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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         u16 bpf_num_ops;
 32         bool is_ebpf;
 33 };
 34 
 35 static unsigned int bpf_net_id;
 36 static struct tc_action_ops act_bpf_ops;
 37 
 38 static int tcf_bpf(struct sk_buff *skb, const struct tc_action *act,
 39                    struct tcf_result *res)
 40 {
 41         bool at_ingress = skb_at_tc_ingress(skb);
 42         struct tcf_bpf *prog = to_bpf(act);
 43         struct bpf_prog *filter;
 44         int action, filter_res;
 45 
 46         tcf_lastuse_update(&prog->tcf_tm);
 47         bstats_cpu_update(this_cpu_ptr(prog->common.cpu_bstats), skb);
 48 
 49         rcu_read_lock();
 50         filter = rcu_dereference(prog->filter);
 51         if (at_ingress) {
 52                 __skb_push(skb, skb->mac_len);
 53                 bpf_compute_data_end(skb);
 54                 filter_res = BPF_PROG_RUN(filter, skb);
 55                 __skb_pull(skb, skb->mac_len);
 56         } else {
 57                 bpf_compute_data_end(skb);
 58                 filter_res = BPF_PROG_RUN(filter, skb);
 59         }
 60         rcu_read_unlock();
 61 
 62         /* A BPF program may overwrite the default action opcode.
 63          * Similarly as in cls_bpf, if filter_res == -1 we use the
 64          * default action specified from tc.
 65          *
 66          * In case a different well-known TC_ACT opcode has been
 67          * returned, it will overwrite the default one.
 68          *
 69          * For everything else that is unkown, TC_ACT_UNSPEC is
 70          * returned.
 71          */
 72         switch (filter_res) {
 73         case TC_ACT_PIPE:
 74         case TC_ACT_RECLASSIFY:
 75         case TC_ACT_OK:
 76         case TC_ACT_REDIRECT:
 77                 action = filter_res;
 78                 break;
 79         case TC_ACT_SHOT:
 80                 action = filter_res;
 81                 qstats_drop_inc(this_cpu_ptr(prog->common.cpu_qstats));
 82                 break;
 83         case TC_ACT_UNSPEC:
 84                 action = prog->tcf_action;
 85                 break;
 86         default:
 87                 action = TC_ACT_UNSPEC;
 88                 break;
 89         }
 90 
 91         return action;
 92 }
 93 
 94 static bool tcf_bpf_is_ebpf(const struct tcf_bpf *prog)
 95 {
 96         return !prog->bpf_ops;
 97 }
 98 
 99 static int tcf_bpf_dump_bpf_info(const struct tcf_bpf *prog,
100                                  struct sk_buff *skb)
101 {
102         struct nlattr *nla;
103 
104         if (nla_put_u16(skb, TCA_ACT_BPF_OPS_LEN, prog->bpf_num_ops))
105                 return -EMSGSIZE;
106 
107         nla = nla_reserve(skb, TCA_ACT_BPF_OPS, prog->bpf_num_ops *
108                           sizeof(struct sock_filter));
109         if (nla == NULL)
110                 return -EMSGSIZE;
111 
112         memcpy(nla_data(nla), prog->bpf_ops, nla_len(nla));
113 
114         return 0;
115 }
116 
117 static int tcf_bpf_dump_ebpf_info(const struct tcf_bpf *prog,
118                                   struct sk_buff *skb)
119 {
120         struct nlattr *nla;
121 
122         if (prog->bpf_name &&
123             nla_put_string(skb, TCA_ACT_BPF_NAME, prog->bpf_name))
124                 return -EMSGSIZE;
125 
126         nla = nla_reserve(skb, TCA_ACT_BPF_TAG, sizeof(prog->filter->tag));
127         if (nla == NULL)
128                 return -EMSGSIZE;
129 
130         memcpy(nla_data(nla), prog->filter->tag, nla_len(nla));
131 
132         return 0;
133 }
134 
135 static int tcf_bpf_dump(struct sk_buff *skb, struct tc_action *act,
136                         int bind, int ref)
137 {
138         unsigned char *tp = skb_tail_pointer(skb);
139         struct tcf_bpf *prog = to_bpf(act);
140         struct tc_act_bpf opt = {
141                 .index   = prog->tcf_index,
142                 .refcnt  = prog->tcf_refcnt - ref,
143                 .bindcnt = prog->tcf_bindcnt - bind,
144                 .action  = prog->tcf_action,
145         };
146         struct tcf_t tm;
147         int ret;
148 
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         return skb->len;
165 
166 nla_put_failure:
167         nlmsg_trim(skb, tp);
168         return -1;
169 }
170 
171 static const struct nla_policy act_bpf_policy[TCA_ACT_BPF_MAX + 1] = {
172         [TCA_ACT_BPF_PARMS]     = { .len = sizeof(struct tc_act_bpf) },
173         [TCA_ACT_BPF_FD]        = { .type = NLA_U32 },
174         [TCA_ACT_BPF_NAME]      = { .type = NLA_NUL_STRING,
175                                     .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_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         if (cfg->is_ebpf)
250                 bpf_prog_put(cfg->filter);
251         else
252                 bpf_prog_destroy(cfg->filter);
253 
254         kfree(cfg->bpf_ops);
255         kfree(cfg->bpf_name);
256 }
257 
258 static void tcf_bpf_prog_fill_cfg(const struct tcf_bpf *prog,
259                                   struct tcf_bpf_cfg *cfg)
260 {
261         cfg->is_ebpf = tcf_bpf_is_ebpf(prog);
262         /* updates to prog->filter are prevented, since it's called either
263          * with rtnl lock or during final cleanup in rcu callback
264          */
265         cfg->filter = rcu_dereference_protected(prog->filter, 1);
266 
267         cfg->bpf_ops = prog->bpf_ops;
268         cfg->bpf_name = prog->bpf_name;
269 }
270 
271 static int tcf_bpf_init(struct net *net, struct nlattr *nla,
272                         struct nlattr *est, struct tc_action **act,
273                         int replace, int bind)
274 {
275         struct tc_action_net *tn = net_generic(net, bpf_net_id);
276         struct nlattr *tb[TCA_ACT_BPF_MAX + 1];
277         struct tcf_bpf_cfg cfg, old;
278         struct tc_act_bpf *parm;
279         struct tcf_bpf *prog;
280         bool is_bpf, is_ebpf;
281         int ret, res = 0;
282 
283         if (!nla)
284                 return -EINVAL;
285 
286         ret = nla_parse_nested(tb, TCA_ACT_BPF_MAX, nla, act_bpf_policy);
287         if (ret < 0)
288                 return ret;
289 
290         if (!tb[TCA_ACT_BPF_PARMS])
291                 return -EINVAL;
292 
293         parm = nla_data(tb[TCA_ACT_BPF_PARMS]);
294 
295         if (!tcf_hash_check(tn, parm->index, act, bind)) {
296                 ret = tcf_hash_create(tn, parm->index, est, act,
297                                       &act_bpf_ops, bind, true);
298                 if (ret < 0)
299                         return ret;
300 
301                 res = ACT_P_CREATED;
302         } else {
303                 /* Don't override defaults. */
304                 if (bind)
305                         return 0;
306 
307                 tcf_hash_release(*act, bind);
308                 if (!replace)
309                         return -EEXIST;
310         }
311 
312         is_bpf = tb[TCA_ACT_BPF_OPS_LEN] && tb[TCA_ACT_BPF_OPS];
313         is_ebpf = tb[TCA_ACT_BPF_FD];
314 
315         if ((!is_bpf && !is_ebpf) || (is_bpf && is_ebpf)) {
316                 ret = -EINVAL;
317                 goto out;
318         }
319 
320         memset(&cfg, 0, sizeof(cfg));
321 
322         ret = is_bpf ? tcf_bpf_init_from_ops(tb, &cfg) :
323                        tcf_bpf_init_from_efd(tb, &cfg);
324         if (ret < 0)
325                 goto out;
326 
327         prog = to_bpf(*act);
328         ASSERT_RTNL();
329 
330         if (res != ACT_P_CREATED)
331                 tcf_bpf_prog_fill_cfg(prog, &old);
332 
333         prog->bpf_ops = cfg.bpf_ops;
334         prog->bpf_name = cfg.bpf_name;
335 
336         if (cfg.bpf_num_ops)
337                 prog->bpf_num_ops = cfg.bpf_num_ops;
338 
339         prog->tcf_action = parm->action;
340         rcu_assign_pointer(prog->filter, cfg.filter);
341 
342         if (res == ACT_P_CREATED) {
343                 tcf_hash_insert(tn, *act);
344         } else {
345                 /* make sure the program being replaced is no longer executing */
346                 synchronize_rcu();
347                 tcf_bpf_cfg_cleanup(&old);
348         }
349 
350         return res;
351 out:
352         if (res == ACT_P_CREATED)
353                 tcf_hash_cleanup(*act, est);
354 
355         return ret;
356 }
357 
358 static void tcf_bpf_cleanup(struct tc_action *act, int bind)
359 {
360         struct tcf_bpf_cfg tmp;
361 
362         tcf_bpf_prog_fill_cfg(to_bpf(act), &tmp);
363         tcf_bpf_cfg_cleanup(&tmp);
364 }
365 
366 static int tcf_bpf_walker(struct net *net, struct sk_buff *skb,
367                           struct netlink_callback *cb, int type,
368                           const struct tc_action_ops *ops)
369 {
370         struct tc_action_net *tn = net_generic(net, bpf_net_id);
371 
372         return tcf_generic_walker(tn, skb, cb, type, ops);
373 }
374 
375 static int tcf_bpf_search(struct net *net, struct tc_action **a, u32 index)
376 {
377         struct tc_action_net *tn = net_generic(net, bpf_net_id);
378 
379         return tcf_hash_search(tn, a, index);
380 }
381 
382 static struct tc_action_ops act_bpf_ops __read_mostly = {
383         .kind           =       "bpf",
384         .type           =       TCA_ACT_BPF,
385         .owner          =       THIS_MODULE,
386         .act            =       tcf_bpf,
387         .dump           =       tcf_bpf_dump,
388         .cleanup        =       tcf_bpf_cleanup,
389         .init           =       tcf_bpf_init,
390         .walk           =       tcf_bpf_walker,
391         .lookup         =       tcf_bpf_search,
392         .size           =       sizeof(struct tcf_bpf),
393 };
394 
395 static __net_init int bpf_init_net(struct net *net)
396 {
397         struct tc_action_net *tn = net_generic(net, bpf_net_id);
398 
399         return tc_action_net_init(tn, &act_bpf_ops, BPF_TAB_MASK);
400 }
401 
402 static void __net_exit bpf_exit_net(struct net *net)
403 {
404         struct tc_action_net *tn = net_generic(net, bpf_net_id);
405 
406         tc_action_net_exit(tn);
407 }
408 
409 static struct pernet_operations bpf_net_ops = {
410         .init = bpf_init_net,
411         .exit = bpf_exit_net,
412         .id   = &bpf_net_id,
413         .size = sizeof(struct tc_action_net),
414 };
415 
416 static int __init bpf_init_module(void)
417 {
418         return tcf_register_action(&act_bpf_ops, &bpf_net_ops);
419 }
420 
421 static void __exit bpf_cleanup_module(void)
422 {
423         tcf_unregister_action(&act_bpf_ops, &bpf_net_ops);
424 }
425 
426 module_init(bpf_init_module);
427 module_exit(bpf_cleanup_module);
428 
429 MODULE_AUTHOR("Jiri Pirko <jiri@resnulli.us>");
430 MODULE_DESCRIPTION("TC BPF based action");
431 MODULE_LICENSE("GPL v2");
432 

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