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Subject: Re: [alpine-user] Alpine Linux is second class member in an IPv6 network
From: Jakub Jirutka <jakub@jirutka.cz>
In-Reply-To: <20171019112452.GD5749@angua.1042.ch>
Date: Thu, 19 Oct 2017 13:54:42 +0200
Cc: alpine-user@lists.alpinelinux.org,
 be@bernhard-ehlers.de,
 Jean-Louis Fuchs <ganwell@fangorn.ch>
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Message-Id: <D15820EF-B45C-4C14-91A8-2C586390CF22@jirutka.cz>
References: <3FA7B5A4-16EB-416E-8C82-FFC17414D782@bernhard-ehlers.de> <20171019112452.GD5749@angua.1042.ch>
To: pavlix@pavlix.net

Hi Pavel,

since you have deep knowledge and experience with linux networking, can =
I ask you to help us with this IPv6 issue on Alpine, please?

Jakub

> On 19. Oct 2017, at 13:24, Jean-Louis Fuchs <ganwell@fangorn.ch> =
wrote:
>=20
> Hi
>=20
> There is also a problem with static IPv6 config. Something locks the
> IPv6 routing table for 30min (containing the correct routes), but
> after 30min the lock goes away, along with the routes. I worked
> around this by reseting the routing table, just after the interface is
> configured. So the script will stay for 30min and then fix the routing
> table, when the lock goes away. (Alpine 3.6)
>=20
> I haven't reported this because I didn't have time to investigate the
> cause or compare to edge. And of course the whole issue is more
> complex. The problem has also to do with the fact that although the
> default of accept_ra and autoconf are set to 0, the interface comes up
> with accept_ra and autoconf set to 1.=20
>=20
> $> cat /etc/sysctl.d/01-ipv6.conf
> net.ipv6.conf.default.accept_ra =3D 0
> net.ipv6.conf.default.autoconf =3D 0
> net.ipv6.conf.all.accept_ra =3D 0
> net.ipv6.conf.all.autoconf =3D 0
>=20
> Again I just worked around it:
>=20
> iface eth0 inet6 static
>        address X
>        netmask 64
>        gateway X
>        pre-up echo 0 > /proc/sys/net/ipv6/conf/eth0/accept_ra
>        pre-up echo 0 > /proc/sys/net/ipv6/conf/eth0/autoconf
>=20
> My guess even though the interface is set to static, some
> auto-configuration mechanism is still being started.
>=20
> Best,
>    Jean-Louis


>> On 18. Oct 2017, at 14:36, Bernhard Ehlers <be@bernhard-ehlers.de> =
wrote:
>>=20
>> Hi,
>>=20
>> I=E2=80=99m quite frustrated trying to integrate Alpine Linux in an =
IPv6 network.
>> My requirements should be pretty standard, I want to use auto
>> configuration (SLAAC) for address assignment and classless DHCPv6
>> for getting the DNS server IPs and domain name from the router.
>>=20
>> While SLAAC is working fine, DHCPv6 is a nightmare in Alpine.
>> The default DHCP client udhcpc6 is simply not ready for use.
>> They made some changes in busybox v1.27, so it might work,
>> but that=E2=80=99s available only in the edge branch. Furthermore the
>> ifup from busybox doesn=E2=80=99t support the use of DHCPv6 for IPv6.
>>=20
>> Then I tried using the ifupdown package together with dhclient.
>> The first stumbling block is, that ifupdown looks for /sbin/dhclient,
>> while it is installed in /usr/sbin/dhclient. Adding a symlink solves =
this.
>> Next is, that ifupdown calls the ip command with options, it =
doesn=E2=80=99t
>> support. So I additionally installed iproute2, that solves that.
>>=20
>> But the stateless DHCPv6 still doesn=E2=80=99t work. After some more
>> debugging (and comparing with a working Debian) I saw that
>> ifup doesn=E2=80=99t wait for a link-local address before starting =
the DHCPv6
>> client. Therefore ifup often fails. That was fixed in ifupdown v0.8,
>> but Alpine still uses 0.7. So I tagged ifupdown as outdated.
>>=20
>> At that point I gave up.
>>=20
>> Regards
>>=20
>> Bernhard


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