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NetBSD 6.1.5 - man page for nfssvc (netbsd section 2)

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NFSSVC(2)			     BSD System Calls Manual				NFSSVC(2)

NAME
     nfssvc -- NFS services

LIBRARY
     Standard C Library (libc, -lc)

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

     int
     nfssvc(int flags, void *argstructp);

DESCRIPTION
     The nfssvc() function is used by the NFS daemons to pass information into and out of the
     kernel and also to enter the kernel as a server daemon.  The flags argument consists of sev-
     eral bits that show what action is to be taken once in the kernel and the argstructp points
     to one of three structures depending on which bits are set in flags.

   Calls used by nfsd(8)
     On the server side, nfssvc() is called with the flag NFSSVC_NFSD and a pointer to a

     struct nfsd_srvargs {
	     struct nfsd     *nsd_nfsd;      /* Pointer to in kernel nfsd struct */
	     uid_t	     nsd_uid;	     /* Effective uid mapped to cred */
	     u_long	     nsd_haddr;      /* Ip address of client */
	     struct ucred    nsd_cr;	     /* Cred. uid maps to */
	     int	     nsd_authlen;    /* Length of auth string (ret) */
	     char	     *nsd_authstr;   /* Auth string (ret) */
     };

     to enter the kernel as an nfsd(8) daemon.	Whenever an nfsd(8) daemon receives a Kerberos
     authentication ticket, it will return from nfssvc() with errno set to ENEEDAUTH.  The
     nfsd(8) will attempt to authenticate the ticket and generate a set of credentials on the
     server for the ``user id'' specified in the field nsd_uid.  This is done by first authenti-
     cating the Kerberos ticket and then mapping the Kerberos principal to a local name and get-
     ting a set of credentials for that user via getpwnam(3) and getgrouplist(3).  If successful,
     the nfsd(8) will call nfssvc() with the NFSSVC_NFSD and NFSSVC_AUTHIN flags set to pass the
     credential mapping in nsd_cr into the kernel to be cached on the server socket for that
     client.  If the authentication failed, nfsd(8) calls nfssvc() with the flags NFSSVC_NFSD and
     NFSSVC_AUTHINFAIL to denote an authentication failure.

     The master 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.

   Calls used by mountd(8)
     The mountd(8) server daemon calls nfssvc() with the flag NFSSVC_SETEXPORTSLIST and a pointer
     to a struct mountd_exports_list object to atomically change the exports lists of a specific
     file system.  This structure has the following fields:

     const char *mel_path  Path to the file system that will have its exports list replaced by
			   the one described in the other fields.

     size_t mel_nexports   Number of valid entries in the mel_export field.  If zero, the exports
			   list will be cleared for the given file system.

     struct export_args mel_export[AF_MAX]
			   Set of exports to be used for the given file system.

RETURN VALUES
     Usually nfssvc does not return unless the server is terminated by a signal when a value of 0
     is returned.  Otherwise, -1 is returned and the global variable errno is set to specify the
     error.

ERRORS
     [ENEEDAUTH]	This special error value is really used for authentication support, par-
			ticularly Kerberos, as explained above.

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

SEE ALSO
     mount_nfs(8), nfsd(8)

HISTORY
     The nfssvc function first appeared in 4.4BSD.

BUGS
     The nfssvc system call is designed specifically for the NFS support daemons and as such is
     specific to their requirements.  It should really return values to indicate the need for
     authentication support, since ENEEDAUTH is not really an error.  Several fields of the argu-
     ment structures are assumed to be valid and sometimes to be unchanged from a previous call,
     such that nfssvc must be used with extreme care.

BSD					December 30, 2006				      BSD
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