All things related to multicast

[Hoerdt Mickael <>]

Hi Alan,

You shouln't bind your socket before joining the SSM channel I think, 
try to bind it after or better,
try to bind it outside of the openSSM function : joining an SSM channel 
is an IP operation, which
is not related to socket binding (ususally related to transport operation).

Also, do not forget that the group_source_req structure is the following :

struct group_source_req
{
       __u32                   gsr_interface;  /* interface index */
       struct sockaddr_storage gsr_group;      /* group address */
       struct sockaddr_storage gsr_source;     /* source address */
};

Which means that gsr_group and gsr_source are address family independant 
(IPv4/IPv6). Usually
the best way to use it is to have a sockaddr_in * and a sockaddr_in6 *, 
both pointing to the
same sockaddr_storage structure and to fill the required fields : 
sin4/6_family and sin4/6_add
and sin4/6_len (not under linux). gsr_interface is an integer 
corresponding to the whished interface
index.

<marketing>
For an excellent documentation (including multicast) see Richard Stevens 
TCP/IP Networking book,
also for a quick SSM test prog you can take a look at  Source Specific 
Multicast Source Discovery Protocol implementation which offers an open 
source SSM test prog called test_msf (test multicast
socket filter) in src/examples, this program rely on the libmcast 
library. I used Richard stevens
book to write this library 
=>http://clarinet.u-strasbg.fr/~hoerdt/libssmsdp/
</marketing>

Cheers,

Hoerdt Mickael

Alan Crosswell a écrit :

> 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);
> }