CTFS_CTL
#define CT_CABANDON CTFS_CTL(0) /* Abandon contract */
#define CT_CACK CTFS_CTL(1) /* Ack a message */
#define CT_CQREQ CTFS_CTL(2) /* Request an additional quantum */
#define CT_CADOPT CTFS_CTL(3) /* Adopt a contract */
#define CT_CNEWCT CTFS_CTL(4) /* Define new contract */
#define CT_CNACK CTFS_CTL(5) /* nack a negotiation */