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 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 local_bh_enable(); 82 migrate_enable(); 83 84 return ret; 85 } 86 87 static int bpf_lwt_input_reroute(struct sk_buff *skb) 88 { 89 int err = -EINVAL; 90 91 if (skb->protocol == htons(ETH_P_IP)) { 92 struct net_device *dev = skb_dst(skb)->dev; 93 struct iphdr *iph = ip_hdr(skb); 94 95 dev_hold(dev); 96 skb_dst_drop(skb); 97 err = ip_route_input_noref(skb, iph->daddr, iph->saddr, 98 iph->tos, dev); 99 dev_put(dev); 100 } else if (skb->protocol == htons(ETH_P_IPV6)) { 101 skb_dst_drop(skb); 102 err = ipv6_stub->ipv6_route_input(skb); 103 } else { 104 err = -EAFNOSUPPORT; 105 } 106 107 if (err) 108 goto err; 109 return dst_input(skb); 110 111 err: 112 kfree_skb(skb); 113 return err; 114 } 115 116 static int bpf_input(struct sk_buff *skb) 117 { 118 struct dst_entry *dst = skb_dst(skb); 119 struct bpf_lwt *bpf; 120 int ret; 121 122 bpf = bpf_lwt_lwtunnel(dst->lwtstate); 123 if (bpf->in.prog) { 124 ret = run_lwt_bpf(skb, &bpf->in, dst, NO_REDIRECT); 125 if (ret < 0) 126 return ret; 127 if (ret == BPF_LWT_REROUTE) 128 return bpf_lwt_input_reroute(skb); 129 } 130 131 if (unlikely(!dst->lwtstate->orig_input)) { 132 kfree_skb(skb); 133 return -EINVAL; 134 } 135 136 return dst->lwtstate->orig_input(skb); 137 } 138 139 static int bpf_output(struct net *net, struct sock *sk, struct sk_buff *skb) 140 { 141 struct dst_entry *dst = skb_dst(skb); 142 struct bpf_lwt *bpf; 143 int ret; 144 145 bpf = bpf_lwt_lwtunnel(dst->lwtstate); 146 if (bpf->out.prog) { 147 ret = run_lwt_bpf(skb, &bpf->out, dst, NO_REDIRECT); 148 if (ret < 0) 149 return ret; 150 } 151 152 if (unlikely(!dst->lwtstate->orig_output)) { 153 pr_warn_once("orig_output not set on dst for prog %s\n", 154 bpf->out.name); 155 kfree_skb(skb); 156 return -EINVAL; 157 } 158 159 return dst->lwtstate->orig_output(net, sk, skb); 160 } 161 162 static int xmit_check_hhlen(struct sk_buff *skb) 163 { 164 int hh_len = skb_dst(skb)->dev->hard_header_len; 165 166 if (skb_headroom(skb) < hh_len) { 167 int nhead = HH_DATA_ALIGN(hh_len - skb_headroom(skb)); 168 169 if (pskb_expand_head(skb, nhead, 0, GFP_ATOMIC)) 170 return -ENOMEM; 171 } 172 173 return 0; 174 } 175 176 static int bpf_lwt_xmit_reroute(struct sk_buff *skb) 177 { 178 struct net_device *l3mdev = l3mdev_master_dev_rcu(skb_dst(skb)->dev); 179 int oif = l3mdev ? l3mdev->ifindex : 0; 180 struct dst_entry *dst = NULL; 181 int err = -EAFNOSUPPORT; 182 struct sock *sk; 183 struct net *net; 184 bool ipv4; 185 186 if (skb->protocol == htons(ETH_P_IP)) 187 ipv4 = true; 188 else if (skb->protocol == htons(ETH_P_IPV6)) 189 ipv4 = false; 190 else 191 goto err; 192 193 sk = sk_to_full_sk(skb->sk); 194 if (sk) { 195 if (sk->sk_bound_dev_if) 196 oif = sk->sk_bound_dev_if; 197 net = sock_net(sk); 198 } else { 199 net = dev_net(skb_dst(skb)->dev); 200 } 201 202 if (ipv4) { 203 struct iphdr *iph = ip_hdr(skb); 204 struct flowi4 fl4 = {}; 205 struct rtable *rt; 206 207 fl4.flowi4_oif = oif; 208 fl4.flowi4_mark = skb->mark; 209 fl4.flowi4_uid = sock_net_uid(net, sk); 210 fl4.flowi4_tos = RT_TOS(iph->tos); 211 fl4.flowi4_flags = FLOWI_FLAG_ANYSRC; 212 fl4.flowi4_proto = iph->protocol; 213 fl4.daddr = iph->daddr; 214 fl4.saddr = iph->saddr; 215 216 rt = ip_route_output_key(net, &fl4); 217 if (IS_ERR(rt)) { 218 err = PTR_ERR(rt); 219 goto err; 220 } 221 dst = &rt->dst; 222 } else { 223 struct ipv6hdr *iph6 = ipv6_hdr(skb); 224 struct flowi6 fl6 = {}; 225 226 fl6.flowi6_oif = oif; 227 fl6.flowi6_mark = skb->mark; 228 fl6.flowi6_uid = sock_net_uid(net, sk); 229 fl6.flowlabel = ip6_flowinfo(iph6); 230 fl6.flowi6_proto = iph6->nexthdr; 231 fl6.daddr = iph6->daddr; 232 fl6.saddr = iph6->saddr; 233 234 dst = ipv6_stub->ipv6_dst_lookup_flow(net, skb->sk, &fl6, NULL); 235 if (IS_ERR(dst)) { 236 err = PTR_ERR(dst); 237 goto err; 238 } 239 } 240 if (unlikely(dst->error)) { 241 err = dst->error; 242 dst_release(dst); 243 goto err; 244 } 245 246 /* Although skb header was reserved in bpf_lwt_push_ip_encap(), it 247 * was done for the previous dst, so we are doing it here again, in 248 * case the new dst needs much more space. The call below is a noop 249 * if there is enough header space in skb. 250 */ 251 err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev)); 252 if (unlikely(err)) 253 goto err; 254 255 skb_dst_drop(skb); 256 skb_dst_set(skb, dst); 257 258 err = dst_output(dev_net(skb_dst(skb)->dev), skb->sk, skb); 259 if (unlikely(err)) 260 return err; 261 262 /* ip[6]_finish_output2 understand LWTUNNEL_XMIT_DONE */ 263 return LWTUNNEL_XMIT_DONE; 264 265 err: 266 kfree_skb(skb); 267 return err; 268 } 269 270 static int bpf_xmit(struct sk_buff *skb) 271 { 272 struct dst_entry *dst = skb_dst(skb); 273 struct bpf_lwt *bpf; 274 275 bpf = bpf_lwt_lwtunnel(dst->lwtstate); 276 if (bpf->xmit.prog) { 277 __be16 proto = skb->protocol; 278 int ret; 279 280 ret = run_lwt_bpf(skb, &bpf->xmit, dst, CAN_REDIRECT); 281 switch (ret) { 282 case BPF_OK: 283 /* If the header changed, e.g. via bpf_lwt_push_encap, 284 * BPF_LWT_REROUTE below should have been used if the 285 * protocol was also changed. 286 */ 287 if (skb->protocol != proto) { 288 kfree_skb(skb); 289 return -EINVAL; 290 } 291 /* If the header was expanded, headroom might be too 292 * small for L2 header to come, expand as needed. 293 */ 294 ret = xmit_check_hhlen(skb); 295 if (unlikely(ret)) 296 return ret; 297 298 return LWTUNNEL_XMIT_CONTINUE; 299 case BPF_REDIRECT: 300 return LWTUNNEL_XMIT_DONE; 301 case BPF_LWT_REROUTE: 302 return bpf_lwt_xmit_reroute(skb); 303 default: 304 return ret; 305 } 306 } 307 308 return LWTUNNEL_XMIT_CONTINUE; 309 } 310 311 static void bpf_lwt_prog_destroy(struct bpf_lwt_prog *prog) 312 { 313 if (prog->prog) 314 bpf_prog_put(prog->prog); 315 316 kfree(prog->name); 317 } 318 319 static void bpf_destroy_state(struct lwtunnel_state *lwt) 320 { 321 struct bpf_lwt *bpf = bpf_lwt_lwtunnel(lwt); 322 323 bpf_lwt_prog_destroy(&bpf->in); 324 bpf_lwt_prog_destroy(&bpf->out); 325 bpf_lwt_prog_destroy(&bpf->xmit); 326 } 327 328 static const struct nla_policy bpf_prog_policy[LWT_BPF_PROG_MAX + 1] = { 329 [LWT_BPF_PROG_FD] = { .type = NLA_U32, }, 330 [LWT_BPF_PROG_NAME] = { .type = NLA_NUL_STRING, 331 .len = MAX_PROG_NAME }, 332 }; 333 334 static int bpf_parse_prog(struct nlattr *attr, struct bpf_lwt_prog *prog, 335 enum bpf_prog_type type) 336 { 337 struct nlattr *tb[LWT_BPF_PROG_MAX + 1]; 338 struct bpf_prog *p; 339 int ret; 340 u32 fd; 341 342 ret = nla_parse_nested_deprecated(tb, LWT_BPF_PROG_MAX, attr, 343 bpf_prog_policy, NULL); 344 if (ret < 0) 345 return ret; 346 347 if (!tb[LWT_BPF_PROG_FD] || !tb[LWT_BPF_PROG_NAME]) 348 return -EINVAL; 349 350 prog->name = nla_memdup(tb[LWT_BPF_PROG_NAME], GFP_ATOMIC); 351 if (!prog->name) 352 return -ENOMEM; 353 354 fd = nla_get_u32(tb[LWT_BPF_PROG_FD]); 355 p = bpf_prog_get_type(fd, type); 356 if (IS_ERR(p)) 357 return PTR_ERR(p); 358 359 prog->prog = p; 360 361 return 0; 362 } 363 364 static const struct nla_policy bpf_nl_policy[LWT_BPF_MAX + 1] = { 365 [LWT_BPF_IN] = { .type = NLA_NESTED, }, 366 [LWT_BPF_OUT] = { .type = NLA_NESTED, }, 367 [LWT_BPF_XMIT] = { .type = NLA_NESTED, }, 368 [LWT_BPF_XMIT_HEADROOM] = { .type = NLA_U32 }, 369 }; 370 371 static int bpf_build_state(struct net *net, struct nlattr *nla, 372 unsigned int family, const void *cfg, 373 struct lwtunnel_state **ts, 374 struct netlink_ext_ack *extack) 375 { 376 struct nlattr *tb[LWT_BPF_MAX + 1]; 377 struct lwtunnel_state *newts; 378 struct bpf_lwt *bpf; 379 int ret; 380 381 if (family != AF_INET && family != AF_INET6) 382 return -EAFNOSUPPORT; 383 384 ret = nla_parse_nested_deprecated(tb, LWT_BPF_MAX, nla, bpf_nl_policy, 385 extack); 386 if (ret < 0) 387 return ret; 388 389 if (!tb[LWT_BPF_IN] && !tb[LWT_BPF_OUT] && !tb[LWT_BPF_XMIT]) 390 return -EINVAL; 391 392 newts = lwtunnel_state_alloc(sizeof(*bpf)); 393 if (!newts) 394 return -ENOMEM; 395 396 newts->type = LWTUNNEL_ENCAP_BPF; 397 bpf = bpf_lwt_lwtunnel(newts); 398 399 if (tb[LWT_BPF_IN]) { 400 newts->flags |= LWTUNNEL_STATE_INPUT_REDIRECT; 401 ret = bpf_parse_prog(tb[LWT_BPF_IN], &bpf->in, 402 BPF_PROG_TYPE_LWT_IN); 403 if (ret < 0) 404 goto errout; 405 } 406 407 if (tb[LWT_BPF_OUT]) { 408 newts->flags |= LWTUNNEL_STATE_OUTPUT_REDIRECT; 409 ret = bpf_parse_prog(tb[LWT_BPF_OUT], &bpf->out, 410 BPF_PROG_TYPE_LWT_OUT); 411 if (ret < 0) 412 goto errout; 413 } 414 415 if (tb[LWT_BPF_XMIT]) { 416 newts->flags |= LWTUNNEL_STATE_XMIT_REDIRECT; 417 ret = bpf_parse_prog(tb[LWT_BPF_XMIT], &bpf->xmit, 418 BPF_PROG_TYPE_LWT_XMIT); 419 if (ret < 0) 420 goto errout; 421 } 422 423 if (tb[LWT_BPF_XMIT_HEADROOM]) { 424 u32 headroom = nla_get_u32(tb[LWT_BPF_XMIT_HEADROOM]); 425 426 if (headroom > LWT_BPF_MAX_HEADROOM) { 427 ret = -ERANGE; 428 goto errout; 429 } 430 431 newts->headroom = headroom; 432 } 433 434 bpf->family = family; 435 *ts = newts; 436 437 return 0; 438 439 errout: 440 bpf_destroy_state(newts); 441 kfree(newts); 442 return ret; 443 } 444 445 static int bpf_fill_lwt_prog(struct sk_buff *skb, int attr, 446 struct bpf_lwt_prog *prog) 447 { 448 struct nlattr *nest; 449 450 if (!prog->prog) 451 return 0; 452 453 nest = nla_nest_start_noflag(skb, attr); 454 if (!nest) 455 return -EMSGSIZE; 456 457 if (prog->name && 458 nla_put_string(skb, LWT_BPF_PROG_NAME, prog->name)) 459 return -EMSGSIZE; 460 461 return nla_nest_end(skb, nest); 462 } 463 464 static int bpf_fill_encap_info(struct sk_buff *skb, struct lwtunnel_state *lwt) 465 { 466 struct bpf_lwt *bpf = bpf_lwt_lwtunnel(lwt); 467 468 if (bpf_fill_lwt_prog(skb, LWT_BPF_IN, &bpf->in) < 0 || 469 bpf_fill_lwt_prog(skb, LWT_BPF_OUT, &bpf->out) < 0 || 470 bpf_fill_lwt_prog(skb, LWT_BPF_XMIT, &bpf->xmit) < 0) 471 return -EMSGSIZE; 472 473 return 0; 474 } 475 476 static int bpf_encap_nlsize(struct lwtunnel_state *lwtstate) 477 { 478 int nest_len = nla_total_size(sizeof(struct nlattr)) + 479 nla_total_size(MAX_PROG_NAME) + /* LWT_BPF_PROG_NAME */ 480 0; 481 482 return nest_len + /* LWT_BPF_IN */ 483 nest_len + /* LWT_BPF_OUT */ 484 nest_len + /* LWT_BPF_XMIT */ 485 0; 486 } 487 488 static int bpf_lwt_prog_cmp(struct bpf_lwt_prog *a, struct bpf_lwt_prog *b) 489 { 490 /* FIXME: 491 * The LWT state is currently rebuilt for delete requests which 492 * results in a new bpf_prog instance. Comparing names for now. 493 */ 494 if (!a->name && !b->name) 495 return 0; 496 497 if (!a->name || !b->name) 498 return 1; 499 500 return strcmp(a->name, b->name); 501 } 502 503 static int bpf_encap_cmp(struct lwtunnel_state *a, struct lwtunnel_state *b) 504 { 505 struct bpf_lwt *a_bpf = bpf_lwt_lwtunnel(a); 506 struct bpf_lwt *b_bpf = bpf_lwt_lwtunnel(b); 507 508 return bpf_lwt_prog_cmp(&a_bpf->in, &b_bpf->in) || 509 bpf_lwt_prog_cmp(&a_bpf->out, &b_bpf->out) || 510 bpf_lwt_prog_cmp(&a_bpf->xmit, &b_bpf->xmit); 511 } 512 513 static const struct lwtunnel_encap_ops bpf_encap_ops = { 514 .build_state = bpf_build_state, 515 .destroy_state = bpf_destroy_state, 516 .input = bpf_input, 517 .output = bpf_output, 518 .xmit = bpf_xmit, 519 .fill_encap = bpf_fill_encap_info, 520 .get_encap_size = bpf_encap_nlsize, 521 .cmp_encap = bpf_encap_cmp, 522 .owner = THIS_MODULE, 523 }; 524 525 static int handle_gso_type(struct sk_buff *skb, unsigned int gso_type, 526 int encap_len) 527 { 528 struct skb_shared_info *shinfo = skb_shinfo(skb); 529 530 gso_type |= SKB_GSO_DODGY; 531 shinfo->gso_type |= gso_type; 532 skb_decrease_gso_size(shinfo, encap_len); 533 shinfo->gso_segs = 0; 534 return 0; 535 } 536 537 static int handle_gso_encap(struct sk_buff *skb, bool ipv4, int encap_len) 538 { 539 int next_hdr_offset; 540 void *next_hdr; 541 __u8 protocol; 542 543 /* SCTP and UDP_L4 gso need more nuanced handling than what 544 * handle_gso_type() does above: skb_decrease_gso_size() is not enough. 545 * So at the moment only TCP GSO packets are let through. 546 */ 547 if (!(skb_shinfo(skb)->gso_type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6))) 548 return -ENOTSUPP; 549 550 if (ipv4) { 551 protocol = ip_hdr(skb)->protocol; 552 next_hdr_offset = sizeof(struct iphdr); 553 next_hdr = skb_network_header(skb) + next_hdr_offset; 554 } else { 555 protocol = ipv6_hdr(skb)->nexthdr; 556 next_hdr_offset = sizeof(struct ipv6hdr); 557 next_hdr = skb_network_header(skb) + next_hdr_offset; 558 } 559 560 switch (protocol) { 561 case IPPROTO_GRE: 562 next_hdr_offset += sizeof(struct gre_base_hdr); 563 if (next_hdr_offset > encap_len) 564 return -EINVAL; 565 566 if (((struct gre_base_hdr *)next_hdr)->flags & GRE_CSUM) 567 return handle_gso_type(skb, SKB_GSO_GRE_CSUM, 568 encap_len); 569 return handle_gso_type(skb, SKB_GSO_GRE, encap_len); 570 571 case IPPROTO_UDP: 572 next_hdr_offset += sizeof(struct udphdr); 573 if (next_hdr_offset > encap_len) 574 return -EINVAL; 575 576 if (((struct udphdr *)next_hdr)->check) 577 return handle_gso_type(skb, SKB_GSO_UDP_TUNNEL_CSUM, 578 encap_len); 579 return handle_gso_type(skb, SKB_GSO_UDP_TUNNEL, encap_len); 580 581 case IPPROTO_IP: 582 case IPPROTO_IPV6: 583 if (ipv4) 584 return handle_gso_type(skb, SKB_GSO_IPXIP4, encap_len); 585 else 586 return handle_gso_type(skb, SKB_GSO_IPXIP6, encap_len); 587 588 default: 589 return -EPROTONOSUPPORT; 590 } 591 } 592 593 int bpf_lwt_push_ip_encap(struct sk_buff *skb, void *hdr, u32 len, bool ingress) 594 { 595 struct iphdr *iph; 596 bool ipv4; 597 int err; 598 599 if (unlikely(len < sizeof(struct iphdr) || len > LWT_BPF_MAX_HEADROOM)) 600 return -EINVAL; 601 602 /* validate protocol and length */ 603 iph = (struct iphdr *)hdr; 604 if (iph->version == 4) { 605 ipv4 = true; 606 if (unlikely(len < iph->ihl * 4)) 607 return -EINVAL; 608 } else if (iph->version == 6) { 609 ipv4 = false; 610 if (unlikely(len < sizeof(struct ipv6hdr))) 611 return -EINVAL; 612 } else { 613 return -EINVAL; 614 } 615 616 if (ingress) 617 err = skb_cow_head(skb, len + skb->mac_len); 618 else 619 err = skb_cow_head(skb, 620 len + LL_RESERVED_SPACE(skb_dst(skb)->dev)); 621 if (unlikely(err)) 622 return err; 623 624 /* push the encap headers and fix pointers */ 625 skb_reset_inner_headers(skb); 626 skb_reset_inner_mac_header(skb); /* mac header is not yet set */ 627 skb_set_inner_protocol(skb, skb->protocol); 628 skb->encapsulation = 1; 629 skb_push(skb, len); 630 if (ingress) 631 skb_postpush_rcsum(skb, iph, len); 632 skb_reset_network_header(skb); 633 memcpy(skb_network_header(skb), hdr, len); 634 bpf_compute_data_pointers(skb); 635 skb_clear_hash(skb); 636 637 if (ipv4) { 638 skb->protocol = htons(ETH_P_IP); 639 iph = ip_hdr(skb); 640 641 if (!iph->check) 642 iph->check = ip_fast_csum((unsigned char *)iph, 643 iph->ihl); 644 } else { 645 skb->protocol = htons(ETH_P_IPV6); 646 } 647 648 if (skb_is_gso(skb)) 649 return handle_gso_encap(skb, ipv4, len); 650 651 return 0; 652 } 653 654 static int __init bpf_lwt_init(void) 655 { 656 return lwtunnel_encap_add_ops(&bpf_encap_ops, LWTUNNEL_ENCAP_BPF); 657 } 658 659 subsys_initcall(bpf_lwt_init) 660