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Date:: Fri Jan 29 17:11:03 2021 UTC
Message:: puny_decode: set an error string
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1 /*
2  * Copyright (c) 2021 Omar Polo <op@omarpolo.com>
3  *
4  * Permission to use, copy, modify, and distribute this software for any
5  * purpose with or without fee is hereby granted, provided that the above
6  * copyright notice and this permission notice appear in all copies.
7  *
8  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15  */
16 
17 #include <sys/mman.h>
18 #include <sys/stat.h>
19 
20 #include <netdb.h>
21 
22 #include <assert.h>
23 #include <errno.h>
24 #include <fcntl.h>
25 #include <fnmatch.h>
26 #include <string.h>
27 
28 #include "gmid.h"
29 
30 int connected_clients;
31 
32 const char *
33 vhost_lang(struct vhost *v, const char *path)
34 {
35 	struct location *loc;
36 	const char *lang = NULL;
37 
38 	if (v == NULL || path == NULL)
39 		return lang;
40 
41 	for (loc = v->locations; loc->match != NULL; ++loc) {
42 		if (!fnmatch(loc->match, path, 0)) {
43 			if (loc->lang != NULL)
44 				lang = loc->lang;
45 		}
46 	}
47 
48 	return lang;
49 }
50 
51 const char *
52 vhost_default_mime(struct vhost *v, const char *path)
53 {
54 	struct location *loc;
55 	const char *default_mime = "application/octet-stream";
56 
57 	if (v == NULL || path == NULL)
58 		return default_mime;
59 
60 	for (loc = v->locations; loc->match != NULL; ++loc) {
61 		if (!fnmatch(loc->match, path, 0)) {
62 			if (loc->default_mime != NULL)
63 				default_mime = loc->default_mime;
64 		}
65 	}
66 
67 	return default_mime;
68 }
69 
70 const char *
71 vhost_index(struct vhost *v, const char *path)
72 {
73 	struct location *loc;
74 	const char *index = "index.gmi";
75 
76 	if (v == NULL || path == NULL)
77 		return index;
78 
79 	for (loc = v->locations; loc->match != NULL; ++loc) {
80 		if (!fnmatch(loc->match, path, 0)) {
81 			if (loc->index != NULL)
82 				index = loc->index;
83 		}
84 	}
85 
86 	return index;
87 }
88 
89 int
90 vhost_auto_index(struct vhost *v, const char *path)
91 {
92 	struct location *loc;
93 	int auto_index = 0;
94 
95 	for (loc = v->locations; loc->match != NULL; ++loc) {
96 		if (!fnmatch(loc->match, path, 0)) {
97 			if (loc->auto_index)
98 				auto_index = loc->auto_index;
99 		}
100 	}
101 
102 	return auto_index == 1;
103 }
104 
105 int
106 check_path(struct client *c, const char *path, int *fd)
107 {
108 	struct stat sb;
109 	const char *p;
110 	int flags;
111 
112 	assert(path != NULL);
113 
114 	if (*path == '\0')
115 		p = ".";
116 	else if (*path == '/')
117 		/* in send_dir we add an initial / (to be
118 		 * redirect-friendly), but here we want to skip it */
119 		p = path+1;
120 	else
121 		p = path;
122 
123 	flags = O_RDONLY | O_NOFOLLOW;
124 
125 	if (*fd == -1 && (*fd = openat(c->host->dirfd, p, flags)) == -1)
126 		return FILE_MISSING;
127 
128 	if (fstat(*fd, &sb) == -1) {
129 		LOGN(c, "failed stat for %s: %s", path, strerror(errno));
130 		return FILE_MISSING;
131 	}
132 
133 	if (S_ISDIR(sb.st_mode))
134 		return FILE_DIRECTORY;
135 
136 	if (sb.st_mode & S_IXUSR)
137 		return FILE_EXECUTABLE;
138 
139 	return FILE_EXISTS;
140 }
141 
142 void
143 open_file(struct pollfd *fds, struct client *c)
144 {
145 	switch (check_path(c, c->iri.path, &c->fd)) {
146 	case FILE_EXECUTABLE:
147 		if (starts_with(c->iri.path, c->host->cgi)) {
148 			start_cgi(c->iri.path, "", c->iri.query, fds, c);
149 			return;
150 		}
151 
152 		/* fallthrough */
153 
154 	case FILE_EXISTS:
155 		load_file(fds, c);
156 		return;
157 
158 	case FILE_DIRECTORY:
159 		open_dir(fds, c);
160 		return;
161 
162 	case FILE_MISSING:
163 		if (c->host->cgi != NULL && starts_with(c->iri.path, c->host->cgi)) {
164 			check_for_cgi(c->iri.path, c->iri.query, fds, c);
165 			return;
166 		}
167 		start_reply(fds, c, NOT_FOUND, "not found");
168 		return;
169 
170 	default:
171 		/* unreachable */
172 		abort();
173 	}
174 }
175 
176 void
177 load_file(struct pollfd *fds, struct client *c)
178 {
179 	if ((c->len = filesize(c->fd)) == -1) {
180 		LOGE(c, "failed to get file size for %s", c->iri.path);
181 		start_reply(fds, c, TEMP_FAILURE, "internal server error");
182 		return;
183 	}
184 
185 	if ((c->buf = mmap(NULL, c->len, PROT_READ, MAP_PRIVATE,
186 		    c->fd, 0)) == MAP_FAILED) {
187 		LOGW(c, "mmap: %s: %s", c->iri.path, strerror(errno));
188 		start_reply(fds, c, TEMP_FAILURE, "internal server error");
189 		return;
190 	}
191 	c->i = c->buf;
192 	c->next = S_SENDING_FILE;
193 	start_reply(fds, c, SUCCESS, mime(c->host, c->iri.path));
194 }
195 
196 /*
197  * the inverse of this algorithm, i.e. starting from the start of the
198  * path + strlen(cgi), and checking if each component, should be
199  * faster.  But it's tedious to write.  This does the opposite: starts
200  * from the end and strip one component at a time, until either an
201  * executable is found or we emptied the path.
202  */
203 void
204 check_for_cgi(char *path, char *query, struct pollfd *fds, struct client *c)
205 {
206 	char *end;
207 	end = strchr(path, '\0');
208 
209 	/* NB: assume CGI is enabled and path matches cgi */
210 
211 	while (end > path) {
212 		/* go up one level.  UNIX paths are simple and POSIX
213 		 * dirname, with its ambiguities on if the given path
214 		 * is changed or not, gives me headaches. */
215 		while (*end != '/')
216 			end--;
217 		*end = '\0';
218 
219 		switch (check_path(c, path, &c->fd)) {
220 		case FILE_EXECUTABLE:
221 			start_cgi(path, end+1, query, fds,c);
222 			return;
223 		case FILE_MISSING:
224 			break;
225 		default:
226 			goto err;
227 		}
228 
229 		*end = '/';
230 		end--;
231 	}
232 
233 err:
234 	start_reply(fds, c, NOT_FOUND, "not found");
235 	return;
236 }
237 
238 void
239 mark_nonblock(int fd)
240 {
241 	int flags;
242 
243 	if ((flags = fcntl(fd, F_GETFL)) == -1)
244 		fatal("fcntl(F_GETFL): %s", strerror(errno));
245 	if (fcntl(fd, F_SETFL, flags | O_NONBLOCK) == -1)
246 		fatal("fcntl(F_SETFL): %s", strerror(errno));
247 }
248 
249 void
250 handle_handshake(struct pollfd *fds, struct client *c)
251 {
252 	struct vhost *h;
253 	const char *servname;
254 
255 	switch (tls_handshake(c->ctx)) {
256 	case 0:  /* success */
257 	case -1: /* already handshaked */
258 		break;
259 	case TLS_WANT_POLLIN:
260 		fds->events = POLLIN;
261 		return;
262 	case TLS_WANT_POLLOUT:
263 		fds->events = POLLOUT;
264 		return;
265 	default:
266 		/* unreachable */
267 		abort();
268 	}
269 
270 	servname = tls_conn_servername(c->ctx);
271 	puny_decode(servname, c->domain, sizeof(c->domain));
272 
273 	for (h = hosts; h->domain != NULL; ++h) {
274 		if (!fnmatch(h->domain, c->domain, 0))
275 			break;
276 	}
277 
278 	/* LOGD(c, "handshake: SNI: \"%s\"; decoded: \"%s\"; matched: \"%s\"", */
279 	/*     servname != NULL ? servname : "(null)", */
280 	/*     c->domain, */
281 	/*     h->domain != NULL ? h->domain : "(null)"); */
282 
283 	if (h->domain != NULL) {
284 		c->state = S_OPEN;
285 		c->host = h;
286 		handle_open_conn(fds, c);
287 		return;
288 	}
289 
290 	if (servname != NULL)
291 		strncpy(c->req, servname, sizeof(c->req));
292 	else
293 		strncpy(c->req, "null", sizeof(c->req));
294 
295 	start_reply(fds, c, BAD_REQUEST, "Wrong host or missing SNI");
296 }
297 
298 void
299 handle_open_conn(struct pollfd *fds, struct client *c)
300 {
301 	const char *parse_err = "invalid request";
302 	char decoded[DOMAIN_NAME_LEN];
303 
304 	bzero(c->req, sizeof(c->req));
305 	bzero(&c->iri, sizeof(c->iri));
306 
307 	switch (tls_read(c->ctx, c->req, sizeof(c->req)-1)) {
308 	case -1:
309 		LOGE(c, "tls_read: %s", tls_error(c->ctx));
310 		close_conn(fds, c);
311 		return;
312 
313 	case TLS_WANT_POLLIN:
314 		fds->events = POLLIN;
315 		return;
316 
317 	case TLS_WANT_POLLOUT:
318 		fds->events = POLLOUT;
319 		return;
320 	}
321 
322 	if (!trim_req_iri(c->req, &parse_err)
323 	    || !parse_iri(c->req, &c->iri, &parse_err)
324 	    || !puny_decode(c->iri.host, decoded, sizeof(decoded), &parse_err)) {
325 		LOGI(c, "iri parse error: %s", parse_err);
326 		start_reply(fds, c, BAD_REQUEST, "invalid request");
327 		return;
328 	}
329 
330 	if (c->iri.port_no != conf.port
331 	    || strcmp(c->iri.schema, "gemini")
332 	    || strcmp(decoded, c->domain)) {
333 		start_reply(fds, c, PROXY_REFUSED, "won't proxy request");
334 		return;
335 	}
336 
337 	open_file(fds, c);
338 }
339 
340 void
341 start_reply(struct pollfd *pfd, struct client *c, int code, const char *meta)
342 {
343 	char buf[1030];		/* status + ' ' + max reply len + \r\n\0 */
344 	const char *lang;
345 	size_t len;
346 
347 	c->code = code;
348 	c->meta = meta;
349 	c->state = S_INITIALIZING;
350 
351 	lang = vhost_lang(c->host, c->iri.path);
352 
353 	snprintf(buf, sizeof(buf), "%d ", code);
354 	strlcat(buf, meta, sizeof(buf));
355 	if (!strcmp(meta, "text/gemini") && lang != NULL) {
356 		strlcat(buf, "; lang=", sizeof(buf));
357 		strlcat(buf, lang, sizeof(buf));
358 	}
359 
360 	len = strlcat(buf, "\r\n", sizeof(buf));
361 	assert(len < sizeof(buf));
362 
363 	switch (tls_write(c->ctx, buf, len)) {
364 	case -1:
365 		close_conn(pfd, c);
366 		return;
367 	case TLS_WANT_POLLIN:
368 		pfd->events = POLLIN;
369 		return;
370 	case TLS_WANT_POLLOUT:
371 		pfd->events = POLLOUT;
372 		return;
373 	}
374 
375 	log_request(c, buf, sizeof(buf));
376 
377 	/* we don't need a body */
378 	if (c->code != SUCCESS) {
379 		close_conn(pfd, c);
380 		return;
381 	}
382 
383 	/* advance the state machine */
384 	c->state = c->next;
385 	handle(pfd, c);
386 }
387 
388 void
389 start_cgi(const char *spath, const char *relpath, const char *query,
390     struct pollfd *fds, struct client *c)
391 {
392 	char addr[NI_MAXHOST];
393 	const char *ruser, *cissuer, *chash;
394 	int e;
395 
396 	e = getnameinfo((struct sockaddr*)&c->addr, sizeof(c->addr),
397 	    addr, sizeof(addr),
398 	    NULL, 0,
399 	    NI_NUMERICHOST);
400 	if (e != 0)
401 		goto err;
402 
403 	if (tls_peer_cert_provided(c->ctx)) {
404 		ruser = tls_peer_cert_subject(c->ctx);
405 		cissuer = tls_peer_cert_issuer(c->ctx);
406 		chash = tls_peer_cert_hash(c->ctx);
407 	} else {
408 		ruser = NULL;
409 		cissuer = NULL;
410 		chash = NULL;
411 	}
412 
413 	if (!send_string(exfd, spath)
414 	    || !send_string(exfd, relpath)
415 	    || !send_string(exfd, query)
416 	    || !send_string(exfd, addr)
417 	    || !send_string(exfd, ruser)
418 	    || !send_string(exfd, cissuer)
419 	    || !send_string(exfd, chash)
420 	    || !send_vhost(exfd, c->host))
421 		goto err;
422 
423 	close(c->fd);
424 	if ((c->fd = recv_fd(exfd)) == -1) {
425 		start_reply(fds, c, TEMP_FAILURE, "internal server error");
426 		return;
427 	}
428 	c->state = S_SENDING_CGI;
429 	cgi_poll_on_child(fds, c);
430 	c->code = -1;
431 	/* handle_cgi(fds, c); */
432 	return;
433 
434 err:
435 	/* fatal("cannot talk to the executor process: %s", strerror(errno)); */
436 	fatal("cannot talk to the executor process");
437 }
438 
439 void
440 send_file(struct pollfd *fds, struct client *c)
441 {
442 	ssize_t ret, len;
443 
444 	/* ensure the correct state */
445 	c->state = S_SENDING_FILE;
446 
447 	len = (c->buf + c->len) - c->i;
448 
449 	while (len > 0) {
450 		switch (ret = tls_write(c->ctx, c->i, len)) {
451 		case -1:
452 			LOGE(c, "tls_write: %s", tls_error(c->ctx));
453 			close_conn(fds, c);
454 			return;
455 
456 		case TLS_WANT_POLLIN:
457 			fds->events = POLLIN;
458 			return;
459 
460 		case TLS_WANT_POLLOUT:
461 			fds->events = POLLOUT;
462 			return;
463 
464 		default:
465 			c->i += ret;
466 			len -= ret;
467 			break;
468 		}
469 	}
470 
471 	close_conn(fds, c);
472 }
473 
474 void
475 open_dir(struct pollfd *fds, struct client *c)
476 {
477 	size_t len;
478 	int dirfd;
479 	char *before_file;
480 
481 	len = strlen(c->iri.path);
482 	if (len > 0 && !ends_with(c->iri.path, "/")) {
483 		redirect_canonical_dir(fds, c);
484 		return;
485 	}
486 
487 	strlcpy(c->sbuf, "/", sizeof(c->sbuf));
488 	strlcat(c->sbuf, c->iri.path, sizeof(c->sbuf));
489 	if (!ends_with(c->sbuf, "/"))
490 		strlcat(c->sbuf, "/", sizeof(c->sbuf));
491 	before_file = strchr(c->sbuf, '\0');
492 	len = strlcat(c->sbuf, vhost_index(c->host, c->iri.path),
493 	    sizeof(c->sbuf));
494 	if (len >= sizeof(c->sbuf)) {
495 		start_reply(fds, c, TEMP_FAILURE, "internal server error");
496 		return;
497 	}
498 
499 	c->iri.path = c->sbuf;
500 
501 	/* close later unless we have to generate the dir listing */
502 	dirfd = c->fd;
503 	c->fd = -1;
504 
505 	switch (check_path(c, c->iri.path, &c->fd)) {
506 	case FILE_EXECUTABLE:
507 		if (starts_with(c->iri.path, c->host->cgi)) {
508 			start_cgi(c->iri.path, "", c->iri.query, fds, c);
509 			break;
510 		}
511 
512 		/* fallthrough */
513 
514 	case FILE_EXISTS:
515                 load_file(fds, c);
516 		break;
517 
518 	case FILE_DIRECTORY:
519 		start_reply(fds, c, TEMP_REDIRECT, c->sbuf);
520 		break;
521 
522 	case FILE_MISSING:
523 		*before_file = '\0';
524 
525 		if (!vhost_auto_index(c->host, c->iri.path)) {
526 			start_reply(fds, c, NOT_FOUND, "not found");
527 			break;
528 		}
529 
530 		c->fd = dirfd;
531 		c->next = S_SENDING_DIR;
532 
533 		if ((c->dir = fdopendir(c->fd)) == NULL) {
534 			LOGE(c, "can't fdopendir(%d) (vhost:%s) %s: %s",
535 			    c->fd, c->host->domain, c->iri.path, strerror(errno));
536 			start_reply(fds, c, TEMP_FAILURE, "internal server error");
537 			return;
538 		}
539 		c->off = 0;
540 
541                 start_reply(fds, c, SUCCESS, "text/gemini");
542 		return;
543 
544 	default:
545 		/* unreachable */
546 		abort();
547 	}
548 
549 	close(dirfd);
550 }
551 
552 void
553 redirect_canonical_dir(struct pollfd *fds, struct client *c)
554 {
555 	size_t len;
556 
557 	strlcpy(c->sbuf, "/", sizeof(c->sbuf));
558 	strlcat(c->sbuf, c->iri.path, sizeof(c->sbuf));
559 	len = strlcat(c->sbuf, "/", sizeof(c->sbuf));
560 
561 	if (len >= sizeof(c->sbuf)) {
562 		start_reply(fds, c, TEMP_FAILURE, "internal server error");
563 		return;
564 	}
565 
566 	start_reply(fds, c, TEMP_REDIRECT, c->sbuf);
567 }
568 
569 int
570 read_next_dir_entry(struct client *c)
571 {
572 	struct dirent *d;
573 
574 	do {
575 		errno = 0;
576 		if ((d = readdir(c->dir)) == NULL) {
577 			if (errno != 0)
578 				LOGE(c, "readdir: %s", strerror(errno));
579 			return 0;
580 		}
581 	} while (!strcmp(d->d_name, "."));
582 
583 	/* XXX: url escape */
584 	snprintf(c->sbuf, sizeof(c->sbuf), "=> %s %s\n",
585 	    d->d_name, d->d_name);
586 	c->len = strlen(c->sbuf);
587 	c->off = 0;
588 
589 	return 1;
590 }
591 
592 void
593 send_directory_listing(struct pollfd *fds, struct client *c)
594 {
595 	ssize_t r;
596 
597 	while (1) {
598 		if (c->len == 0) {
599 			if (!read_next_dir_entry(c))
600 				goto end;
601 		}
602 
603 		while (c->len > 0) {
604 			switch (r = tls_write(c->ctx, c->sbuf + c->off, c->len)) {
605 			case -1:
606 				goto end;
607 
608 			case TLS_WANT_POLLOUT:
609 				fds->events = POLLOUT;
610 				return;
611 
612 			case TLS_WANT_POLLIN:
613 				fds->events = POLLIN;
614 				return;
615 
616 			default:
617 				c->off += r;
618 				c->len -= r;
619 				break;
620 			}
621 		}
622 	}
623 
624 end:
625 	close_conn(fds, c);
626 }
627 
628 void
629 cgi_poll_on_child(struct pollfd *fds, struct client *c)
630 {
631 	int fd;
632 
633 	if (c->waiting_on_child)
634 		return;
635 	c->waiting_on_child = 1;
636 
637 	fds->events = POLLIN;
638 
639 	fd = fds->fd;
640 	fds->fd = c->fd;
641 	c->fd = fd;
642 }
643 
644 void
645 cgi_poll_on_client(struct pollfd *fds, struct client *c)
646 {
647 	int fd;
648 
649 	if (!c->waiting_on_child)
650 		return;
651 	c->waiting_on_child = 0;
652 
653 	fd = fds->fd;
654 	fds->fd = c->fd;
655 	c->fd = fd;
656 }
657 
658 /* handle the read from the child process.  Return like read(2) */
659 static ssize_t
660 read_from_cgi(struct client *c)
661 {
662 	void	*buf;
663 	size_t	 len;
664 	ssize_t	 r;
665 
666 	/* if we haven't read a whole response line, we want to
667 	 * continue reading. */
668 
669 	if (c->code == -1) {
670 		buf = c->sbuf + c->len;
671 		len = sizeof(c->sbuf) - c->len;
672 	} else {
673 		buf = c->sbuf;
674 		len = sizeof(c->sbuf);
675 	}
676 
677 	r = read(c->fd, buf, len);
678 	if (r == 0 || r == -1)
679 		return r;
680 
681 	c->len += r;
682 	c->off = 0;
683 
684 	if (c->code != -1)
685 		return r;
686 
687 	if (strchr(c->sbuf, '\n') || c->len == sizeof(c->sbuf)) {
688 		c->code = 0;
689 		log_request(c, c->sbuf, c->len);
690 	}
691 
692 	return r;
693 }
694 
695 void
696 handle_cgi(struct pollfd *fds, struct client *c)
697 {
698 	ssize_t r;
699 
700 	/* ensure c->fd is the child and fds->fd the client */
701 	cgi_poll_on_client(fds, c);
702 
703 	while (1) {
704 		if (c->code == -1 || c->len == 0) {
705 			switch (r = read_from_cgi(c)) {
706 			case 0:
707 				goto end;
708 
709 			case -1:
710 				if (errno == EAGAIN || errno == EWOULDBLOCK) {
711 					cgi_poll_on_child(fds, c);
712 					return;
713 				}
714 				goto end;
715 			}
716 		}
717 
718 		if (c->code == -1) {
719 			cgi_poll_on_child(fds, c);
720 			return;
721 		}
722 
723 		while (c->len > 0) {
724 			switch (r = tls_write(c->ctx, c->sbuf + c->off, c->len)) {
725 			case -1:
726 				goto end;
727 
728 			case TLS_WANT_POLLOUT:
729 				fds->events = POLLOUT;
730 				return;
731 
732 			case TLS_WANT_POLLIN:
733 				fds->events = POLLIN;
734 				return;
735 
736 			default:
737                                 c->off += r;
738 				c->len -= r;
739 				break;
740 			}
741 		}
742 	}
743 
744 end:
745 	close_conn(fds, c);
746 }
747 
748 void
749 close_conn(struct pollfd *pfd, struct client *c)
750 {
751 	c->state = S_CLOSING;
752 
753 	switch (tls_close(c->ctx)) {
754 	case TLS_WANT_POLLIN:
755 		pfd->events = POLLIN;
756 		return;
757 	case TLS_WANT_POLLOUT:
758 		pfd->events = POLLOUT;
759 		return;
760 	}
761 
762 	connected_clients--;
763 
764 	tls_free(c->ctx);
765 	c->ctx = NULL;
766 
767 	if (c->buf != MAP_FAILED)
768 		munmap(c->buf, c->len);
769 
770 	if (c->fd != -1)
771 		close(c->fd);
772 
773 	if (c->dir != NULL)
774 		closedir(c->dir);
775 
776 	close(pfd->fd);
777 	pfd->fd = -1;
778 }
779 
780 void
781 do_accept(int sock, struct tls *ctx, struct pollfd *fds, struct client *clients)
782 {
783 	int i, fd;
784 	struct sockaddr_storage addr;
785 	socklen_t len;
786 
787 	len = sizeof(addr);
788 	if ((fd = accept(sock, (struct sockaddr*)&addr, &len)) == -1) {
789 		if (errno == EWOULDBLOCK)
790 			return;
791 		fatal("accept: %s", strerror(errno));
792 	}
793 
794 	mark_nonblock(fd);
795 
796 	for (i = 0; i < MAX_USERS; ++i) {
797 		if (fds[i].fd == -1) {
798 			bzero(&clients[i], sizeof(struct client));
799 			if (tls_accept_socket(ctx, &clients[i].ctx, fd) == -1)
800 				break; /* goodbye fd! */
801 
802 			fds[i].fd = fd;
803 			fds[i].events = POLLIN;
804 
805 			clients[i].state = S_HANDSHAKE;
806 			clients[i].next = S_SENDING_FILE;
807 			clients[i].fd = -1;
808 			clients[i].waiting_on_child = 0;
809 			clients[i].buf = MAP_FAILED;
810 			clients[i].dir = NULL;
811 			clients[i].addr = addr;
812 
813 			connected_clients++;
814 			return;
815 		}
816 	}
817 
818 	close(fd);
819 }
820 
821 void
822 handle(struct pollfd *fds, struct client *client)
823 {
824 	switch (client->state) {
825 	case S_HANDSHAKE:
826 		handle_handshake(fds, client);
827 		break;
828 
829 	case S_OPEN:
830                 handle_open_conn(fds, client);
831 		break;
832 
833 	case S_INITIALIZING:
834 		start_reply(fds, client, client->code, client->meta);
835                 break;
836 
837 	case S_SENDING_FILE:
838 		send_file(fds, client);
839 		break;
840 
841 	case S_SENDING_DIR:
842 		send_directory_listing(fds, client);
843 		break;
844 
845 	case S_SENDING_CGI:
846 		handle_cgi(fds, client);
847 		break;
848 
849 	case S_CLOSING:
850 		close_conn(fds, client);
851 		break;
852 
853 	default:
854 		/* unreachable */
855 		abort();
856 	}
857 }
858 
859 void
860 loop(struct tls *ctx, int sock4, int sock6)
861 {
862 	int i;
863 	struct client clients[MAX_USERS];
864 	struct pollfd fds[MAX_USERS];
865 
866 	connected_clients = 0;
867 
868 	for (i = 0; i < MAX_USERS; ++i) {
869 		fds[i].fd = -1;
870 		fds[i].events = POLLIN;
871 		bzero(&clients[i], sizeof(struct client));
872 	}
873 
874 	fds[0].fd = sock4;
875 	fds[1].fd = sock6;
876 
877 	for (;;) {
878 		if (poll(fds, MAX_USERS, INFTIM) == -1) {
879 			if (errno == EINTR) {
880                                 fprintf(stderr, "connected clients: %d\n",
881 				    connected_clients);
882 				continue;
883 			}
884 			fatal("poll: %s", strerror(errno));
885 		}
886 
887 		for (i = 0; i < MAX_USERS; i++) {
888 			if (fds[i].revents == 0)
889 				continue;
890 
891 			if (fds[i].revents & (POLLERR|POLLNVAL))
892 				fatal("bad fd %d: %s", fds[i].fd,
893 				    strerror(errno));
894 
895 			if (fds[i].revents & POLLHUP) {
896 				/* fds[i] may be the fd of the stdin
897 				 * of a cgi script that has exited. */
898 				if (!clients[i].waiting_on_child) {
899 					close_conn(&fds[i], &clients[i]);
900 					continue;
901 				}
902 			}
903 
904 			if (fds[i].fd == sock4)
905 				do_accept(sock4, ctx, fds, clients);
906 			else if (fds[i].fd == sock6)
907 				do_accept(sock6, ctx, fds, clients);
908 			else
909 				handle(&fds[i], &clients[i]);
910 		}
911 	}
912 }