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/* SPDX-License-Identifier: LGPL-2.1+ */
#include <errno.h>
#include <poll.h>
#include "libudev.h"
#include "alloc-util.h"
#include "device-monitor-private.h"
#include "device-private.h"
#include "device-util.h"
#include "libudev-device-internal.h"
#include "string-util.h"
/**
* SECTION:libudev-monitor
* @short_description: device event source
*
* Connects to a device event source.
*/
/**
* udev_monitor:
*
* Opaque object handling an event source.
*/
struct udev_monitor {
struct udev *udev;
unsigned n_ref;
sd_device_monitor *monitor;
};
static MonitorNetlinkGroup monitor_netlink_group_from_string(const char *name) {
if (!name)
return MONITOR_GROUP_NONE;
if (streq(name, "udev"))
return MONITOR_GROUP_UDEV;
if (streq(name, "kernel"))
return MONITOR_GROUP_KERNEL;
return _MONITOR_NETLINK_GROUP_INVALID;
}
/**
* udev_monitor_new_from_netlink:
* @udev: udev library context
* @name: name of event source
*
* Create new udev monitor and connect to a specified event
* source. Valid sources identifiers are "udev" and "kernel".
*
* Applications should usually not connect directly to the
* "kernel" events, because the devices might not be useable
* at that time, before udev has configured them, and created
* device nodes. Accessing devices at the same time as udev,
* might result in unpredictable behavior. The "udev" events
* are sent out after udev has finished its event processing,
* all rules have been processed, and needed device nodes are
* created.
*
* The initial refcount is 1, and needs to be decremented to
* release the resources of the udev monitor.
*
* Returns: a new udev monitor, or #NULL, in case of an error
**/
_public_ struct udev_monitor *udev_monitor_new_from_netlink(struct udev *udev, const char *name) {
_cleanup_(sd_device_monitor_unrefp) sd_device_monitor *m = NULL;
struct udev_monitor *udev_monitor;
MonitorNetlinkGroup g;
int r;
g = monitor_netlink_group_from_string(name);
if (g < 0) {
errno = EINVAL;
return NULL;
}
r = device_monitor_new_full(&m, g, -1);
if (r < 0) {
errno = -r;
return NULL;
}
udev_monitor = new(struct udev_monitor, 1);
if (!udev_monitor) {
errno = ENOMEM;
return NULL;
}
*udev_monitor = (struct udev_monitor) {
.udev = udev,
.n_ref = 1,
.monitor = TAKE_PTR(m),
};
return udev_monitor;
}
/**
* udev_monitor_filter_update:
* @udev_monitor: monitor
*
* Update the installed socket filter. This is only needed,
* if the filter was removed or changed.
*
* Returns: 0 on success, otherwise a negative error value.
*/
_public_ int udev_monitor_filter_update(struct udev_monitor *udev_monitor) {
assert_return(udev_monitor, -EINVAL);
return sd_device_monitor_filter_update(udev_monitor->monitor);
}
/**
* udev_monitor_enable_receiving:
* @udev_monitor: the monitor which should receive events
*
* Binds the @udev_monitor socket to the event source.
*
* Returns: 0 on success, otherwise a negative error value.
*/
_public_ int udev_monitor_enable_receiving(struct udev_monitor *udev_monitor) {
assert_return(udev_monitor, -EINVAL);
return device_monitor_enable_receiving(udev_monitor->monitor);
}
/**
* udev_monitor_set_receive_buffer_size:
* @udev_monitor: the monitor which should receive events
* @size: the size in bytes
*
* Set the size of the kernel socket buffer. This call needs the
* appropriate privileges to succeed.
*
* Returns: 0 on success, otherwise -1 on error.
*/
_public_ int udev_monitor_set_receive_buffer_size(struct udev_monitor *udev_monitor, int size) {
assert_return(udev_monitor, -EINVAL);
return sd_device_monitor_set_receive_buffer_size(udev_monitor->monitor, (size_t) size);
}
static struct udev_monitor *udev_monitor_free(struct udev_monitor *udev_monitor) {
assert(udev_monitor);
sd_device_monitor_unref(udev_monitor->monitor);
return mfree(udev_monitor);
}
/**
* udev_monitor_ref:
* @udev_monitor: udev monitor
*
* Take a reference of a udev monitor.
*
* Returns: the passed udev monitor
**/
/**
* udev_monitor_unref:
* @udev_monitor: udev monitor
*
* Drop a reference of a udev monitor. If the refcount reaches zero,
* the bound socket will be closed, and the resources of the monitor
* will be released.
*
* Returns: #NULL
**/
DEFINE_PUBLIC_TRIVIAL_REF_UNREF_FUNC(struct udev_monitor, udev_monitor, udev_monitor_free);
/**
* udev_monitor_get_udev:
* @udev_monitor: udev monitor
*
* Retrieve the udev library context the monitor was created with.
*
* Returns: the udev library context
**/
_public_ struct udev *udev_monitor_get_udev(struct udev_monitor *udev_monitor) {
assert_return(udev_monitor, NULL);
return udev_monitor->udev;
}
/**
* udev_monitor_get_fd:
* @udev_monitor: udev monitor
*
* Retrieve the socket file descriptor associated with the monitor.
*
* Returns: the socket file descriptor
**/
_public_ int udev_monitor_get_fd(struct udev_monitor *udev_monitor) {
assert_return(udev_monitor, -EINVAL);
return device_monitor_get_fd(udev_monitor->monitor);
}
static int udev_monitor_receive_sd_device(struct udev_monitor *udev_monitor, sd_device **ret) {
struct pollfd pfd;
int r;
assert(udev_monitor);
assert(ret);
pfd = (struct pollfd) {
.fd = device_monitor_get_fd(udev_monitor->monitor),
.events = POLLIN,
};
for (;;) {
/* r == 0 means a device is received but it does not pass the current filter. */
r = device_monitor_receive_device(udev_monitor->monitor, ret);
if (r != 0)
return r;
for (;;) {
/* wait next message */
r = poll(&pfd, 1, 0);
if (r < 0) {
if (IN_SET(errno, EINTR, EAGAIN))
continue;
return -errno;
} else if (r == 0)
return -EAGAIN;
/* receive next message */
break;
}
}
}
/**
* udev_monitor_receive_device:
* @udev_monitor: udev monitor
*
* Receive data from the udev monitor socket, allocate a new udev
* device, fill in the received data, and return the device.
*
* Only socket connections with uid=0 are accepted.
*
* The monitor socket is by default set to NONBLOCK. A variant of poll() on
* the file descriptor returned by udev_monitor_get_fd() should to be used to
* wake up when new devices arrive, or alternatively the file descriptor
* switched into blocking mode.
*
* The initial refcount is 1, and needs to be decremented to
* release the resources of the udev device.
*
* Returns: a new udev device, or #NULL, in case of an error
**/
_public_ struct udev_device *udev_monitor_receive_device(struct udev_monitor *udev_monitor) {
_cleanup_(sd_device_unrefp) sd_device *device = NULL;
int r;
assert_return(udev_monitor, NULL);
r = udev_monitor_receive_sd_device(udev_monitor, &device);
if (r < 0) {
errno = -r;
return NULL;
}
return udev_device_new(udev_monitor->udev, device);
}
/**
* udev_monitor_filter_add_match_subsystem_devtype:
* @udev_monitor: the monitor
* @subsystem: the subsystem value to match the incoming devices against
* @devtype: the devtype value to match the incoming devices against
*
* This filter is efficiently executed inside the kernel, and libudev subscribers
* will usually not be woken up for devices which do not match.
*
* The filter must be installed before the monitor is switched to listening mode.
*
* Returns: 0 on success, otherwise a negative error value.
*/
_public_ int udev_monitor_filter_add_match_subsystem_devtype(struct udev_monitor *udev_monitor, const char *subsystem, const char *devtype) {
assert_return(udev_monitor, -EINVAL);
return sd_device_monitor_filter_add_match_subsystem_devtype(udev_monitor->monitor, subsystem, devtype);
}
/**
* udev_monitor_filter_add_match_tag:
* @udev_monitor: the monitor
* @tag: the name of a tag
*
* This filter is efficiently executed inside the kernel, and libudev subscribers
* will usually not be woken up for devices which do not match.
*
* The filter must be installed before the monitor is switched to listening mode.
*
* Returns: 0 on success, otherwise a negative error value.
*/
_public_ int udev_monitor_filter_add_match_tag(struct udev_monitor *udev_monitor, const char *tag) {
assert_return(udev_monitor, -EINVAL);
return sd_device_monitor_filter_add_match_tag(udev_monitor->monitor, tag);
}
/**
* udev_monitor_filter_remove:
* @udev_monitor: monitor
*
* Remove all filters from monitor.
*
* Returns: 0 on success, otherwise a negative error value.
*/
_public_ int udev_monitor_filter_remove(struct udev_monitor *udev_monitor) {
assert_return(udev_monitor, -EINVAL);
return sd_device_monitor_filter_remove(udev_monitor->monitor);
}
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