[PATCH 10/17] Tools: hv: Gather ipv[4,6] gateway information

KY Srinivasan kys at microsoft.com
Tue Jul 24 22:13:00 UTC 2012



> -----Original Message-----
> From: Dan Williams [mailto:dcbw at redhat.com]
> Sent: Tuesday, July 24, 2012 2:37 PM
> To: Stephen Hemminger
> Cc: Olaf Hering; KY Srinivasan; gregkh at linuxfoundation.org; linux-
> kernel at vger.kernel.org; devel at linuxdriverproject.org;
> virtualization at lists.osdl.org; apw at canonical.com; netdev at vger.kernel.org;
> ben at decadent.org.uk
> Subject: Re: [PATCH 10/17] Tools: hv: Gather ipv[4,6] gateway information
> 
> On Tue, 2012-07-24 at 09:56 -0700, Stephen Hemminger wrote:
> > On Tue, 24 Jul 2012 18:53:59 +0200
> > Olaf Hering <olaf at aepfle.de> wrote:
> >
> > > On Tue, Jul 24, Stephen Hemminger wrote:
> > >
> > > > On Tue, 24 Jul 2012 09:01:34 -0700
> > > > "K. Y. Srinivasan" <kys at microsoft.com> wrote:
> > > >
> > > > > +	memset(cmd, 0, sizeof(cmd));
> > > > > +	strcat(cmd, "/sbin/ip -f inet  route | grep -w ");
> > > > > +	strcat(cmd, if_name);
> > > > > +	strcat(cmd, " | awk '/default/ {print $3 }'");
> > > >
> > > >
> > > > Much simpler method:
> > > >
> > > > ip route show match 0/0
> > >
> > > This also has the benefit that ip is not called with absolute path, now
> > > that distros move binaries around.
> > >
> > > Olaf
> >
> > It is also not hard to do the same thing with a little function
> > using libmnl
> 
> Yeah seriously, netlink anyone?  You'll even get nicer error reporting
> that way.

While I will be the first admit that using C API is always better (in C code),
in this particular instance I am not so sure. All I am doing is retrieving information
on default gateways. If there is an error, that is ok and this won't be reported
back to the host. Using the ip command significantly simplifies the code here.

Regards,

K. Y  



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