From: Andre Noll Date: Fri, 17 Feb 2017 14:29:52 +0000 (+0100) Subject: ipc.c: Use ftok() instead of SuperFastHash. X-Git-Tag: v1.0.0~30 X-Git-Url: http://git.tue.mpg.de/?a=commitdiff_plain;h=c92370affe722f38a85a41d1b5524e4a102b8f4d;p=dss.git ipc.c: Use ftok() instead of SuperFastHash. ftok(3) uses the identity of the named file to generate a key_t type System V IPC key, which is easier than computing the key by hashing the (resolved) pathname of the config file. This change allows to get rid of the realpath() and the super_fast_hash() implementation. If ftok(3) fails, presumably because the underlying call to stat(2) fails, we now simply return a phony identifier, similar to what we did before in this case. This eliminates the only possible failure path in get_key_or_die(), so this function is renamed to get_key(). --- diff --git a/ipc.c b/ipc.c index c55554c..723570e 100644 --- a/ipc.c +++ b/ipc.c @@ -22,240 +22,22 @@ #include "err.h" #include "ipc.h" -#if (defined(__GNUC__) && defined(__i386__)) -#define get16bits(d) (*((const uint16_t *) (d))) -#else -#define get16bits(d) ((((uint32_t)(((const uint8_t *)(d))[1])) << 8)\ - +(uint32_t)(((const uint8_t *)(d))[0]) ) -#endif - -/* - * SuperFastHash, by Paul Hsieh. - * http://www.azillionmonkeys.com/qed/hash.html - */ -static uint32_t super_fast_hash(const uint8_t *data, uint32_t len, uint32_t hash) -{ - uint32_t tmp; - int rem = len & 3; - - len >>= 2; - - for (;len > 0; len--) { - hash += get16bits (data); - tmp = (get16bits (data+2) << 11) ^ hash; - hash = (hash << 16) ^ tmp; - data += 2*sizeof (uint16_t); - hash += hash >> 11; - } - - /* Handle end cases */ - switch (rem) { - case 3: - hash += get16bits (data); - hash ^= hash << 16; - hash ^= data[sizeof (uint16_t)] << 18; - hash += hash >> 11; - break; - case 2: - hash += get16bits (data); - hash ^= hash << 11; - hash += hash >> 17; - break; - case 1: - hash += *data; - hash ^= hash << 10; - hash += hash >> 1; - } - /* Force "avalanching" of final 127 bits */ - hash ^= hash << 3; - hash += hash >> 5; - hash ^= hash << 4; - hash += hash >> 17; - hash ^= hash << 25; - hash += hash >> 6; - return hash; -} - -/* - * Return the canonical absolute name of a given file name. - * - * Slightly modified version of glibc's realpath, Copyright (C) - * 1996-2002,2004,2005,2006,2008 Free Software Foundation, Inc. - * - * A canonical name does not contain any `.', `..' components nor any repeated - * path separators ('/') or symlinks. All path components must exist. The - * result is malloc'd and must be freed by the caller. - */ -static int dss_realpath(const char *name, char **resolved_path) -{ - char *rpath = NULL, *dest, *extra_buf = NULL; - const char *start, *end, *rpath_limit; - long int path_max; - int ret, num_links = 0; - - if (name[0] == '\0') { - /* - * As per Single Unix Specification V2 we must return an error - * if the name argument points to an empty string. - */ - ret = -ERRNO_TO_DSS_ERROR(ENOENT); - goto error; - } -#ifdef PATH_MAX - path_max = PATH_MAX; -#else - /* - * From realpath(3): Asking pathconf(3) does not really help, since on - * the one hand POSIX warns that the result of pathconf(3) may be - * huge and unsuitable for mallocing memory. And on the other hand - * pathconf(3) may return -1 to signify that PATH_MAX is not bounded. - */ - path_max = pathconf(name, _PC_PATH_MAX); - if (path_max <= 0 || path_max >= 4096) - path_max = 4096; -#endif - rpath = dss_malloc(path_max); - rpath_limit = rpath + path_max; - - if (name[0] != '/') { - if (!getcwd(rpath, path_max)) { - ret = -ERRNO_TO_DSS_ERROR(errno); - goto error; - } - dest = memchr(rpath, '\0', path_max); - } else { - rpath[0] = '/'; - dest = rpath + 1; - } - - for (start = end = name; *start; start = end) { - struct stat st; - int n; - - /* Skip sequence of multiple path-separators. */ - while (*start == '/') - ++start; - - /* Find end of path component. */ - for (end = start; *end && *end != '/'; ++end) - /* Nothing. */ ; - - if (end - start == 0) - break; - else if (end - start == 1 && start[0] == '.') - /* nothing */ ; - else if (end - start == 2 && start[0] == '.' && start[1] == '.') { - /* Back up to previous component, ignore if at root already. */ - if (dest > rpath + 1) - while ((--dest)[-1] != '/') ; - } else { - size_t new_size; - - if (dest[-1] != '/') - *dest++ = '/'; - - if (dest + (end - start) >= rpath_limit) { - ptrdiff_t dest_offset = dest - rpath; - - new_size = rpath_limit - rpath; - if (end - start + 1 > path_max) - new_size += end - start + 1; - else - new_size += path_max; - rpath = dss_realloc(rpath, new_size); - rpath_limit = rpath + new_size; - dest = rpath + dest_offset; - } - - memcpy(dest, start, end - start); - dest += end - start; - *dest = '\0'; - - if (stat(rpath, &st) < 0) { - ret = -ERRNO_TO_DSS_ERROR(errno); - goto error; - } - - if (S_ISLNK(st.st_mode)) { - char *buf = alloca(path_max); - size_t len; - - if (++num_links > MAXSYMLINKS) { - ret = -ERRNO_TO_DSS_ERROR(ELOOP); - goto error; - } - - n = readlink(rpath, buf, path_max - 1); - if (n < 0) { - ret = -ERRNO_TO_DSS_ERROR(errno); - goto error; - } - buf[n] = '\0'; - - if (!extra_buf) - extra_buf = alloca(path_max); - - len = strlen(end); - if ((long int) (n + len) >= path_max) { - ret = -ERRNO_TO_DSS_ERROR(ENAMETOOLONG); - goto error; - } - - /* Careful here, end may be a pointer into extra_buf... */ - memmove(&extra_buf[n], end, len + 1); - name = end = memcpy(extra_buf, buf, n); - - if (buf[0] == '/') /* It's an absolute symlink */ - dest = rpath + 1; - else /* Back up to previous component, ignore if at root already: */ - if (dest > rpath + 1) - while ((--dest)[-1] != '/') - ; /* nothing */ - } else if (!S_ISDIR(st.st_mode) && *end != '\0') { - ret = -ERRNO_TO_DSS_ERROR(ENOTDIR); - goto error; - } - } - } - if (dest > rpath + 1 && dest[-1] == '/') - --dest; - *dest = '\0'; - *resolved_path = rpath; - return 1; -error: - free(rpath); - *resolved_path = NULL; - return ret; -} - -static int get_key_or_die(const char *config_file) +static int get_key(const char *config_file) { int ret; - struct stat statbuf; - char *rpath; assert(config_file); - if (stat(config_file, &statbuf) == 0) { - ret = dss_realpath(config_file, &rpath); - if (ret < 0) { - DSS_EMERG_LOG(("could not resolve path %s: %s\n", config_file, - dss_strerror(-ret))); - exit(EXIT_FAILURE); - } - DSS_DEBUG_LOG(("resolved path: %s\n", rpath)); - } else - /* - * This happens if the user did not specify a config file, and - * the default config file does not exist. Another (unlikely) - * possibility is that the config file was removed between - * startup and this call. We don't care about these corner - * cases too much and just use the unresolved path in this - * case. - */ - rpath = dss_strdup(config_file); - ret = super_fast_hash((uint8_t *)rpath, strlen(rpath), 0) >> 1; - free(rpath); - return ret; + ret = ftok(config_file, 'D'); + if (ret >= 0) + return ret; + /* + * This happens if the user did not specify a config file, and the + * default config file does not exist. Another (unlikely) possibility + * is that the config file was removed between startup and this call. + * We don't care about these corner cases too much and just return a + * fixed key in this case. + */ + return 0x0D55; /* no magic, this number just looks a bit like DSS */ } static int mutex_get(int key, int flags) @@ -326,7 +108,7 @@ static bool mutex_is_locked(int id) int lock_dss(char *config_file) { - int ret, key = get_key_or_die(config_file); + int ret, key = get_key(config_file); ret = mutex_get(key, IPC_CREAT | 0600); if (ret < 0) @@ -336,7 +118,7 @@ int lock_dss(char *config_file) int get_dss_pid(char *config_file, pid_t *pid) { - int ret, semid, key = get_key_or_die(config_file); + int ret, semid, key = get_key(config_file); if (pid) *pid = 0;