When using offloaded network, an L2 is never assigned to the net_if.
Only certain portions of the net_if code are referenced such as:
net_if_up()
net_if_down()
And these functions make use of several L2 references:
get_flags()
enable()
Let's add checks to make sure we don't deref a NULL when using these
functions.
Fixes the following exception on K64F and other HW which can make
use of offloaded network HW:
FATAL: ***** Reserved Exception ( -16) *****
FATAL: r0/a1: 0x00000010 r1/a2: 0x0000644f r2/a3: 0x00000000
FATAL: r3/a4: 0x00000000 r12/ip: 0x2000474c r14/lr: 0x0001475b
FATAL: xpsr: 0x00000000
FATAL: Faulting instruction address (r15/pc): 0x0001b1cd
FATAL: >>> ZEPHYR FATAL ERROR 0: CPU exception
FATAL: Current thread: 0x20004c4c (unknown)
Fixes: https://github.com/zephyrproject-rtos/zephyr/issues/18957
Signed-off-by: Michael Scott <mike@foundries.io>
a4f4f6d6f3