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Linux/net/sched/act_bpf.c

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  1 // SPDX-License-Identifier: GPL-2.0-or-later
  2 /*
  3  * Copyright (c) 2015 Jiri Pirko <jiri@resnulli.us>
  4  */
  5 
  6 #include <linux/module.h>
  7 #include <linux/init.h>
  8 #include <linux/kernel.h>
  9 #include <linux/skbuff.h>
 10 #include <linux/rtnetlink.h>
 11 #include <linux/filter.h>
 12 #include <linux/bpf.h>
 13 
 14 #include <net/netlink.h>
 15 #include <net/sock.h>
 16 #include <net/pkt_sched.h>
 17 #include <net/pkt_cls.h>
 18 
 19 #include <linux/tc_act/tc_bpf.h>
 20 #include <net/tc_act/tc_bpf.h>
 21 
 22 #define ACT_BPF_NAME_LEN        256
 23 
 24 struct tcf_bpf_cfg {
 25         struct bpf_prog *filter;
 26         struct sock_filter *bpf_ops;
 27         const char *bpf_name;
 28         u16 bpf_num_ops;
 29         bool is_ebpf;
 30 };
 31 
 32 static unsigned int bpf_net_id;
 33 static struct tc_action_ops act_bpf_ops;
 34 
 35 static int tcf_bpf_act(struct sk_buff *skb, const struct tc_action *act,
 36                        struct tcf_result *res)
 37 {
 38         bool at_ingress = skb_at_tc_ingress(skb);
 39         struct tcf_bpf *prog = to_bpf(act);
 40         struct bpf_prog *filter;
 41         int action, filter_res;
 42 
 43         tcf_lastuse_update(&prog->tcf_tm);
 44         bstats_cpu_update(this_cpu_ptr(prog->common.cpu_bstats), skb);
 45 
 46         rcu_read_lock();
 47         filter = rcu_dereference(prog->filter);
 48         if (at_ingress) {
 49                 __skb_push(skb, skb->mac_len);
 50                 bpf_compute_data_pointers(skb);
 51                 filter_res = BPF_PROG_RUN(filter, skb);
 52                 __skb_pull(skb, skb->mac_len);
 53         } else {
 54                 bpf_compute_data_pointers(skb);
 55                 filter_res = BPF_PROG_RUN(filter, skb);
 56         }
 57         if (skb_sk_is_prefetched(skb) && filter_res != TC_ACT_OK)
 58                 skb_orphan(skb);
 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 unknown, 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  = refcount_read(&prog->tcf_refcnt) - ref,
145                 .bindcnt = atomic_read(&prog->tcf_bindcnt) - bind,
146         };
147         struct tcf_t tm;
148         int ret;
149 
150         spin_lock_bh(&prog->tcf_lock);
151         opt.action = prog->tcf_action;
152         if (nla_put(skb, TCA_ACT_BPF_PARMS, sizeof(opt), &opt))
153                 goto nla_put_failure;
154 
155         if (tcf_bpf_is_ebpf(prog))
156                 ret = tcf_bpf_dump_ebpf_info(prog, skb);
157         else
158                 ret = tcf_bpf_dump_bpf_info(prog, skb);
159         if (ret)
160                 goto nla_put_failure;
161 
162         tcf_tm_dump(&tm, &prog->tcf_tm);
163         if (nla_put_64bit(skb, TCA_ACT_BPF_TM, sizeof(tm), &tm,
164                           TCA_ACT_BPF_PAD))
165                 goto nla_put_failure;
166 
167         spin_unlock_bh(&prog->tcf_lock);
168         return skb->len;
169 
170 nla_put_failure:
171         spin_unlock_bh(&prog->tcf_lock);
172         nlmsg_trim(skb, tp);
173         return -1;
174 }
175 
176 static const struct nla_policy act_bpf_policy[TCA_ACT_BPF_MAX + 1] = {
177         [TCA_ACT_BPF_PARMS]     = { .len = sizeof(struct tc_act_bpf) },
178         [TCA_ACT_BPF_FD]        = { .type = NLA_U32 },
179         [TCA_ACT_BPF_NAME]      = { .type = NLA_NUL_STRING,
180                                     .len = ACT_BPF_NAME_LEN },
181         [TCA_ACT_BPF_OPS_LEN]   = { .type = NLA_U16 },
182         [TCA_ACT_BPF_OPS]       = { .type = NLA_BINARY,
183                                     .len = sizeof(struct sock_filter) * BPF_MAXINSNS },
184 };
185 
186 static int tcf_bpf_init_from_ops(struct nlattr **tb, struct tcf_bpf_cfg *cfg)
187 {
188         struct sock_filter *bpf_ops;
189         struct sock_fprog_kern fprog_tmp;
190         struct bpf_prog *fp;
191         u16 bpf_size, bpf_num_ops;
192         int ret;
193 
194         bpf_num_ops = nla_get_u16(tb[TCA_ACT_BPF_OPS_LEN]);
195         if (bpf_num_ops > BPF_MAXINSNS || bpf_num_ops == 0)
196                 return -EINVAL;
197 
198         bpf_size = bpf_num_ops * sizeof(*bpf_ops);
199         if (bpf_size != nla_len(tb[TCA_ACT_BPF_OPS]))
200                 return -EINVAL;
201 
202         bpf_ops = kmemdup(nla_data(tb[TCA_ACT_BPF_OPS]), bpf_size, GFP_KERNEL);
203         if (bpf_ops == NULL)
204                 return -ENOMEM;
205 
206         fprog_tmp.len = bpf_num_ops;
207         fprog_tmp.filter = bpf_ops;
208 
209         ret = bpf_prog_create(&fp, &fprog_tmp);
210         if (ret < 0) {
211                 kfree(bpf_ops);
212                 return ret;
213         }
214 
215         cfg->bpf_ops = bpf_ops;
216         cfg->bpf_num_ops = bpf_num_ops;
217         cfg->filter = fp;
218         cfg->is_ebpf = false;
219 
220         return 0;
221 }
222 
223 static int tcf_bpf_init_from_efd(struct nlattr **tb, struct tcf_bpf_cfg *cfg)
224 {
225         struct bpf_prog *fp;
226         char *name = NULL;
227         u32 bpf_fd;
228 
229         bpf_fd = nla_get_u32(tb[TCA_ACT_BPF_FD]);
230 
231         fp = bpf_prog_get_type(bpf_fd, BPF_PROG_TYPE_SCHED_ACT);
232         if (IS_ERR(fp))
233                 return PTR_ERR(fp);
234 
235         if (tb[TCA_ACT_BPF_NAME]) {
236                 name = nla_memdup(tb[TCA_ACT_BPF_NAME], GFP_KERNEL);
237                 if (!name) {
238                         bpf_prog_put(fp);
239                         return -ENOMEM;
240                 }
241         }
242 
243         cfg->bpf_name = name;
244         cfg->filter = fp;
245         cfg->is_ebpf = true;
246 
247         return 0;
248 }
249 
250 static void tcf_bpf_cfg_cleanup(const struct tcf_bpf_cfg *cfg)
251 {
252         struct bpf_prog *filter = cfg->filter;
253 
254         if (filter) {
255                 if (cfg->is_ebpf)
256                         bpf_prog_put(filter);
257                 else
258                         bpf_prog_destroy(filter);
259         }
260 
261         kfree(cfg->bpf_ops);
262         kfree(cfg->bpf_name);
263 }
264 
265 static void tcf_bpf_prog_fill_cfg(const struct tcf_bpf *prog,
266                                   struct tcf_bpf_cfg *cfg)
267 {
268         cfg->is_ebpf = tcf_bpf_is_ebpf(prog);
269         /* updates to prog->filter are prevented, since it's called either
270          * with tcf lock or during final cleanup in rcu callback
271          */
272         cfg->filter = rcu_dereference_protected(prog->filter, 1);
273 
274         cfg->bpf_ops = prog->bpf_ops;
275         cfg->bpf_name = prog->bpf_name;
276 }
277 
278 static int tcf_bpf_init(struct net *net, struct nlattr *nla,
279                         struct nlattr *est, struct tc_action **act,
280                         int replace, int bind, bool rtnl_held,
281                         struct tcf_proto *tp, u32 flags,
282                         struct netlink_ext_ack *extack)
283 {
284         struct tc_action_net *tn = net_generic(net, bpf_net_id);
285         struct nlattr *tb[TCA_ACT_BPF_MAX + 1];
286         struct tcf_chain *goto_ch = NULL;
287         struct tcf_bpf_cfg cfg, old;
288         struct tc_act_bpf *parm;
289         struct tcf_bpf *prog;
290         bool is_bpf, is_ebpf;
291         int ret, res = 0;
292         u32 index;
293 
294         if (!nla)
295                 return -EINVAL;
296 
297         ret = nla_parse_nested_deprecated(tb, TCA_ACT_BPF_MAX, nla,
298                                           act_bpf_policy, NULL);
299         if (ret < 0)
300                 return ret;
301 
302         if (!tb[TCA_ACT_BPF_PARMS])
303                 return -EINVAL;
304 
305         parm = nla_data(tb[TCA_ACT_BPF_PARMS]);
306         index = parm->index;
307         ret = tcf_idr_check_alloc(tn, &index, act, bind);
308         if (!ret) {
309                 ret = tcf_idr_create(tn, index, est, act,
310                                      &act_bpf_ops, bind, true, 0);
311                 if (ret < 0) {
312                         tcf_idr_cleanup(tn, index);
313                         return ret;
314                 }
315 
316                 res = ACT_P_CREATED;
317         } else if (ret > 0) {
318                 /* Don't override defaults. */
319                 if (bind)
320                         return 0;
321 
322                 if (!replace) {
323                         tcf_idr_release(*act, bind);
324                         return -EEXIST;
325                 }
326         } else {
327                 return ret;
328         }
329 
330         ret = tcf_action_check_ctrlact(parm->action, tp, &goto_ch, extack);
331         if (ret < 0)
332                 goto release_idr;
333 
334         is_bpf = tb[TCA_ACT_BPF_OPS_LEN] && tb[TCA_ACT_BPF_OPS];
335         is_ebpf = tb[TCA_ACT_BPF_FD];
336 
337         if ((!is_bpf && !is_ebpf) || (is_bpf && is_ebpf)) {
338                 ret = -EINVAL;
339                 goto put_chain;
340         }
341 
342         memset(&cfg, 0, sizeof(cfg));
343 
344         ret = is_bpf ? tcf_bpf_init_from_ops(tb, &cfg) :
345                        tcf_bpf_init_from_efd(tb, &cfg);
346         if (ret < 0)
347                 goto put_chain;
348 
349         prog = to_bpf(*act);
350 
351         spin_lock_bh(&prog->tcf_lock);
352         if (res != ACT_P_CREATED)
353                 tcf_bpf_prog_fill_cfg(prog, &old);
354 
355         prog->bpf_ops = cfg.bpf_ops;
356         prog->bpf_name = cfg.bpf_name;
357 
358         if (cfg.bpf_num_ops)
359                 prog->bpf_num_ops = cfg.bpf_num_ops;
360 
361         goto_ch = tcf_action_set_ctrlact(*act, parm->action, goto_ch);
362         rcu_assign_pointer(prog->filter, cfg.filter);
363         spin_unlock_bh(&prog->tcf_lock);
364 
365         if (goto_ch)
366                 tcf_chain_put_by_act(goto_ch);
367 
368         if (res != ACT_P_CREATED) {
369                 /* make sure the program being replaced is no longer executing */
370                 synchronize_rcu();
371                 tcf_bpf_cfg_cleanup(&old);
372         }
373 
374         return res;
375 
376 put_chain:
377         if (goto_ch)
378                 tcf_chain_put_by_act(goto_ch);
379 
380 release_idr:
381         tcf_idr_release(*act, bind);
382         return ret;
383 }
384 
385 static void tcf_bpf_cleanup(struct tc_action *act)
386 {
387         struct tcf_bpf_cfg tmp;
388 
389         tcf_bpf_prog_fill_cfg(to_bpf(act), &tmp);
390         tcf_bpf_cfg_cleanup(&tmp);
391 }
392 
393 static int tcf_bpf_walker(struct net *net, struct sk_buff *skb,
394                           struct netlink_callback *cb, int type,
395                           const struct tc_action_ops *ops,
396                           struct netlink_ext_ack *extack)
397 {
398         struct tc_action_net *tn = net_generic(net, bpf_net_id);
399 
400         return tcf_generic_walker(tn, skb, cb, type, ops, extack);
401 }
402 
403 static int tcf_bpf_search(struct net *net, struct tc_action **a, u32 index)
404 {
405         struct tc_action_net *tn = net_generic(net, bpf_net_id);
406 
407         return tcf_idr_search(tn, a, index);
408 }
409 
410 static struct tc_action_ops act_bpf_ops __read_mostly = {
411         .kind           =       "bpf",
412         .id             =       TCA_ID_BPF,
413         .owner          =       THIS_MODULE,
414         .act            =       tcf_bpf_act,
415         .dump           =       tcf_bpf_dump,
416         .cleanup        =       tcf_bpf_cleanup,
417         .init           =       tcf_bpf_init,
418         .walk           =       tcf_bpf_walker,
419         .lookup         =       tcf_bpf_search,
420         .size           =       sizeof(struct tcf_bpf),
421 };
422 
423 static __net_init int bpf_init_net(struct net *net)
424 {
425         struct tc_action_net *tn = net_generic(net, bpf_net_id);
426 
427         return tc_action_net_init(net, tn, &act_bpf_ops);
428 }
429 
430 static void __net_exit bpf_exit_net(struct list_head *net_list)
431 {
432         tc_action_net_exit(net_list, bpf_net_id);
433 }
434 
435 static struct pernet_operations bpf_net_ops = {
436         .init = bpf_init_net,
437         .exit_batch = bpf_exit_net,
438         .id   = &bpf_net_id,
439         .size = sizeof(struct tc_action_net),
440 };
441 
442 static int __init bpf_init_module(void)
443 {
444         return tcf_register_action(&act_bpf_ops, &bpf_net_ops);
445 }
446 
447 static void __exit bpf_cleanup_module(void)
448 {
449         tcf_unregister_action(&act_bpf_ops, &bpf_net_ops);
450 }
451 
452 module_init(bpf_init_module);
453 module_exit(bpf_cleanup_module);
454 
455 MODULE_AUTHOR("Jiri Pirko <jiri@resnulli.us>");
456 MODULE_DESCRIPTION("TC BPF based action");
457 MODULE_LICENSE("GPL v2");
458 

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