systemd/libudev/libudev-queue.c

/*
 * libudev - interface to udev device information
 *
 * Copyright (C) 2008 Kay Sievers <kay.sievers@vrfy.org>
 * Copyright (C) 2009 Alan Jenkins <alan-jenkins@tuffmail.co.uk>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 */

#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <dirent.h>
#include <fcntl.h>
#include <limits.h>
#include <sys/stat.h>

#include "libudev.h"
#include "libudev-private.h"

/**
 * SECTION:libudev-queue
 * @short_description: access to currently active events
 *
 * The udev daemon processes events asynchronously. All events which do not have
 * interdependencies run in parallel. This exports the current state of the
 * event processing queue, and the current event sequence numbers from the kernel
 * and the udev daemon.
 */

/**
 * udev_queue:
 *
 * Opaque object representing the current event queue in the udev daemon.
 */
struct udev_queue {
	struct udev *udev;
	int refcount;
	struct udev_list_node queue_list;
	struct udev_list_node failed_list;
};

/**
 * udev_queue_new:
 * @udev: udev library context
 *
 * The initial refcount is 1, and needs to be decremented to
 * release the resources of the udev queue context.
 *
 * Returns: the udev queue context, or #NULL on error.
 **/
struct udev_queue *udev_queue_new(struct udev *udev)
{
	struct udev_queue *udev_queue;

	if (udev == NULL)
		return NULL;

	udev_queue = calloc(1, sizeof(struct udev_queue));
	if (udev_queue == NULL)
		return NULL;
	udev_queue->refcount = 1;
	udev_queue->udev = udev;
	udev_list_init(&udev_queue->queue_list);
	udev_list_init(&udev_queue->failed_list);
	return udev_queue;
}

/**
 * udev_queue_ref:
 * @udev_queue: udev queue context
 *
 * Take a reference of a udev queue context.
 *
 * Returns: the same udev queue context.
 **/
struct udev_queue *udev_queue_ref(struct udev_queue *udev_queue)
{
	if (udev_queue == NULL)
		return NULL;
	udev_queue->refcount++;
	return udev_queue;
}

/**
 * udev_queue_unref:
 * @udev_queue: udev queue context
 *
 * Drop a reference of a udev queue context. If the refcount reaches zero,
 * the resources of the queue context will be released.
 **/
void udev_queue_unref(struct udev_queue *udev_queue)
{
	if (udev_queue == NULL)
		return;
	udev_queue->refcount--;
	if (udev_queue->refcount > 0)
		return;
	udev_list_cleanup_entries(udev_queue->udev, &udev_queue->queue_list);
	udev_list_cleanup_entries(udev_queue->udev, &udev_queue->failed_list);
	free(udev_queue);
}

/**
 * udev_queue_get_udev:
 * @udev_queue: udev queue context
 *
 * Retrieve the udev library context the queue context was created with.
 *
 * Returns: the udev library context.
 **/
struct udev *udev_queue_get_udev(struct udev_queue *udev_queue)
{
	if (udev_queue == NULL)
		return NULL;
	return udev_queue->udev;
}

unsigned long long int udev_get_kernel_seqnum(struct udev *udev)
{
	char filename[UTIL_PATH_SIZE];
	unsigned long long int seqnum;
	int fd;
	char buf[32];
	ssize_t len;

	util_strscpyl(filename, sizeof(filename), udev_get_sys_path(udev), "/kernel/uevent_seqnum", NULL);
	fd = open(filename, O_RDONLY|O_CLOEXEC);
	if (fd < 0)
		return 0;
	len = read(fd, buf, sizeof(buf));
	close(fd);
	if (len <= 2)
		return 0;
	buf[len-1] = '\0';
	seqnum = strtoull(buf, NULL, 10);
	return seqnum;
}

/**
 * udev_queue_get_kernel_seqnum:
 * @udev_queue: udev queue context
 *
 * Returns: the current kernel event sequence number.
 **/
unsigned long long int udev_queue_get_kernel_seqnum(struct udev_queue *udev_queue)
{
	unsigned long long int seqnum;

	if (udev_queue == NULL)
		return -EINVAL;

	seqnum = udev_get_kernel_seqnum(udev_queue->udev);
	dbg(udev_queue->udev, "seqnum=%llu\n", seqnum);
	return seqnum;
}

int udev_queue_read_seqnum(FILE *queue_file, unsigned long long int *seqnum)
{
	if (fread(seqnum, sizeof(unsigned long long int), 1, queue_file) != 1)
		return -1;

	return 0;
}

ssize_t udev_queue_skip_devpath(FILE *queue_file)
{
	unsigned short int len;

	if (fread(&len, sizeof(unsigned short int), 1, queue_file) == 1) {
		char devpath[len];

		/* use fread to skip, fseek might drop buffered data */
		if (fread(devpath, 1, len, queue_file) == len)
			return len;
	}

	return -1;
}

ssize_t udev_queue_read_devpath(FILE *queue_file, char *devpath, size_t size)
{
	unsigned short int read_bytes = 0;
	unsigned short int len;

	if (fread(&len, sizeof(unsigned short int), 1, queue_file) != 1)
		return -1;

	read_bytes = (len < size - 1) ? len : size - 1;
	if (fread(devpath, 1, read_bytes, queue_file) != read_bytes)
		return -1;
	devpath[read_bytes] = '\0';

	/* if devpath was too long, skip unread characters */
	if (read_bytes != len) {
		unsigned short int skip_bytes = len - read_bytes;
		char buf[skip_bytes];

		if (fread(buf, 1, skip_bytes, queue_file) != skip_bytes)
			return -1;
	}

	return read_bytes;
}

static FILE *open_queue_file(struct udev_queue *udev_queue, unsigned long long int *seqnum_start)
{
	char filename[UTIL_PATH_SIZE];
	FILE *queue_file;

	util_strscpyl(filename, sizeof(filename), udev_get_dev_path(udev_queue->udev), "/.udev/queue.bin", NULL);
	queue_file = fopen(filename, "re");
	if (queue_file == NULL)
		return NULL;

	if (udev_queue_read_seqnum(queue_file, seqnum_start) < 0) {
		err(udev_queue->udev, "corrupt queue file\n");
		fclose(queue_file);
		return NULL;
	}

	return queue_file;
}

/**
 * udev_queue_get_udev_seqnum:
 * @udev_queue: udev queue context
 *
 * Returns: the last known udev event sequence number.
 **/
unsigned long long int udev_queue_get_udev_seqnum(struct udev_queue *udev_queue)
{
	unsigned long long int seqnum_udev;
	FILE *queue_file;

	queue_file = open_queue_file(udev_queue, &seqnum_udev);
	if (queue_file == NULL)
		return 0;

	for (;;) {
		unsigned long long int seqnum;
		ssize_t devpath_len;

		if (udev_queue_read_seqnum(queue_file, &seqnum) < 0)
			break;
		devpath_len = udev_queue_skip_devpath(queue_file);
		if (devpath_len < 0)
			break;
		if (devpath_len > 0)
			seqnum_udev = seqnum;
	}

	fclose(queue_file);
	return seqnum_udev;
}

/**
 * udev_queue_get_udev_is_active:
 * @udev_queue: udev queue context
 *
 * Returns: a flag indicating if udev is active.
 **/
int udev_queue_get_udev_is_active(struct udev_queue *udev_queue)
{
	unsigned long long int seqnum_start;
	FILE *queue_file;

	queue_file = open_queue_file(udev_queue, &seqnum_start);
	if (queue_file == NULL)
		return 0;

	fclose(queue_file);
	return 1;
}

/**
 * udev_queue_get_queue_is_empty:
 * @udev_queue: udev queue context
 *
 * Returns: a flag indicating if udev is currently handling events.
 **/
int udev_queue_get_queue_is_empty(struct udev_queue *udev_queue)
{
	unsigned long long int seqnum_kernel;
	unsigned long long int seqnum_udev = 0;
	int queued = 0;
	int is_empty = 0;
	FILE *queue_file;

	if (udev_queue == NULL)
		return -EINVAL;
	queue_file = open_queue_file(udev_queue, &seqnum_udev);
	if (queue_file == NULL)
		return 1;

	for (;;) {
		unsigned long long int seqnum;
		ssize_t devpath_len;

		if (udev_queue_read_seqnum(queue_file, &seqnum) < 0)
			break;
		devpath_len = udev_queue_skip_devpath(queue_file);
		if (devpath_len < 0)
			break;

		if (devpath_len > 0) {
			queued++;
			seqnum_udev = seqnum;
		} else {
			queued--;
		}
	}

	if (queued > 0) {
		dbg(udev_queue->udev, "queue is not empty\n");
		goto out;
	}

	seqnum_kernel = udev_queue_get_kernel_seqnum(udev_queue);
	if (seqnum_udev < seqnum_kernel) {
		dbg(udev_queue->udev, "queue is empty but kernel events still pending [%llu]<->[%llu]\n",
					seqnum_kernel, seqnum_udev);
		goto out;
	}

	dbg(udev_queue->udev, "queue is empty\n");
	is_empty = 1;

out:
	fclose(queue_file);
	return is_empty;
}

/**
 * udev_queue_get_seqnum_sequence_is_finished:
 * @udev_queue: udev queue context
 * @start: first event sequence number
 * @end: last event sequence number
 *
 * Returns: if any of the sequence numbers in the given range is currently active.
 **/
int udev_queue_get_seqnum_sequence_is_finished(struct udev_queue *udev_queue,
					       unsigned long long int start, unsigned long long int end)
{
	unsigned long long int seqnum;
	ssize_t devpath_len;
	int unfinished;
	FILE *queue_file;

	if (udev_queue == NULL)
		return -EINVAL;
	queue_file = open_queue_file(udev_queue, &seqnum);
	if (queue_file == NULL)
		return 1;
	if (start < seqnum)
		start = seqnum;
	if (start > end) {
		fclose(queue_file);
		return 1;
	}
	if (end - start > INT_MAX - 1) {
		fclose(queue_file);
		return -EOVERFLOW;
	}

	/*
	 * we might start with 0, and handle the initial seqnum
	 * only when we find an entry in the queue file
	 **/
	unfinished = end - start;

	do {
		if (udev_queue_read_seqnum(queue_file, &seqnum) < 0)
			break;
		devpath_len = udev_queue_skip_devpath(queue_file);
		if (devpath_len < 0)
			break;

		/*
		 * we might start with an empty or re-build queue file, where
		 * the initial seqnum is not recorded as finished
		 */
		if (start == seqnum && devpath_len > 0)
			unfinished++;

		if (devpath_len == 0) {
			if (seqnum >= start && seqnum <= end)
				unfinished--;
		}
	} while (unfinished > 0);

	fclose(queue_file);

	return (unfinished == 0);
}

/**
 * udev_queue_get_seqnum_is_finished:
 * @udev_queue: udev queue context
 * @seqnum: sequence number
 *
 * Returns: a flag indicating if the given sequence number is handled.
 **/
int udev_queue_get_seqnum_is_finished(struct udev_queue *udev_queue, unsigned long long int seqnum)
{
	if (!udev_queue_get_seqnum_sequence_is_finished(udev_queue, seqnum, seqnum))
		return 0;

	dbg(udev_queue->udev, "seqnum: %llu finished\n", seqnum);
	return 1;
}

/**
 * udev_queue_get_queued_list_entry:
 * @udev_queue: udev queue context
 *
 * Returns: the first entry of the list of queued events.
 **/
struct udev_list_entry *udev_queue_get_queued_list_entry(struct udev_queue *udev_queue)
{
	unsigned long long int seqnum;
	FILE *queue_file;

	if (udev_queue == NULL)
		return NULL;
	udev_list_cleanup_entries(udev_queue->udev, &udev_queue->queue_list);

	queue_file = open_queue_file(udev_queue, &seqnum);
	if (queue_file == NULL)
		return NULL;

	for (;;) {
		char syspath[UTIL_PATH_SIZE];
		char *s;
		size_t l;
		ssize_t len;
		char seqnum_str[32];
		struct udev_list_entry *list_entry;

		if (udev_queue_read_seqnum(queue_file, &seqnum) < 0)
			break;
		snprintf(seqnum_str, sizeof(seqnum_str), "%llu", seqnum);

		s = syspath;
		l = util_strpcpyl(&s, sizeof(syspath), udev_get_sys_path(udev_queue->udev), NULL);
		len = udev_queue_read_devpath(queue_file, s, l);
		if (len < 0)
			break;

		if (len > 0) {
			udev_list_entry_add(udev_queue->udev, &udev_queue->queue_list, syspath, seqnum_str, 0, 0);
		} else {
			udev_list_entry_foreach(list_entry, udev_list_get_entry(&udev_queue->queue_list)) {
				if (strcmp(seqnum_str, udev_list_entry_get_value(list_entry)) == 0) {
					udev_list_entry_delete(list_entry);
					break;
				}
			}
		}
	}
	fclose(queue_file);

	return udev_list_get_entry(&udev_queue->queue_list);
}

/**
 * udev_queue_get_failed_list_entry:
 * @udev_queue: udev queue context
 *
 * Returns: the first entry of the list of recorded failed events.
 **/
struct udev_list_entry *udev_queue_get_failed_list_entry(struct udev_queue *udev_queue)
{
	char path[UTIL_PATH_SIZE];
	DIR *dir;
	struct dirent *dent;

	if (udev_queue == NULL)
		return NULL;
	udev_list_cleanup_entries(udev_queue->udev, &udev_queue->failed_list);
	util_strscpyl(path, sizeof(path), udev_get_dev_path(udev_queue->udev), "/.udev/failed", NULL);
	dir = opendir(path);
	if (dir == NULL)
		return NULL;
	for (dent = readdir(dir); dent != NULL; dent = readdir(dir)) {
		char filename[UTIL_PATH_SIZE];
		char syspath[UTIL_PATH_SIZE];
		char *s;
		size_t l;
		ssize_t len;
		struct stat statbuf;

		if (dent->d_name[0] == '.')
			continue;
		s = syspath;
		l = util_strpcpyl(&s, sizeof(syspath), udev_get_sys_path(udev_queue->udev), NULL);
		len = readlinkat(dirfd(dir), dent->d_name, s, l);
		if (len <= 0 || (size_t)len == l)
			continue;
		s[len] = '\0';
		dbg(udev_queue->udev, "found '%s' [%s]\n", syspath, dent->d_name);
		util_strscpyl(filename, sizeof(filename), syspath, "/uevent", NULL);
		if (stat(filename, &statbuf) != 0)
			continue;
		udev_list_entry_add(udev_queue->udev, &udev_queue->failed_list, syspath, NULL, 0, 0);
	}
	closedir(dir);
	return udev_list_get_entry(&udev_queue->failed_list);
}