[distcc] distcc only listens on v6 with --enable-rfc2553?

Jeff Rizzo riz+distcc at boogers.sf.ca.us
Wed May 12 15:31:20 GMT 2004

On Wed, May 12, 2004 at 05:04:47PM +1000, Martin Pool wrote:
> On 11 May 2004, Jeff Rizzo <riz+distcc at boogers.sf.ca.us> wrote:
> > > Do you actually want to mix IPv6 and IPv4 connections?  In fact, if
> > > not, why not just build without rfc2553.
> > 
> > Yes, I would like to mix the connections.  Practically speaking,
> > there's ways I could work around it, and few situations where I'd
> > need to do both at the same time, but now that I've learned I *can't*
> > do it, my contrariness is kicking in.  :)  If/when I get some patches
> > together, I'll be happy to either post them or maintain them
> > locally.
> In that case, I think you need to get ip6-mapped addresses working.
> That is the right way to have servers accept both connections over
> both protocols.  Please let me know what the BSD folks say about it.

OK, this morning, I now know a lot more about the situation.  :)

It seems that the consensus in the BSD community is that ipv4-mapped
addresses present something of a security risk:


There is a sysctl on the three major BSDs:

net.inet6.ip6.v6only = 1

... when this is "1", it disables ipv4-mapped addresses.  "1" is the default
on OpenBSD, NetBSD, and FreeBSD 5.  (FreeBSD4 had it "0").

The consensus over there seems to be that the right thing to do is
to open two sockets if you want to support both protocols.

So, for the moment, I can set v6only to 0, but I'd like to explicitly
support both in distccd... is this something you'd consider for inclusion
if I wrote the support?  If so, what do you think the best way to
enable it would be?  Via autoconf, with some --enable flag?  Checking
the sysctl value and acting accordingly?

I realize that dual-stack support isn't really high on most folks' priority
lists (hell, it probably shouldn't be as high as it is on *my* list),
but I'm willing to do the work if it will eventually get included...


Jeff Rizzo                                         http://boogers.sf.ca.us/~riz

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