/* cache.c: cache management * * Copyright (C) 2006-2014 cgit Development Team <cgit@lists.zx2c4.com> * * Licensed under GNU General Public License v2 *   (see COPYING for full license text) * * * The cache is just a directory structure where each file is a cache slot, * and each filename is based on the hash of some key (e.g. the cgit url). * Each file contains the full key followed by the cached content for that * key. * */ #include "cgit.h"#include "cache.h"#include "html.h"#ifdef HAVE_LINUX_SENDFILE#include <sys/sendfile.h>#endif #define CACHE_BUFSIZE (1024 * 4) struct cache_slot {	const char *key;	size_t keylen;	int ttl;	cache_fill_fn fn;	int cache_fd;	int lock_fd;	int stdout_fd;	const char *cache_name;	const char *lock_name;	int match;	struct stat cache_st;	int bufsize;	char buf[CACHE_BUFSIZE];}; /* Open an existing cache slot and fill the cache buffer with * (part of) the content of the cache file. Return 0 on success * and errno otherwise. */static int open_slot(struct cache_slot *slot){	char *bufz;	ssize_t bufkeylen = -1; 	slot->cache_fd = open(slot->cache_name, O_RDONLY);	if (slot->cache_fd == -1)		return errno; 	if (fstat(slot->cache_fd, &slot->cache_st))		return errno; 	slot->bufsize = xread(slot->cache_fd, slot->buf, sizeof(slot->buf));	if (slot->bufsize < 0)		return errno; 	bufz = memchr(slot->buf, 0, slot->bufsize);	if (bufz)		bufkeylen = bufz - slot->buf; 	if (slot->key)		slot->match = bufkeylen == slot->keylen &&		    !memcmp(slot->key, slot->buf, bufkeylen + 1); 	return 0;} /* Close the active cache slot */static int close_slot(struct cache_slot *slot){	int err = 0;	if (slot->cache_fd > 0) {		if (close(slot->cache_fd))			err = errno;		else			slot->cache_fd = -1;	}	return err;} /* Print the content of the active cache slot (but skip the key). */static int print_slot(struct cache_slot *slot){	off_t off;#ifdef HAVE_LINUX_SENDFILE	off_t size;#endif 	off = slot->keylen + 1; #ifdef HAVE_LINUX_SENDFILE	size = slot->cache_st.st_size; 	do {		ssize_t ret;		ret = sendfile(STDOUT_FILENO, slot->cache_fd, &off, size - off);		if (ret < 0) {			if (errno == EAGAIN || errno == EINTR)				continue;			/* Fall back to read/write on EINVAL or ENOSYS */			if (errno == EINVAL || errno == ENOSYS)				break;			return errno;		}		if (off == size)			return 0;	} while (1);#endif 	if (lseek(slot->cache_fd, off, SEEK_SET) != off)		return errno; 	do {		ssize_t ret;		ret = xread(slot->cache_fd, slot->buf, sizeof(slot->buf));		if (ret < 0)			return errno;		if (ret == 0)			return 0;		if (write_in_full(STDOUT_FILENO, slot->buf, ret) < 0)			return errno;	} while (1);} /* Check if the slot has expired */static int is_expired(struct cache_slot *slot){	if (slot->ttl < 0)		return 0;	else		return slot->cache_st.st_mtime + slot->ttl * 60 < time(NULL);} /* Check if the slot has been modified since we opened it. * NB: If stat() fails, we pretend the file is modified. */static int is_modified(struct cache_slot *slot){	struct stat st; 	if (stat(slot->cache_name, &st))		return 1;	return (st.st_ino != slot->cache_st.st_ino ||		st.st_mtime != slot->cache_st.st_mtime ||		st.st_size != slot->cache_st.st_size);} /* Close an open lockfile */static int close_lock(struct cache_slot *slot){	int err = 0;	if (slot->lock_fd > 0) {		if (close(slot->lock_fd))			err = errno;		else			slot->lock_fd = -1;	}	return err;} /* Create a lockfile used to store the generated content for a cache * slot, and write the slot key + \0 into it. * Returns 0 on success and errno otherwise. */static int lock_slot(struct cache_slot *slot){	struct flock lock = {		.l_type = F_WRLCK,		.l_whence = SEEK_SET,		.l_start = 0,		.l_len = 0,	}; 	slot->lock_fd = open(slot->lock_name, O_RDWR | O_CREAT,			     S_IRUSR | S_IWUSR);	if (slot->lock_fd == -1)		return errno;	if (fcntl(slot->lock_fd, F_SETLK, &lock) < 0) {		int saved_errno = errno;		close(slot->lock_fd);		slot->lock_fd = -1;		return saved_errno;	}	if (ftruncate(slot->lock_fd, 0) < 0)		return errno;	if (xwrite(slot->lock_fd, slot->key, slot->keylen + 1) < 0)		return errno;	return 0;} /* Release the current lockfile. If `replace_old_slot` is set the * lockfile replaces the old cache slot, otherwise the lockfile is * just deleted. */static int unlock_slot(struct cache_slot *slot, int replace_old_slot){	int err; 	if (replace_old_slot)		err = rename(slot->lock_name, slot->cache_name);	else		err = unlink(slot->lock_name); 	/* Restore stdout and close the temporary FD. */	if (slot->stdout_fd >= 0) {		dup2(slot->stdout_fd, STDOUT_FILENO);		close(slot->stdout_fd);		slot->stdout_fd = -1;	} 	if (err)		return errno; 	return 0;} /* Generate the content for the current cache slot by redirecting * stdout to the lock-fd and invoking the callback function */static int fill_slot(struct cache_slot *slot){	/* Preserve stdout */	slot->stdout_fd = dup(STDOUT_FILENO);	if (slot->stdout_fd == -1)		return errno; 	/* Redirect stdout to lockfile */	if (dup2(slot->lock_fd, STDOUT_FILENO) == -1)		return errno; 	/* Generate cache content */	slot->fn(); 	/* Make sure any buffered data is flushed to the file */	if (fflush(stdout))		return errno; 	/* update stat info */	if (fstat(slot->lock_fd, &slot->cache_st))		return errno; 	return 0;} /* Crude implementation of 32-bit FNV-1 hash algorithm, * see http://www.isthe.com/chongo/tech/comp/fnv/ for details * about the magic numbers. */#define FNV_OFFSET 0x811c9dc5#define FNV_PRIME  0x01000193 unsigned long hash_str(const char *str){	unsigned long h = FNV_OFFSET;	unsigned char *s = (unsigned char *)str; 	if (!s)		return h; 	while (*s) {		h *= FNV_PRIME;		h ^= *s++;	}	return h;} static int process_slot(struct cache_slot *slot){	int err; 	err = open_slot(slot);	if (!err && slot->match) {		if (is_expired(slot)) {			if (!lock_slot(slot)) {				/* If the cachefile has been replaced between				 * `open_slot` and `lock_slot`, we'll just				 * serve the stale content from the original				 * cachefile. This way we avoid pruning the				 * newly generated slot. The same code-path				 * is chosen if fill_slot() fails for some				 * reason.				 *				 * TODO? check if the new slot contains the				 * same key as the old one, since we would				 * prefer to serve the newest content.				 * This will require us to open yet another				 * file-descriptor and read and compare the				 * key from the new file, so for now we're				 * lazy and just ignore the new file.				 */				if (is_modified(slot) || fill_slot(slot)) {					unlock_slot(slot, 0);					close_lock(slot);				} else {					close_slot(slot);					unlock_slot(slot, 1);					slot->cache_fd = slot->lock_fd;				}			}		}		if ((err = print_slot(slot)) != 0) {			cache_log("[cgit] error printing cache %s: %s (%d)\n",				  slot->cache_name,				  strerror(err),				  err);		}		close_slot(slot);		return err;	} 	/* If the cache slot does not exist (or its key doesn't match the	 * current key), lets try to create a new cache slot for this	 * request. If this fails (for whatever reason), lets just generate	 * the content without caching it and fool the caller to believe	 * everything worked out (but print a warning on stdout).	 */ 	close_slot(slot);	if ((err = lock_slot(slot)) != 0) {		cache_log("[cgit] Unable to lock slot %s: %s (%d)\n",			  slot->lock_name, strerror(err), err);		slot->fn();		return 0;	} 	if ((err = fill_slot(slot)) != 0) {		cache_log("[cgit] Unable to fill slot %s: %s (%d)\n",			  slot->lock_name, strerror(err), err);		unlock_slot(slot, 0);		close_lock(slot);		slot->fn();		return 0;	}	// We've got a valid cache slot in the lock file, which	// is about to replace the old cache slot. But if we	// release the lockfile and then try to open the new cache	// slot, we might get a race condition with a concurrent	// writer for the same cache slot (with a different key).	// Lets avoid such a race by just printing the content of	// the lock file.	slot->cache_fd = slot->lock_fd;	unlock_slot(slot, 1);	if ((err = print_slot(slot)) != 0) {		cache_log("[cgit] error printing cache %s: %s (%d)\n",			  slot->cache_name,			  strerror(err),			  err);	}	close_slot(slot);	return err;} /* Print cached content to stdout, generate the content if necessary. */int cache_process(int size, const char *path, const char *key, int ttl,		  cache_fill_fn fn){	unsigned long hash;	int i;	struct strbuf filename = STRBUF_INIT;	struct strbuf lockname = STRBUF_INIT;	struct cache_slot slot;	int result; 	/* If the cache is disabled, just generate the content */	if (size <= 0 || ttl == 0) {		fn();		return 0;	} 	/* Verify input, calculate filenames */	if (!path) {		cache_log("[cgit] Cache path not specified, caching is disabled\n");		fn();		return 0;	}	if (!key)		key = "";	hash = hash_str(key) % size;	strbuf_addstr(&filename, path);	strbuf_ensure_end(&filename, '/');	for (i = 0; i < 8; i++) {		strbuf_addf(&filename, "%x", (unsigned char)(hash & 0xf));		hash >>= 4;	}	strbuf_addbuf(&lockname, &filename);	strbuf_addstr(&lockname, ".lock");	slot.fn = fn;	slot.ttl = ttl;	slot.stdout_fd = -1;	slot.cache_name = filename.buf;	slot.lock_name = lockname.buf;	slot.key = key;	slot.keylen = strlen(key);	result = process_slot(&slot); 	strbuf_release(&filename);	strbuf_release(&lockname);	return result;} /* Return a strftime formatted date/time * NB: the result from this function is to shared memory */static char *sprintftime(const char *format, time_t time){	static char buf[64];	struct tm tm; 	if (!time)		return NULL;	gmtime_r(&time, &tm);	strftime(buf, sizeof(buf)-1, format, &tm);	return buf;} int cache_ls(const char *path){	DIR *dir;	struct dirent *ent;	int err = 0;	struct cache_slot slot = { NULL };	struct strbuf fullname = STRBUF_INIT;	size_t prefixlen; 	if (!path) {		cache_log("[cgit] cache path not specified\n");		return -1;	}	dir = opendir(path);	if (!dir) {		err = errno;		cache_log("[cgit] unable to open path %s: %s (%d)\n",			  path, strerror(err), err);		return err;	}	strbuf_addstr(&fullname, path);	strbuf_ensure_end(&fullname, '/');	prefixlen = fullname.len;	while ((ent = readdir(dir)) != NULL) {		if (strlen(ent->d_name) != 8)			continue;		strbuf_setlen(&fullname, prefixlen);		strbuf_addstr(&fullname, ent->d_name);		slot.cache_name = fullname.buf;		if ((err = open_slot(&slot)) != 0) {			cache_log("[cgit] unable to open path %s: %s (%d)\n",				  fullname.buf, strerror(err), err);			continue;		}		htmlf("%s %s %10"PRIuMAX" %s\n",		      fullname.buf,		      sprintftime("%Y-%m-%d %H:%M:%S",				  slot.cache_st.st_mtime),		      (uintmax_t)slot.cache_st.st_size,		      slot.buf);		close_slot(&slot);	}	closedir(dir);	strbuf_release(&fullname);	return 0;} /* Print a message to stdout */void cache_log(const char *format, ...){	va_list args;	va_start(args, format);	vfprintf(stderr, format, args);	va_end(args);}