From: Daniel Berger <djberg96@...>
Date: 2007-07-19T02:13:00+09:00
Subject: Re: Listing all IP addresses on an multihomed system

On 7/18/07, Francis Cianfrocca <garbagecat10@gmail.com> wrote:
> On 7/18/07, Daniel Berger <djberg96@gmail.com> wrote:
> >
> > Hi all,
> >
> > 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 (at http://www.rubyforge.org/projects/sysutils).
> > It's C, but I figure I can reverse engineer the Ruby code back to C.
> >
> > Here's the equivalent of what I'm currently doing (in C):
> >
> > #include <unistd.h>
> > #include <netdb.h>
> > #include <stdio.h>
> > #include <arpa/inet.h>
> >
> > #define BUF 256
> >
> > int main(){
> >    struct hostent* h;
> >    char hostname[BUF];
> >    char ip[BUF];
> >
> >    if(gethostname(hostname, BUF) != 0){
> >       printf("gethostbyname failed\n");
> >       return -1;
> >    }
> >
> >    printf("Hostname: %s\n", hostname);
> >
> >    h = gethostbyname(hostname);
> >
> >    if(!h){
> >       printf("gethostbyname failed\n");
> >       return -1;
> >    }
> >
> >    while(*h->h_addr_list){
> >       printf("Addr: %s\n", inet_ntop(h->h_addrtype, *h->h_addr_list,
> > ip, BUF));
> >       *h->h_addr_list++;
> >    }
> >
> >    return 0;
> > }
> >
> > 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.
> >
> > Is there a pure Ruby solution? Is it just a matter of
> > Socket.getaddrinfo(Socket.gethostname, 80)? Or, does anyone happen to
> > know the C solution?
> >
> > Thanks,
> >
> > Dan
> >
> >
> >
>
> Since you're obviously using Linux, how about just parsing the output of
> ethtool?
>

Eh? No, the C code above works just fine on Solaris (with -lsocket and
-lnsl added). Besides, I need the code to be as cross platform as
possible (for Unix flavors, that is - I use a different approach on MS
Windows). So, parsing system calls is out of the question.

Regards,

Dan