/*

 *

 *   Authors:

 *    Pedro Roque   <roque@di.fc.ul.pt>

 *    Lars Fenneberg    <lf@elemental.net>

 *

 *   This software is Copyright 1996,1997 by the above mentioned author(s),

 *   All Rights Reserved.

 *

 *   The license which is distributed with this software in the file COPYRIGHT

 *   applies to this software. If your distribution is missing this file, you

 *   may request it from <reubenhwk@gmail.com>.

 *

 */

#include "config.h"

#include "includes.h"

#include "radvd.h"

static void process_rs(int sock, struct Interface *, unsigned char *msg, int len, struct sockaddr_in6 *);

static void process_ra(struct Interface *, unsigned char *msg, int len, struct sockaddr_in6 *);

static int addr_match(struct in6_addr *a1, struct in6_addr *a2, int prefixlen);

void process(int sock, struct Interface *interfaces, unsigned char *msg, int len, struct sockaddr_in6 *addr,

       struct in6_pktinfo *pkt_info, int hoplimit)

{

  char if_namebuf[IF_NAMESIZE] = {""};

  char *if_name = if_indextoname(pkt_info->ipi6_ifindex, if_namebuf);

  if (!if_name) {

    if_name = "unknown interface";

  }

  dlog(LOG_DEBUG, 4, "%s received a packet", if_name);

  char addr_str[INET6_ADDRSTRLEN];

  addrtostr(&addr->sin6_addr, addr_str, sizeof(addr_str));

  if (!pkt_info) {

    flog(LOG_WARNING, "%s received packet with no pkt_info from %s!", if_name, addr_str);

    return;

  }

  /*

   * can this happen?

   */

  if (len < sizeof(struct icmp6_hdr)) {

    flog(LOG_WARNING, "%s received icmpv6 packet with invalid length (%d) from %s", if_name, len, addr_str);

    return;

  }

  struct icmp6_hdr *icmph = (struct icmp6_hdr *)msg;

  if (icmph->icmp6_type != ND_ROUTER_SOLICIT && icmph->icmp6_type != ND_ROUTER_ADVERT) {

    /*

     *      We just want to listen to RSs and RAs

     */

    flog(LOG_ERR, "%s icmpv6 filter failed", if_name);

    return;

  }

  if (icmph->icmp6_type == ND_ROUTER_ADVERT) {

    if (len < sizeof(struct nd_router_advert)) {

      flog(LOG_WARNING, "%s received icmpv6 RA packet with invalid length (%d) from %s", if_name, len,

           addr_str);

      return;

    }

    if (!IN6_IS_ADDR_LINKLOCAL(&addr->sin6_addr)) {

      flog(LOG_WARNING, "%s received icmpv6 RA packet with non-linklocal source address from %s", if_name,

           addr_str);

      return;

    }

  }

  if (icmph->icmp6_type == ND_ROUTER_SOLICIT) {

    if (len < sizeof(struct nd_router_solicit)) {

      flog(LOG_WARNING, "%s received icmpv6 RS packet with invalid length (%d) from %s", if_name, len,

           addr_str);

      return;

    }

  }

  if (icmph->icmp6_code != 0) {

    flog(LOG_WARNING, "%s received icmpv6 RS/RA packet with invalid code (%d) from %s", if_name, icmph->icmp6_code,

         addr_str);

    return;

  }

  /* get iface by received if_index */

  struct Interface *iface = find_iface_by_index(interfaces, pkt_info->ipi6_ifindex);

  if (iface == NULL) {

    dlog(LOG_WARNING, 4, "%s received icmpv6 RS/RA packet on an unknown interface with index %d", if_name,

         pkt_info->ipi6_ifindex);

    return;

  }

  if (!iface->state_info.ready && (0 != setup_iface(sock, iface))) {

    flog(LOG_WARNING, "%s received RS or RA on %s but %s is not ready and setup_iface failed", if_name,

         iface->props.name, iface->props.name);

    return;

  }

  if (hoplimit != 255) {

    flog(LOG_WARNING, "%s received RS or RA with invalid hoplimit %d from %s", if_name, hoplimit, addr_str);

    return;

  }

  if (icmph->icmp6_type == ND_ROUTER_SOLICIT) {

    dlog(LOG_DEBUG, 3, "%s received RS from: %s", if_name, addr_str);

    process_rs(sock, iface, msg, len, addr);

  } else if (icmph->icmp6_type == ND_ROUTER_ADVERT) {

    if (0 == memcmp(&addr->sin6_addr, &iface->props.if_addr, sizeof(iface->props.if_addr))) {

      dlog(LOG_DEBUG, 3, "%s received RA from: %s (myself)", if_name, addr_str);

    } else {

      dlog(LOG_DEBUG, 3, "%s received RA from: %s", if_name, addr_str);

    }

    process_ra(iface, msg, len, addr);

  }

}

static void process_rs(int sock, struct Interface *iface, unsigned char *msg, int len, struct sockaddr_in6 *addr)

{

  /* RFC 7772, section 5.1:

   * 5.1.  Network-Side Recommendations

   *    1.  Router manufacturers SHOULD allow network administrators to

   *        configure the routers to respond to Router Solicitations with

   *        unicast Router Advertisements if:

   *        *  The Router Solicitation's source address is not the

   *           unspecified address, and:

   *        *  The solicitation contains a valid Source Link-Layer Address

   *           option.

   *

   * However, testing shows that many clients do not set the SLLA option:

   * https://github.com/reubenhwk/radvd/issues/63#issuecomment-287172252

   * As of 2017/03/16:

   * - macOS 10.12.3 sierra - sends SLLA 2 times out of 4

   * - iOS 10.2.1 (iPhone 5s) - no SLLA

   * - Android 7.0 (sony xperia phone) - sends SLLA

   * - Android 5.1 (nexus 7 tablet) - sends SLLA

   * - Ubuntu 16.04.2 LTS w/ Network Manager, running 4.9 kernel (dell laptop) - no SLLA

   * - Windows 10 (dell laptop) - no SLLA

   *

   * We decide to ignore the SLLA option for now, and only require the

   * unspecified address check. Clients that did not set the SLLA option will

   * trigger a neighbour solicit to the solicited-node address trying to

   * resolve the link-local address to, this would still be less traffic than

   * the all-nodes multicast.

   */

  int rfc7772_unicast_response = iface->AdvRASolicitedUnicast && !IN6_IS_ADDR_UNSPECIFIED(&addr->sin6_addr);

  /* validation */

  len -= sizeof(struct nd_router_solicit);

  uint8_t *opt_str = (uint8_t *)(msg + sizeof(struct nd_router_solicit));

  while (len > 0) {

    if (len < 2) {

      flog(LOG_WARNING, "trailing garbage in RS");

      return;

    }

    int const optlen = (opt_str[1] << 3);

    if (optlen == 0) {

      flog(LOG_WARNING, "zero length option in RS");

      return;

    } else if (optlen > len) {

      flog(LOG_WARNING, "option length greater than total length in RS");

      return;

    }

    if (*opt_str == ND_OPT_SOURCE_LINKADDR && IN6_IS_ADDR_UNSPECIFIED(&addr->sin6_addr)) {

      flog(LOG_WARNING,

           "received icmpv6 RS packet with unspecified source address and there is a lladdr option");

      return;

    }

    len -= optlen;

    opt_str += optlen;

  }

  struct timespec ts;

  clock_gettime(CLOCK_MONOTONIC, &ts);

  double const delay = (MAX_RA_DELAY_SECONDS * rand() / (RAND_MAX + 1.0));

  if (iface->UnicastOnly || rfc7772_unicast_response) {

    send_ra_forall(sock, iface, &addr->sin6_addr);

  } else if (timespecdiff(&ts, &iface->times.last_multicast) / 1000.0 < iface->MinDelayBetweenRAs) {

    /* last RA was sent only a few moments ago, don't send another immediately. */

    double next = iface->MinDelayBetweenRAs - (ts.tv_sec + ts.tv_nsec / 1000000000.0) +

            (iface->times.last_multicast.tv_sec + iface->times.last_multicast.tv_nsec / 1000000000.0) + delay;

    dlog(LOG_DEBUG, 5, "%s: rate limiting RA's, rescheduling RA %f seconds from now", iface->props.name, next);

    reschedule_iface(iface, next);

  } else {

    /* no RA sent in a while, send a multicast reply */

    send_ra_forall(sock, iface, NULL);

    double next = rand_between(iface->MinRtrAdvInterval, iface->MaxRtrAdvInterval);

    reschedule_iface(iface, next);

  }

  dlog(LOG_DEBUG, 2, "%s processed an RS", iface->props.name);

}

/*

 * check router advertisements according to RFC 4861, 6.2.7

 */

static void process_ra(struct Interface *iface, unsigned char *msg, int len, struct sockaddr_in6 *addr)

{

  char addr_str[INET6_ADDRSTRLEN];

  addrtostr(&addr->sin6_addr, addr_str, sizeof(addr_str));

  struct nd_router_advert *radvert = (struct nd_router_advert *)msg;

  if ((radvert->nd_ra_curhoplimit && iface->ra_header_info.AdvCurHopLimit) &&

      (radvert->nd_ra_curhoplimit != iface->ra_header_info.AdvCurHopLimit)) {

    flog(LOG_WARNING, "our AdvCurHopLimit on %s doesn't agree with %s", iface->props.name, addr_str);

  }

  if ((radvert->nd_ra_flags_reserved & ND_RA_FLAG_MANAGED) && !iface->ra_header_info.AdvManagedFlag) {

    flog(LOG_WARNING, "our AdvManagedFlag on %s doesn't agree with %s", iface->props.name, addr_str);

  }

  if ((radvert->nd_ra_flags_reserved & ND_RA_FLAG_OTHER) && !iface->ra_header_info.AdvOtherConfigFlag) {

    flog(LOG_WARNING, "our AdvOtherConfigFlag on %s doesn't agree with %s", iface->props.name, addr_str);

  }

  /* note: we don't check the default router preference here, because they're likely different */

  if ((radvert->nd_ra_reachable && iface->ra_header_info.AdvReachableTime) &&

      (ntohl(radvert->nd_ra_reachable) != iface->ra_header_info.AdvReachableTime)) {

    flog(LOG_WARNING, "our AdvReachableTime on %s doesn't agree with %s", iface->props.name, addr_str);

  }

  if ((radvert->nd_ra_retransmit && iface->ra_header_info.AdvRetransTimer) &&

      (ntohl(radvert->nd_ra_retransmit) != iface->ra_header_info.AdvRetransTimer)) {

    flog(LOG_WARNING, "our AdvRetransTimer on %s doesn't agree with %s", iface->props.name, addr_str);

  }

  len -= sizeof(struct nd_router_advert);

  if (len == 0)

    return;

  uint8_t *opt_str = (uint8_t *)(msg + sizeof(struct nd_router_advert));

  while (len > 0) {

    if (len < 2) {

      flog(LOG_ERR, "trailing garbage in RA on %s from %s", iface->props.name, addr_str);

      break;

    }

    int optlen = (opt_str[1] << 3);

    if (optlen == 0) {

      flog(LOG_ERR, "zero length option in RA on %s from %s", iface->props.name, addr_str);

      break;

    } else if (optlen > len) {

      flog(LOG_ERR, "option length (%d) greater than total"

              " length (%d) in RA on %s from %s",

           optlen, len, iface->props.name, addr_str);

      break;

    }

    switch (*opt_str) {

    case ND_OPT_MTU: {

      struct nd_opt_mtu *mtu = (struct nd_opt_mtu *)opt_str;

      if (len < sizeof(*mtu))

        return;

      if (iface->AdvLinkMTU && (ntohl(mtu->nd_opt_mtu_mtu) != iface->AdvLinkMTU)) {

        flog(LOG_WARNING, "our AdvLinkMTU on %s doesn't agree with %s", iface->props.name, addr_str);

      }

      break;

    }

    case ND_OPT_PREFIX_INFORMATION: {

      struct nd_opt_prefix_info *pinfo = (struct nd_opt_prefix_info *)opt_str;

      if (len < sizeof(*pinfo))

        return;

      int preferred = ntohl(pinfo->nd_opt_pi_preferred_time);

      int valid = ntohl(pinfo->nd_opt_pi_valid_time);

      struct AdvPrefix *prefix = iface->AdvPrefixList;

      while (prefix) {

        char prefix_str[INET6_ADDRSTRLEN];

        if ((prefix->PrefixLen == pinfo->nd_opt_pi_prefix_len) &&

            addr_match(&prefix->Prefix, &pinfo->nd_opt_pi_prefix, prefix->PrefixLen)) {

          addrtostr(&prefix->Prefix, prefix_str, sizeof(prefix_str));

          if (!prefix->DecrementLifetimesFlag && valid != prefix->AdvValidLifetime) {

            flog(LOG_WARNING, "our AdvValidLifetime on"

                  " %s for %s doesn't agree with %s",

                 iface->props.name, prefix_str, addr_str);

          }

          if (!prefix->DecrementLifetimesFlag && preferred != prefix->AdvPreferredLifetime) {

            flog(LOG_WARNING, "our AdvPreferredLifetime on"

                  " %s for %s doesn't agree with %s",

                 iface->props.name, prefix_str, addr_str);

          }

        }

        prefix = prefix->next;

      }

      break;

    }

    case ND_OPT_ROUTE_INFORMATION:

      /* not checked: these will very likely vary a lot */

      break;

    case ND_OPT_SOURCE_LINKADDR:

      /* not checked */

      break;

    case ND_OPT_TARGET_LINKADDR:

    case ND_OPT_REDIRECTED_HEADER:

      flog(LOG_ERR, "invalid option %d in RA on %s from %s", (int)*opt_str, iface->props.name, addr_str);

      break;

    /* Mobile IPv6 extensions */

    case ND_OPT_RTR_ADV_INTERVAL:

    case ND_OPT_HOME_AGENT_INFO:

      /* not checked */

      break;

    case ND_OPT_RDNSS_INFORMATION: {

      char rdnss_str[INET6_ADDRSTRLEN];

      struct nd_opt_rdnss_info_local *rdnssinfo = (struct nd_opt_rdnss_info_local *)opt_str;

      if (len < sizeof(*rdnssinfo))

        return;

      // must be a multiple of 2, in the range of 3..255

      // https://datatracker.ietf.org/doc/html/rfc8106#section-5.1

      if (rdnssinfo->nd_opt_rdnssi_len >= 3 && rdnssinfo->nd_opt_rdnssi_len % 2 == 1) {

        for (int i = 0; i < (rdnssinfo->nd_opt_rdnssi_len - 1) / 2; i++) {

          if (!check_rdnss_presence(iface->AdvRDNSSList, &rdnssinfo->nd_opt_rdnssi_addr[i])) {

            addrtostr(&rdnssinfo->nd_opt_rdnssi_addr[i], rdnss_str, sizeof(rdnss_str));

            flog(LOG_WARNING, "RDNSS address %s received on %s from %s is not advertised by us",

                 rdnss_str, iface->props.name, addr_str);

          }

        }

      } else {

        flog(LOG_ERR, "invalid len %i in RDNSS option on %s from %s",

             rdnssinfo->nd_opt_rdnssi_len, iface->props.name, addr_str);

      }

      break;

    }

    case ND_OPT_DNSSL_INFORMATION: {

      struct nd_opt_dnssl_info_local *dnsslinfo = (struct nd_opt_dnssl_info_local *)opt_str;

      if (len < sizeof(*dnsslinfo))

        return;

      for (int offset = 0; offset < (dnsslinfo->nd_opt_dnssli_len - 1) * 8;) {

        char suffix[256] = {""};

        if (&dnsslinfo->nd_opt_dnssli_suffixes[offset] - opt_str >= len)

          return;

        int label_len = dnsslinfo->nd_opt_dnssli_suffixes[offset++];

        if (label_len == 0) {

          /*

           * Ignore empty suffixes. They're

           * probably just padding...

           */

          if (suffix[0] == '\0')

            continue;

          if (!check_dnssl_presence(iface->AdvDNSSLList, suffix)) {

            flog(LOG_WARNING,

                 "DNSSL suffix %s received on %s from %s is not advertised by us", suffix,

                 iface->props.name, addr_str);

          }

          suffix[0] = '\0';

          continue;

        }

        /*

         * 1) must not overflow int: label + 2, offset + label_len

         * 2) last byte of dnssli_suffix must not overflow opt_str + len

         */

        if ((sizeof(suffix) - strlen(suffix)) < (label_len + 2) || label_len >= (INT_MAX - 1) ||

            &dnsslinfo->nd_opt_dnssli_suffixes[offset + label_len] - opt_str >= len ||

            offset + label_len < offset) {

          flog(LOG_ERR, "oversized suffix in DNSSL option on %s from %s", iface->props.name,

               addr_str);

          break;

        }

        if (suffix[0] != '\0')

          strcat(suffix, ".");

        strncat(suffix, (char *)&dnsslinfo->nd_opt_dnssli_suffixes[offset], label_len);

        offset += label_len;

      }

      break;

    }

    case ND_OPT_PREF64:

      /* not checked */

      break;

    default:

      dlog(LOG_DEBUG, 1, "unknown option %d in RA on %s from %s", (int)*opt_str, iface->props.name, addr_str);

      break;

    }

    len -= optlen;

    opt_str += optlen;

  }

  dlog(LOG_DEBUG, 2, "processed RA on %s", iface->props.name);

}

static int addr_match(struct in6_addr *a1, struct in6_addr *a2, int prefixlen)

{

  unsigned int pdw = prefixlen >> 0x05; /* num of whole uint32_t in prefix */

  if (pdw) {

    if (memcmp(a1, a2, pdw << 2))

      return 0;

  }

  unsigned int pbi = prefixlen & 0x1f; /* num of bits in incomplete uint32_t in prefix */

  if (pbi) {

    uint32_t w1 = *((uint32_t *)a1 + pdw);

    uint32_t w2 = *((uint32_t *)a2 + pdw);

    uint32_t mask = htonl(((uint32_t)0xffffffff) << (0x20 - pbi));

    if ((w1 ^ w2) & mask)

      return 0;

  }

  return 1;

}