net/ndisc.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * Copyright (C) 2013 Allied Telesis Labs NZ
   4  * Chris Packham, <judge.packham@gmail.com>
   5  *
   6  * Copyright (C) 2022 YADRO
   7  * Viacheslav Mitrofanov <v.v.mitrofanov@yadro.com>
   8  */
   9
  10 /* Neighbour Discovery for IPv6 */
  11
  12 #include <net.h>
  13 #include <net6.h>
  14 #include <ndisc.h>
  15 #include <stdlib.h>
  16 #include <linux/delay.h>
  17
  18 /* IPv6 destination address of packet waiting for ND */
  19 struct in6_addr net_nd_sol_packet_ip6 = ZERO_IPV6_ADDR;
  20 /* IPv6 address we are expecting ND advert from */
  21 static struct in6_addr net_nd_rep_packet_ip6 = ZERO_IPV6_ADDR;
  22 /* MAC destination address of packet waiting for ND */
  23 uchar *net_nd_packet_mac;
  24 /* pointer to packet waiting to be transmitted after ND is resolved */
  25 uchar *net_nd_tx_packet;
  26 static uchar net_nd_packet_buf[PKTSIZE_ALIGN + PKTALIGN];
  27 /* size of packet waiting to be transmitted */
  28 int net_nd_tx_packet_size;
  29 /* the timer for ND resolution */
  30 ulong net_nd_timer_start;
  31 /* the number of requests we have sent so far */
  32 int net_nd_try;
  33 struct in6_addr all_routers = ALL_ROUTERS_MULT_ADDR;
  34
  35 #define MAX_RTR_SOLICITATIONS           3
  36 /* The maximum time to delay sending the first router solicitation message. */
  37 #define MAX_SOLICITATION_DELAY          1 // 1 second
  38 /* The time to wait before sending the next router solicitation message. */
  39 #define RTR_SOLICITATION_INTERVAL       4000 // 4 seconds
  40
  41 #define IP6_NDISC_OPT_SPACE(len) (((len) + 2 + 7) & ~7)
  42
  43 /**
  44  * ndisc_insert_option() - Insert an option into a neighbor discovery packet
  45  *
  46  * @opt:        pointer to the option element of the neighbor discovery packet
  47  * @type:       option type to insert
  48  * @data:       option data to insert
  49  * @len:        data length
  50  * Return: the number of bytes inserted (which may be >= len)
  51  */
  52 static int ndisc_insert_option(__u8 *opt, int type, u8 *data, int len)
  53 {
  54         int space = IP6_NDISC_OPT_SPACE(len);
  55
  56         opt[0] = type;
  57         opt[1] = space >> 3;
  58         memcpy(&opt[2], data, len);
  59         len += 2;
  60
  61         /* fill the remainder with 0 */
  62         if (space - len > 0)
  63                 memset(&opt[len], '\0', space - len);
  64
  65         return space;
  66 }
  67
  68 /**
  69  * ndisc_extract_enetaddr() - Extract the Ethernet address from a ND packet
  70  *
  71  * Note that the link layer address could be anything but the only networking
  72  * media that u-boot supports is Ethernet so we assume we're extracting a 6
  73  * byte Ethernet MAC address.
  74  *
  75  * @ndisc:      pointer to ND packet
  76  * @enetaddr:   extracted MAC addr
  77  */
  78 static void ndisc_extract_enetaddr(struct nd_msg *ndisc, uchar enetaddr[6])
  79 {
  80         memcpy(enetaddr, &ndisc->opt[2], 6);
  81 }
  82
  83 /**
  84  * ndisc_has_option() - Check if the ND packet has the specified option set
  85  *
  86  * @ip6:        pointer to IPv6 header
  87  * @type:       option type to check
  88  * Return: 1 if ND has that option, 0 therwise
  89  */
  90 static int ndisc_has_option(struct ip6_hdr *ip6, __u8 type)
  91 {
  92         struct nd_msg *ndisc = (struct nd_msg *)(((uchar *)ip6) + IP6_HDR_SIZE);
  93
  94         if (ip6->payload_len <= sizeof(struct icmp6hdr))
  95                 return 0;
  96
  97         return ndisc->opt[0] == type;
  98 }
  99
 100 static void ip6_send_ns(struct in6_addr *neigh_addr)
 101 {
 102         struct in6_addr dst_adr;
 103         unsigned char enetaddr[6];
 104         struct nd_msg *msg;
 105         __u16 len;
 106         uchar *pkt;
 107         unsigned short csum;
 108         unsigned int pcsum;
 109
 110         debug("sending neighbor solicitation for %pI6c our address %pI6c\n",
 111               neigh_addr, &net_link_local_ip6);
 112
 113         /* calculate src, dest IPv6 addr and dest Eth addr */
 114         ip6_make_snma(&dst_adr, neigh_addr);
 115         ip6_make_mult_ethdstaddr(enetaddr, &dst_adr);
 116         len = sizeof(struct icmp6hdr) + IN6ADDRSZ +
 117             IP6_NDISC_OPT_SPACE(INETHADDRSZ);
 118
 119         pkt = (uchar *)net_tx_packet;
 120         pkt += net_set_ether(pkt, enetaddr, PROT_IP6);
 121         pkt += ip6_add_hdr(pkt, &net_link_local_ip6, &dst_adr, PROT_ICMPV6,
 122                            IPV6_NDISC_HOPLIMIT, len);
 123
 124         /* ICMPv6 - NS */
 125         msg = (struct nd_msg *)pkt;
 126         msg->icmph.icmp6_type = IPV6_NDISC_NEIGHBOUR_SOLICITATION;
 127         msg->icmph.icmp6_code = 0;
 128         memset(&msg->icmph.icmp6_cksum, 0, sizeof(__be16));
 129         memset(&msg->icmph.icmp6_unused, 0, sizeof(__be32));
 130
 131         /* Set the target address and llsaddr option */
 132         net_copy_ip6(&msg->target, neigh_addr);
 133         ndisc_insert_option(msg->opt, ND_OPT_SOURCE_LL_ADDR, net_ethaddr,
 134                             INETHADDRSZ);
 135
 136         /* checksum */
 137         pcsum = csum_partial((__u8 *)msg, len, 0);
 138         csum = csum_ipv6_magic(&net_link_local_ip6, &dst_adr,
 139                                len, PROT_ICMPV6, pcsum);
 140         msg->icmph.icmp6_cksum = csum;
 141         pkt += len;
 142
 143         /* send it! */
 144         net_send_packet(net_tx_packet, (pkt - net_tx_packet));
 145 }
 146
 147 /*
 148  * ip6_send_rs() - Send IPv6 Router Solicitation Message.
 149  *
 150  * A router solicitation is sent to discover a router. RS message creation is
 151  * based on RFC 4861 section 4.1. Router Solicitation Message Format.
 152  */
 153 void ip6_send_rs(void)
 154 {
 155         unsigned char enetaddr[6];
 156         struct rs_msg *msg;
 157         __u16 icmp_len;
 158         uchar *pkt;
 159         unsigned short csum;
 160         unsigned int pcsum;
 161         static unsigned int retry_count;
 162
 163         if (!ip6_is_unspecified_addr(&net_gateway6) &&
 164             net_prefix_length != 0) {
 165                 net_set_state(NETLOOP_SUCCESS);
 166                 return;
 167         } else if (retry_count >= MAX_RTR_SOLICITATIONS) {
 168                 net_set_state(NETLOOP_FAIL);
 169                 net_set_timeout_handler(0, NULL);
 170                 retry_count = 0;
 171                 return;
 172         }
 173
 174         printf("ROUTER SOLICITATION %d\n", retry_count + 1);
 175
 176         ip6_make_mult_ethdstaddr(enetaddr, &all_routers);
 177         /*
 178          * ICMP length is the size of ICMP header (8) + one option (8) = 16.
 179          * The option is 2 bytes of type and length + 6 bytes for MAC.
 180          */
 181         icmp_len = sizeof(struct icmp6hdr) + IP6_NDISC_OPT_SPACE(INETHADDRSZ);
 182
 183         pkt = (uchar *)net_tx_packet;
 184         pkt += net_set_ether(pkt, enetaddr, PROT_IP6);
 185         pkt += ip6_add_hdr(pkt, &net_link_local_ip6, &all_routers, PROT_ICMPV6,
 186                            IPV6_NDISC_HOPLIMIT, icmp_len);
 187
 188         /* ICMPv6 - RS */
 189         msg = (struct rs_msg *)pkt;
 190         msg->icmph.icmp6_type = IPV6_NDISC_ROUTER_SOLICITATION;
 191         msg->icmph.icmp6_code = 0;
 192         memset(&msg->icmph.icmp6_cksum, 0, sizeof(__be16));
 193         memset(&msg->icmph.icmp6_unused, 0, sizeof(__be32));
 194
 195         /* Set the llsaddr option */
 196         ndisc_insert_option(msg->opt, ND_OPT_SOURCE_LL_ADDR, net_ethaddr,
 197                             INETHADDRSZ);
 198
 199         /* checksum */
 200         pcsum = csum_partial((__u8 *)msg, icmp_len, 0);
 201         csum = csum_ipv6_magic(&net_link_local_ip6, &all_routers,
 202                                icmp_len, PROT_ICMPV6, pcsum);
 203         msg->icmph.icmp6_cksum = csum;
 204         pkt += icmp_len;
 205
 206         /* Wait up to 1 second if it is the first try to get the RA */
 207         if (retry_count == 0)
 208                 udelay(((unsigned int)rand() % 1000000) * MAX_SOLICITATION_DELAY);
 209
 210         /* send it! */
 211         net_send_packet(net_tx_packet, (pkt - net_tx_packet));
 212
 213         retry_count++;
 214         net_set_timeout_handler(RTR_SOLICITATION_INTERVAL, ip6_send_rs);
 215 }
 216
 217 static void
 218 ip6_send_na(uchar *eth_dst_addr, struct in6_addr *neigh_addr,
 219             struct in6_addr *target)
 220 {
 221         struct nd_msg *msg;
 222         __u16 len;
 223         uchar *pkt;
 224         unsigned short csum;
 225
 226         debug("sending neighbor advertisement for %pI6c to %pI6c (%pM)\n",
 227               target, neigh_addr, eth_dst_addr);
 228
 229         len = sizeof(struct icmp6hdr) + IN6ADDRSZ +
 230             IP6_NDISC_OPT_SPACE(INETHADDRSZ);
 231
 232         pkt = (uchar *)net_tx_packet;
 233         pkt += net_set_ether(pkt, eth_dst_addr, PROT_IP6);
 234         pkt += ip6_add_hdr(pkt, &net_link_local_ip6, neigh_addr,
 235                            PROT_ICMPV6, IPV6_NDISC_HOPLIMIT, len);
 236
 237         /* ICMPv6 - NA */
 238         msg = (struct nd_msg *)pkt;
 239         msg->icmph.icmp6_type = IPV6_NDISC_NEIGHBOUR_ADVERTISEMENT;
 240         msg->icmph.icmp6_code = 0;
 241         memset(&msg->icmph.icmp6_cksum, 0, sizeof(__be16));
 242         memset(&msg->icmph.icmp6_unused, 0, sizeof(__be32));
 243         msg->icmph.icmp6_dataun.u_nd_advt.solicited = 1;
 244         msg->icmph.icmp6_dataun.u_nd_advt.override = 1;
 245         /* Set the target address and lltargetaddr option */
 246         net_copy_ip6(&msg->target, target);
 247         ndisc_insert_option(msg->opt, ND_OPT_TARGET_LL_ADDR, net_ethaddr,
 248                             INETHADDRSZ);
 249
 250         /* checksum */
 251         csum = csum_ipv6_magic(&net_link_local_ip6,
 252                                neigh_addr, len, PROT_ICMPV6,
 253                                csum_partial((__u8 *)msg, len, 0));
 254         msg->icmph.icmp6_cksum = csum;
 255         pkt += len;
 256
 257         /* send it! */
 258         net_send_packet(net_tx_packet, (pkt - net_tx_packet));
 259 }
 260
 261 void ndisc_request(void)
 262 {
 263         if (!ip6_addr_in_subnet(&net_ip6, &net_nd_sol_packet_ip6,
 264                                 net_prefix_length)) {
 265                 if (ip6_is_unspecified_addr(&net_gateway6)) {
 266                         puts("## Warning: gatewayip6 is needed but not set\n");
 267                         net_nd_rep_packet_ip6 = net_nd_sol_packet_ip6;
 268                 } else {
 269                         net_nd_rep_packet_ip6 = net_gateway6;
 270                 }
 271         } else {
 272                 net_nd_rep_packet_ip6 = net_nd_sol_packet_ip6;
 273         }
 274
 275         ip6_send_ns(&net_nd_rep_packet_ip6);
 276 }
 277
 278 int ndisc_timeout_check(void)
 279 {
 280         ulong t;
 281
 282         if (ip6_is_unspecified_addr(&net_nd_sol_packet_ip6))
 283                 return 0;
 284
 285         t = get_timer(0);
 286
 287         /* check for NDISC timeout */
 288         if ((t - net_nd_timer_start) > NDISC_TIMEOUT) {
 289                 net_nd_try++;
 290                 if (net_nd_try >= NDISC_TIMEOUT_COUNT) {
 291                         puts("\nNeighbour discovery retry count exceeded; "
 292                              "starting again\n");
 293                         net_nd_try = 0;
 294                         net_set_state(NETLOOP_FAIL);
 295                 } else {
 296                         net_nd_timer_start = t;
 297                         ndisc_request();
 298                 }
 299         }
 300         return 1;
 301 }
 302
 303 /*
 304  * ndisc_init() - Make initial steps for ND state machine.
 305  * Usually move variables into initial state.
 306  */
 307 void ndisc_init(void)
 308 {
 309         net_nd_packet_mac = NULL;
 310         net_nd_tx_packet = NULL;
 311         net_nd_sol_packet_ip6 = net_null_addr_ip6;
 312         net_nd_rep_packet_ip6 = net_null_addr_ip6;
 313         net_nd_tx_packet_size = 0;
 314         net_nd_tx_packet = &net_nd_packet_buf[0] + (PKTALIGN - 1);
 315         net_nd_tx_packet -= (ulong)net_nd_tx_packet % PKTALIGN;
 316 }
 317
 318 /*
 319  * validate_ra() - Validate the router advertisement message.
 320  *
 321  * @ip6: Pointer to the router advertisement packet
 322  *
 323  * Check if the router advertisement message is valid. Conditions are
 324  * according to RFC 4861 section 6.1.2. Validation of Router Advertisement
 325  * Messages.
 326  *
 327  * Return: true if the message is valid and false if it is invalid.
 328  */
 329 bool validate_ra(struct ip6_hdr *ip6)
 330 {
 331         struct icmp6hdr *icmp = (struct icmp6hdr *)(ip6 + 1);
 332
 333         /* ICMP length (derived from the IP length) should be 16 or more octets. */
 334         if (ip6->payload_len < 16)
 335                 return false;
 336
 337         /* Source IP Address should be a valid link-local address. */
 338         if ((ntohs(ip6->saddr.s6_addr16[0]) & IPV6_LINK_LOCAL_MASK) !=
 339             IPV6_LINK_LOCAL_PREFIX)
 340                 return false;
 341
 342         /*
 343          * The IP Hop Limit field should have a value of 255, i.e., the packet
 344          * could not possibly have been forwarded by a router.
 345          */
 346         if (ip6->hop_limit != 255)
 347                 return false;
 348
 349         /* ICMP checksum has already been checked in net_ip6_handler. */
 350
 351         if (icmp->icmp6_code != 0)
 352                 return false;
 353
 354         return true;
 355 }
 356
 357 /*
 358  * process_ra() - Process the router advertisement packet.
 359  *
 360  * @ip6: Pointer to the router advertisement packet
 361  * @len: Length of the router advertisement packet
 362  *
 363  * Process the received router advertisement message.
 364  * Although RFC 4861 requires retaining at least two router addresses, we only
 365  * keep one because of the U-Boot limitations and its goal of lightweight code.
 366  *
 367  * Return: 0 - RA is a default router and contains valid prefix information.
 368  * Non-zero - RA options are invalid or do not indicate it is a default router
 369  * or do not contain valid prefix information.
 370  */
 371 int process_ra(struct ip6_hdr *ip6, int len)
 372 {
 373         /* Pointer to the ICMP section of the packet */
 374         struct icmp6hdr *icmp = (struct icmp6hdr *)(ip6 + 1);
 375         struct ra_msg *msg = (struct ra_msg *)icmp;
 376         int remaining_option_len = len - IP6_HDR_SIZE - sizeof(struct ra_msg);
 377         unsigned short int option_len;  /* Length of each option */
 378         /* Pointer to the ICMPv6 message options */
 379         unsigned char *option = NULL;
 380         /* 8-bit identifier of the type of ICMPv6 option */
 381         unsigned char type = 0;
 382         struct icmp6_ra_prefix_info *prefix = NULL;
 383
 384         if (len > ETH_MAX_MTU)
 385                 return -EMSGSIZE;
 386         /* Ignore the packet if router lifetime is 0. */
 387         if (!icmp->icmp6_rt_lifetime)
 388                 return -EOPNOTSUPP;
 389
 390         /* Processing the options */
 391         option = msg->opt;
 392         while (remaining_option_len > 0) {
 393                 /* The 2nd byte of the option is its length. */
 394                 option_len = option[1];
 395                 /* All included options should have a positive length. */
 396                 if (option_len == 0)
 397                         return -EINVAL;
 398
 399                 type = option[0];
 400                 /* All option types except Prefix Information are ignored. */
 401                 switch (type) {
 402                 case ND_OPT_SOURCE_LL_ADDR:
 403                 case ND_OPT_TARGET_LL_ADDR:
 404                 case ND_OPT_REDIRECT_HDR:
 405                 case ND_OPT_MTU:
 406                         break;
 407                 case ND_OPT_PREFIX_INFO:
 408                         prefix = (struct icmp6_ra_prefix_info *)option;
 409                         /* The link-local prefix 0xfe80::/10 is ignored. */
 410                         if ((ntohs(prefix->prefix.s6_addr16[0]) &
 411                              IPV6_LINK_LOCAL_MASK) == IPV6_LINK_LOCAL_PREFIX)
 412                                 break;
 413                         if (prefix->on_link && ntohl(prefix->valid_lifetime)) {
 414                                 net_prefix_length = prefix->prefix_len;
 415                                 net_gateway6 = ip6->saddr;
 416                                 return 0;
 417                         }
 418                         break;
 419                 default:
 420                         debug("Unknown IPv6 Neighbor Discovery Option 0x%x\n",
 421                               type);
 422                 }
 423
 424                 option_len <<= 3; /* Option length is a multiple of 8. */
 425                 remaining_option_len -= option_len;
 426                 option += option_len;
 427         }
 428
 429         return -EADDRNOTAVAIL;
 430 }
 431
 432 int ndisc_receive(struct ethernet_hdr *et, struct ip6_hdr *ip6, int len)
 433 {
 434         struct icmp6hdr *icmp =
 435             (struct icmp6hdr *)(((uchar *)ip6) + IP6_HDR_SIZE);
 436         struct nd_msg *ndisc = (struct nd_msg *)icmp;
 437         uchar neigh_eth_addr[6];
 438         int err = 0;    // The error code returned calling functions.
 439
 440         switch (icmp->icmp6_type) {
 441         case IPV6_NDISC_NEIGHBOUR_SOLICITATION:
 442                 debug("received neighbor solicitation for %pI6c from %pI6c\n",
 443                       &ndisc->target, &ip6->saddr);
 444                 if (ip6_is_our_addr(&ndisc->target) &&
 445                     ndisc_has_option(ip6, ND_OPT_SOURCE_LL_ADDR)) {
 446                         ndisc_extract_enetaddr(ndisc, neigh_eth_addr);
 447                         ip6_send_na(neigh_eth_addr, &ip6->saddr,
 448                                     &ndisc->target);
 449                 }
 450                 break;
 451
 452         case IPV6_NDISC_NEIGHBOUR_ADVERTISEMENT:
 453                 /* are we waiting for a reply ? */
 454                 if (ip6_is_unspecified_addr(&net_nd_sol_packet_ip6))
 455                         break;
 456
 457                 if ((memcmp(&ndisc->target, &net_nd_rep_packet_ip6,
 458                             sizeof(struct in6_addr)) == 0) &&
 459                     ndisc_has_option(ip6, ND_OPT_TARGET_LL_ADDR)) {
 460                         ndisc_extract_enetaddr(ndisc, neigh_eth_addr);
 461
 462                         /* save address for later use */
 463                         if (!net_nd_packet_mac)
 464                                 net_nd_packet_mac = neigh_eth_addr;
 465
 466                         /* modify header, and transmit it */
 467                         memcpy(((struct ethernet_hdr *)net_nd_tx_packet)->et_dest,
 468                                neigh_eth_addr, 6);
 469
 470                         net_send_packet(net_nd_tx_packet,
 471                                         net_nd_tx_packet_size);
 472
 473                         /* no ND request pending now */
 474                         net_nd_sol_packet_ip6 = net_null_addr_ip6;
 475                         net_nd_tx_packet_size = 0;
 476                         net_nd_packet_mac = NULL;
 477                 }
 478                 break;
 479         case IPV6_NDISC_ROUTER_SOLICITATION:
 480                 break;
 481         case IPV6_NDISC_ROUTER_ADVERTISEMENT:
 482                 debug("Received router advertisement for %pI6c from %pI6c\n",
 483                       &ip6->daddr, &ip6->saddr);
 484                 /*
 485                  * If gateway and prefix are set, the RA packet is ignored. The
 486                  * reason is that the U-Boot code is supposed to be as compact
 487                  * as possible and does not need to take care of multiple
 488                  * routers. In addition to that, U-Boot does not want to handle
 489                  * scenarios like a router setting its lifetime to zero to
 490                  * indicate it is not routing anymore. U-Boot program has a
 491                  * short life when the system boots up and does not need such
 492                  * sophistication.
 493                  */
 494                 if (!ip6_is_unspecified_addr(&net_gateway6) &&
 495                     net_prefix_length != 0) {
 496                         break;
 497                 }
 498                 if (!validate_ra(ip6)) {
 499                         debug("Invalid router advertisement message.\n");
 500                         break;
 501                 }
 502                 err = process_ra(ip6, len);
 503                 if (err)
 504                         debug("Ignored router advertisement. Error: %d\n", err);
 505                 else
 506                         printf("Set gatewayip6: %pI6c, prefix_length: %d\n",
 507                                &net_gateway6, net_prefix_length);
 508                 break;
 509         default:
 510                 debug("Unexpected ICMPv6 type 0x%x\n", icmp->icmp6_type);
 511                 return -1;
 512         }
 513
 514         return 0;
 515 }