Supporting Multicast in Network driver

[freebsd nettest]

Hi,
   
  I would like to support MULTICAST in my network driver. I have define a function set_multi which will extract the Ethernet multicast address and update the corresponding hardware register. This function is called in the SIOCADDMULTI and SIOCDELMULTI ioctl case. 
   
  I used following user level program to test the multicast functionality of the driver. When I run the user level program, I could see that the control comes to SIOCADDMULTI ioctl and the correct Ethernet Multicast Mac address is added. After that when I try to ping the Multicast IP address from remote machine, the ping is not responding. Do I need to do any thing extra apart from update the Ethernet Multicast address?
   
    User level program:
   
  #include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <arpa/inet.h>
#include <unistd.h>
//#include <net/if.h>
#include <netinet/in.h>
//#include <sys/types.h>
#include <sys/socket.h>
  int
main(int argc, char *argv[])
{
  struct ip_mreq mreqn;
  int s;
  struct in_addr ip;
    if (argc != 3) {
    fprintf(stderr, "usage: %s <dev> <group>\n", argv[0]);
    exit(1);
  }
    if((s = socket(PF_INET, SOCK_DGRAM, 0)) < 0) {
    perror("socket");
    exit(1);
  }
    memset(&mreqn, 0, sizeof(mreqn));
  inet_aton(argv[1], &(mreqn.imr_interface));
  /* mreqn.imr_interface = ip; */
  
  if (inet_pton(AF_INET, argv[2], &mreqn.imr_multiaddr) <= 0) {
    fprintf(stderr, "%s: \"%s\" invalid group address\n", argv[0],argv[2]);
    exit(1);
  }
  if (setsockopt(s, 0, IP_ADD_MEMBERSHIP,&mreqn,sizeof mreqn) < 0) {
    perror("IP_ADD_MEMBERSHIP");
    exit(1);
  }
  printf("joined group %s on %s (pausing...)\n", argv[2], argv[1]);
fflush(stdout);
  pause();
  }

  Thanks
   


 				
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