All things related to multicast

[Alan Crosswell <>]

Does anyone have a working example of doing an (S,G) join on Linux 2.6?  I'm 
trying this and getting the always-helpful "Invalid argument" error.  Before I 
add printf's to the kernel I thought I'd ask....  Is there a better list to ask 
this on?

The following code snippet is derived from rtpqual.c:

int openSSM(source, name, port)
char *source;
char *name;
int port;
{
  struct group_source_req greq;
  struct sockaddr_in sin;
  struct hostent *hp;
  int fd, one=1;

  bzero(&greq, sizeof(struct group_source_req));
  bzero(&sin, sizeof(struct sockaddr_in));

  greq.gsr_interface = 1;       /* default intf XXXX */

  if (isdigit(*name)) {
    sin.sin_addr.s_addr = inet_addr(name);
  }
  else if (hp = gethostbyname(name)) {
    bcopy(hp->h_addr, (char *)&sin.sin_addr.s_addr, hp->h_length);
  }
  else {
    printf("I Don't understand session name %s\n",name);
    exit(1);
  }
  sin.sin_family = AF_INET;
  sin.sin_port = port;

  if (!IN_MULTICAST(ntohl(sin.sin_addr.s_addr))) {
    printf("%s is not a multicast session\n", name);
    exit(1);
  }
  greq.gsr_group.sin_addr.s_addr = sin.sin_addr.s_addr;
  //  greq.gsr_interface.s_addr = INADDR_ANY;
  if (isdigit(*source)) {
    greq.gsr_source.sin_addr.s_addr = inet_addr(source);
  }
  else if (hp = gethostbyname(source)) {
    bcopy(hp->h_addr, (char *)&greq.gsr_source.sin_addr.s_addr, hp->h_length);
  }
  else {
    printf("I Don't understand source name %s\n",source);
    exit(1);
  }

  NOERROR(fd = socket(AF_INET, SOCK_DGRAM, 0), "socket");
  NOERROR(setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one)),
          "SO_REUSEADDR");

  if (bind(fd, &sin, sizeof(sin)) == -1) {
    perror("Warning - Using INADDR_ANY because");
    sin.sin_addr.s_addr = INADDR_ANY;
    NOERROR(bind(fd, &sin, sizeof(sin)), "bind");
  }

  NOERROR(setsockopt(fd, IPPROTO_IP, MCAST_JOIN_SOURCE_GROUP, &greq, 
sizeof(greq)),
          "MCAST_JOIN_SOURCE_GROUP");

  return(fd);
}