src/logging.c

/* Debugging/Logging support code */

/* (C) 2008-2010 by Harald Welte <laforge@gnumonks.org>
 * (C) 2008 by Holger Hans Peter Freyther <zecke@selfish.org>
 * All Rights Reserved
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 */

/* \addtogroup logging
 * @{
 */

/* \file logging.c */

#include "../config.h"

#include <stdarg.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>

#ifdef HAVE_STRINGS_H
#include <strings.h>
#endif
#include <time.h>
#include <sys/time.h>
#include <errno.h>

#include <osmocom/core/talloc.h>
#include <osmocom/core/utils.h>
#include <osmocom/core/logging.h>

#include <osmocom/vty/logging.h>	/* for LOGGING_STR. */

struct log_info *osmo_log_info;

static struct log_context log_context;
static void *tall_log_ctx = NULL;
LLIST_HEAD(osmo_log_target_list);

#define LOGLEVEL_DEFS	6	/* Number of loglevels.*/

static const struct value_string loglevel_strs[LOGLEVEL_DEFS+1] = {
	{ 0,		"EVERYTHING" },
	{ LOGL_DEBUG,	"DEBUG" },
	{ LOGL_INFO,	"INFO" },
	{ LOGL_NOTICE,	"NOTICE" },
	{ LOGL_ERROR,	"ERROR" },
	{ LOGL_FATAL,	"FATAL" },
	{ 0, NULL },
};

#define INT2IDX(x)	(-1*(x)-1)
static const struct log_info_cat internal_cat[OSMO_NUM_DLIB] = {
	[INT2IDX(DLGLOBAL)] = {	/* -1 becomes 0 */
		.name = "DLGLOBAL",
		.description = "Library-internal global log family",
		.loglevel = LOGL_NOTICE,
		.enabled = 1,
	},
	[INT2IDX(DLLAPD)] = {	/* -2 becomes 1 */
		.name = "DLLAPD",
		.description = "LAPD in libosmogsm",
		.loglevel = LOGL_NOTICE,
		.enabled = 1,
	},
	[INT2IDX(DLINP)] = {
		.name = "DLINP",
		.description = "A-bis Intput Subsystem",
		.loglevel = LOGL_NOTICE,
		.enabled = 1,
	},
	[INT2IDX(DLMUX)] = {
		.name = "DLMUX",
		.description = "A-bis B-Subchannel TRAU Frame Multiplex",
		.loglevel = LOGL_NOTICE,
		.enabled = 1,
	},
	[INT2IDX(DLMI)] = {
		.name = "DLMI",
		.description = "A-bis Input Driver for Signalling",
		.enabled = 0, .loglevel = LOGL_NOTICE,
	},
	[INT2IDX(DLMIB)] = {
		.name = "DLMIB",
		.description = "A-bis Input Driver for B-Channels (voice)",
		.enabled = 0, .loglevel = LOGL_NOTICE,
	},
	[INT2IDX(DLSMS)] = {
		.name = "DLSMS",
		.description = "Layer3 Short Message Service (SMS)",
		.enabled = 1, .loglevel = LOGL_NOTICE,
		.color = "\033[1;38m",
	},
	[INT2IDX(DLCTRL)] = {
		.name = "DLCTRL",
		.description = "Control Interface",
		.enabled = 1, .loglevel = LOGL_NOTICE,
	},
	[INT2IDX(DLGTP)] = {
		.name = "DLGTP",
		.description = "GPRS GTP library",
		.enabled = 1, .loglevel = LOGL_NOTICE,
	},
	[INT2IDX(DLSTATS)] = {
		.name = "DLSTATS",
		.description = "Statistics messages and logging",
		.enabled = 1, .loglevel = LOGL_NOTICE,
	},
};

/*! \brief descriptive string for each log level */
/* You have to keep this in sync with the structure loglevel_strs. */
const char *loglevel_descriptions[LOGLEVEL_DEFS+1] = {
	"Don't use. It doesn't log anything",
	"Log debug messages and higher levels",
	"Log informational messages and higher levels",
	"Log noticeable messages and higher levels",
	"Log error messages and higher levels",
	"Log only fatal messages",
	NULL,
};

/* special magic for negative (library-internal) log subsystem numbers */
static int subsys_lib2index(int subsys)
{
	return (subsys * -1) + (osmo_log_info->num_cat_user-1);
}

/*! \brief Parse a human-readable log level into a numeric value
 *  \param lvl[in] zero-terminated string containing log level name
 *  \returns numeric log level
 */
int log_parse_level(const char *lvl)
{
	return get_string_value(loglevel_strs, lvl);
}

/*! \brief convert a numeric log level into human-readable string
 *  \param lvl[in] numeric log level
 *  \returns zero-terminated string (log level name)
 */
const char *log_level_str(unsigned int lvl)
{
	return get_value_string(loglevel_strs, lvl);
}

/*! \brief parse a human-readable log category into numeric form
 *  \param[in] category human-readable log category name
 *  \returns numeric category value, or -EINVAL otherwise
 */
int log_parse_category(const char *category)
{
	int i;

	for (i = 0; i < osmo_log_info->num_cat; ++i) {
		if (osmo_log_info->cat[i].name == NULL)
			continue;
		if (!strcasecmp(osmo_log_info->cat[i].name+1, category))
			return i;
	}

	return -EINVAL;
}

/*! \brief parse the log category mask
 *  \param[in] target log target to be configured
 *  \param[in] _mask log category mask string
 *
 * The format can be this: category1:category2:category3
 * or category1,2:category2,3:...
 */
void log_parse_category_mask(struct log_target* target, const char *_mask)
{
	int i = 0;
	char *mask = strdup(_mask);
	char *category_token = NULL;

	/* Disable everything to enable it afterwards */
	for (i = 0; i < osmo_log_info->num_cat; ++i)
		target->categories[i].enabled = 0;

	category_token = strtok(mask, ":");
	OSMO_ASSERT(category_token);
	do {
		for (i = 0; i < osmo_log_info->num_cat; ++i) {
			size_t length, cat_length;
			char* colon = strstr(category_token, ",");

			if (!osmo_log_info->cat[i].name)
				continue;

			length = strlen(category_token);
			cat_length = strlen(osmo_log_info->cat[i].name);

			/* Use longest length not to match subocurrences. */
			if (cat_length > length)
				length = cat_length;

			if (colon)
			    length = colon - category_token;

			if (strncasecmp(osmo_log_info->cat[i].name,
					category_token, length) == 0) {
				int level = 0;

				if (colon)
					level = atoi(colon+1);

				target->categories[i].enabled = 1;
				target->categories[i].loglevel = level;
			}
		}
	} while ((category_token = strtok(NULL, ":")));

	free(mask);
}

static const char* color(int subsys)
{
	if (subsys < osmo_log_info->num_cat)
		return osmo_log_info->cat[subsys].color;

	return NULL;
}

static const char* category_name(int subsys)
{
	if (subsys < osmo_log_info->num_cat)
		return osmo_log_info->cat[subsys].name;

	return NULL;
}

static void _output(struct log_target *target, unsigned int subsys,
		    unsigned int level, const char *file, int line, int cont,
		    const char *format, va_list ap)
{
	char buf[4096];
	int ret, len = 0, offset = 0, rem = sizeof(buf);

	/* are we using color */
	if (target->use_color) {
		const char *c = color(subsys);
		if (c) {
			ret = snprintf(buf + offset, rem, "%s", c);
			if (ret < 0)
				goto err;
			OSMO_SNPRINTF_RET(ret, rem, offset, len);
		}
	}
	if (!cont) {
		if (target->print_ext_timestamp) {
			struct tm tm;
			struct timeval tv;
			gettimeofday(&tv, NULL);
			localtime_r(&tv.tv_sec, &tm);
			ret = snprintf(buf + offset, rem, "%04d%02d%02d%02d%02d%02d%03d ",
					tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
					tm.tm_hour, tm.tm_min, tm.tm_sec,
					(int)(tv.tv_usec / 1000));
			if (ret < 0)
				goto err;
			OSMO_SNPRINTF_RET(ret, rem, offset, len);
		} else if (target->print_timestamp) {
			char *timestr;
			time_t tm;
			tm = time(NULL);
			timestr = ctime(&tm);
			timestr[strlen(timestr)-1] = '\0';
			ret = snprintf(buf + offset, rem, "%s ", timestr);
			if (ret < 0)
				goto err;
			OSMO_SNPRINTF_RET(ret, rem, offset, len);
		}
		if (target->print_category) {
			ret = snprintf(buf + offset, rem, "%s ", category_name(subsys));
			if (ret < 0)
				goto err;
			OSMO_SNPRINTF_RET(ret, rem, offset, len);
		}
		if (target->print_filename) {
			ret = snprintf(buf + offset, rem, "<%4.4x> %s:%d ",
					subsys, file, line);
			if (ret < 0)
				goto err;
			OSMO_SNPRINTF_RET(ret, rem, offset, len);
		}
	}
	ret = vsnprintf(buf + offset, rem, format, ap);
	if (ret < 0)
		goto err;
	OSMO_SNPRINTF_RET(ret, rem, offset, len);

	ret = snprintf(buf + offset, rem, "%s",
			target->use_color ? "\033[0;m" : "");
	if (ret < 0)
		goto err;
	OSMO_SNPRINTF_RET(ret, rem, offset, len);
err:
	buf[sizeof(buf)-1] = '\0';
	target->output(target, level, buf);
}

static inline int map_subsys(int subsys)
{
	if (subsys < 0)
		subsys = subsys_lib2index(subsys);

	if (subsys > osmo_log_info->num_cat)
		subsys = DLGLOBAL;
	return subsys;
}

static inline int check_log_to_target(struct log_target *tar, int subsys, int level)
{
	struct log_category *category;

	category = &tar->categories[subsys];

	/* subsystem is not supposed to be logged */
	if (!category->enabled)
		return 0;

	/* Check the global log level */
	if (tar->loglevel != 0 && level < tar->loglevel)
		return 0;

	/* Check the category log level */
	if (tar->loglevel == 0 && category->loglevel != 0 &&
	    level < category->loglevel)
		return 0;

	/* Apply filters here... if that becomes messy we will
	 * need to put filters in a list and each filter will
	 * say stop, continue, output */
	if ((tar->filter_map & LOG_FILTER_ALL) != 0)
		return 1;

	if (osmo_log_info->filter_fn)
		return osmo_log_info->filter_fn(&log_context, tar);

	/* TODO: Check the filter/selector too? */
	return 1;
}

/*! \brief vararg version of logging function
 *  \param[in] subsys Logging sub-system
 *  \param[in] level Log level
 *  \param[in] file name of source code file
 *  \param[in] cont continuation (1) or new line (0)
 *  \param[in] format format string
 *  \param[in] ap vararg-list containing format string arguments
 */
void osmo_vlogp(int subsys, int level, const char *file, int line,
		int cont, const char *format, va_list ap)
{
	struct log_target *tar;

	subsys = map_subsys(subsys);

	llist_for_each_entry(tar, &osmo_log_target_list, entry) {
		va_list bp;

		if (!check_log_to_target(tar, subsys, level))
			continue;

		/* According to the manpage, vsnprintf leaves the value of ap
		 * in undefined state. Since _output uses vsnprintf and it may
		 * be called several times, we have to pass a copy of ap. */
		va_copy(bp, ap);
		_output(tar, subsys, level, file, line, cont, format, bp);
		va_end(bp);
	}
}

/*! \brief logging function used by DEBUGP() macro
 *  \param[in] subsys Logging sub-system
 *  \param[in] file name of source code file
 *  \param[in] cont continuation (1) or new line (0)
 *  \param[in] format format string
 */
void logp(int subsys, const char *file, int line, int cont,
	  const char *format, ...)
{
	va_list ap;

	va_start(ap, format);
	osmo_vlogp(subsys, LOGL_DEBUG, file, line, cont, format, ap);
	va_end(ap);
}

/*! \brief logging function used by LOGP() macro
 *  \param[in] subsys Logging sub-system
 *  \param[in] level Log level
 *  \param[in] file name of source code file
 *  \param[in] cont continuation (1) or new line (0)
 *  \param[in] format format string
 */
void logp2(int subsys, unsigned int level, const char *file, int line, int cont, const char *format, ...)
{
	va_list ap;

	va_start(ap, format);
	osmo_vlogp(subsys, level, file, line, cont, format, ap);
	va_end(ap);
}

/*! \brief Register a new log target with the logging core
 *  \param[in] target Log target to be registered
 */
void log_add_target(struct log_target *target)
{
	llist_add_tail(&target->entry, &osmo_log_target_list);
}

/*! \brief Unregister a log target from the logging core
 *  \param[in] target Log target to be unregistered
 */
void log_del_target(struct log_target *target)
{
	llist_del(&target->entry);
}

/*! \brief Reset (clear) the logging context */
void log_reset_context(void)
{
	memset(&log_context, 0, sizeof(log_context));
}

/*! \brief Set the logging context
 *  \param[in] ctx_nr logging context number
 *  \param[in] value value to which the context is to be set
 *  \returns 0 in case of success; negative otherwise
 *
 * A logging context is something like the subscriber identity to which
 * the currently processed message relates, or the BTS through which it
 * was received.  As soon as this data is known, it can be set using
 * this function.  The main use of context information is for logging
 * filters.
 */
int log_set_context(uint8_t ctx_nr, void *value)
{
	if (ctx_nr > LOG_MAX_CTX)
		return -EINVAL;

	log_context.ctx[ctx_nr] = value;

	return 0;
}

/*! \brief Enable the \ref LOG_FILTER_ALL log filter
 *  \param[in] target Log target to be affected
 *  \param[in] all enable (1) or disable (0) the ALL filter
 *
 * When the \ref LOG_FILTER_ALL filter is enabled, all log messages will
 * be printed.  It acts as a wildcard.  Setting it to \a 1 means there
 * is no filtering.
 */
void log_set_all_filter(struct log_target *target, int all)
{
	if (all)
		target->filter_map |= LOG_FILTER_ALL;
	else
		target->filter_map &= ~LOG_FILTER_ALL;
}

/*! \brief Enable or disable the use of colored output
 *  \param[in] target Log target to be affected
 *  \param[in] use_color Use color (1) or don't use color (0)
 */
void log_set_use_color(struct log_target *target, int use_color)
{
	target->use_color = use_color;
}

/*! \brief Enable or disable printing of timestamps while logging
 *  \param[in] target Log target to be affected
 *  \param[in] print_timestamp Enable (1) or disable (0) timestamps
 */
void log_set_print_timestamp(struct log_target *target, int print_timestamp)
{
	target->print_timestamp = print_timestamp;
}

/*! \brief Enable or disable printing of extended timestamps while logging
 *  \param[in] target Log target to be affected
 *  \param[in] print_timestamp Enable (1) or disable (0) timestamps
 *
 * When both timestamp and extended timestamp is enabled then only
 * the extended timestamp will be used. The format of the timestamp
 * is YYYYMMDDhhmmssnnn.
 */
void log_set_print_extended_timestamp(struct log_target *target, int print_timestamp)
{
	target->print_ext_timestamp = print_timestamp;
}

/*! \brief Enable or disable printing of the filename while logging
 *  \param[in] target Log target to be affected
 *  \param[in] print_filename Enable (1) or disable (0) filenames
 */
void log_set_print_filename(struct log_target *target, int print_filename)
{
	target->print_filename = print_filename;
}

/*! \brief Enable or disable printing of the category name
 *  \param[in] target Log target to be affected
 *  \param[in] print_catname Enable (1) or disable (0) filenames
 *
 *  Print the category/subsys name in front of every log message.
 */
void log_set_print_category(struct log_target *target, int print_category)
{
	target->print_category = print_category;
}

/*! \brief Set the global log level for a given log target
 *  \param[in] target Log target to be affected
 *  \param[in] log_level New global log level
 */
void log_set_log_level(struct log_target *target, int log_level)
{
	target->loglevel = log_level;
}

/*! \brief Set a category filter on a given log target
 *  \param[in] target Log target to be affected
 *  \param[in] category Log category to be affected
 *  \param[in] enable whether to enable or disable the filter
 *  \param[in] level Log level of the filter
 */
void log_set_category_filter(struct log_target *target, int category,
			       int enable, int level)
{
	if (category >= osmo_log_info->num_cat)
		return;
	target->categories[category].enabled = !!enable;
	target->categories[category].loglevel = level;
}

static void _file_output(struct log_target *target, unsigned int level,
			 const char *log)
{
	fprintf(target->tgt_file.out, "%s", log);
	fflush(target->tgt_file.out);
}

/*! \brief Create a new log target skeleton
 *  \returns dynamically-allocated log target
 *  This funcition allocates a \ref log_target and initializes it
 *  with some default values.  The newly created target is not
 *  registered yet.
 */
struct log_target *log_target_create(void)
{
	struct log_target *target;
	unsigned int i;

	target = talloc_zero(tall_log_ctx, struct log_target);
	if (!target)
		return NULL;

	target->categories = talloc_zero_array(target, 
						struct log_category,
						osmo_log_info->num_cat);
	if (!target->categories) {
		talloc_free(target);
		return NULL;
	}

	INIT_LLIST_HEAD(&target->entry);

	/* initialize the per-category enabled/loglevel from defaults */
	for (i = 0; i < osmo_log_info->num_cat; i++) {
		struct log_category *cat = &target->categories[i];
		cat->enabled = osmo_log_info->cat[i].enabled;
		cat->loglevel = osmo_log_info->cat[i].loglevel;
	}

	/* global settings */
	target->use_color = 1;
	target->print_timestamp = 0;
	target->print_filename = 1;

	/* global log level */
	target->loglevel = 0;
	return target;
}

/*! \brief Create the STDERR log target
 *  \returns dynamically-allocated \ref log_target for STDERR */
struct log_target *log_target_create_stderr(void)
{
/* since C89/C99 says stderr is a macro, we can safely do this! */
#ifdef stderr
	struct log_target *target;

	target = log_target_create();
	if (!target)
		return NULL;

	target->type = LOG_TGT_TYPE_STDERR;
	target->tgt_file.out = stderr;
	target->output = _file_output;
	return target;
#else
	return NULL;
#endif /* stderr */
}

/*! \brief Create a new file-based log target
 *  \param[in] fname File name of the new log file
 *  \returns Log target in case of success, NULL otherwise
 */
struct log_target *log_target_create_file(const char *fname)
{
	struct log_target *target;

	target = log_target_create();
	if (!target)
		return NULL;

	target->type = LOG_TGT_TYPE_FILE;
	target->tgt_file.out = fopen(fname, "a");
	if (!target->tgt_file.out)
		return NULL;

	target->output = _file_output;

	target->tgt_file.fname = talloc_strdup(target, fname);

	return target;
}

/*! \brief Find a registered log target
 *  \param[in] type Log target type
 *  \param[in] fname File name
 *  \returns Log target (if found), NULL otherwise
 */
struct log_target *log_target_find(int type, const char *fname)
{
	struct log_target *tgt;

	llist_for_each_entry(tgt, &osmo_log_target_list, entry) {
		if (tgt->type != type)
			continue;
		if (tgt->type == LOG_TGT_TYPE_FILE) {
			if (!strcmp(fname, tgt->tgt_file.fname))
				return tgt;
		} else
			return tgt;
	}
	return NULL;
}

/*! \brief Unregister, close and delete a log target
 *  \param target[in] log target to unregister, close and delete */
void log_target_destroy(struct log_target *target)
{

	/* just in case, to make sure we don't have any references */
	log_del_target(target);

	if (target->output == &_file_output) {
/* since C89/C99 says stderr is a macro, we can safely do this! */
#ifdef stderr
		/* don't close stderr */
		if (target->tgt_file.out != stderr)
#endif
		{
			fclose(target->tgt_file.out);
			target->tgt_file.out = NULL;
		}
	}

	talloc_free(target);
}

/*! \brief close and re-open a log file (for log file rotation)
 *  \param[in] target log target to re-open
 *  \returns 0 in case of success; negative otherwise */
int log_target_file_reopen(struct log_target *target)
{
	fclose(target->tgt_file.out);

	target->tgt_file.out = fopen(target->tgt_file.fname, "a");
	if (!target->tgt_file.out)
		return -errno;

	/* we assume target->output already to be set */

	return 0;
}

/*! \brief close and re-open all log files (for log file rotation)
 *  \returns 0 in case of success; negative otherwise */
int log_targets_reopen(void)
{
	struct log_target *tar;
	int rc = 0;

	llist_for_each_entry(tar, &osmo_log_target_list, entry) {
		switch (tar->type) {
		case LOG_TGT_TYPE_FILE:
			if (log_target_file_reopen(tar) < 0)
				rc = -1;
			break;
		default:
			break;
		}
	}

	return rc;
}

/*! \brief Generates the logging command string for VTY
 *  \param[in] unused_info Deprecated parameter, no longer used!
 *  \returns vty command string for use by VTY command node
 */
const char *log_vty_command_string(const struct log_info *unused_info)
{
	struct log_info *info = osmo_log_info;
	int len = 0, offset = 0, ret, i, rem;
	int size = strlen("logging level () ()") + 1;
	char *str;

	for (i = 0; i < info->num_cat; i++) {
		if (info->cat[i].name == NULL)
			continue;
		size += strlen(info->cat[i].name) + 1;
	}

	for (i = 0; i < LOGLEVEL_DEFS; i++)
		size += strlen(loglevel_strs[i].str) + 1;

	rem = size;
	str = talloc_zero_size(tall_log_ctx, size);
	if (!str)
		return NULL;

	ret = snprintf(str + offset, rem, "logging level (all|");
	if (ret < 0)
		goto err;
	OSMO_SNPRINTF_RET(ret, rem, offset, len);

	for (i = 0; i < info->num_cat; i++) {
		if (info->cat[i].name) {
			int j, name_len = strlen(info->cat[i].name)+1;
			char name[name_len];

			for (j = 0; j < name_len; j++)
				name[j] = tolower(info->cat[i].name[j]);

			name[name_len-1] = '\0';
			ret = snprintf(str + offset, rem, "%s|", name+1);
			if (ret < 0)
				goto err;
			OSMO_SNPRINTF_RET(ret, rem, offset, len);
		}
	}
	offset--;	/* to remove the trailing | */
	rem++;

	ret = snprintf(str + offset, rem, ") (");
	if (ret < 0)
		goto err;
	OSMO_SNPRINTF_RET(ret, rem, offset, len);

	for (i = 0; i < LOGLEVEL_DEFS; i++) {
		int j, loglevel_str_len = strlen(loglevel_strs[i].str)+1;
		char loglevel_str[loglevel_str_len];

		for (j = 0; j < loglevel_str_len; j++)
			loglevel_str[j] = tolower(loglevel_strs[i].str[j]);

		loglevel_str[loglevel_str_len-1] = '\0';
		ret = snprintf(str + offset, rem, "%s|", loglevel_str);
		if (ret < 0)
			goto err;
		OSMO_SNPRINTF_RET(ret, rem, offset, len);
	}
	offset--;	/* to remove the trailing | */
	rem++;

	ret = snprintf(str + offset, rem, ")");
	if (ret < 0)
		goto err;
	OSMO_SNPRINTF_RET(ret, rem, offset, len);
err:
	str[size-1] = '\0';
	return str;
}

/*! \brief Generates the logging command description for VTY
 *  \param[in] unused_info Deprecated parameter, no longer used!
 *  \returns logging command description for use by VTY command node
 */
const char *log_vty_command_description(const struct log_info *unused_info)
{
	struct log_info *info = osmo_log_info;
	char *str;
	int i, ret, len = 0, offset = 0, rem;
	unsigned int size =
		strlen(LOGGING_STR
		       "Set the log level for a specified category\n") + 1;

	for (i = 0; i < info->num_cat; i++) {
		if (info->cat[i].name == NULL)
			continue;
		size += strlen(info->cat[i].description) + 1;
	}

	for (i = 0; i < LOGLEVEL_DEFS; i++)
		size += strlen(loglevel_descriptions[i]) + 1;

	size += strlen("Global setting for all subsystems") + 1;
	rem = size;
	str = talloc_zero_size(tall_log_ctx, size);
	if (!str)
		return NULL;

	ret = snprintf(str + offset, rem, LOGGING_STR
			"Set the log level for a specified category\n");
	if (ret < 0)
		goto err;
	OSMO_SNPRINTF_RET(ret, rem, offset, len);

	ret = snprintf(str + offset, rem,
			"Global setting for all subsystems\n");
	if (ret < 0)
		goto err;
	OSMO_SNPRINTF_RET(ret, rem, offset, len);

	for (i = 0; i < info->num_cat; i++) {
		if (info->cat[i].name == NULL)
			continue;
		ret = snprintf(str + offset, rem, "%s\n",
				info->cat[i].description);
		if (ret < 0)
			goto err;
		OSMO_SNPRINTF_RET(ret, rem, offset, len);
	}
	for (i = 0; i < LOGLEVEL_DEFS; i++) {
		ret = snprintf(str + offset, rem, "%s\n",
				loglevel_descriptions[i]);
		if (ret < 0)
			goto err;
		OSMO_SNPRINTF_RET(ret, rem, offset, len);
	}
err:
	str[size-1] = '\0';
	return str;
}

/*! \brief Initialize the Osmocom logging core
 *  \param[in] inf Information regarding logging categories
 *  \param[in] ctx \ref talloc context for logging allocations
 *  \returns 0 in case of success, negative in case of error
 */
int log_init(const struct log_info *inf, void *ctx)
{
	int i;

	tall_log_ctx = talloc_named_const(ctx, 1, "logging");
	if (!tall_log_ctx)
		return -ENOMEM;

	osmo_log_info = talloc_zero(tall_log_ctx, struct log_info);
	if (!osmo_log_info)
		return -ENOMEM;

	osmo_log_info->filter_fn = inf->filter_fn;
	osmo_log_info->num_cat_user = inf->num_cat;
	/* total number = number of user cat + library cat */
	osmo_log_info->num_cat = inf->num_cat + ARRAY_SIZE(internal_cat);

	osmo_log_info->cat = talloc_zero_array(osmo_log_info,
					struct log_info_cat,
					osmo_log_info->num_cat);
	if (!osmo_log_info->cat) {
		talloc_free(osmo_log_info);
		osmo_log_info = NULL;
		return -ENOMEM;
	}

	/* copy over the user part */
	for (i = 0; i < inf->num_cat; i++) {
		memcpy((struct log_info_cat *) &osmo_log_info->cat[i],
			&inf->cat[i],
			sizeof(struct log_info_cat));
	}

	/* copy over the library part */
	for (i = 0; i < ARRAY_SIZE(internal_cat); i++) {
		unsigned int cn = osmo_log_info->num_cat_user + i;
		memcpy((struct log_info_cat *) &osmo_log_info->cat[cn],
			&internal_cat[i], sizeof(struct log_info_cat));
	}

	return 0;
}

/* \brief De-initialize the Osmocom logging core
 * This function destroys all targets and releases associated memory */
void log_fini(void)
{
	struct log_target *tar, *tar2;

	llist_for_each_entry_safe(tar, tar2, &osmo_log_target_list, entry)
		log_target_destroy(tar);

	talloc_free(osmo_log_info);
	osmo_log_info = NULL;
	talloc_free(tall_log_ctx);
	tall_log_ctx = NULL;
}

/*! \brief Check whether a log entry will be generated.
 *  \returns != 0 if a log entry might get generated by at least one target */
int log_check_level(int subsys, unsigned int level)
{
	struct log_target *tar;

	subsys = map_subsys(subsys);

	/* TODO: The following could/should be cached (update on config) */

	llist_for_each_entry(tar, &osmo_log_target_list, entry) {
		if (!check_log_to_target(tar, subsys, level))
			continue;

		/* This might get logged (ignoring filters) */
		return 1;
	}

	/* We are sure, that this will not be logged. */
	return 0;
}

/*! @} */