xref: /openbmc/linux/net/sched/cls_bpf.c (revision c819e2cf) 
1 /*
2  * Berkeley Packet Filter based traffic classifier
3  *
4  * Might be used to classify traffic through flexible, user-defined and
5  * possibly JIT-ed BPF filters for traffic control as an alternative to
6  * ematches.
7  *
8  * (C) 2013 Daniel Borkmann <dborkman@redhat.com>
9  *
10  * This program is free software; you can redistribute it and/or modify
11  * it under the terms of the GNU General Public License version 2 as
12  * published by the Free Software Foundation.
13  */
14 
15 #include <linux/module.h>
16 #include <linux/types.h>
17 #include <linux/skbuff.h>
18 #include <linux/filter.h>
19 #include <net/rtnetlink.h>
20 #include <net/pkt_cls.h>
21 #include <net/sock.h>
22 
23 MODULE_LICENSE("GPL");
24 MODULE_AUTHOR("Daniel Borkmann <dborkman@redhat.com>");
25 MODULE_DESCRIPTION("TC BPF based classifier");
26 
27 struct cls_bpf_head {
28 	struct list_head plist;
29 	u32 hgen;
30 	struct rcu_head rcu;
31 };
32 
33 struct cls_bpf_prog {
34 	struct bpf_prog *filter;
35 	struct sock_filter *bpf_ops;
36 	struct tcf_exts exts;
37 	struct tcf_result res;
38 	struct list_head link;
39 	u32 handle;
40 	u16 bpf_len;
41 	struct tcf_proto *tp;
42 	struct rcu_head rcu;
43 };
44 
45 static const struct nla_policy bpf_policy[TCA_BPF_MAX + 1] = {
46 	[TCA_BPF_CLASSID]	= { .type = NLA_U32 },
47 	[TCA_BPF_OPS_LEN]	= { .type = NLA_U16 },
48 	[TCA_BPF_OPS]		= { .type = NLA_BINARY,
49 				    .len = sizeof(struct sock_filter) * BPF_MAXINSNS },
50 };
51 
52 static int cls_bpf_classify(struct sk_buff *skb, const struct tcf_proto *tp,
53 			    struct tcf_result *res)
54 {
55 	struct cls_bpf_head *head = rcu_dereference_bh(tp->root);
56 	struct cls_bpf_prog *prog;
57 	int ret;
58 
59 	list_for_each_entry_rcu(prog, &head->plist, link) {
60 		int filter_res = BPF_PROG_RUN(prog->filter, skb);
61 
62 		if (filter_res == 0)
63 			continue;
64 
65 		*res = prog->res;
66 		if (filter_res != -1)
67 			res->classid = filter_res;
68 
69 		ret = tcf_exts_exec(skb, &prog->exts, res);
70 		if (ret < 0)
71 			continue;
72 
73 		return ret;
74 	}
75 
76 	return -1;
77 }
78 
79 static int cls_bpf_init(struct tcf_proto *tp)
80 {
81 	struct cls_bpf_head *head;
82 
83 	head = kzalloc(sizeof(*head), GFP_KERNEL);
84 	if (head == NULL)
85 		return -ENOBUFS;
86 
87 	INIT_LIST_HEAD_RCU(&head->plist);
88 	rcu_assign_pointer(tp->root, head);
89 
90 	return 0;
91 }
92 
93 static void cls_bpf_delete_prog(struct tcf_proto *tp, struct cls_bpf_prog *prog)
94 {
95 	tcf_exts_destroy(&prog->exts);
96 
97 	bpf_prog_destroy(prog->filter);
98 
99 	kfree(prog->bpf_ops);
100 	kfree(prog);
101 }
102 
103 static void __cls_bpf_delete_prog(struct rcu_head *rcu)
104 {
105 	struct cls_bpf_prog *prog = container_of(rcu, struct cls_bpf_prog, rcu);
106 
107 	cls_bpf_delete_prog(prog->tp, prog);
108 }
109 
110 static int cls_bpf_delete(struct tcf_proto *tp, unsigned long arg)
111 {
112 	struct cls_bpf_prog *prog = (struct cls_bpf_prog *) arg;
113 
114 	list_del_rcu(&prog->link);
115 	tcf_unbind_filter(tp, &prog->res);
116 	call_rcu(&prog->rcu, __cls_bpf_delete_prog);
117 	return 0;
118 }
119 
120 static void cls_bpf_destroy(struct tcf_proto *tp)
121 {
122 	struct cls_bpf_head *head = rtnl_dereference(tp->root);
123 	struct cls_bpf_prog *prog, *tmp;
124 
125 	list_for_each_entry_safe(prog, tmp, &head->plist, link) {
126 		list_del_rcu(&prog->link);
127 		tcf_unbind_filter(tp, &prog->res);
128 		call_rcu(&prog->rcu, __cls_bpf_delete_prog);
129 	}
130 
131 	RCU_INIT_POINTER(tp->root, NULL);
132 	kfree_rcu(head, rcu);
133 }
134 
135 static unsigned long cls_bpf_get(struct tcf_proto *tp, u32 handle)
136 {
137 	struct cls_bpf_head *head = rtnl_dereference(tp->root);
138 	struct cls_bpf_prog *prog;
139 	unsigned long ret = 0UL;
140 
141 	if (head == NULL)
142 		return 0UL;
143 
144 	list_for_each_entry(prog, &head->plist, link) {
145 		if (prog->handle == handle) {
146 			ret = (unsigned long) prog;
147 			break;
148 		}
149 	}
150 
151 	return ret;
152 }
153 
154 static int cls_bpf_modify_existing(struct net *net, struct tcf_proto *tp,
155 				   struct cls_bpf_prog *prog,
156 				   unsigned long base, struct nlattr **tb,
157 				   struct nlattr *est, bool ovr)
158 {
159 	struct sock_filter *bpf_ops;
160 	struct tcf_exts exts;
161 	struct sock_fprog_kern tmp;
162 	struct bpf_prog *fp;
163 	u16 bpf_size, bpf_len;
164 	u32 classid;
165 	int ret;
166 
167 	if (!tb[TCA_BPF_OPS_LEN] || !tb[TCA_BPF_OPS] || !tb[TCA_BPF_CLASSID])
168 		return -EINVAL;
169 
170 	tcf_exts_init(&exts, TCA_BPF_ACT, TCA_BPF_POLICE);
171 	ret = tcf_exts_validate(net, tp, tb, est, &exts, ovr);
172 	if (ret < 0)
173 		return ret;
174 
175 	classid = nla_get_u32(tb[TCA_BPF_CLASSID]);
176 	bpf_len = nla_get_u16(tb[TCA_BPF_OPS_LEN]);
177 	if (bpf_len > BPF_MAXINSNS || bpf_len == 0) {
178 		ret = -EINVAL;
179 		goto errout;
180 	}
181 
182 	bpf_size = bpf_len * sizeof(*bpf_ops);
183 	if (bpf_size != nla_len(tb[TCA_BPF_OPS])) {
184 		ret = -EINVAL;
185 		goto errout;
186 	}
187 
188 	bpf_ops = kzalloc(bpf_size, GFP_KERNEL);
189 	if (bpf_ops == NULL) {
190 		ret = -ENOMEM;
191 		goto errout;
192 	}
193 
194 	memcpy(bpf_ops, nla_data(tb[TCA_BPF_OPS]), bpf_size);
195 
196 	tmp.len = bpf_len;
197 	tmp.filter = bpf_ops;
198 
199 	ret = bpf_prog_create(&fp, &tmp);
200 	if (ret)
201 		goto errout_free;
202 
203 	prog->bpf_len = bpf_len;
204 	prog->bpf_ops = bpf_ops;
205 	prog->filter = fp;
206 	prog->res.classid = classid;
207 
208 	tcf_bind_filter(tp, &prog->res, base);
209 	tcf_exts_change(tp, &prog->exts, &exts);
210 
211 	return 0;
212 errout_free:
213 	kfree(bpf_ops);
214 errout:
215 	tcf_exts_destroy(&exts);
216 	return ret;
217 }
218 
219 static u32 cls_bpf_grab_new_handle(struct tcf_proto *tp,
220 				   struct cls_bpf_head *head)
221 {
222 	unsigned int i = 0x80000000;
223 	u32 handle;
224 
225 	do {
226 		if (++head->hgen == 0x7FFFFFFF)
227 			head->hgen = 1;
228 	} while (--i > 0 && cls_bpf_get(tp, head->hgen));
229 
230 	if (unlikely(i == 0)) {
231 		pr_err("Insufficient number of handles\n");
232 		handle = 0;
233 	} else {
234 		handle = head->hgen;
235 	}
236 
237 	return handle;
238 }
239 
240 static int cls_bpf_change(struct net *net, struct sk_buff *in_skb,
241 			  struct tcf_proto *tp, unsigned long base,
242 			  u32 handle, struct nlattr **tca,
243 			  unsigned long *arg, bool ovr)
244 {
245 	struct cls_bpf_head *head = rtnl_dereference(tp->root);
246 	struct cls_bpf_prog *oldprog = (struct cls_bpf_prog *) *arg;
247 	struct nlattr *tb[TCA_BPF_MAX + 1];
248 	struct cls_bpf_prog *prog;
249 	int ret;
250 
251 	if (tca[TCA_OPTIONS] == NULL)
252 		return -EINVAL;
253 
254 	ret = nla_parse_nested(tb, TCA_BPF_MAX, tca[TCA_OPTIONS], bpf_policy);
255 	if (ret < 0)
256 		return ret;
257 
258 	prog = kzalloc(sizeof(*prog), GFP_KERNEL);
259 	if (!prog)
260 		return -ENOBUFS;
261 
262 	tcf_exts_init(&prog->exts, TCA_BPF_ACT, TCA_BPF_POLICE);
263 
264 	if (oldprog) {
265 		if (handle && oldprog->handle != handle) {
266 			ret = -EINVAL;
267 			goto errout;
268 		}
269 	}
270 
271 	if (handle == 0)
272 		prog->handle = cls_bpf_grab_new_handle(tp, head);
273 	else
274 		prog->handle = handle;
275 	if (prog->handle == 0) {
276 		ret = -EINVAL;
277 		goto errout;
278 	}
279 
280 	ret = cls_bpf_modify_existing(net, tp, prog, base, tb, tca[TCA_RATE], ovr);
281 	if (ret < 0)
282 		goto errout;
283 
284 	if (oldprog) {
285 		list_replace_rcu(&prog->link, &oldprog->link);
286 		tcf_unbind_filter(tp, &oldprog->res);
287 		call_rcu(&oldprog->rcu, __cls_bpf_delete_prog);
288 	} else {
289 		list_add_rcu(&prog->link, &head->plist);
290 	}
291 
292 	*arg = (unsigned long) prog;
293 	return 0;
294 errout:
295 	kfree(prog);
296 
297 	return ret;
298 }
299 
300 static int cls_bpf_dump(struct net *net, struct tcf_proto *tp, unsigned long fh,
301 			struct sk_buff *skb, struct tcmsg *tm)
302 {
303 	struct cls_bpf_prog *prog = (struct cls_bpf_prog *) fh;
304 	struct nlattr *nest, *nla;
305 
306 	if (prog == NULL)
307 		return skb->len;
308 
309 	tm->tcm_handle = prog->handle;
310 
311 	nest = nla_nest_start(skb, TCA_OPTIONS);
312 	if (nest == NULL)
313 		goto nla_put_failure;
314 
315 	if (nla_put_u32(skb, TCA_BPF_CLASSID, prog->res.classid))
316 		goto nla_put_failure;
317 	if (nla_put_u16(skb, TCA_BPF_OPS_LEN, prog->bpf_len))
318 		goto nla_put_failure;
319 
320 	nla = nla_reserve(skb, TCA_BPF_OPS, prog->bpf_len *
321 			  sizeof(struct sock_filter));
322 	if (nla == NULL)
323 		goto nla_put_failure;
324 
325 	memcpy(nla_data(nla), prog->bpf_ops, nla_len(nla));
326 
327 	if (tcf_exts_dump(skb, &prog->exts) < 0)
328 		goto nla_put_failure;
329 
330 	nla_nest_end(skb, nest);
331 
332 	if (tcf_exts_dump_stats(skb, &prog->exts) < 0)
333 		goto nla_put_failure;
334 
335 	return skb->len;
336 
337 nla_put_failure:
338 	nla_nest_cancel(skb, nest);
339 	return -1;
340 }
341 
342 static void cls_bpf_walk(struct tcf_proto *tp, struct tcf_walker *arg)
343 {
344 	struct cls_bpf_head *head = rtnl_dereference(tp->root);
345 	struct cls_bpf_prog *prog;
346 
347 	list_for_each_entry(prog, &head->plist, link) {
348 		if (arg->count < arg->skip)
349 			goto skip;
350 		if (arg->fn(tp, (unsigned long) prog, arg) < 0) {
351 			arg->stop = 1;
352 			break;
353 		}
354 skip:
355 		arg->count++;
356 	}
357 }
358 
359 static struct tcf_proto_ops cls_bpf_ops __read_mostly = {
360 	.kind		=	"bpf",
361 	.owner		=	THIS_MODULE,
362 	.classify	=	cls_bpf_classify,
363 	.init		=	cls_bpf_init,
364 	.destroy	=	cls_bpf_destroy,
365 	.get		=	cls_bpf_get,
366 	.change		=	cls_bpf_change,
367 	.delete		=	cls_bpf_delete,
368 	.walk		=	cls_bpf_walk,
369 	.dump		=	cls_bpf_dump,
370 };
371 
372 static int __init cls_bpf_init_mod(void)
373 {
374 	return register_tcf_proto_ops(&cls_bpf_ops);
375 }
376 
377 static void __exit cls_bpf_exit_mod(void)
378 {
379 	unregister_tcf_proto_ops(&cls_bpf_ops);
380 }
381 
382 module_init(cls_bpf_init_mod);
383 module_exit(cls_bpf_exit_mod);
384