Re: Loss of Network Adress is DHCP Server failed for some hours

[Francesco Giudici <fgiudici redhat com>]

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On 02/10/2017 17:53, Oliver Freyermuth wrote:
> Hi!
>
> [...] Sadly, also -EPERM here. We use CentOS 7, so there's no RHEL
> support contract. Could you maybe describe the solution given
> there? I would be curious to implement that on our systems.


Sorry, I did not realized access to that bugzilla was restricted.
Put the relevant info in the answer to Olaf.

> > The fact that an ipv4 connection may fail (also one with dhcp) is
> > a feature: this would allow for instance to setup multiple
> > connections with different priorities on the same interface,
> > giving first a try to the dhcp connection and then falling back
> > to another one with static ipv4 address or with 802.1x
> > configuration.
> Understood. Still I would strongly prefer it if there was an option
> to keep trying forever, as all other network managers I know do
> (dhclient, dhcpcd, any device I have encountered so far).

Something is already there on upstream master. You can do:
nmcli con mod $CON ipv4.dhcp-timeout infinity

but it is available via nmcli only...

> I think this "option" I am longing for is the suggestion you
> describe in your last paragraph.
>
> If there is only one (DHCP) connection configured for the
> interface, I would even expect "trying DHCP forever" to be the
> default behaviour, since there is no fallback to fall back to. Does
> that sound reasonable?
>
> Alternatively: Is it possible to tell network manager to retry the
> complete activation cycle, i.e. retry all configured connections
> for the interface (in order) again after all have failed? In case
> only one connection (DHCP) is configured, this would effectively
> result in trying DHCP forever.

Yes, this seems reasonable.
Maybe keep periodically trying activation of connection with
auto-activate enabled that point to an interface with no active
connections on top of it.

> > If you really want your dhcp connection to keep trying forever
> > the only viable solution at present seems to be the
> > ipv4.dhcp-timeout property. Maybe we could manage to keep trying
> > also with a brand new value to the ipv4.method... see: 
> > https://bugzilla.redhat.com/show_bug.cgi?id=1350830#c1 Apart from
> > that, there is nothing I would change.
> That sounds like a good idea (for the future). Sadly, -EPERM for
> your link from my side.
Sorry, link to the same bugzilla as above.
Summing up, basically, what could be taken into account is to review
the meaning of ipv4/ipv6.may-fail=yes: we can keep retrying dhcp while
keeping the connection active.
This would solve all the complains while leaving the "stop" behavior
there if one chooses may-fail=no.

Cheers

Francesco

> Cheers and many thanks for your detailed reply! Much appreciated!
>
> Oliver
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