nfssvc man page on 4.4BSD

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

     nfssvc — NFS services

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

     nfssvc(int flags, void *argstructp);

     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 several 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.

     On the client side, nfsiod(8) calls nfssvc() with the flags argument set
     to NFSSVC_BIOD and argstructp set to NULL to enter the kernel as a block
     I/O server daemon.	 For NQNFS, mount_nfs(8) calls nfssvc() with the
     NFSSVC_MNTD flag, optionally or'd with the flags NFSSVC_GOTAUTH and
     NFSSVC_AUTHINFAIL along with a pointer to a

     struct nfsd_cargs {
	     char	     *ncd_dirp;	     /* Mount dir path */
	     uid_t	     ncd_authuid;    /* Effective uid */
	     int	     ncd_authtype;   /* Type of authenticator */
	     int	     ncd_authlen;    /* Length of authenticator string */
	     char	     *ncd_authstr;   /* Authenticator string */

     structure.	 The initial call has only the NFSSVC_MNTD flag set to specify
     service for the mount point.  If the mount point is using Kerberos, then
     the mount_nfs(8) daemon will return from nfssvc() with errno == ENEEDAUTH
     whenever the client side requires an ``rcmd'' authentication ticket for
     the user.	Mount_nfs(8) will attempt to get the Kerberos ticket, and if
     successful will call nfssvc() with the flags NFSSVC_MNTD and
     NFSSVC_GOTAUTH after filling the ticket into the ncd_authstr field and
     setting the ncd_authlen and ncd_authtype fields of the nfsd_cargs struc‐
     ture.  If mount_nfs(8) failed to get the ticket, nfssvc() will be called
     denote a failed authentication attempt.

     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 == 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 authenticat‐
     ing the Kerberos ticket and then mapping the Kerberos principal to a
     local name and getting 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.

     Normally nfssvc does not return unless the server is terminated by a sig‐
     nal when a value of 0 is returned.	 Otherwise, -1 is returned and the
     global variable errno is set to specify the error.

     [ENEEDAUTH]  This special error value is really used for authentication
		  support, particularly Kerberos, as explained above.

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

     nfsd(8), mount_nfs(8), nfsiod(8)

     The nfssvc function first appeared in 4.4BSD.

     The nfssvc system call is designed specifically for the NFS support dae‐
     mons 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 argument struc‐
     tures are assumed to be valid and sometimes to be unchanged from a previ‐
     ous call, such that nfssvc must be used with extreme care.

BSD				 June 9, 1993				   BSD

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