eigrpd: Only install up to eigrp->max_paths into rib.

[mirror_frr.git] / eigrpd / eigrp_hello.c

/*
 * EIGRP Sending and Receiving EIGRP Hello Packets.
 * Copyright (C) 2013-2016
 * Authors:
 *   Donnie Savage
 *   Jan Janovic
 *   Matej Perina
 *   Peter Orsag
 *   Peter Paluch
 *   Frantisek Gazo
 *   Tomas Hvorkovy
 *   Martin Kontsek
 *   Lukas Koribsky
 *
 * This file is part of GNU Zebra.
 *
 * GNU Zebra is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2, or (at your option) any
 * later version.
 *
 * GNU Zebra is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with GNU Zebra; see the file COPYING.  If not, write to the Free
 * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
 * 02111-1307, USA.
 */

#include <zebra.h>

#include "thread.h"
#include "memory.h"
#include "linklist.h"
#include "prefix.h"
#include "if.h"
#include "table.h"
#include "sockunion.h"
#include "stream.h"
#include "log.h"
#include "sockopt.h"
#include "checksum.h"
#include "vty.h"
#include "md5.h"

#include "eigrpd/eigrp_structs.h"
#include "eigrpd/eigrpd.h"
#include "eigrpd/eigrp_interface.h"
#include "eigrpd/eigrp_neighbor.h"
#include "eigrpd/eigrp_packet.h"
#include "eigrpd/eigrp_zebra.h"
#include "eigrpd/eigrp_vty.h"
#include "eigrpd/eigrp_dump.h"
#include "eigrpd/eigrp_macros.h"

/* Packet Type String. */
static const struct message eigrp_general_tlv_type_str[] =
{
  { EIGRP_TLV_PARAMETER,	"PARAMETER"		},
  { EIGRP_TLV_AUTH,		"AUTH"			},
  { EIGRP_TLV_SEQ,		"SEQ"			},
  { EIGRP_TLV_SW_VERSION,	"SW_VERSION"		},
  { EIGRP_TLV_NEXT_MCAST_SEQ,	"NEXT_MCAST_SEQ"	},
  { EIGRP_TLV_PEER_TERMINATION,	"PEER_TERMINATION"	},
  { EIGRP_TLV_PEER_MTRLIST,	"PEER_MTRLIST"		},
  { EIGRP_TLV_PEER_TIDLIST,	"PEER_TIDLIST"		},
};

static const size_t eigrp_general_tlv_type_str_max = sizeof(eigrp_general_tlv_type_str) /
  sizeof(eigrp_general_tlv_type_str[0]);


/*
 * @fn eigrp_hello_timer
 *
 * @param[in]	thread	current execution thread timer is associated with
 * 
 * @return int	always returns 0
 *
 * @par
 * Called once per "hello" time interval, default 5 seconds
 * Sends hello packet via multicast for all interfaces eigrp
 * is configured for
 */
int
eigrp_hello_timer (struct thread *thread)
{
  struct eigrp_interface *ei;

  ei = THREAD_ARG(thread);
  ei->t_hello = NULL;

  if (IS_DEBUG_EIGRP(0, TIMERS))
    zlog_debug ("Start Hello Timer (%s) Expire [%u]",
                IF_NAME(ei), EIGRP_IF_PARAM(ei, v_hello));

  /* Sending hello packet. */
  eigrp_hello_send(ei, EIGRP_HELLO_NORMAL, NULL);

  /* Hello timer set. */
  ei->t_hello = thread_add_timer(master, eigrp_hello_timer, ei,
				 EIGRP_IF_PARAM(ei, v_hello));

  return 0;
}

/**
 * @fn eigrp_hello_parameter_decode
 *
 * @param[in]		nbr	neighbor the ACK should be sent to
 * @param[in]		param	pointer packet TLV is stored to
 *
 * @return u_int16_t	number of bytes added to packet stream
 *
 * @par
 * Encode Parameter TLV, used to convey metric weights and the hold time.
 *
 * @usage
 * Note the addition of K6 for the new extended metrics, and does not apply to
 * older TLV packet formats.
 */
static void
eigrp_hello_parameter_decode (struct eigrp_neighbor *nbr,
			       struct eigrp_tlv_hdr_type *tlv)			      
{
  struct eigrp *eigrp = nbr->ei->eigrp;
  struct TLV_Parameter_Type *param = (struct TLV_Parameter_Type *)tlv;

  /* copy over the values passed in by the neighbor */
  nbr->K1 = param->K1;
  nbr->K2 = param->K2;
  nbr->K3 = param->K3;
  nbr->K4 = param->K4;
  nbr->K5 = param->K5;
  nbr->K6 = param->K6;
  nbr->v_holddown = ntohs(param->hold_time);

  /*
   * Check K1-K5 have the correct values to be able to become neighbors
   * K6 does not have to match
   */
  if ((eigrp->k_values[0] == nbr->K1) &&
      (eigrp->k_values[1] == nbr->K2) &&
      (eigrp->k_values[2] == nbr->K3) &&
      (eigrp->k_values[3] == nbr->K4) &&
      (eigrp->k_values[4] == nbr->K5))
    {

      if (eigrp_nbr_state_get(nbr) == EIGRP_NEIGHBOR_DOWN)
	{
	  zlog_info("Neighbor %s (%s) is pending: new adjacency",
		    inet_ntoa(nbr->src), ifindex2ifname(nbr->ei->ifp->ifindex, VRF_DEFAULT));

	  /* Expedited hello sent */
	    eigrp_hello_send(nbr->ei, EIGRP_HELLO_NORMAL, NULL);

//	  if(ntohl(nbr->ei->address->u.prefix4.s_addr) > ntohl(nbr->src.s_addr))
	      eigrp_update_send_init(nbr);

	  eigrp_nbr_state_set(nbr, EIGRP_NEIGHBOR_PENDING);
	}
    }
  else
    {
      if (eigrp_nbr_state_get(nbr) != EIGRP_NEIGHBOR_DOWN)
	{
	  if ((param->K1 & param->K2 & param->K3 & param->K4 & param->K5) == 255)
	    {
              zlog_info ("Neighbor %s (%s) is down: Interface PEER-TERMINATION received",
                         inet_ntoa (nbr->src),ifindex2ifname (nbr->ei->ifp->ifindex, VRF_DEFAULT));
              eigrp_nbr_delete (nbr);
	    }
	  else
	    {
              zlog_info ("Neighbor %s (%s) going down: Kvalue mismatch",
                         inet_ntoa (nbr->src),ifindex2ifname (nbr->ei->ifp->ifindex, VRF_DEFAULT));
              eigrp_nbr_state_set(nbr, EIGRP_NEIGHBOR_DOWN);
	    }
	}
    }
}

static u_char
eigrp_hello_authentication_decode(struct stream *s, struct eigrp_tlv_hdr_type *tlv_header, struct eigrp_neighbor *nbr)
{

  struct TLV_MD5_Authentication_Type *md5;

  md5 = (struct TLV_MD5_Authentication_Type *) tlv_header;

  if(md5->auth_type == EIGRP_AUTH_TYPE_MD5)
    return eigrp_check_md5_digest(s, md5, nbr, EIGRP_AUTH_BASIC_HELLO_FLAG);
  else if (md5->auth_type == EIGRP_AUTH_TYPE_SHA256)
    return eigrp_check_sha256_digest(s, (struct TLV_SHA256_Authentication_Type *) tlv_header, nbr, EIGRP_AUTH_BASIC_HELLO_FLAG);

  return 0;
}

/**
 * @fn eigrp_sw_version_decode
 *
 * @param[in]		nbr	neighbor the ACK shoudl be sent to
 * @param[in]		param	pointer to TLV software version information
 *
 * @return void
 *
 * @par
 * Read the software version in the specified location.
 * This consists of two bytes of OS version, and two bytes of EIGRP
 * revision number.
 */
static void
eigrp_sw_version_decode (struct eigrp_neighbor *nbr,
			 struct eigrp_tlv_hdr_type *tlv)			      
{
  struct TLV_Software_Type *version = (struct TLV_Software_Type *)tlv;

  nbr->os_rel_major = version->vender_major;
  nbr->os_rel_minor = version->vender_minor;
  nbr->tlv_rel_major = version->eigrp_major;
  nbr->tlv_rel_minor = version->eigrp_minor;
  return;
}

/**
 * @fn eigrp_peer_termination_decode
 *
 * @param[in]		nbr	neighbor the ACK shoudl be sent to
 * @param[in]		tlv	pointer to TLV software version information
 *
 * @return void
 *
 * @par
 * Read the address in the TLV and match to out address. If
 * a match is found, move the sending neighbor to the down state. If
 * out address is not in the TLV, then ignore the peer termination
 */
static void
eigrp_peer_termination_decode (struct eigrp_neighbor *nbr,
			       struct eigrp_tlv_hdr_type *tlv)
{
	struct TLV_Peer_Termination_type *param = (struct TLV_Peer_Termination_type *)tlv;

	uint32_t my_ip = nbr->ei->address->u.prefix4.s_addr;
	uint32_t received_ip = param->neighbor_ip;

	if(my_ip == received_ip)
	{
		zlog_info ("Neighbor %s (%s) is down: Peer Termination received",
			   inet_ntoa (nbr->src),ifindex2ifname (nbr->ei->ifp->ifindex, VRF_DEFAULT));
		/* set neighbor to DOWN */
		nbr->state = EIGRP_NEIGHBOR_DOWN;
		/* delete neighbor */
		eigrp_nbr_delete (nbr);
	}
}

/**
 * @fn eigrp_peer_termination_encode
 *
 * @param[in,out]   s      	  packet stream TLV is stored to
 * @param[in]		nbr_addr  pointer to neighbor address for Peer Termination TLV
 *
 * @return u_int16_t    number of bytes added to packet stream
 *
 * @par
 * Function used to encode Peer Termination TLV to Hello packet.
 */
static u_int16_t
eigrp_peer_termination_encode (struct stream *s, struct in_addr *nbr_addr)
{
	u_int16_t length = EIGRP_TLV_PEER_TERMINATION_LEN;

	/* fill in type and length */
	stream_putw(s, EIGRP_TLV_PEER_TERMINATION);
	stream_putw(s, length);

	/* fill in unknown field 0x04 */
	stream_putc(s, 0x04);

	/* finally neighbor IP address */
	stream_put_ipv4(s, nbr_addr->s_addr);

	return(length);
}

/*
 * @fn eigrp_hello_receive
 *
 * @param[in]	eigrp		eigrp routing process
 * @param[in]	iph		pointer to ip header
 * @param[in]	eigrph		pointer to eigrp header
 * @param[in]	s		input ip stream
 * @param[in]	ei		eigrp interface packet arrived on
 * @param[in]	size		size of eigrp packet
 *
 * @return void
 *
 * @par
 * This is the main worker function for processing hello packets. It
 * will validate the peer associated with the src ip address of the ip
 * header, and then decode each of the general TLVs which the packet
 * may contain.
 * 
 * @usage
 * Not all TLVs are current decoder.  This is a work in progress..
 */
void
eigrp_hello_receive (struct eigrp *eigrp, struct ip *iph, struct eigrp_header *eigrph,
		     struct stream *s, struct eigrp_interface *ei, int size)
{
  struct eigrp_tlv_hdr_type *tlv_header;
  struct eigrp_neighbor *nbr;
  uint16_t	type;
  uint16_t	length;

  /* get neighbor struct */
  nbr = eigrp_nbr_get(ei, eigrph, iph);

  /* neighbor must be valid, eigrp_nbr_get creates if none existed */
  assert(nbr);
  
  if (IS_DEBUG_EIGRP_PACKET(eigrph->opcode - 1, RECV))
    zlog_debug("Processing Hello size[%u] int(%s) nbr(%s)",
	       size, ifindex2ifname(nbr->ei->ifp->ifindex, VRF_DEFAULT), 
	       inet_ntoa(nbr->src));

  size -= EIGRP_HEADER_LEN;
  if (size < 0)
    return;

  tlv_header = (struct eigrp_tlv_hdr_type *)eigrph->tlv;

  do {
    type = ntohs(tlv_header->type);
    length = ntohs(tlv_header->length);

    if ((length > 0) && (length <= size))
      {
	if (IS_DEBUG_EIGRP_PACKET(0, RECV))
	  zlog_debug("  General TLV(%s)", LOOKUP(eigrp_general_tlv_type_str, type));

	// determine what General TLV is being processed
	switch (type)
	  {
	  case EIGRP_TLV_PARAMETER:
	    eigrp_hello_parameter_decode(nbr, tlv_header);
	    break;
	  case EIGRP_TLV_AUTH:
	    {
              if(eigrp_hello_authentication_decode(s,tlv_header,nbr) == 0)
                return;
              else
                break;
              break;
	    }
	  case EIGRP_TLV_SEQ:
	    break;
	  case EIGRP_TLV_SW_VERSION:
	    eigrp_sw_version_decode(nbr, tlv_header);
	    break;
	  case EIGRP_TLV_NEXT_MCAST_SEQ:
	    break;
	  case EIGRP_TLV_PEER_TERMINATION:
	    eigrp_peer_termination_decode(nbr, tlv_header);
	    break;
	  case EIGRP_TLV_PEER_MTRLIST:
	  case EIGRP_TLV_PEER_TIDLIST:
	    break;
	  default:
	    break;
	  }
    }

    tlv_header = (struct eigrp_tlv_hdr_type *)(((char *)tlv_header) + length);
    size -= length;

  } while (size > 0);


  /*If received packet is hello with Parameter TLV*/
  if (ntohl(eigrph->ack) == 0)
    {
      /* increment statistics. */
      ei->hello_in++;
      eigrp_nbr_state_update(nbr);

    }

  if (IS_DEBUG_EIGRP_PACKET(0, RECV))
      zlog_debug("Hello Packet received from %s", inet_ntoa(nbr->src));

}

/**
 * @fn eigrp_sw_version_encode
 *
 * @param[in,out]	s	packet stream TLV is stored to
 *
 * @return u_int16_t	number of bytes added to packet stream
 *
 * @par
 * Store the software version in the specified location.
 * This consists of two bytes of OS version, and two bytes of EIGRP
 * revision number.
 */
static u_int16_t
eigrp_sw_version_encode (struct stream *s)
{
  u_int16_t length = EIGRP_TLV_SW_VERSION_LEN;

  // setup the tlv fields
  stream_putw(s, EIGRP_TLV_SW_VERSION);
  stream_putw(s, length);

  // encode the version of quagga we're running
  // DVS: need to figure out a cleaner way to do this
  stream_putc(s, 0);		//!< major os version
  stream_putc(s, 99);		//!< minor os version

  /* and the core eigrp version */
  stream_putc(s, EIGRP_MAJOR_VERSION);
  stream_putc(s, EIGRP_MINOR_VERSION);

  return(length);
}

/**
 * @fn eigrp_tidlist_encode
 *
 * @param[in,out]	s	packet stream TLV is stored to
 *
 * @return void
 *
 * @par
 * If doing mutli-topology, then store the supported TID list.
 * This is currently a place holder function
 */
static u_int16_t
eigrp_tidlist_encode (struct stream *s)
{
  //u_int16_t length = EIGRP_TLV_SW_VERSION_LEN;
  return 0;
}

/**
 * @fn eigrp_sequence_encode
 *
 * @param[in,out]       s       packet stream TLV is stored to
 *
 * @return u_int16_t    number of bytes added to packet stream
 *
 * @par
 * Part of conditional receive process
 *
 */
static u_int16_t
eigrp_sequence_encode (struct stream *s)
{
  u_int16_t length = EIGRP_TLV_SEQ_BASE_LEN;
  struct eigrp *eigrp;
  struct eigrp_interface *ei;
  struct listnode *node, *node2, *nnode2;
  struct eigrp_neighbor *nbr;
  size_t backup_end, size_end;
  int found;

  eigrp = eigrp_lookup ();
  if (eigrp == NULL)
    {
      return 0;
    }

  // add in the parameters TLV
  backup_end = stream_get_endp(s);
  stream_putw(s, EIGRP_TLV_SEQ);
  size_end = s->endp;
  stream_putw(s, 0x0000);
  stream_putc(s, IPV4_MAX_BYTELEN);

  found = 0;
  for (ALL_LIST_ELEMENTS_RO (eigrp->eiflist, node, ei))
    {
      for (ALL_LIST_ELEMENTS (ei->nbrs, node2, nnode2, nbr))
        {
          if(nbr->multicast_queue->count > 0)
            {
              length += (u_int16_t) stream_put_ipv4(s,nbr->src.s_addr);
              found = 1;
            }
        }
    }

  if(found == 0)
    {
      stream_set_endp(s,backup_end);
      return 0;
    }

  backup_end = stream_get_endp (s);
  stream_set_endp (s,size_end);
  stream_putw (s, length);
  stream_set_endp (s, backup_end);

  return length;
}

/**
 * @fn eigrp_sequence_encode
 *
 * @param[in,out]       s       packet stream TLV is stored to
 *
 * @return u_int16_t    number of bytes added to packet stream
 *
 * @par
 * Part of conditional receive process
 *
 */
static u_int16_t
eigrp_next_sequence_encode (struct stream *s)
{
  u_int16_t length = EIGRP_NEXT_SEQUENCE_TLV_SIZE;
  struct eigrp *eigrp;

  eigrp = eigrp_lookup ();
  if (eigrp == NULL)
    {
      return 0;
    }

  // add in the parameters TLV
    stream_putw(s, EIGRP_TLV_NEXT_MCAST_SEQ);
    stream_putw(s, EIGRP_NEXT_SEQUENCE_TLV_SIZE);
    stream_putl(s,eigrp->sequence_number+1);

  return length;
}

/**
 * @fn eigrp_hello_parameter_encode
 *
 * @param[in]		ei	pointer to interface hello packet came in on
 * @param[in,out]	s	packet stream TLV is stored to
 *
 * @return u_int16_t	number of bytes added to packet stream
 *
 * @par
 * Encode Parameter TLV, used to convey metric weights and the hold time.
 *
 * @usage
 * Note the addition of K6 for the new extended metrics, and does not apply to
 * older TLV packet formats.
 */
static u_int16_t
eigrp_hello_parameter_encode (struct eigrp_interface *ei, struct stream *s, u_char flags)
{
    u_int16_t length = EIGRP_TLV_PARAMETER_LEN;

  // add in the parameters TLV
  stream_putw(s, EIGRP_TLV_PARAMETER);
  stream_putw(s, EIGRP_TLV_PARAMETER_LEN);

  //if graceful shutdown is needed to be announced, send all 255 in K values
  if(flags & EIGRP_HELLO_GRACEFUL_SHUTDOWN)
    {
      stream_putc(s, 0xff); /* K1 */
      stream_putc(s, 0xff); /* K2 */
      stream_putc(s, 0xff); /* K3 */
      stream_putc(s, 0xff); /* K4 */
      stream_putc(s, 0xff); /* K5 */
      stream_putc(s, 0xff); /* K6 */
    }
  else // set k values
    {
      stream_putc(s, ei->eigrp->k_values[0]); /* K1 */
      stream_putc(s, ei->eigrp->k_values[1]); /* K2 */
      stream_putc(s, ei->eigrp->k_values[2]); /* K3 */
      stream_putc(s, ei->eigrp->k_values[3]); /* K4 */
      stream_putc(s, ei->eigrp->k_values[4]); /* K5 */
      stream_putc(s, ei->eigrp->k_values[5]); /* K6 */
    }

  // and set hold time value..
  stream_putw(s, IF_DEF_PARAMS(ei->ifp)->v_wait);

  return length;
}

/**
 * @fn eigrp_hello_encode
 *
 * @param[in]		ei	pointer to interface hello packet came in on
 * @param[in]		s	packet stream TLV is stored to
 * @param[in]		ack	 if non-zero, neigbors sequence packet to ack
 * @param[in]		flags  type of hello packet
 * @param[in]		nbr_addr  pointer to neighbor address for Peer Termination TLV
 *
 * @return eigrp_packet		pointer initialize hello packet
 *
 * @par
 * Allocate an EIGRP hello packet, and add in the the approperate TLVs
 *
 */
static struct eigrp_packet *
eigrp_hello_encode (struct eigrp_interface *ei, in_addr_t addr, u_int32_t ack, u_char flags, struct in_addr *nbr_addr)
{
  struct eigrp_packet *ep;
  u_int16_t length = EIGRP_HEADER_LEN;

  // allocate a new packet to be sent
  ep = eigrp_packet_new(ei->ifp->mtu);

  if (ep)
    {
      // encode common header feilds
      eigrp_packet_header_init(EIGRP_OPC_HELLO, ei, ep->s, 0, 0, ack);

      // encode Authentication TLV
      if((IF_DEF_PARAMS (ei->ifp)->auth_type == EIGRP_AUTH_TYPE_MD5) && (IF_DEF_PARAMS (ei->ifp)->auth_keychain != NULL))
        {
          length += eigrp_add_authTLV_MD5_to_stream(ep->s,ei);
        }
      else if((IF_DEF_PARAMS (ei->ifp)->auth_type == EIGRP_AUTH_TYPE_SHA256) && (IF_DEF_PARAMS (ei->ifp)->auth_keychain != NULL))
        {
          length += eigrp_add_authTLV_SHA256_to_stream(ep->s,ei);
        }

      /* encode appropriate parameters to Hello packet */
      if(flags & EIGRP_HELLO_GRACEFUL_SHUTDOWN)
        length += eigrp_hello_parameter_encode(ei, ep->s, EIGRP_HELLO_GRACEFUL_SHUTDOWN);
      else
        length += eigrp_hello_parameter_encode(ei, ep->s, EIGRP_HELLO_NORMAL);

      // figure out the version of code we're running
      length += eigrp_sw_version_encode(ep->s);

      if(flags & EIGRP_HELLO_ADD_SEQUENCE)
        {
          length += eigrp_sequence_encode(ep->s);
          length += eigrp_next_sequence_encode(ep->s);
        }

      // add in the TID list if doing multi-topology
      length += eigrp_tidlist_encode(ep->s);

      /* encode Peer Termination TLV if needed */
      if(flags & EIGRP_HELLO_GRACEFUL_SHUTDOWN_NBR)
    	  length += eigrp_peer_termination_encode(ep->s, nbr_addr);

      // Set packet length
      ep->length = length;

      // set soruce address for the hello packet
      ep->dst.s_addr = addr;

      if((IF_DEF_PARAMS (ei->ifp)->auth_type == EIGRP_AUTH_TYPE_MD5) && (IF_DEF_PARAMS (ei->ifp)->auth_keychain != NULL))
        {
          eigrp_make_md5_digest(ei,ep->s, EIGRP_AUTH_BASIC_HELLO_FLAG);
        }
      else if((IF_DEF_PARAMS (ei->ifp)->auth_type == EIGRP_AUTH_TYPE_SHA256) && (IF_DEF_PARAMS (ei->ifp)->auth_keychain != NULL))
        {
          eigrp_make_sha256_digest(ei,ep->s, EIGRP_AUTH_BASIC_HELLO_FLAG);
        }

      // EIGRP Checksum
      eigrp_packet_checksum(ei, ep->s, length);
    }

  return(ep);
}

/**
 * @fn eigrp_hello_send
 *
 * @param[in]		nbr	neighbor the ACK should be sent to
 *
 * @return void
 *
 * @par
 *  Send (unicast) a hello packet with the destination address
 *  associated with the neighbor.  The eigrp header ACK feild will be
 *  updated to the neighbor's sequence number to acknolodge any
 *  outstanding packets
 */
void
eigrp_hello_send_ack (struct eigrp_neighbor *nbr)
{
  struct eigrp_packet *ep;

  /* if packet succesfully created, add it to the interface queue */
  ep = eigrp_hello_encode(nbr->ei, nbr->src.s_addr, nbr->recv_sequence_number, EIGRP_HELLO_NORMAL, NULL);

  if (ep)
    {
      if (IS_DEBUG_EIGRP_PACKET(0, SEND))
	zlog_debug("Queueing [Hello] Ack Seq [%u] nbr [%s]",
		   nbr->recv_sequence_number, inet_ntoa(nbr->src));

      /* Add packet to the top of the interface output queue*/
      eigrp_fifo_push_head(nbr->ei->obuf, ep);

      /* Hook thread to write packet. */
      if (nbr->ei->on_write_q == 0)
	{
	  listnode_add(nbr->ei->eigrp->oi_write_q, nbr->ei);
	  nbr->ei->on_write_q = 1;
	}
      if (nbr->ei->eigrp->t_write == NULL)
	nbr->ei->eigrp->t_write =
	  thread_add_write(master, eigrp_write, nbr->ei->eigrp, nbr->ei->eigrp->fd);
    }
}

/**
 * @fn eigrp_hello_send
 *
 * @param[in]		ei	pointer to interface hello should be sent
 * @param[in]		flags type of hello packet
 * @param[in]		nbr_addr  pointer to neighbor address for Peer Termination TLV
 *
 * @return void
 *
 * @par
 * Build and enqueue a generic (multicast) periodic hello packet for
 * sending.  If no packets are currently queues, the packet will be
 * sent immadiatly
 */
void
eigrp_hello_send (struct eigrp_interface *ei, u_char flags, struct in_addr *nbr_addr)
{
  struct eigrp_packet *ep = NULL;

  /* If this is passive interface, do not send EIGRP Hello.
  if ((EIGRP_IF_PASSIVE_STATUS (ei) == EIGRP_IF_PASSIVE) ||
      (ei->type != EIGRP_IFTYPE_NBMA))
    return;
  */

  if (IS_DEBUG_EIGRP_PACKET(0, SEND))
    zlog_debug("Queueing [Hello] Interface(%s)", IF_NAME(ei));

  /* if packet was succesfully created, then add it to the interface queue */
  ep = eigrp_hello_encode(ei, htonl(EIGRP_MULTICAST_ADDRESS), 0, flags, nbr_addr);

  if (ep)
    {
      // Add packet to the top of the interface output queue
      eigrp_fifo_push_head(ei->obuf, ep);

      /* Hook thread to write packet. */
      if (ei->on_write_q == 0)
        {
          listnode_add(ei->eigrp->oi_write_q, ei);
          ei->on_write_q = 1;
        }

      if (ei->eigrp->t_write == NULL)
        {
          if(flags & EIGRP_HELLO_GRACEFUL_SHUTDOWN)
            {
              ei->eigrp->t_write =
                  thread_execute(master, eigrp_write, ei->eigrp, ei->eigrp->fd);
            }
          else
            {
              ei->eigrp->t_write =
                thread_add_write(master, eigrp_write, ei->eigrp, ei->eigrp->fd);
            }
	}
    }
}