NFSCLNT(2) System Calls Manual NFSCLNT(2)

nfsclntNFS client services

#include <unistd.h>
#include <nfs/nfs.h>

nfsclnt(unsigned long request, void *argstructp);

The () function is used by the NFS client daemons to pass information into and out of the kernel. The request argument consists of several bits that show what action is to be taken once in the kernel and the argstructp points to any corresponding data that the action may require.

rpc.lockd(8) calls () with the flag NFSCLNT_LOCKDANS and a pointer to a

struct lockd_ans {
	int		la_version;		/* lockd_ans version */
	int		la_errno;		/* return status */
	u_int64_t	la_xid;			/* unique message transaction ID */
	int		la_flags;		/* answer flags */
	pid_t		la_pid;			/* pid of lock requester/owner */
	off_t		la_start;		/* lock starting offset */
	off_t		la_len;			/* lock length */
	int 		la_fh_len;		/* The file handle length. */
	u_int8_t	la_fh[NFSV3_MAX_FH_SIZE];/* The file handle. */

to pass the response to an NFS file locking request back into the kernel.

Upon successful completion, a value of 0 is returned. Otherwise, -1 is returned and the global variable errno is set to specify the error.

The caller is not the super-user.
The action specified by the flags argument was not valid.
argstructp points to an invalid address.
The response doesn't match any currently-outstanding lock request.
nfsclnt character device was not found.


The nfsclnt system call is designed specifically for the NFS client daemons and as such is specific to their requirements. Several fields of the argument structures are assumed to be valid, such that nfsclnt must be used with extreme care.

January 9, 2007 macOS 14.4