On 30 Nov 2013 03:59, "Rich Felker" <dalias@aerifal.cx> wrote:
>
> On Fri, Nov 29, 2013 at 10:51:16PM -0500, Rich Felker wrote:
> > On Fri, Nov 29, 2013 at 10:45:26PM -0500, Strake wrote:
> > > On 29/11/2013, Rich Felker <dalias@aerifal.cx> wrote:
> > > > But that would mean complete unconditional DNS failure on systems
> > > > lacking IPv6.
> > >
> > > We could do so iff system has IPv6. Switching on whether system has
> > > IPv6 rather than whether resolv.conf has any IPv6 nameservers means
> > > * no check whether resolv.conf includes v6 server
> > > * that adding a v6 server to resolv.conf can not break DNS even on
> > > systems lacking v6
> > > which seems saner.
> >
> > OK, so how do we detect if the system "has IPv6"? I don't think it's
>
> BTW, short of an answer to this question, I think the approach I
> already suggested is rather safe. I can't imagine how an IPv6
> nameserver address would end up in resolv.conf on a system completely
> lacking IPv6 support at the kernel level.
>

I can imagine how it got there eg if you have a standard config or you
compile a new kernel and omit ipv6...