From: Daniel Berger <djberg96@...>
Date: 2007-07-19T07:16:02+09:00
Subject: Re: Listing all IP addresses on an multihomed system



On Jul 18, 2:10 pm, s...@signature.invalid (Douglas Wells) wrote:
> In article <1184772029.010310.165...@j4g2000prf.googlegroups.com>,
>   Daniel Berger <djber...@gmail.com> writes:
>
> > I'm wondering if there's a way to list all IP addresses on a
> > multihomed system using Ruby's Socket API. I actually want this for
> > the sys-host library (athttp://www.rubyforge.org/projects/sysutils).
> > It's C, but I figure I can reverse engineer the Ruby code back to C.
>
> > [ extraneous program based on gethostbyname elided]
>
> > But, at least one user has reported that he has eth0 configured with a
> > LAN IP and eth1 that has 5 attached IP addresses. The above code
> > doesn't pick them up.
>
> As your user has reported, your C-based program does not do what
> you desire.  gethostbyname (and its friends) can only deal with
> DNS-based information.  Information about multi-hosting is not
> stored in the DNS. In fact, it is actually system dependent and is
> only stored in the local kernel's network tables.
>
> Most UNIX and Linux systems provide a mechanism to access this
> information via some variant of the ioctl(2) call with command
> SIOCGIFCONF.  BSDi and FreeBSD have a set of subroutines (originally
> based on the ioctl) called getifaddrs.  MS Windows WinSock2 uses
> the command SIO_GET_INTERFACE_LIST with the WSAIoctl procedure.
> You will need to look in the documentation for your system (and
> probably do a net search for programming examples) to see how it
> works.

<snip>

Indeed, there's an example in Stevens' "Unix Network Programming, Vol.
1" staring at me now. :) Many thanks for the lead. I should be ok from
here (I hope).

I'll see if I can come up with a pure Ruby solution and post it here
eventually.

Regards,

Dan