1 // SPDX-License-Identifier: GPL-2.0-only 2 /* Copyright (c) 2016 Thomas Graf <tgraf@tgraf.ch> 3 */ 4 5 #include <linux/kernel.h> 6 #include <linux/module.h> 7 #include <linux/skbuff.h> 8 #include <linux/types.h> 9 #include <linux/bpf.h> 10 #include <net/lwtunnel.h> 11 #include <net/gre.h> 12 #include <net/ip6_route.h> 13 #include <net/ipv6_stubs.h> 14 15 struct bpf_lwt_prog { 16 struct bpf_prog *prog; 17 char *name; 18 }; 19 20 struct bpf_lwt { 21 struct bpf_lwt_prog in; 22 struct bpf_lwt_prog out; 23 struct bpf_lwt_prog xmit; 24 int family; 25 }; 26 27 #define MAX_PROG_NAME 256 28 29 static inline struct bpf_lwt *bpf_lwt_lwtunnel(struct lwtunnel_state *lwt) 30 { 31 return (struct bpf_lwt *)lwt->data; 32 } 33 34 #define NO_REDIRECT false 35 #define CAN_REDIRECT true 36 37 static int run_lwt_bpf(struct sk_buff *skb, struct bpf_lwt_prog *lwt, 38 struct dst_entry *dst, bool can_redirect) 39 { 40 int ret; 41 42 /* Preempt disable is needed to protect per-cpu redirect_info between 43 * BPF prog and skb_do_redirect(). The call_rcu in bpf_prog_put() and 44 * access to maps strictly require a rcu_read_lock() for protection, 45 * mixing with BH RCU lock doesn't work. 46 */ 47 preempt_disable(); 48 bpf_compute_data_pointers(skb); 49 ret = bpf_prog_run_save_cb(lwt->prog, skb); 50 51 switch (ret) { 52 case BPF_OK: 53 case BPF_LWT_REROUTE: 54 break; 55 56 case BPF_REDIRECT: 57 if (unlikely(!can_redirect)) { 58 pr_warn_once("Illegal redirect return code in prog %s\n", 59 lwt->name ? : "<unknown>"); 60 ret = BPF_OK; 61 } else { 62 skb_reset_mac_header(skb); 63 ret = skb_do_redirect(skb); 64 if (ret == 0) 65 ret = BPF_REDIRECT; 66 } 67 break; 68 69 case BPF_DROP: 70 kfree_skb(skb); 71 ret = -EPERM; 72 break; 73 74 default: 75 pr_warn_once("bpf-lwt: Illegal return value %u, expect packet loss\n", ret); 76 kfree_skb(skb); 77 ret = -EINVAL; 78 break; 79 } 80 81 preempt_enable(); 82 83 return ret; 84 } 85 86 static int bpf_lwt_input_reroute(struct sk_buff *skb) 87 { 88 int err = -EINVAL; 89 90 if (skb->protocol == htons(ETH_P_IP)) { 91 struct net_device *dev = skb_dst(skb)->dev; 92 struct iphdr *iph = ip_hdr(skb); 93 94 dev_hold(dev); 95 skb_dst_drop(skb); 96 err = ip_route_input_noref(skb, iph->daddr, iph->saddr, 97 iph->tos, dev); 98 dev_put(dev); 99 } else if (skb->protocol == htons(ETH_P_IPV6)) { 100 skb_dst_drop(skb); 101 err = ipv6_stub->ipv6_route_input(skb); 102 } else { 103 err = -EAFNOSUPPORT; 104 } 105 106 if (err) 107 goto err; 108 return dst_input(skb); 109 110 err: 111 kfree_skb(skb); 112 return err; 113 } 114 115 static int bpf_input(struct sk_buff *skb) 116 { 117 struct dst_entry *dst = skb_dst(skb); 118 struct bpf_lwt *bpf; 119 int ret; 120 121 bpf = bpf_lwt_lwtunnel(dst->lwtstate); 122 if (bpf->in.prog) { 123 ret = run_lwt_bpf(skb, &bpf->in, dst, NO_REDIRECT); 124 if (ret < 0) 125 return ret; 126 if (ret == BPF_LWT_REROUTE) 127 return bpf_lwt_input_reroute(skb); 128 } 129 130 if (unlikely(!dst->lwtstate->orig_input)) { 131 kfree_skb(skb); 132 return -EINVAL; 133 } 134 135 return dst->lwtstate->orig_input(skb); 136 } 137 138 static int bpf_output(struct net *net, struct sock *sk, struct sk_buff *skb) 139 { 140 struct dst_entry *dst = skb_dst(skb); 141 struct bpf_lwt *bpf; 142 int ret; 143 144 bpf = bpf_lwt_lwtunnel(dst->lwtstate); 145 if (bpf->out.prog) { 146 ret = run_lwt_bpf(skb, &bpf->out, dst, NO_REDIRECT); 147 if (ret < 0) 148 return ret; 149 } 150 151 if (unlikely(!dst->lwtstate->orig_output)) { 152 pr_warn_once("orig_output not set on dst for prog %s\n", 153 bpf->out.name); 154 kfree_skb(skb); 155 return -EINVAL; 156 } 157 158 return dst->lwtstate->orig_output(net, sk, skb); 159 } 160 161 static int xmit_check_hhlen(struct sk_buff *skb) 162 { 163 int hh_len = skb_dst(skb)->dev->hard_header_len; 164 165 if (skb_headroom(skb) < hh_len) { 166 int nhead = HH_DATA_ALIGN(hh_len - skb_headroom(skb)); 167 168 if (pskb_expand_head(skb, nhead, 0, GFP_ATOMIC)) 169 return -ENOMEM; 170 } 171 172 return 0; 173 } 174 175 static int bpf_lwt_xmit_reroute(struct sk_buff *skb) 176 { 177 struct net_device *l3mdev = l3mdev_master_dev_rcu(skb_dst(skb)->dev); 178 int oif = l3mdev ? l3mdev->ifindex : 0; 179 struct dst_entry *dst = NULL; 180 int err = -EAFNOSUPPORT; 181 struct sock *sk; 182 struct net *net; 183 bool ipv4; 184 185 if (skb->protocol == htons(ETH_P_IP)) 186 ipv4 = true; 187 else if (skb->protocol == htons(ETH_P_IPV6)) 188 ipv4 = false; 189 else 190 goto err; 191 192 sk = sk_to_full_sk(skb->sk); 193 if (sk) { 194 if (sk->sk_bound_dev_if) 195 oif = sk->sk_bound_dev_if; 196 net = sock_net(sk); 197 } else { 198 net = dev_net(skb_dst(skb)->dev); 199 } 200 201 if (ipv4) { 202 struct iphdr *iph = ip_hdr(skb); 203 struct flowi4 fl4 = {}; 204 struct rtable *rt; 205 206 fl4.flowi4_oif = oif; 207 fl4.flowi4_mark = skb->mark; 208 fl4.flowi4_uid = sock_net_uid(net, sk); 209 fl4.flowi4_tos = RT_TOS(iph->tos); 210 fl4.flowi4_flags = FLOWI_FLAG_ANYSRC; 211 fl4.flowi4_proto = iph->protocol; 212 fl4.daddr = iph->daddr; 213 fl4.saddr = iph->saddr; 214 215 rt = ip_route_output_key(net, &fl4); 216 if (IS_ERR(rt)) { 217 err = PTR_ERR(rt); 218 goto err; 219 } 220 dst = &rt->dst; 221 } else { 222 struct ipv6hdr *iph6 = ipv6_hdr(skb); 223 struct flowi6 fl6 = {}; 224 225 fl6.flowi6_oif = oif; 226 fl6.flowi6_mark = skb->mark; 227 fl6.flowi6_uid = sock_net_uid(net, sk); 228 fl6.flowlabel = ip6_flowinfo(iph6); 229 fl6.flowi6_proto = iph6->nexthdr; 230 fl6.daddr = iph6->daddr; 231 fl6.saddr = iph6->saddr; 232 233 err = ipv6_stub->ipv6_dst_lookup(net, skb->sk, &dst, &fl6); 234 if (unlikely(err)) 235 goto err; 236 if (IS_ERR(dst)) { 237 err = PTR_ERR(dst); 238 goto err; 239 } 240 } 241 if (unlikely(dst->error)) { 242 err = dst->error; 243 dst_release(dst); 244 goto err; 245 } 246 247 /* Although skb header was reserved in bpf_lwt_push_ip_encap(), it 248 * was done for the previous dst, so we are doing it here again, in 249 * case the new dst needs much more space. The call below is a noop 250 * if there is enough header space in skb. 251 */ 252 err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev)); 253 if (unlikely(err)) 254 goto err; 255 256 skb_dst_drop(skb); 257 skb_dst_set(skb, dst); 258 259 err = dst_output(dev_net(skb_dst(skb)->dev), skb->sk, skb); 260 if (unlikely(err)) 261 return err; 262 263 /* ip[6]_finish_output2 understand LWTUNNEL_XMIT_DONE */ 264 return LWTUNNEL_XMIT_DONE; 265 266 err: 267 kfree_skb(skb); 268 return err; 269 } 270 271 static int bpf_xmit(struct sk_buff *skb) 272 { 273 struct dst_entry *dst = skb_dst(skb); 274 struct bpf_lwt *bpf; 275 276 bpf = bpf_lwt_lwtunnel(dst->lwtstate); 277 if (bpf->xmit.prog) { 278 __be16 proto = skb->protocol; 279 int ret; 280 281 ret = run_lwt_bpf(skb, &bpf->xmit, dst, CAN_REDIRECT); 282 switch (ret) { 283 case BPF_OK: 284 /* If the header changed, e.g. via bpf_lwt_push_encap, 285 * BPF_LWT_REROUTE below should have been used if the 286 * protocol was also changed. 287 */ 288 if (skb->protocol != proto) { 289 kfree_skb(skb); 290 return -EINVAL; 291 } 292 /* If the header was expanded, headroom might be too 293 * small for L2 header to come, expand as needed. 294 */ 295 ret = xmit_check_hhlen(skb); 296 if (unlikely(ret)) 297 return ret; 298 299 return LWTUNNEL_XMIT_CONTINUE; 300 case BPF_REDIRECT: 301 return LWTUNNEL_XMIT_DONE; 302 case BPF_LWT_REROUTE: 303 return bpf_lwt_xmit_reroute(skb); 304 default: 305 return ret; 306 } 307 } 308 309 return LWTUNNEL_XMIT_CONTINUE; 310 } 311 312 static void bpf_lwt_prog_destroy(struct bpf_lwt_prog *prog) 313 { 314 if (prog->prog) 315 bpf_prog_put(prog->prog); 316 317 kfree(prog->name); 318 } 319 320 static void bpf_destroy_state(struct lwtunnel_state *lwt) 321 { 322 struct bpf_lwt *bpf = bpf_lwt_lwtunnel(lwt); 323 324 bpf_lwt_prog_destroy(&bpf->in); 325 bpf_lwt_prog_destroy(&bpf->out); 326 bpf_lwt_prog_destroy(&bpf->xmit); 327 } 328 329 static const struct nla_policy bpf_prog_policy[LWT_BPF_PROG_MAX + 1] = { 330 [LWT_BPF_PROG_FD] = { .type = NLA_U32, }, 331 [LWT_BPF_PROG_NAME] = { .type = NLA_NUL_STRING, 332 .len = MAX_PROG_NAME }, 333 }; 334 335 static int bpf_parse_prog(struct nlattr *attr, struct bpf_lwt_prog *prog, 336 enum bpf_prog_type type) 337 { 338 struct nlattr *tb[LWT_BPF_PROG_MAX + 1]; 339 struct bpf_prog *p; 340 int ret; 341 u32 fd; 342 343 ret = nla_parse_nested_deprecated(tb, LWT_BPF_PROG_MAX, attr, 344 bpf_prog_policy, NULL); 345 if (ret < 0) 346 return ret; 347 348 if (!tb[LWT_BPF_PROG_FD] || !tb[LWT_BPF_PROG_NAME]) 349 return -EINVAL; 350 351 prog->name = nla_memdup(tb[LWT_BPF_PROG_NAME], GFP_ATOMIC); 352 if (!prog->name) 353 return -ENOMEM; 354 355 fd = nla_get_u32(tb[LWT_BPF_PROG_FD]); 356 p = bpf_prog_get_type(fd, type); 357 if (IS_ERR(p)) 358 return PTR_ERR(p); 359 360 prog->prog = p; 361 362 return 0; 363 } 364 365 static const struct nla_policy bpf_nl_policy[LWT_BPF_MAX + 1] = { 366 [LWT_BPF_IN] = { .type = NLA_NESTED, }, 367 [LWT_BPF_OUT] = { .type = NLA_NESTED, }, 368 [LWT_BPF_XMIT] = { .type = NLA_NESTED, }, 369 [LWT_BPF_XMIT_HEADROOM] = { .type = NLA_U32 }, 370 }; 371 372 static int bpf_build_state(struct nlattr *nla, 373 unsigned int family, const void *cfg, 374 struct lwtunnel_state **ts, 375 struct netlink_ext_ack *extack) 376 { 377 struct nlattr *tb[LWT_BPF_MAX + 1]; 378 struct lwtunnel_state *newts; 379 struct bpf_lwt *bpf; 380 int ret; 381 382 if (family != AF_INET && family != AF_INET6) 383 return -EAFNOSUPPORT; 384 385 ret = nla_parse_nested_deprecated(tb, LWT_BPF_MAX, nla, bpf_nl_policy, 386 extack); 387 if (ret < 0) 388 return ret; 389 390 if (!tb[LWT_BPF_IN] && !tb[LWT_BPF_OUT] && !tb[LWT_BPF_XMIT]) 391 return -EINVAL; 392 393 newts = lwtunnel_state_alloc(sizeof(*bpf)); 394 if (!newts) 395 return -ENOMEM; 396 397 newts->type = LWTUNNEL_ENCAP_BPF; 398 bpf = bpf_lwt_lwtunnel(newts); 399 400 if (tb[LWT_BPF_IN]) { 401 newts->flags |= LWTUNNEL_STATE_INPUT_REDIRECT; 402 ret = bpf_parse_prog(tb[LWT_BPF_IN], &bpf->in, 403 BPF_PROG_TYPE_LWT_IN); 404 if (ret < 0) 405 goto errout; 406 } 407 408 if (tb[LWT_BPF_OUT]) { 409 newts->flags |= LWTUNNEL_STATE_OUTPUT_REDIRECT; 410 ret = bpf_parse_prog(tb[LWT_BPF_OUT], &bpf->out, 411 BPF_PROG_TYPE_LWT_OUT); 412 if (ret < 0) 413 goto errout; 414 } 415 416 if (tb[LWT_BPF_XMIT]) { 417 newts->flags |= LWTUNNEL_STATE_XMIT_REDIRECT; 418 ret = bpf_parse_prog(tb[LWT_BPF_XMIT], &bpf->xmit, 419 BPF_PROG_TYPE_LWT_XMIT); 420 if (ret < 0) 421 goto errout; 422 } 423 424 if (tb[LWT_BPF_XMIT_HEADROOM]) { 425 u32 headroom = nla_get_u32(tb[LWT_BPF_XMIT_HEADROOM]); 426 427 if (headroom > LWT_BPF_MAX_HEADROOM) { 428 ret = -ERANGE; 429 goto errout; 430 } 431 432 newts->headroom = headroom; 433 } 434 435 bpf->family = family; 436 *ts = newts; 437 438 return 0; 439 440 errout: 441 bpf_destroy_state(newts); 442 kfree(newts); 443 return ret; 444 } 445 446 static int bpf_fill_lwt_prog(struct sk_buff *skb, int attr, 447 struct bpf_lwt_prog *prog) 448 { 449 struct nlattr *nest; 450 451 if (!prog->prog) 452 return 0; 453 454 nest = nla_nest_start_noflag(skb, attr); 455 if (!nest) 456 return -EMSGSIZE; 457 458 if (prog->name && 459 nla_put_string(skb, LWT_BPF_PROG_NAME, prog->name)) 460 return -EMSGSIZE; 461 462 return nla_nest_end(skb, nest); 463 } 464 465 static int bpf_fill_encap_info(struct sk_buff *skb, struct lwtunnel_state *lwt) 466 { 467 struct bpf_lwt *bpf = bpf_lwt_lwtunnel(lwt); 468 469 if (bpf_fill_lwt_prog(skb, LWT_BPF_IN, &bpf->in) < 0 || 470 bpf_fill_lwt_prog(skb, LWT_BPF_OUT, &bpf->out) < 0 || 471 bpf_fill_lwt_prog(skb, LWT_BPF_XMIT, &bpf->xmit) < 0) 472 return -EMSGSIZE; 473 474 return 0; 475 } 476 477 static int bpf_encap_nlsize(struct lwtunnel_state *lwtstate) 478 { 479 int nest_len = nla_total_size(sizeof(struct nlattr)) + 480 nla_total_size(MAX_PROG_NAME) + /* LWT_BPF_PROG_NAME */ 481 0; 482 483 return nest_len + /* LWT_BPF_IN */ 484 nest_len + /* LWT_BPF_OUT */ 485 nest_len + /* LWT_BPF_XMIT */ 486 0; 487 } 488 489 static int bpf_lwt_prog_cmp(struct bpf_lwt_prog *a, struct bpf_lwt_prog *b) 490 { 491 /* FIXME: 492 * The LWT state is currently rebuilt for delete requests which 493 * results in a new bpf_prog instance. Comparing names for now. 494 */ 495 if (!a->name && !b->name) 496 return 0; 497 498 if (!a->name || !b->name) 499 return 1; 500 501 return strcmp(a->name, b->name); 502 } 503 504 static int bpf_encap_cmp(struct lwtunnel_state *a, struct lwtunnel_state *b) 505 { 506 struct bpf_lwt *a_bpf = bpf_lwt_lwtunnel(a); 507 struct bpf_lwt *b_bpf = bpf_lwt_lwtunnel(b); 508 509 return bpf_lwt_prog_cmp(&a_bpf->in, &b_bpf->in) || 510 bpf_lwt_prog_cmp(&a_bpf->out, &b_bpf->out) || 511 bpf_lwt_prog_cmp(&a_bpf->xmit, &b_bpf->xmit); 512 } 513 514 static const struct lwtunnel_encap_ops bpf_encap_ops = { 515 .build_state = bpf_build_state, 516 .destroy_state = bpf_destroy_state, 517 .input = bpf_input, 518 .output = bpf_output, 519 .xmit = bpf_xmit, 520 .fill_encap = bpf_fill_encap_info, 521 .get_encap_size = bpf_encap_nlsize, 522 .cmp_encap = bpf_encap_cmp, 523 .owner = THIS_MODULE, 524 }; 525 526 static int handle_gso_type(struct sk_buff *skb, unsigned int gso_type, 527 int encap_len) 528 { 529 struct skb_shared_info *shinfo = skb_shinfo(skb); 530 531 gso_type |= SKB_GSO_DODGY; 532 shinfo->gso_type |= gso_type; 533 skb_decrease_gso_size(shinfo, encap_len); 534 shinfo->gso_segs = 0; 535 return 0; 536 } 537 538 static int handle_gso_encap(struct sk_buff *skb, bool ipv4, int encap_len) 539 { 540 int next_hdr_offset; 541 void *next_hdr; 542 __u8 protocol; 543 544 /* SCTP and UDP_L4 gso need more nuanced handling than what 545 * handle_gso_type() does above: skb_decrease_gso_size() is not enough. 546 * So at the moment only TCP GSO packets are let through. 547 */ 548 if (!(skb_shinfo(skb)->gso_type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6))) 549 return -ENOTSUPP; 550 551 if (ipv4) { 552 protocol = ip_hdr(skb)->protocol; 553 next_hdr_offset = sizeof(struct iphdr); 554 next_hdr = skb_network_header(skb) + next_hdr_offset; 555 } else { 556 protocol = ipv6_hdr(skb)->nexthdr; 557 next_hdr_offset = sizeof(struct ipv6hdr); 558 next_hdr = skb_network_header(skb) + next_hdr_offset; 559 } 560 561 switch (protocol) { 562 case IPPROTO_GRE: 563 next_hdr_offset += sizeof(struct gre_base_hdr); 564 if (next_hdr_offset > encap_len) 565 return -EINVAL; 566 567 if (((struct gre_base_hdr *)next_hdr)->flags & GRE_CSUM) 568 return handle_gso_type(skb, SKB_GSO_GRE_CSUM, 569 encap_len); 570 return handle_gso_type(skb, SKB_GSO_GRE, encap_len); 571 572 case IPPROTO_UDP: 573 next_hdr_offset += sizeof(struct udphdr); 574 if (next_hdr_offset > encap_len) 575 return -EINVAL; 576 577 if (((struct udphdr *)next_hdr)->check) 578 return handle_gso_type(skb, SKB_GSO_UDP_TUNNEL_CSUM, 579 encap_len); 580 return handle_gso_type(skb, SKB_GSO_UDP_TUNNEL, encap_len); 581 582 case IPPROTO_IP: 583 case IPPROTO_IPV6: 584 if (ipv4) 585 return handle_gso_type(skb, SKB_GSO_IPXIP4, encap_len); 586 else 587 return handle_gso_type(skb, SKB_GSO_IPXIP6, encap_len); 588 589 default: 590 return -EPROTONOSUPPORT; 591 } 592 } 593 594 int bpf_lwt_push_ip_encap(struct sk_buff *skb, void *hdr, u32 len, bool ingress) 595 { 596 struct iphdr *iph; 597 bool ipv4; 598 int err; 599 600 if (unlikely(len < sizeof(struct iphdr) || len > LWT_BPF_MAX_HEADROOM)) 601 return -EINVAL; 602 603 /* validate protocol and length */ 604 iph = (struct iphdr *)hdr; 605 if (iph->version == 4) { 606 ipv4 = true; 607 if (unlikely(len < iph->ihl * 4)) 608 return -EINVAL; 609 } else if (iph->version == 6) { 610 ipv4 = false; 611 if (unlikely(len < sizeof(struct ipv6hdr))) 612 return -EINVAL; 613 } else { 614 return -EINVAL; 615 } 616 617 if (ingress) 618 err = skb_cow_head(skb, len + skb->mac_len); 619 else 620 err = skb_cow_head(skb, 621 len + LL_RESERVED_SPACE(skb_dst(skb)->dev)); 622 if (unlikely(err)) 623 return err; 624 625 /* push the encap headers and fix pointers */ 626 skb_reset_inner_headers(skb); 627 skb_reset_inner_mac_header(skb); /* mac header is not yet set */ 628 skb_set_inner_protocol(skb, skb->protocol); 629 skb->encapsulation = 1; 630 skb_push(skb, len); 631 if (ingress) 632 skb_postpush_rcsum(skb, iph, len); 633 skb_reset_network_header(skb); 634 memcpy(skb_network_header(skb), hdr, len); 635 bpf_compute_data_pointers(skb); 636 skb_clear_hash(skb); 637 638 if (ipv4) { 639 skb->protocol = htons(ETH_P_IP); 640 iph = ip_hdr(skb); 641 642 if (!iph->check) 643 iph->check = ip_fast_csum((unsigned char *)iph, 644 iph->ihl); 645 } else { 646 skb->protocol = htons(ETH_P_IPV6); 647 } 648 649 if (skb_is_gso(skb)) 650 return handle_gso_encap(skb, ipv4, len); 651 652 return 0; 653 } 654 655 static int __init bpf_lwt_init(void) 656 { 657 return lwtunnel_encap_add_ops(&bpf_encap_ops, LWTUNNEL_ENCAP_BPF); 658 } 659 660 subsys_initcall(bpf_lwt_init) 661