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 | |
53 | static inline struct nf_gre_net *gre_pernet(struct net *net) |
54 | { |
55 | return &net->ct.nf_ct_proto.gre; |
56 | } |
57 | |
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(p: &km->tuple.src.u3, q: &t->src.u3, size: sizeof(t->src.u3)) && |
63 | !memcmp(p: &km->tuple.dst.u3, q: &t->dst.u3, size: 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 */ |
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 */ |
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(size: 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(t: &km->tuple); |
117 | |
118 | spin_lock_bh(lock: &keymap_lock); |
119 | list_add_tail(new: &km->list, head: &net_gre->keymap_list); |
120 | spin_unlock_bh(lock: &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 */ |
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(lock: &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(entry: &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(lock: &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 */ |
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, offset: dataoff, len: sizeof(_grehdr), buffer: &_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, offset: dataoff, len: 8, buffer: &_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, t: 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 */ |
188 | static void gre_print_conntrack(struct seq_file *s, struct nf_conn *ct) |
189 | { |
190 | seq_printf(m: s, fmt: "timeout=%u, stream_timeout=%u " , |
191 | (ct->proto.gre.timeout / HZ), |
192 | (ct->proto.gre.stream_timeout / HZ)); |
193 | } |
194 | #endif |
195 | |
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 */ |
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 | unsigned long status; |
209 | |
210 | if (!nf_ct_is_confirmed(ct)) { |
211 | unsigned int *timeouts = nf_ct_timeout_lookup(ct); |
212 | |
213 | if (!timeouts) |
214 | timeouts = gre_get_timeouts(net: nf_ct_net(ct)); |
215 | |
216 | /* initialize to sane value. Ideally a conntrack helper |
217 | * (e.g. in case of pptp) is increasing them */ |
218 | ct->proto.gre.stream_timeout = timeouts[GRE_CT_REPLIED]; |
219 | ct->proto.gre.timeout = timeouts[GRE_CT_UNREPLIED]; |
220 | } |
221 | |
222 | status = READ_ONCE(ct->status); |
223 | /* If we've seen traffic both ways, this is a GRE connection. |
224 | * Extend timeout. */ |
225 | if (status & IPS_SEEN_REPLY) { |
226 | nf_ct_refresh_acct(ct, ctinfo, skb, |
227 | extra_jiffies: ct->proto.gre.stream_timeout); |
228 | |
229 | /* never set ASSURED for IPS_NAT_CLASH, they time out soon */ |
230 | if (unlikely((status & IPS_NAT_CLASH))) |
231 | return NF_ACCEPT; |
232 | |
233 | /* Also, more likely to be important, and not a probe. */ |
234 | if (!test_and_set_bit(nr: IPS_ASSURED_BIT, addr: &ct->status)) |
235 | nf_conntrack_event_cache(event: IPCT_ASSURED, ct); |
236 | } else |
237 | nf_ct_refresh_acct(ct, ctinfo, skb, |
238 | extra_jiffies: ct->proto.gre.timeout); |
239 | |
240 | return NF_ACCEPT; |
241 | } |
242 | |
243 | #ifdef CONFIG_NF_CONNTRACK_TIMEOUT |
244 | |
245 | #include <linux/netfilter/nfnetlink.h> |
246 | #include <linux/netfilter/nfnetlink_cttimeout.h> |
247 | |
248 | static int gre_timeout_nlattr_to_obj(struct nlattr *tb[], |
249 | struct net *net, void *data) |
250 | { |
251 | unsigned int *timeouts = data; |
252 | struct nf_gre_net *net_gre = gre_pernet(net); |
253 | |
254 | if (!timeouts) |
255 | timeouts = gre_get_timeouts(net); |
256 | /* set default timeouts for GRE. */ |
257 | timeouts[GRE_CT_UNREPLIED] = net_gre->timeouts[GRE_CT_UNREPLIED]; |
258 | timeouts[GRE_CT_REPLIED] = net_gre->timeouts[GRE_CT_REPLIED]; |
259 | |
260 | if (tb[CTA_TIMEOUT_GRE_UNREPLIED]) { |
261 | timeouts[GRE_CT_UNREPLIED] = |
262 | ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_UNREPLIED])) * HZ; |
263 | } |
264 | if (tb[CTA_TIMEOUT_GRE_REPLIED]) { |
265 | timeouts[GRE_CT_REPLIED] = |
266 | ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_REPLIED])) * HZ; |
267 | } |
268 | return 0; |
269 | } |
270 | |
271 | static int |
272 | gre_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data) |
273 | { |
274 | const unsigned int *timeouts = data; |
275 | |
276 | if (nla_put_be32(skb, attrtype: CTA_TIMEOUT_GRE_UNREPLIED, |
277 | htonl(timeouts[GRE_CT_UNREPLIED] / HZ)) || |
278 | nla_put_be32(skb, attrtype: CTA_TIMEOUT_GRE_REPLIED, |
279 | htonl(timeouts[GRE_CT_REPLIED] / HZ))) |
280 | goto nla_put_failure; |
281 | return 0; |
282 | |
283 | nla_put_failure: |
284 | return -ENOSPC; |
285 | } |
286 | |
287 | static const struct nla_policy |
288 | gre_timeout_nla_policy[CTA_TIMEOUT_GRE_MAX+1] = { |
289 | [CTA_TIMEOUT_GRE_UNREPLIED] = { .type = NLA_U32 }, |
290 | [CTA_TIMEOUT_GRE_REPLIED] = { .type = NLA_U32 }, |
291 | }; |
292 | #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */ |
293 | |
294 | void nf_conntrack_gre_init_net(struct net *net) |
295 | { |
296 | struct nf_gre_net *net_gre = gre_pernet(net); |
297 | int i; |
298 | |
299 | INIT_LIST_HEAD(list: &net_gre->keymap_list); |
300 | for (i = 0; i < GRE_CT_MAX; i++) |
301 | net_gre->timeouts[i] = gre_timeouts[i]; |
302 | } |
303 | |
304 | /* protocol helper struct */ |
305 | const struct nf_conntrack_l4proto nf_conntrack_l4proto_gre = { |
306 | .l4proto = IPPROTO_GRE, |
307 | .allow_clash = true, |
308 | #ifdef CONFIG_NF_CONNTRACK_PROCFS |
309 | .print_conntrack = gre_print_conntrack, |
310 | #endif |
311 | #if IS_ENABLED(CONFIG_NF_CT_NETLINK) |
312 | .tuple_to_nlattr = nf_ct_port_tuple_to_nlattr, |
313 | .nlattr_tuple_size = nf_ct_port_nlattr_tuple_size, |
314 | .nlattr_to_tuple = nf_ct_port_nlattr_to_tuple, |
315 | .nla_policy = nf_ct_port_nla_policy, |
316 | #endif |
317 | #ifdef CONFIG_NF_CONNTRACK_TIMEOUT |
318 | .ctnl_timeout = { |
319 | .nlattr_to_obj = gre_timeout_nlattr_to_obj, |
320 | .obj_to_nlattr = gre_timeout_obj_to_nlattr, |
321 | .nlattr_max = CTA_TIMEOUT_GRE_MAX, |
322 | .obj_size = sizeof(unsigned int) * GRE_CT_MAX, |
323 | .nla_policy = gre_timeout_nla_policy, |
324 | }, |
325 | #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */ |
326 | }; |
327 | |