netdev - RE: Getting the IPv6 'prefix_len' for DHCP6 assigned addresses.

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Message-ID: <b3d1e478fb02420ab6414e889fd10259@AcuMS.aculab.com>
Date:   Thu, 3 Feb 2022 18:37:18 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Dan Williams' <dcbw@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     David Ahern <dsahern@...nel.org>
Subject: RE: Getting the IPv6 'prefix_len' for DHCP6 assigned addresses.

From: Dan Williams
> Sent: 03 February 2022 14:52
> > > On Wed, 2022-02-02 at 16:58 +0000, David Laight wrote:
> > > > I'm trying to work out how DHCP6 is supposed to work.
> > > >
> > > > I've a test network with the ISC dhcp6 server and radvd running.
> > > > If I enable 'autoconf' I get a nice address with the prefix from
> > > > radvd and the last 8 bytes from my mac address, prefix_len 64.
> > > > I get a nice address from dhcp6 (busybox udhcpc6) with the same
> > > > prefix.

Today it was working.
Not sure what was going on last time I tried.

But I do have to look very hard to find the IPv6 routes.
Running:
   ip route show table all
does give them, but nothing else seems to.

The busybox netstat doesn't grok -6.
But I've the full version of 'ip' to get namespace support.

Talking of namespaces, is it possible to mount the namespace
version of /proc/sys/net somewhere in the filesystem?
I've got programs that really want to open nodes in the
'init' namespace and a named one.

I can use:
	ip netns exec namespace program 3</proc/sys/net and
then use openat(3, "path") to get items in the 'init' namespace.
But it is a bit horrid.

	David

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