mcast.c

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/* mcast.c -- multicast socket setup routines
 *  
 * This file is part of 'netcast' program, released under BSD License. 
 * (c) 2001-2002 Stanis砤w Pa秌o <[e-mail]>. All rights reserved.   
 */

#include <fcntl.h>
#include <net/if.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>

#include "mdist.h"
#include "mcast.h"
#include "util.h"

//! const -- reuse sockets ?
int msock_reuse = 1;
//! const -- loop mcast packets ?
u_char msock_loop = MCAST_LOOP;
//! const -- multicast hop limit
u_char msock_ttl = MCAST_TTL; 


/*! gs - packed group address. (Uses port and addr fields) !*/
int init_mcast_socket(struct sockaddr_in *gs) {
  struct ip_mreq mreq;                            /* multicast request */
  int ms;                                         /* multicast socket */
  struct sockaddr_in sin;                         /* address for bind */
  u_short msock_port;                             /* port. taken from gs */
  
  msock_port=ntohs(gs->sin_port);
  sin = make_addr(0,msock_port);  
  
  if ((ms = socket(PF_INET, SOCK_DGRAM, 0)) < 0)
    crit("socket() failed, error allocating multicast socket");

  if (setsockopt(ms,SOL_SOCKET,SO_REUSEADDR,&msock_reuse,sizeof(msock_reuse)) < 0)
    MSG(2,"setsockopt() failed, can't set reuse flag");
 
  if ( bind(ms, (struct sockaddr*) &sin, sizeof(sin)) < 0)
    crit("bind() error, can't bind mcast socket");
  
  if (setsockopt(ms,IPPROTO_IP,IP_MULTICAST_TTL,&msock_ttl,sizeof(msock_ttl)) < 0)
    MSG(2,"setsockopt() failed, can't set ttl value");

  if (setsockopt(ms,IPPROTO_IP,IP_MULTICAST_LOOP,&msock_loop,sizeof(msock_loop)) < 0)
    MSG(2,"setsockopt() failed, can't set multicast packet looping");

  mreq.imr_interface.s_addr = INADDR_ANY;
  mreq.imr_multiaddr = gs->sin_addr;

  MSG(4,"Using multicast address: %s:%d",inet_ntoa(mreq.imr_multiaddr),msock_port);
  
  if (setsockopt(ms,IPPROTO_IP,IP_ADD_MEMBERSHIP,&mreq,sizeof(mreq)) < 0)
    crit("setsockopt() failed, can't join multicast group");
     
  return ms;
}