dir]->list);
153 kfree_rcu(ct_pptp_info->keymap[dir], rcu);
154 ct_pptp_info->keymap[dir] = NULL;
155 }
156 }
157 spin_unlock_bh(&keymap_lock);
158 }
159 EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_destroy);
160
161 /* PUBLIC CONNTRACK PROTO HELPER FUNCTIONS */
162
163 /* 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)164 bool gre_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff,
165 struct net *net, struct nf_conntrack_tuple *tuple)
166 {
167 const struct pptp_gre_header *pgrehdr;
168 struct pptp_gre_header _pgrehdr;
169 __be16 srckey;
170 const struct gre_base_hdr *grehdr;
171 struct gre_base_hdr _grehdr;
172
173 /* first only delinearize old RFC1701 GRE header */
174 grehdr = skb_header_pointer(skb, dataoff, sizeof(_grehdr), &_grehdr);
175 if (!grehdr || (grehdr->flags & GRE_VERSION) != GRE_VERSION_1) {
176 /* try to behave like "nf_conntrack_proto_generic" */
177 tuple->src.u.all = 0;
178 tuple->dst.u.all = 0;
179 return true;
180 }
181
182 /* PPTP header is variable length, only need up to the call_id field */
183 pgrehdr = skb_header_pointer(skb, dataoff, 8, &_pgrehdr);
184 if (!pgrehdr)
185 return true;
186
187 if (grehdr->protocol != GRE_PROTO_PPP) {
188 pr_debug("Unsupported GRE proto(0x%x)\n", ntohs(grehdr->protocol));
189 return false;
190 }
191
192 tuple->dst.u.gre.key = pgrehdr->call_id;
193 srckey = gre_keymap_lookup(net, tuple);
194 tuple->src.u.gre.key = srckey;
195
196 return true;
197 }
198
199 #ifdef CONFIG_NF_CONNTRACK_PROCFS
200 /* print private data for conntrack */
gre_print_conntrack(struct seq_file * s,struct nf_conn * ct)201 static void gre_print_conntrack(struct seq_file *s, struct nf_conn *ct)
202 {
203 seq_printf(s, "timeout=%u, stream_timeout=%u ",
204 (ct->proto.gre.timeout / HZ),
205 (ct->proto.gre.stream_timeout / HZ));
206 }
207 #endif
208
gre_get_timeouts(struct net * net)209 static unsigned int *gre_get_timeouts(struct net *net)
210 {
211 return gre_pernet(net)->timeouts;
212 }
213
214 /* 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)215 int nf_conntrack_gre_packet(struct nf_conn *ct,
216 struct sk_buff *skb,
217 unsigned int dataoff,
218 enum ip_conntrack_info ctinfo,
219 const struct nf_hook_state *state)
220 {
221 if (state->pf != NFPROTO_IPV4)
222 return -NF_ACCEPT;
223
224 if (!nf_ct_is_confirmed(ct)) {
225 unsigned int *timeouts = nf_ct_timeout_lookup(ct);
226
227 if (!timeouts)
228 timeouts = gre_get_timeouts(nf_ct_net(ct));
229
230 /* initialize to sane value. Ideally a conntrack helper
231 * (e.g. in case of pptp) is increasing them */
232 ct->proto.gre.stream_timeout = timeouts[GRE_CT_REPLIED];
233 ct->proto.gre.timeout = timeouts[GRE_CT_UNREPLIED];
234 }
235
236 /* If we've seen traffic both ways, this is a GRE connection.
237 * Extend timeout. */
238 if (ct->status & IPS_SEEN_REPLY) {
239 nf_ct_refresh_acct(ct, ctinfo, skb,
240 ct->proto.gre.stream_timeout);
241 /* Also, more likely to be important, and not a probe. */
242 if (!test_and_set_bit(IPS_ASSURED_BIT, &ct->status))
243 nf_conntrack_event_cache(IPCT_ASSURED, ct);
244 } else
245 nf_ct_refresh_acct(ct, ctinfo, skb,
246 ct->proto.gre.timeout);
247
248 return NF_ACCEPT;
249 }
250
251 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
252
253 #include <linux/netfilter/nfnetlink.h>
254 #include <linux/netfilter/nfnetlink_cttimeout.h>
255
gre_timeout_nlattr_to_obj(struct nlattr * tb[],struct net * net,void * data)256 static int gre_timeout_nlattr_to_obj(struct nlattr *tb[],
257 struct net *net, void *data)
258 {
259 unsigned int *timeouts = data;
260 struct nf_gre_net *net_gre = gre_pernet(net);
261
262 if (!timeouts)
263 timeouts = gre_get_timeouts(net);
264 /* set default timeouts for GRE. */
265 timeouts[GRE_CT_UNREPLIED] = net_gre->timeouts[GRE_CT_UNREPLIED];
266 timeouts[GRE_CT_REPLIED] = net_gre->timeouts[GRE_CT_REPLIED];
267
268 if (tb[CTA_TIMEOUT_GRE_UNREPLIED]) {
269 timeouts[GRE_CT_UNREPLIED] =
270 ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_UNREPLIED])) * HZ;
271 }
272 if (tb[CTA_TIMEOUT_GRE_REPLIED]) {
273 timeouts[GRE_CT_REPLIED] =
274 ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_REPLIED])) * HZ;
275 }
276 return 0;
277 }
278
279 static int
gre_timeout_obj_to_nlattr(struct sk_buff * skb,const void * data)280 gre_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
281 {
282 const unsigned int *timeouts = data;
283
284 if (nla_put_be32(skb, CTA_TIMEOUT_GRE_UNREPLIED,
285 htonl(timeouts[GRE_CT_UNREPLIED] / HZ)) ||
286 nla_put_be32(skb, CTA_TIMEOUT_GRE_REPLIED,
287 htonl(timeouts[GRE_CT_REPLIED] / HZ)))
288 goto nla_put_failure;
289 return 0;
290
291 nla_put_failure:
292 return -ENOSPC;
293 }
294
295 static const struct nla_policy
296 gre_timeout_nla_policy[CTA_TIMEOUT_GRE_MAX+1] = {
297 [CTA_TIMEOUT_GRE_UNREPLIED] = { .type = NLA_U32 },
298 [CTA_TIMEOUT_GRE_REPLIED] = { .type = NLA_U32 },
299 };
300 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
301
nf_conntrack_gre_init_net(struct net * net)302 void nf_conntrack_gre_init_net(struct net *net)
303 {
304 struct nf_gre_net *net_gre = gre_pernet(net);
305 int i;
306
307 INIT_LIST_HEAD(&net_gre->keymap_list);
308 for (i = 0; i < GRE_CT_MAX; i++)
309 net_gre->timeouts[i] = gre_timeouts[i];
310 }
311
312 /* protocol helper struct */
313 const struct nf_conntrack_l4proto nf_conntrack_l4proto_gre = {
314 .l4proto = IPPROTO_GRE,
315 #ifdef CONFIG_NF_CONNTRACK_PROCFS
316 .print_conntrack = gre_print_conntrack,
317 #endif
318 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
319 .tuple_to_nlattr = nf_ct_port_tuple_to_nlattr,
320 .nlattr_tuple_size = nf_ct_port_nlattr_tuple_size,
321 .nlattr_to_tuple = nf_ct_port_nlattr_to_tuple,
322 .nla_policy = nf_ct_port_nla_policy,
323 #endif
324 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
325 .ctnl_timeout = {
326 .nlattr_to_obj = gre_timeout_nlattr_to_obj,
327 .obj_to_nlattr = gre_timeout_obj_to_nlattr,
328 .nlattr_max = CTA_TIMEOUT_GRE_MAX,
329 .obj_size = sizeof(unsigned int) * GRE_CT_MAX,
330 .nla_policy = gre_timeout_nla_policy,
331 },
332 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
333 };
334