DHCP at initrd time broken (ip=dhcp)
The Alpine kernel is built with CONFIG_IP_PNP=y and CONFIG_IP_PNP_DHCP=y, which means that it should obtain an IP address if booted with ip=dhcp. However, this appears to require that the relevant network drivers are built into the kernel itself rather than as modules.
We should therefore disable CONFIG_IP_PNP and call udhcpc at initrd time if ip=dhcp is spotted in the command line. This will require modification to the initrd init script and inclusion of an appropriate udhcpc handler in the initrd.
This is a blocker for allowing Alpine to boot usefully with PXE (i.e., with a NFS or HTTP server as alpine_dev.)