Merge pull request #2344 from brauner/2018-05-23/on_demand_log_file

[mirror_lxc.git] / src / lxc / log.c

/*
 * lxc: linux Container library
 *
 * (C) Copyright IBM Corp. 2007, 2008
 *
 * Authors:
 * Cedric Le Goater <legoater@free.fr>
 *
 * 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.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#define _GNU_SOURCE
#define __STDC_FORMAT_MACROS /* Required for PRIu64 to work. */
#include <stdint.h>
#include <stdio.h>
#include <errno.h>
#include <inttypes.h>
#include <limits.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <string.h>
#include <pthread.h>
#include <time.h>

#include <syslog.h>
#include <stdio.h>

#include <fcntl.h>
#include <stdlib.h>

#include "log.h"
#include "caps.h"
#include "utils.h"
#include "lxccontainer.h"

#ifndef HAVE_STRLCPY
#include "include/strlcpy.h"
#endif

/* We're logging in seconds and nanoseconds. Assuming that the underlying
 * datatype is currently at maximum a 64bit integer, we have a date string that
 * is of maximum length (2^64 - 1) * 2 = (21 + 21) = 42.
 */
#define LXC_LOG_TIME_SIZE ((LXC_NUMSTRLEN64)*2)

int lxc_log_fd = -1;
static int syslog_enable = 0;
int lxc_quiet_specified;
int lxc_log_use_global_fd;
static int lxc_loglevel_specified;

static char log_prefix[LXC_LOG_PREFIX_SIZE] = "lxc";
static char *log_fname = NULL;
static char *log_vmname = NULL;

lxc_log_define(lxc_log, lxc);

static int lxc_log_priority_to_syslog(int priority)
{
        switch (priority) {
        case LXC_LOG_LEVEL_FATAL:
                return LOG_EMERG;
        case LXC_LOG_LEVEL_ALERT:
                return LOG_ALERT;
        case LXC_LOG_LEVEL_CRIT:
                return LOG_CRIT;
        case LXC_LOG_LEVEL_ERROR:
                return LOG_ERR;
        case LXC_LOG_LEVEL_WARN:
                return LOG_WARNING;
        case LXC_LOG_LEVEL_NOTICE:
        case LXC_LOG_LEVEL_NOTSET:
                return LOG_NOTICE;
        case LXC_LOG_LEVEL_INFO:
                return LOG_INFO;
        case LXC_LOG_LEVEL_TRACE:
        case LXC_LOG_LEVEL_DEBUG:
                return LOG_DEBUG;
        }

        /* Not reached */
        return LOG_NOTICE;
}

/*---------------------------------------------------------------------------*/
static int log_append_syslog(const struct lxc_log_appender *appender,
                             struct lxc_log_event *event)
{
        char *msg;
        int rc, len;
        va_list args;
        const char *log_container_name = log_vmname;

#ifndef NO_LXC_CONF
        if (current_config && !log_container_name)
                log_container_name = current_config->name;
#endif

        if (!syslog_enable)
                return 0;

        va_copy(args, *event->vap);
        len = vsnprintf(NULL, 0, event->fmt, args) + 1;
        va_end(args);

        msg = malloc(len * sizeof(char));
        if (msg == NULL)
                return 0;

        rc = vsnprintf(msg, len, event->fmt, *event->vap);
        if (rc == -1 || rc >= len) {
                free(msg);
                return 0;
        }

        syslog(lxc_log_priority_to_syslog(event->priority),
                "%s%s %s - %s:%s:%d - %s" ,
                log_container_name ? log_container_name : "",
                log_container_name ? ":" : "",
                event->category,
                event->locinfo->file, event->locinfo->func,
                event->locinfo->line,
                msg);
        free(msg);

        return 0;
}

/*---------------------------------------------------------------------------*/
static int log_append_stderr(const struct lxc_log_appender *appender,
                             struct lxc_log_event *event)
{
        const char *log_container_name;

        if (event->priority < LXC_LOG_LEVEL_ERROR)
                return 0;

        log_container_name = log_vmname;

#ifndef NO_LXC_CONF
        if (current_config && !log_container_name)
                log_container_name = current_config->name;
#endif

        fprintf(stderr, "%s: %s%s", log_prefix,
                log_container_name ? log_container_name : "",
                log_container_name ? ": " : "");
        fprintf(stderr, "%s: %s: %d ", event->locinfo->file,
                event->locinfo->func, event->locinfo->line);
        vfprintf(stderr, event->fmt, *event->vap);
        fprintf(stderr, "\n");

        return 0;
}

/*---------------------------------------------------------------------------*/
int lxc_unix_epoch_to_utc(char *buf, size_t bufsize, const struct timespec *time)
{
        int64_t epoch_to_days, z, era, doe, yoe, year, doy, mp, day, month,
            d_in_s, hours, h_in_s, minutes, seconds;
        char nanosec[LXC_NUMSTRLEN64];
        int ret;

        /* See https://howardhinnant.github.io/date_algorithms.html for an
         * explanation of the algorithm used here.
         */

        /* Convert Epoch in seconds to number of days. */
        epoch_to_days = time->tv_sec / 86400;

        /* Shift the Epoch from 1970-01-01 to 0000-03-01. */
        z = epoch_to_days + 719468;

        /* compute the era from the serial date by simply dividing by the number
         * of days in an era (146097).
         */
        era = (z >= 0 ? z : z - 146096) / 146097;

        /* The day-of-era (doe) can then be found by subtracting the era number
         * times the number of days per era, from the serial date.
         */
        doe = (z - era * 146097);

        /* From the day-of-era (doe), the year-of-era (yoe, range [0, 399]) can
         * be computed.
         */
        yoe = (doe - doe / 1460 + doe / 36524 - doe / 146096) / 365;

        /* Given year-of-era, and era, one can now compute the year. */
        year = yoe + era * 400;

        /* Also the day-of-year, again with the year beginning on Mar. 1, can be
         * computed from the day-of-era and year-of-era.
         */
        doy = doe - (365 * yoe + yoe / 4 - yoe / 100);

        /* Given day-of-year, find the month number. */
        mp = (5 * doy + 2) / 153;

        /* From day-of-year and month-of-year we can now easily compute
         * day-of-month.
         */
        day = doy - (153 * mp + 2) / 5 + 1;

        /* Transform the month number from the [0, 11] / [Mar, Feb] system to
         * the civil system: [1, 12] to find the correct month.
         */
        month = mp + (mp < 10 ? 3 : -9);

        /* The algorithm assumes that a year begins on 1 March, so add 1 before
         * that. */
        if (month < 3)
                year++;

        /* Transform days in the epoch to seconds. */
        d_in_s = epoch_to_days * 86400;

        /* To find the current hour simply substract the Epoch_to_days from the
         * total Epoch and divide by the number of seconds in an hour.
         */
        hours = (time->tv_sec - d_in_s) / 3600;

        /* Transform hours to seconds. */
        h_in_s = hours * 3600;

        /* Calculate minutes by substracting the seconds for all days in the
         * epoch and for all hours in the epoch and divide by the number of
         * minutes in an hour.
         */
        minutes = (time->tv_sec - d_in_s - h_in_s) / 60;

        /* Calculate the seconds by substracting the seconds for all days in the
         * epoch, hours in the epoch and minutes in the epoch.
         */
        seconds = (time->tv_sec - d_in_s - h_in_s - (minutes * 60));

        /* Make string from nanoseconds. */
        ret = snprintf(nanosec, LXC_NUMSTRLEN64, "%"PRId64, (int64_t)time->tv_nsec);
        if (ret < 0 || ret >= LXC_NUMSTRLEN64)
                return -1;

        /* Create final timestamp for the log and shorten nanoseconds to 3
         * digit precision.
         */
        ret = snprintf(buf, bufsize,
                       "%" PRId64 "%02" PRId64 "%02" PRId64 "%02" PRId64
                       "%02" PRId64 "%02" PRId64 ".%.3s",
                       year, month, day, hours, minutes, seconds, nanosec);
        if (ret < 0 || (size_t)ret >= bufsize)
                return -1;

        return 0;
}

/* This function needs to make extra sure that it is thread-safe. We had some
 * problems with that before. This especially involves time-conversion
 * functions. I don't want to find any localtime() or gmtime() functions or
 * relatives in here. Not even localtime_r() or gmtime_r() or relatives. They
 * all fiddle with global variables and locking in various libcs. They cause
 * deadlocks when liblxc is used multi-threaded and no matter how smart you
 * think you are, you __will__ cause trouble using them.
 * (As a short example how this can cause trouble: LXD uses forkstart to fork
 * off a new process that runs the container. At the same time the go runtime
 * LXD relies on does its own multi-threading thing which we can't controll. The
 * fork()ing + threading then seems to mess with the locking states in these
 * time functions causing deadlocks.)
 * The current solution is to be good old unix people and use the Epoch as our
 * reference point and simply use the seconds and nanoseconds that have past
 * since then. This relies on clock_gettime() which is explicitly marked MT-Safe
 * with no restrictions! This way, anyone who is really strongly invested in
 * getting the actual time the log entry was created, can just convert it for
 * themselves. Our logging is mostly done for debugging purposes so don't try
 * to make it pretty. Pretty might cost you thread-safety.
 */
static int log_append_logfile(const struct lxc_log_appender *appender,
                              struct lxc_log_event *event)
{
        char buffer[LXC_LOG_BUFFER_SIZE];
        char date_time[LXC_LOG_TIME_SIZE];
        int n, ret;
        int fd_to_use = -1;
        const char *log_container_name = log_vmname;

#ifndef NO_LXC_CONF
        if (current_config) {
                if (!lxc_log_use_global_fd)
                        fd_to_use = current_config->logfd;

                if (!log_container_name)
                        log_container_name = current_config->name;
        }
#endif

        if (fd_to_use == -1)
                fd_to_use = lxc_log_fd;

        if (fd_to_use == -1)
                return 0;

        if (lxc_unix_epoch_to_utc(date_time, LXC_LOG_TIME_SIZE, &event->timestamp) < 0)
                return 0;

        n = snprintf(buffer, sizeof(buffer),
                        "%s%s%s %s %-8s %s - %s:%s:%d - ",
                        log_prefix,
                        log_container_name ? " " : "",
                        log_container_name ? log_container_name : "",
                        date_time,
                        lxc_log_priority_to_string(event->priority),
                        event->category,
                        event->locinfo->file, event->locinfo->func,
                        event->locinfo->line);

        if (n < 0)
                return n;

        if ((size_t)n < (sizeof(buffer) - 1)) {
                ret = vsnprintf(buffer + n, sizeof(buffer) - n, event->fmt, *event->vap);
                if (ret < 0)
                        return 0;

                n += ret;
        }

        if ((size_t)n >= sizeof(buffer))
                n = sizeof(buffer) - 1;

        buffer[n] = '\n';

        return write(fd_to_use, buffer, n + 1);
}

static struct lxc_log_appender log_appender_syslog = {
        .name           = "syslog",
        .append         = log_append_syslog,
        .next           = NULL,
};

static struct lxc_log_appender log_appender_stderr = {
        .name           = "stderr",
        .append         = log_append_stderr,
        .next           = NULL,
};

static struct lxc_log_appender log_appender_logfile = {
        .name           = "logfile",
        .append         = log_append_logfile,
        .next           = NULL,
};

static struct lxc_log_category log_root = {
        .name           = "root",
        .priority       = LXC_LOG_LEVEL_ERROR,
        .appender       = NULL,
        .parent         = NULL,
};

struct lxc_log_category lxc_log_category_lxc = {
        .name           = "lxc",
        .priority       = LXC_LOG_LEVEL_ERROR,
        .appender       = &log_appender_logfile,
        .parent         = &log_root
};

/*---------------------------------------------------------------------------*/
static int build_dir(const char *name)
{
        int ret;
        char *e, *n, *p;

        /* Make copy of string since we'll be modifying it. */
        n = strdup(name);
        if (!n) {
                ERROR("Out of memory while creating directory '%s'.", name);
                return -1;
        }

        e = &n[strlen(n)];
        for (p = n+1; p < e; p++) {
                if (*p != '/')
                        continue;
                *p = '\0';
                if (access(n, F_OK)) {
                        ret = lxc_unpriv(mkdir(n, 0755));
                        if (ret && errno != EEXIST) {
                                SYSERROR("failed to create directory '%s'.", n);
                                free(n);
                                return -1;
                        }
                }
                *p = '/';
        }
        free(n);
        return 0;
}

/*---------------------------------------------------------------------------*/
static int log_open(const char *name)
{
        int fd;
        int newfd;

        fd = lxc_unpriv(open(name, O_CREAT | O_WRONLY |
                             O_APPEND | O_CLOEXEC, 0666));
        if (fd == -1) {
                ERROR("failed to open log file \"%s\" : %s", name,
                      strerror(errno));
                return -1;
        }

        if (fd > 2)
                return fd;

        newfd = fcntl(fd, F_DUPFD_CLOEXEC, 3);
        if (newfd == -1)
                ERROR("failed to dup log fd %d : %s", fd, strerror(errno));

        close(fd);
        return newfd;
}

/*
 * Build the path to the log file
 * @name     : the name of the container
 * @lxcpath  : the lxcpath to use as a basename or NULL to use LOGPATH
 * Returns malloced path on success, or NULL on failure
 */
static char *build_log_path(const char *name, const char *lxcpath)
{
        char *p;
        int len, ret, use_dir;

        if (!name)
                return NULL;

#if USE_CONFIGPATH_LOGS
        use_dir = 1;
#else
        use_dir = 0;
#endif

        /*
         * If USE_CONFIGPATH_LOGS is true or lxcpath is given, the resulting
         * path will be:
         * '$logpath' + '/' + '$name' + '/' + '$name' + '.log' + '\0'
         *
         * If USE_CONFIGPATH_LOGS is false the resulting path will be:
         * '$logpath' + '/' + '$name' + '.log' + '\0'
         */
        len = strlen(name) + 6; /* 6 == '/' + '.log' + '\0' */
        if (lxcpath)
                use_dir = 1;
        else
                lxcpath = LOGPATH;

        if (use_dir)
                len += strlen(lxcpath) + 1 + strlen(name) + 1;  /* add "/$container_name/" */
        else
                len += strlen(lxcpath) + 1;
        p = malloc(len);
        if (!p)
                return p;

        if (use_dir)
                ret = snprintf(p, len, "%s/%s/%s.log", lxcpath, name, name);
        else
                ret = snprintf(p, len, "%s/%s.log", lxcpath, name);

        if (ret < 0 || ret >= len) {
                free(p);
                return NULL;
        }
        return p;
}

extern void lxc_log_close(void)
{
        closelog();
        free(log_vmname);
        log_vmname = NULL;
        if (lxc_log_fd == -1)
                return;
        close(lxc_log_fd);
        lxc_log_fd = -1;
        free(log_fname);
        log_fname = NULL;
}

/*
 * This can be called:
 *   1. when a program calls lxc_log_init with no logfile parameter (in which
 *      case the default is used).  In this case lxc.loge can override this.
 *   2. when a program calls lxc_log_init with a logfile parameter.  In this
 *      case we don't want lxc.log to override this.
 *   3. When a lxc.log entry is found in config file.
 */
static int __lxc_log_set_file(const char *fname, int create_dirs)
{
        /* we are overriding the default. */
        if (lxc_log_fd != -1)
                lxc_log_close();

        if (!fname)
                return -1;

        if (strlen(fname) == 0) {
                log_fname = NULL;
                return 0;
        }

#if USE_CONFIGPATH_LOGS
        /* We don't build_dir for the default if the default is i.e.
         * /var/lib/lxc/$container/$container.log.
         */
        if (create_dirs)
#endif
        if (build_dir(fname)) {
                ERROR("failed to create dir for log file \"%s\" : %s", fname,
                      strerror(errno));
                return -1;
        }

        lxc_log_fd = log_open(fname);
        if (lxc_log_fd == -1)
                return -1;

        log_fname = strdup(fname);
        return 0;
}

static int _lxc_log_set_file(const char *name, const char *lxcpath, int create_dirs)
{
        char *logfile;
        int ret;

        logfile = build_log_path(name, lxcpath);
        if (!logfile) {
                ERROR("could not build log path");
                return -1;
        }
        ret = __lxc_log_set_file(logfile, create_dirs);
        free(logfile);
        return ret;
}

extern int lxc_log_syslog(int facility)
{
        struct lxc_log_appender *appender;

        openlog(log_prefix, LOG_PID, facility);
        if (!lxc_log_category_lxc.appender) {
                lxc_log_category_lxc.appender = &log_appender_syslog;
                return 0;
        }

        appender = lxc_log_category_lxc.appender;
        /* Check if syslog was already added, to avoid creating a loop */
        while (appender) {
                if (appender == &log_appender_syslog) {
                        /* not an error: openlog re-opened the connection */
                        return 0;
                }
                appender = appender->next;
        }

        appender = lxc_log_category_lxc.appender;
        while (appender->next != NULL)
                appender = appender->next;
        appender->next = &log_appender_syslog;

        return 0;
}

extern void lxc_log_enable_syslog(void)
{
        syslog_enable = 1;
}

/*
 * lxc_log_init:
 * Called from lxc front-end programs (like lxc-create, lxc-start) to
 * initalize the log defaults.
 */
extern int lxc_log_init(struct lxc_log *log)
{
        int lxc_priority = LXC_LOG_LEVEL_ERROR;
        int ret;

        if (lxc_log_fd != -1) {
                WARN("lxc_log_init called with log already initialized");
                return 0;
        }

        if (log->level)
                lxc_priority = lxc_log_priority_to_int(log->level);

        if (!lxc_loglevel_specified) {
                lxc_log_category_lxc.priority = lxc_priority;
                lxc_loglevel_specified = 1;
        }

        if (!lxc_quiet_specified) {
                if (!log->quiet)
                        lxc_log_category_lxc.appender->next = &log_appender_stderr;
        }

        if (log->prefix)
                lxc_log_set_prefix(log->prefix);

        if (log->name)
                log_vmname = strdup(log->name);

        if (log->file) {
                if (strcmp(log->file, "none") == 0)
                        return 0;
                ret = __lxc_log_set_file(log->file, 1);
                lxc_log_use_global_fd = 1;
        } else {
                /* if no name was specified, there nothing to do */
                if (!log->name)
                        return 0;

                ret = -1;

                if (!log->lxcpath)
                        log->lxcpath = LOGPATH;

                /* try LOGPATH if lxcpath is the default for the privileged containers */
                if (!geteuid() && strcmp(LXCPATH, log->lxcpath) == 0)
                        ret = _lxc_log_set_file(log->name, NULL, 0);

                /* try in lxcpath */
                if (ret < 0)
                        ret = _lxc_log_set_file(log->name, log->lxcpath, 1);

                /* try LOGPATH in case its writable by the caller */
                if (ret < 0)
                        ret = _lxc_log_set_file(log->name, NULL, 0);
        }

        /*
         * If !file, that is, if the user did not request this logpath, then
         * ignore failures and continue logging to console
         */
        if (!log->file && ret != 0) {
                INFO("Ignoring failure to open default logfile.");
                ret = 0;
        }

        return ret;
}

/*
 * This is called when we read a lxc.log.level entry in a lxc.conf file.  This
 * happens after processing command line arguments, which override the .conf
 * settings.  So only set the level if previously unset.
 */
extern int lxc_log_set_level(int *dest, int level)
{
        if (level < 0 || level >= LXC_LOG_LEVEL_NOTSET) {
                ERROR("invalid log priority %d", level);
                return -1;
        }
        *dest = level;
        return 0;
}

extern int lxc_log_get_level(void)
{
        return lxc_log_category_lxc.priority;
}

extern bool lxc_log_has_valid_level(void)
{
        int log_level = lxc_log_get_level();
        if (log_level < 0 || log_level >= LXC_LOG_LEVEL_NOTSET)
                return false;
        return true;
}

/*
 * This is called when we read a lxc.logfile entry in a lxc.conf file.  This
 * happens after processing command line arguments, which override the .conf
 * settings.  So only set the file if previously unset.
 */
extern int lxc_log_set_file(int *fd, const char *fname)
{
        if (*fd != -1) {
                close(*fd);
                *fd = -1;
        }

        if (build_dir(fname)) {
                ERROR("failed to create dir for log file \"%s\" : %s", fname,
                                strerror(errno));
                return -1;
        }

        *fd = log_open(fname);
        if (*fd == -1)
                return -errno;
        return 0;
}

extern const char *lxc_log_get_file(void)
{
        return log_fname;
}

extern void lxc_log_set_prefix(const char *prefix)
{
        /* We don't care if thte prefix is truncated. */
        (void)strlcpy(log_prefix, prefix, sizeof(log_prefix));
}

extern const char *lxc_log_get_prefix(void)
{
        return log_prefix;
}

extern void lxc_log_options_no_override()
{
        lxc_quiet_specified = 1;
        lxc_loglevel_specified = 1;
}