Why I did it
Add dhcp_server ipv4 feature to SONiC.
HLD: sonic-net/SONiC#1282
How I did it
To be clarify: This container is disabled by INCLUDE_DHCP_SERVER = n for now, which would cause container not build.
Add INCLUDE_DHCP_SERVER to indicate whether to build dhcp_server container
Add docker file for dhcp_server, build and install kea-dhcp4 inside container
Add template file for dhcp_server container services.
Add entry for dhcp_server to FEATURE table in config_db.
How to verify it
Build image with INCLUDE_DHCP_SERVER = y to verify:
Image can be install successfully without crush.
By config feature state dhcp_server enabled to enable dhcp_server.
