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/gre.h>
37 #include <net/net_namespace.h>
38 #include <net/netns/generic.h>
39 #include <net/netfilter/nf_conntrack_l4proto.h>
40 #include <net/netfilter/nf_conntrack_helper.h>
41 #include <net/netfilter/nf_conntrack_core.h>
42 #include <net/netfilter/nf_conntrack_timeout.h>
43 #include <net/pptp.h>
44 #include <linux/netfilter/nf_conntrack_proto_gre.h>
45 #include <linux/netfilter/nf_conntrack_pptp.h>
46
47 static const unsigned int gre_timeouts[GRE_CT_MAX] = {
48 [GRE_CT_UNREPLIED] = 30*HZ,
49 [GRE_CT_REPLIED] = 180*HZ,
50 };
51
52 /* used when expectation is added */
53 static DEFINE_SPINLOCK(keymap_lock);
54
gre_pernet(struct net * net)55 static inline struct nf_gre_net *gre_pernet(struct net *net)
56 {
57 return &net->ct.nf_ct_proto.gre;
58 }
59
gre_key_cmpfn(const struct nf_ct_gre_keymap * km,const struct nf_conntrack_tuple * t)60 static inline int gre_key_cmpfn(const struct nf_ct_gre_keymap *km,
61 const struct nf_conntrack_tuple *t)
62 {
63 return km->tuple.src.l3num == t->src.l3num &&
64 !memcmp(&km->tuple.src.u3, &t->src.u3, sizeof(t->src.u3)) &&
65 !memcmp(&km->tuple.dst.u3, &t->dst.u3, sizeof(t->dst.u3)) &&
66 km->tuple.dst.protonum == t->dst.protonum &&
67 km->tuple.dst.u.all == t->dst.u.all;
68 }
69
70 /* look up the source key for a given tuple */
gre_keymap_lookup(struct net * net,struct nf_conntrack_tuple * t)71 static __be16 gre_keymap_lookup(struct net *net, struct nf_conntrack_tuple *t)
72 {
73 struct nf_gre_net *net_gre = gre_pernet(net);
74 struct nf_ct_gre_keymap *km;
75 __be16 key = 0;
76
77 list_for_each_entry_rcu(km, &net_gre->keymap_list, list) {
78 if (gre_key_cmpfn(km, t)) {
79 key = km->tuple.src.u.gre.key;
80 break;
81 }
82 }
83
84 pr_debug("lookup src key 0x%x for ", key);
85 nf_ct_dump_tuple(t);
86
87 return key;
88 }
89
90 /* 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)91 int nf_ct_gre_keymap_add(struct nf_conn *ct, enum ip_conntrack_dir dir,
92 struct nf_conntrack_tuple *t)
93 {
94 struct net *net = nf_ct_net(ct);
95 struct nf_gre_net *net_gre = gre_pernet(net);
96 struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
97 struct nf_ct_gre_keymap **kmp, *km;
98
99 kmp = &ct_pptp_info->keymap[dir];
100 if (*kmp) {
101 /* check whether it's a retransmission */
102 list_for_each_entry_rcu(km, &net_gre->keymap_list, list) {
103 if (gre_key_cmpfn(km, t) && km == *kmp)
104 return 0;
105 }
106 pr_debug("trying to override keymap_%s for ct %p\n",
107 dir == IP_CT_DIR_REPLY ? "reply" : "orig", ct);
108 return -EEXIST;
109 }
110
111 km = kmalloc_obj(*km, GFP_ATOMIC);
112 if (!km)
113 return -ENOMEM;
114 memcpy(&km->tuple, t, sizeof(*t));
115 *kmp = km;
116
117 pr_debug("adding new entry %p: ", km);
118 nf_ct_dump_tuple(&km->tuple);
119
120 spin_lock_bh(&keymap_lock);
121 list_add_tail(&km->list, &net_gre->keymap_list);
122 spin_unlock_bh(&keymap_lock);
123
124 return 0;
125 }
126 EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_add);
127
128 /* destroy the keymap entries associated with specified master ct */
nf_ct_gre_keymap_destroy(struct nf_conn * ct)129 void nf_ct_gre_keymap_destroy(struct nf_conn *ct)
130 {
131 struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
132 enum ip_conntrack_dir dir;
133
134 pr_debug("entering for ct %p\n", ct);
135
136 spin_lock_bh(&keymap_lock);
137 for (dir = IP_CT_DIR_ORIGINAL; dir < IP_CT_DIR_MAX; dir++) {
138 if (ct_pptp_info->keymap[dir]) {
139 pr_debug("removing %p from list\n",
140 ct_pptp_info->keymap[dir]);
141 list_del_rcu(&ct_pptp_info->keymap[dir]->list);
142 kfree_rcu(ct_pptp_info->keymap[dir], rcu);
143 ct_pptp_info->keymap[dir] = NULL;
144 }
145 }
146 spin_unlock_bh(&keymap_lock);
147 }
148 EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_destroy);
149
150 /* PUBLIC CONNTRACK PROTO HELPER FUNCTIONS */
151
152 /* 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)153 bool gre_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff,
154 struct net *net, struct nf_conntrack_tuple *tuple)
155 {
156 const struct pptp_gre_header *pgrehdr;
157 struct pptp_gre_header _pgrehdr;
158 __be16 srckey;
159 const struct gre_base_hdr *grehdr;
160 struct gre_base_hdr _grehdr;
161
162 /* first only delinearize old RFC1701 GRE header */
163 grehdr = skb_header_pointer(skb, dataoff, sizeof(_grehdr), &_grehdr);
164 if (!grehdr || (grehdr->flags & GRE_VERSION) != GRE_VERSION_1) {
165 /* try to behave like "nf_conntrack_proto_generic" */
166 tuple->src.u.all = 0;
167 tuple->dst.u.all = 0;
168 return true;
169 }
170
171 /* PPTP header is variable length, only need up to the call_id field */
172 pgrehdr = skb_header_pointer(skb, dataoff, 8, &_pgrehdr);
173 if (!pgrehdr)
174 return true;
175
176 if (grehdr->protocol != GRE_PROTO_PPP) {
177 pr_debug("Unsupported GRE proto(0x%x)\n", ntohs(grehdr->protocol));
178 return false;
179 }
180
181 tuple->dst.u.gre.key = pgrehdr->call_id;
182 srckey = gre_keymap_lookup(net, tuple);
183 tuple->src.u.gre.key = srckey;
184
185 return true;
186 }
187
188 #ifdef CONFIG_NF_CONNTRACK_PROCFS
189 /* print private data for conntrack */
gre_print_conntrack(struct seq_file * s,struct nf_conn * ct)190 static void gre_print_conntrack(struct seq_file *s, struct nf_conn *ct)
191 {
192 seq_printf(s, "timeout=%u, stream_timeout=%u ",
193 (ct->proto.gre.timeout / HZ),
194 (ct->proto.gre.stream_timeout / HZ));
195 }
196 #endif
197
gre_get_timeouts(struct net * net)198 static unsigned int *gre_get_timeouts(struct net *net)
199 {
200 return gre_pernet(net)->timeouts;
201 }
202
203 /* 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)204 int nf_conntrack_gre_packet(struct nf_conn *ct,
205 struct sk_buff *skb,
206 unsigned int dataoff,
207 enum ip_conntrack_info ctinfo,
208 const struct nf_hook_state *state)
209 {
210 unsigned long status;
211
212 if (!nf_ct_is_confirmed(ct)) {
213 unsigned int *timeouts = nf_ct_timeout_lookup(ct);
214
215 if (!timeouts)
216 timeouts = gre_get_timeouts(nf_ct_net(ct));
217
218 /* initialize to sane value. Ideally a conntrack helper
219 * (e.g. in case of pptp) is increasing them */
220 ct->proto.gre.stream_timeout = timeouts[GRE_CT_REPLIED];
221 ct->proto.gre.timeout = timeouts[GRE_CT_UNREPLIED];
222 }
223
224 status = READ_ONCE(ct->status);
225 /* If we've seen traffic both ways, this is a GRE connection.
226 * Extend timeout. */
227 if (status & IPS_SEEN_REPLY) {
228 nf_ct_refresh_acct(ct, ctinfo, skb,
229 ct->proto.gre.stream_timeout);
230
231 /* never set ASSURED for IPS_NAT_CLASH, they time out soon */
232 if (unlikely((status & IPS_NAT_CLASH)))
233 return NF_ACCEPT;
234
235 /* Also, more likely to be important, and not a probe. */
236 if (!test_and_set_bit(IPS_ASSURED_BIT, &ct->status))
237 nf_conntrack_event_cache(IPCT_ASSURED, ct);
238 } else
239 nf_ct_refresh_acct(ct, ctinfo, skb,
240 ct->proto.gre.timeout);
241
242 return NF_ACCEPT;
243 }
244
245 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
246
247 #include <linux/netfilter/nfnetlink.h>
248 #include <linux/netfilter/nfnetlink_cttimeout.h>
249
gre_timeout_nlattr_to_obj(struct nlattr * tb[],struct net * net,void * data)250 static int gre_timeout_nlattr_to_obj(struct nlattr *tb[],
251 struct net *net, void *data)
252 {
253 unsigned int *timeouts = data;
254 struct nf_gre_net *net_gre = gre_pernet(net);
255
256 if (!timeouts)
257 timeouts = gre_get_timeouts(net);
258 /* set default timeouts for GRE. */
259 timeouts[GRE_CT_UNREPLIED] = net_gre->timeouts[GRE_CT_UNREPLIED];
260 timeouts[GRE_CT_REPLIED] = net_gre->timeouts[GRE_CT_REPLIED];
261
262 if (tb[CTA_TIMEOUT_GRE_UNREPLIED]) {
263 timeouts[GRE_CT_UNREPLIED] =
264 ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_UNREPLIED])) * HZ;
265 }
266 if (tb[CTA_TIMEOUT_GRE_REPLIED]) {
267 timeouts[GRE_CT_REPLIED] =
268 ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_REPLIED])) * HZ;
269 }
270 return 0;
271 }
272
273 static int
gre_timeout_obj_to_nlattr(struct sk_buff * skb,const void * data)274 gre_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
275 {
276 const unsigned int *timeouts = data;
277
278 if (nla_put_be32(skb, CTA_TIMEOUT_GRE_UNREPLIED,
279 htonl(timeouts[GRE_CT_UNREPLIED] / HZ)) ||
280 nla_put_be32(skb, CTA_TIMEOUT_GRE_REPLIED,
281 htonl(timeouts[GRE_CT_REPLIED] / HZ)))
282 goto nla_put_failure;
283 return 0;
284
285 nla_put_failure:
286 return -ENOSPC;
287 }
288
289 static const struct nla_policy
290 gre_timeout_nla_policy[CTA_TIMEOUT_GRE_MAX+1] = {
291 [CTA_TIMEOUT_GRE_UNREPLIED] = { .type = NLA_U32 },
292 [CTA_TIMEOUT_GRE_REPLIED] = { .type = NLA_U32 },
293 };
294 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
295
nf_conntrack_gre_init_net(struct net * net)296 void nf_conntrack_gre_init_net(struct net *net)
297 {
298 struct nf_gre_net *net_gre = gre_pernet(net);
299 int i;
300
301 INIT_LIST_HEAD(&net_gre->keymap_list);
302 for (i = 0; i < GRE_CT_MAX; i++)
303 net_gre->timeouts[i] = gre_timeouts[i];
304 }
305
306 /* protocol helper struct */
307 const struct nf_conntrack_l4proto nf_conntrack_l4proto_gre = {
308 .l4proto = IPPROTO_GRE,
309 .allow_clash = true,
310 #ifdef CONFIG_NF_CONNTRACK_PROCFS
311 .print_conntrack = gre_print_conntrack,
312 #endif
313 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
314 .tuple_to_nlattr = nf_ct_port_tuple_to_nlattr,
315 .nlattr_tuple_size = nf_ct_port_nlattr_tuple_size,
316 .nlattr_to_tuple = nf_ct_port_nlattr_to_tuple,
317 .nla_policy = nf_ct_port_nla_policy,
318 #endif
319 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
320 .ctnl_timeout = {
321 .nlattr_to_obj = gre_timeout_nlattr_to_obj,
322 .obj_to_nlattr = gre_timeout_obj_to_nlattr,
323 .nlattr_max = CTA_TIMEOUT_GRE_MAX,
324 .obj_size = sizeof(unsigned int) * GRE_CT_MAX,
325 .nla_policy = gre_timeout_nla_policy,
326 },
327 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
328 };
329