Now that nfsm_reply() does not usually set 'error' to 0, we need

to do it explicitly in nfsrv_noop so that the reply gets sent back
to the client. This fixes the generation of a selection of RPC
error replies (RPC_PROGMISMATCH, RPC_PROGUNAVAIL, RPC_PROCUNAVAIL
etc.) that are used by some clients to detect support for optional
protocols and features.

Reviewed by:	peter
Reported by:	Thomas Quinot <quinot@inf.enst.fr>
PR:		kern/31479

sys/nfsserver/nfs_serv.c

@@ -4000,6 +4000,7 @@ nfsrv_noop(struct nfsrv_descript *nfsd, struct nfssvc_sock *slp,
 	else
 		error = EPROCUNAVAIL;
 	nfsm_reply(0);
+	error = 0;
 nfsmout:
 	return (error);
 }