apparmor/libraries/libapparmor/doc/aa_policy_cache.pod

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=pod

=head1 NAME

aa_policy_cache - an opaque object representing an AppArmor policy cache

aa_policy_cache_new - create a new aa_policy_cache object from a path

aa_policy_cache_ref - increments the ref count of an aa_policy_cache object

aa_policy_cache_unref - decrements the ref count and frees the aa_policy_cache object when 0

aa_policy_cache_remove - removes all policy cache files under a path

aa_policy_cache_replace_all - performs a kernel policy replacement of all cached policies

aa_policy_cache_dir_path - returns the path to the aa_policy_cache directory

aa_policy_cache_dir_path_preview - returns a preview of the path to the aa_policy_cache directory without an existing aa_policy_cache object

=head1 SYNOPSIS

B<#include E<lt>sys/apparmor.hE<gt>>

B<typedef struct aa_policy_cache aa_policy_cache;>

B<int aa_policy_cache_new(aa_policy_cache **policy_cache, aa_features *kernel_features, int dirfd, const char *path, uint16_t max_caches);>

B<aa_policy_cache *aa_policy_cache_ref(aa_policy_cache *policy_cache);>

B<void aa_policy_cache_unref(aa_policy_cache *policy_cache);>

B<int aa_policy_cache_remove(int dirfd, const char *path);>

B<int aa_policy_cache_replace_all(aa_policy_cache *policy_cache, aa_kernel_interface *kernel_interface);>

B<char *aa_policy_cache_dir_path(aa_policy_cache *policy_cache);>

B<char *aa_policy_cache_dir_path_preview(aa_features *kernel_features, int dirfd, const char *path);>

Link with B<-lapparmor> when compiling.

=head1 DESCRIPTION

The I<aa_policy_cache> object contains information about a set of AppArmor
policy cache files. The policy cache files are the binary representation of a
human-readable AppArmor profile. The binary representation is the form that is
loaded into the kernel.

The aa_policy_cache_new() function creates an I<aa_policy_cache> object based
upon a directory file descriptor and path. See the openat(2) man page for
examples of I<dirfd> and I<path>. The I<path> must point to a directory and it
will be used as the basis for the location of policy cache files. See
I<aa_policy_cache_dir_path> to find out which directory will be used to store
the binary policy cache files. If I<kernel_features> is NULL, then the features
of the current kernel are used. When specifying a valid I<kernel_features>
object, it must be the compatible with the features of the kernel of interest.
The value of I<max_caches> should be equal to the number of caches that should
be allowed before old caches are automatically reaped. The definition of what is
considered to be an old cache is private to libapparmor. Specifying 0 means that
no new caches should be created and only existing, valid caches may be used.
Specifying UINT16_MAX means that a new cache may be created and that the reaping
of old caches is disabled. The allocated I<aa_policy_cache> object must be freed
using aa_policy_cache_unref().

aa_policy_cache_ref() increments the reference count on the I<policy_cache>
object.

aa_policy_cache_unref() decrements the reference count on the I<policy_cache>
object and releases all corresponding resources when the reference count
reaches zero.

The aa_policy_cache_remove() function deletes all of the policy cache files
based upon a directory file descriptor and path. The I<path> must point to a 
directory. See the openat(2) man page for examples of I<dirfd> and I<path>.

The aa_policy_cache_replace_all() function can be used to perform a policy
replacement of all of the cache policies in the cache directory represented by
the I<policy_cache> object. If I<kernel_interface> is NULL, then the current
kernel interface is used. When specifying a valid I<kernel_interface> object,
it must be the interface of the currently running kernel.

The aa_policy_cache_dir_path() function provides the path to the cache directory
for a I<policy_cache> object. Binary policy cache files will be located in the
directory returned by this function.

=head1 RETURN VALUE

The aa_policy_cache_new() function returns 0 on success and I<*policy_cache>
will point to an I<aa_policy_cache> object that must be freed by
aa_policy_cache_unref(). -1 is returned on error, with errno set appropriately,
and I<*policy_cache> will be set to NULL.

aa_policy_cache_ref() returns the value of I<policy_cache>.

aa_policy_cache_remove() and aa_policy_cache_replace_all() return 0 on success.
-1 is returned on error, with errno set appropriately.

aa_policy_cache_dir_path() returns a path string which must be freed by the
caller. NULL is returned on error, with errnor set appropriately.

aa_policy_cache_dir_path_preview() is the same as
aa_policy_cache_dir_path() except that it doesn't require an existing
I<aa_policy_cache> object. This is useful if the calling program cannot
create an I<aa_policy_cache> object due to lack of privileges needed to
create the cache directory.

=head1 ERRORS

The errno value will be set according to the underlying error in the
I<aa_policy_cache> family of functions that return -1 or NULL on error.

=head1 NOTES

All aa_policy_cache functions described above, except for
aa_policy_cache_dir_path() and aa_policy_cache_dir_path_preview(), are
present in libapparmor version 2.10. The aa_policy_cache_dir_path() and
aa_policy_cache_dir_path_preview() functions can be found in libapparmor
version 2.12.

aa_policy_cache_unref() saves the value of errno when called and restores errno
before exiting in libapparmor version 2.12 and newer.

=head1 BUGS

None known. If you find any, please report them at
L<https://bugs.launchpad.net/apparmor/+filebug>.

=head1 SEE ALSO

aa_features(3), aa_kernel_interface(3), openat(2) and
L<http://wiki.apparmor.net>.

=cut