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Re: doc getsockopt, setsockopt

From: Kevin Ryde
Subject: Re: doc getsockopt, setsockopt
Date: Sat, 01 Oct 2005 09:06:56 +1000
User-agent: Gnus/5.110004 (No Gnus v0.4) Emacs/21.4 (gnu/linux)

Greg Troxel <address@hidden> writes:
> NetBSD does not define SOL_IP.  SOL_SOCKET is 0xffff.  So from the
> NetBSD point of view, the right thing to do is define
> IPPROTO_{IP,UDP,TCP} as (constant) variables.

The posix spec at
gives IPPROTO_TCP as an example, so yep, I'll remove the SOL bits in
favour of IPPROTO.

I'd noticed in the past the gnu/linux "man 5 protocols" says to use
/etc/protocols instead of numbers like IPPROTO, but what posix says
must trump that.

> NetBSD's Linux compatibility code indicates that SOL_IP is 0, but has
> a comment that these values can vary by architecture

That should be ok, we don't care about the actual values as long as
the constants are right.

> It would be interesting to hear what variables the Linux kernel
> actually compares to - IPPROTO_IP or SOL_IP.

Oh, well, there should be a better spec for the programming interface
than digging around the sources :-).

> 'man 7 ip' is Linux specific (it's ip(4) on BSD).  Perhaps "Consult
> operating system documentation for these calls".

Thanks, I'll put "man ip" (there should be only one).

> MULTIADDR is the multicast group to be joined or left, and
> INTERFACEADDR is an IP adddress by which an interface will be found to
> perform the join/leave operation.  INTERFACEADDR may be INADDR_ANY in
> which case the default interface will be used. These values are simply
> passed to the underlying system call, so extensions on some systems to
> specify interface by ifindex may be available.

Sounds fair.

> Or skip the last sentence, or the second half of it.  People who
> understand specifying interfaces by ifindex will hopefully realize the
> portability issues of that.

Do you need to know about host vs network byte order to get it
through?  That would be something to note.

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