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;
}