Comment author: administrator

On 4.4BSD, In order to use IP Multicasting, the SO_REUSEPORT must be
given as a parameter to setsockopt. On other Unixes and Linux,
SO_REUSEADDR is good enough. Ocaml 3.08 supports calling
SO_REUSEADDR but not SO_REUSEPORT.

Well, SO_REUSEPORT is a BSD-ism that isn't present everywhere. It is
not in the Single Unix Specification, in particular, and that's the
spec we try to stick to in the OCaml Unix library.

Also, http://www.unixguide.net/network/socketfaq/4.11.shtml quotes
Richard Stevens (someone I tend to listen to) as writing:

But when binding a multicast address (its main use), SO_REUSEADDR is
considered identical to SO_REUSEPORT (p. 731, "TCP/IP Illustrated,
Volume 2"). So for portability of multicasting applications I always
use SO_REUSEADDR.

So, there might be something non-standard in MacOS X about this.

Regards,

• Xavier Leroy

Comment author: administrator

BSDism, not standard enough? XL, 2005-03-08

Comment author: administrator

Hello Xavier, thanks for the response.

You're right that it is a BSDism, though I don't believe that Darwin
has any plans to change this. Thus, IP multicast with OCaml is broken
for that platform. I have seen that Ruby and Perl have added this
socket option, as have I for my source-compiled OCaml build. Can you
think of an alternative way to set this option without explicitly
including it in the socket option list?

Thanks,

-Alon.

On Mar 8, 2005, at 12:40, Xavier Leroy wrote:

On 4.4BSD, In order to use IP Multicasting, the SO_REUSEPORT must be
given as a parameter to setsockopt. On other Unixes and Linux,
SO_REUSEADDR is good enough. Ocaml 3.08 supports calling
SO_REUSEADDR but not SO_REUSEPORT.

Well, SO_REUSEPORT is a BSD-ism that isn't present everywhere. It is
not in the Single Unix Specification, in particular, and that's the
spec we try to stick to in the OCaml Unix library.

Also, http://www.unixguide.net/network/socketfaq/4.11.shtml quotes
Richard Stevens (someone I tend to listen to) as writing:

But when binding a multicast address (its main use), SO_REUSEADDR is
considered identical to SO_REUSEPORT (p. 731, "TCP/IP Illustrated,
Volume 2"). So for portability of multicasting applications I always
use SO_REUSEADDR.

So, there might be something non-standard in MacOS X about this.

Regards,

• Xavier Leroy

Comment author: @mshinwell

It sounds like SO_REUSEPORT has become more widespread now (2016) so we might consider adding this.

Comment author: @xavierleroy

Stevens must be spinning in his grave... A pull request on Github implementing this feature would be welcome.

This issue has been open one year with no activity. Consequently, it is being marked with the "stale" label. What this means is that the issue will be automatically closed in 30 days unless more comments are added or the "stale" label is removed. Comments that provide new information on the issue are especially welcome: is it still reproducible? did it appear in other contexts? how critical is it? etc.

I'm willing to admit that SO_REUSEPORT is more widely available now, with slightly different semantics from SO_REUSEADDR (https://lwn.net/Articles/542629/). A pull request, please?