Make recv_pattern() use the nonblock API.
[paraslash.git] / fd.c
1 /*
2 * Copyright (C) 2006-2010 Andre Noll <maan@systemlinux.org>
3 *
4 * Licensed under the GPL v2. For licencing details see COPYING.
5 */
6
7 /** \file fd.c Helper functions for file descriptor handling. */
8
9 #include <regex.h>
10 #include <sys/types.h>
11 #include <dirent.h>
12 #include <sys/mman.h>
13 #include <fcntl.h>
14 #include <sys/uio.h>
15
16 #include "para.h"
17 #include "error.h"
18 #include "string.h"
19 #include "fd.h"
20
21 /**
22 * Write a buffer to a file descriptor, re-write on short writes.
23 *
24 * \param fd The file descriptor.
25 * \param buf The buffer to be sent.
26 * \param len The length of \a buf.
27 *
28 * \return Standard. In any case, the number of bytes that have been written is
29 * stored in \a len.
30 */
31 int write_all(int fd, const char *buf, size_t *len)
32 {
33 size_t total = *len;
34
35 assert(total);
36 *len = 0;
37 while (*len < total) {
38 int ret = write(fd, buf + *len, total - *len);
39 if (ret == -1)
40 return -ERRNO_TO_PARA_ERROR(errno);
41 *len += ret;
42 }
43 return 1;
44 }
45
46 /**
47 * Write a buffer to a non-blocking file descriptor.
48 *
49 * \param fd The file descriptor.
50 * \param buf the buffer to write.
51 * \param len the number of bytes of \a buf.
52 * \param max_bytes_per_write Do not write more than that many bytes at once.
53 *
54 * If \a max_bytes_per_write is non-zero, do not send more than that many bytes
55 * per write().
56 *
57 * EAGAIN is not considered an error condition. For example CCID3 has a
58 * sending wait queue which fills up and is emptied asynchronously. The EAGAIN
59 * case means that there is currently no space in the wait queue, but this can
60 * change at any moment.
61 *
62 * \return Negative on errors, number of bytes written else.
63 */
64 int write_nonblock(int fd, const char *buf, size_t len,
65 size_t max_bytes_per_write)
66 {
67 size_t written = 0;
68 int ret = 0;
69
70 while (written < len) {
71 size_t num = len - written;
72
73 if (max_bytes_per_write && max_bytes_per_write < num)
74 num = max_bytes_per_write;
75 ret = write(fd, buf + written, num);
76 if (ret < 0 && errno == EAGAIN)
77 return written;
78 if (ret < 0)
79 return -ERRNO_TO_PARA_ERROR(errno);
80 written += ret;
81 }
82 return written;
83 }
84
85 /**
86 * Read from a non-blocking file descriptor into multiple buffers.
87 *
88 * \param fd The file descriptor to read from.
89 * \param iov Scatter/gather array used in readv().
90 * \param iovcnt Number of elements in \a iov.
91 * \param rfds An optional fd set pointer.
92 * \param num_bytes Result pointer. Contains the number of bytes read from \a fd.
93 *
94 * If \a rfds is not \p NULL and the (non-blocking) file descriptor \a fd is
95 * not set in \a rfds, this function returns early without doing anything.
96 * Otherwise The function tries to read up to \a sz bytes from \a fd. As for
97 * write_nonblock(), EAGAIN is not considered an error condition. However, EOF
98 * is.
99 *
100 * \return Zero or a negative error code. If the underlying call to readv(2)
101 * returned zero (indicating an end of file condition) or failed for some
102 * reason other than \p EAGAIN, a negative return value is returned.
103 *
104 * In any case, \a num_bytes contains the number of bytes that have been
105 * successfully read from \a fd (zero if the first readv() call failed with
106 * EAGAIN). Note that even if the function returns negative, some data might
107 * have been read before the error occured. In this case \a num_bytes is
108 * positive.
109 *
110 * \sa \ref write_nonblock(), read(2), readv(2).
111 */
112 int readv_nonblock(int fd, struct iovec *iov, int iovcnt, fd_set *rfds,
113 size_t *num_bytes)
114 {
115 int ret, i, j;
116
117 *num_bytes = 0;
118 /*
119 * Avoid a shortcoming of select(): Reads from a non-blocking fd might
120 * return EAGAIN even if FD_ISSET() returns true. However, FD_ISSET()
121 * returning false definitely means that no data can currently be read.
122 * This is the common case, so it is worth to avoid the overhead of the
123 * read() system call in this case.
124 */
125 if (rfds && !FD_ISSET(fd, rfds))
126 return 0;
127
128 for (i = 0, j = 0; i < iovcnt;) {
129
130 /* fix up the first iov */
131 assert(j < iov[i].iov_len);
132 iov[i].iov_base += j;
133 iov[i].iov_len -= j;
134 ret = readv(fd, iov + i, iovcnt - i);
135 iov[i].iov_base -= j;
136 iov[i].iov_len += j;
137
138 if (ret == 0)
139 return -E_EOF;
140 if (ret < 0) {
141 if (errno == EAGAIN)
142 return 0;
143 return -ERRNO_TO_PARA_ERROR(errno);
144 }
145 *num_bytes += ret;
146 while (ret > 0) {
147 if (ret < iov[i].iov_len - j) {
148 j += ret;
149 break;
150 }
151 ret -= iov[i].iov_len - j;
152 j = 0;
153 if (++i >= iovcnt)
154 break;
155 }
156 }
157 return 0;
158 }
159
160 /**
161 * Read from a non-blocking file descriptor into a single buffer.
162 *
163 * \param fd The file descriptor to read from.
164 * \param buf The buffer to read data to.
165 * \param sz The size of \a buf.
166 * \param rfds \see \ref readv_nonblock().
167 * \param num_bytes \see \ref readv_nonblock().
168 *
169 * This is a simple wrapper for readv_nonblock() which uses an iovec with a single
170 * buffer.
171 *
172 * \return The return value of the underlying call to readv_nonblock().
173 */
174 int read_nonblock(int fd, void *buf, size_t sz, fd_set *rfds, size_t *num_bytes)
175 {
176 struct iovec iov = {.iov_base = buf, .iov_len = sz};
177 return readv_nonblock(fd, &iov, 1, rfds, num_bytes);
178 }
179
180 /**
181 * Read a buffer and check its content for a pattern.
182 *
183 * \param fd The file descriptor to receive from.
184 * \param pattern The expected pattern.
185 * \param bufsize The size of the internal buffer.
186 *
187 * This function tries to read at most \a bufsize bytes from the non-blocking
188 * file descriptor \a fd. If at least \p strlen(\a pattern) bytes have been
189 * received, the beginning of the received buffer is compared with \a pattern,
190 * ignoring case.
191 *
192 * \return Positive if \a pattern was received, negative on errors, zero if no data
193 * was available to read.
194 *
195 * \sa \ref read_nonblock(), \sa strncasecmp(3).
196 */
197 int read_pattern(int fd, const char *pattern, size_t bufsize, fd_set *rfds)
198 {
199 size_t n, len;
200 char *buf = para_malloc(bufsize + 1);
201 int ret = read_nonblock(fd, buf, bufsize, rfds, &n);
202
203 buf[n] = '\0';
204 if (ret < 0)
205 goto out;
206 ret = 0;
207 if (n == 0)
208 goto out;
209 ret = -E_READ_PATTERN;
210 len = strlen(pattern);
211 if (n < len)
212 goto out;
213 if (strncasecmp(buf, pattern, len) != 0)
214 goto out;
215 ret = 1;
216 out:
217 if (ret < 0) {
218 PARA_NOTICE_LOG("%s\n", para_strerror(-ret));
219 PARA_NOTICE_LOG("recvd %zu bytes: %s\n", n, buf);
220 }
221 free(buf);
222 return ret;
223 }
224
225 /**
226 * Check whether a file exists.
227 *
228 * \param fn The file name.
229 *
230 * \return Non-zero iff file exists.
231 */
232 int file_exists(const char *fn)
233 {
234 struct stat statbuf;
235
236 return !stat(fn, &statbuf);
237 }
238
239 /**
240 * Paraslash's wrapper for select(2).
241 *
242 * It calls select(2) (with no exceptfds) and starts over if select() was
243 * interrupted by a signal.
244 *
245 * \param n The highest-numbered descriptor in any of the two sets, plus 1.
246 * \param readfds fds that should be checked for readability.
247 * \param writefds fds that should be checked for writablility.
248 * \param timeout_tv upper bound on the amount of time elapsed before select()
249 * returns.
250 *
251 * \return The return value of the underlying select() call on success, the
252 * negative system error code on errors.
253 *
254 * All arguments are passed verbatim to select(2).
255 * \sa select(2) select_tut(2).
256 */
257 int para_select(int n, fd_set *readfds, fd_set *writefds,
258 struct timeval *timeout_tv)
259 {
260 int ret;
261 do
262 ret = select(n, readfds, writefds, NULL, timeout_tv);
263 while (ret < 0 && errno == EINTR);
264 if (ret < 0)
265 return -ERRNO_TO_PARA_ERROR(errno);
266 return ret;
267 }
268
269 /**
270 * Set a file descriptor to blocking mode.
271 *
272 * \param fd The file descriptor.
273 *
274 * \return Standard.
275 */
276 __must_check int mark_fd_blocking(int fd)
277 {
278 int flags = fcntl(fd, F_GETFL);
279 if (flags < 0)
280 return -ERRNO_TO_PARA_ERROR(errno);
281 flags = fcntl(fd, F_SETFL, ((long)flags) & ~O_NONBLOCK);
282 if (flags < 0)
283 return -ERRNO_TO_PARA_ERROR(errno);
284 return 1;
285 }
286
287 /**
288 * Set a file descriptor to non-blocking mode.
289 *
290 * \param fd The file descriptor.
291 *
292 * \return Standard.
293 */
294 __must_check int mark_fd_nonblocking(int fd)
295 {
296 int flags = fcntl(fd, F_GETFL);
297 if (flags < 0)
298 return -ERRNO_TO_PARA_ERROR(errno);
299 flags = fcntl(fd, F_SETFL, ((long)flags) | O_NONBLOCK);
300 if (flags < 0)
301 return -ERRNO_TO_PARA_ERROR(errno);
302 return 1;
303 }
304
305 /**
306 * Set a file descriptor in a fd_set.
307 *
308 * \param fd The file descriptor to be set.
309 * \param fds The file descriptor set.
310 * \param max_fileno Highest-numbered file descriptor.
311 *
312 * This wrapper for FD_SET() passes its first two arguments to \p FD_SET. Upon
313 * return, \a max_fileno contains the maximum of the old_value and \a fd.
314 *
315 * \sa para_select.
316 */
317 void para_fd_set(int fd, fd_set *fds, int *max_fileno)
318 {
319 assert(fd >= 0 && fd < FD_SETSIZE);
320 #if 0
321 {
322 int flags = fcntl(fd, F_GETFL);
323 if (!(flags & O_NONBLOCK)) {
324 PARA_EMERG_LOG("fd %d is a blocking file descriptor\n", fd);
325 exit(EXIT_FAILURE);
326 }
327 }
328 #endif
329 FD_SET(fd, fds);
330 *max_fileno = PARA_MAX(*max_fileno, fd);
331 }
332
333 /**
334 * Paraslash's wrapper for fgets(3).
335 *
336 * \param line Pointer to the buffer to store the line.
337 * \param size The size of the buffer given by \a line.
338 * \param f The stream to read from.
339 *
340 * \return Unlike the standard fgets() function, an integer value
341 * is returned. On success, this function returns 1. On errors, -E_FGETS
342 * is returned. A zero return value indicates an end of file condition.
343 */
344 __must_check int para_fgets(char *line, int size, FILE *f)
345 {
346 again:
347 if (fgets(line, size, f))
348 return 1;
349 if (feof(f))
350 return 0;
351 if (!ferror(f))
352 return -E_FGETS;
353 if (errno != EINTR) {
354 PARA_ERROR_LOG("%s\n", strerror(errno));
355 return -E_FGETS;
356 }
357 clearerr(f);
358 goto again;
359 }
360
361 /**
362 * Paraslash's wrapper for mmap.
363 *
364 * \param length Number of bytes to mmap.
365 * \param prot Either PROT_NONE or the bitwise OR of one or more of
366 * PROT_EXEC PROT_READ PROT_WRITE.
367 * \param flags Exactly one of MAP_SHARED and MAP_PRIVATE.
368 * \param fd The file to mmap from.
369 * \param offset Mmap start.
370 * \param map Result pointer.
371 *
372 * \return Standard.
373 *
374 * \sa mmap(2).
375 */
376 int para_mmap(size_t length, int prot, int flags, int fd, off_t offset,
377 void *map)
378 {
379 void **m = map;
380
381 errno = EINVAL;
382 if (!length)
383 goto err;
384 *m = mmap(NULL, length, prot, flags, fd, offset);
385 if (*m != MAP_FAILED)
386 return 1;
387 err:
388 *m = NULL;
389 return -ERRNO_TO_PARA_ERROR(errno);
390 }
391
392 /**
393 * Wrapper for the open(2) system call.
394 *
395 * \param path The filename.
396 * \param flags The usual open(2) flags.
397 * \param mode Specifies the permissions to use.
398 *
399 * The mode parameter must be specified when O_CREAT is in the flags, and is
400 * ignored otherwise.
401 *
402 * \return The file descriptor on success, negative on errors.
403 *
404 * \sa open(2).
405 */
406 int para_open(const char *path, int flags, mode_t mode)
407 {
408 int ret = open(path, flags, mode);
409
410 if (ret >= 0)
411 return ret;
412 return -ERRNO_TO_PARA_ERROR(errno);
413 }
414
415 /**
416 * Wrapper for chdir(2).
417 *
418 * \param path The specified directory.
419 *
420 * \return Standard.
421 */
422 int para_chdir(const char *path)
423 {
424 int ret = chdir(path);
425
426 if (ret >= 0)
427 return 1;
428 return -ERRNO_TO_PARA_ERROR(errno);
429 }
430
431 /**
432 * Save the cwd and open a given directory.
433 *
434 * \param dirname Path to the directory to open.
435 * \param dir Result pointer.
436 * \param cwd File descriptor of the current working directory.
437 *
438 * \return Standard.
439 *
440 * Opening the current directory (".") and calling fchdir() to return is
441 * usually faster and more reliable than saving cwd in some buffer and calling
442 * chdir() afterwards.
443 *
444 * If \a cwd is not \p NULL "." is opened and the resulting file descriptor is
445 * stored in \a cwd. If the function returns success, and \a cwd is not \p
446 * NULL, the caller must close this file descriptor (probably after calling
447 * fchdir(*cwd)).
448 *
449 * On errors, the function undos everything, so the caller needs neither close
450 * any files, nor change back to the original working directory.
451 *
452 * \sa getcwd(3).
453 *
454 */
455 int para_opendir(const char *dirname, DIR **dir, int *cwd)
456 {
457 int ret;
458
459 if (cwd) {
460 ret = para_open(".", O_RDONLY, 0);
461 if (ret < 0)
462 return ret;
463 *cwd = ret;
464 }
465 ret = para_chdir(dirname);
466 if (ret < 0)
467 goto close_cwd;
468 *dir = opendir(".");
469 if (*dir)
470 return 1;
471 ret = -ERRNO_TO_PARA_ERROR(errno);
472 /* Ignore return value of fchdir() and close(). We're busted anyway. */
473 if (cwd) {
474 int __a_unused ret2 = fchdir(*cwd); /* STFU, gcc */
475 }
476 close_cwd:
477 if (cwd)
478 close(*cwd);
479 return ret;
480 }
481
482 /**
483 * A wrapper for fchdir().
484 *
485 * \param fd An open file descriptor.
486 *
487 * \return Standard.
488 */
489 int para_fchdir(int fd)
490 {
491 if (fchdir(fd) < 0)
492 return -ERRNO_TO_PARA_ERROR(errno);
493 return 1;
494 }
495
496 /**
497 * A wrapper for mkdir(2).
498 *
499 * \param path Name of the directory to create.
500 * \param mode The permissions to use.
501 *
502 * \return Standard.
503 */
504 int para_mkdir(const char *path, mode_t mode)
505 {
506 if (!mkdir(path, mode))
507 return 1;
508 return -ERRNO_TO_PARA_ERROR(errno);
509 }
510
511 /**
512 * Open a file and map it into memory.
513 *
514 * \param path Name of the regular file to map.
515 * \param open_mode Either \p O_RDONLY or \p O_RDWR.
516 * \param map On success, the mapping is returned here.
517 * \param size size of the mapping.
518 * \param fd_ptr The file descriptor of the mapping.
519 *
520 * If \a fd_ptr is \p NULL, the file descriptor resulting from the underlying
521 * open call is closed after mmap(). Otherwise the file is kept open and the
522 * file descriptor is returned in \a fd_ptr.
523 *
524 * \return Standard.
525 *
526 * \sa para_open(), mmap(2).
527 */
528 int mmap_full_file(const char *path, int open_mode, void **map,
529 size_t *size, int *fd_ptr)
530 {
531 int fd, ret, mmap_prot, mmap_flags;
532 struct stat file_status;
533
534 if (open_mode == O_RDONLY) {
535 mmap_prot = PROT_READ;
536 mmap_flags = MAP_PRIVATE;
537 } else {
538 mmap_prot = PROT_READ | PROT_WRITE;
539 mmap_flags = MAP_SHARED;
540 }
541 ret = para_open(path, open_mode, 0);
542 if (ret < 0)
543 return ret;
544 fd = ret;
545 if (fstat(fd, &file_status) < 0) {
546 ret = -ERRNO_TO_PARA_ERROR(errno);
547 goto out;
548 }
549 *size = file_status.st_size;
550 ret = para_mmap(*size, mmap_prot, mmap_flags, fd, 0, map);
551 out:
552 if (ret < 0 || !fd_ptr)
553 close(fd);
554 else
555 *fd_ptr = fd;
556 return ret;
557 }
558
559 /**
560 * A wrapper for munmap(2).
561 *
562 * \param start The start address of the memory mapping.
563 * \param length The size of the mapping.
564 *
565 * \return Standard.
566 *
567 * \sa munmap(2), mmap_full_file().
568 */
569 int para_munmap(void *start, size_t length)
570 {
571 int err;
572 if (munmap(start, length) >= 0)
573 return 1;
574 err = errno;
575 PARA_ERROR_LOG("munmap (%p/%zu) failed: %s\n", start, length,
576 strerror(err));
577 return -ERRNO_TO_PARA_ERROR(err);
578 }
579
580 /**
581 * Check a file descriptor for writability.
582 *
583 * \param fd The file descriptor.
584 *
585 * \return positive if fd is ready for writing, zero if it isn't, negative if
586 * an error occurred.
587 */
588
589 int write_ok(int fd)
590 {
591 struct timeval tv;
592 fd_set wfds;
593
594 FD_ZERO(&wfds);
595 FD_SET(fd, &wfds);
596 tv.tv_sec = 0;
597 tv.tv_usec = 0;
598 return para_select(fd + 1, NULL, &wfds, &tv);
599 }
600
601 /**
602 * Ensure that file descriptors 0, 1, and 2 are valid.
603 *
604 * Common approach that opens /dev/null until it gets a file descriptor greater
605 * than two.
606 *
607 * \sa okir's Black Hats Manual.
608 */
609 void valid_fd_012(void)
610 {
611 while (1) {
612 int fd = open("/dev/null", O_RDWR);
613 if (fd < 0)
614 exit(EXIT_FAILURE);
615 if (fd > 2) {
616 close(fd);
617 break;
618 }
619 }
620 }
621
622 /**
623 * Traverse the given directory recursively.
624 *
625 * \param dirname The directory to traverse.
626 * \param func The function to call for each entry.
627 * \param private_data Pointer to an arbitrary data structure.
628 *
629 * For each regular file under \a dirname, the supplied function \a func is
630 * called. The full path of the regular file and the \a private_data pointer
631 * are passed to \a func. Directories for which the calling process has no
632 * permissions to change to are silently ignored.
633 *
634 * \return Standard.
635 */
636 int for_each_file_in_dir(const char *dirname,
637 int (*func)(const char *, void *), void *private_data)
638 {
639 DIR *dir;
640 struct dirent *entry;
641 int cwd_fd, ret2, ret = para_opendir(dirname, &dir, &cwd_fd);
642
643 if (ret < 0)
644 return ret == -ERRNO_TO_PARA_ERROR(EACCES)? 1 : ret;
645 /* scan cwd recursively */
646 while ((entry = readdir(dir))) {
647 mode_t m;
648 char *tmp;
649 struct stat s;
650
651 if (!strcmp(entry->d_name, "."))
652 continue;
653 if (!strcmp(entry->d_name, ".."))
654 continue;
655 if (lstat(entry->d_name, &s) == -1)
656 continue;
657 m = s.st_mode;
658 if (!S_ISREG(m) && !S_ISDIR(m))
659 continue;
660 tmp = make_message("%s/%s", dirname, entry->d_name);
661 if (!S_ISDIR(m)) {
662 ret = func(tmp, private_data);
663 free(tmp);
664 if (ret < 0)
665 goto out;
666 continue;
667 }
668 /* directory */
669 ret = for_each_file_in_dir(tmp, func, private_data);
670 free(tmp);
671 if (ret < 0)
672 goto out;
673 }
674 ret = 1;
675 out:
676 closedir(dir);
677 ret2 = para_fchdir(cwd_fd);
678 if (ret2 < 0 && ret >= 0)
679 ret = ret2;
680 close(cwd_fd);
681 return ret;
682 }