[boost] [asio] Multicast join group does not honor interface specificatoin

Subject: [boost] [asio] Multicast join group does not honor interface specificatoin
From: Dale Wilson (wilsond_at_[hidden])
Date: 2009-07-01 16:51:24

I'm working with the Multicast receiver example at:

http://www.boost.org/doc/libs/1_35_0/doc/html/boost_asio/example/multicast/receiver.cpp

Notice that you specify the listen_address as you create the endpoint 
that is bound to the socket. Later when you call socket::set_option with 
the multicast_address, I would expect the listen_address to be honored. 
The current implementation uses INET_ANY for the interface in the 
multicast subscription.   This means the multicast messages may arrive 
on one interface while you are listening for them on another one.  I 
can't think of any case in which you would want to specify an IP for the 
receive, but not for the join_group.

Workaround: There is a different constructor for the join_group object 
that does produce the desired behavior, but it is not obvious that you 
should need it.  Also it does not accept boost::asio::ip::addresses as 
arguments (which would make sense) but requires that you "convert" them 
to ip4 (or ip6) addresses.   Seems awkward.

Dale