With dhcpcd.service enabled, a master dhcpcd process monitors new interfaces and automatically configures them as they are brought up. In particular, when I associate my wireless interface (wlan0) to an access point using wpa_supplicant, dhcpcd automatically configures the new interface.

However, this fails if, prior to starting wpa_supplicant and associating, I spoof the MAC address of the interface using:

ip link set wlan0 down
ip link set wlan0 addr 02:03:05:07:11:13
ip link set wlan0 up

Then, the master dhcpcd process fails to notice the interface. Even asking it nicely to probe the new interface fails:

# dhcpcd wlan0
dhcpcd[728]: sending commands to master dhcpcd process

In spite of this nice reply from the dhcpcd slave, the interface remains unconfigured.

Note that everything works properly if I reset the interface MAC address to its hardware value.