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IPv6 prefix delegation: avahi-daemon vs dhcpcd vs kernel

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  IPv6 prefix delegation: avahi-daemon vs dhcpcd vs kernel Harald Dunkel <harald.dunkel@aixigo.com> - 2019-07-29 11:40 +0200
    Re: IPv6 prefix delegation: avahi-daemon vs dhcpcd vs kernel Reco <recoverym4n@enotuniq.net> - 2019-07-29 12:00 +0200
    Re: IPv6 prefix delegation: avahi-daemon vs dhcpcd vs kernel Pascal Hambourg <pascal@plouf.fr.eu.org> - 2019-07-29 13:10 +0200
      Re: IPv6 prefix delegation: avahi-daemon vs dhcpcd vs kernel Pascal Hambourg <pascal@plouf.fr.eu.org> - 2019-07-29 13:30 +0200

#211845 — IPv6 prefix delegation: avahi-daemon vs dhcpcd vs kernel

Hi folks,

question about IPv6 support in sid: Whose job is it to bother
about the IPv6 addresses dynamically bound to eth0?

AFAIU the kernel sees the prefix delegation on eth0, sets the
old IPv6 address to "deprecated" and registers the new one. How
comes that avahi daemon and dhcpcd and possibly others interfere?


Every insightful comment is highly appreciated

Harri

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#211846

	Hi.

On Mon, Jul 29, 2019 at 11:07:50AM +0200, Harald Dunkel wrote:
> question about IPv6 support in sid: Whose job is it to bother
> about the IPv6 addresses dynamically bound to eth0?

Kernel's, mostly. You don't need userspace to receive and process SLAAC.


> AFAIU the kernel sees the prefix delegation on eth0, sets the
> old IPv6 address to "deprecated" and registers the new one. How
> comes that avahi daemon and dhcpcd and possibly others interfere?

I won't say anything about the avahi (don't see the need to install it),
but I'm familiar with dhcpcd.

Unless they've changed it in sid, dhcpcd should wait for RA announce for
a couple of seconds (ipv6ra_autoconf option in dhcpcd.conf) and then
send AF_NETLINK message to the kernel asking to set "global dynamic
mngtmpaddr" IP on an interface and received routes.
And, unless you force it somehow, dhcpcd should not touch
"net.ipv6.conf.$IFACE.accept_ra" kernel knob, so future RAs are
processed by the kernel directly.

Reco

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#211850

Le 29/07/2019 à 11:07, Harald Dunkel a écrit :
> 
> question about IPv6 support in sid: Whose job is it to bother
> about the IPv6 addresses dynamically bound to eth0?

It depends what dynamic configuration method is used.
SLAAC (using router advertisements) is in kernelspace. However some 
information which may be included in router advertisements such as DNS 
related information are not managed by the kernel and must be managed in 
userspace (DNS in general is not managed by the kernel).
DHCPv6 is in userspace (DHCPv6 client).

> AFAIU the kernel sees the prefix delegation on eth0, sets the
> old IPv6 address to "deprecated" and registers the new one.

Prefix delegation is a DHCPv6 feature. The kernel does managed it. Or do 
you mean prefix information in router advertisements ?

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#211851

Le 29/07/2019 à 13:08, Pascal Hambourg a écrit :
> 
> Prefix delegation is a DHCPv6 feature. The kernel does managed it.

Oops ! I meant "the kernel does NOT manage it".

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