NFSSVC(2)                     System Calls Manual                    NFSSVC(2)

NAME
     nfssvc – NFS services

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

     int
     nfssvc(int flags, void *argstructp);

DESCRIPTION
     The nfssvc() function is used by the NFS server daemon to pass
     information into and out of the kernel and also to enter the kernel as a
     server daemon.  The flags 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.

     nfssvc() is called with the flag NFSSVC_NFSD and a NULL argstructp to
     enter the kernel as an nfsd(8) daemon.  The NFSSVC_NFSD action normally
     does not return until the NFS server is stopped.

     The nfsd(8) server daemon calls nfssvc() with the flag NFSSVC_ADDSOCK and
     a pointer to a

     struct nfsd_args {
             int     sock;           /* Socket to serve */
             caddr_t name;           /* Client address for connection based sockets */
             int     namelen;        /* Length of name */
     };

     to pass a server side NFS socket into the kernel for servicing by the
     nfsd(8) daemons.

     The nfsd(8) server daemon calls nfssvc() with the flag NFSSVC_EXPORT and
     a pointer to a

     struct nfs_export_args {
             uint32_t                nxa_fsid;       /* export FS ID */
             uint32_t                nxa_expid;      /* export ID */
             char                    *nxa_fspath;    /* export FS path */
             char                    *nxa_exppath;   /* export sub-path */
             uint32_t                nxa_flags;      /* export arg flags */
             uint32_t                nxa_netcount;   /* #entries in ex_nets array */
             struct nfs_export_net_args *nxa_nets;   /* array of net args */
     };

     to pass exported file system information into the kernel.

     Additionally, the nfssvc() is used by nfsstat(1) tool to receive
     statistic about the server from kernel.  While used, argstructp points to
     struct iovec of size 2.  The first iovec entry specifies the base address
     and length of an area in memory from which data should be written.  The
     size of the available data will be returned in the location pointed by
     the second iovec entry.  The following flags are supported :

     NFSSVC_EXPORTSTATS    Used to receive exported directory status.

     NFSSVC_USERSTATS      Used to receive exported directory active user
                           status.

     NFSSVC_USERCOUNT      Used to receive current count of active NFS users.

     NFSSVC_ZEROSTATS      Used to zero NFS server statistics.

     NFSSVC_SRVSTATS       Used to receive NFS server statistics.

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

ERRORS
     [EPERM]            The caller is not the super-user.

     [EINVAL]           The action specified by the flags argument was not
                        valid.

     [EFAULT]           argstructp points to an invalid address.

     [ENOMEM]           A memory allocation failure prevented the action from
                        completing.

     [EEXIST]           An attempt was made to add a UDP socket via the
                        NFSSVC_ADDSOCK action, but the UDP socket has already
                        been added.

SEE ALSO
     nfsstat(1), nfsd(8)

HISTORY
     The nfssvc function first appeared in 4.4BSD.

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

macOS 15.2                      January 9, 2007                     macOS 15.2