net: l2: ppp: fix k_work API usage in carrier on/off handling

net_ppp_carrier_on() and net_ppp_carrier_off() call k_work_init() on
work item that can be pending or still be processed in another thread.
This results in undefined behavior.

Initialize work item once and use an atomic flag to switch between
up/down carrier state. Submit work to workqueue whenever up/down carrier
state changes, so that last state is always properly propagated to
network interface layer.

Signed-off-by: Marcin Niestroj <m.niestroj@grinn-global.com>
2 files changed