Re: [PATCH v3] treewide: Introduce 'local mode' for disconnected setups

[Paul Holzinger <pholzing@redhat.com>]

On 26/11/2024 06:54, Stefano Brivio wrote:
> There are setups where no host interface is available or configured
> at all, intentionally or not, temporarily or not, but users expect
> (Podman) containers to run in any case as they did with slirp4netns,
> and we're now getting reports that we broke such setups at a rather
> alarming rate.
>
> To this end, if we don't find any usable host interface, instead of
> exiting:
>
> - for IPv4, use 169.254.2.1 as guest/container address and 169.254.2.2
>    as default gateway
>
> - for IPv6, don't assign any address (forcibly disable DHCPv6), and
>    use the *first* link-local address we observe to represent the
>    guest/container. Advertise fe80::1 as default gateway
>
> - use 'tap0' as default interface name for pasta
>
> Change ifi4 and ifi6 in struct ctx to int and accept a special -1
> value meaning that no host interface was selected, but the IP family
> is enabled. The fact that the kernel uses unsigned int values for
> those is not an issue as 1. one can't create so many interfaces
> anyway and 2. we otherwise handle those values transparently.
>
> Fix a botched conditional in conf_print() to actually skip printing
> DHCPv6 information if DHCPv6 is disabled (and skip printing NDP
> information if NDP is disabled).
>
> Link: https://github.com/containers/podman/issues/24614
> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Tested-by: Paul Holzinger <pholzing@redhat.com>

As mentioned on IRC I noticed a problem in Podman with this as we ignore 
link local addresses when adding host entries but that is a Podman bug 
and must be fixed there.


-- 
Paul Holzinger