Re: [lwip-devel] Does multicast setsockopt() support IP_MULTICAST_LOOP?

[Frédéric BERNON]

Got IP_MULTICAST_LOOP defined in sockets.h is just to have a source code 
compatibility. This is not only this option, some others are used like this. 
EAFNOSUPPORT return value can be used to know at run-time if the option is 
really supported. Of course, in all cases, if your application MUST HAVE 
this option, you have a problem, and you need to implement this option. I'm 
not sure this option will be implement in the near future...

Just a sample of MSDN documentation about the difference between Winsock & 
Unix for this option:

Note  The Winsock version of the IP_MULTICAST_LOOP option is semantically 
different than the UNIX version of the IP_MULTICAST_LOOP option:
 a.. In Winsock, the IP_MULTICAST_LOOP option applies only to the receive 
path.
 b.. In the UNIX version, the IP_MULTICAST_LOOP option applies to the send 
path.
For example, applications ON and OFF (which are easier to track than X and 
Y) join the same group on the same interface; application ON sets the 
IP_MULTICAST_LOOP option on, application OFF sets the IP_MULTICAST_LOOP 
option off. If ON and OFF are Winsock applications, OFF can send to ON, but 
ON cannot sent to OFF. In contrast, if ON and OFF are UNIX applications, ON 
can send to OFF, but OFF cannot send to ON.


----- Original Message ----- 
From: "Chu, Zhenwei" <address@hidden>
To: "lwip-devel" <address@hidden>
Sent: Monday, September 15, 2008 9:12 PM
Subject: [lwip-devel] Does multicast setsockopt() support IP_MULTICAST_LOOP?


> Hi,
>
> IP_MULTICAST_LOOP is defined in sockets.h line 172
> #define IP_MULTICAST_LOOP  7
>
> But when I call setsockopt() with IP_MULTICAST_LOOP, it always returns 
> failure. After step into setsockopt(), I found IP_MULTICAST_LOOP is not 
> implemented. Will IP_MULTICAST_LOOP be supported in the near future? Or 
> shall IP_MULTICAST_LOOP be undefined? So user will not be mislead.
>
> Thanks
>
> Zhenwei Chu


--------------------------------------------------------------------------------


> _______________________________________________
> lwip-devel mailing list
> address@hidden
> http://lists.nongnu.org/mailman/listinfo/lwip-devel