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/xdp.h>
  18 #include <net/netfilter/nf_conntrack_bpf.h>
  19 #include <net/netfilter/nf_conntrack_core.h>
  20
  21 /* bpf_ct_opts - Options for CT lookup helpers
  22  *
  23  * Members:
  24  * @netns_id   - Specify the network namespace for lookup
  25  *               Values:
  26  *                 BPF_F_CURRENT_NETNS (-1)
  27  *                   Use namespace associated with ctx (xdp_md, __sk_buff)
  28  *                 [0, S32_MAX]
  29  *                   Network Namespace ID
  30  * @error      - Out parameter, set for any errors encountered
  31  *               Values:
  32  *                 -EINVAL - Passed NULL for bpf_tuple pointer
  33  *                 -EINVAL - opts->reserved is not 0
  34  *                 -EINVAL - netns_id is less than -1
  35  *                 -EINVAL - opts__sz isn't NF_BPF_CT_OPTS_SZ (12)
  36  *                 -EPROTO - l4proto isn't one of IPPROTO_TCP or IPPROTO_UDP
  37  *                 -ENONET - No network namespace found for netns_id
  38  *                 -ENOENT - Conntrack lookup could not find entry for tuple
  39  *                 -EAFNOSUPPORT - tuple__sz isn't one of sizeof(tuple->ipv4)
  40  *                                 or sizeof(tuple->ipv6)
  41  * @l4proto    - Layer 4 protocol
  42  *               Values:
  43  *                 IPPROTO_TCP, IPPROTO_UDP
  44  * @dir:       - connection tracking tuple direction.
  45  * @reserved   - Reserved member, will be reused for more options in future
  46  *               Values:
  47  *                 0
  48  */
  49 struct bpf_ct_opts {
  50         s32 netns_id;
  51         s32 error;
  52         u8 l4proto;
  53         u8 dir;
  54         u8 reserved[2];
  55 };
  56
  57 enum {
  58         NF_BPF_CT_OPTS_SZ = 12,
  59 };
  60
  61 static int bpf_nf_ct_tuple_parse(struct bpf_sock_tuple *bpf_tuple,
  62                                  u32 tuple_len, u8 protonum, u8 dir,
  63                                  struct nf_conntrack_tuple *tuple)
  64 {
  65         union nf_inet_addr *src = dir ? &tuple->dst.u3 : &tuple->src.u3;
  66         union nf_inet_addr *dst = dir ? &tuple->src.u3 : &tuple->dst.u3;
  67         union nf_conntrack_man_proto *sport = dir ? (void *)&tuple->dst.u
  68                                                   : &tuple->src.u;
  69         union nf_conntrack_man_proto *dport = dir ? &tuple->src.u
  70                                                   : (void *)&tuple->dst.u;
  71
  72         if (unlikely(protonum != IPPROTO_TCP && protonum != IPPROTO_UDP))
  73                 return -EPROTO;
  74
  75         memset(tuple, 0, sizeof(*tuple));
  76
  77         switch (tuple_len) {
  78         case sizeof(bpf_tuple->ipv4):
  79                 tuple->src.l3num = AF_INET;
  80                 src->ip = bpf_tuple->ipv4.saddr;
  81                 sport->tcp.port = bpf_tuple->ipv4.sport;
  82                 dst->ip = bpf_tuple->ipv4.daddr;
  83                 dport->tcp.port = bpf_tuple->ipv4.dport;
  84                 break;
  85         case sizeof(bpf_tuple->ipv6):
  86                 tuple->src.l3num = AF_INET6;
  87                 memcpy(src->ip6, bpf_tuple->ipv6.saddr, sizeof(bpf_tuple->ipv6.saddr));
  88                 sport->tcp.port = bpf_tuple->ipv6.sport;
  89                 memcpy(dst->ip6, bpf_tuple->ipv6.daddr, sizeof(bpf_tuple->ipv6.daddr));
  90                 dport->tcp.port = bpf_tuple->ipv6.dport;
  91                 break;
  92         default:
  93                 return -EAFNOSUPPORT;
  94         }
  95         tuple->dst.protonum = protonum;
  96         tuple->dst.dir = dir;
  97
  98         return 0;
  99 }
 100
 101 static struct nf_conn *
 102 __bpf_nf_ct_alloc_entry(struct net *net, struct bpf_sock_tuple *bpf_tuple,
 103                         u32 tuple_len, struct bpf_ct_opts *opts, u32 opts_len,
 104                         u32 timeout)
 105 {
 106         struct nf_conntrack_tuple otuple, rtuple;
 107         struct nf_conn *ct;
 108         int err;
 109
 110         if (!opts || !bpf_tuple || opts->reserved[0] || opts->reserved[1] ||
 111             opts_len != NF_BPF_CT_OPTS_SZ)
 112                 return ERR_PTR(-EINVAL);
 113
 114         if (unlikely(opts->netns_id < BPF_F_CURRENT_NETNS))
 115                 return ERR_PTR(-EINVAL);
 116
 117         err = bpf_nf_ct_tuple_parse(bpf_tuple, tuple_len, opts->l4proto,
 118                                     IP_CT_DIR_ORIGINAL, &otuple);
 119         if (err < 0)
 120                 return ERR_PTR(err);
 121
 122         err = bpf_nf_ct_tuple_parse(bpf_tuple, tuple_len, opts->l4proto,
 123                                     IP_CT_DIR_REPLY, &rtuple);
 124         if (err < 0)
 125                 return ERR_PTR(err);
 126
 127         if (opts->netns_id >= 0) {
 128                 net = get_net_ns_by_id(net, opts->netns_id);
 129                 if (unlikely(!net))
 130                         return ERR_PTR(-ENONET);
 131         }
 132
 133         ct = nf_conntrack_alloc(net, &nf_ct_zone_dflt, &otuple, &rtuple,
 134                                 GFP_ATOMIC);
 135         if (IS_ERR(ct))
 136                 goto out;
 137
 138         memset(&ct->proto, 0, sizeof(ct->proto));
 139         __nf_ct_set_timeout(ct, timeout * HZ);
 140
 141 out:
 142         if (opts->netns_id >= 0)
 143                 put_net(net);
 144
 145         return ct;
 146 }
 147
 148 static struct nf_conn *__bpf_nf_ct_lookup(struct net *net,
 149                                           struct bpf_sock_tuple *bpf_tuple,
 150                                           u32 tuple_len, struct bpf_ct_opts *opts,
 151                                           u32 opts_len)
 152 {
 153         struct nf_conntrack_tuple_hash *hash;
 154         struct nf_conntrack_tuple tuple;
 155         struct nf_conn *ct;
 156         int err;
 157
 158         if (!opts || !bpf_tuple || opts->reserved[0] || opts->reserved[1] ||
 159             opts_len != NF_BPF_CT_OPTS_SZ)
 160                 return ERR_PTR(-EINVAL);
 161         if (unlikely(opts->l4proto != IPPROTO_TCP && opts->l4proto != IPPROTO_UDP))
 162                 return ERR_PTR(-EPROTO);
 163         if (unlikely(opts->netns_id < BPF_F_CURRENT_NETNS))
 164                 return ERR_PTR(-EINVAL);
 165
 166         err = bpf_nf_ct_tuple_parse(bpf_tuple, tuple_len, opts->l4proto,
 167                                     IP_CT_DIR_ORIGINAL, &tuple);
 168         if (err < 0)
 169                 return ERR_PTR(err);
 170
 171         if (opts->netns_id >= 0) {
 172                 net = get_net_ns_by_id(net, opts->netns_id);
 173                 if (unlikely(!net))
 174                         return ERR_PTR(-ENONET);
 175         }
 176
 177         hash = nf_conntrack_find_get(net, &nf_ct_zone_dflt, &tuple);
 178         if (opts->netns_id >= 0)
 179                 put_net(net);
 180         if (!hash)
 181                 return ERR_PTR(-ENOENT);
 182
 183         ct = nf_ct_tuplehash_to_ctrack(hash);
 184         opts->dir = NF_CT_DIRECTION(hash);
 185
 186         return ct;
 187 }
 188
 189 BTF_ID_LIST(btf_nf_conn_ids)
 190 BTF_ID(struct, nf_conn)
 191 BTF_ID(struct, nf_conn___init)
 192
 193 /* Check writes into `struct nf_conn` */
 194 static int _nf_conntrack_btf_struct_access(struct bpf_verifier_log *log,
 195                                            const struct bpf_reg_state *reg,
 196                                            int off, int size)
 197 {
 198         const struct btf_type *ncit, *nct, *t;
 199         size_t end;
 200
 201         ncit = btf_type_by_id(reg->btf, btf_nf_conn_ids[1]);
 202         nct = btf_type_by_id(reg->btf, btf_nf_conn_ids[0]);
 203         t = btf_type_by_id(reg->btf, reg->btf_id);
 204         if (t != nct && t != ncit) {
 205                 bpf_log(log, "only read is supported\n");
 206                 return -EACCES;
 207         }
 208
 209         /* `struct nf_conn` and `struct nf_conn___init` have the same layout
 210          * so we are safe to simply merge offset checks here
 211          */
 212         switch (off) {
 213 #if defined(CONFIG_NF_CONNTRACK_MARK)
 214         case offsetof(struct nf_conn, mark):
 215                 end = offsetofend(struct nf_conn, mark);
 216                 break;
 217 #endif
 218         default:
 219                 bpf_log(log, "no write support to nf_conn at off %d\n", off);
 220                 return -EACCES;
 221         }
 222
 223         if (off + size > end) {
 224                 bpf_log(log,
 225                         "write access at off %d with size %d beyond the member of nf_conn ended at %zu\n",
 226                         off, size, end);
 227                 return -EACCES;
 228         }
 229
 230         return 0;
 231 }
 232
 233 __bpf_kfunc_start_defs();
 234
 235 /* bpf_xdp_ct_alloc - Allocate a new CT entry
 236  *
 237  * Parameters:
 238  * @xdp_ctx     - Pointer to ctx (xdp_md) in XDP program
 239  *                  Cannot be NULL
 240  * @bpf_tuple   - Pointer to memory representing the tuple to look up
 241  *                  Cannot be NULL
 242  * @tuple__sz   - Length of the tuple structure
 243  *                  Must be one of sizeof(bpf_tuple->ipv4) or
 244  *                  sizeof(bpf_tuple->ipv6)
 245  * @opts        - Additional options for allocation (documented above)
 246  *                  Cannot be NULL
 247  * @opts__sz    - Length of the bpf_ct_opts structure
 248  *                  Must be NF_BPF_CT_OPTS_SZ (12)
 249  */
 250 __bpf_kfunc struct nf_conn___init *
 251 bpf_xdp_ct_alloc(struct xdp_md *xdp_ctx, struct bpf_sock_tuple *bpf_tuple,
 252                  u32 tuple__sz, struct bpf_ct_opts *opts, u32 opts__sz)
 253 {
 254         struct xdp_buff *ctx = (struct xdp_buff *)xdp_ctx;
 255         struct nf_conn *nfct;
 256
 257         nfct = __bpf_nf_ct_alloc_entry(dev_net(ctx->rxq->dev), bpf_tuple, tuple__sz,
 258                                        opts, opts__sz, 10);
 259         if (IS_ERR(nfct)) {
 260                 if (opts)
 261                         opts->error = PTR_ERR(nfct);
 262                 return NULL;
 263         }
 264
 265         return (struct nf_conn___init *)nfct;
 266 }
 267
 268 /* bpf_xdp_ct_lookup - Lookup CT entry for the given tuple, and acquire a
 269  *                     reference to it
 270  *
 271  * Parameters:
 272  * @xdp_ctx     - Pointer to ctx (xdp_md) in XDP program
 273  *                  Cannot be NULL
 274  * @bpf_tuple   - Pointer to memory representing the tuple to look up
 275  *                  Cannot be NULL
 276  * @tuple__sz   - Length of the tuple structure
 277  *                  Must be one of sizeof(bpf_tuple->ipv4) or
 278  *                  sizeof(bpf_tuple->ipv6)
 279  * @opts        - Additional options for lookup (documented above)
 280  *                  Cannot be NULL
 281  * @opts__sz    - Length of the bpf_ct_opts structure
 282  *                  Must be NF_BPF_CT_OPTS_SZ (12)
 283  */
 284 __bpf_kfunc struct nf_conn *
 285 bpf_xdp_ct_lookup(struct xdp_md *xdp_ctx, struct bpf_sock_tuple *bpf_tuple,
 286                   u32 tuple__sz, struct bpf_ct_opts *opts, u32 opts__sz)
 287 {
 288         struct xdp_buff *ctx = (struct xdp_buff *)xdp_ctx;
 289         struct net *caller_net;
 290         struct nf_conn *nfct;
 291
 292         caller_net = dev_net(ctx->rxq->dev);
 293         nfct = __bpf_nf_ct_lookup(caller_net, bpf_tuple, tuple__sz, opts, opts__sz);
 294         if (IS_ERR(nfct)) {
 295                 if (opts)
 296                         opts->error = PTR_ERR(nfct);
 297                 return NULL;
 298         }
 299         return nfct;
 300 }
 301
 302 /* bpf_skb_ct_alloc - Allocate a new CT entry
 303  *
 304  * Parameters:
 305  * @skb_ctx     - Pointer to ctx (__sk_buff) in TC program
 306  *                  Cannot be NULL
 307  * @bpf_tuple   - Pointer to memory representing the tuple to look up
 308  *                  Cannot be NULL
 309  * @tuple__sz   - Length of the tuple structure
 310  *                  Must be one of sizeof(bpf_tuple->ipv4) or
 311  *                  sizeof(bpf_tuple->ipv6)
 312  * @opts        - Additional options for allocation (documented above)
 313  *                  Cannot be NULL
 314  * @opts__sz    - Length of the bpf_ct_opts structure
 315  *                  Must be NF_BPF_CT_OPTS_SZ (12)
 316  */
 317 __bpf_kfunc struct nf_conn___init *
 318 bpf_skb_ct_alloc(struct __sk_buff *skb_ctx, struct bpf_sock_tuple *bpf_tuple,
 319                  u32 tuple__sz, struct bpf_ct_opts *opts, u32 opts__sz)
 320 {
 321         struct sk_buff *skb = (struct sk_buff *)skb_ctx;
 322         struct nf_conn *nfct;
 323         struct net *net;
 324
 325         net = skb->dev ? dev_net(skb->dev) : sock_net(skb->sk);
 326         nfct = __bpf_nf_ct_alloc_entry(net, bpf_tuple, tuple__sz, opts, opts__sz, 10);
 327         if (IS_ERR(nfct)) {
 328                 if (opts)
 329                         opts->error = PTR_ERR(nfct);
 330                 return NULL;
 331         }
 332
 333         return (struct nf_conn___init *)nfct;
 334 }
 335
 336 /* bpf_skb_ct_lookup - Lookup CT entry for the given tuple, and acquire a
 337  *                     reference to it
 338  *
 339  * Parameters:
 340  * @skb_ctx     - Pointer to ctx (__sk_buff) in TC program
 341  *                  Cannot be NULL
 342  * @bpf_tuple   - Pointer to memory representing the tuple to look up
 343  *                  Cannot be NULL
 344  * @tuple__sz   - Length of the tuple structure
 345  *                  Must be one of sizeof(bpf_tuple->ipv4) or
 346  *                  sizeof(bpf_tuple->ipv6)
 347  * @opts        - Additional options for lookup (documented above)
 348  *                  Cannot be NULL
 349  * @opts__sz    - Length of the bpf_ct_opts structure
 350  *                  Must be NF_BPF_CT_OPTS_SZ (12)
 351  */
 352 __bpf_kfunc struct nf_conn *
 353 bpf_skb_ct_lookup(struct __sk_buff *skb_ctx, struct bpf_sock_tuple *bpf_tuple,
 354                   u32 tuple__sz, struct bpf_ct_opts *opts, u32 opts__sz)
 355 {
 356         struct sk_buff *skb = (struct sk_buff *)skb_ctx;
 357         struct net *caller_net;
 358         struct nf_conn *nfct;
 359
 360         caller_net = skb->dev ? dev_net(skb->dev) : sock_net(skb->sk);
 361         nfct = __bpf_nf_ct_lookup(caller_net, bpf_tuple, tuple__sz, opts, opts__sz);
 362         if (IS_ERR(nfct)) {
 363                 if (opts)
 364                         opts->error = PTR_ERR(nfct);
 365                 return NULL;
 366         }
 367         return nfct;
 368 }
 369
 370 /* bpf_ct_insert_entry - Add the provided entry into a CT map
 371  *
 372  * This must be invoked for referenced PTR_TO_BTF_ID.
 373  *
 374  * @nfct         - Pointer to referenced nf_conn___init object, obtained
 375  *                 using bpf_xdp_ct_alloc or bpf_skb_ct_alloc.
 376  */
 377 __bpf_kfunc struct nf_conn *bpf_ct_insert_entry(struct nf_conn___init *nfct_i)
 378 {
 379         struct nf_conn *nfct = (struct nf_conn *)nfct_i;
 380         int err;
 381
 382         if (!nf_ct_is_confirmed(nfct))
 383                 nfct->timeout += nfct_time_stamp;
 384         nfct->status |= IPS_CONFIRMED;
 385         err = nf_conntrack_hash_check_insert(nfct);
 386         if (err < 0) {
 387                 nf_conntrack_free(nfct);
 388                 return NULL;
 389         }
 390         return nfct;
 391 }
 392
 393 /* bpf_ct_release - Release acquired nf_conn object
 394  *
 395  * This must be invoked for referenced PTR_TO_BTF_ID, and the verifier rejects
 396  * the program if any references remain in the program in all of the explored
 397  * states.
 398  *
 399  * Parameters:
 400  * @nf_conn      - Pointer to referenced nf_conn object, obtained using
 401  *                 bpf_xdp_ct_lookup or bpf_skb_ct_lookup.
 402  */
 403 __bpf_kfunc void bpf_ct_release(struct nf_conn *nfct)
 404 {
 405         nf_ct_put(nfct);
 406 }
 407
 408 /* bpf_ct_set_timeout - Set timeout of allocated nf_conn
 409  *
 410  * Sets the default timeout of newly allocated nf_conn before insertion.
 411  * This helper must be invoked for refcounted pointer to nf_conn___init.
 412  *
 413  * Parameters:
 414  * @nfct         - Pointer to referenced nf_conn object, obtained using
 415  *                 bpf_xdp_ct_alloc or bpf_skb_ct_alloc.
 416  * @timeout      - Timeout in msecs.
 417  */
 418 __bpf_kfunc void bpf_ct_set_timeout(struct nf_conn___init *nfct, u32 timeout)
 419 {
 420         __nf_ct_set_timeout((struct nf_conn *)nfct, msecs_to_jiffies(timeout));
 421 }
 422
 423 /* bpf_ct_change_timeout - Change timeout of inserted nf_conn
 424  *
 425  * Change timeout associated of the inserted or looked up nf_conn.
 426  * This helper must be invoked for refcounted pointer to nf_conn.
 427  *
 428  * Parameters:
 429  * @nfct         - Pointer to referenced nf_conn object, obtained using
 430  *                 bpf_ct_insert_entry, bpf_xdp_ct_lookup, or bpf_skb_ct_lookup.
 431  * @timeout      - New timeout in msecs.
 432  */
 433 __bpf_kfunc int bpf_ct_change_timeout(struct nf_conn *nfct, u32 timeout)
 434 {
 435         return __nf_ct_change_timeout(nfct, msecs_to_jiffies(timeout));
 436 }
 437
 438 /* bpf_ct_set_status - Set status field of allocated nf_conn
 439  *
 440  * Set the status field of the newly allocated nf_conn before insertion.
 441  * This must be invoked for referenced PTR_TO_BTF_ID to nf_conn___init.
 442  *
 443  * Parameters:
 444  * @nfct         - Pointer to referenced nf_conn object, obtained using
 445  *                 bpf_xdp_ct_alloc or bpf_skb_ct_alloc.
 446  * @status       - New status value.
 447  */
 448 __bpf_kfunc int bpf_ct_set_status(const struct nf_conn___init *nfct, u32 status)
 449 {
 450         return nf_ct_change_status_common((struct nf_conn *)nfct, status);
 451 }
 452
 453 /* bpf_ct_change_status - Change status of inserted nf_conn
 454  *
 455  * Change the status field of the provided connection tracking entry.
 456  * This must be invoked for referenced PTR_TO_BTF_ID to nf_conn.
 457  *
 458  * Parameters:
 459  * @nfct         - Pointer to referenced nf_conn object, obtained using
 460  *                 bpf_ct_insert_entry, bpf_xdp_ct_lookup or bpf_skb_ct_lookup.
 461  * @status       - New status value.
 462  */
 463 __bpf_kfunc int bpf_ct_change_status(struct nf_conn *nfct, u32 status)
 464 {
 465         return nf_ct_change_status_common(nfct, status);
 466 }
 467
 468 __bpf_kfunc_end_defs();
 469
 470 BTF_SET8_START(nf_ct_kfunc_set)
 471 BTF_ID_FLAGS(func, bpf_xdp_ct_alloc, KF_ACQUIRE | KF_RET_NULL)
 472 BTF_ID_FLAGS(func, bpf_xdp_ct_lookup, KF_ACQUIRE | KF_RET_NULL)
 473 BTF_ID_FLAGS(func, bpf_skb_ct_alloc, KF_ACQUIRE | KF_RET_NULL)
 474 BTF_ID_FLAGS(func, bpf_skb_ct_lookup, KF_ACQUIRE | KF_RET_NULL)
 475 BTF_ID_FLAGS(func, bpf_ct_insert_entry, KF_ACQUIRE | KF_RET_NULL | KF_RELEASE)
 476 BTF_ID_FLAGS(func, bpf_ct_release, KF_RELEASE)
 477 BTF_ID_FLAGS(func, bpf_ct_set_timeout, KF_TRUSTED_ARGS)
 478 BTF_ID_FLAGS(func, bpf_ct_change_timeout, KF_TRUSTED_ARGS)
 479 BTF_ID_FLAGS(func, bpf_ct_set_status, KF_TRUSTED_ARGS)
 480 BTF_ID_FLAGS(func, bpf_ct_change_status, KF_TRUSTED_ARGS)
 481 BTF_SET8_END(nf_ct_kfunc_set)
 482
 483 static const struct btf_kfunc_id_set nf_conntrack_kfunc_set = {
 484         .owner = THIS_MODULE,
 485         .set   = &nf_ct_kfunc_set,
 486 };
 487
 488 int register_nf_conntrack_bpf(void)
 489 {
 490         int ret;
 491
 492         ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_XDP, &nf_conntrack_kfunc_set);
 493         ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS, &nf_conntrack_kfunc_set);
 494         if (!ret) {
 495                 mutex_lock(&nf_conn_btf_access_lock);
 496                 nfct_btf_struct_access = _nf_conntrack_btf_struct_access;
 497                 mutex_unlock(&nf_conn_btf_access_lock);
 498         }
 499
 500         return ret;
 501 }
 502
 503 void cleanup_nf_conntrack_bpf(void)
 504 {
 505         mutex_lock(&nf_conn_btf_access_lock);
 506         nfct_btf_struct_access = NULL;
 507         mutex_unlock(&nf_conn_btf_access_lock);
 508 }