Currently, we can not set the metric of routes in dhcp.
It's ok if there is only a network interface.
But if there are multiple network interfaces, and both have a default route,
We need to set the metric of the route to make the traffic
go through the correct network interface.
For host-local and static, we can set the metric with the route.priority option.
But there is no such option for dhcp.
Signed-off-by: Songmin Li <lisongmin@protonmail.com>
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