Multiple Server Versions

By convention, the first version number of a program, PROG, is named PROGVERS_ORIG and the most recent version is named PROGVERS. Program version numbers must be assigned consecutively. Leaving a gap in the program version sequence can cause the search algorithm not to find a matching program version number that is defined.

Only the owner of a program should change version numbers. Adding a version number to a program that you do not own can cause severe problems when the owner increments the version number. Sun registers version numbers and answers questions about them (rpc@Sun.com).

Suppose a new version of the ruser program returns an unsigned short rather than an int. If you name this version RUSERSVERS_SHORT, a server that supports both versions would do a double register. Use the same server handle for both registrations.

Example 5-15 Server Handle for Two Versions of Single Routine

if (!svc_reg(transp, RUSERSPROG, RUSERSVERS_ORIG, 
                        nuser, nconf))
{
    fprintf(stderr, "can't register RUSER service\n");
    exit(1);
}
if (!svc_reg(transp, RUSERSPROG, RUSERSVERS_SHORT, nuser,
                        nconf)) {
    fprintf(stderr, "can't register RUSER service\n");
    exit(1);
}

Both versions can be performed by a single procedure, as shown in the following example.

Example 5-16 Procedure for Two Versions of Single Routine

void
nuser(rqstp, transp)
    struct svc_req *rqstp;
    SVCXPRT *transp;
{
    unsigned int nusers;
    unsigned short nusers2;
    switch(rqstp->rq_proc) {
        case NULLPROC:
            if (!svc_sendreply( transp, xdr_void, 0))
                fprintf(stderr, "can't reply to RPC call\n");
            return;
        case RUSERSPROC_NUM:
            /*
             * Code here to compute the number of users
             * and assign it to the variable nusers
             */
        switch(rqstp->rq_vers) {
            case RUSERSVERS_ORIG:
                if (! svc_sendreply( transp, xdr_u_int, &nusers))
                    fprintf(stderr, "can't reply to RPC call\n");
                break;
            case RUSERSVERS_SHORT:
                nusers2 = nusers;
                if (! svc_sendreply( transp, xdr_u_short, &nusers2))
                    fprintf(stderr, "can't reply to RPC call\n");
                break;
        }
        default:
            svcerr_noproc(transp);
            return;
    }
    return;
}