This has the advantage that it also works for static DHCP leases,
provided the device obtains a DHCP lease at all (and isn’t configured with a
static IP address, like the shelly motion sensors for example).
* internal/dhcp*: switch to github.com/mdlayher/packet
* internal/dhcp4d: update test constructor name to avoid packet conflict
Signed-off-by: Matt Layher <mdlayher@gmail.com>
Previously SetHostname could operate on an expired lease, or even on a
lease for a different hwaddr, if the lease for the correct hwaddr
expired and the same lease ID was given away to someone else.
That's though mostly a theoretical concern, given the actual usage of
SetHostname and the time scales involved.
The Nintendo Switch has been observed to hold on to IP addresses even after
their expiration. My guess is that this is an oversight: likely the device
enters power saving mode with a configured IP address and just sleeps through
the expiration time.
As the device seems to wake up once every hour, we enforce a minimum lease time
of 1 hour, but only for affected devices. The rest of the network gets short
lease times.
https://twitter.com/zekjur/status/1263949112036282374
This can be used to permanently override a hostname, regardless of whether the
lease is static or not. We use a separate field because we want devices to be
able to change their hostname themselves, until we override it.
Turns out a5d9e03dd3 was not entirely sufficient:
even though reused addresses would not be handed out anymore, they would still
be offered, which results in the client not being able to obtain an address.
Preferring unicast over multicast (which hogs a lot of airtime on WiFi networks)
is a best practice.
Some device/access point vendor combinations even seem to entirely eat (some?)
broadcast traffic (sometimes), e.g. my Apple iPhone SE/Ubiquiti UAP-AC-HD, so
that using unicast is required for reliable WiFi.
