[systemd-devel] how to automate undirected UDP broadcast route for linklocal addresses?

[Bill Plunkett]

FWIW, it appears that this is indeed possible via the
[Network]DefaultRouteOnDevice setting:

/usr/sbin# cat /etc/systemd/network/eth0.network.dhcp
[Match]
Name=eth0
KernelCommandLine=!nfsroot

[Network]
DHCP=ipv4
LinkLocalAddressing=ipv4
DefaultRouteOnDevice=true

[DHCP]
ClientIdentifier=mac
RouteMetric=10

On Mon, Jun 10, 2024 at 1:52 PM Bill Plunkett <bill at plunkware.com> wrote:

> I have a yocto-hardknott (systemd v247) embedded system using link local
> addressing.  Undirected UDP broadcasts (i.e. dest ip = 255.255.255.255) are
> failing with a 'Network is unreachable' error.  I've been able to fix this
> with the 'route add' command shown below, but would prefer to automate it
> with systemd.  Any help is greatly appreciated.
>
> This command allows undirected broadcasts:
>
> route add -net 255.255.255.255 netmask 255.255.255.255 dev eth0
>
> systemd configuration:
>
> [Match]
> Name=eth0
> KernelCommandLine=!nfsroot
>
> [Network]
> DHCP=ipv4
> LinkLocalAddressing=ipv4
>
> [DHCP]
> ClientIdentifier=mac
> RouteMetric=10
>
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