net/netfilter/nf_conntrack_bpf.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* Unstable Conntrack Helpers for XDP and TC-BPF hook
   3  *
   4  * These are called from the XDP and SCHED_CLS BPF programs. Note that it is
   5  * allowed to break compatibility for these functions since the interface they
   6  * are exposed through to BPF programs is explicitly unstable.
   7  */
   8
   9 #include <linux/bpf_verifier.h>
  10 #include <linux/bpf.h>
  11 #include <linux/btf.h>
  12 #include <linux/filter.h>
  13 #include <linux/mutex.h>
  14 #include <linux/types.h>
  15 #include <linux/btf_ids.h>
  16 #include <linux/net_namespace.h>
  17 #include <net/netfilter/nf_conntrack_bpf.h>
  18 #include <net/netfilter/nf_conntrack_core.h>
  19
  20 /* bpf_ct_opts - Options for CT lookup helpers
  21  *
  22  * Members:
  23  * @netns_id   - Specify the network namespace for lookup
  24  *               Values:
  25  *                 BPF_F_CURRENT_NETNS (-1)
  26  *                   Use namespace associated with ctx (xdp_md, __sk_buff)
  27  *                 [0, S32_MAX]
  28  *                   Network Namespace ID
  29  * @error      - Out parameter, set for any errors encountered
  30  *               Values:
  31  *                 -EINVAL - Passed NULL for bpf_tuple pointer
  32  *                 -EINVAL - opts->reserved is not 0
  33  *                 -EINVAL - netns_id is less than -1
  34  *                 -EINVAL - opts__sz isn't NF_BPF_CT_OPTS_SZ (12)
  35  *                 -EPROTO - l4proto isn't one of IPPROTO_TCP or IPPROTO_UDP
  36  *                 -ENONET - No network namespace found for netns_id
  37  *                 -ENOENT - Conntrack lookup could not find entry for tuple
  38  *                 -EAFNOSUPPORT - tuple__sz isn't one of sizeof(tuple->ipv4)
  39  *                                 or sizeof(tuple->ipv6)
  40  * @l4proto    - Layer 4 protocol
  41  *               Values:
  42  *                 IPPROTO_TCP, IPPROTO_UDP
  43  * @dir:       - connection tracking tuple direction.
  44  * @reserved   - Reserved member, will be reused for more options in future
  45  *               Values:
  46  *                 0
  47  */
  48 struct bpf_ct_opts {
  49         s32 netns_id;
  50         s32 error;
  51         u8 l4proto;
  52         u8 dir;
  53         u8 reserved[2];
  54 };
  55
  56 enum {
  57         NF_BPF_CT_OPTS_SZ = 12,
  58 };
  59
  60 static int bpf_nf_ct_tuple_parse(struct bpf_sock_tuple *bpf_tuple,
  61                                  u32 tuple_len, u8 protonum, u8 dir,
  62                                  struct nf_conntrack_tuple *tuple)
  63 {
  64         union nf_inet_addr *src = dir ? &tuple->dst.u3 : &tuple->src.u3;
  65         union nf_inet_addr *dst = dir ? &tuple->src.u3 : &tuple->dst.u3;
  66         union nf_conntrack_man_proto *sport = dir ? (void *)&tuple->dst.u
  67                                                   : &tuple->src.u;
  68         union nf_conntrack_man_proto *dport = dir ? &tuple->src.u
  69                                                   : (void *)&tuple->dst.u;
  70
  71         if (unlikely(protonum != IPPROTO_TCP && protonum != IPPROTO_UDP))
  72                 return -EPROTO;
  73
  74         memset(tuple, 0, sizeof(*tuple));
  75
  76         switch (tuple_len) {
  77         case sizeof(bpf_tuple->ipv4):
  78                 tuple->src.l3num = AF_INET;
  79                 src->ip = bpf_tuple->ipv4.saddr;
  80                 sport->tcp.port = bpf_tuple->ipv4.sport;
  81                 dst->ip = bpf_tuple->ipv4.daddr;
  82                 dport->tcp.port = bpf_tuple->ipv4.dport;
  83                 break;
  84         case sizeof(bpf_tuple->ipv6):
  85                 tuple->src.l3num = AF_INET6;
  86                 memcpy(src->ip6, bpf_tuple->ipv6.saddr, sizeof(bpf_tuple->ipv6.saddr));
  87                 sport->tcp.port = bpf_tuple->ipv6.sport;
  88                 memcpy(dst->ip6, bpf_tuple->ipv6.daddr, sizeof(bpf_tuple->ipv6.daddr));
  89                 dport->tcp.port = bpf_tuple->ipv6.dport;
  90                 break;
  91         default:
  92                 return -EAFNOSUPPORT;
  93         }
  94         tuple->dst.protonum = protonum;
  95         tuple->dst.dir = dir;
  96
  97         return 0;
  98 }
  99
 100 static struct nf_conn *
 101 __bpf_nf_ct_alloc_entry(struct net *net, struct bpf_sock_tuple *bpf_tuple,
 102                         u32 tuple_len, struct bpf_ct_opts *opts, u32 opts_len,
 103                         u32 timeout)
 104 {
 105         struct nf_conntrack_tuple otuple, rtuple;
 106         struct nf_conn *ct;
 107         int err;
 108
 109         if (!opts || !bpf_tuple || opts->reserved[0] || opts->reserved[1] ||
 110             opts_len != NF_BPF_CT_OPTS_SZ)
 111                 return ERR_PTR(-EINVAL);
 112
 113         if (unlikely(opts->netns_id < BPF_F_CURRENT_NETNS))
 114                 return ERR_PTR(-EINVAL);
 115
 116         err = bpf_nf_ct_tuple_parse(bpf_tuple, tuple_len, opts->l4proto,
 117                                     IP_CT_DIR_ORIGINAL, &otuple);
 118         if (err < 0)
 119                 return ERR_PTR(err);
 120
 121         err = bpf_nf_ct_tuple_parse(bpf_tuple, tuple_len, opts->l4proto,
 122                                     IP_CT_DIR_REPLY, &rtuple);
 123         if (err < 0)
 124                 return ERR_PTR(err);
 125
 126         if (opts->netns_id >= 0) {
 127                 net = get_net_ns_by_id(net, opts->netns_id);
 128                 if (unlikely(!net))
 129                         return ERR_PTR(-ENONET);
 130         }
 131
 132         ct = nf_conntrack_alloc(net, &nf_ct_zone_dflt, &otuple, &rtuple,
 133                                 GFP_ATOMIC);
 134         if (IS_ERR(ct))
 135                 goto out;
 136
 137         memset(&ct->proto, 0, sizeof(ct->proto));
 138         __nf_ct_set_timeout(ct, timeout * HZ);
 139
 140 out:
 141         if (opts->netns_id >= 0)
 142                 put_net(net);
 143
 144         return ct;
 145 }
 146
 147 static struct nf_conn *__bpf_nf_ct_lookup(struct net *net,
 148                                           struct bpf_sock_tuple *bpf_tuple,
 149                                           u32 tuple_len, struct bpf_ct_opts *opts,
 150                                           u32 opts_len)
 151 {
 152         struct nf_conntrack_tuple_hash *hash;
 153         struct nf_conntrack_tuple tuple;
 154         struct nf_conn *ct;
 155         int err;
 156
 157         if (!opts || !bpf_tuple || opts->reserved[0] || opts->reserved[1] ||
 158             opts_len != NF_BPF_CT_OPTS_SZ)
 159                 return ERR_PTR(-EINVAL);
 160         if (unlikely(opts->l4proto != IPPROTO_TCP && opts->l4proto != IPPROTO_UDP))
 161                 return ERR_PTR(-EPROTO);
 162         if (unlikely(opts->netns_id < BPF_F_CURRENT_NETNS))
 163                 return ERR_PTR(-EINVAL);
 164
 165         err = bpf_nf_ct_tuple_parse(bpf_tuple, tuple_len, opts->l4proto,
 166                                     IP_CT_DIR_ORIGINAL, &tuple);
 167         if (err < 0)
 168                 return ERR_PTR(err);
 169
 170         if (opts->netns_id >= 0) {
 171                 net = get_net_ns_by_id(net, opts->netns_id);
 172                 if (unlikely(!net))
 173                         return ERR_PTR(-ENONET);
 174         }
 175
 176         hash = nf_conntrack_find_get(net, &nf_ct_zone_dflt, &tuple);
 177         if (opts->netns_id >= 0)
 178                 put_net(net);
 179         if (!hash)
 180                 return ERR_PTR(-ENOENT);
 181
 182         ct = nf_ct_tuplehash_to_ctrack(hash);
 183         opts->dir = NF_CT_DIRECTION(hash);
 184
 185         return ct;
 186 }
 187
 188 BTF_ID_LIST(btf_nf_conn_ids)
 189 BTF_ID(struct, nf_conn)
 190 BTF_ID(struct, nf_conn___init)
 191
 192 /* Check writes into `struct nf_conn` */
 193 static int _nf_conntrack_btf_struct_access(struct bpf_verifier_log *log,
 194                                            const struct bpf_reg_state *reg,
 195                                            int off, int size)
 196 {
 197         const struct btf_type *ncit, *nct, *t;
 198         size_t end;
 199
 200         ncit = btf_type_by_id(reg->btf, btf_nf_conn_ids[1]);
 201         nct = btf_type_by_id(reg->btf, btf_nf_conn_ids[0]);
 202         t = btf_type_by_id(reg->btf, reg->btf_id);
 203         if (t != nct && t != ncit) {
 204                 bpf_log(log, "only read is supported\n");
 205                 return -EACCES;
 206         }
 207
 208         /* `struct nf_conn` and `struct nf_conn___init` have the same layout
 209          * so we are safe to simply merge offset checks here
 210          */
 211         switch (off) {
 212 #if defined(CONFIG_NF_CONNTRACK_MARK)
 213         case offsetof(struct nf_conn, mark):
 214                 end = offsetofend(struct nf_conn, mark);
 215                 break;
 216 #endif
 217         default:
 218                 bpf_log(log, "no write support to nf_conn at off %d\n", off);
 219                 return -EACCES;
 220         }
 221
 222         if (off + size > end) {
 223                 bpf_log(log,
 224                         "write access at off %d with size %d beyond the member of nf_conn ended at %zu\n",
 225                         off, size, end);
 226                 return -EACCES;
 227         }
 228
 229         return 0;
 230 }
 231
 232 __diag_push();
 233 __diag_ignore_all("-Wmissing-prototypes",
 234                   "Global functions as their definitions will be in nf_conntrack BTF");
 235
 236 /* bpf_xdp_ct_alloc - Allocate a new CT entry
 237  *
 238  * Parameters:
 239  * @xdp_ctx     - Pointer to ctx (xdp_md) in XDP program
 240  *                  Cannot be NULL
 241  * @bpf_tuple   - Pointer to memory representing the tuple to look up
 242  *                  Cannot be NULL
 243  * @tuple__sz   - Length of the tuple structure
 244  *                  Must be one of sizeof(bpf_tuple->ipv4) or
 245  *                  sizeof(bpf_tuple->ipv6)
 246  * @opts        - Additional options for allocation (documented above)
 247  *                  Cannot be NULL
 248  * @opts__sz    - Length of the bpf_ct_opts structure
 249  *                  Must be NF_BPF_CT_OPTS_SZ (12)
 250  */
 251 __bpf_kfunc struct nf_conn___init *
 252 bpf_xdp_ct_alloc(struct xdp_md *xdp_ctx, struct bpf_sock_tuple *bpf_tuple,
 253                  u32 tuple__sz, struct bpf_ct_opts *opts, u32 opts__sz)
 254 {
 255         struct xdp_buff *ctx = (struct xdp_buff *)xdp_ctx;
 256         struct nf_conn *nfct;
 257
 258         nfct = __bpf_nf_ct_alloc_entry(dev_net(ctx->rxq->dev), bpf_tuple, tuple__sz,
 259                                        opts, opts__sz, 10);
 260         if (IS_ERR(nfct)) {
 261                 if (opts)
 262                         opts->error = PTR_ERR(nfct);
 263                 return NULL;
 264         }
 265
 266         return (struct nf_conn___init *)nfct;
 267 }
 268
 269 /* bpf_xdp_ct_lookup - Lookup CT entry for the given tuple, and acquire a
 270  *                     reference to it
 271  *
 272  * Parameters:
 273  * @xdp_ctx     - Pointer to ctx (xdp_md) in XDP program
 274  *                  Cannot be NULL
 275  * @bpf_tuple   - Pointer to memory representing the tuple to look up
 276  *                  Cannot be NULL
 277  * @tuple__sz   - Length of the tuple structure
 278  *                  Must be one of sizeof(bpf_tuple->ipv4) or
 279  *                  sizeof(bpf_tuple->ipv6)
 280  * @opts        - Additional options for lookup (documented above)
 281  *                  Cannot be NULL
 282  * @opts__sz    - Length of the bpf_ct_opts structure
 283  *                  Must be NF_BPF_CT_OPTS_SZ (12)
 284  */
 285 __bpf_kfunc struct nf_conn *
 286 bpf_xdp_ct_lookup(struct xdp_md *xdp_ctx, struct bpf_sock_tuple *bpf_tuple,
 287                   u32 tuple__sz, struct bpf_ct_opts *opts, u32 opts__sz)
 288 {
 289         struct xdp_buff *ctx = (struct xdp_buff *)xdp_ctx;
 290         struct net *caller_net;
 291         struct nf_conn *nfct;
 292
 293         caller_net = dev_net(ctx->rxq->dev);
 294         nfct = __bpf_nf_ct_lookup(caller_net, bpf_tuple, tuple__sz, opts, opts__sz);
 295         if (IS_ERR(nfct)) {
 296                 if (opts)
 297                         opts->error = PTR_ERR(nfct);
 298                 return NULL;
 299         }
 300         return nfct;
 301 }
 302
 303 /* bpf_skb_ct_alloc - Allocate a new CT entry
 304  *
 305  * Parameters:
 306  * @skb_ctx     - Pointer to ctx (__sk_buff) in TC program
 307  *                  Cannot be NULL
 308  * @bpf_tuple   - Pointer to memory representing the tuple to look up
 309  *                  Cannot be NULL
 310  * @tuple__sz   - Length of the tuple structure
 311  *                  Must be one of sizeof(bpf_tuple->ipv4) or
 312  *                  sizeof(bpf_tuple->ipv6)
 313  * @opts        - Additional options for allocation (documented above)
 314  *                  Cannot be NULL
 315  * @opts__sz    - Length of the bpf_ct_opts structure
 316  *                  Must be NF_BPF_CT_OPTS_SZ (12)
 317  */
 318 __bpf_kfunc struct nf_conn___init *
 319 bpf_skb_ct_alloc(struct __sk_buff *skb_ctx, struct bpf_sock_tuple *bpf_tuple,
 320                  u32 tuple__sz, struct bpf_ct_opts *opts, u32 opts__sz)
 321 {
 322         struct sk_buff *skb = (struct sk_buff *)skb_ctx;
 323         struct nf_conn *nfct;
 324         struct net *net;
 325
 326         net = skb->dev ? dev_net(skb->dev) : sock_net(skb->sk);
 327         nfct = __bpf_nf_ct_alloc_entry(net, bpf_tuple, tuple__sz, opts, opts__sz, 10);
 328         if (IS_ERR(nfct)) {
 329                 if (opts)
 330                         opts->error = PTR_ERR(nfct);
 331                 return NULL;
 332         }
 333
 334         return (struct nf_conn___init *)nfct;
 335 }
 336
 337 /* bpf_skb_ct_lookup - Lookup CT entry for the given tuple, and acquire a
 338  *                     reference to it
 339  *
 340  * Parameters:
 341  * @skb_ctx     - Pointer to ctx (__sk_buff) in TC program
 342  *                  Cannot be NULL
 343  * @bpf_tuple   - Pointer to memory representing the tuple to look up
 344  *                  Cannot be NULL
 345  * @tuple__sz   - Length of the tuple structure
 346  *                  Must be one of sizeof(bpf_tuple->ipv4) or
 347  *                  sizeof(bpf_tuple->ipv6)
 348  * @opts        - Additional options for lookup (documented above)
 349  *                  Cannot be NULL
 350  * @opts__sz    - Length of the bpf_ct_opts structure
 351  *                  Must be NF_BPF_CT_OPTS_SZ (12)
 352  */
 353 __bpf_kfunc struct nf_conn *
 354 bpf_skb_ct_lookup(struct __sk_buff *skb_ctx, struct bpf_sock_tuple *bpf_tuple,
 355                   u32 tuple__sz, struct bpf_ct_opts *opts, u32 opts__sz)
 356 {
 357         struct sk_buff *skb = (struct sk_buff *)skb_ctx;
 358         struct net *caller_net;
 359         struct nf_conn *nfct;
 360
 361         caller_net = skb->dev ? dev_net(skb->dev) : sock_net(skb->sk);
 362         nfct = __bpf_nf_ct_lookup(caller_net, bpf_tuple, tuple__sz, opts, opts__sz);
 363         if (IS_ERR(nfct)) {
 364                 if (opts)
 365                         opts->error = PTR_ERR(nfct);
 366                 return NULL;
 367         }
 368         return nfct;
 369 }
 370
 371 /* bpf_ct_insert_entry - Add the provided entry into a CT map
 372  *
 373  * This must be invoked for referenced PTR_TO_BTF_ID.
 374  *
 375  * @nfct         - Pointer to referenced nf_conn___init object, obtained
 376  *                 using bpf_xdp_ct_alloc or bpf_skb_ct_alloc.
 377  */
 378 __bpf_kfunc struct nf_conn *bpf_ct_insert_entry(struct nf_conn___init *nfct_i)
 379 {
 380         struct nf_conn *nfct = (struct nf_conn *)nfct_i;
 381         int err;
 382
 383         nfct->status |= IPS_CONFIRMED;
 384         err = nf_conntrack_hash_check_insert(nfct);
 385         if (err < 0) {
 386                 nf_conntrack_free(nfct);
 387                 return NULL;
 388         }
 389         return nfct;
 390 }
 391
 392 /* bpf_ct_release - Release acquired nf_conn object
 393  *
 394  * This must be invoked for referenced PTR_TO_BTF_ID, and the verifier rejects
 395  * the program if any references remain in the program in all of the explored
 396  * states.
 397  *
 398  * Parameters:
 399  * @nf_conn      - Pointer to referenced nf_conn object, obtained using
 400  *                 bpf_xdp_ct_lookup or bpf_skb_ct_lookup.
 401  */
 402 __bpf_kfunc void bpf_ct_release(struct nf_conn *nfct)
 403 {
 404         nf_ct_put(nfct);
 405 }
 406
 407 /* bpf_ct_set_timeout - Set timeout of allocated nf_conn
 408  *
 409  * Sets the default timeout of newly allocated nf_conn before insertion.
 410  * This helper must be invoked for refcounted pointer to nf_conn___init.
 411  *
 412  * Parameters:
 413  * @nfct         - Pointer to referenced nf_conn object, obtained using
 414  *                 bpf_xdp_ct_alloc or bpf_skb_ct_alloc.
 415  * @timeout      - Timeout in msecs.
 416  */
 417 __bpf_kfunc void bpf_ct_set_timeout(struct nf_conn___init *nfct, u32 timeout)
 418 {
 419         __nf_ct_set_timeout((struct nf_conn *)nfct, msecs_to_jiffies(timeout));
 420 }
 421
 422 /* bpf_ct_change_timeout - Change timeout of inserted nf_conn
 423  *
 424  * Change timeout associated of the inserted or looked up nf_conn.
 425  * This helper must be invoked for refcounted pointer to nf_conn.
 426  *
 427  * Parameters:
 428  * @nfct         - Pointer to referenced nf_conn object, obtained using
 429  *                 bpf_ct_insert_entry, bpf_xdp_ct_lookup, or bpf_skb_ct_lookup.
 430  * @timeout      - New timeout in msecs.
 431  */
 432 __bpf_kfunc int bpf_ct_change_timeout(struct nf_conn *nfct, u32 timeout)
 433 {
 434         return __nf_ct_change_timeout(nfct, msecs_to_jiffies(timeout));
 435 }
 436
 437 /* bpf_ct_set_status - Set status field of allocated nf_conn
 438  *
 439  * Set the status field of the newly allocated nf_conn before insertion.
 440  * This must be invoked for referenced PTR_TO_BTF_ID to nf_conn___init.
 441  *
 442  * Parameters:
 443  * @nfct         - Pointer to referenced nf_conn object, obtained using
 444  *                 bpf_xdp_ct_alloc or bpf_skb_ct_alloc.
 445  * @status       - New status value.
 446  */
 447 __bpf_kfunc int bpf_ct_set_status(const struct nf_conn___init *nfct, u32 status)
 448 {
 449         return nf_ct_change_status_common((struct nf_conn *)nfct, status);
 450 }
 451
 452 /* bpf_ct_change_status - Change status of inserted nf_conn
 453  *
 454  * Change the status field of the provided connection tracking entry.
 455  * This must be invoked for referenced PTR_TO_BTF_ID to nf_conn.
 456  *
 457  * Parameters:
 458  * @nfct         - Pointer to referenced nf_conn object, obtained using
 459  *                 bpf_ct_insert_entry, bpf_xdp_ct_lookup or bpf_skb_ct_lookup.
 460  * @status       - New status value.
 461  */
 462 __bpf_kfunc int bpf_ct_change_status(struct nf_conn *nfct, u32 status)
 463 {
 464         return nf_ct_change_status_common(nfct, status);
 465 }
 466
 467 __diag_pop()
 468
 469 BTF_SET8_START(nf_ct_kfunc_set)
 470 BTF_ID_FLAGS(func, bpf_xdp_ct_alloc, KF_ACQUIRE | KF_RET_NULL)
 471 BTF_ID_FLAGS(func, bpf_xdp_ct_lookup, KF_ACQUIRE | KF_RET_NULL)
 472 BTF_ID_FLAGS(func, bpf_skb_ct_alloc, KF_ACQUIRE | KF_RET_NULL)
 473 BTF_ID_FLAGS(func, bpf_skb_ct_lookup, KF_ACQUIRE | KF_RET_NULL)
 474 BTF_ID_FLAGS(func, bpf_ct_insert_entry, KF_ACQUIRE | KF_RET_NULL | KF_RELEASE)
 475 BTF_ID_FLAGS(func, bpf_ct_release, KF_RELEASE)
 476 BTF_ID_FLAGS(func, bpf_ct_set_timeout, KF_TRUSTED_ARGS)
 477 BTF_ID_FLAGS(func, bpf_ct_change_timeout, KF_TRUSTED_ARGS)
 478 BTF_ID_FLAGS(func, bpf_ct_set_status, KF_TRUSTED_ARGS)
 479 BTF_ID_FLAGS(func, bpf_ct_change_status, KF_TRUSTED_ARGS)
 480 BTF_SET8_END(nf_ct_kfunc_set)
 481
 482 static const struct btf_kfunc_id_set nf_conntrack_kfunc_set = {
 483         .owner = THIS_MODULE,
 484         .set   = &nf_ct_kfunc_set,
 485 };
 486
 487 int register_nf_conntrack_bpf(void)
 488 {
 489         int ret;
 490
 491         ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_XDP, &nf_conntrack_kfunc_set);
 492         ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS, &nf_conntrack_kfunc_set);
 493         if (!ret) {
 494                 mutex_lock(&nf_conn_btf_access_lock);
 495                 nfct_btf_struct_access = _nf_conntrack_btf_struct_access;
 496                 mutex_unlock(&nf_conn_btf_access_lock);
 497         }
 498
 499         return ret;
 500 }
 501
 502 void cleanup_nf_conntrack_bpf(void)
 503 {
 504         mutex_lock(&nf_conn_btf_access_lock);
 505         nfct_btf_struct_access = NULL;
 506         mutex_unlock(&nf_conn_btf_access_lock);
 507 }