locks.c

linux网络服务器工具

/* Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * Generic DAV lock implementation that a DAV provider can use.
 */

#include "apr.h"
#include "apr_strings.h"
#include "apr_file_io.h"
#include "apr_uuid.h"

#define APR_WANT_MEMFUNC
#include "apr_want.h"

#include "httpd.h"
#include "http_log.h"

#include "mod_dav.h"

#include "locks.h"


/* ---------------------------------------------------------------
 *
 * Lock database primitives
 *
 */

/*
 * LOCK DATABASES
 *
 * Lockdiscovery information is stored in the single lock database specified
 * by the DAVGenericLockDB directive.  Information about this db is stored in
 * the per-dir configuration.
 *
 * KEY
 *
 * The database is keyed by a key_type unsigned char (DAV_TYPE_FNAME)
 * followed by full path.
 *
 * VALUE
 *
 * The value consists of a list of elements.
 *    DIRECT LOCK:     [char      (DAV_LOCK_DIRECT),
 *                      char      (dav_lock_scope),
 *                      char      (dav_lock_type),
 *                      int        depth,
 *                      time_t     expires,
 *                      apr_uuid_t locktoken,
 *                      char[]     owner,
 *                      char[]     auth_user]
 *
 *    INDIRECT LOCK:   [char      (DAV_LOCK_INDIRECT),
 *                      apr_uuid_t locktoken,
 *                      time_t     expires,
 *                      int        key_size,
 *                      char[]     key]
 *       The key is to the collection lock that resulted in this indirect lock
 */

#define DAV_TRUE                    1
#define DAV_FALSE                   0

#define DAV_CREATE_LIST            23
#define DAV_APPEND_LIST            24

/* Stored lock_discovery prefix */
#define DAV_LOCK_DIRECT             1
#define DAV_LOCK_INDIRECT           2

#define DAV_TYPE_FNAME             11

/* Use the opaquelock scheme for locktokens */
struct dav_locktoken {
    apr_uuid_t uuid;
};
#define dav_compare_locktoken(plt1, plt2) \
                memcmp(&(plt1)->uuid, &(plt2)->uuid, sizeof((plt1)->uuid))


/* #################################################################
 * ### keep these structures (internal) or move fully to dav_lock?
 */

/*
 * We need to reliably size the fixed-length portion of
 * dav_lock_discovery; best to separate it into another
 * struct for a convenient sizeof, unless we pack lock_discovery.
 */
typedef struct dav_lock_discovery_fixed
{
    char scope;
    char type;
    int depth;
    time_t timeout;
} dav_lock_discovery_fixed;

typedef struct dav_lock_discovery
{
    struct dav_lock_discovery_fixed f;

    dav_locktoken *locktoken;
    const char *owner;     /* owner field from activelock */
    const char *auth_user; /* authenticated user who created the lock */
    struct dav_lock_discovery *next;
} dav_lock_discovery;

/* Indirect locks represent locks inherited from containing collections.
 * They reference the lock token for the collection the lock is
 * inherited from. A lock provider may also define a key to the
 * inherited lock, for fast datbase lookup. The key is opaque outside
 * the lock provider.
 */
typedef struct dav_lock_indirect
{
    dav_locktoken *locktoken;
    apr_datum_t key;
    struct dav_lock_indirect *next;
    time_t timeout;
} dav_lock_indirect;

/* ################################################################# */

/*
 * Stored direct lock info - full lock_discovery length:
 * prefix + Fixed length + lock token + 2 strings + 2 nulls (one for each
 * string)
 */
#define dav_size_direct(a)  (1 + sizeof(dav_lock_discovery_fixed) \
                               + sizeof(apr_uuid_t) \
                               + ((a)->owner ? strlen((a)->owner) : 0) \
                               + ((a)->auth_user ? strlen((a)->auth_user) : 0) \
                               + 2)

/* Stored indirect lock info - lock token and apr_datum_t */
#define dav_size_indirect(a) (1 + sizeof(apr_uuid_t) \
                                + sizeof(time_t) \
                                + sizeof(int) + (a)->key.dsize)

/*
 * The lockdb structure.
 *
 * The <db> field may be NULL, meaning one of two things:
 * 1) That we have not actually opened the underlying database (yet). The
 *    <opened> field should be false.
 * 2) We opened it readonly and it wasn't present.
 *
 * The delayed opening (determined by <opened>) makes creating a lockdb
 * quick, while deferring the underlying I/O until it is actually required.
 *
 * We export the notion of a lockdb, but hide the details of it. Most
 * implementations will use a database of some kind, but it is certainly
 * possible that alternatives could be used.
 */
struct dav_lockdb_private
{
    request_rec *r; /* for accessing the uuid state */
    apr_pool_t *pool; /* a pool to use */
    const char *lockdb_path; /* where is the lock database? */

    int opened; /* we opened the database */
    apr_dbm_t *db; /* if non-NULL, the lock database */
};

typedef struct
{
    dav_lockdb pub;
    dav_lockdb_private priv;
} dav_lockdb_combined;

/*
 * The private part of the lock structure.
 */
struct dav_lock_private
{
    apr_datum_t key;        /* key into the lock database */
};
typedef struct
{
    dav_lock pub;
    dav_lock_private priv;
    dav_locktoken token;
} dav_lock_combined;

/*
 * This must be forward-declared so the open_lockdb function can use it.
 */
extern const dav_hooks_locks dav_hooks_locks_generic;

static dav_error * dav_generic_dbm_new_error(apr_dbm_t *db, apr_pool_t *p,
                                             apr_status_t status)
{
    int save_errno = errno;
    int errcode;
    const char *errstr;
    dav_error *err;
    char errbuf[200];

    if (status == APR_SUCCESS) {
        return NULL;
    }

    /* There might not be a <db> if we had problems creating it. */
    if (db == NULL) {
        errcode = 1;
        errstr = "Could not open property database.";
    }
    else {
        (void) apr_dbm_geterror(db, &errcode, errbuf, sizeof(errbuf));
        errstr = apr_pstrdup(p, errbuf);
    }

    err = dav_new_error(p, HTTP_INTERNAL_SERVER_ERROR, errcode, errstr);
    err->save_errno = save_errno;
    return err;
}

/* internal function for creating locks */
static dav_lock *dav_generic_alloc_lock(dav_lockdb *lockdb, apr_datum_t key,
                                        const dav_locktoken *locktoken)
{
    dav_lock_combined *comb;

    comb = apr_pcalloc(lockdb->info->pool, sizeof(*comb));
    comb->pub.rectype = DAV_LOCKREC_DIRECT;
    comb->pub.info = &comb->priv;
    comb->priv.key = key;

    if (locktoken == NULL) {
        comb->pub.locktoken = &comb->token;
        apr_uuid_get(&comb->token.uuid);
    }
    else {
        comb->pub.locktoken = locktoken;
    }

    return &comb->pub;
}

/*
 * dav_generic_parse_locktoken
 *
 * Parse an opaquelocktoken URI into a locktoken.
 */
static dav_error * dav_generic_parse_locktoken(apr_pool_t *p,
                                               const char *char_token,
                                               dav_locktoken **locktoken_p)
{
    dav_locktoken *locktoken;

    if (ap_strstr_c(char_token, "opaquelocktoken:") != char_token) {
        return dav_new_error(p,
                             HTTP_BAD_REQUEST, DAV_ERR_LOCK_UNK_STATE_TOKEN,
                             "The lock token uses an unknown State-token "
                             "format and could not be parsed.");
    }
    char_token += 16;

    locktoken = apr_pcalloc(p, sizeof(*locktoken));
    if (apr_uuid_parse(&locktoken->uuid, char_token)) {
        return dav_new_error(p, HTTP_BAD_REQUEST, DAV_ERR_LOCK_PARSE_TOKEN,
                             "The opaquelocktoken has an incorrect format "
                             "and could not be parsed.");
    }

    *locktoken_p = locktoken;
    return NULL;
}

/*
 * dav_generic_format_locktoken
 *
 * Generate the URI for a locktoken
 */
static const char *dav_generic_format_locktoken(apr_pool_t *p,
                                                const dav_locktoken *locktoken)
{
    char buf[APR_UUID_FORMATTED_LENGTH + 1];

    apr_uuid_format(buf, &locktoken->uuid);
    return apr_pstrcat(p, "opaquelocktoken:", buf, NULL);
}

/*
 * dav_generic_compare_locktoken
 *
 * Determine whether two locktokens are the same
 */
static int dav_generic_compare_locktoken(const dav_locktoken *lt1,
                                         const dav_locktoken *lt2)
{
    return dav_compare_locktoken(lt1, lt2);
}

/*
 * dav_generic_really_open_lockdb:
 *
 * If the database hasn't been opened yet, then open the thing.
 */
static dav_error * dav_generic_really_open_lockdb(dav_lockdb *lockdb)
{
    dav_error *err;
    apr_status_t status;

    if (lockdb->info->opened) {
        return NULL;
    }

    status = apr_dbm_open(&lockdb->info->db, lockdb->info->lockdb_path,
                          lockdb->ro ? APR_DBM_READONLY : APR_DBM_RWCREATE,
                          APR_OS_DEFAULT, lockdb->info->pool);

    if (status) {
        err = dav_generic_dbm_new_error(lockdb->info->db, lockdb->info->pool,
                                        status);
        return dav_push_error(lockdb->info->pool,
                              HTTP_INTERNAL_SERVER_ERROR,
                              DAV_ERR_LOCK_OPENDB,
                              "Could not open the lock database.",
                              err);
    }

    /* all right. it is opened now. */
    lockdb->info->opened = 1;

    return NULL;
}

/*
 * dav_generic_open_lockdb:
 *
 * "open" the lock database, as specified in the global server configuration.
 * If force is TRUE, then the database is opened now, rather than lazily.
 *
 * Note that only one can be open read/write.
 */
static dav_error * dav_generic_open_lockdb(request_rec *r, int ro, int force,
                                           dav_lockdb **lockdb)
{
    dav_lockdb_combined *comb;

    comb = apr_pcalloc(r->pool, sizeof(*comb));
    comb->pub.hooks = &dav_hooks_locks_generic;
    comb->pub.ro = ro;
    comb->pub.info = &comb->priv;
    comb->priv.r = r;
    comb->priv.pool = r->pool;

    comb->priv.lockdb_path = dav_generic_get_lockdb_path(r);
    if (comb->priv.lockdb_path == NULL) {
        return dav_new_error(r->pool, HTTP_INTERNAL_SERVER_ERROR,
                             DAV_ERR_LOCK_NO_DB,
                             "A lock database was not specified with the "
                             "DAVGenericLockDB directive. One must be "
                             "specified to use the locking functionality.");
    }

    /* done initializing. return it. */
    *lockdb = &comb->pub;

    if (force) {
        /* ### add a higher-level comment? */
        return dav_generic_really_open_lockdb(*lockdb);
    }

    return NULL;
}

/*
 * dav_generic_close_lockdb:
 *
 * Close it. Duh.
 */
static void dav_generic_close_lockdb(dav_lockdb *lockdb)
{
    if (lockdb->info->db != NULL) {
        apr_dbm_close(lockdb->info->db);
    }
    lockdb->info->opened = 0;
}

/*
 * dav_generic_build_key
 *
 * Given a pathname, build a DAV_TYPE_FNAME lock database key.
 */
static apr_datum_t dav_generic_build_key(apr_pool_t *p,
                                         const dav_resource *resource)
{
    apr_datum_t key;
    const char *pathname = resource->uri;