An assertion in dhcp_network_bind_raw_socket() is triggered when
starting an sd_dhcp_client without setting a MAC address first.
- sd_dhcp_client_start()
- client_start()
- client_start_delayed()
- dhcp_network_bind_raw_socket()
In that case, the arp-type and MAC address is still unset. Note that
dhcp_network_bind_raw_socket() already checks for a valid arp-type
and MAC address below, so we should just gracefully return -EINVAL.
Maybe sd_dhcp_client_start() should fail earlier when starting without
MAC address. But the failure here will be correctly propagated and
the start aborted.
Fixes: 76253e73f9