dhcpcd-discuss

On Wednesday 27 April 2016 11:02:38 Shahid Mahmood wrote:
> Use case is a multiple vlan environment. At start, the device obtains a
> lease on a no-vlan (eth0) dhcp server. The lease informs us (using a custom
> option) to switch to another vlan, say 345 (as supplied). We will first
> need to release the old eth0 lease and then request new lease using the
> provided vlan id.
> 
> Basically we cant hard code the vlan id (and consequently adaptor name) in
> the .conf file because it is not known.
> 
> Can you suggest why my approach would not work? (ie putting desired
> interface name in .conf file).
> (I want to avoid having to deal with pidfile).

Everything in dhcpcd is known :D
If you're more clever with shell you don't even need the -M flag, but I'll 
leave that exercise upto the reader.

Start it up
dhcpcd -M eth0

In dhcpcd.enter-hook, maybe something like this (untested).

if $if_up && [ "$old_vlanid" != "$new_vlanid"]; then
	# vlan changed, release current.
	# This works because of the -M flag.
	dhcpcd -k

	# Fire up the vlan
	platform_specific_vlan_init

	# Request DHCP over it, background right away
	dhcpcd -bM eth0."$new_vlanid"

	# Exit dhcpcd-run-hooks
	exit 1
fi

Roy