Protocol-specific opcodes are defined relative to an identifier that has been assigned to each protocol. For example, the protocol ARP has been assigned the id ARP_CTL. Individual opcodes are then defined (in arp.h) as
This scheme is used to ensure that all control opcodes are unique. By convention, protocol-specific opcodes defined by protocol XYZ are prefixed with XYZ_. Also, until an identifier has been assigned to a protocol you are writing (i.e., upi.h has been edited), you can use a set of temporary ids: TMP0_CTL, TMP1_CTL, etc.
Protocol-specific control operations are described in the manual page for each protocol in appendix A.