JAIL(3)

NAME
jail_getid, jail_getname, jail_setv, jail_getv, jailparam_all, jailparam_init, jailparam_import, jailparam_import_raw, jailparam_set, jailparam_get, jailparam_export, jailparam_free - create and manage system jails

LIBRARY
libjail

SYNOPSIS
#include <sys/param.h>
#include <sys/jail.h>
#include <jail.h>
extern char jail_errmsg[];
int
jail_getid(const char *name);
char *
jail_getname(int jid);
int
jail_setv(int flags, ...);
int
jail_getv(int flags, ...);
int
jailparam_all(struct jailparam **jpp);
int
jailparam_init(struct jailparam *jp, const char *name);
int
jailparam_import(struct jailparam *jp, const char *value);
int
jailparam_import_raw(struct jailparam *jp, void *value, size_t valuelen);
int
jailparam_set(struct jailparam *jp, unsigned njp, int flags);
int
jailparam_get(struct jailparam *jp, unsigned njp, int flags);
char *
jailparam_export(struct jailparam *jp);
void
jailparam_free(struct jailparam *jp, unsigned njp);

DESCRIPTION
The jail library is an interface to the jail_set(2) and jail_get(2) system calls, and the 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.

The jail_getid() function returns the JID of the jail identified by name, or -1 if the jail does not exist.

The jail_getname() function returns the name of the jail identified by jid, or NULL if the jail does not exist.

The jail_setv() function takes a null-terminated list of name and value strings, and passes it to jail_set(2).

The jail_getv() function takes a null-terminated list of name and value strings, and passes it to 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.

The jailparam_all() function sets jpp to a list of all known jail parameters, and returns the number of parameters. The list should later be freed with jailparam_free() and free(3).

The jailparam_init() function clears a parameter record and copies the name to it. After use, it should be freed with jailparam_free().

The jailparam_import() function adds a value to a parameter record, converting it from a string to its native form. The jailparam_import_raw() function adds a value without performing any conversion.

The jailparam_set() function passes a list of parameters to jail_set(2). The parameters are assumed to have been created with jailparam_init() and jailparam_import().

The jailparam_get() function passes a list of parameters to jail_get(2). The parameters are assumed to have been created with jailparam_init() or jailparam_list(), with one parameter (the key) having been given a value with jailparam_import().

The jailparam_export() function returns the string equivalent of a parameter value. The returned string should be freed after use.

The jailparam_free() function frees the stored names and values in a parameter list. If the list itself came from jailparam_all(), it should be freed as well.

RETURN VALUES
The jail_getid(), jail_setv(), jail_getv(), jailparam_set() and jailparam_get() functions return a JID on success, or -1 on error.

The jail_getname() and jailparam_export() functions return a dynamically allocated string on success, or NULL on error.

The jailparam_all() function returns the number of parameters on success, or -1 on error.

The jailparam_init(), jailparam_import() and jailparam_import_raw() functions return 0 on success, or -1 on error.

Whenever an error is returned, errno is set, and the global string jail_errmsg contains a description of the error, possibly from jail_set(2) or jail_get(2).

EXAMPLES
Set the hostname of jail “foo” to “foo.bar”:

    jail_setv(JAIL_UPDATE, "name", "foo", "host.hostname", "foo.bar",
        NULL);

OR:

    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);

Retrieve the hostname of jail “foo”:

    char hostname[MAXHOSTNAMELEN];
    jail_getv(0, "name", "foo", "host.hostname", hostname, NULL);

OR:

    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);

ERRORS
The jail functions may return errors from jail_set(2), jail_get(2), malloc(3) or sysctl(3). In addition, the following errors are possible:

[EINVAL]
    A parameter value cannot be converted from the passed string to its internal form.

[ENOENT]
    The named parameter does not exist.

[ENOENT]
    A parameter is of an unknown type.

SEE ALSO
jail(2), sysctl(3), jail(8)

HISTORY
The jail library first appeared in FreeBSD 8.0.

AUTHORS
James Gritton