systemd/libudev/libudev.c

/*
 * libudev - interface to udev device information
 *
 * Copyright (C) 2008-2010 Kay Sievers <kay.sievers@vrfy.org>
 *
 * 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 <stdarg.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <ctype.h>

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

/**
 * SECTION:libudev
 * @short_description: libudev context
 *
 * The context contains the default values read from the udev config file,
 * and is passed to all library operations.
 */

/**
 * udev:
 *
 * Opaque object representing the library context.
 */
struct udev {
	int refcount;
	void (*log_fn)(struct udev *udev,
		       int priority, const char *file, int line, const char *fn,
		       const char *format, va_list args);
	void *userdata;
	char *sys_path;
	char *dev_path;
	char *rules_path;
	char *run_config_path;
	char *run_path;
	struct udev_list_node properties_list;
	int log_priority;
};

void udev_log(struct udev *udev,
	      int priority, const char *file, int line, const char *fn,
	      const char *format, ...)
{
	va_list args;

	va_start(args, format);
	udev->log_fn(udev, priority, file, line, fn, format, args);
	va_end(args);
}

static void log_stderr(struct udev *udev,
		       int priority, const char *file, int line, const char *fn,
		       const char *format, va_list args)
{
	fprintf(stderr, "libudev: %s: ", fn);
	vfprintf(stderr, format, args);
}

/**
 * udev_get_userdata:
 * @udev: udev library context
 *
 * Retrieve stored data pointer from library context. This might be useful
 * to access from callbacks like a custom logging function.
 *
 * Returns: stored userdata
 **/
void *udev_get_userdata(struct udev *udev)
{
	if (udev == NULL)
		return NULL;
	return udev->userdata;
}

/**
 * udev_set_userdata:
 * @udev: udev library context
 * @userdata: data pointer
 *
 * Store custom @userdata in the library context.
 **/
void udev_set_userdata(struct udev *udev, void *userdata)
{
	if (udev == NULL)
		return;
	udev->userdata = userdata;
}

static char *set_value(char **s, const char *v)
{
	free(*s);
	*s = strdup(v);
	util_remove_trailing_chars(*s, '/');
	return *s;
}

/**
 * udev_new:
 *
 * Create udev library context. This reads the udev configuration
 * file, and fills in the default values.
 *
 * The initial refcount is 1, and needs to be decremented to
 * release the resources of the udev library context.
 *
 * Returns: a new udev library context
 **/
struct udev *udev_new(void)
{
	struct udev *udev;
	const char *env;
	char *config_file = NULL;
	FILE *f;

	udev = calloc(1, sizeof(struct udev));
	if (udev == NULL)
		return NULL;
	udev->refcount = 1;
	udev->log_fn = log_stderr;
	udev->log_priority = LOG_ERR;
	udev_list_init(&udev->properties_list);

	/* custom config file */
	env = getenv("UDEV_CONFIG_FILE");
	if (env != NULL) {
		udev_add_property(udev, "UDEV_CONFIG_FILE", udev->dev_path);
		if (set_value(&config_file, env) == NULL)
			goto err;
	}

	/* default config file */
	if (config_file == NULL)
		config_file = strdup(SYSCONFDIR "/udev/udev.conf");
	if (config_file == NULL)
		goto err;

	f = fopen(config_file, "re");
	if (f != NULL) {
		char line[UTIL_LINE_SIZE];
		int line_nr = 0;

		while (fgets(line, sizeof(line), f)) {
			size_t len;
			char *key;
			char *val;

			line_nr++;

			/* find key */
			key = line;
			while (isspace(key[0]))
				key++;

			/* comment or empty line */
			if (key[0] == '#' || key[0] == '\0')
				continue;

			/* split key/value */
			val = strchr(key, '=');
			if (val == NULL) {
				err(udev, "missing <key>=<value> in '%s'[%i], skip line\n", config_file, line_nr);
				continue;
			}
			val[0] = '\0';
			val++;

			/* find value */
			while (isspace(val[0]))
				val++;

			/* terminate key */
			len = strlen(key);
			if (len == 0)
				continue;
			while (isspace(key[len-1]))
				len--;
			key[len] = '\0';

			/* terminate value */
			len = strlen(val);
			if (len == 0)
				continue;
			while (isspace(val[len-1]))
				len--;
			val[len] = '\0';

			if (len == 0)
				continue;

			/* unquote */
			if (val[0] == '"' || val[0] == '\'') {
				if (val[len-1] != val[0]) {
					err(udev, "inconsistent quoting in '%s'[%i], skip line\n", config_file, line_nr);
					continue;
				}
				val[len-1] = '\0';
				val++;
			}

			if (strcmp(key, "udev_log") == 0) {
				udev_set_log_priority(udev, util_log_priority(val));
				continue;
			}
			if (strcmp(key, "udev_root") == 0) {
				set_value(&udev->dev_path, val);
				continue;
			}
			if (strcmp(key, "udev_run") == 0) {
				set_value(&udev->run_config_path, val);
				continue;
			}
			if (strcmp(key, "udev_rules") == 0) {
				set_value(&udev->rules_path, val);
				continue;
			}
		}
		fclose(f);
	}

	/* environment overwrites config */
	env = getenv("UDEV_LOG");
	if (env != NULL)
		udev_set_log_priority(udev, util_log_priority(env));

	env = getenv("UDEV_ROOT");
	if (env != NULL) {
		set_value(&udev->dev_path, env);
		udev_add_property(udev, "UDEV_ROOT", udev->dev_path);
	}

	env = getenv("SYSFS_PATH");
	if (env != NULL) {
		set_value(&udev->sys_path, env);
		udev_add_property(udev, "SYSFS_PATH", udev->sys_path);
	}

	/* set defaults */
	if (udev->dev_path == NULL)
		if (set_value(&udev->dev_path, "/dev") == NULL)
			goto err;

	if (udev->sys_path == NULL)
		if (set_value(&udev->sys_path, "/sys") == NULL)
			goto err;

	if (udev->run_config_path == NULL)
		if (set_value(&udev->run_config_path, "/run/udev") == NULL)
			goto err;

	dbg(udev, "context %p created\n", udev);
	dbg(udev, "log_priority=%d\n", udev->log_priority);
	dbg(udev, "config_file='%s'\n", config_file);
	dbg(udev, "dev_path='%s'\n", udev->dev_path);
	dbg(udev, "sys_path='%s'\n", udev->sys_path);
	dbg(udev, "run_path='%s'\n", udev->run_config_path);
	if (udev->rules_path != NULL)
		dbg(udev, "rules_path='%s'\n", udev->rules_path);
	free(config_file);
	return udev;
err:
	free(config_file);
	err(udev, "context creation failed\n");
	udev_unref(udev);
	return NULL;
}

/**
 * udev_ref:
 * @udev: udev library context
 *
 * Take a reference of the udev library context.
 *
 * Returns: the passed udev library context
 **/
struct udev *udev_ref(struct udev *udev)
{
	if (udev == NULL)
		return NULL;
	udev->refcount++;
	return udev;
}

/**
 * udev_unref:
 * @udev: udev library context
 *
 * Drop a reference of the udev library context. If the refcount
 * reaches zero, the resources of the context will be released.
 *
 **/
void udev_unref(struct udev *udev)
{
	if (udev == NULL)
		return;
	udev->refcount--;
	if (udev->refcount > 0)
		return;
	udev_list_cleanup_entries(udev, &udev->properties_list);
	free(udev->dev_path);
	free(udev->sys_path);
	free(udev->rules_path);
	free(udev->run_path);
	free(udev->run_config_path);
	dbg(udev, "context %p released\n", udev);
	free(udev);
}

/**
 * udev_set_log_fn:
 * @udev: udev library context
 * @log_fn: function to be called for logging messages
 *
 * The built-in logging writes to stderr. It can be
 * overridden by a custom function, to plug log messages
 * into the users' logging functionality.
 *
 **/
void udev_set_log_fn(struct udev *udev,
		     void (*log_fn)(struct udev *udev,
				    int priority, const char *file, int line, const char *fn,
				    const char *format, va_list args))
{
	udev->log_fn = log_fn;
	info(udev, "custom logging function %p registered\n", udev);
}

/**
 * udev_get_log_priority:
 * @udev: udev library context
 *
 * The initial logging priority is read from the udev config file
 * at startup.
 *
 * Returns: the current logging priority
 **/
int udev_get_log_priority(struct udev *udev)
{
	return udev->log_priority;
}

/**
 * udev_set_log_priority:
 * @udev: udev library context
 * @priority: the new logging priority
 *
 * Set the current logging priority. The value controls which messages
 * are logged.
 **/
void udev_set_log_priority(struct udev *udev, int priority)
{
	char num[32];

	udev->log_priority = priority;
	snprintf(num, sizeof(num), "%u", udev->log_priority);
	udev_add_property(udev, "UDEV_LOG", num);
}

const char *udev_get_rules_path(struct udev *udev)
{
	return udev->rules_path;
}

/**
 * udev_get_sys_path:
 * @udev: udev library context
 *
 * Retrieve the sysfs mount point. The default is "/sys". For
 * testing purposes, it can be overridden with the environment
 * variable SYSFS_PATH.
 *
 * Returns: the sys mount point
 **/
const char *udev_get_sys_path(struct udev *udev)
{
	if (udev == NULL)
		return NULL;
	return udev->sys_path;
}

/**
 * udev_get_dev_path:
 * @udev: udev library context
 *
 * Retrieve the device directory path. The default value is "/dev",
 * the actual value may be overridden in the udev configuration
 * file.
 *
 * Returns: the device directory path
 **/
const char *udev_get_dev_path(struct udev *udev)
{
	if (udev == NULL)
		return NULL;
	return udev->dev_path;
}

const char *udev_get_run_config_path(struct udev *udev)
{
	return udev->run_config_path;
}

/**
 * udev_get_run_path:
 * @udev: udev library context
 *
 * Retrieve the udev runtime directory path. The default is "/run/udev".
 *
 * Returns: the runtime directory path
 **/
const char *udev_get_run_path(struct udev *udev)
{
	if (udev->run_path != NULL)
		return udev->run_path;

	/* check if configured path exists */
	if (access(udev->run_config_path, F_OK) < 0) {
		char filename[UTIL_PATH_SIZE];

		/* fall back to /dev/.udev if that exists */
		util_strscpyl(filename, sizeof(filename), udev_get_dev_path(udev), "/.udev", NULL);
		if (access(filename, F_OK) >= 0)
			if (set_value(&udev->run_path, filename) != NULL)
				return udev->run_path;
	}

	/* use default path */
	set_value(&udev->run_path, udev->run_config_path);
	if (udev->run_path == NULL)
		return udev->run_config_path;
	return udev->run_path;
}

const char *udev_set_run_path(struct udev *udev, const char *path)
{
	return set_value(&udev->run_path, path);
}

struct udev_list_entry *udev_add_property(struct udev *udev, const char *key, const char *value)
{
	if (value == NULL) {
		struct udev_list_entry *list_entry;

		list_entry = udev_get_properties_list_entry(udev);
		list_entry = udev_list_entry_get_by_name(list_entry, key);
		if (list_entry != NULL)
			udev_list_entry_delete(list_entry);
		return NULL;
	}
	return udev_list_entry_add(udev, &udev->properties_list, key, value, 1, 0);
}

struct udev_list_entry *udev_get_properties_list_entry(struct udev *udev)
{
	return udev_list_get_entry(&udev->properties_list);
}