xref: /linux/net/ipv4/fib_rules.c (revision 908fc4c2) 
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * INET		An implementation of the TCP/IP protocol suite for the LINUX
4  *		operating system.  INET is implemented using the  BSD Socket
5  *		interface as the means of communication with the user level.
6  *
7  *		IPv4 Forwarding Information Base: policy rules.
8  *
9  * Authors:	Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
10  *		Thomas Graf <tgraf@suug.ch>
11  *
12  * Fixes:
13  *		Rani Assaf	:	local_rule cannot be deleted
14  *		Marc Boucher	:	routing by fwmark
15  */
16 
17 #include <linux/types.h>
18 #include <linux/kernel.h>
19 #include <linux/netdevice.h>
20 #include <linux/netlink.h>
21 #include <linux/inetdevice.h>
22 #include <linux/init.h>
23 #include <linux/list.h>
24 #include <linux/rcupdate.h>
25 #include <linux/export.h>
26 #include <net/inet_dscp.h>
27 #include <net/ip.h>
28 #include <net/route.h>
29 #include <net/tcp.h>
30 #include <net/ip_fib.h>
31 #include <net/nexthop.h>
32 #include <net/fib_rules.h>
33 #include <linux/indirect_call_wrapper.h>
34 
35 struct fib4_rule {
36 	struct fib_rule		common;
37 	u8			dst_len;
38 	u8			src_len;
39 	dscp_t			dscp;
40 	__be32			src;
41 	__be32			srcmask;
42 	__be32			dst;
43 	__be32			dstmask;
44 #ifdef CONFIG_IP_ROUTE_CLASSID
45 	u32			tclassid;
46 #endif
47 };
48 
49 static bool fib4_rule_matchall(const struct fib_rule *rule)
50 {
51 	struct fib4_rule *r = container_of(rule, struct fib4_rule, common);
52 
53 	if (r->dst_len || r->src_len || r->dscp)
54 		return false;
55 	return fib_rule_matchall(rule);
56 }
57 
58 bool fib4_rule_default(const struct fib_rule *rule)
59 {
60 	if (!fib4_rule_matchall(rule) || rule->action != FR_ACT_TO_TBL ||
61 	    rule->l3mdev)
62 		return false;
63 	if (rule->table != RT_TABLE_LOCAL && rule->table != RT_TABLE_MAIN &&
64 	    rule->table != RT_TABLE_DEFAULT)
65 		return false;
66 	return true;
67 }
68 EXPORT_SYMBOL_GPL(fib4_rule_default);
69 
70 int fib4_rules_dump(struct net *net, struct notifier_block *nb,
71 		    struct netlink_ext_ack *extack)
72 {
73 	return fib_rules_dump(net, nb, AF_INET, extack);
74 }
75 
76 unsigned int fib4_rules_seq_read(struct net *net)
77 {
78 	return fib_rules_seq_read(net, AF_INET);
79 }
80 
81 int __fib_lookup(struct net *net, struct flowi4 *flp,
82 		 struct fib_result *res, unsigned int flags)
83 {
84 	struct fib_lookup_arg arg = {
85 		.result = res,
86 		.flags = flags,
87 	};
88 	int err;
89 
90 	/* update flow if oif or iif point to device enslaved to l3mdev */
91 	l3mdev_update_flow(net, flowi4_to_flowi(flp));
92 
93 	err = fib_rules_lookup(net->ipv4.rules_ops, flowi4_to_flowi(flp), 0, &arg);
94 #ifdef CONFIG_IP_ROUTE_CLASSID
95 	if (arg.rule)
96 		res->tclassid = ((struct fib4_rule *)arg.rule)->tclassid;
97 	else
98 		res->tclassid = 0;
99 #endif
100 
101 	if (err == -ESRCH)
102 		err = -ENETUNREACH;
103 
104 	return err;
105 }
106 EXPORT_SYMBOL_GPL(__fib_lookup);
107 
108 INDIRECT_CALLABLE_SCOPE int fib4_rule_action(struct fib_rule *rule,
109 					     struct flowi *flp, int flags,
110 					     struct fib_lookup_arg *arg)
111 {
112 	int err = -EAGAIN;
113 	struct fib_table *tbl;
114 	u32 tb_id;
115 
116 	switch (rule->action) {
117 	case FR_ACT_TO_TBL:
118 		break;
119 
120 	case FR_ACT_UNREACHABLE:
121 		return -ENETUNREACH;
122 
123 	case FR_ACT_PROHIBIT:
124 		return -EACCES;
125 
126 	case FR_ACT_BLACKHOLE:
127 	default:
128 		return -EINVAL;
129 	}
130 
131 	rcu_read_lock();
132 
133 	tb_id = fib_rule_get_table(rule, arg);
134 	tbl = fib_get_table(rule->fr_net, tb_id);
135 	if (tbl)
136 		err = fib_table_lookup(tbl, &flp->u.ip4,
137 				       (struct fib_result *)arg->result,
138 				       arg->flags);
139 
140 	rcu_read_unlock();
141 	return err;
142 }
143 
144 INDIRECT_CALLABLE_SCOPE bool fib4_rule_suppress(struct fib_rule *rule,
145 						int flags,
146 						struct fib_lookup_arg *arg)
147 {
148 	struct fib_result *result = arg->result;
149 	struct net_device *dev = NULL;
150 
151 	if (result->fi) {
152 		struct fib_nh_common *nhc = fib_info_nhc(result->fi, 0);
153 
154 		dev = nhc->nhc_dev;
155 	}
156 
157 	/* do not accept result if the route does
158 	 * not meet the required prefix length
159 	 */
160 	if (result->prefixlen <= rule->suppress_prefixlen)
161 		goto suppress_route;
162 
163 	/* do not accept result if the route uses a device
164 	 * belonging to a forbidden interface group
165 	 */
166 	if (rule->suppress_ifgroup != -1 && dev && dev->group == rule->suppress_ifgroup)
167 		goto suppress_route;
168 
169 	return false;
170 
171 suppress_route:
172 	if (!(arg->flags & FIB_LOOKUP_NOREF))
173 		fib_info_put(result->fi);
174 	return true;
175 }
176 
177 INDIRECT_CALLABLE_SCOPE int fib4_rule_match(struct fib_rule *rule,
178 					    struct flowi *fl, int flags)
179 {
180 	struct fib4_rule *r = (struct fib4_rule *) rule;
181 	struct flowi4 *fl4 = &fl->u.ip4;
182 	__be32 daddr = fl4->daddr;
183 	__be32 saddr = fl4->saddr;
184 
185 	if (((saddr ^ r->src) & r->srcmask) ||
186 	    ((daddr ^ r->dst) & r->dstmask))
187 		return 0;
188 
189 	if (r->dscp && r->dscp != inet_dsfield_to_dscp(fl4->flowi4_tos))
190 		return 0;
191 
192 	if (rule->ip_proto && (rule->ip_proto != fl4->flowi4_proto))
193 		return 0;
194 
195 	if (fib_rule_port_range_set(&rule->sport_range) &&
196 	    !fib_rule_port_inrange(&rule->sport_range, fl4->fl4_sport))
197 		return 0;
198 
199 	if (fib_rule_port_range_set(&rule->dport_range) &&
200 	    !fib_rule_port_inrange(&rule->dport_range, fl4->fl4_dport))
201 		return 0;
202 
203 	return 1;
204 }
205 
206 static struct fib_table *fib_empty_table(struct net *net)
207 {
208 	u32 id = 1;
209 
210 	while (1) {
211 		if (!fib_get_table(net, id))
212 			return fib_new_table(net, id);
213 
214 		if (id++ == RT_TABLE_MAX)
215 			break;
216 	}
217 	return NULL;
218 }
219 
220 static int fib4_rule_configure(struct fib_rule *rule, struct sk_buff *skb,
221 			       struct fib_rule_hdr *frh,
222 			       struct nlattr **tb,
223 			       struct netlink_ext_ack *extack)
224 {
225 	struct net *net = sock_net(skb->sk);
226 	int err = -EINVAL;
227 	struct fib4_rule *rule4 = (struct fib4_rule *) rule;
228 
229 	if (!inet_validate_dscp(frh->tos)) {
230 		NL_SET_ERR_MSG(extack,
231 			       "Invalid dsfield (tos): ECN bits must be 0");
232 		goto errout;
233 	}
234 	/* IPv4 currently doesn't handle high order DSCP bits correctly */
235 	if (frh->tos & ~IPTOS_TOS_MASK) {
236 		NL_SET_ERR_MSG(extack, "Invalid tos");
237 		goto errout;
238 	}
239 	rule4->dscp = inet_dsfield_to_dscp(frh->tos);
240 
241 	/* split local/main if they are not already split */
242 	err = fib_unmerge(net);
243 	if (err)
244 		goto errout;
245 
246 	if (rule->table == RT_TABLE_UNSPEC && !rule->l3mdev) {
247 		if (rule->action == FR_ACT_TO_TBL) {
248 			struct fib_table *table;
249 
250 			table = fib_empty_table(net);
251 			if (!table) {
252 				err = -ENOBUFS;
253 				goto errout;
254 			}
255 
256 			rule->table = table->tb_id;
257 		}
258 	}
259 
260 	if (frh->src_len)
261 		rule4->src = nla_get_in_addr(tb[FRA_SRC]);
262 
263 	if (frh->dst_len)
264 		rule4->dst = nla_get_in_addr(tb[FRA_DST]);
265 
266 #ifdef CONFIG_IP_ROUTE_CLASSID
267 	if (tb[FRA_FLOW]) {
268 		rule4->tclassid = nla_get_u32(tb[FRA_FLOW]);
269 		if (rule4->tclassid)
270 			atomic_inc(&net->ipv4.fib_num_tclassid_users);
271 	}
272 #endif
273 
274 	if (fib_rule_requires_fldissect(rule))
275 		net->ipv4.fib_rules_require_fldissect++;
276 
277 	rule4->src_len = frh->src_len;
278 	rule4->srcmask = inet_make_mask(rule4->src_len);
279 	rule4->dst_len = frh->dst_len;
280 	rule4->dstmask = inet_make_mask(rule4->dst_len);
281 
282 	net->ipv4.fib_has_custom_rules = true;
283 
284 	err = 0;
285 errout:
286 	return err;
287 }
288 
289 static int fib4_rule_delete(struct fib_rule *rule)
290 {
291 	struct net *net = rule->fr_net;
292 	int err;
293 
294 	/* split local/main if they are not already split */
295 	err = fib_unmerge(net);
296 	if (err)
297 		goto errout;
298 
299 #ifdef CONFIG_IP_ROUTE_CLASSID
300 	if (((struct fib4_rule *)rule)->tclassid)
301 		atomic_dec(&net->ipv4.fib_num_tclassid_users);
302 #endif
303 	net->ipv4.fib_has_custom_rules = true;
304 
305 	if (net->ipv4.fib_rules_require_fldissect &&
306 	    fib_rule_requires_fldissect(rule))
307 		net->ipv4.fib_rules_require_fldissect--;
308 errout:
309 	return err;
310 }
311 
312 static int fib4_rule_compare(struct fib_rule *rule, struct fib_rule_hdr *frh,
313 			     struct nlattr **tb)
314 {
315 	struct fib4_rule *rule4 = (struct fib4_rule *) rule;
316 
317 	if (frh->src_len && (rule4->src_len != frh->src_len))
318 		return 0;
319 
320 	if (frh->dst_len && (rule4->dst_len != frh->dst_len))
321 		return 0;
322 
323 	if (frh->tos && inet_dscp_to_dsfield(rule4->dscp) != frh->tos)
324 		return 0;
325 
326 #ifdef CONFIG_IP_ROUTE_CLASSID
327 	if (tb[FRA_FLOW] && (rule4->tclassid != nla_get_u32(tb[FRA_FLOW])))
328 		return 0;
329 #endif
330 
331 	if (frh->src_len && (rule4->src != nla_get_in_addr(tb[FRA_SRC])))
332 		return 0;
333 
334 	if (frh->dst_len && (rule4->dst != nla_get_in_addr(tb[FRA_DST])))
335 		return 0;
336 
337 	return 1;
338 }
339 
340 static int fib4_rule_fill(struct fib_rule *rule, struct sk_buff *skb,
341 			  struct fib_rule_hdr *frh)
342 {
343 	struct fib4_rule *rule4 = (struct fib4_rule *) rule;
344 
345 	frh->dst_len = rule4->dst_len;
346 	frh->src_len = rule4->src_len;
347 	frh->tos = inet_dscp_to_dsfield(rule4->dscp);
348 
349 	if ((rule4->dst_len &&
350 	     nla_put_in_addr(skb, FRA_DST, rule4->dst)) ||
351 	    (rule4->src_len &&
352 	     nla_put_in_addr(skb, FRA_SRC, rule4->src)))
353 		goto nla_put_failure;
354 #ifdef CONFIG_IP_ROUTE_CLASSID
355 	if (rule4->tclassid &&
356 	    nla_put_u32(skb, FRA_FLOW, rule4->tclassid))
357 		goto nla_put_failure;
358 #endif
359 	return 0;
360 
361 nla_put_failure:
362 	return -ENOBUFS;
363 }
364 
365 static size_t fib4_rule_nlmsg_payload(struct fib_rule *rule)
366 {
367 	return nla_total_size(4) /* dst */
368 	       + nla_total_size(4) /* src */
369 	       + nla_total_size(4); /* flow */
370 }
371 
372 static void fib4_rule_flush_cache(struct fib_rules_ops *ops)
373 {
374 	rt_cache_flush(ops->fro_net);
375 }
376 
377 static const struct fib_rules_ops __net_initconst fib4_rules_ops_template = {
378 	.family		= AF_INET,
379 	.rule_size	= sizeof(struct fib4_rule),
380 	.addr_size	= sizeof(u32),
381 	.action		= fib4_rule_action,
382 	.suppress	= fib4_rule_suppress,
383 	.match		= fib4_rule_match,
384 	.configure	= fib4_rule_configure,
385 	.delete		= fib4_rule_delete,
386 	.compare	= fib4_rule_compare,
387 	.fill		= fib4_rule_fill,
388 	.nlmsg_payload	= fib4_rule_nlmsg_payload,
389 	.flush_cache	= fib4_rule_flush_cache,
390 	.nlgroup	= RTNLGRP_IPV4_RULE,
391 	.owner		= THIS_MODULE,
392 };
393 
394 static int fib_default_rules_init(struct fib_rules_ops *ops)
395 {
396 	int err;
397 
398 	err = fib_default_rule_add(ops, 0, RT_TABLE_LOCAL, 0);
399 	if (err < 0)
400 		return err;
401 	err = fib_default_rule_add(ops, 0x7FFE, RT_TABLE_MAIN, 0);
402 	if (err < 0)
403 		return err;
404 	err = fib_default_rule_add(ops, 0x7FFF, RT_TABLE_DEFAULT, 0);
405 	if (err < 0)
406 		return err;
407 	return 0;
408 }
409 
410 int __net_init fib4_rules_init(struct net *net)
411 {
412 	int err;
413 	struct fib_rules_ops *ops;
414 
415 	ops = fib_rules_register(&fib4_rules_ops_template, net);
416 	if (IS_ERR(ops))
417 		return PTR_ERR(ops);
418 
419 	err = fib_default_rules_init(ops);
420 	if (err < 0)
421 		goto fail;
422 	net->ipv4.rules_ops = ops;
423 	net->ipv4.fib_has_custom_rules = false;
424 	net->ipv4.fib_rules_require_fldissect = 0;
425 	return 0;
426 
427 fail:
428 	/* also cleans all rules already added */
429 	fib_rules_unregister(ops);
430 	return err;
431 }
432 
433 void __net_exit fib4_rules_exit(struct net *net)
434 {
435 	fib_rules_unregister(net->ipv4.rules_ops);
436 }
437