net/sched/cls_bpf.c

   1 /*
   2  * Berkeley Packet Filter based traffic classifier
   3  *
   4  * Might be used to classify traffic through flexible, user-defined and
   5  * possibly JIT-ed BPF filters for traffic control as an alternative to
   6  * ematches.
   7  *
   8  * (C) 2013 Daniel Borkmann <dborkman@redhat.com>
   9  *
  10  * This program is free software; you can redistribute it and/or modify
  11  * it under the terms of the GNU General Public License version 2 as
  12  * published by the Free Software Foundation.
  13  */
  14
  15 #include <linux/module.h>
  16 #include <linux/types.h>
  17 #include <linux/skbuff.h>
  18 #include <linux/filter.h>
  19 #include <linux/bpf.h>
  20
  21 #include <net/rtnetlink.h>
  22 #include <net/pkt_cls.h>
  23 #include <net/sock.h>
  24
  25 MODULE_LICENSE("GPL");
  26 MODULE_AUTHOR("Daniel Borkmann <dborkman@redhat.com>");
  27 MODULE_DESCRIPTION("TC BPF based classifier");
  28
  29 #define CLS_BPF_NAME_LEN        256
  30
  31 struct cls_bpf_head {
  32         struct list_head plist;
  33         u32 hgen;
  34         struct rcu_head rcu;
  35 };
  36
  37 struct cls_bpf_prog {
  38         struct bpf_prog *filter;
  39         struct list_head link;
  40         struct tcf_result res;
  41         bool exts_integrated;
  42         struct tcf_exts exts;
  43         u32 handle;
  44         union {
  45                 u32 bpf_fd;
  46                 u16 bpf_num_ops;
  47         };
  48         struct sock_filter *bpf_ops;
  49         const char *bpf_name;
  50         struct tcf_proto *tp;
  51         struct rcu_head rcu;
  52 };
  53
  54 static const struct nla_policy bpf_policy[TCA_BPF_MAX + 1] = {
  55         [TCA_BPF_CLASSID]       = { .type = NLA_U32 },
  56         [TCA_BPF_FLAGS]         = { .type = NLA_U32 },
  57         [TCA_BPF_FD]            = { .type = NLA_U32 },
  58         [TCA_BPF_NAME]          = { .type = NLA_NUL_STRING, .len = CLS_BPF_NAME_LEN },
  59         [TCA_BPF_OPS_LEN]       = { .type = NLA_U16 },
  60         [TCA_BPF_OPS]           = { .type = NLA_BINARY,
  61                                     .len = sizeof(struct sock_filter) * BPF_MAXINSNS },
  62 };
  63
  64 static int cls_bpf_exec_opcode(int code)
  65 {
  66         switch (code) {
  67         case TC_ACT_OK:
  68         case TC_ACT_SHOT:
  69         case TC_ACT_STOLEN:
  70         case TC_ACT_REDIRECT:
  71         case TC_ACT_UNSPEC:
  72                 return code;
  73         default:
  74                 return TC_ACT_UNSPEC;
  75         }
  76 }
  77
  78 static int cls_bpf_classify(struct sk_buff *skb, const struct tcf_proto *tp,
  79                             struct tcf_result *res)
  80 {
  81         struct cls_bpf_head *head = rcu_dereference_bh(tp->root);
  82         struct cls_bpf_prog *prog;
  83 #ifdef CONFIG_NET_CLS_ACT
  84         bool at_ingress = G_TC_AT(skb->tc_verd) & AT_INGRESS;
  85 #else
  86         bool at_ingress = false;
  87 #endif
  88         int ret = -1;
  89
  90         if (unlikely(!skb_mac_header_was_set(skb)))
  91                 return -1;
  92
  93         /* Needed here for accessing maps. */
  94         rcu_read_lock();
  95         list_for_each_entry_rcu(prog, &head->plist, link) {
  96                 int filter_res;
  97
  98                 qdisc_skb_cb(skb)->tc_classid = prog->res.classid;
  99
 100                 if (at_ingress) {
 101                         /* It is safe to push/pull even if skb_shared() */
 102                         __skb_push(skb, skb->mac_len);
 103                         filter_res = BPF_PROG_RUN(prog->filter, skb);
 104                         __skb_pull(skb, skb->mac_len);
 105                 } else {
 106                         filter_res = BPF_PROG_RUN(prog->filter, skb);
 107                 }
 108
 109                 if (prog->exts_integrated) {
 110                         res->class = prog->res.class;
 111                         res->classid = qdisc_skb_cb(skb)->tc_classid;
 112
 113                         ret = cls_bpf_exec_opcode(filter_res);
 114                         if (ret == TC_ACT_UNSPEC)
 115                                 continue;
 116                         break;
 117                 }
 118
 119                 if (filter_res == 0)
 120                         continue;
 121
 122                 *res = prog->res;
 123                 if (filter_res != -1)
 124                         res->classid = filter_res;
 125
 126                 ret = tcf_exts_exec(skb, &prog->exts, res);
 127                 if (ret < 0)
 128                         continue;
 129
 130                 break;
 131         }
 132         rcu_read_unlock();
 133
 134         return ret;
 135 }
 136
 137 static bool cls_bpf_is_ebpf(const struct cls_bpf_prog *prog)
 138 {
 139         return !prog->bpf_ops;
 140 }
 141
 142 static int cls_bpf_init(struct tcf_proto *tp)
 143 {
 144         struct cls_bpf_head *head;
 145
 146         head = kzalloc(sizeof(*head), GFP_KERNEL);
 147         if (head == NULL)
 148                 return -ENOBUFS;
 149
 150         INIT_LIST_HEAD_RCU(&head->plist);
 151         rcu_assign_pointer(tp->root, head);
 152
 153         return 0;
 154 }
 155
 156 static void cls_bpf_delete_prog(struct tcf_proto *tp, struct cls_bpf_prog *prog)
 157 {
 158         tcf_exts_destroy(&prog->exts);
 159
 160         if (cls_bpf_is_ebpf(prog))
 161                 bpf_prog_put(prog->filter);
 162         else
 163                 bpf_prog_destroy(prog->filter);
 164
 165         kfree(prog->bpf_name);
 166         kfree(prog->bpf_ops);
 167         kfree(prog);
 168 }
 169
 170 static void __cls_bpf_delete_prog(struct rcu_head *rcu)
 171 {
 172         struct cls_bpf_prog *prog = container_of(rcu, struct cls_bpf_prog, rcu);
 173
 174         cls_bpf_delete_prog(prog->tp, prog);
 175 }
 176
 177 static int cls_bpf_delete(struct tcf_proto *tp, unsigned long arg)
 178 {
 179         struct cls_bpf_prog *prog = (struct cls_bpf_prog *) arg;
 180
 181         list_del_rcu(&prog->link);
 182         tcf_unbind_filter(tp, &prog->res);
 183         call_rcu(&prog->rcu, __cls_bpf_delete_prog);
 184
 185         return 0;
 186 }
 187
 188 static bool cls_bpf_destroy(struct tcf_proto *tp, bool force)
 189 {
 190         struct cls_bpf_head *head = rtnl_dereference(tp->root);
 191         struct cls_bpf_prog *prog, *tmp;
 192
 193         if (!force && !list_empty(&head->plist))
 194                 return false;
 195
 196         list_for_each_entry_safe(prog, tmp, &head->plist, link) {
 197                 list_del_rcu(&prog->link);
 198                 tcf_unbind_filter(tp, &prog->res);
 199                 call_rcu(&prog->rcu, __cls_bpf_delete_prog);
 200         }
 201
 202         RCU_INIT_POINTER(tp->root, NULL);
 203         kfree_rcu(head, rcu);
 204         return true;
 205 }
 206
 207 static unsigned long cls_bpf_get(struct tcf_proto *tp, u32 handle)
 208 {
 209         struct cls_bpf_head *head = rtnl_dereference(tp->root);
 210         struct cls_bpf_prog *prog;
 211         unsigned long ret = 0UL;
 212
 213         if (head == NULL)
 214                 return 0UL;
 215
 216         list_for_each_entry(prog, &head->plist, link) {
 217                 if (prog->handle == handle) {
 218                         ret = (unsigned long) prog;
 219                         break;
 220                 }
 221         }
 222
 223         return ret;
 224 }
 225
 226 static int cls_bpf_prog_from_ops(struct nlattr **tb, struct cls_bpf_prog *prog)
 227 {
 228         struct sock_filter *bpf_ops;
 229         struct sock_fprog_kern fprog_tmp;
 230         struct bpf_prog *fp;
 231         u16 bpf_size, bpf_num_ops;
 232         int ret;
 233
 234         bpf_num_ops = nla_get_u16(tb[TCA_BPF_OPS_LEN]);
 235         if (bpf_num_ops > BPF_MAXINSNS || bpf_num_ops == 0)
 236                 return -EINVAL;
 237
 238         bpf_size = bpf_num_ops * sizeof(*bpf_ops);
 239         if (bpf_size != nla_len(tb[TCA_BPF_OPS]))
 240                 return -EINVAL;
 241
 242         bpf_ops = kzalloc(bpf_size, GFP_KERNEL);
 243         if (bpf_ops == NULL)
 244                 return -ENOMEM;
 245
 246         memcpy(bpf_ops, nla_data(tb[TCA_BPF_OPS]), bpf_size);
 247
 248         fprog_tmp.len = bpf_num_ops;
 249         fprog_tmp.filter = bpf_ops;
 250
 251         ret = bpf_prog_create(&fp, &fprog_tmp);
 252         if (ret < 0) {
 253                 kfree(bpf_ops);
 254                 return ret;
 255         }
 256
 257         prog->bpf_ops = bpf_ops;
 258         prog->bpf_num_ops = bpf_num_ops;
 259         prog->bpf_name = NULL;
 260         prog->filter = fp;
 261
 262         return 0;
 263 }
 264
 265 static int cls_bpf_prog_from_efd(struct nlattr **tb, struct cls_bpf_prog *prog,
 266                                  const struct tcf_proto *tp)
 267 {
 268         struct bpf_prog *fp;
 269         char *name = NULL;
 270         u32 bpf_fd;
 271
 272         bpf_fd = nla_get_u32(tb[TCA_BPF_FD]);
 273
 274         fp = bpf_prog_get(bpf_fd);
 275         if (IS_ERR(fp))
 276                 return PTR_ERR(fp);
 277
 278         if (fp->type != BPF_PROG_TYPE_SCHED_CLS) {
 279                 bpf_prog_put(fp);
 280                 return -EINVAL;
 281         }
 282
 283         if (tb[TCA_BPF_NAME]) {
 284                 name = kmemdup(nla_data(tb[TCA_BPF_NAME]),
 285                                nla_len(tb[TCA_BPF_NAME]),
 286                                GFP_KERNEL);
 287                 if (!name) {
 288                         bpf_prog_put(fp);
 289                         return -ENOMEM;
 290                 }
 291         }
 292
 293         prog->bpf_ops = NULL;
 294         prog->bpf_fd = bpf_fd;
 295         prog->bpf_name = name;
 296         prog->filter = fp;
 297
 298         if (fp->dst_needed)
 299                 netif_keep_dst(qdisc_dev(tp->q));
 300
 301         return 0;
 302 }
 303
 304 static int cls_bpf_modify_existing(struct net *net, struct tcf_proto *tp,
 305                                    struct cls_bpf_prog *prog,
 306                                    unsigned long base, struct nlattr **tb,
 307                                    struct nlattr *est, bool ovr)
 308 {
 309         bool is_bpf, is_ebpf, have_exts = false;
 310         struct tcf_exts exts;
 311         int ret;
 312
 313         is_bpf = tb[TCA_BPF_OPS_LEN] && tb[TCA_BPF_OPS];
 314         is_ebpf = tb[TCA_BPF_FD];
 315         if ((!is_bpf && !is_ebpf) || (is_bpf && is_ebpf))
 316                 return -EINVAL;
 317
 318         tcf_exts_init(&exts, TCA_BPF_ACT, TCA_BPF_POLICE);
 319         ret = tcf_exts_validate(net, tp, tb, est, &exts, ovr);
 320         if (ret < 0)
 321                 return ret;
 322
 323         if (tb[TCA_BPF_FLAGS]) {
 324                 u32 bpf_flags = nla_get_u32(tb[TCA_BPF_FLAGS]);
 325
 326                 if (bpf_flags & ~TCA_BPF_FLAG_ACT_DIRECT) {
 327                         tcf_exts_destroy(&exts);
 328                         return -EINVAL;
 329                 }
 330
 331                 have_exts = bpf_flags & TCA_BPF_FLAG_ACT_DIRECT;
 332         }
 333
 334         prog->exts_integrated = have_exts;
 335
 336         ret = is_bpf ? cls_bpf_prog_from_ops(tb, prog) :
 337                        cls_bpf_prog_from_efd(tb, prog, tp);
 338         if (ret < 0) {
 339                 tcf_exts_destroy(&exts);
 340                 return ret;
 341         }
 342
 343         if (tb[TCA_BPF_CLASSID]) {
 344                 prog->res.classid = nla_get_u32(tb[TCA_BPF_CLASSID]);
 345                 tcf_bind_filter(tp, &prog->res, base);
 346         }
 347
 348         tcf_exts_change(tp, &prog->exts, &exts);
 349         return 0;
 350 }
 351
 352 static u32 cls_bpf_grab_new_handle(struct tcf_proto *tp,
 353                                    struct cls_bpf_head *head)
 354 {
 355         unsigned int i = 0x80000000;
 356         u32 handle;
 357
 358         do {
 359                 if (++head->hgen == 0x7FFFFFFF)
 360                         head->hgen = 1;
 361         } while (--i > 0 && cls_bpf_get(tp, head->hgen));
 362
 363         if (unlikely(i == 0)) {
 364                 pr_err("Insufficient number of handles\n");
 365                 handle = 0;
 366         } else {
 367                 handle = head->hgen;
 368         }
 369
 370         return handle;
 371 }
 372
 373 static int cls_bpf_change(struct net *net, struct sk_buff *in_skb,
 374                           struct tcf_proto *tp, unsigned long base,
 375                           u32 handle, struct nlattr **tca,
 376                           unsigned long *arg, bool ovr)
 377 {
 378         struct cls_bpf_head *head = rtnl_dereference(tp->root);
 379         struct cls_bpf_prog *oldprog = (struct cls_bpf_prog *) *arg;
 380         struct nlattr *tb[TCA_BPF_MAX + 1];
 381         struct cls_bpf_prog *prog;
 382         int ret;
 383
 384         if (tca[TCA_OPTIONS] == NULL)
 385                 return -EINVAL;
 386
 387         ret = nla_parse_nested(tb, TCA_BPF_MAX, tca[TCA_OPTIONS], bpf_policy);
 388         if (ret < 0)
 389                 return ret;
 390
 391         prog = kzalloc(sizeof(*prog), GFP_KERNEL);
 392         if (!prog)
 393                 return -ENOBUFS;
 394
 395         tcf_exts_init(&prog->exts, TCA_BPF_ACT, TCA_BPF_POLICE);
 396
 397         if (oldprog) {
 398                 if (handle && oldprog->handle != handle) {
 399                         ret = -EINVAL;
 400                         goto errout;
 401                 }
 402         }
 403
 404         if (handle == 0)
 405                 prog->handle = cls_bpf_grab_new_handle(tp, head);
 406         else
 407                 prog->handle = handle;
 408         if (prog->handle == 0) {
 409                 ret = -EINVAL;
 410                 goto errout;
 411         }
 412
 413         ret = cls_bpf_modify_existing(net, tp, prog, base, tb, tca[TCA_RATE], ovr);
 414         if (ret < 0)
 415                 goto errout;
 416
 417         if (oldprog) {
 418                 list_replace_rcu(&oldprog->link, &prog->link);
 419                 tcf_unbind_filter(tp, &oldprog->res);
 420                 call_rcu(&oldprog->rcu, __cls_bpf_delete_prog);
 421         } else {
 422                 list_add_rcu(&prog->link, &head->plist);
 423         }
 424
 425         *arg = (unsigned long) prog;
 426         return 0;
 427 errout:
 428         kfree(prog);
 429
 430         return ret;
 431 }
 432
 433 static int cls_bpf_dump_bpf_info(const struct cls_bpf_prog *prog,
 434                                  struct sk_buff *skb)
 435 {
 436         struct nlattr *nla;
 437
 438         if (nla_put_u16(skb, TCA_BPF_OPS_LEN, prog->bpf_num_ops))
 439                 return -EMSGSIZE;
 440
 441         nla = nla_reserve(skb, TCA_BPF_OPS, prog->bpf_num_ops *
 442                           sizeof(struct sock_filter));
 443         if (nla == NULL)
 444                 return -EMSGSIZE;
 445
 446         memcpy(nla_data(nla), prog->bpf_ops, nla_len(nla));
 447
 448         return 0;
 449 }
 450
 451 static int cls_bpf_dump_ebpf_info(const struct cls_bpf_prog *prog,
 452                                   struct sk_buff *skb)
 453 {
 454         if (nla_put_u32(skb, TCA_BPF_FD, prog->bpf_fd))
 455                 return -EMSGSIZE;
 456
 457         if (prog->bpf_name &&
 458             nla_put_string(skb, TCA_BPF_NAME, prog->bpf_name))
 459                 return -EMSGSIZE;
 460
 461         return 0;
 462 }
 463
 464 static int cls_bpf_dump(struct net *net, struct tcf_proto *tp, unsigned long fh,
 465                         struct sk_buff *skb, struct tcmsg *tm)
 466 {
 467         struct cls_bpf_prog *prog = (struct cls_bpf_prog *) fh;
 468         struct nlattr *nest;
 469         u32 bpf_flags = 0;
 470         int ret;
 471
 472         if (prog == NULL)
 473                 return skb->len;
 474
 475         tm->tcm_handle = prog->handle;
 476
 477         nest = nla_nest_start(skb, TCA_OPTIONS);
 478         if (nest == NULL)
 479                 goto nla_put_failure;
 480
 481         if (prog->res.classid &&
 482             nla_put_u32(skb, TCA_BPF_CLASSID, prog->res.classid))
 483                 goto nla_put_failure;
 484
 485         if (cls_bpf_is_ebpf(prog))
 486                 ret = cls_bpf_dump_ebpf_info(prog, skb);
 487         else
 488                 ret = cls_bpf_dump_bpf_info(prog, skb);
 489         if (ret)
 490                 goto nla_put_failure;
 491
 492         if (tcf_exts_dump(skb, &prog->exts) < 0)
 493                 goto nla_put_failure;
 494
 495         if (prog->exts_integrated)
 496                 bpf_flags |= TCA_BPF_FLAG_ACT_DIRECT;
 497         if (bpf_flags && nla_put_u32(skb, TCA_BPF_FLAGS, bpf_flags))
 498                 goto nla_put_failure;
 499
 500         nla_nest_end(skb, nest);
 501
 502         if (tcf_exts_dump_stats(skb, &prog->exts) < 0)
 503                 goto nla_put_failure;
 504
 505         return skb->len;
 506
 507 nla_put_failure:
 508         nla_nest_cancel(skb, nest);
 509         return -1;
 510 }
 511
 512 static void cls_bpf_walk(struct tcf_proto *tp, struct tcf_walker *arg)
 513 {
 514         struct cls_bpf_head *head = rtnl_dereference(tp->root);
 515         struct cls_bpf_prog *prog;
 516
 517         list_for_each_entry(prog, &head->plist, link) {
 518                 if (arg->count < arg->skip)
 519                         goto skip;
 520                 if (arg->fn(tp, (unsigned long) prog, arg) < 0) {
 521                         arg->stop = 1;
 522                         break;
 523                 }
 524 skip:
 525                 arg->count++;
 526         }
 527 }
 528
 529 static struct tcf_proto_ops cls_bpf_ops __read_mostly = {
 530         .kind           =       "bpf",
 531         .owner          =       THIS_MODULE,
 532         .classify       =       cls_bpf_classify,
 533         .init           =       cls_bpf_init,
 534         .destroy        =       cls_bpf_destroy,
 535         .get            =       cls_bpf_get,
 536         .change         =       cls_bpf_change,
 537         .delete         =       cls_bpf_delete,
 538         .walk           =       cls_bpf_walk,
 539         .dump           =       cls_bpf_dump,
 540 };
 541
 542 static int __init cls_bpf_init_mod(void)
 543 {
 544         return register_tcf_proto_ops(&cls_bpf_ops);
 545 }
 546
 547 static void __exit cls_bpf_exit_mod(void)
 548 {
 549         unregister_tcf_proto_ops(&cls_bpf_ops);
 550 }
 551
 552 module_init(cls_bpf_init_mod);
 553 module_exit(cls_bpf_exit_mod);