nfssvc(2) - NetBSD Manual Pages

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NFSSVC(2)                 NetBSD 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 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.

   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 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 map-
     ping 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 fail-
     ure.

     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_REPLACEEXPORTSLIST and a pointer to a struct mountd_exports_list
     object to atomically replace 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 sys-
                           tem.


RETURN VALUES

     Usually 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.


ERRORS

     [ENEEDAUTH]        This special error value is really used for authenti-
                        cation support, particularly 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 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.

NetBSD 10.1                      June 8, 2021                      NetBSD 10.1