Has anyone tried IP multicast with RTEMS?

Joel Sherrill joel.sherrill at OARcorp.com
Tue Oct 21 12:52:51 UTC 2003


Could you produce this information as a patch to some
section of the Networking Guide?

Also someone posted a snippet of code to get the
IP address of an interface.  Could whoever did that
please turn it into a patch against the networking

It would be nice to get this type of information
into a manual so it isn't necessary to recreate it. :)



Thomas Rauscher wrote:

>>-----Original Message-----
>>From: Phil Torre [mailto:ptorre at zetron.com]
>>Sent: Monday, October 20, 2003 8:16 PM
>>To: RTEMS User List
>>Subject: Has anyone tried IP multicast with RTEMS?
>>Greetings All,
>>Can anyone report success with RTEMS and multicast?  From what I can
>>tell by looking through the source, it looks like the FreeBSD stack
>>is multicast-capable, but I may have some work to do in the Ethernet
>>device driver (for MPC860, as used in the eth_comm BSP).
>>I haven't done any experiments yet, but we will want to be doing
>>multicast in future product development, so I'm just looking ahead.
> Multicasting works. Basically, two things are important:
> 1) Ethernet layer:
>    The driver must support ethernet multicasting. That is, it must
>    configure its ethernet multicast list/hash table when
>    a socket joins a multicast group.
>    This is done in the driver's ioctl. Required commands
>    There is a macro ETHER_MAP_IP_MULTICAST to map IP addresses
>    and ethernet multicast addresses. 
> 2) IP layer:
>    Sending works immediately by just using an IP multicast address.
>    Receiving requires to add the node to an IP multicast group
>    (so that IP/Ethernet multicasting is configured properly).
>    This is done like in the code snippet below.
>     #include <sys/socket.h>                                                         
>     #include <sys/sockio.h>                                                         
>     #include <net/if.h>                                                             
>     #include <netinet/in.h>                                                         
>     #include <netinet/if_ether.h>                                                   
>     struct ip_mreq mreq;        
>     int            fd;                                                  
>     mreq.imr_multiaddr.s_addr=inet_addr(HELLO_GROUP);                           
>     mreq.imr_interface.s_addr=htonl(INADDR_ANY);                                
>     if (setsockopt(fd,IPPROTO_IP,IP_ADD_MEMBERSHIP,&mreq,sizeof(mreq)) < 0) {
>       perror("setsockopt");                                                     
>       exit(1);                                                                  
>     }                                                                           
> Best regards,
> Thomas
> --
> Dipl.-Ing. Thomas Rauscher                 Tel.:   ++43 1 402 08 05 15
>                                            Fax:    ++43 1 402 08 05 99
> LOYTEC electronics GmbH                    E-mail: trauscher at loytec.com
> Stolzenthalergasse 24/3, A-1080 Wien       Web:    http://www.loytec.com

Joel Sherrill, Ph.D.             Director of Research & Development
joel at OARcorp.com                 On-Line Applications Research
Ask me about RTEMS: a free RTOS  Huntsville AL 35805
Support Available                (256) 722-9985

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