RPC Messages

This section explains the RPC messages.

The initial structure of an RPC message is as follows:


struct rpc_msg {
     unsigned int  xid;
     union switch (enum msg_type mtype)  {
          case CALL:
               call_body cbody;
          case REPLY;
               reply_body rbody;
     } body;
};

All RPC call and reply messages start with a transaction identifier, xid, which is followed by a two-armed discriminated union. The union's discriminant is msg_type, which switches to one of the following message types: CALL or REPLY. The msg_type has the following enumeration:


enum msg_type {
     CALL     = 0,
     REPLY    = 1
};

The xid parameter is used by clients matching a reply message to a call message or by servers detecting retransmissions. The server side does not treat the xid parameter as a sequence number.

The initial structure of an RPC message is followed by the body of the message. The body of a call message has one form. The body of a reply message, however, takes one of two forms, depending on whether a call is accepted or rejected by the server.