On 09/05/2013 21:49, Brian Call wrote:
Hi Guys,
My name is Brian Call and I'm a software developer for Sotera
Wireless. I'm currently developing a relatively complex multicast
application using the jdk7 selector-based I/O for multicast and I've
run in to a pretty major hurdle. By "complex", I mean that I have a
single bound socket joining multiple groups and it's critical that the
bound socket only receive traffic for groups it has joined. I'm
hitting the "promiscuous" traffic problem... and while bound to
0.0.0.0 on linux I'm getting traffic for all multicast groups, even if
they were not specifically joined. In essence, there is no IP
stack-level filtering for datagrams by joined group on linux unless
you explicitly tell the stack to do so. Solaris and windows does the
filtering by default and Linux does not.
Is there any way to make use of a non-standard socket option in Java?
Having spoken with Neil Horman lead networking developer over at Red
Hat, he mentioned that by passing in the socket option
IP_MULTICAST_ALL with a value of '0' it will disable UDP multiplexing
on Linux when bound to the wildcard address. This would definitely be
the hot move...
If you have any insight into resolving the promiscuous multicast
traffic problem in Java, I'd be more than grateful.
Thanks for you mail. I wasn't aware of IP_MULTICAST_ALL, this is very
useful to know because multicasting behavior on Linux has been painful
because of works differently to other platforms (particularly Solaris,
Mac and Windows). It may be that we need to consider setting
IP_MULTICAST_ALL to 0 by default.
As regards platform specific socket options then it is possible for a
JDK implementation to expose socket options beyond those specified. This
is the rational for the NetworkChannel setOption/getOption methods. This
isn't exactly what you want though, it's not a means to "bolt on"
support for other socket options to an existing JDK build.
-Alan
