Internet on FIRE

/*

 *        BIRD -- Routing Information Protocol (RIP)

 *

 *        (c) 1998--1999 Pavel Machek <pavel@ucw.cz>

 *        (c) 2004--2013 Ondrej Filip <feela@network.cz>

 *        (c) 2009--2015 Ondrej Zajicek <santiago@crfreenet.org>

 *        (c) 2009--2015 CZ.NIC z.s.p.o.

 *

 *        Can be freely distributed and used under the terms of the GNU GPL.

 */

#undef LOCAL_DEBUG

#include "rip.h"

#include "lib/mac.h"

#define RIP_CMD_REQUEST                1        /* want info */

#define RIP_CMD_RESPONSE        2        /* responding to request */

#define RIP_BLOCK_LENGTH        20

#define RIP_PASSWD_LENGTH        16

#define RIP_AF_IPV4                2

#define RIP_AF_AUTH                0xffff

/* RIP packet header */

struct rip_packet

{

  u8 command;

  u8 version;

  u16 unused;

};

/* RTE block for RIPv2 */

struct rip_block_v2

{

  u16 family;

  u16 tag;

  ip4_addr network;

  ip4_addr netmask;

  ip4_addr next_hop;

  u32 metric;

};

/* RTE block for RIPng */

struct rip_block_ng

{

  ip6_addr prefix;

  u16 tag;

  u8 pxlen;

  u8 metric;

};

/* Authentication block for RIPv2 */

struct rip_block_auth

{

  u16 must_be_ffff;

  u16 auth_type;

  char password[0];

  u16 packet_len;

  u8 key_id;

  u8 auth_len;

  u32 seq_num;

  u32 unused1;

  u32 unused2;

};

/* Authentication tail, RFC 4822 */

struct rip_auth_tail

{

  u16 must_be_ffff;

  u16 must_be_0001;

  byte auth_data[0];

};

/* Internal representation of RTE block data */

struct rip_block

{

  net_addr net;

  u32 metric;

  u16 tag;

  u16 no_af;

  ip_addr next_hop;

};

#define DROP(DSC,VAL) do { err_dsc = DSC; err_val = VAL; goto drop; } while(0)

#define DROP1(DSC) do { err_dsc = DSC; goto drop; } while(0)

#define SKIP(DSC) do { err_dsc = DSC; goto skip; } while(0)

#define LOG_PKT(msg, args...) \

  log_rl(&p->log_pkt_tbf, L_REMOTE "%s: " msg, p->p.name, args)

#define LOG_PKT_AUTH(msg, args...) \

  log_rl(&p->log_pkt_tbf, L_AUTH "%s: " msg, p->p.name, args)

#define LOG_RTE(msg, args...) \

  log_rl(&p->log_rte_tbf, L_REMOTE "%s: " msg, p->p.name, args)

static inline void * rip_tx_buffer(struct rip_iface *ifa)

{ return ifa->sk->tbuf; }

static inline uint rip_pkt_hdrlen(struct rip_iface *ifa)

{ return sizeof(struct rip_packet) + (ifa->cf->auth_type ? RIP_BLOCK_LENGTH : 0); }

static inline void

rip_put_block(struct rip_proto *p, byte *pos, struct rip_block *rte)

{

  if (rip_is_v2(p))

  {

    struct rip_block_v2 *block = (void *) pos;

    block->family = rte->no_af ? 0 : htons(RIP_AF_IPV4);

    block->tag = htons(rte->tag);

    block->network = ip4_hton(net4_prefix(&rte->net));

    block->netmask = ip4_hton(ip4_mkmask(net4_pxlen(&rte->net)));

    block->next_hop = ip4_hton(ipa_to_ip4(rte->next_hop));

    block->metric = htonl(rte->metric);

  }

  else /* RIPng */

  {

    struct rip_block_ng *block = (void *) pos;

    block->prefix = ip6_hton(net6_prefix(&rte->net));

    block->tag = htons(rte->tag);

    block->pxlen = net6_pxlen(&rte->net);

    block->metric = rte->metric;

  }

}

static inline void

rip_put_next_hop(struct rip_proto *p UNUSED, byte *pos, struct rip_block *rte)

{

  struct rip_block_ng *block = (void *) pos;

  block->prefix = ip6_hton(ipa_to_ip6(rte->next_hop));

  block->tag = 0;

  block->pxlen = 0;

  block->metric = 0xff;

}

static inline int

rip_get_block(struct rip_proto *p, byte *pos, struct rip_block *rte)

{

  if (rip_is_v2(p))

  {

    struct rip_block_v2 *block = (void *) pos;

    /* Skip blocks with strange AF, including authentication blocks */

    if (block->family != (rte->no_af ? 0 : htons(RIP_AF_IPV4)))

      return 0;

    uint pxlen = ip4_masklen(ip4_ntoh(block->netmask));

    net_fill_ip4(&rte->net, ip4_ntoh(block->network), pxlen);

    rte->metric = ntohl(block->metric);

    rte->tag = ntohs(block->tag);

    rte->next_hop = ipa_from_ip4(ip4_ntoh(block->next_hop));

    return 1;

  }

  else /* RIPng */

  {

    struct rip_block_ng *block = (void *) pos;

    /* Handle and skip next hop blocks */

    if (block->metric == 0xff)

    {

      rte->next_hop = ipa_from_ip6(ip6_ntoh(block->prefix));

      if (!ipa_is_link_local(rte->next_hop)) rte->next_hop = IPA_NONE;

      return 0;

    }

    uint pxlen = (block->pxlen <= IP6_MAX_PREFIX_LENGTH) ? block->pxlen : 255;

    net_fill_ip6(&rte->net, ip6_ntoh(block->prefix), pxlen);

    rte->metric = block->metric;

    rte->tag = ntohs(block->tag);

    /* rte->next_hop is deliberately kept unmodified */;

    return 1;

  }

}

static inline void

rip_update_csn(struct rip_proto *p UNUSED, struct rip_iface *ifa)

{

  /*

   * We update crypto sequence numbers at the beginning of update session to

   * avoid issues with packet reordering, so packets inside one update session

   * have the same CSN. We are using real time, but enforcing monotonicity.

   */

  if (ifa->cf->auth_type == RIP_AUTH_CRYPTO)

  {

    u32 now_real = (u32) (current_real_time() TO_S);

    ifa->csn = (ifa->csn < now_real) ? now_real : ifa->csn + 1;

  }

}

static void

rip_fill_authentication(struct rip_proto *p, struct rip_iface *ifa, struct rip_packet *pkt, uint *plen)

{

  struct rip_block_auth *auth = (void *) (pkt + 1);

  struct password_item *pass = password_find(ifa->cf->passwords, 0);

  if (!pass)

  {

    /* FIXME: This should not happen */

    log(L_ERR "%s: No suitable password found for authentication", p->p.name);

    memset(auth, 0, sizeof(struct rip_block_auth));

    return;

  }

  switch (ifa->cf->auth_type)

  {

  case RIP_AUTH_PLAIN:

    auth->must_be_ffff = htons(0xffff);

    auth->auth_type = htons(RIP_AUTH_PLAIN);

    strncpy(auth->password, pass->password, RIP_PASSWD_LENGTH);

    return;

  case RIP_AUTH_CRYPTO:

    auth->must_be_ffff = htons(0xffff);

    auth->auth_type = htons(RIP_AUTH_CRYPTO);

    auth->packet_len = htons(*plen);

    auth->key_id = pass->id;

    auth->auth_len = mac_type_length(pass->alg);

    auth->seq_num = ifa->csn_ready ? htonl(ifa->csn) : 0;

    auth->unused1 = 0;

    auth->unused2 = 0;

    ifa->csn_ready = 1;

    if (pass->alg < ALG_HMAC)

      auth->auth_len += sizeof(struct rip_auth_tail);

    /*

     * Note that RFC 4822 is unclear whether auth_len should cover whole

     * authentication trailer or just auth_data length.

     *

     * FIXME: We should use just auth_data length by default. Currently we put

     * the whole auth trailer length in keyed hash case to keep old behavior,

     * but we put just auth_data length in the new HMAC case. Note that Quagga

     * has config option for this.

     *

     * Crypto sequence numbers are increased by sender in rip_update_csn().

     * First CSN should be zero, this is handled by csn_ready.

     */

    struct rip_auth_tail *tail = (void *) ((byte *) pkt + *plen);

    tail->must_be_ffff = htons(0xffff);

    tail->must_be_0001 = htons(0x0001);

    uint auth_len = mac_type_length(pass->alg);

    *plen += sizeof(struct rip_auth_tail) + auth_len;

    /* Append key for keyed hash, append padding for HMAC (RFC 4822 2.5) */

    if (pass->alg < ALG_HMAC)

      strncpy(tail->auth_data, pass->password, auth_len);

    else

      memset32(tail->auth_data, HMAC_MAGIC, auth_len / 4);

    mac_fill(pass->alg, pass->password, pass->length,

             (byte *) pkt, *plen, tail->auth_data);

    return;

  default:

    bug("Unknown authentication type");

  }

}

static int

rip_check_authentication(struct rip_proto *p, struct rip_iface *ifa, struct rip_packet *pkt, uint *plen, struct rip_neighbor *n)

{

  struct rip_block_auth *auth = (void *) (pkt + 1);

  struct password_item *pass = NULL;

  const char *err_dsc = NULL;

  uint err_val = 0;

  uint auth_type = 0;

  /* Check for authentication entry */

  if ((*plen >= (sizeof(struct rip_packet) + sizeof(struct rip_block_auth))) &&

      (auth->must_be_ffff == htons(0xffff)))

    auth_type = ntohs(auth->auth_type);

  if (auth_type != ifa->cf->auth_type)

    DROP("authentication method mismatch", auth_type);

  switch (auth_type)

  {

  case RIP_AUTH_NONE:

    return 1;

  case RIP_AUTH_PLAIN:

    pass = password_find_by_value(ifa->cf->passwords, auth->password, RIP_PASSWD_LENGTH);

    if (!pass)

      DROP1("wrong password");

    return 1;

  case RIP_AUTH_CRYPTO:

    pass = password_find_by_id(ifa->cf->passwords, auth->key_id);

    if (!pass)

      DROP("no suitable password found", auth->key_id);

    uint data_len = ntohs(auth->packet_len);

    uint auth_len = mac_type_length(pass->alg);

    uint auth_len2 = sizeof(struct rip_auth_tail) + auth_len;

    /*

     * Ideally, first check should be check for internal consistency:

     *   (data_len + sizeof(struct rip_auth_tail) + auth->auth_len) != *plen

     *

     * Second one should check expected code length:

     *   auth->auth_len != auth_len

     *

     * But as auth->auth_len has two interpretations, we simplify this

     */

    if (data_len + auth_len2 != *plen)

      DROP("packet length mismatch", *plen);

    /* Warning: two interpretations of auth_len field */

    if ((auth->auth_len != auth_len) && (auth->auth_len != auth_len2))

      DROP("wrong authentication length", auth->auth_len);

    struct rip_auth_tail *tail = (void *) ((byte *) pkt + data_len);

    if ((tail->must_be_ffff != htons(0xffff)) || (tail->must_be_0001 != htons(0x0001)))

      DROP1("authentication trailer is missing");

    /* Accept higher sequence number, or zero if connectivity is lost */

    /* FIXME: sequence number must be password/SA specific */

    u32 rcv_csn = ntohl(auth->seq_num);

    if ((rcv_csn < n->csn) && (rcv_csn || n->uc))

    {

      /* We want to report both new and old CSN */

      LOG_PKT_AUTH("Authentication failed for %I on %s - "

                   "lower sequence number (rcv %u, old %u)",

                   n->nbr->addr, ifa->iface->name, rcv_csn, n->csn);

      return 0;

    }

    byte *auth_data = alloca(auth_len);

    memcpy(auth_data, tail->auth_data, auth_len);

    /* Append key for keyed hash, append padding for HMAC (RFC 4822 2.5) */

    if (pass->alg < ALG_HMAC)

      strncpy(tail->auth_data, pass->password, auth_len);

    else

      memset32(tail->auth_data, HMAC_MAGIC, auth_len / 4);

    if (!mac_verify(pass->alg, pass->password, pass->length,

                    (byte *) pkt, *plen, auth_data))

      DROP("wrong authentication code", pass->id);

    *plen = data_len;

    n->csn = rcv_csn;

    return 1;

  }

drop:

  LOG_PKT_AUTH("Authentication failed for %I on %s - %s (%u)",

               n->nbr->addr, ifa->iface->name, err_dsc, err_val);

  return 0;

}

static inline int

rip_send_to(struct rip_proto *p, struct rip_iface *ifa, struct rip_packet *pkt, uint plen, ip_addr dst)

{

  if (ifa->cf->auth_type)

    rip_fill_authentication(p, ifa, pkt, &plen);

  return sk_send_to(ifa->sk, plen, dst, 0);

}

void

rip_send_request(struct rip_proto *p, struct rip_iface *ifa)

{

  byte *pos = rip_tx_buffer(ifa);

  struct rip_packet *pkt = (void *) pos;

  pkt->command = RIP_CMD_REQUEST;

  pkt->version = ifa->cf->version;

  pkt->unused = 0;

  pos += rip_pkt_hdrlen(ifa);

  struct rip_block b = { .no_af = 1, .metric = p->infinity };

  rip_put_block(p, pos, &b);

  pos += RIP_BLOCK_LENGTH;

  rip_update_csn(p, ifa);

  TRACE(D_PACKETS, "Sending request via %s", ifa->iface->name);

  rip_send_to(p, ifa, pkt, pos - (byte *) pkt, ifa->addr);

}

static void

rip_receive_request(struct rip_proto *p, struct rip_iface *ifa, struct rip_packet *pkt, uint plen, struct rip_neighbor *from)

{

  TRACE(D_PACKETS, "Request received from %I on %s", from->nbr->addr, ifa->iface->name);

  byte *pos = (byte *) pkt + rip_pkt_hdrlen(ifa);

  /* We expect one regular block */

  if (plen != (rip_pkt_hdrlen(ifa) + RIP_BLOCK_LENGTH))

    return;

  struct rip_block b = { .no_af = 1 };

  if (!rip_get_block(p, pos, &b))

    return;

  /* Special case - infinity metric, for RIPng also zero prefix */

  if ((b.metric != p->infinity) ||

      (rip_is_ng(p) && !net_zero_ip6((net_addr_ip6 *) &b.net)))

    return;

  /* We do nothing if TX is already active */

  if (ifa->tx_active)

  {

    TRACE(D_EVENTS, "Skipping request from %I on %s, TX is busy", from->nbr->addr, ifa->iface->name);

    return;

  }

  if (!ifa->cf->passive)

    rip_send_table(p, ifa, from->nbr->addr, 0);

}

static int

rip_send_response(struct rip_proto *p, struct rip_iface *ifa)

{

  if (! ifa->tx_active)

    return 0;

  byte *pos = rip_tx_buffer(ifa);

  byte *max = rip_tx_buffer(ifa) + ifa->tx_plen -

    (rip_is_v2(p) ? RIP_BLOCK_LENGTH : 2*RIP_BLOCK_LENGTH);

  ip_addr last_next_hop = IPA_NONE;

  btime now_ = current_time();

  int send = 0;

  struct rip_packet *pkt = (void *) pos;

  pkt->command = RIP_CMD_RESPONSE;

  pkt->version = ifa->cf->version;

  pkt->unused = 0;

  pos += rip_pkt_hdrlen(ifa);

  FIB_ITERATE_START(&p->rtable, &ifa->tx_fit, struct rip_entry, en)

  {

    /* Dummy entries */

    if (!en->valid)

      goto next_entry;

    /* Stale entries that should be removed */

    if ((en->valid == RIP_ENTRY_STALE) &&

        ((en->changed + ifa->cf->garbage_time) <= now_))

      goto next_entry;

    /* Triggered updates */

    if (en->changed < ifa->tx_changed)

      goto next_entry;

    /* Not enough space for current entry */

    if (pos > max)

    {

      FIB_ITERATE_PUT(&ifa->tx_fit);

      goto break_loop;

    }

    struct rip_block rte = {

      .metric = en->metric,

      .tag = en->tag

    };

    net_copy(&rte.net, en->n.addr);

    if (en->iface == ifa->iface)

      rte.next_hop = en->next_hop;

    if (rip_is_v2(p) && (ifa->cf->version == RIP_V1))

    {

      /* Skipping subnets (i.e. not hosts, classful networks or default route) */

      if (ip4_masklen(ip4_class_mask(net4_prefix(&rte.net))) != rte.net.pxlen)

        goto next_entry;

      rte.tag = 0;

      rte.net.pxlen = 0;

      rte.next_hop = IPA_NONE;

    }

    /* Split horizon */

    if (en->from == ifa->iface && ifa->cf->split_horizon)

    {

      if (ifa->cf->poison_reverse)

      {

        rte.metric = p->infinity;

        rte.next_hop = IPA_NONE;

      }

      else

        goto next_entry;

    }

    // TRACE(D_PACKETS, "    %N -> %I metric %d", &rte.net, rte.next_hop, rte.metric);

    /* RIPng next hop entry */

    if (rip_is_ng(p) && !ipa_equal(rte.next_hop, last_next_hop))

    {

      last_next_hop = rte.next_hop;

      rip_put_next_hop(p, pos, &rte);

      pos += RIP_BLOCK_LENGTH;

    }

    rip_put_block(p, pos, &rte);

    pos += RIP_BLOCK_LENGTH;

    send = 1;

  next_entry: ;

  }

  FIB_ITERATE_END;

  ifa->tx_active = 0;

  /* Do not send empty packet */

  if (!send)

    return 0;

break_loop:

  TRACE(D_PACKETS, "Sending response via %s", ifa->iface->name);

  return rip_send_to(p, ifa, pkt, pos - (byte *) pkt, ifa->tx_addr);

}

/**

 * rip_send_table - RIP interface timer hook

 * @p: RIP instance

 * @ifa: RIP interface

 * @addr: destination IP address

 * @changed: time limit for triggered updates

 *

 * The function activates an update session and starts sending routing update

 * packets (using rip_send_response()). The session may be finished during the

 * call or may continue in rip_tx_hook() until all appropriate routes are

 * transmitted. Note that there may be at most one active update session per

 * interface, the function will terminate the old active session before

 * activating the new one.

 */

void

rip_send_table(struct rip_proto *p, struct rip_iface *ifa, ip_addr addr, btime changed)

{

  DBG("RIP: Opening TX session to %I on %s\n", addr, ifa->iface->name);

  rip_reset_tx_session(p, ifa);

  ifa->tx_active = 1;

  ifa->tx_addr = addr;

  ifa->tx_changed = changed;

  FIB_ITERATE_INIT(&ifa->tx_fit, &p->rtable);

  rip_update_csn(p, ifa);

  while (rip_send_response(p, ifa) > 0)

    ;

}

static void

rip_tx_hook(sock *sk)

{

  struct rip_iface *ifa = sk->data;

  struct rip_proto *p = ifa->rip;

  DBG("RIP: TX hook called (iface %s, src %I, dst %I)\n",

      sk->iface->name, sk->saddr, sk->daddr);

  while (rip_send_response(p, ifa) > 0)

    ;

}

static void

rip_err_hook(sock *sk, int err)

{

  struct rip_iface *ifa = sk->data;

  struct rip_proto *p = ifa->rip;

  log(L_ERR "%s: Socket error on %s: %M", p->p.name, ifa->iface->name, err);

  rip_reset_tx_session(p, ifa);

}

static void

rip_receive_response(struct rip_proto *p, struct rip_iface *ifa, struct rip_packet *pkt, uint plen, struct rip_neighbor *from)

{

  struct rip_block rte = {};

  const char *err_dsc = NULL;

  TRACE(D_PACKETS, "Response received from %I on %s", from->nbr->addr, ifa->iface->name);

  byte *pos = (byte *) pkt + sizeof(struct rip_packet);

  byte *end = (byte *) pkt + plen;

  btime now_ = current_time();

  for (; pos < end; pos += RIP_BLOCK_LENGTH)

  {

    /* Find next regular RTE */

    if (!rip_get_block(p, pos, &rte))

      continue;

    if (rip_is_v2(p) && (pkt->version == RIP_V1))

    {

      if (ifa->cf->check_zero && (rte.tag || rte.net.pxlen || ipa_nonzero(rte.next_hop)))

        SKIP("RIPv1 reserved field is nonzero");

      rte.tag = 0;

      rte.net.pxlen = ip4_masklen(ip4_class_mask(net4_prefix(&rte.net)));

      rte.next_hop = IPA_NONE;

    }

    if (rte.net.pxlen == 255)

      SKIP("invalid prefix length");

    net_normalize(&rte.net);

    int c = net_classify(&rte.net);

    if ((c < 0) || !(c & IADDR_HOST) || ((c & IADDR_SCOPE_MASK) <= SCOPE_LINK))

      SKIP("invalid prefix");

    if (rte.metric > p->infinity)

      SKIP("invalid metric");

    if (ipa_nonzero(rte.next_hop))

    {

      neighbor *nbr = neigh_find2(&p->p, &rte.next_hop, ifa->iface, 0);

      if (!nbr || (nbr->scope <= 0))

        rte.next_hop = IPA_NONE;

    }

    // TRACE(D_PACKETS, "    %N -> %I metric %d", &rte.net.n, rte.next_hop, rte.metric);

    rte.metric += ifa->cf->metric;

    if (rte.metric < p->infinity)

    {

      struct rip_rte new = {

        .from = from,

        .next_hop = ipa_nonzero(rte.next_hop) ? rte.next_hop : from->nbr->addr,

        .metric = rte.metric,

        .tag = rte.tag,

        .expires = now_ + ifa->cf->timeout_time

      };

      rip_update_rte(p, &rte.net, &new);

    }

    else

      rip_withdraw_rte(p, &rte.net, from);

    continue;

  skip:

    LOG_RTE("Ignoring route %N received from %I - %s",

            &rte.net, from->nbr->addr, err_dsc);

  }

}

static int

rip_rx_hook(sock *sk, uint len)

{

  struct rip_iface *ifa = sk->data;

  struct rip_proto *p = ifa->rip;

  const char *err_dsc = NULL;

  uint err_val = 0;

  if (sk->lifindex != sk->iface->index)

    return 1;

  DBG("RIP: RX hook called (iface %s, src %I, dst %I)\n",

      sk->iface->name, sk->faddr, sk->laddr);

  /* Silently ignore my own packets */

  if (ipa_equal(sk->faddr, sk->saddr))

    return 1;

  if (rip_is_ng(p) && !ipa_is_link_local(sk->faddr))

    DROP1("wrong src address");

  struct rip_neighbor *n = rip_get_neighbor(p, &sk->faddr, ifa);

  if (!n)

    DROP1("not from neighbor");

  if ((ifa->cf->ttl_security == 1) && (sk->rcv_ttl < 255))

    DROP("wrong TTL", sk->rcv_ttl);

  if (sk->fport != sk->dport)

    DROP("wrong src port", sk->fport);

  if (len < sizeof(struct rip_packet))

    DROP("too short", len);

  if (sk->flags & SKF_TRUNCATED)

    DROP("truncated", len);

  struct rip_packet *pkt = (struct rip_packet *) sk->rbuf;

  uint plen = len;

  if (!pkt->version || (ifa->cf->version_only && (pkt->version != ifa->cf->version)))

    DROP("wrong version", pkt->version);

  /* rip_check_authentication() has its own error logging */

  if (rip_is_v2(p) && !rip_check_authentication(p, ifa, pkt, &plen, n))

    return 1;

  if ((plen - sizeof(struct rip_packet)) % RIP_BLOCK_LENGTH)

    DROP("invalid length", plen);

  n->last_seen = current_time();

  rip_update_bfd(p, n);

  switch (pkt->command)

  {

  case RIP_CMD_REQUEST:

    rip_receive_request(p, ifa, pkt, plen, n);

    break;

  case RIP_CMD_RESPONSE:

    rip_receive_response(p, ifa, pkt, plen, n);

    break;

  default:

    DROP("unknown command", pkt->command);

  }

  return 1;

drop:

  LOG_PKT("Bad packet from %I via %s - %s (%u)",

          sk->faddr, sk->iface->name, err_dsc, err_val);

  return 1;

}

int

rip_open_socket(struct rip_iface *ifa)

{

  struct rip_proto *p = ifa->rip;

  sock *sk = sk_new(p->p.pool);

  sk->type = SK_UDP;

  sk->subtype = rip_is_v2(p) ? SK_IPV4 : SK_IPV6;

  sk->sport = ifa->cf->port;

  sk->dport = ifa->cf->port;

  sk->iface = ifa->iface;

  sk->saddr = rip_is_v2(p) ? ifa->iface->addr4->ip : ifa->iface->llv6->ip;

  sk->rx_hook = rip_rx_hook;

  sk->tx_hook = rip_tx_hook;

  sk->err_hook = rip_err_hook;

  sk->data = ifa;

  sk->tos = ifa->cf->tx_tos;

  sk->priority = ifa->cf->tx_priority;

  sk->ttl = ifa->cf->ttl_security ? 255 : 1;

  sk->flags = SKF_LADDR_RX | ((ifa->cf->ttl_security == 1) ? SKF_TTL_RX : 0);

  /* sk->rbsize and sk->tbsize are handled in rip_iface_update_buffers() */

  if (sk_open(sk) < 0)

    goto err;

  if (ifa->cf->mode == RIP_IM_MULTICAST)

  {

    if (sk_setup_multicast(sk) < 0)

      goto err;

    if (sk_join_group(sk, ifa->addr) < 0)

      goto err;

  }

  else /* Broadcast */

  {

    if (sk_setup_broadcast(sk) < 0)

      goto err;

    if (ipa_zero(ifa->addr))

    {

      sk->err = "Missing broadcast address";

      goto err;

    }

  }

  ifa->sk = sk;

  return 1;

err:

  sk_log_error(sk, p->p.name);

  rfree(sk);

  return 0;

}