exfile.c

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/*
 *   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 St, Fifth Floor, Boston, MA 02110-1301, USA
 */
 
/*
 * $Id: 9602d7e7e2f0c584a973de5f978c63392f9a6f64 $
 *
 * @file exfile.c
 * @brief Allow multiple threads to write to the same set of files.
 *
 * @author Alan DeKok (aland@freeradius.org)
 * @copyright 2014 The FreeRADIUS server project
 */
#define _EXFILE_PRIVATE 1
#include <freeradius-devel/protocol/freeradius/freeradius.internal.h>
#include <freeradius-devel/server/exfile.h>
#include <freeradius-devel/server/trigger.h>
 
#include <freeradius-devel/util/debug.h>
#include <freeradius-devel/util/file.h>
#include <freeradius-devel/util/misc.h>
#include <freeradius-devel/util/perm.h>
#include <freeradius-devel/util/syserror.h>
 
#include <fcntl.h>
 
typedef enum : uint8_t {
        EXFILE_TRIGGER_OPEN = 0,
        EXFILE_TRIGGER_CLOSE,
        EXFILE_TRIGGER_RESERVE,
        EXFILE_TRIGGER_RELEASE,
        EXFILE_TRIGGER_MAX
} exfile_trigger_t;
 
static const char * exfile_trigger_names[EXFILE_TRIGGER_MAX] = {
        "open",
        "close",
        "reserve",
        "release"
};
 
typedef struct {
        int                     fd;                     //!< File descriptor associated with an entry.
        uint32_t                hash;                   //!< Hash for cheap comparison.
        fr_time_t               last_used;              //!< Last time the entry was used.
        dev_t                   st_dev;                 //!< device inode
        ino_t                   st_ino;                 //!< inode number
        char                    *filename;              //!< Filename.
} exfile_entry_t;
 
 
struct exfile_s {
        uint32_t                max_entries;            //!< How many file descriptors we keep track of.
        fr_time_delta_t         max_idle;               //!< Maximum idle time for a descriptor.
                                                        ///< If this is zero, the descriptor will be closed
                                                        ///< immediately after it is unlocked.
        fr_time_t               last_cleaned;
        pthread_mutex_t         mutex;
        exfile_entry_t          *entries;
        bool                    locking;
        CONF_SECTION            *conf;                  //!< Conf section to search for triggers.
        char const              *trigger_prefix;        //!< Trigger path in the global trigger section.
        fr_pair_list_t          trigger_args;           //!< Arguments to pass to trigger.
        bool                    trigger_undef[EXFILE_TRIGGER_MAX];      //!< Is the trigger undefined
        CONF_PAIR               *trigger_cp[EXFILE_TRIGGER_MAX];        //!< Cache of trigger CONF_PAIRs
};
 
#define MAX_TRY_LOCK 4                  //!< How many times we attempt to acquire a lock
                                        //!< before giving up.
 
/** Send an exfile trigger.
 *
 * @param[in] ef to send trigger for.
 * @param[in] entry for the file that the event occurred on.
 * @param[in] ex_trigger to fire.
 */
static inline void exfile_trigger(exfile_t *ef, exfile_entry_t *entry, exfile_trigger_t ex_trigger)
{
        char                    name[128];
        fr_pair_t               *vp;
        fr_pair_list_t          args;
        fr_dict_attr_t const    *da;
 
        if (ef->trigger_undef[ex_trigger]) return;
 
        fr_pair_list_init(&args);
        fr_assert(ef != NULL);
        fr_assert(ex_trigger < EXFILE_TRIGGER_MAX);
 
        if (!ef->trigger_prefix) return;
 
        da = fr_dict_attr_child_by_num(fr_dict_root(fr_dict_internal()), FR_EXFILE_NAME);
        if (!da) {
                ERROR("Incomplete internal dictionary: Missing definition for \"Exfile-Name\"");
                return;
        }
 
        (void) fr_pair_list_copy(NULL, &args, &ef->trigger_args);
 
        fr_pair_list_prepend_by_da_len(NULL, vp, &args, da, entry->filename,
                                       talloc_strlen(entry->filename), false);
 
        snprintf(name, sizeof(name), "%s.%s", ef->trigger_prefix, exfile_trigger_names[ex_trigger]);
        if (trigger(unlang_interpret_get_thread_default(), ef->conf, &ef->trigger_cp[ex_trigger], name, false, &args, NULL) == -1) {
                ef->trigger_undef[ex_trigger] = true;
        }
 
        fr_pair_list_free(&args);
}
 
 
static void exfile_cleanup_entry(exfile_t *ef, exfile_entry_t *entry)
{
        if (entry->fd >= 0) close(entry->fd);
 
        entry->hash = 0;
        entry->fd = -1;
 
        /*
         *      Issue close trigger *after* we've closed the fd
         */
        exfile_trigger(ef, entry, EXFILE_TRIGGER_CLOSE);
 
        /*
         *      Trigger still needs access to filename to populate Exfile-Name
         */
        TALLOC_FREE(entry->filename);
}
 
 
static int _exfile_free(exfile_t *ef)
{
        uint32_t i;
 
        pthread_mutex_lock(&ef->mutex);
 
        for (i = 0; i < ef->max_entries; i++) {
                if (!ef->entries[i].filename) continue;
 
                exfile_cleanup_entry(ef, &ef->entries[i]);
        }
 
        pthread_mutex_unlock(&ef->mutex);
        pthread_mutex_destroy(&ef->mutex);
 
        return 0;
}
 
/** Initialize a way for multiple threads to log to one or more files.
 *
 * @param ctx The talloc context
 * @param max_entries Max file descriptors to cache, and manage locks for.
 * @param max_idle Maximum time a file descriptor can be idle before it's closed.
 * @param locking whether or not to lock the files.
 * @return
 *      - new context.
 *      - NULL on error.
 */
exfile_t *exfile_init(TALLOC_CTX *ctx, uint32_t max_entries, fr_time_delta_t max_idle, bool locking)
{
        exfile_t *ef;
 
        ef = talloc_zero(NULL, exfile_t);
        if (!ef) return NULL;
        fr_pair_list_init(&ef->trigger_args);
 
        talloc_link_ctx(ctx, ef);
 
        ef->max_entries = max_entries;
        ef->max_idle = max_idle;
        ef->locking = locking;
 
        /*
         *      If we're not locking the files, just return the
         *      handle.  Each call to exfile_open() will just open a
         *      new file descriptor.
         */
        if (!ef->locking) return ef;
 
        ef->entries = talloc_zero_array(ef, exfile_entry_t, max_entries);
        if (!ef->entries) {
                talloc_free(ef);
                return NULL;
        }
 
        if (pthread_mutex_init(&ef->mutex, NULL) != 0) {
                talloc_free(ef);
                return NULL;
        }
 
        talloc_set_destructor(ef, _exfile_free);
 
        return ef;
}
 
/** Enable triggers for an exfiles handle
 *
 * @param[in] ef to enable triggers for.
 * @param[in] conf section to search for triggers in.
 * @param[in] trigger_prefix prefix to prepend to all trigger names.  Usually a path
 *      to the module's trigger configuration .e.g.
 *      @verbatim modules.<name>.file @endverbatim
 *      @verbatim <trigger name> @endverbatim is appended to form the complete path.
 * @param[in] trigger_args to make available in any triggers executed by the exfile api.
 *      Exfile-File is automatically added to this list.
 */
void exfile_enable_triggers(exfile_t *ef, CONF_SECTION *conf, char const *trigger_prefix, fr_pair_list_t *trigger_args)
{
        talloc_const_free(ef->trigger_prefix);
        MEM(ef->trigger_prefix = trigger_prefix ? talloc_strdup(ef, trigger_prefix) : talloc_strdup(ef, ""));
 
        fr_pair_list_free(&ef->trigger_args);
 
        ef->conf = conf;
 
        if (!trigger_args) return;
 
        (void) fr_pair_list_copy(ef, &ef->trigger_args, trigger_args);
}
 
 
/*
 *      Try to open the file. It it doesn't exist, try to
 *      create it's parent directories.
 */
static int exfile_open_mkdir(char const *filename, mode_t permissions, int flags)
{
        int fd;
 
        fd = open(filename, O_RDWR | O_CREAT | flags, permissions);
        if (fd < 0) {
                int dirfd;
                mode_t dirperm;
                char *p, *dir;
 
                /*
                 *      Maybe the directory doesn't exist.  Try to
                 *      create it.
                 */
                dir = talloc_strdup(NULL, filename);
                if (!dir) return -1;
                p = strrchr(dir, FR_DIR_SEP);
                if (!p) {
                        fr_strerror_printf("No '/' in '%s'", filename);
                        talloc_free(dir);
                        return -1;
                }
                *p = '\0';
 
                /*
                 *      Ensure that the 'x' bit is set, so that we can
                 *      read the directory.
                 */
                dirperm = permissions;
                if ((dirperm & 0600) != 0) dirperm |= 0100;
                if ((dirperm & 0060) != 0) dirperm |= 0010;
                if ((dirperm & 0006) != 0) dirperm |= 0001;
 
                if (fr_mkdir(&dirfd, dir, -1, dirperm, NULL, NULL) < 0) {
                        fr_strerror_printf("Failed to create directory %s: %s", dir, fr_syserror(errno));
                        talloc_free(dir);
                        return -1;
                }
 
                fd = openat(dirfd, p+1, O_RDWR | O_CREAT | flags, permissions);
                talloc_free(dir);
                close(dirfd);
 
                if (fd < 0) {
                        fr_strerror_printf("Failed to open file %s: %s", filename, fr_syserror(errno));
                        return -1;
                }
        }
 
        return fd;
}
 
/*
 * exfile_open() calls exfile_open_lock() when ef->locking is true.
 * exfile_open_lock() returns holding ef->mutex on success, and returns
 * without holding ef->mutex on failure.  exfile.h gives Coverity the
 * same contract at each call site.
 */
static int exfile_open_lock(exfile_t *ef, char const *filename, mode_t permissions, int flags, off_t *offset)
{
        int i, tries, unused = -1, found = -1, oldest = -1;
        bool do_cleanup = false;
        uint32_t hash;
        fr_time_t now;
        struct stat st;
        off_t real_offset;
 
        /*
         *      It's faster to do hash comparisons of a string than
         *      full string comparisons.
         */
        hash = fr_hash_string(filename);
        now = fr_time();
        unused = -1;
 
        pthread_mutex_lock(&ef->mutex);
 
        if (fr_time_gt(now, fr_time_add(ef->last_cleaned, fr_time_delta_from_sec(1)))) do_cleanup = true;
 
        /*
         *      Find the matching entry, or an unused one.
         *
         *      Also track which entry is the oldest, in case there
         *      are no unused entries.
         */
        for (i = 0; i < (int) ef->max_entries; i++) {
                if (!ef->entries[i].filename) {
                        if (unused < 0) unused = i;
                        continue;
                }
 
                if ((oldest < 0) ||
                    (fr_time_lt(ef->entries[i].last_used, ef->entries[oldest].last_used))) {
                        oldest = i;
                }
 
                /*
                 *      Hash comparisons are fast.  String comparisons are slow.
                 *
                 *      But we still need to do string comparisons if
                 *      the hash matches, because 1/2^16 filenames
                 *      will result in a hash collision.  And that's
                 *      enough filenames in a long-running server to
                 *      ensure that it happens.
                 */
                if ((found < 0) &&
                    (ef->entries[i].hash == hash) &&
                    (strcmp(ef->entries[i].filename, filename) == 0)) {
                        found = i;
 
                        /*
                         *      If we're not cleaning up, stop now.
                         */
                        if (!do_cleanup) break;
 
                        /*
                         *      If we are cleaning up, then clean up
                         *      entries OTHER than the one we found,
                         *      do so now.
                         */
                } else if (do_cleanup) {
                        if (fr_time_gteq(fr_time_add(ef->entries[i].last_used, ef->max_idle), now)) continue;
 
                        exfile_cleanup_entry(ef, &ef->entries[i]);
                }
        }
 
        if (do_cleanup) ef->last_cleaned = now;
 
        /*
         *      We found an existing entry, return that.
         */
        if (found >= 0) {
                i = found;
 
                /*
                 *      Stat the *filename*, not the file we opened.
                 *      If that's not the file we opened, then go back
                 *      and re-open the file.
                 */
                if (stat(ef->entries[i].filename, &st) < 0) {
                        goto close_reopen;
                }
 
                if ((st.st_dev != ef->entries[i].st_dev) ||
                    (st.st_ino != ef->entries[i].st_ino)) {
                close_reopen:
                        close(ef->entries[i].fd);
                        goto reopen_reset;
                }
 
                goto try_lock;
        }
 
        /*
         *      There are no unused entries, free the oldest one.
         */
        if (unused < 0) {
                exfile_cleanup_entry(ef, &ef->entries[oldest]);
                unused = oldest;
        }
 
        /*
         *      Create a new entry.
         */
        i = unused;
 
        ef->entries[i].hash = hash;
        ef->entries[i].filename = talloc_strdup(ef->entries, filename);
 
reopen_reset:
        ef->entries[i].fd = -1;
 
        ef->entries[i].fd = exfile_open_mkdir(filename, permissions, flags);
        if (ef->entries[i].fd < 0) goto error;
 
        exfile_trigger(ef, &ef->entries[i], EXFILE_TRIGGER_OPEN);
 
try_lock:
        /*
         *      Lock from the start of the file.
         */
        if (lseek(ef->entries[i].fd, 0, SEEK_SET) < 0) {
                fr_strerror_printf("Failed to seek in file %s: %s", filename, fr_syserror(errno));
 
        error:
                exfile_cleanup_entry(ef, &ef->entries[i]);
                pthread_mutex_unlock(&(ef->mutex));
                return -1;
        }
 
        /*
         *      Try to lock it.  If we can't lock it, it's because
         *      some reader has re-named the file to "foo.work" and
         *      locked it.  So, we close the current file, re-open it,
         *      and try again/
         */
        for (tries = 0; tries < MAX_TRY_LOCK; tries++) {
                if (rad_lockfd_nonblock(ef->entries[i].fd, 0) >= 0) break;
 
                if (errno != EAGAIN) {
                        fr_strerror_printf("Failed to lock file %s: %s", filename, fr_syserror(errno));
                        goto error;
                }
 
                close(ef->entries[i].fd);
                ef->entries[i].fd = open(filename, O_RDWR | O_CREAT | flags, permissions);
                if (ef->entries[i].fd < 0) {
                        fr_strerror_printf("Failed to open file %s: %s", filename, fr_syserror(errno));
                        goto error;
                }
        }
 
        if (tries >= MAX_TRY_LOCK) {
                fr_strerror_printf("Failed to lock file %s: too many tries", filename);
                goto error;
        }
 
        /*
         *      Maybe someone deleted the file while we were waiting
         *      for the lock.  If so, re-open it.
         */
        if (fstat(ef->entries[i].fd, &st) < 0) goto close_reopen;
 
        if (st.st_nlink == 0) goto close_reopen;
 
        /*
         *      Remember which device and inode this file is
         *      for.
         */
        ef->entries[i].st_dev = st.st_dev;
        ef->entries[i].st_ino = st.st_ino;
 
        /*
         *      Sometimes the file permissions are changed externally.
         *      just be sure to update the permission if necessary.
         */
        if ((st.st_mode & ~S_IFMT)  != permissions) {
                char str_need[10], oct_need[5];
                char str_have[10], oct_have[5];
 
                fr_perm_mode_to_oct(oct_need, permissions);
                fr_perm_mode_to_str(str_need, permissions);
 
                fr_perm_mode_to_oct(oct_have, st.st_mode & ~S_IFMT);
                fr_perm_mode_to_str(str_have, st.st_mode & ~S_IFMT);
 
                WARN("File %s permissions are %s (%s) not %s (%s))", filename,
                     oct_have, str_have, oct_need, str_need);
 
                if (((st.st_mode | permissions) != st.st_mode) &&
                    (fchmod(ef->entries[i].fd, (st.st_mode & ~S_IFMT) | permissions) < 0)) {
                        fr_perm_mode_to_oct(oct_need, (st.st_mode & ~S_IFMT) | permissions);
                        fr_perm_mode_to_str(str_need, (st.st_mode & ~S_IFMT) | permissions);
 
                        WARN("Failed resetting file %s permissions to %s (%s): %s",
                             filename, oct_need, str_need, fr_syserror(errno));
                }
        }
 
        /*
         *      Seek to the end of the file before returning the FD to
         *      the caller.
         */
        real_offset = lseek(ef->entries[i].fd, 0, SEEK_END);
        if (offset) *offset = real_offset;
 
        /*
         *      Return holding the mutex for the entry.
         */
        ef->entries[i].last_used = now;
 
        exfile_trigger(ef, &ef->entries[i], EXFILE_TRIGGER_RESERVE);
 
        /*
         *      Every path here called lseek() on the fd at try_lock, which
         *      fails for an invalid fd and goes to error, so the fd is valid,
         *      and the caller only ever holds the mutex with an fd >= 0.
         */
        fr_assert(ef->entries[i].fd >= 0);
 
#ifdef __COVERITY__
        /*
         *      The caller holds ef->mutex until exfile_close().  The
         *      macros in exfile.h tell Coverity about the lock at the call
         *      site.  Here Coverity must see ef->mutex released.
         */
        __coverity_exclusive_lock_release__(&ef->mutex);
#endif
        return ef->entries[i].fd;
}
 
/** Open a new log file, or maybe an existing one.
 *
 * When multithreaded, the FD is locked via a mutex.  This way we're
 * sure that no other thread is writing to the file.
 *
 * On success the mutex is held until exfile_close() is called.  On
 * failure the mutex is not held.
 *
 * @param ef The logfile context returned from exfile_init().
 * @param filename the file to open.
 * @param permissions to use.
 * @param flags flags to pass to open.
 * @param offset Optional pointer to store offset in when seeking the end of file.
 * @return
 *      - FD used to write to the file.
 *      - -1 on failure.
 */
int exfile_open(exfile_t *ef, char const *filename, mode_t permissions, int flags, off_t *offset)
{
        if (!ef || !filename) return -1;
 
        if (!ef->locking) {
                int found = exfile_open_mkdir(filename, permissions, flags);
                off_t real_offset;
 
                if (found < 0) return -1;
                real_offset = lseek(found, 0, SEEK_END);
                if (offset) *offset = real_offset;
                return found;
        }
 
        return exfile_open_lock(ef, filename, permissions, flags, offset);
}
 
/*
 * exfile_close() calls exfile_close_lock() when ef->locking is true.
 * exfile_close_lock() releases ef->mutex on every return path.
 */
static int exfile_close_lock(exfile_t *ef, int fd)
{
        uint32_t i;
 
#ifdef __COVERITY__
        /*
         *      The caller has held ef->mutex since exfile_open().  The
         *      macros in exfile.h tell Coverity about the lock at the call
         *      site.  Here Coverity must see ef->mutex taken.
         */
        __coverity_exclusive_lock_acquire__(&ef->mutex);
#endif
 
        /*
         *      Unlock the bytes that we had previously locked.
         */
        for (i = 0; i < ef->max_entries; i++) {
                if (ef->entries[i].fd != fd) continue;
 
                (void) lseek(ef->entries[i].fd, 0, SEEK_SET);
                (void) rad_unlockfd(ef->entries[i].fd, 0);
 
                /*
                 *      If max idle is 0, then clean up the file immediately
                 *      this is mostly used for testing.
                 */
                if (fr_time_delta_eq(ef->max_idle, fr_time_delta_from_sec(0))) {
                        exfile_cleanup_entry(ef, &ef->entries[i]);
                        pthread_mutex_unlock(&(ef->mutex));
                        return 0;
                }
 
                pthread_mutex_unlock(&(ef->mutex));
 
                exfile_trigger(ef, &ef->entries[i], EXFILE_TRIGGER_RELEASE);
                return 0;
        }
 
        pthread_mutex_unlock(&(ef->mutex));
 
        fr_strerror_const("Attempt to unlock file which is not tracked");
        return -1;
}
 
/** Close the log file.  Really just return it to the pool.
 *
 * When multithreaded, the FD is locked via a mutex. This way we're sure that no other thread is
 * writing to the file. This function will unlock the mutex, so that other threads can write to
 * the file.
 *
 * @param ef The logfile context returned from #exfile_init.
 * @param fd the FD to close (i.e. return to the pool).
 * @return
 *      - 0 on success.
 *      - -1 on failure.
 */
int exfile_close(exfile_t *ef, int fd)
{
        if (!ef->locking) {
                /*
                 *      No locking: just close the file.
                 */
                close(fd);
                return 0;
        }
        return exfile_close_lock(ef, fd);
}