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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/pkt_sched.h>
 16 #include <net/pkt_cls.h>
 17 
 18 #include <linux/tc_act/tc_bpf.h>
 19 #include <net/tc_act/tc_bpf.h>
 20 
 21 #define ACT_BPF_NAME_LEN        256
 22 
 23 struct tcf_bpf_cfg {
 24         struct bpf_prog *filter;
 25         struct sock_filter *bpf_ops;
 26         const char *bpf_name;
 27         u16 bpf_num_ops;
 28         bool is_ebpf;
 29 };
 30 
 31 static unsigned int bpf_net_id;
 32 static struct tc_action_ops act_bpf_ops;
 33 
 34 static int tcf_bpf_act(struct sk_buff *skb, const struct tc_action *act,
 35                        struct tcf_result *res)
 36 {
 37         bool at_ingress = skb_at_tc_ingress(skb);
 38         struct tcf_bpf *prog = to_bpf(act);
 39         struct bpf_prog *filter;
 40         int action, filter_res;
 41 
 42         tcf_lastuse_update(&prog->tcf_tm);
 43         bstats_cpu_update(this_cpu_ptr(prog->common.cpu_bstats), skb);
 44 
 45         rcu_read_lock();
 46         filter = rcu_dereference(prog->filter);
 47         if (at_ingress) {
 48                 __skb_push(skb, skb->mac_len);
 49                 bpf_compute_data_pointers(skb);
 50                 filter_res = BPF_PROG_RUN(filter, skb);
 51                 __skb_pull(skb, skb->mac_len);
 52         } else {
 53                 bpf_compute_data_pointers(skb);
 54                 filter_res = BPF_PROG_RUN(filter, skb);
 55         }
 56         rcu_read_unlock();
 57 
 58         /* A BPF program may overwrite the default action opcode.
 59          * Similarly as in cls_bpf, if filter_res == -1 we use the
 60          * default action specified from tc.
 61          *
 62          * In case a different well-known TC_ACT opcode has been
 63          * returned, it will overwrite the default one.
 64          *
 65          * For everything else that is unkown, TC_ACT_UNSPEC is
 66          * returned.
 67          */
 68         switch (filter_res) {
 69         case TC_ACT_PIPE:
 70         case TC_ACT_RECLASSIFY:
 71         case TC_ACT_OK:
 72         case TC_ACT_REDIRECT:
 73                 action = filter_res;
 74                 break;
 75         case TC_ACT_SHOT:
 76                 action = filter_res;
 77                 qstats_drop_inc(this_cpu_ptr(prog->common.cpu_qstats));
 78                 break;
 79         case TC_ACT_UNSPEC:
 80                 action = prog->tcf_action;
 81                 break;
 82         default:
 83                 action = TC_ACT_UNSPEC;
 84                 break;
 85         }
 86 
 87         return action;
 88 }
 89 
 90 static bool tcf_bpf_is_ebpf(const struct tcf_bpf *prog)
 91 {
 92         return !prog->bpf_ops;
 93 }
 94 
 95 static int tcf_bpf_dump_bpf_info(const struct tcf_bpf *prog,
 96                                  struct sk_buff *skb)
 97 {
 98         struct nlattr *nla;
 99 
100         if (nla_put_u16(skb, TCA_ACT_BPF_OPS_LEN, prog->bpf_num_ops))
101                 return -EMSGSIZE;
102 
103         nla = nla_reserve(skb, TCA_ACT_BPF_OPS, prog->bpf_num_ops *
104                           sizeof(struct sock_filter));
105         if (nla == NULL)
106                 return -EMSGSIZE;
107 
108         memcpy(nla_data(nla), prog->bpf_ops, nla_len(nla));
109 
110         return 0;
111 }
112 
113 static int tcf_bpf_dump_ebpf_info(const struct tcf_bpf *prog,
114                                   struct sk_buff *skb)
115 {
116         struct nlattr *nla;
117 
118         if (prog->bpf_name &&
119             nla_put_string(skb, TCA_ACT_BPF_NAME, prog->bpf_name))
120                 return -EMSGSIZE;
121 
122         if (nla_put_u32(skb, TCA_ACT_BPF_ID, prog->filter->aux->id))
123                 return -EMSGSIZE;
124 
125         nla = nla_reserve(skb, TCA_ACT_BPF_TAG, sizeof(prog->filter->tag));
126         if (nla == NULL)
127                 return -EMSGSIZE;
128 
129         memcpy(nla_data(nla), prog->filter->tag, nla_len(nla));
130 
131         return 0;
132 }
133 
134 static int tcf_bpf_dump(struct sk_buff *skb, struct tc_action *act,
135                         int bind, int ref)
136 {
137         unsigned char *tp = skb_tail_pointer(skb);
138         struct tcf_bpf *prog = to_bpf(act);
139         struct tc_act_bpf opt = {
140                 .index   = prog->tcf_index,
141                 .refcnt  = refcount_read(&prog->tcf_refcnt) - ref,
142                 .bindcnt = atomic_read(&prog->tcf_bindcnt) - bind,
143         };
144         struct tcf_t tm;
145         int ret;
146 
147         spin_lock_bh(&prog->tcf_lock);
148         opt.action = prog->tcf_action;
149         if (nla_put(skb, TCA_ACT_BPF_PARMS, sizeof(opt), &opt))
150                 goto nla_put_failure;
151 
152         if (tcf_bpf_is_ebpf(prog))
153                 ret = tcf_bpf_dump_ebpf_info(prog, skb);
154         else
155                 ret = tcf_bpf_dump_bpf_info(prog, skb);
156         if (ret)
157                 goto nla_put_failure;
158 
159         tcf_tm_dump(&tm, &prog->tcf_tm);
160         if (nla_put_64bit(skb, TCA_ACT_BPF_TM, sizeof(tm), &tm,
161                           TCA_ACT_BPF_PAD))
162                 goto nla_put_failure;
163 
164         spin_unlock_bh(&prog->tcf_lock);
165         return skb->len;
166 
167 nla_put_failure:
168         spin_unlock_bh(&prog->tcf_lock);
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 = kmemdup(nla_data(tb[TCA_ACT_BPF_OPS]), bpf_size, GFP_KERNEL);
200         if (bpf_ops == NULL)
201                 return -ENOMEM;
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_type(bpf_fd, BPF_PROG_TYPE_SCHED_ACT);
229         if (IS_ERR(fp))
230                 return PTR_ERR(fp);
231 
232         if (tb[TCA_ACT_BPF_NAME]) {
233                 name = nla_memdup(tb[TCA_ACT_BPF_NAME], GFP_KERNEL);
234                 if (!name) {
235                         bpf_prog_put(fp);
236                         return -ENOMEM;
237                 }
238         }
239 
240         cfg->bpf_name = name;
241         cfg->filter = fp;
242         cfg->is_ebpf = true;
243 
244         return 0;
245 }
246 
247 static void tcf_bpf_cfg_cleanup(const struct tcf_bpf_cfg *cfg)
248 {
249         struct bpf_prog *filter = cfg->filter;
250 
251         if (filter) {
252                 if (cfg->is_ebpf)
253                         bpf_prog_put(filter);
254                 else
255                         bpf_prog_destroy(filter);
256         }
257 
258         kfree(cfg->bpf_ops);
259         kfree(cfg->bpf_name);
260 }
261 
262 static void tcf_bpf_prog_fill_cfg(const struct tcf_bpf *prog,
263                                   struct tcf_bpf_cfg *cfg)
264 {
265         cfg->is_ebpf = tcf_bpf_is_ebpf(prog);
266         /* updates to prog->filter are prevented, since it's called either
267          * with tcf lock or during final cleanup in rcu callback
268          */
269         cfg->filter = rcu_dereference_protected(prog->filter, 1);
270 
271         cfg->bpf_ops = prog->bpf_ops;
272         cfg->bpf_name = prog->bpf_name;
273 }
274 
275 static int tcf_bpf_init(struct net *net, struct nlattr *nla,
276                         struct nlattr *est, struct tc_action **act,
277                         int replace, int bind, bool rtnl_held,
278                         struct tcf_proto *tp, u32 flags,
279                         struct netlink_ext_ack *extack)
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_chain *goto_ch = NULL;
284         struct tcf_bpf_cfg cfg, old;
285         struct tc_act_bpf *parm;
286         struct tcf_bpf *prog;
287         bool is_bpf, is_ebpf;
288         int ret, res = 0;
289         u32 index;
290 
291         if (!nla)
292                 return -EINVAL;
293 
294         ret = nla_parse_nested_deprecated(tb, TCA_ACT_BPF_MAX, nla,
295                                           act_bpf_policy, NULL);
296         if (ret < 0)
297                 return ret;
298 
299         if (!tb[TCA_ACT_BPF_PARMS])
300                 return -EINVAL;
301 
302         parm = nla_data(tb[TCA_ACT_BPF_PARMS]);
303         index = parm->index;
304         ret = tcf_idr_check_alloc(tn, &index, act, bind);
305         if (!ret) {
306                 ret = tcf_idr_create(tn, index, est, act,
307                                      &act_bpf_ops, bind, true, 0);
308                 if (ret < 0) {
309                         tcf_idr_cleanup(tn, index);
310                         return ret;
311                 }
312 
313                 res = ACT_P_CREATED;
314         } else if (ret > 0) {
315                 /* Don't override defaults. */
316                 if (bind)
317                         return 0;
318 
319                 if (!replace) {
320                         tcf_idr_release(*act, bind);
321                         return -EEXIST;
322                 }
323         } else {
324                 return ret;
325         }
326 
327         ret = tcf_action_check_ctrlact(parm->action, tp, &goto_ch, extack);
328         if (ret < 0)
329                 goto release_idr;
330 
331         is_bpf = tb[TCA_ACT_BPF_OPS_LEN] && tb[TCA_ACT_BPF_OPS];
332         is_ebpf = tb[TCA_ACT_BPF_FD];
333 
334         if ((!is_bpf && !is_ebpf) || (is_bpf && is_ebpf)) {
335                 ret = -EINVAL;
336                 goto put_chain;
337         }
338 
339         memset(&cfg, 0, sizeof(cfg));
340 
341         ret = is_bpf ? tcf_bpf_init_from_ops(tb, &cfg) :
342                        tcf_bpf_init_from_efd(tb, &cfg);
343         if (ret < 0)
344                 goto put_chain;
345 
346         prog = to_bpf(*act);
347 
348         spin_lock_bh(&prog->tcf_lock);
349         if (res != ACT_P_CREATED)
350                 tcf_bpf_prog_fill_cfg(prog, &old);
351 
352         prog->bpf_ops = cfg.bpf_ops;
353         prog->bpf_name = cfg.bpf_name;
354 
355         if (cfg.bpf_num_ops)
356                 prog->bpf_num_ops = cfg.bpf_num_ops;
357 
358         goto_ch = tcf_action_set_ctrlact(*act, parm->action, goto_ch);
359         rcu_assign_pointer(prog->filter, cfg.filter);
360         spin_unlock_bh(&prog->tcf_lock);
361 
362         if (goto_ch)
363                 tcf_chain_put_by_act(goto_ch);
364 
365         if (res == ACT_P_CREATED) {
366                 tcf_idr_insert(tn, *act);
367         } else {
368                 /* make sure the program being replaced is no longer executing */
369                 synchronize_rcu();
370                 tcf_bpf_cfg_cleanup(&old);
371         }
372 
373         return res;
374 
375 put_chain:
376         if (goto_ch)
377                 tcf_chain_put_by_act(goto_ch);
378 
379 release_idr:
380         tcf_idr_release(*act, bind);
381         return ret;
382 }
383 
384 static void tcf_bpf_cleanup(struct tc_action *act)
385 {
386         struct tcf_bpf_cfg tmp;
387 
388         tcf_bpf_prog_fill_cfg(to_bpf(act), &tmp);
389         tcf_bpf_cfg_cleanup(&tmp);
390 }
391 
392 static int tcf_bpf_walker(struct net *net, struct sk_buff *skb,
393                           struct netlink_callback *cb, int type,
394                           const struct tc_action_ops *ops,
395                           struct netlink_ext_ack *extack)
396 {
397         struct tc_action_net *tn = net_generic(net, bpf_net_id);
398 
399         return tcf_generic_walker(tn, skb, cb, type, ops, extack);
400 }
401 
402 static int tcf_bpf_search(struct net *net, struct tc_action **a, u32 index)
403 {
404         struct tc_action_net *tn = net_generic(net, bpf_net_id);
405 
406         return tcf_idr_search(tn, a, index);
407 }
408 
409 static struct tc_action_ops act_bpf_ops __read_mostly = {
410         .kind           =       "bpf",
411         .id             =       TCA_ID_BPF,
412         .owner          =       THIS_MODULE,
413         .act            =       tcf_bpf_act,
414         .dump           =       tcf_bpf_dump,
415         .cleanup        =       tcf_bpf_cleanup,
416         .init           =       tcf_bpf_init,
417         .walk           =       tcf_bpf_walker,
418         .lookup         =       tcf_bpf_search,
419         .size           =       sizeof(struct tcf_bpf),
420 };
421 
422 static __net_init int bpf_init_net(struct net *net)
423 {
424         struct tc_action_net *tn = net_generic(net, bpf_net_id);
425 
426         return tc_action_net_init(net, tn, &act_bpf_ops);
427 }
428 
429 static void __net_exit bpf_exit_net(struct list_head *net_list)
430 {
431         tc_action_net_exit(net_list, bpf_net_id);
432 }
433 
434 static struct pernet_operations bpf_net_ops = {
435         .init = bpf_init_net,
436         .exit_batch = bpf_exit_net,
437         .id   = &bpf_net_id,
438         .size = sizeof(struct tc_action_net),
439 };
440 
441 static int __init bpf_init_module(void)
442 {
443         return tcf_register_action(&act_bpf_ops, &bpf_net_ops);
444 }
445 
446 static void __exit bpf_cleanup_module(void)
447 {
448         tcf_unregister_action(&act_bpf_ops, &bpf_net_ops);
449 }
450 
451 module_init(bpf_init_module);
452 module_exit(bpf_cleanup_module);
453 
454 MODULE_AUTHOR("Jiri Pirko <jiri@resnulli.us>");
455 MODULE_DESCRIPTION("TC BPF based action");
456 MODULE_LICENSE("GPL v2");
457 

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