net/sched/act_bpf.c

   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         u32 bpf_fd;
  32         u16 bpf_num_ops;
  33         bool is_ebpf;
  34 };
  35
  36 static int tcf_bpf(struct sk_buff *skb, const struct tc_action *act,
  37                    struct tcf_result *res)
  38 {
  39         struct tcf_bpf *prog = act->priv;
  40         struct bpf_prog *filter;
  41         int action, filter_res;
  42         bool at_ingress = G_TC_AT(skb->tc_verd) & AT_INGRESS;
  43
  44         if (unlikely(!skb_mac_header_was_set(skb)))
  45                 return TC_ACT_UNSPEC;
  46
  47         tcf_lastuse_update(&prog->tcf_tm);
  48         bstats_cpu_update(this_cpu_ptr(prog->common.cpu_bstats), skb);
  49
  50         rcu_read_lock();
  51         filter = rcu_dereference(prog->filter);
  52         if (at_ingress) {
  53                 __skb_push(skb, skb->mac_len);
  54                 filter_res = BPF_PROG_RUN(filter, skb);
  55                 __skb_pull(skb, skb->mac_len);
  56         } else {
  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                 action = filter_res;
  76                 break;
  77         case TC_ACT_SHOT:
  78                 action = filter_res;
  79                 qstats_drop_inc(this_cpu_ptr(prog->common.cpu_qstats));
  80                 break;
  81         case TC_ACT_UNSPEC:
  82                 action = prog->tcf_action;
  83                 break;
  84         default:
  85                 action = TC_ACT_UNSPEC;
  86                 break;
  87         }
  88
  89         return action;
  90 }
  91
  92 static bool tcf_bpf_is_ebpf(const struct tcf_bpf *prog)
  93 {
  94         return !prog->bpf_ops;
  95 }
  96
  97 static int tcf_bpf_dump_bpf_info(const struct tcf_bpf *prog,
  98                                  struct sk_buff *skb)
  99 {
 100         struct nlattr *nla;
 101
 102         if (nla_put_u16(skb, TCA_ACT_BPF_OPS_LEN, prog->bpf_num_ops))
 103                 return -EMSGSIZE;
 104
 105         nla = nla_reserve(skb, TCA_ACT_BPF_OPS, prog->bpf_num_ops *
 106                           sizeof(struct sock_filter));
 107         if (nla == NULL)
 108                 return -EMSGSIZE;
 109
 110         memcpy(nla_data(nla), prog->bpf_ops, nla_len(nla));
 111
 112         return 0;
 113 }
 114
 115 static int tcf_bpf_dump_ebpf_info(const struct tcf_bpf *prog,
 116                                   struct sk_buff *skb)
 117 {
 118         if (nla_put_u32(skb, TCA_ACT_BPF_FD, prog->bpf_fd))
 119                 return -EMSGSIZE;
 120
 121         if (prog->bpf_name &&
 122             nla_put_string(skb, TCA_ACT_BPF_NAME, prog->bpf_name))
 123                 return -EMSGSIZE;
 124
 125         return 0;
 126 }
 127
 128 static int tcf_bpf_dump(struct sk_buff *skb, struct tc_action *act,
 129                         int bind, int ref)
 130 {
 131         unsigned char *tp = skb_tail_pointer(skb);
 132         struct tcf_bpf *prog = act->priv;
 133         struct tc_act_bpf opt = {
 134                 .index   = prog->tcf_index,
 135                 .refcnt  = prog->tcf_refcnt - ref,
 136                 .bindcnt = prog->tcf_bindcnt - bind,
 137                 .action  = prog->tcf_action,
 138         };
 139         struct tcf_t tm;
 140         int ret;
 141
 142         if (nla_put(skb, TCA_ACT_BPF_PARMS, sizeof(opt), &opt))
 143                 goto nla_put_failure;
 144
 145         if (tcf_bpf_is_ebpf(prog))
 146                 ret = tcf_bpf_dump_ebpf_info(prog, skb);
 147         else
 148                 ret = tcf_bpf_dump_bpf_info(prog, skb);
 149         if (ret)
 150                 goto nla_put_failure;
 151
 152         tm.install = jiffies_to_clock_t(jiffies - prog->tcf_tm.install);
 153         tm.lastuse = jiffies_to_clock_t(jiffies - prog->tcf_tm.lastuse);
 154         tm.expires = jiffies_to_clock_t(prog->tcf_tm.expires);
 155
 156         if (nla_put(skb, TCA_ACT_BPF_TM, sizeof(tm), &tm))
 157                 goto nla_put_failure;
 158
 159         return skb->len;
 160
 161 nla_put_failure:
 162         nlmsg_trim(skb, tp);
 163         return -1;
 164 }
 165
 166 static const struct nla_policy act_bpf_policy[TCA_ACT_BPF_MAX + 1] = {
 167         [TCA_ACT_BPF_PARMS]     = { .len = sizeof(struct tc_act_bpf) },
 168         [TCA_ACT_BPF_FD]        = { .type = NLA_U32 },
 169         [TCA_ACT_BPF_NAME]      = { .type = NLA_NUL_STRING, .len = ACT_BPF_NAME_LEN },
 170         [TCA_ACT_BPF_OPS_LEN]   = { .type = NLA_U16 },
 171         [TCA_ACT_BPF_OPS]       = { .type = NLA_BINARY,
 172                                     .len = sizeof(struct sock_filter) * BPF_MAXINSNS },
 173 };
 174
 175 static int tcf_bpf_init_from_ops(struct nlattr **tb, struct tcf_bpf_cfg *cfg)
 176 {
 177         struct sock_filter *bpf_ops;
 178         struct sock_fprog_kern fprog_tmp;
 179         struct bpf_prog *fp;
 180         u16 bpf_size, bpf_num_ops;
 181         int ret;
 182
 183         bpf_num_ops = nla_get_u16(tb[TCA_ACT_BPF_OPS_LEN]);
 184         if (bpf_num_ops > BPF_MAXINSNS || bpf_num_ops == 0)
 185                 return -EINVAL;
 186
 187         bpf_size = bpf_num_ops * sizeof(*bpf_ops);
 188         if (bpf_size != nla_len(tb[TCA_ACT_BPF_OPS]))
 189                 return -EINVAL;
 190
 191         bpf_ops = kzalloc(bpf_size, GFP_KERNEL);
 192         if (bpf_ops == NULL)
 193                 return -ENOMEM;
 194
 195         memcpy(bpf_ops, nla_data(tb[TCA_ACT_BPF_OPS]), bpf_size);
 196
 197         fprog_tmp.len = bpf_num_ops;
 198         fprog_tmp.filter = bpf_ops;
 199
 200         ret = bpf_prog_create(&fp, &fprog_tmp);
 201         if (ret < 0) {
 202                 kfree(bpf_ops);
 203                 return ret;
 204         }
 205
 206         cfg->bpf_ops = bpf_ops;
 207         cfg->bpf_num_ops = bpf_num_ops;
 208         cfg->filter = fp;
 209         cfg->is_ebpf = false;
 210
 211         return 0;
 212 }
 213
 214 static int tcf_bpf_init_from_efd(struct nlattr **tb, struct tcf_bpf_cfg *cfg)
 215 {
 216         struct bpf_prog *fp;
 217         char *name = NULL;
 218         u32 bpf_fd;
 219
 220         bpf_fd = nla_get_u32(tb[TCA_ACT_BPF_FD]);
 221
 222         fp = bpf_prog_get(bpf_fd);
 223         if (IS_ERR(fp))
 224                 return PTR_ERR(fp);
 225
 226         if (fp->type != BPF_PROG_TYPE_SCHED_ACT) {
 227                 bpf_prog_put(fp);
 228                 return -EINVAL;
 229         }
 230
 231         if (tb[TCA_ACT_BPF_NAME]) {
 232                 name = kmemdup(nla_data(tb[TCA_ACT_BPF_NAME]),
 233                                nla_len(tb[TCA_ACT_BPF_NAME]),
 234                                GFP_KERNEL);
 235                 if (!name) {
 236                         bpf_prog_put(fp);
 237                         return -ENOMEM;
 238                 }
 239         }
 240
 241         cfg->bpf_fd = bpf_fd;
 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         if (cfg->is_ebpf)
 252                 bpf_prog_put(cfg->filter);
 253         else
 254                 bpf_prog_destroy(cfg->filter);
 255
 256         kfree(cfg->bpf_ops);
 257         kfree(cfg->bpf_name);
 258 }
 259
 260 static void tcf_bpf_prog_fill_cfg(const struct tcf_bpf *prog,
 261                                   struct tcf_bpf_cfg *cfg)
 262 {
 263         cfg->is_ebpf = tcf_bpf_is_ebpf(prog);
 264         /* updates to prog->filter are prevented, since it's called either
 265          * with rtnl lock or during final cleanup in rcu callback
 266          */
 267         cfg->filter = rcu_dereference_protected(prog->filter, 1);
 268
 269         cfg->bpf_ops = prog->bpf_ops;
 270         cfg->bpf_name = prog->bpf_name;
 271 }
 272
 273 static int tcf_bpf_init(struct net *net, struct nlattr *nla,
 274                         struct nlattr *est, struct tc_action *act,
 275                         int replace, int bind)
 276 {
 277         struct nlattr *tb[TCA_ACT_BPF_MAX + 1];
 278         struct tcf_bpf_cfg cfg, old;
 279         struct tc_act_bpf *parm;
 280         struct tcf_bpf *prog;
 281         bool is_bpf, is_ebpf;
 282         int ret, res = 0;
 283
 284         if (!nla)
 285                 return -EINVAL;
 286
 287         ret = nla_parse_nested(tb, TCA_ACT_BPF_MAX, nla, act_bpf_policy);
 288         if (ret < 0)
 289                 return ret;
 290
 291         if (!tb[TCA_ACT_BPF_PARMS])
 292                 return -EINVAL;
 293
 294         parm = nla_data(tb[TCA_ACT_BPF_PARMS]);
 295
 296         if (!tcf_hash_check(parm->index, act, bind)) {
 297                 ret = tcf_hash_create(parm->index, est, act,
 298                                       sizeof(*prog), bind, true);
 299                 if (ret < 0)
 300                         return ret;
 301
 302                 res = ACT_P_CREATED;
 303         } else {
 304                 /* Don't override defaults. */
 305                 if (bind)
 306                         return 0;
 307
 308                 tcf_hash_release(act, bind);
 309                 if (!replace)
 310                         return -EEXIST;
 311         }
 312
 313         is_bpf = tb[TCA_ACT_BPF_OPS_LEN] && tb[TCA_ACT_BPF_OPS];
 314         is_ebpf = tb[TCA_ACT_BPF_FD];
 315
 316         if ((!is_bpf && !is_ebpf) || (is_bpf && is_ebpf)) {
 317                 ret = -EINVAL;
 318                 goto out;
 319         }
 320
 321         memset(&cfg, 0, sizeof(cfg));
 322
 323         ret = is_bpf ? tcf_bpf_init_from_ops(tb, &cfg) :
 324                        tcf_bpf_init_from_efd(tb, &cfg);
 325         if (ret < 0)
 326                 goto out;
 327
 328         prog = to_bpf(act);
 329         ASSERT_RTNL();
 330
 331         if (res != ACT_P_CREATED)
 332                 tcf_bpf_prog_fill_cfg(prog, &old);
 333
 334         prog->bpf_ops = cfg.bpf_ops;
 335         prog->bpf_name = cfg.bpf_name;
 336
 337         if (cfg.bpf_num_ops)
 338                 prog->bpf_num_ops = cfg.bpf_num_ops;
 339         if (cfg.bpf_fd)
 340                 prog->bpf_fd = cfg.bpf_fd;
 341
 342         prog->tcf_action = parm->action;
 343         rcu_assign_pointer(prog->filter, cfg.filter);
 344
 345         if (res == ACT_P_CREATED) {
 346                 tcf_hash_insert(act);
 347         } else {
 348                 /* make sure the program being replaced is no longer executing */
 349                 synchronize_rcu();
 350                 tcf_bpf_cfg_cleanup(&old);
 351         }
 352
 353         return res;
 354 out:
 355         if (res == ACT_P_CREATED)
 356                 tcf_hash_cleanup(act, est);
 357
 358         return ret;
 359 }
 360
 361 static void tcf_bpf_cleanup(struct tc_action *act, int bind)
 362 {
 363         struct tcf_bpf_cfg tmp;
 364
 365         tcf_bpf_prog_fill_cfg(act->priv, &tmp);
 366         tcf_bpf_cfg_cleanup(&tmp);
 367 }
 368
 369 static struct tc_action_ops act_bpf_ops __read_mostly = {
 370         .kind           =       "bpf",
 371         .type           =       TCA_ACT_BPF,
 372         .owner          =       THIS_MODULE,
 373         .act            =       tcf_bpf,
 374         .dump           =       tcf_bpf_dump,
 375         .cleanup        =       tcf_bpf_cleanup,
 376         .init           =       tcf_bpf_init,
 377 };
 378
 379 static int __init bpf_init_module(void)
 380 {
 381         return tcf_register_action(&act_bpf_ops, BPF_TAB_MASK);
 382 }
 383
 384 static void __exit bpf_cleanup_module(void)
 385 {
 386         tcf_unregister_action(&act_bpf_ops);
 387 }
 388
 389 module_init(bpf_init_module);
 390 module_exit(bpf_cleanup_module);
 391
 392 MODULE_AUTHOR("Jiri Pirko <jiri@resnulli.us>");
 393 MODULE_DESCRIPTION("TC BPF based action");
 394 MODULE_LICENSE("GPL v2");