1 // SPDX-License-Identifier: GPL-2.0-only 2 /* Copyright (c) 2016 Thomas Graf <tgraf@tgraf.ch> 3 */ 4 5 #include <linux/filter.h> 6 #include <linux/kernel.h> 7 #include <linux/module.h> 8 #include <linux/skbuff.h> 9 #include <linux/types.h> 10 #include <linux/bpf.h> 11 #include <net/lwtunnel.h> 12 #include <net/gre.h> 13 #include <net/ip6_route.h> 14 #include <net/ipv6_stubs.h> 15 16 struct bpf_lwt_prog { 17 struct bpf_prog *prog; 18 char *name; 19 }; 20 21 struct bpf_lwt { 22 struct bpf_lwt_prog in; 23 struct bpf_lwt_prog out; 24 struct bpf_lwt_prog xmit; 25 int family; 26 }; 27 28 #define MAX_PROG_NAME 256 29 30 static inline struct bpf_lwt *bpf_lwt_lwtunnel(struct lwtunnel_state *lwt) 31 { 32 return (struct bpf_lwt *)lwt->data; 33 } 34 35 #define NO_REDIRECT false 36 #define CAN_REDIRECT true 37 38 static int run_lwt_bpf(struct sk_buff *skb, struct bpf_lwt_prog *lwt, 39 struct dst_entry *dst, bool can_redirect) 40 { 41 int ret; 42 43 /* Migration disable and BH disable are needed to protect per-cpu 44 * redirect_info between BPF prog and skb_do_redirect(). 45 */ 46 migrate_disable(); 47 local_bh_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 skb_do_redirect(skb); 64 ret = BPF_REDIRECT; 65 } 66 break; 67 68 case BPF_DROP: 69 kfree_skb(skb); 70 ret = -EPERM; 71 break; 72 73 default: 74 pr_warn_once("bpf-lwt: Illegal return value %u, expect packet loss\n", ret); 75 kfree_skb(skb); 76 ret = -EINVAL; 77 break; 78 } 79 80 local_bh_enable(); 81 migrate_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, int hh_len) 162 { 163 if (skb_headroom(skb) < hh_len) { 164 int nhead = HH_DATA_ALIGN(hh_len - skb_headroom(skb)); 165 166 if (pskb_expand_head(skb, nhead, 0, GFP_ATOMIC)) 167 return -ENOMEM; 168 } 169 170 return 0; 171 } 172 173 static int bpf_lwt_xmit_reroute(struct sk_buff *skb) 174 { 175 struct net_device *l3mdev = l3mdev_master_dev_rcu(skb_dst(skb)->dev); 176 int oif = l3mdev ? l3mdev->ifindex : 0; 177 struct dst_entry *dst = NULL; 178 int err = -EAFNOSUPPORT; 179 struct sock *sk; 180 struct net *net; 181 bool ipv4; 182 183 if (skb->protocol == htons(ETH_P_IP)) 184 ipv4 = true; 185 else if (skb->protocol == htons(ETH_P_IPV6)) 186 ipv4 = false; 187 else 188 goto err; 189 190 sk = sk_to_full_sk(skb->sk); 191 if (sk) { 192 if (sk->sk_bound_dev_if) 193 oif = sk->sk_bound_dev_if; 194 net = sock_net(sk); 195 } else { 196 net = dev_net(skb_dst(skb)->dev); 197 } 198 199 if (ipv4) { 200 struct iphdr *iph = ip_hdr(skb); 201 struct flowi4 fl4 = {}; 202 struct rtable *rt; 203 204 fl4.flowi4_oif = oif; 205 fl4.flowi4_mark = skb->mark; 206 fl4.flowi4_uid = sock_net_uid(net, sk); 207 fl4.flowi4_tos = RT_TOS(iph->tos); 208 fl4.flowi4_flags = FLOWI_FLAG_ANYSRC; 209 fl4.flowi4_proto = iph->protocol; 210 fl4.daddr = iph->daddr; 211 fl4.saddr = iph->saddr; 212 213 rt = ip_route_output_key(net, &fl4); 214 if (IS_ERR(rt)) { 215 err = PTR_ERR(rt); 216 goto err; 217 } 218 dst = &rt->dst; 219 } else { 220 struct ipv6hdr *iph6 = ipv6_hdr(skb); 221 struct flowi6 fl6 = {}; 222 223 fl6.flowi6_oif = oif; 224 fl6.flowi6_mark = skb->mark; 225 fl6.flowi6_uid = sock_net_uid(net, sk); 226 fl6.flowlabel = ip6_flowinfo(iph6); 227 fl6.flowi6_proto = iph6->nexthdr; 228 fl6.daddr = iph6->daddr; 229 fl6.saddr = iph6->saddr; 230 231 dst = ipv6_stub->ipv6_dst_lookup_flow(net, skb->sk, &fl6, NULL); 232 if (IS_ERR(dst)) { 233 err = PTR_ERR(dst); 234 goto err; 235 } 236 } 237 if (unlikely(dst->error)) { 238 err = dst->error; 239 dst_release(dst); 240 goto err; 241 } 242 243 /* Although skb header was reserved in bpf_lwt_push_ip_encap(), it 244 * was done for the previous dst, so we are doing it here again, in 245 * case the new dst needs much more space. The call below is a noop 246 * if there is enough header space in skb. 247 */ 248 err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev)); 249 if (unlikely(err)) 250 goto err; 251 252 skb_dst_drop(skb); 253 skb_dst_set(skb, dst); 254 255 err = dst_output(dev_net(skb_dst(skb)->dev), skb->sk, skb); 256 if (unlikely(err)) 257 return net_xmit_errno(err); 258 259 /* ip[6]_finish_output2 understand LWTUNNEL_XMIT_DONE */ 260 return LWTUNNEL_XMIT_DONE; 261 262 err: 263 kfree_skb(skb); 264 return err; 265 } 266 267 static int bpf_xmit(struct sk_buff *skb) 268 { 269 struct dst_entry *dst = skb_dst(skb); 270 struct bpf_lwt *bpf; 271 272 bpf = bpf_lwt_lwtunnel(dst->lwtstate); 273 if (bpf->xmit.prog) { 274 int hh_len = dst->dev->hard_header_len; 275 __be16 proto = skb->protocol; 276 int ret; 277 278 ret = run_lwt_bpf(skb, &bpf->xmit, dst, CAN_REDIRECT); 279 switch (ret) { 280 case BPF_OK: 281 /* If the header changed, e.g. via bpf_lwt_push_encap, 282 * BPF_LWT_REROUTE below should have been used if the 283 * protocol was also changed. 284 */ 285 if (skb->protocol != proto) { 286 kfree_skb(skb); 287 return -EINVAL; 288 } 289 /* If the header was expanded, headroom might be too 290 * small for L2 header to come, expand as needed. 291 */ 292 ret = xmit_check_hhlen(skb, hh_len); 293 if (unlikely(ret)) 294 return ret; 295 296 return LWTUNNEL_XMIT_CONTINUE; 297 case BPF_REDIRECT: 298 return LWTUNNEL_XMIT_DONE; 299 case BPF_LWT_REROUTE: 300 return bpf_lwt_xmit_reroute(skb); 301 default: 302 return ret; 303 } 304 } 305 306 return LWTUNNEL_XMIT_CONTINUE; 307 } 308 309 static void bpf_lwt_prog_destroy(struct bpf_lwt_prog *prog) 310 { 311 if (prog->prog) 312 bpf_prog_put(prog->prog); 313 314 kfree(prog->name); 315 } 316 317 static void bpf_destroy_state(struct lwtunnel_state *lwt) 318 { 319 struct bpf_lwt *bpf = bpf_lwt_lwtunnel(lwt); 320 321 bpf_lwt_prog_destroy(&bpf->in); 322 bpf_lwt_prog_destroy(&bpf->out); 323 bpf_lwt_prog_destroy(&bpf->xmit); 324 } 325 326 static const struct nla_policy bpf_prog_policy[LWT_BPF_PROG_MAX + 1] = { 327 [LWT_BPF_PROG_FD] = { .type = NLA_U32, }, 328 [LWT_BPF_PROG_NAME] = { .type = NLA_NUL_STRING, 329 .len = MAX_PROG_NAME }, 330 }; 331 332 static int bpf_parse_prog(struct nlattr *attr, struct bpf_lwt_prog *prog, 333 enum bpf_prog_type type) 334 { 335 struct nlattr *tb[LWT_BPF_PROG_MAX + 1]; 336 struct bpf_prog *p; 337 int ret; 338 u32 fd; 339 340 ret = nla_parse_nested_deprecated(tb, LWT_BPF_PROG_MAX, attr, 341 bpf_prog_policy, NULL); 342 if (ret < 0) 343 return ret; 344 345 if (!tb[LWT_BPF_PROG_FD] || !tb[LWT_BPF_PROG_NAME]) 346 return -EINVAL; 347 348 prog->name = nla_memdup(tb[LWT_BPF_PROG_NAME], GFP_ATOMIC); 349 if (!prog->name) 350 return -ENOMEM; 351 352 fd = nla_get_u32(tb[LWT_BPF_PROG_FD]); 353 p = bpf_prog_get_type(fd, type); 354 if (IS_ERR(p)) 355 return PTR_ERR(p); 356 357 prog->prog = p; 358 359 return 0; 360 } 361 362 static const struct nla_policy bpf_nl_policy[LWT_BPF_MAX + 1] = { 363 [LWT_BPF_IN] = { .type = NLA_NESTED, }, 364 [LWT_BPF_OUT] = { .type = NLA_NESTED, }, 365 [LWT_BPF_XMIT] = { .type = NLA_NESTED, }, 366 [LWT_BPF_XMIT_HEADROOM] = { .type = NLA_U32 }, 367 }; 368 369 static int bpf_build_state(struct net *net, struct nlattr *nla, 370 unsigned int family, const void *cfg, 371 struct lwtunnel_state **ts, 372 struct netlink_ext_ack *extack) 373 { 374 struct nlattr *tb[LWT_BPF_MAX + 1]; 375 struct lwtunnel_state *newts; 376 struct bpf_lwt *bpf; 377 int ret; 378 379 if (family != AF_INET && family != AF_INET6) 380 return -EAFNOSUPPORT; 381 382 ret = nla_parse_nested_deprecated(tb, LWT_BPF_MAX, nla, bpf_nl_policy, 383 extack); 384 if (ret < 0) 385 return ret; 386 387 if (!tb[LWT_BPF_IN] && !tb[LWT_BPF_OUT] && !tb[LWT_BPF_XMIT]) 388 return -EINVAL; 389 390 newts = lwtunnel_state_alloc(sizeof(*bpf)); 391 if (!newts) 392 return -ENOMEM; 393 394 newts->type = LWTUNNEL_ENCAP_BPF; 395 bpf = bpf_lwt_lwtunnel(newts); 396 397 if (tb[LWT_BPF_IN]) { 398 newts->flags |= LWTUNNEL_STATE_INPUT_REDIRECT; 399 ret = bpf_parse_prog(tb[LWT_BPF_IN], &bpf->in, 400 BPF_PROG_TYPE_LWT_IN); 401 if (ret < 0) 402 goto errout; 403 } 404 405 if (tb[LWT_BPF_OUT]) { 406 newts->flags |= LWTUNNEL_STATE_OUTPUT_REDIRECT; 407 ret = bpf_parse_prog(tb[LWT_BPF_OUT], &bpf->out, 408 BPF_PROG_TYPE_LWT_OUT); 409 if (ret < 0) 410 goto errout; 411 } 412 413 if (tb[LWT_BPF_XMIT]) { 414 newts->flags |= LWTUNNEL_STATE_XMIT_REDIRECT; 415 ret = bpf_parse_prog(tb[LWT_BPF_XMIT], &bpf->xmit, 416 BPF_PROG_TYPE_LWT_XMIT); 417 if (ret < 0) 418 goto errout; 419 } 420 421 if (tb[LWT_BPF_XMIT_HEADROOM]) { 422 u32 headroom = nla_get_u32(tb[LWT_BPF_XMIT_HEADROOM]); 423 424 if (headroom > LWT_BPF_MAX_HEADROOM) { 425 ret = -ERANGE; 426 goto errout; 427 } 428 429 newts->headroom = headroom; 430 } 431 432 bpf->family = family; 433 *ts = newts; 434 435 return 0; 436 437 errout: 438 bpf_destroy_state(newts); 439 kfree(newts); 440 return ret; 441 } 442 443 static int bpf_fill_lwt_prog(struct sk_buff *skb, int attr, 444 struct bpf_lwt_prog *prog) 445 { 446 struct nlattr *nest; 447 448 if (!prog->prog) 449 return 0; 450 451 nest = nla_nest_start_noflag(skb, attr); 452 if (!nest) 453 return -EMSGSIZE; 454 455 if (prog->name && 456 nla_put_string(skb, LWT_BPF_PROG_NAME, prog->name)) 457 return -EMSGSIZE; 458 459 return nla_nest_end(skb, nest); 460 } 461 462 static int bpf_fill_encap_info(struct sk_buff *skb, struct lwtunnel_state *lwt) 463 { 464 struct bpf_lwt *bpf = bpf_lwt_lwtunnel(lwt); 465 466 if (bpf_fill_lwt_prog(skb, LWT_BPF_IN, &bpf->in) < 0 || 467 bpf_fill_lwt_prog(skb, LWT_BPF_OUT, &bpf->out) < 0 || 468 bpf_fill_lwt_prog(skb, LWT_BPF_XMIT, &bpf->xmit) < 0) 469 return -EMSGSIZE; 470 471 return 0; 472 } 473 474 static int bpf_encap_nlsize(struct lwtunnel_state *lwtstate) 475 { 476 int nest_len = nla_total_size(sizeof(struct nlattr)) + 477 nla_total_size(MAX_PROG_NAME) + /* LWT_BPF_PROG_NAME */ 478 0; 479 480 return nest_len + /* LWT_BPF_IN */ 481 nest_len + /* LWT_BPF_OUT */ 482 nest_len + /* LWT_BPF_XMIT */ 483 0; 484 } 485 486 static int bpf_lwt_prog_cmp(struct bpf_lwt_prog *a, struct bpf_lwt_prog *b) 487 { 488 /* FIXME: 489 * The LWT state is currently rebuilt for delete requests which 490 * results in a new bpf_prog instance. Comparing names for now. 491 */ 492 if (!a->name && !b->name) 493 return 0; 494 495 if (!a->name || !b->name) 496 return 1; 497 498 return strcmp(a->name, b->name); 499 } 500 501 static int bpf_encap_cmp(struct lwtunnel_state *a, struct lwtunnel_state *b) 502 { 503 struct bpf_lwt *a_bpf = bpf_lwt_lwtunnel(a); 504 struct bpf_lwt *b_bpf = bpf_lwt_lwtunnel(b); 505 506 return bpf_lwt_prog_cmp(&a_bpf->in, &b_bpf->in) || 507 bpf_lwt_prog_cmp(&a_bpf->out, &b_bpf->out) || 508 bpf_lwt_prog_cmp(&a_bpf->xmit, &b_bpf->xmit); 509 } 510 511 static const struct lwtunnel_encap_ops bpf_encap_ops = { 512 .build_state = bpf_build_state, 513 .destroy_state = bpf_destroy_state, 514 .input = bpf_input, 515 .output = bpf_output, 516 .xmit = bpf_xmit, 517 .fill_encap = bpf_fill_encap_info, 518 .get_encap_size = bpf_encap_nlsize, 519 .cmp_encap = bpf_encap_cmp, 520 .owner = THIS_MODULE, 521 }; 522 523 static int handle_gso_type(struct sk_buff *skb, unsigned int gso_type, 524 int encap_len) 525 { 526 struct skb_shared_info *shinfo = skb_shinfo(skb); 527 528 gso_type |= SKB_GSO_DODGY; 529 shinfo->gso_type |= gso_type; 530 skb_decrease_gso_size(shinfo, encap_len); 531 shinfo->gso_segs = 0; 532 return 0; 533 } 534 535 static int handle_gso_encap(struct sk_buff *skb, bool ipv4, int encap_len) 536 { 537 int next_hdr_offset; 538 void *next_hdr; 539 __u8 protocol; 540 541 /* SCTP and UDP_L4 gso need more nuanced handling than what 542 * handle_gso_type() does above: skb_decrease_gso_size() is not enough. 543 * So at the moment only TCP GSO packets are let through. 544 */ 545 if (!(skb_shinfo(skb)->gso_type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6))) 546 return -ENOTSUPP; 547 548 if (ipv4) { 549 protocol = ip_hdr(skb)->protocol; 550 next_hdr_offset = sizeof(struct iphdr); 551 next_hdr = skb_network_header(skb) + next_hdr_offset; 552 } else { 553 protocol = ipv6_hdr(skb)->nexthdr; 554 next_hdr_offset = sizeof(struct ipv6hdr); 555 next_hdr = skb_network_header(skb) + next_hdr_offset; 556 } 557 558 switch (protocol) { 559 case IPPROTO_GRE: 560 next_hdr_offset += sizeof(struct gre_base_hdr); 561 if (next_hdr_offset > encap_len) 562 return -EINVAL; 563 564 if (((struct gre_base_hdr *)next_hdr)->flags & GRE_CSUM) 565 return handle_gso_type(skb, SKB_GSO_GRE_CSUM, 566 encap_len); 567 return handle_gso_type(skb, SKB_GSO_GRE, encap_len); 568 569 case IPPROTO_UDP: 570 next_hdr_offset += sizeof(struct udphdr); 571 if (next_hdr_offset > encap_len) 572 return -EINVAL; 573 574 if (((struct udphdr *)next_hdr)->check) 575 return handle_gso_type(skb, SKB_GSO_UDP_TUNNEL_CSUM, 576 encap_len); 577 return handle_gso_type(skb, SKB_GSO_UDP_TUNNEL, encap_len); 578 579 case IPPROTO_IP: 580 case IPPROTO_IPV6: 581 if (ipv4) 582 return handle_gso_type(skb, SKB_GSO_IPXIP4, encap_len); 583 else 584 return handle_gso_type(skb, SKB_GSO_IPXIP6, encap_len); 585 586 default: 587 return -EPROTONOSUPPORT; 588 } 589 } 590 591 int bpf_lwt_push_ip_encap(struct sk_buff *skb, void *hdr, u32 len, bool ingress) 592 { 593 struct iphdr *iph; 594 bool ipv4; 595 int err; 596 597 if (unlikely(len < sizeof(struct iphdr) || len > LWT_BPF_MAX_HEADROOM)) 598 return -EINVAL; 599 600 /* validate protocol and length */ 601 iph = (struct iphdr *)hdr; 602 if (iph->version == 4) { 603 ipv4 = true; 604 if (unlikely(len < iph->ihl * 4)) 605 return -EINVAL; 606 } else if (iph->version == 6) { 607 ipv4 = false; 608 if (unlikely(len < sizeof(struct ipv6hdr))) 609 return -EINVAL; 610 } else { 611 return -EINVAL; 612 } 613 614 if (ingress) 615 err = skb_cow_head(skb, len + skb->mac_len); 616 else 617 err = skb_cow_head(skb, 618 len + LL_RESERVED_SPACE(skb_dst(skb)->dev)); 619 if (unlikely(err)) 620 return err; 621 622 /* push the encap headers and fix pointers */ 623 skb_reset_inner_headers(skb); 624 skb_reset_inner_mac_header(skb); /* mac header is not yet set */ 625 skb_set_inner_protocol(skb, skb->protocol); 626 skb->encapsulation = 1; 627 skb_push(skb, len); 628 if (ingress) 629 skb_postpush_rcsum(skb, iph, len); 630 skb_reset_network_header(skb); 631 memcpy(skb_network_header(skb), hdr, len); 632 bpf_compute_data_pointers(skb); 633 skb_clear_hash(skb); 634 635 if (ipv4) { 636 skb->protocol = htons(ETH_P_IP); 637 iph = ip_hdr(skb); 638 639 if (!iph->check) 640 iph->check = ip_fast_csum((unsigned char *)iph, 641 iph->ihl); 642 } else { 643 skb->protocol = htons(ETH_P_IPV6); 644 } 645 646 if (skb_is_gso(skb)) 647 return handle_gso_encap(skb, ipv4, len); 648 649 return 0; 650 } 651 652 static int __init bpf_lwt_init(void) 653 { 654 return lwtunnel_encap_add_ops(&bpf_encap_ops, LWTUNNEL_ENCAP_BPF); 655 } 656 657 subsys_initcall(bpf_lwt_init) 658