Re: [OMPI devel] IPv6 support in OpenMPI?

[Ralph Castain]

Hi folks Sorry to be coming late to the discussion - I'm on travel, so my comments will likely have long time delays in them. Only one contribution I would like to make. You are welcome to do whatever you like (subject to the usual approval procedure) in the MPI layer (the btl's for example) - my comments only apply to the OpenRTE layer (specifically, the oob tcp component). >From the run-time perspective, whatever you do *must* support heterogeneous networks of computers that may and may not support IPv6, and may and may not support IPv6-mapped IPv4 addresses. In other words, the solution must support systems including computers that only know IPv4. I know this may make things more difficult, but OpenRTE has additional requirements on it for other applications as well. We cannot lock ourselves into IPv6-supported systems. Thanks Ralph Christian Kauhaus wrote: Adrian Knoth <a...@drcomp.erfurt.thur.de>: (I really prefer the v6-mapped-v4 solution with a single socket, thus eliminating this problem) One little problem here is that it is possible to disable the IPv6-mapped IPv4 addresses at least under Linux and some BSD variants. For Linux, have a look at sys.net.ipv6.bindv6only. Some authors even recommend to do so for security considerations (for example, Murphy & Malone in IPv6 Network Administration, O'Reilly 2005). So the approach that maximizes the environments where it works out of the box is this: Call getaddrinfo with PF_UNSPEC and open a socket for each IP version it returns (usually this means two sockets on IPv6-enabled hosts, but this may change in the future... who knows?) If the connection handling code already makes use of one big select loop, this should not be *too* hard... Christian