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.\" $DragonFly: src/share/man/man9/nlookup.9,v 1.6 2006/02/17 19:37:10 swildner Exp $
.\"
.Dd August 6, 2005
.Os
.Dt NLOOKUP 9
.Sh NAME
.Nm nlookup ,
.Nm nlookup_init ,
.Nm nlookup_init_raw ,
.Nm nlookup_set_cred ,
.Nm nlookup_zero ,
.Nm nlookup_done ,
.Nm nlookup_simple ,
.Nm nlookup_mp ,
.Nm nreadsymlink ,
.Nm naccess ,
.Nm naccess_va ,
.Nm namei
.Nd namecache API
.Sh SYNOPSIS
.In sys/types.h
.In sys/nlookup.h
.Ft int
.Fn nlookup "struct nlookupdata *nd"
.Ft int
.Fn nlookup_init "struct nlookupdata *nd" "const char *path" "enum uio_seg seg" "int flags"
.Ft int
.Fn nlookup_init_raw "struct nlookupdata *nd" "const char *path" "enum uio_seg seg" "int flags" "struct ucred *cred" "struct namecache *ncstart"
.Ft void
.Fn nlookup_set_cred "struct nlookupdata *nd" "struct ucred *cred"
.Ft void
.Fn nlookup_zero "struct nlookupdata *nd"
.Ft void
.Fn nlookup_done "struct nlookupdata *nd"
.Ft "struct namecache *"
.Fn nlookup_simple "const char *str" "enum uio_seg seg" "int niflags" "int *error"
.Ft int
.Fn nlookup_mp "struct mount *mp" "struct namecache **ncpp"
.Ft int
.Fn nreadsymlink "struct nlookupdata *nd" "struct namecache *ncp" "struct nlcomponent *nlc"
.Ft int
.Fn naccess "struct namecache *ncp" "int vmode" "struct ucred *cred"
.Ft int
.Fn naccess_va "struct vattr *va" "int vmode" "struct ucred *cred"
.Sh DESCRIPTION
.Fn nlookup
does a generic namecache lookup.
Note that the passed
.Fa "struct nlookupdata"
is not
.Fn nlookup_done Ap d
on return, even if an error occurs.
If no error occurs the returned nl_ncp
is always referenced and locked, otherwise it may or may not be.
Intermediate directory elements, including the current directory,
require execute (search) permission.
.Fn nlookup
does not examine the access permissions on the returned element.
If
.Dv NLC_CREATE
or
.Dv NLC_DELETE
is set the last directory must allow
node creation
.Po
.Dv VCREATE Ns / Ns Dv VDELETE
.Pc ,
and an error code of 0
will be returned for a non-existant target.
Otherwise a non-existant target will cause
.Er ENOENT
to be returned.
.Pp
.Fn nlookup_init
initializes a
.Fa "struct nlookupdata" ,
and does an early error
return for copyin faults or a degenerate empty string (which is
not allowed).
The first process proc0's
credentials are used if the calling
thread is not associated with a process context.
.Pp
.Fn nlookup_init_raw
works similarly to
.Fn nlookup_init
but does not assume a process context.
rootncp is always chosen for the root directory and the
.Fa cred
and starting directory are supplied in the arguments.
.Pp
.Fn nlookup_set_cred
sets a different credential; this credential will be used by
future operations performed on nd.nl_open_vp
and the
.Fa nlookupdata
structure.
.Pp
.Fn nlookup_zero
zeroes a given
.Fa "struct nlookupdata" .
.Pp
.Fn nlookup_done
cleans up an
.Fa nlookupdata
structure after we are through with
it.
This function may be called on any nlookupdata structure
initialized with
.Fn nlookup_init .
Calling
.Fn nlookup_done
is mandatory in all cases except where
.Fn nlookup_init
returns an error, even if as a consumer you believe you
have taken all dynamic elements out of the
.Fa nlookupdata
structure.
.Pp
.Fn nlookup_simple
is a simple all-in-one nlookup.
It returns a locked namecache structure or NULL if an error
occured.
Note that the returned ncp
is not checked for permissions,
though
.Dv VEXEC
is checked on the directory path leading up to
the result.
The caller must call
.Fn naccess
to check the permissions of the returned leaf.
.Pp
.Fn nlookup_mp
is used to resolve a mount point's glue ncp.
It creates the illusion of continuity in the namecache tree
by connecting the ncp related to the vnode under the mount
to the ncp related to the mount's root vnode.
If no error occured a locked, ref'd ncp is stored in
.Fa *ncpp .
.Pp
.Fn nreadsymlink
reads the contents of a symlink, allocates a path buffer out
of the namei_zone and initialize the supplied nlcomponent
with the result.
If an error occurs no buffer will be allocated or returned
in the nlc.
.Pp
.Fn naccess
generally checks the V* access bits from
.Pa sys/vnode.h .
All specified bits must pass for this function to return 0.
If
.Dv VCREATE
is specified and the target ncp represents a
non-existant file or dir, or if
.Dv VDELETE
is specified and the
target exists, the parent directory is checked for
.Dv VWRITE .
If
.Dv VEXCL
is specified and the target ncp represents a positive
hit, an error is returned.
If
.Dv VCREATE
is not specified and the target does not exist
(negative hit),
.Er ENOENT
is returned.
Note that
.Fn nlookup
does not (and should not) return
.Er ENOENT
for non-existant leafs.
The passed ncp may or may not be locked.
The caller should use a locked ncp on leaf lookups, especially
for
.Dv VCREATE ,
.Dv VDELETE ,
and
.Dv VEXCL
checks.
.Pp
.Fn naccess_va
checks the requested access against the given
.Fa vattr using
.Fa cred .
.Sh SEE ALSO
.Xr VFS 9 ,
.Xr vnode 9
.Pp
.Pa src/sys/kern/vfs_nlookup.c
.Sh AUTHORS
This man page was written by
.An Sascha Wildner .
.Sh BUGS
This man page needs further work.