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Linux/net/sched/act_bpf.c

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  1 /*
  2  * Copyright (c) 2015 Jiri Pirko <jiri@resnulli.us>
  3  *
  4  * This program is free software; you can redistribute it and/or modify
  5  * it under the terms of the GNU General Public License as published by
  6  * the Free Software Foundation; either version 2 of the License, or
  7  * (at your option) any later version.
  8  */
  9 
 10 #include <linux/module.h>
 11 #include <linux/init.h>
 12 #include <linux/kernel.h>
 13 #include <linux/skbuff.h>
 14 #include <linux/rtnetlink.h>
 15 #include <linux/filter.h>
 16 #include <linux/bpf.h>
 17 
 18 #include <net/netlink.h>
 19 #include <net/pkt_sched.h>
 20 
 21 #include <linux/tc_act/tc_bpf.h>
 22 #include <net/tc_act/tc_bpf.h>
 23 
 24 #define BPF_TAB_MASK            15
 25 #define ACT_BPF_NAME_LEN        256
 26 
 27 struct tcf_bpf_cfg {
 28         struct bpf_prog *filter;
 29         struct sock_filter *bpf_ops;
 30         const char *bpf_name;
 31         u32 bpf_fd;
 32         u16 bpf_num_ops;
 33         bool is_ebpf;
 34 };
 35 
 36 static int bpf_net_id;
 37 
 38 static int tcf_bpf(struct sk_buff *skb, const struct tc_action *act,
 39                    struct tcf_result *res)
 40 {
 41         struct tcf_bpf *prog = act->priv;
 42         struct bpf_prog *filter;
 43         int action, filter_res;
 44         bool at_ingress = G_TC_AT(skb->tc_verd) & AT_INGRESS;
 45 
 46         if (unlikely(!skb_mac_header_was_set(skb)))
 47                 return TC_ACT_UNSPEC;
 48 
 49         tcf_lastuse_update(&prog->tcf_tm);
 50         bstats_cpu_update(this_cpu_ptr(prog->common.cpu_bstats), skb);
 51 
 52         rcu_read_lock();
 53         filter = rcu_dereference(prog->filter);
 54         if (at_ingress) {
 55                 __skb_push(skb, skb->mac_len);
 56                 bpf_compute_data_end(skb);
 57                 filter_res = BPF_PROG_RUN(filter, skb);
 58                 __skb_pull(skb, skb->mac_len);
 59         } else {
 60                 bpf_compute_data_end(skb);
 61                 filter_res = BPF_PROG_RUN(filter, skb);
 62         }
 63         rcu_read_unlock();
 64 
 65         /* A BPF program may overwrite the default action opcode.
 66          * Similarly as in cls_bpf, if filter_res == -1 we use the
 67          * default action specified from tc.
 68          *
 69          * In case a different well-known TC_ACT opcode has been
 70          * returned, it will overwrite the default one.
 71          *
 72          * For everything else that is unkown, TC_ACT_UNSPEC is
 73          * returned.
 74          */
 75         switch (filter_res) {
 76         case TC_ACT_PIPE:
 77         case TC_ACT_RECLASSIFY:
 78         case TC_ACT_OK:
 79         case TC_ACT_REDIRECT:
 80                 action = filter_res;
 81                 break;
 82         case TC_ACT_SHOT:
 83                 action = filter_res;
 84                 qstats_drop_inc(this_cpu_ptr(prog->common.cpu_qstats));
 85                 break;
 86         case TC_ACT_UNSPEC:
 87                 action = prog->tcf_action;
 88                 break;
 89         default:
 90                 action = TC_ACT_UNSPEC;
 91                 break;
 92         }
 93 
 94         return action;
 95 }
 96 
 97 static bool tcf_bpf_is_ebpf(const struct tcf_bpf *prog)
 98 {
 99         return !prog->bpf_ops;
100 }
101 
102 static int tcf_bpf_dump_bpf_info(const struct tcf_bpf *prog,
103                                  struct sk_buff *skb)
104 {
105         struct nlattr *nla;
106 
107         if (nla_put_u16(skb, TCA_ACT_BPF_OPS_LEN, prog->bpf_num_ops))
108                 return -EMSGSIZE;
109 
110         nla = nla_reserve(skb, TCA_ACT_BPF_OPS, prog->bpf_num_ops *
111                           sizeof(struct sock_filter));
112         if (nla == NULL)
113                 return -EMSGSIZE;
114 
115         memcpy(nla_data(nla), prog->bpf_ops, nla_len(nla));
116 
117         return 0;
118 }
119 
120 static int tcf_bpf_dump_ebpf_info(const struct tcf_bpf *prog,
121                                   struct sk_buff *skb)
122 {
123         if (nla_put_u32(skb, TCA_ACT_BPF_FD, prog->bpf_fd))
124                 return -EMSGSIZE;
125 
126         if (prog->bpf_name &&
127             nla_put_string(skb, TCA_ACT_BPF_NAME, prog->bpf_name))
128                 return -EMSGSIZE;
129 
130         return 0;
131 }
132 
133 static int tcf_bpf_dump(struct sk_buff *skb, struct tc_action *act,
134                         int bind, int ref)
135 {
136         unsigned char *tp = skb_tail_pointer(skb);
137         struct tcf_bpf *prog = act->priv;
138         struct tc_act_bpf opt = {
139                 .index   = prog->tcf_index,
140                 .refcnt  = prog->tcf_refcnt - ref,
141                 .bindcnt = prog->tcf_bindcnt - bind,
142                 .action  = prog->tcf_action,
143         };
144         struct tcf_t tm;
145         int ret;
146 
147         if (nla_put(skb, TCA_ACT_BPF_PARMS, sizeof(opt), &opt))
148                 goto nla_put_failure;
149 
150         if (tcf_bpf_is_ebpf(prog))
151                 ret = tcf_bpf_dump_ebpf_info(prog, skb);
152         else
153                 ret = tcf_bpf_dump_bpf_info(prog, skb);
154         if (ret)
155                 goto nla_put_failure;
156 
157         tm.install = jiffies_to_clock_t(jiffies - prog->tcf_tm.install);
158         tm.lastuse = jiffies_to_clock_t(jiffies - prog->tcf_tm.lastuse);
159         tm.expires = jiffies_to_clock_t(prog->tcf_tm.expires);
160 
161         if (nla_put_64bit(skb, TCA_ACT_BPF_TM, sizeof(tm), &tm,
162                           TCA_ACT_BPF_PAD))
163                 goto nla_put_failure;
164 
165         return skb->len;
166 
167 nla_put_failure:
168         nlmsg_trim(skb, tp);
169         return -1;
170 }
171 
172 static const struct nla_policy act_bpf_policy[TCA_ACT_BPF_MAX + 1] = {
173         [TCA_ACT_BPF_PARMS]     = { .len = sizeof(struct tc_act_bpf) },
174         [TCA_ACT_BPF_FD]        = { .type = NLA_U32 },
175         [TCA_ACT_BPF_NAME]      = { .type = NLA_NUL_STRING, .len = ACT_BPF_NAME_LEN },
176         [TCA_ACT_BPF_OPS_LEN]   = { .type = NLA_U16 },
177         [TCA_ACT_BPF_OPS]       = { .type = NLA_BINARY,
178                                     .len = sizeof(struct sock_filter) * BPF_MAXINSNS },
179 };
180 
181 static int tcf_bpf_init_from_ops(struct nlattr **tb, struct tcf_bpf_cfg *cfg)
182 {
183         struct sock_filter *bpf_ops;
184         struct sock_fprog_kern fprog_tmp;
185         struct bpf_prog *fp;
186         u16 bpf_size, bpf_num_ops;
187         int ret;
188 
189         bpf_num_ops = nla_get_u16(tb[TCA_ACT_BPF_OPS_LEN]);
190         if (bpf_num_ops > BPF_MAXINSNS || bpf_num_ops == 0)
191                 return -EINVAL;
192 
193         bpf_size = bpf_num_ops * sizeof(*bpf_ops);
194         if (bpf_size != nla_len(tb[TCA_ACT_BPF_OPS]))
195                 return -EINVAL;
196 
197         bpf_ops = kzalloc(bpf_size, GFP_KERNEL);
198         if (bpf_ops == NULL)
199                 return -ENOMEM;
200 
201         memcpy(bpf_ops, nla_data(tb[TCA_ACT_BPF_OPS]), bpf_size);
202 
203         fprog_tmp.len = bpf_num_ops;
204         fprog_tmp.filter = bpf_ops;
205 
206         ret = bpf_prog_create(&fp, &fprog_tmp);
207         if (ret < 0) {
208                 kfree(bpf_ops);
209                 return ret;
210         }
211 
212         cfg->bpf_ops = bpf_ops;
213         cfg->bpf_num_ops = bpf_num_ops;
214         cfg->filter = fp;
215         cfg->is_ebpf = false;
216 
217         return 0;
218 }
219 
220 static int tcf_bpf_init_from_efd(struct nlattr **tb, struct tcf_bpf_cfg *cfg)
221 {
222         struct bpf_prog *fp;
223         char *name = NULL;
224         u32 bpf_fd;
225 
226         bpf_fd = nla_get_u32(tb[TCA_ACT_BPF_FD]);
227 
228         fp = bpf_prog_get(bpf_fd);
229         if (IS_ERR(fp))
230                 return PTR_ERR(fp);
231 
232         if (fp->type != BPF_PROG_TYPE_SCHED_ACT) {
233                 bpf_prog_put(fp);
234                 return -EINVAL;
235         }
236 
237         if (tb[TCA_ACT_BPF_NAME]) {
238                 name = kmemdup(nla_data(tb[TCA_ACT_BPF_NAME]),
239                                nla_len(tb[TCA_ACT_BPF_NAME]),
240                                GFP_KERNEL);
241                 if (!name) {
242                         bpf_prog_put(fp);
243                         return -ENOMEM;
244                 }
245         }
246 
247         cfg->bpf_fd = bpf_fd;
248         cfg->bpf_name = name;
249         cfg->filter = fp;
250         cfg->is_ebpf = true;
251 
252         return 0;
253 }
254 
255 static void tcf_bpf_cfg_cleanup(const struct tcf_bpf_cfg *cfg)
256 {
257         if (cfg->is_ebpf)
258                 bpf_prog_put(cfg->filter);
259         else
260                 bpf_prog_destroy(cfg->filter);
261 
262         kfree(cfg->bpf_ops);
263         kfree(cfg->bpf_name);
264 }
265 
266 static void tcf_bpf_prog_fill_cfg(const struct tcf_bpf *prog,
267                                   struct tcf_bpf_cfg *cfg)
268 {
269         cfg->is_ebpf = tcf_bpf_is_ebpf(prog);
270         /* updates to prog->filter are prevented, since it's called either
271          * with rtnl lock or during final cleanup in rcu callback
272          */
273         cfg->filter = rcu_dereference_protected(prog->filter, 1);
274 
275         cfg->bpf_ops = prog->bpf_ops;
276         cfg->bpf_name = prog->bpf_name;
277 }
278 
279 static int tcf_bpf_init(struct net *net, struct nlattr *nla,
280                         struct nlattr *est, struct tc_action *act,
281                         int replace, int bind)
282 {
283         struct tc_action_net *tn = net_generic(net, bpf_net_id);
284         struct nlattr *tb[TCA_ACT_BPF_MAX + 1];
285         struct tcf_bpf_cfg cfg, old;
286         struct tc_act_bpf *parm;
287         struct tcf_bpf *prog;
288         bool is_bpf, is_ebpf;
289         int ret, res = 0;
290 
291         if (!nla)
292                 return -EINVAL;
293 
294         ret = nla_parse_nested(tb, TCA_ACT_BPF_MAX, nla, act_bpf_policy);
295         if (ret < 0)
296                 return ret;
297 
298         if (!tb[TCA_ACT_BPF_PARMS])
299                 return -EINVAL;
300 
301         parm = nla_data(tb[TCA_ACT_BPF_PARMS]);
302 
303         if (!tcf_hash_check(tn, parm->index, act, bind)) {
304                 ret = tcf_hash_create(tn, parm->index, est, act,
305                                       sizeof(*prog), bind, true);
306                 if (ret < 0)
307                         return ret;
308 
309                 res = ACT_P_CREATED;
310         } else {
311                 /* Don't override defaults. */
312                 if (bind)
313                         return 0;
314 
315                 tcf_hash_release(act, bind);
316                 if (!replace)
317                         return -EEXIST;
318         }
319 
320         is_bpf = tb[TCA_ACT_BPF_OPS_LEN] && tb[TCA_ACT_BPF_OPS];
321         is_ebpf = tb[TCA_ACT_BPF_FD];
322 
323         if ((!is_bpf && !is_ebpf) || (is_bpf && is_ebpf)) {
324                 ret = -EINVAL;
325                 goto out;
326         }
327 
328         memset(&cfg, 0, sizeof(cfg));
329 
330         ret = is_bpf ? tcf_bpf_init_from_ops(tb, &cfg) :
331                        tcf_bpf_init_from_efd(tb, &cfg);
332         if (ret < 0)
333                 goto out;
334 
335         prog = to_bpf(act);
336         ASSERT_RTNL();
337 
338         if (res != ACT_P_CREATED)
339                 tcf_bpf_prog_fill_cfg(prog, &old);
340 
341         prog->bpf_ops = cfg.bpf_ops;
342         prog->bpf_name = cfg.bpf_name;
343 
344         if (cfg.bpf_num_ops)
345                 prog->bpf_num_ops = cfg.bpf_num_ops;
346         if (cfg.bpf_fd)
347                 prog->bpf_fd = cfg.bpf_fd;
348 
349         prog->tcf_action = parm->action;
350         rcu_assign_pointer(prog->filter, cfg.filter);
351 
352         if (res == ACT_P_CREATED) {
353                 tcf_hash_insert(tn, act);
354         } else {
355                 /* make sure the program being replaced is no longer executing */
356                 synchronize_rcu();
357                 tcf_bpf_cfg_cleanup(&old);
358         }
359 
360         return res;
361 out:
362         if (res == ACT_P_CREATED)
363                 tcf_hash_cleanup(act, est);
364 
365         return ret;
366 }
367 
368 static void tcf_bpf_cleanup(struct tc_action *act, int bind)
369 {
370         struct tcf_bpf_cfg tmp;
371 
372         tcf_bpf_prog_fill_cfg(act->priv, &tmp);
373         tcf_bpf_cfg_cleanup(&tmp);
374 }
375 
376 static int tcf_bpf_walker(struct net *net, struct sk_buff *skb,
377                           struct netlink_callback *cb, int type,
378                           struct tc_action *a)
379 {
380         struct tc_action_net *tn = net_generic(net, bpf_net_id);
381 
382         return tcf_generic_walker(tn, skb, cb, type, a);
383 }
384 
385 static int tcf_bpf_search(struct net *net, struct tc_action *a, u32 index)
386 {
387         struct tc_action_net *tn = net_generic(net, bpf_net_id);
388 
389         return tcf_hash_search(tn, a, index);
390 }
391 
392 static struct tc_action_ops act_bpf_ops __read_mostly = {
393         .kind           =       "bpf",
394         .type           =       TCA_ACT_BPF,
395         .owner          =       THIS_MODULE,
396         .act            =       tcf_bpf,
397         .dump           =       tcf_bpf_dump,
398         .cleanup        =       tcf_bpf_cleanup,
399         .init           =       tcf_bpf_init,
400         .walk           =       tcf_bpf_walker,
401         .lookup         =       tcf_bpf_search,
402 };
403 
404 static __net_init int bpf_init_net(struct net *net)
405 {
406         struct tc_action_net *tn = net_generic(net, bpf_net_id);
407 
408         return tc_action_net_init(tn, &act_bpf_ops, BPF_TAB_MASK);
409 }
410 
411 static void __net_exit bpf_exit_net(struct net *net)
412 {
413         struct tc_action_net *tn = net_generic(net, bpf_net_id);
414 
415         tc_action_net_exit(tn);
416 }
417 
418 static struct pernet_operations bpf_net_ops = {
419         .init = bpf_init_net,
420         .exit = bpf_exit_net,
421         .id   = &bpf_net_id,
422         .size = sizeof(struct tc_action_net),
423 };
424 
425 static int __init bpf_init_module(void)
426 {
427         return tcf_register_action(&act_bpf_ops, &bpf_net_ops);
428 }
429 
430 static void __exit bpf_cleanup_module(void)
431 {
432         tcf_unregister_action(&act_bpf_ops, &bpf_net_ops);
433 }
434 
435 module_init(bpf_init_module);
436 module_exit(bpf_cleanup_module);
437 
438 MODULE_AUTHOR("Jiri Pirko <jiri@resnulli.us>");
439 MODULE_DESCRIPTION("TC BPF based action");
440 MODULE_LICENSE("GPL v2");
441 

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