jail.3

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.Dd August 31, 2010
.Dt JAIL 3
.Os
.Sh NAME
.Nm jail_getid ,
.Nm jail_getname ,
.Nm jail_setv ,
.Nm jail_getv ,
.Nm jailparam_all ,
.Nm jailparam_init ,
.Nm jailparam_import ,
.Nm jailparam_import_raw ,
.Nm jailparam_set ,
.Nm jailparam_get ,
.Nm jailparam_export ,
.Nm jailparam_free
.Nd create and manage system jails
.Sh LIBRARY
.Lb libjail
.Sh SYNOPSIS
.In sys/param.h
.In sys/jail.h
.In jail.h
.Vt extern char jail_errmsg[] ;
.Ft int
.Fn jail_getid "const char *name"
.Ft char *
.Fn jail_getname "int jid"
.Ft int
.Fn jail_setv "int flags" ...
.Ft int
.Fn jail_getv "int flags" ...
.Ft int
.Fn jailparam_all "struct jailparam **jpp"
.Ft int
.Fn jailparam_init "struct jailparam *jp" "const char *name"
.Ft int
.Fn jailparam_import "struct jailparam *jp" "const char *value"
.Ft int
.Fn jailparam_import_raw "struct jailparam *jp" "void *value" "size_t valuelen"
.Ft int
.Fn jailparam_set "struct jailparam *jp" "unsigned njp" "int flags"
.Ft int
.Fn jailparam_get "struct jailparam *jp" "unsigned njp" "int flags"
.Ft char *
.Fn jailparam_export "struct jailparam *jp"
.Ft void
.Fn jailparam_free "struct jailparam *jp" "unsigned njp"
.Sh DESCRIPTION
The
.Nm jail
library is an interface to the
.Xr jail_set 2
and
.Xr jail_get 2
system calls, and the
.Va security.jail.param
MIB entries.
It simplifies the conversion of prison parameters between internal and
string formats, allowing the setting and querying of prisons without
knowing the parameter formats.
.Pp
The
.Fn jail_getid
function returns the JID of the jail identified by
.Fa name ,
or \-1 if the jail does not exist.
.Pp
The
.Fn jail_getname
function returns the name of the jail identified by
.Fa jid ,
or
.Dv NULL
if the jail does not exist.
.Pp
The
.Fn jail_setv
function takes a null-terminated list of name and value strings,
and passes it to
.Xr jail_set 2 .
.Pp
The
.Fn jail_getv
function takes a null-terminated list of name and value strings,
and passes it to
.Xr jail_get 2 .
It is the caller's responsibility to ensure that the value strings point
to buffers large enough to hold the string representation of the
returned parameters.
.Pp
The
.Fn jailparam_all
function sets
.Fa jpp
to a list of all known jail parameters, and returns the number of
parameters.
The list should later be freed with
.Fn jailparam_free
and
.Xr free 3 .
.Pp
The
.Fn jailparam_init
function clears a parameter record and copies the
.Fa name
to it.
After use, it should be freed with
.Fn jailparam_free .
.Pp
The
.Fn jailparam_import
function adds a
.Fa value
to a parameter record, converting it from a string to its native form.
The
.Fn jailparam_import_raw
function adds a value without performing any conversion.
.Pp
The
.Fn jailparam_set
function passes a list of parameters to
.Xr jail_set 2 .
The parameters are assumed to have been created with
.Fn jailparam_init
and
.Fn jailparam_import .
.Pp
The
.Fn jailparam_get
function passes a list of parameters to
.Xr jail_get 2 .
The parameters are assumed to have been created with
.Fn jailparam_init
or
.Fn jailparam_list ,
with one parameter (the key) having been given a value with
.Fn jailparam_import .
.Pp
The
.Fn jailparam_export
function returns the string equivalent of a parameter value.
The returned string should be freed after use.
.Pp
The
.Fn jailparam_free
function frees the stored names and values in a parameter list.
If the list itself came from
.Fn jailparam_all ,
it should be freed as well.
.Sh RETURN VALUES
The
.Fn jail_getid ,
.Fn jail_setv ,
.Fn jail_getv ,
.Fn jailparam_set
and
.Fn jailparam_get
functions return a JID on success, or \-1 on error.
.Pp
The
.Fn jail_getname
and
.Fn jailparam_export
functions return a dynamically allocated string on success, or
.Dv NULL
on error.
.Pp
The
.Fn jailparam_all
function returns the number of parameters on success, or \-1 on error.
.Pp
The
.Fn jailparam_init ,
.Fn jailparam_import
and
.Fn jailparam_import_raw
functions return 0 on success, or \-1 on error.
.Pp
Whenever an error is returned,
.Va errno
is set, and the global string
.Va jail_errmsg
contains a description of the error, possibly from
.Xr jail_set 2
or
.Xr jail_get 2 .
.Sh EXAMPLES
Set the hostname of jail
.Dq foo
to
.Dq foo.bar :
.Bd -literal -offset indent
jail_setv(JAIL_UPDATE, "name", "foo", "host.hostname", "foo.bar",
    NULL);
.Ed
.Pp
OR:
.Bd -literal -offset indent
struct jailparam params[2];
jailparam_init(&params[0], "name");
jailparam_import(&params[0], "foo");
jailparam_init(&params[1], "host.hostname");
jailparam_import(&params[1], "foo.bar");
jailparam_set(params, 2, JAIL_UPDATE);
jailparam_free(params, 2);
.Ed
.Pp
Retrieve the hostname of jail
.Dq foo :
.Bd -literal -offset indent
char hostname[MAXHOSTNAMELEN];
jail_getv(0, "name", "foo", "host.hostname", hostname, NULL);
.Ed
.Pp
OR:
.Bd -literal -offset indent
struct jailparam params[2];
jailparam_init(&params[0], "name");
jailparam_import(&params[0], "foo");
jailparam_init(&params[1], "host.hostname");
jailparam_get(params, 2, 0);
hostname = jailparam_export(&params[1]);
jailparam_free(params, 2);
\&...
free(hostname);
.Ed
.Sh ERRORS
The
.Nm jail
functions may return errors from
.Xr jail_set 2 ,
.Xr jail_get 2 ,
.Xr malloc 3
or
.Xr sysctl 3 .
In addition, the following errors are possible:
.Bl -tag -width Er
.It Bq Er EINVAL
A parameter value cannot be converted from the passed string to its
internal form.
.It Bq Er ENOENT
The named parameter does not exist.
.It Bq Er ENOENT
A parameter is of an unknown type.
.El
.Sh SEE ALSO
.Xr jail 2 ,
.Xr sysctl 3 ,
.Xr jail 8
.Sh HISTORY
The
.Nm jail
library first appeared in
.Fx 8.0 .
.Sh AUTHORS
.An James Gritton