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     nfssvc — NFS services


     Standard C Library (libc, -lc)


     #include <sys/param.h>
     #include <sys/mount.h>
     #include <sys/time.h>
     #include <nfs/rpcv2.h>
     #include <nfsserver/nfs.h>
     #include <unistd.h>

     nfssvc(int flags, void *argstructp);


     The nfssvc() system call 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 */
             u_char          *ncd_authstr;   /* Authenticator string */
             int             ncd_verflen;    /* and the verifier */
             u_char          *ncd_verfstr;
             NFSKERBKEY_T    ncd_key;        /* Session key */

     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) utility will
     return from nfssvc() with errno == ENEEDAUTH whenever the client side requires an ``rcmd''
     authentication ticket for the user.  The mount_nfs(8) utility 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 structure.  If mount_nfs(8) failed to
     get the ticket, nfssvc() will be called with the flags NFSSVC_MNTD, NFSSVC_GOTAUTH and
     NFSSVC_AUTHINFAIL to 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 */
             uint32_t        nsd_haddr;      /* Ip address of client */
             struct ucred    nsd_cr;         /* Cred. uid maps to */
             int             nsd_authlen;    /* Length of auth string (ret) */
             u_char          *nsd_authstr;   /* Auth string (ret) */
             int             nsd_verflen;    /* and the verifier */
             u_char          *nsd_verfstr;
             struct timeval  nsd_timestamp;  /* timestamp from verifier */
             uint32_t        nsd_ttl;        /* credential ttl (sec) */
             NFSKERBKEY_T    nsd_key;        /* Session key */

     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)
     utility 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
     authenticating 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) utility 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 signal 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.


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


     The nfssvc() system call first appeared in 4.4BSD.


     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
     argument structures are assumed to be valid and sometimes to be unchanged from a previous
     call, such that nfssvc() must be used with extreme care.