1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * SR-IPv6 implementation 4 * 5 * Author: 6 * David Lebrun <david.lebrun@uclouvain.be> 7 */ 8 9 #include <linux/types.h> 10 #include <linux/skbuff.h> 11 #include <linux/net.h> 12 #include <linux/module.h> 13 #include <net/ip.h> 14 #include <net/ip_tunnels.h> 15 #include <net/lwtunnel.h> 16 #include <net/netevent.h> 17 #include <net/netns/generic.h> 18 #include <net/ip6_fib.h> 19 #include <net/route.h> 20 #include <net/seg6.h> 21 #include <linux/seg6.h> 22 #include <linux/seg6_iptunnel.h> 23 #include <net/addrconf.h> 24 #include <net/ip6_route.h> 25 #include <net/dst_cache.h> 26 #ifdef CONFIG_IPV6_SEG6_HMAC 27 #include <net/seg6_hmac.h> 28 #endif 29 #include <linux/netfilter.h> 30 31 static size_t seg6_lwt_headroom(struct seg6_iptunnel_encap *tuninfo) 32 { 33 int head = 0; 34 35 switch (tuninfo->mode) { 36 case SEG6_IPTUN_MODE_INLINE: 37 break; 38 case SEG6_IPTUN_MODE_ENCAP: 39 head = sizeof(struct ipv6hdr); 40 break; 41 case SEG6_IPTUN_MODE_L2ENCAP: 42 return 0; 43 } 44 45 return ((tuninfo->srh->hdrlen + 1) << 3) + head; 46 } 47 48 struct seg6_lwt { 49 struct dst_cache cache; 50 struct seg6_iptunnel_encap tuninfo[]; 51 }; 52 53 static inline struct seg6_lwt *seg6_lwt_lwtunnel(struct lwtunnel_state *lwt) 54 { 55 return (struct seg6_lwt *)lwt->data; 56 } 57 58 static inline struct seg6_iptunnel_encap * 59 seg6_encap_lwtunnel(struct lwtunnel_state *lwt) 60 { 61 return seg6_lwt_lwtunnel(lwt)->tuninfo; 62 } 63 64 static const struct nla_policy seg6_iptunnel_policy[SEG6_IPTUNNEL_MAX + 1] = { 65 [SEG6_IPTUNNEL_SRH] = { .type = NLA_BINARY }, 66 }; 67 68 static int nla_put_srh(struct sk_buff *skb, int attrtype, 69 struct seg6_iptunnel_encap *tuninfo) 70 { 71 struct seg6_iptunnel_encap *data; 72 struct nlattr *nla; 73 int len; 74 75 len = SEG6_IPTUN_ENCAP_SIZE(tuninfo); 76 77 nla = nla_reserve(skb, attrtype, len); 78 if (!nla) 79 return -EMSGSIZE; 80 81 data = nla_data(nla); 82 memcpy(data, tuninfo, len); 83 84 return 0; 85 } 86 87 static void set_tun_src(struct net *net, struct net_device *dev, 88 struct in6_addr *daddr, struct in6_addr *saddr) 89 { 90 struct seg6_pernet_data *sdata = seg6_pernet(net); 91 struct in6_addr *tun_src; 92 93 rcu_read_lock(); 94 95 tun_src = rcu_dereference(sdata->tun_src); 96 97 if (!ipv6_addr_any(tun_src)) { 98 memcpy(saddr, tun_src, sizeof(struct in6_addr)); 99 } else { 100 ipv6_dev_get_saddr(net, dev, daddr, IPV6_PREFER_SRC_PUBLIC, 101 saddr); 102 } 103 104 rcu_read_unlock(); 105 } 106 107 /* Compute flowlabel for outer IPv6 header */ 108 static __be32 seg6_make_flowlabel(struct net *net, struct sk_buff *skb, 109 struct ipv6hdr *inner_hdr) 110 { 111 int do_flowlabel = net->ipv6.sysctl.seg6_flowlabel; 112 __be32 flowlabel = 0; 113 u32 hash; 114 115 if (do_flowlabel > 0) { 116 hash = skb_get_hash(skb); 117 hash = rol32(hash, 16); 118 flowlabel = (__force __be32)hash & IPV6_FLOWLABEL_MASK; 119 } else if (!do_flowlabel && skb->protocol == htons(ETH_P_IPV6)) { 120 flowlabel = ip6_flowlabel(inner_hdr); 121 } 122 return flowlabel; 123 } 124 125 /* encapsulate an IPv6 packet within an outer IPv6 header with a given SRH */ 126 int seg6_do_srh_encap(struct sk_buff *skb, struct ipv6_sr_hdr *osrh, int proto) 127 { 128 struct dst_entry *dst = skb_dst(skb); 129 struct net *net = dev_net(dst->dev); 130 struct ipv6hdr *hdr, *inner_hdr; 131 struct ipv6_sr_hdr *isrh; 132 int hdrlen, tot_len, err; 133 __be32 flowlabel; 134 135 hdrlen = (osrh->hdrlen + 1) << 3; 136 tot_len = hdrlen + sizeof(*hdr); 137 138 err = skb_cow_head(skb, tot_len + skb->mac_len); 139 if (unlikely(err)) 140 return err; 141 142 inner_hdr = ipv6_hdr(skb); 143 flowlabel = seg6_make_flowlabel(net, skb, inner_hdr); 144 145 skb_push(skb, tot_len); 146 skb_reset_network_header(skb); 147 skb_mac_header_rebuild(skb); 148 hdr = ipv6_hdr(skb); 149 150 /* inherit tc, flowlabel and hlim 151 * hlim will be decremented in ip6_forward() afterwards and 152 * decapsulation will overwrite inner hlim with outer hlim 153 */ 154 155 if (skb->protocol == htons(ETH_P_IPV6)) { 156 ip6_flow_hdr(hdr, ip6_tclass(ip6_flowinfo(inner_hdr)), 157 flowlabel); 158 hdr->hop_limit = inner_hdr->hop_limit; 159 } else { 160 ip6_flow_hdr(hdr, 0, flowlabel); 161 hdr->hop_limit = ip6_dst_hoplimit(skb_dst(skb)); 162 163 memset(IP6CB(skb), 0, sizeof(*IP6CB(skb))); 164 } 165 166 hdr->nexthdr = NEXTHDR_ROUTING; 167 168 isrh = (void *)hdr + sizeof(*hdr); 169 memcpy(isrh, osrh, hdrlen); 170 171 isrh->nexthdr = proto; 172 173 hdr->daddr = isrh->segments[isrh->first_segment]; 174 set_tun_src(net, dst->dev, &hdr->daddr, &hdr->saddr); 175 176 #ifdef CONFIG_IPV6_SEG6_HMAC 177 if (sr_has_hmac(isrh)) { 178 err = seg6_push_hmac(net, &hdr->saddr, isrh); 179 if (unlikely(err)) 180 return err; 181 } 182 #endif 183 184 skb_postpush_rcsum(skb, hdr, tot_len); 185 186 return 0; 187 } 188 EXPORT_SYMBOL_GPL(seg6_do_srh_encap); 189 190 /* insert an SRH within an IPv6 packet, just after the IPv6 header */ 191 int seg6_do_srh_inline(struct sk_buff *skb, struct ipv6_sr_hdr *osrh) 192 { 193 struct ipv6hdr *hdr, *oldhdr; 194 struct ipv6_sr_hdr *isrh; 195 int hdrlen, err; 196 197 hdrlen = (osrh->hdrlen + 1) << 3; 198 199 err = skb_cow_head(skb, hdrlen + skb->mac_len); 200 if (unlikely(err)) 201 return err; 202 203 oldhdr = ipv6_hdr(skb); 204 205 skb_pull(skb, sizeof(struct ipv6hdr)); 206 skb_postpull_rcsum(skb, skb_network_header(skb), 207 sizeof(struct ipv6hdr)); 208 209 skb_push(skb, sizeof(struct ipv6hdr) + hdrlen); 210 skb_reset_network_header(skb); 211 skb_mac_header_rebuild(skb); 212 213 hdr = ipv6_hdr(skb); 214 215 memmove(hdr, oldhdr, sizeof(*hdr)); 216 217 isrh = (void *)hdr + sizeof(*hdr); 218 memcpy(isrh, osrh, hdrlen); 219 220 isrh->nexthdr = hdr->nexthdr; 221 hdr->nexthdr = NEXTHDR_ROUTING; 222 223 isrh->segments[0] = hdr->daddr; 224 hdr->daddr = isrh->segments[isrh->first_segment]; 225 226 #ifdef CONFIG_IPV6_SEG6_HMAC 227 if (sr_has_hmac(isrh)) { 228 struct net *net = dev_net(skb_dst(skb)->dev); 229 230 err = seg6_push_hmac(net, &hdr->saddr, isrh); 231 if (unlikely(err)) 232 return err; 233 } 234 #endif 235 236 skb_postpush_rcsum(skb, hdr, sizeof(struct ipv6hdr) + hdrlen); 237 238 return 0; 239 } 240 EXPORT_SYMBOL_GPL(seg6_do_srh_inline); 241 242 static int seg6_do_srh(struct sk_buff *skb) 243 { 244 struct dst_entry *dst = skb_dst(skb); 245 struct seg6_iptunnel_encap *tinfo; 246 int proto, err = 0; 247 248 tinfo = seg6_encap_lwtunnel(dst->lwtstate); 249 250 switch (tinfo->mode) { 251 case SEG6_IPTUN_MODE_INLINE: 252 if (skb->protocol != htons(ETH_P_IPV6)) 253 return -EINVAL; 254 255 err = seg6_do_srh_inline(skb, tinfo->srh); 256 if (err) 257 return err; 258 break; 259 case SEG6_IPTUN_MODE_ENCAP: 260 err = iptunnel_handle_offloads(skb, SKB_GSO_IPXIP6); 261 if (err) 262 return err; 263 264 if (skb->protocol == htons(ETH_P_IPV6)) 265 proto = IPPROTO_IPV6; 266 else if (skb->protocol == htons(ETH_P_IP)) 267 proto = IPPROTO_IPIP; 268 else 269 return -EINVAL; 270 271 err = seg6_do_srh_encap(skb, tinfo->srh, proto); 272 if (err) 273 return err; 274 275 skb_set_inner_transport_header(skb, skb_transport_offset(skb)); 276 skb_set_inner_protocol(skb, skb->protocol); 277 skb->protocol = htons(ETH_P_IPV6); 278 break; 279 case SEG6_IPTUN_MODE_L2ENCAP: 280 if (!skb_mac_header_was_set(skb)) 281 return -EINVAL; 282 283 if (pskb_expand_head(skb, skb->mac_len, 0, GFP_ATOMIC) < 0) 284 return -ENOMEM; 285 286 skb_mac_header_rebuild(skb); 287 skb_push(skb, skb->mac_len); 288 289 err = seg6_do_srh_encap(skb, tinfo->srh, IPPROTO_ETHERNET); 290 if (err) 291 return err; 292 293 skb->protocol = htons(ETH_P_IPV6); 294 break; 295 } 296 297 ipv6_hdr(skb)->payload_len = htons(skb->len - sizeof(struct ipv6hdr)); 298 skb_set_transport_header(skb, sizeof(struct ipv6hdr)); 299 nf_reset_ct(skb); 300 301 return 0; 302 } 303 304 static int seg6_input_finish(struct net *net, struct sock *sk, 305 struct sk_buff *skb) 306 { 307 return dst_input(skb); 308 } 309 310 static int seg6_input_core(struct net *net, struct sock *sk, 311 struct sk_buff *skb) 312 { 313 struct dst_entry *orig_dst = skb_dst(skb); 314 struct dst_entry *dst = NULL; 315 struct seg6_lwt *slwt; 316 int err; 317 318 err = seg6_do_srh(skb); 319 if (unlikely(err)) { 320 kfree_skb(skb); 321 return err; 322 } 323 324 slwt = seg6_lwt_lwtunnel(orig_dst->lwtstate); 325 326 preempt_disable(); 327 dst = dst_cache_get(&slwt->cache); 328 preempt_enable(); 329 330 skb_dst_drop(skb); 331 332 if (!dst) { 333 ip6_route_input(skb); 334 dst = skb_dst(skb); 335 if (!dst->error) { 336 preempt_disable(); 337 dst_cache_set_ip6(&slwt->cache, dst, 338 &ipv6_hdr(skb)->saddr); 339 preempt_enable(); 340 } 341 } else { 342 skb_dst_set(skb, dst); 343 } 344 345 err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev)); 346 if (unlikely(err)) 347 return err; 348 349 if (static_branch_unlikely(&nf_hooks_lwtunnel_enabled)) 350 return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_OUT, 351 dev_net(skb->dev), NULL, skb, NULL, 352 skb_dst(skb)->dev, seg6_input_finish); 353 354 return seg6_input_finish(dev_net(skb->dev), NULL, skb); 355 } 356 357 static int seg6_input_nf(struct sk_buff *skb) 358 { 359 struct net_device *dev = skb_dst(skb)->dev; 360 struct net *net = dev_net(skb->dev); 361 362 switch (skb->protocol) { 363 case htons(ETH_P_IP): 364 return NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING, net, NULL, 365 skb, NULL, dev, seg6_input_core); 366 case htons(ETH_P_IPV6): 367 return NF_HOOK(NFPROTO_IPV6, NF_INET_POST_ROUTING, net, NULL, 368 skb, NULL, dev, seg6_input_core); 369 } 370 371 return -EINVAL; 372 } 373 374 static int seg6_input(struct sk_buff *skb) 375 { 376 if (static_branch_unlikely(&nf_hooks_lwtunnel_enabled)) 377 return seg6_input_nf(skb); 378 379 return seg6_input_core(dev_net(skb->dev), NULL, skb); 380 } 381 382 static int seg6_output_core(struct net *net, struct sock *sk, 383 struct sk_buff *skb) 384 { 385 struct dst_entry *orig_dst = skb_dst(skb); 386 struct dst_entry *dst = NULL; 387 struct seg6_lwt *slwt; 388 int err; 389 390 err = seg6_do_srh(skb); 391 if (unlikely(err)) 392 goto drop; 393 394 slwt = seg6_lwt_lwtunnel(orig_dst->lwtstate); 395 396 preempt_disable(); 397 dst = dst_cache_get(&slwt->cache); 398 preempt_enable(); 399 400 if (unlikely(!dst)) { 401 struct ipv6hdr *hdr = ipv6_hdr(skb); 402 struct flowi6 fl6; 403 404 memset(&fl6, 0, sizeof(fl6)); 405 fl6.daddr = hdr->daddr; 406 fl6.saddr = hdr->saddr; 407 fl6.flowlabel = ip6_flowinfo(hdr); 408 fl6.flowi6_mark = skb->mark; 409 fl6.flowi6_proto = hdr->nexthdr; 410 411 dst = ip6_route_output(net, NULL, &fl6); 412 if (dst->error) { 413 err = dst->error; 414 dst_release(dst); 415 goto drop; 416 } 417 418 preempt_disable(); 419 dst_cache_set_ip6(&slwt->cache, dst, &fl6.saddr); 420 preempt_enable(); 421 } 422 423 skb_dst_drop(skb); 424 skb_dst_set(skb, dst); 425 426 err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev)); 427 if (unlikely(err)) 428 goto drop; 429 430 if (static_branch_unlikely(&nf_hooks_lwtunnel_enabled)) 431 return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_OUT, net, sk, skb, 432 NULL, skb_dst(skb)->dev, dst_output); 433 434 return dst_output(net, sk, skb); 435 drop: 436 kfree_skb(skb); 437 return err; 438 } 439 440 static int seg6_output_nf(struct net *net, struct sock *sk, struct sk_buff *skb) 441 { 442 struct net_device *dev = skb_dst(skb)->dev; 443 444 switch (skb->protocol) { 445 case htons(ETH_P_IP): 446 return NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING, net, sk, skb, 447 NULL, dev, seg6_output_core); 448 case htons(ETH_P_IPV6): 449 return NF_HOOK(NFPROTO_IPV6, NF_INET_POST_ROUTING, net, sk, skb, 450 NULL, dev, seg6_output_core); 451 } 452 453 return -EINVAL; 454 } 455 456 static int seg6_output(struct net *net, struct sock *sk, struct sk_buff *skb) 457 { 458 if (static_branch_unlikely(&nf_hooks_lwtunnel_enabled)) 459 return seg6_output_nf(net, sk, skb); 460 461 return seg6_output_core(net, sk, skb); 462 } 463 464 static int seg6_build_state(struct net *net, struct nlattr *nla, 465 unsigned int family, const void *cfg, 466 struct lwtunnel_state **ts, 467 struct netlink_ext_ack *extack) 468 { 469 struct nlattr *tb[SEG6_IPTUNNEL_MAX + 1]; 470 struct seg6_iptunnel_encap *tuninfo; 471 struct lwtunnel_state *newts; 472 int tuninfo_len, min_size; 473 struct seg6_lwt *slwt; 474 int err; 475 476 if (family != AF_INET && family != AF_INET6) 477 return -EINVAL; 478 479 err = nla_parse_nested_deprecated(tb, SEG6_IPTUNNEL_MAX, nla, 480 seg6_iptunnel_policy, extack); 481 482 if (err < 0) 483 return err; 484 485 if (!tb[SEG6_IPTUNNEL_SRH]) 486 return -EINVAL; 487 488 tuninfo = nla_data(tb[SEG6_IPTUNNEL_SRH]); 489 tuninfo_len = nla_len(tb[SEG6_IPTUNNEL_SRH]); 490 491 /* tuninfo must contain at least the iptunnel encap structure, 492 * the SRH and one segment 493 */ 494 min_size = sizeof(*tuninfo) + sizeof(struct ipv6_sr_hdr) + 495 sizeof(struct in6_addr); 496 if (tuninfo_len < min_size) 497 return -EINVAL; 498 499 switch (tuninfo->mode) { 500 case SEG6_IPTUN_MODE_INLINE: 501 if (family != AF_INET6) 502 return -EINVAL; 503 504 break; 505 case SEG6_IPTUN_MODE_ENCAP: 506 break; 507 case SEG6_IPTUN_MODE_L2ENCAP: 508 break; 509 default: 510 return -EINVAL; 511 } 512 513 /* verify that SRH is consistent */ 514 if (!seg6_validate_srh(tuninfo->srh, tuninfo_len - sizeof(*tuninfo), false)) 515 return -EINVAL; 516 517 newts = lwtunnel_state_alloc(tuninfo_len + sizeof(*slwt)); 518 if (!newts) 519 return -ENOMEM; 520 521 slwt = seg6_lwt_lwtunnel(newts); 522 523 err = dst_cache_init(&slwt->cache, GFP_ATOMIC); 524 if (err) { 525 kfree(newts); 526 return err; 527 } 528 529 memcpy(&slwt->tuninfo, tuninfo, tuninfo_len); 530 531 newts->type = LWTUNNEL_ENCAP_SEG6; 532 newts->flags |= LWTUNNEL_STATE_INPUT_REDIRECT; 533 534 if (tuninfo->mode != SEG6_IPTUN_MODE_L2ENCAP) 535 newts->flags |= LWTUNNEL_STATE_OUTPUT_REDIRECT; 536 537 newts->headroom = seg6_lwt_headroom(tuninfo); 538 539 *ts = newts; 540 541 return 0; 542 } 543 544 static void seg6_destroy_state(struct lwtunnel_state *lwt) 545 { 546 dst_cache_destroy(&seg6_lwt_lwtunnel(lwt)->cache); 547 } 548 549 static int seg6_fill_encap_info(struct sk_buff *skb, 550 struct lwtunnel_state *lwtstate) 551 { 552 struct seg6_iptunnel_encap *tuninfo = seg6_encap_lwtunnel(lwtstate); 553 554 if (nla_put_srh(skb, SEG6_IPTUNNEL_SRH, tuninfo)) 555 return -EMSGSIZE; 556 557 return 0; 558 } 559 560 static int seg6_encap_nlsize(struct lwtunnel_state *lwtstate) 561 { 562 struct seg6_iptunnel_encap *tuninfo = seg6_encap_lwtunnel(lwtstate); 563 564 return nla_total_size(SEG6_IPTUN_ENCAP_SIZE(tuninfo)); 565 } 566 567 static int seg6_encap_cmp(struct lwtunnel_state *a, struct lwtunnel_state *b) 568 { 569 struct seg6_iptunnel_encap *a_hdr = seg6_encap_lwtunnel(a); 570 struct seg6_iptunnel_encap *b_hdr = seg6_encap_lwtunnel(b); 571 int len = SEG6_IPTUN_ENCAP_SIZE(a_hdr); 572 573 if (len != SEG6_IPTUN_ENCAP_SIZE(b_hdr)) 574 return 1; 575 576 return memcmp(a_hdr, b_hdr, len); 577 } 578 579 static const struct lwtunnel_encap_ops seg6_iptun_ops = { 580 .build_state = seg6_build_state, 581 .destroy_state = seg6_destroy_state, 582 .output = seg6_output, 583 .input = seg6_input, 584 .fill_encap = seg6_fill_encap_info, 585 .get_encap_size = seg6_encap_nlsize, 586 .cmp_encap = seg6_encap_cmp, 587 .owner = THIS_MODULE, 588 }; 589 590 int __init seg6_iptunnel_init(void) 591 { 592 return lwtunnel_encap_add_ops(&seg6_iptun_ops, LWTUNNEL_ENCAP_SEG6); 593 } 594 595 void seg6_iptunnel_exit(void) 596 { 597 lwtunnel_encap_del_ops(&seg6_iptun_ops, LWTUNNEL_ENCAP_SEG6); 598 } 599