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