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

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