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Date:: Mon Feb 1 20:00:33 2021 UTC
Message:: client state machine: function pointers instead of enum+switch
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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 <limits.h>
27 #include <string.h>
28 
29 #include "gmid.h"
30 
31 int connected_clients;
32 
33 const char *
34 vhost_lang(struct vhost *v, const char *path)
35 {
36 	struct location *loc;
37 
38 	if (v == NULL || path == NULL)
39 		return NULL;
40 
41 	for (loc = &v->locations[1]; loc->match != NULL; ++loc) {
42 		if (!fnmatch(loc->match, path, 0)) {
43 			if (loc->lang != NULL)
44 				return loc->lang;
45 		}
46 	}
47 
48 	return v->locations[0].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[1]; loc->match != NULL; ++loc) {
61 		if (!fnmatch(loc->match, path, 0)) {
62 			if (loc->default_mime != NULL)
63 				return loc->default_mime;
64 		}
65 	}
66 
67 	if (v->locations[0].default_mime != NULL)
68 		return v->locations[0].default_mime;
69 	return default_mime;
70 }
71 
72 const char *
73 vhost_index(struct vhost *v, const char *path)
74 {
75 	struct location *loc;
76 	const char *index = "index.gmi";
77 
78 	if (v == NULL || path == NULL)
79 		return index;
80 
81 	for (loc = &v->locations[1]; loc->match != NULL; ++loc) {
82 		if (!fnmatch(loc->match, path, 0)) {
83 			if (loc->index != NULL)
84 				return loc->index;
85 		}
86 	}
87 
88 	if (v->locations[0].index != NULL)
89 		return v->locations[0].index;
90 	return index;
91 }
92 
93 int
94 vhost_auto_index(struct vhost *v, const char *path)
95 {
96 	struct location *loc;
97 
98 	if (v == NULL || path == NULL)
99 		return 0;
100 
101 	for (loc = v->locations; loc->match != NULL; ++loc) {
102 		if (!fnmatch(loc->match, path, 0)) {
103 			if (loc->auto_index != 0)
104 				return loc->auto_index == 1;
105 		}
106 	}
107 
108 	return v->locations[0].auto_index == 1;
109 }
110 
111 int
112 check_path(struct client *c, const char *path, int *fd)
113 {
114 	struct stat sb;
115 	const char *p;
116 	int flags;
117 
118 	assert(path != NULL);
119 
120 	if (*path == '\0')
121 		p = ".";
122 	else if (*path == '/')
123 		/* in send_dir we add an initial / (to be
124 		 * redirect-friendly), but here we want to skip it */
125 		p = path+1;
126 	else
127 		p = path;
128 
129 	flags = O_RDONLY | O_NOFOLLOW;
130 
131 	if (*fd == -1 && (*fd = openat(c->host->dirfd, p, flags)) == -1)
132 		return FILE_MISSING;
133 
134 	if (fstat(*fd, &sb) == -1) {
135 		LOGN(c, "failed stat for %s: %s", path, strerror(errno));
136 		return FILE_MISSING;
137 	}
138 
139 	if (S_ISDIR(sb.st_mode))
140 		return FILE_DIRECTORY;
141 
142 	if (sb.st_mode & S_IXUSR)
143 		return FILE_EXECUTABLE;
144 
145 	return FILE_EXISTS;
146 }
147 
148 void
149 open_file(struct pollfd *fds, struct client *c)
150 {
151 	switch (check_path(c, c->iri.path, &c->fd)) {
152 	case FILE_EXECUTABLE:
153 		if (starts_with(c->iri.path, c->host->cgi)) {
154 			start_cgi(c->iri.path, "", fds, c);
155 			return;
156 		}
157 
158 		/* fallthrough */
159 
160 	case FILE_EXISTS:
161 		load_file(fds, c);
162 		return;
163 
164 	case FILE_DIRECTORY:
165 		open_dir(fds, c);
166 		return;
167 
168 	case FILE_MISSING:
169 		if (c->host->cgi != NULL && starts_with(c->iri.path, c->host->cgi)) {
170 			check_for_cgi(fds, c);
171 			return;
172 		}
173 		start_reply(fds, c, NOT_FOUND, "not found");
174 		return;
175 
176 	default:
177 		/* unreachable */
178 		abort();
179 	}
180 }
181 
182 void
183 load_file(struct pollfd *fds, struct client *c)
184 {
185 	if ((c->len = filesize(c->fd)) == -1) {
186 		LOGE(c, "failed to get file size for %s", c->iri.path);
187 		start_reply(fds, c, TEMP_FAILURE, "internal server error");
188 		return;
189 	}
190 
191 	if ((c->buf = mmap(NULL, c->len, PROT_READ, MAP_PRIVATE,
192 		    c->fd, 0)) == MAP_FAILED) {
193 		LOGW(c, "mmap: %s: %s", c->iri.path, strerror(errno));
194 		start_reply(fds, c, TEMP_FAILURE, "internal server error");
195 		return;
196 	}
197 	c->i = c->buf;
198 	c->next = send_file;
199 	start_reply(fds, c, SUCCESS, mime(c->host, c->iri.path));
200 }
201 
202 /*
203  * the inverse of this algorithm, i.e. starting from the start of the
204  * path + strlen(cgi), and checking if each component, should be
205  * faster.  But it's tedious to write.  This does the opposite: starts
206  * from the end and strip one component at a time, until either an
207  * executable is found or we emptied the path.
208  */
209 void
210 check_for_cgi(struct pollfd *fds, struct client *c)
211 {
212 	char path[PATH_MAX];
213 	char *end;
214 
215 	strlcpy(path, c->iri.path, sizeof(path));
216 	end = strchr(path, '\0');
217 
218 	/* NB: assume CGI is enabled and path matches cgi */
219 
220 	while (end > path) {
221 		/* go up one level.  UNIX paths are simple and POSIX
222 		 * dirname, with its ambiguities on if the given path
223 		 * is changed or not, gives me headaches. */
224 		while (*end != '/')
225 			end--;
226 		*end = '\0';
227 
228 		switch (check_path(c, path, &c->fd)) {
229 		case FILE_EXECUTABLE:
230 			start_cgi(path, end+1, fds, c);
231 			return;
232 		case FILE_MISSING:
233 			break;
234 		default:
235 			goto err;
236 		}
237 
238 		*end = '/';
239 		end--;
240 	}
241 
242 err:
243 	start_reply(fds, c, NOT_FOUND, "not found");
244 	return;
245 }
246 
247 void
248 mark_nonblock(int fd)
249 {
250 	int flags;
251 
252 	if ((flags = fcntl(fd, F_GETFL)) == -1)
253 		fatal("fcntl(F_GETFL): %s", strerror(errno));
254 	if (fcntl(fd, F_SETFL, flags | O_NONBLOCK) == -1)
255 		fatal("fcntl(F_SETFL): %s", strerror(errno));
256 }
257 
258 void
259 handle_handshake(struct pollfd *fds, struct client *c)
260 {
261 	struct vhost *h;
262 	const char *servname;
263 	const char *parse_err = "unknown error";
264 
265 	switch (tls_handshake(c->ctx)) {
266 	case 0:  /* success */
267 	case -1: /* already handshaked */
268 		break;
269 	case TLS_WANT_POLLIN:
270 		fds->events = POLLIN;
271 		return;
272 	case TLS_WANT_POLLOUT:
273 		fds->events = POLLOUT;
274 		return;
275 	default:
276 		/* unreachable */
277 		abort();
278 	}
279 
280 	servname = tls_conn_servername(c->ctx);
281 	if (!puny_decode(servname, c->domain, sizeof(c->domain), &parse_err)) {
282 		LOGI(c, "%s", parse_err);
283 		goto err;
284 	}
285 
286 	for (h = hosts; h->domain != NULL; ++h) {
287 		if (!fnmatch(h->domain, c->domain, 0))
288 			break;
289 	}
290 
291 	/* LOGD(c, "handshake: SNI: \"%s\"; decoded: \"%s\"; matched: \"%s\"", */
292 	/*     servname != NULL ? servname : "(null)", */
293 	/*     c->domain, */
294 	/*     h->domain != NULL ? h->domain : "(null)"); */
295 
296 	if (h->domain != NULL) {
297 		c->state = handle_open_conn;
298 		c->host = h;
299 		handle_open_conn(fds, c);
300 		return;
301 	}
302 
303 err:
304 	if (servname != NULL)
305 		strncpy(c->req, servname, sizeof(c->req));
306 	else
307 		strncpy(c->req, "null", sizeof(c->req));
308 
309 	start_reply(fds, c, BAD_REQUEST, "Wrong/malformed host or missing SNI");
310 }
311 
312 void
313 handle_open_conn(struct pollfd *fds, struct client *c)
314 {
315 	const char *parse_err = "invalid request";
316 	char decoded[DOMAIN_NAME_LEN];
317 
318 	bzero(c->req, sizeof(c->req));
319 	bzero(&c->iri, sizeof(c->iri));
320 
321 	switch (tls_read(c->ctx, c->req, sizeof(c->req)-1)) {
322 	case -1:
323 		LOGE(c, "tls_read: %s", tls_error(c->ctx));
324 		close_conn(fds, c);
325 		return;
326 
327 	case TLS_WANT_POLLIN:
328 		fds->events = POLLIN;
329 		return;
330 
331 	case TLS_WANT_POLLOUT:
332 		fds->events = POLLOUT;
333 		return;
334 	}
335 
336 	if (!trim_req_iri(c->req, &parse_err)
337 	    || !parse_iri(c->req, &c->iri, &parse_err)
338 	    || !puny_decode(c->iri.host, decoded, sizeof(decoded), &parse_err)) {
339 		LOGI(c, "iri parse error: %s", parse_err);
340 		start_reply(fds, c, BAD_REQUEST, "invalid request");
341 		return;
342 	}
343 
344 	if (c->iri.port_no != conf.port
345 	    || strcmp(c->iri.schema, "gemini")
346 	    || strcmp(decoded, c->domain)) {
347 		start_reply(fds, c, PROXY_REFUSED, "won't proxy request");
348 		return;
349 	}
350 
351 	open_file(fds, c);
352 }
353 
354 void
355 start_reply(struct pollfd *pfd, struct client *c, int code, const char *meta)
356 {
357 	c->code = code;
358 	c->meta = meta;
359 	c->state = handle_start_reply;
360 	c->state(pfd, c);
361 }
362 
363 void
364 handle_start_reply(struct pollfd *pfd, struct client *c)
365 {
366 	char buf[1030];		/* status + ' ' + max reply len + \r\n\0 */
367 	const char *lang;
368 	size_t len;
369 
370 	lang = vhost_lang(c->host, c->iri.path);
371 
372 	snprintf(buf, sizeof(buf), "%d ", c->code);
373 	strlcat(buf, c->meta, sizeof(buf));
374 	if (!strcmp(c->meta, "text/gemini") && lang != NULL) {
375 		strlcat(buf, "; lang=", sizeof(buf));
376 		strlcat(buf, lang, sizeof(buf));
377 	}
378 
379 	len = strlcat(buf, "\r\n", sizeof(buf));
380 	assert(len < sizeof(buf));
381 
382 	switch (tls_write(c->ctx, buf, len)) {
383 	case -1:
384 		close_conn(pfd, c);
385 		return;
386 	case TLS_WANT_POLLIN:
387 		pfd->events = POLLIN;
388 		return;
389 	case TLS_WANT_POLLOUT:
390 		pfd->events = POLLOUT;
391 		return;
392 	}
393 
394 	log_request(c, buf, sizeof(buf));
395 
396 	/* we don't need a body */
397 	if (c->code != SUCCESS) {
398 		close_conn(pfd, c);
399 		return;
400 	}
401 
402 	/* advance the state machine */
403 	c->state = c->next;
404 	c->state(pfd, c);
405 }
406 
407 void
408 start_cgi(const char *spath, const char *relpath,
409     struct pollfd *fds, struct client *c)
410 {
411 	char addr[NI_MAXHOST];
412 	const char *ruser, *cissuer, *chash;
413 	int e;
414 
415 	e = getnameinfo((struct sockaddr*)&c->addr, sizeof(c->addr),
416 	    addr, sizeof(addr),
417 	    NULL, 0,
418 	    NI_NUMERICHOST);
419 	if (e != 0)
420 		goto err;
421 
422 	if (tls_peer_cert_provided(c->ctx)) {
423 		ruser = tls_peer_cert_subject(c->ctx);
424 		cissuer = tls_peer_cert_issuer(c->ctx);
425 		chash = tls_peer_cert_hash(c->ctx);
426 	} else {
427 		ruser = NULL;
428 		cissuer = NULL;
429 		chash = NULL;
430 	}
431 
432 	if (!send_iri(exfd, &c->iri)
433 	    || !send_string(exfd, spath)
434 	    || !send_string(exfd, relpath)
435 	    || !send_string(exfd, addr)
436 	    || !send_string(exfd, ruser)
437 	    || !send_string(exfd, cissuer)
438 	    || !send_string(exfd, chash)
439 	    || !send_vhost(exfd, c->host))
440 		goto err;
441 
442 	close(c->fd);
443 	if ((c->fd = recv_fd(exfd)) == -1) {
444 		start_reply(fds, c, TEMP_FAILURE, "internal server error");
445 		return;
446 	}
447 	c->state = handle_cgi;
448 	cgi_poll_on_child(fds, c);
449 	c->code = -1;
450 	/* handle_cgi(fds, c); */
451 	return;
452 
453 err:
454 	/* fatal("cannot talk to the executor process: %s", strerror(errno)); */
455 	fatal("cannot talk to the executor process");
456 }
457 
458 void
459 send_file(struct pollfd *fds, struct client *c)
460 {
461 	ssize_t ret, len;
462 
463 	len = (c->buf + c->len) - c->i;
464 
465 	while (len > 0) {
466 		switch (ret = tls_write(c->ctx, c->i, len)) {
467 		case -1:
468 			LOGE(c, "tls_write: %s", tls_error(c->ctx));
469 			close_conn(fds, c);
470 			return;
471 
472 		case TLS_WANT_POLLIN:
473 			fds->events = POLLIN;
474 			return;
475 
476 		case TLS_WANT_POLLOUT:
477 			fds->events = POLLOUT;
478 			return;
479 
480 		default:
481 			c->i += ret;
482 			len -= ret;
483 			break;
484 		}
485 	}
486 
487 	close_conn(fds, c);
488 }
489 
490 void
491 open_dir(struct pollfd *fds, struct client *c)
492 {
493 	size_t len;
494 	int dirfd;
495 	char *before_file;
496 
497 	len = strlen(c->iri.path);
498 	if (len > 0 && !ends_with(c->iri.path, "/")) {
499 		redirect_canonical_dir(fds, c);
500 		return;
501 	}
502 
503 	strlcpy(c->sbuf, "/", sizeof(c->sbuf));
504 	strlcat(c->sbuf, c->iri.path, sizeof(c->sbuf));
505 	if (!ends_with(c->sbuf, "/"))
506 		strlcat(c->sbuf, "/", sizeof(c->sbuf));
507 	before_file = strchr(c->sbuf, '\0');
508 	len = strlcat(c->sbuf, vhost_index(c->host, c->iri.path),
509 	    sizeof(c->sbuf));
510 	if (len >= sizeof(c->sbuf)) {
511 		start_reply(fds, c, TEMP_FAILURE, "internal server error");
512 		return;
513 	}
514 
515 	c->iri.path = c->sbuf;
516 
517 	/* close later unless we have to generate the dir listing */
518 	dirfd = c->fd;
519 	c->fd = -1;
520 
521 	switch (check_path(c, c->iri.path, &c->fd)) {
522 	case FILE_EXECUTABLE:
523 		if (starts_with(c->iri.path, c->host->cgi)) {
524 			start_cgi(c->iri.path, "", fds, c);
525 			break;
526 		}
527 
528 		/* fallthrough */
529 
530 	case FILE_EXISTS:
531                 load_file(fds, c);
532 		break;
533 
534 	case FILE_DIRECTORY:
535 		start_reply(fds, c, TEMP_REDIRECT, c->sbuf);
536 		break;
537 
538 	case FILE_MISSING:
539 		*before_file = '\0';
540 
541 		if (!vhost_auto_index(c->host, c->iri.path)) {
542 			start_reply(fds, c, NOT_FOUND, "not found");
543 			break;
544 		}
545 
546 		c->fd = dirfd;
547 		c->next = send_directory_listing;
548 
549 		if ((c->dir = fdopendir(c->fd)) == NULL) {
550 			LOGE(c, "can't fdopendir(%d) (vhost:%s) %s: %s",
551 			    c->fd, c->host->domain, c->iri.path, strerror(errno));
552 			start_reply(fds, c, TEMP_FAILURE, "internal server error");
553 			return;
554 		}
555 		c->off = 0;
556 
557                 start_reply(fds, c, SUCCESS, "text/gemini");
558 		return;
559 
560 	default:
561 		/* unreachable */
562 		abort();
563 	}
564 
565 	close(dirfd);
566 }
567 
568 void
569 redirect_canonical_dir(struct pollfd *fds, struct client *c)
570 {
571 	size_t len;
572 
573 	strlcpy(c->sbuf, "/", sizeof(c->sbuf));
574 	strlcat(c->sbuf, c->iri.path, sizeof(c->sbuf));
575 	len = strlcat(c->sbuf, "/", sizeof(c->sbuf));
576 
577 	if (len >= sizeof(c->sbuf)) {
578 		start_reply(fds, c, TEMP_FAILURE, "internal server error");
579 		return;
580 	}
581 
582 	start_reply(fds, c, TEMP_REDIRECT, c->sbuf);
583 }
584 
585 int
586 read_next_dir_entry(struct client *c)
587 {
588 	struct dirent *d;
589 
590 	do {
591 		errno = 0;
592 		if ((d = readdir(c->dir)) == NULL) {
593 			if (errno != 0)
594 				LOGE(c, "readdir: %s", strerror(errno));
595 			return 0;
596 		}
597 	} while (!strcmp(d->d_name, "."));
598 
599 	/* XXX: url escape */
600 	snprintf(c->sbuf, sizeof(c->sbuf), "=> %s %s\n",
601 	    d->d_name, d->d_name);
602 	c->len = strlen(c->sbuf);
603 	c->off = 0;
604 
605 	return 1;
606 }
607 
608 void
609 send_directory_listing(struct pollfd *fds, struct client *c)
610 {
611 	ssize_t r;
612 
613 	while (1) {
614 		if (c->len == 0) {
615 			if (!read_next_dir_entry(c))
616 				goto end;
617 		}
618 
619 		while (c->len > 0) {
620 			switch (r = tls_write(c->ctx, c->sbuf + c->off, c->len)) {
621 			case -1:
622 				goto end;
623 
624 			case TLS_WANT_POLLOUT:
625 				fds->events = POLLOUT;
626 				return;
627 
628 			case TLS_WANT_POLLIN:
629 				fds->events = POLLIN;
630 				return;
631 
632 			default:
633 				c->off += r;
634 				c->len -= r;
635 				break;
636 			}
637 		}
638 	}
639 
640 end:
641 	close_conn(fds, c);
642 }
643 
644 void
645 cgi_poll_on_child(struct pollfd *fds, struct client *c)
646 {
647 	int fd;
648 
649 	if (c->waiting_on_child)
650 		return;
651 	c->waiting_on_child = 1;
652 
653 	fds->events = POLLIN;
654 
655 	fd = fds->fd;
656 	fds->fd = c->fd;
657 	c->fd = fd;
658 }
659 
660 void
661 cgi_poll_on_client(struct pollfd *fds, struct client *c)
662 {
663 	int fd;
664 
665 	if (!c->waiting_on_child)
666 		return;
667 	c->waiting_on_child = 0;
668 
669 	fd = fds->fd;
670 	fds->fd = c->fd;
671 	c->fd = fd;
672 }
673 
674 /* handle the read from the child process.  Return like read(2) */
675 static ssize_t
676 read_from_cgi(struct client *c)
677 {
678 	void	*buf;
679 	size_t	 len;
680 	ssize_t	 r;
681 
682 	/* if we haven't read a whole response line, we want to
683 	 * continue reading. */
684 
685 	if (c->code == -1) {
686 		buf = c->sbuf + c->len;
687 		len = sizeof(c->sbuf) - c->len;
688 	} else {
689 		buf = c->sbuf;
690 		len = sizeof(c->sbuf);
691 	}
692 
693 	r = read(c->fd, buf, len);
694 	if (r == 0 || r == -1)
695 		return r;
696 
697 	c->len += r;
698 	c->off = 0;
699 
700 	if (c->code != -1)
701 		return r;
702 
703 	if (strchr(c->sbuf, '\n') || c->len == sizeof(c->sbuf)) {
704 		c->code = 0;
705 		log_request(c, c->sbuf, c->len);
706 	}
707 
708 	return r;
709 }
710 
711 void
712 handle_cgi(struct pollfd *fds, struct client *c)
713 {
714 	ssize_t r;
715 
716 	/* ensure c->fd is the child and fds->fd the client */
717 	cgi_poll_on_client(fds, c);
718 
719 	while (1) {
720 		if (c->code == -1 || c->len == 0) {
721 			switch (r = read_from_cgi(c)) {
722 			case 0:
723 				goto end;
724 
725 			case -1:
726 				if (errno == EAGAIN || errno == EWOULDBLOCK) {
727 					cgi_poll_on_child(fds, c);
728 					return;
729 				}
730 				goto end;
731 			}
732 		}
733 
734 		if (c->code == -1) {
735 			cgi_poll_on_child(fds, c);
736 			return;
737 		}
738 
739 		while (c->len > 0) {
740 			switch (r = tls_write(c->ctx, c->sbuf + c->off, c->len)) {
741 			case -1:
742 				goto end;
743 
744 			case TLS_WANT_POLLOUT:
745 				fds->events = POLLOUT;
746 				return;
747 
748 			case TLS_WANT_POLLIN:
749 				fds->events = POLLIN;
750 				return;
751 
752 			default:
753                                 c->off += r;
754 				c->len -= r;
755 				break;
756 			}
757 		}
758 	}
759 
760 end:
761 	close_conn(fds, c);
762 }
763 
764 void
765 close_conn(struct pollfd *pfd, struct client *c)
766 {
767 	c->state = close_conn;
768 
769 	switch (tls_close(c->ctx)) {
770 	case TLS_WANT_POLLIN:
771 		pfd->events = POLLIN;
772 		return;
773 	case TLS_WANT_POLLOUT:
774 		pfd->events = POLLOUT;
775 		return;
776 	}
777 
778 	connected_clients--;
779 
780 	tls_free(c->ctx);
781 	c->ctx = NULL;
782 
783 	if (c->buf != MAP_FAILED)
784 		munmap(c->buf, c->len);
785 
786 	if (c->fd != -1)
787 		close(c->fd);
788 
789 	if (c->dir != NULL)
790 		closedir(c->dir);
791 
792 	close(pfd->fd);
793 	pfd->fd = -1;
794 }
795 
796 void
797 do_accept(int sock, struct tls *ctx, struct pollfd *fds, struct client *clients)
798 {
799 	int i, fd;
800 	struct sockaddr_storage addr;
801 	socklen_t len;
802 
803 	len = sizeof(addr);
804 	if ((fd = accept(sock, (struct sockaddr*)&addr, &len)) == -1) {
805 		if (errno == EWOULDBLOCK)
806 			return;
807 		fatal("accept: %s", strerror(errno));
808 	}
809 
810 	mark_nonblock(fd);
811 
812 	for (i = 0; i < MAX_USERS; ++i) {
813 		if (fds[i].fd == -1) {
814 			bzero(&clients[i], sizeof(struct client));
815 			if (tls_accept_socket(ctx, &clients[i].ctx, fd) == -1)
816 				break; /* goodbye fd! */
817 
818 			fds[i].fd = fd;
819 			fds[i].events = POLLIN;
820 
821 			clients[i].state = handle_handshake;
822 			clients[i].next = send_file;
823 			clients[i].fd = -1;
824 			clients[i].waiting_on_child = 0;
825 			clients[i].buf = MAP_FAILED;
826 			clients[i].dir = NULL;
827 			clients[i].addr = addr;
828 
829 			connected_clients++;
830 			return;
831 		}
832 	}
833 
834 	close(fd);
835 }
836 
837 void
838 loop(struct tls *ctx, int sock4, int sock6)
839 {
840 	int i;
841 	struct client clients[MAX_USERS];
842 	struct pollfd fds[MAX_USERS];
843 
844 	connected_clients = 0;
845 
846 	for (i = 0; i < MAX_USERS; ++i) {
847 		fds[i].fd = -1;
848 		fds[i].events = POLLIN;
849 		bzero(&clients[i], sizeof(struct client));
850 	}
851 
852 	fds[0].fd = sock4;
853 	fds[1].fd = sock6;
854 
855 	for (;;) {
856 		if (poll(fds, MAX_USERS, INFTIM) == -1) {
857 			if (errno == EINTR) {
858                                 fprintf(stderr, "connected clients: %d\n",
859 				    connected_clients);
860 				continue;
861 			}
862 			fatal("poll: %s", strerror(errno));
863 		}
864 
865 		for (i = 0; i < MAX_USERS; i++) {
866 			if (fds[i].revents == 0)
867 				continue;
868 
869 			if (fds[i].revents & (POLLERR|POLLNVAL))
870 				fatal("bad fd %d: %s", fds[i].fd,
871 				    strerror(errno));
872 
873 			if (fds[i].revents & POLLHUP) {
874 				/* fds[i] may be the fd of the stdin
875 				 * of a cgi script that has exited. */
876 				if (!clients[i].waiting_on_child) {
877 					close_conn(&fds[i], &clients[i]);
878 					continue;
879 				}
880 			}
881 
882 			if (fds[i].fd == sock4)
883 				do_accept(sock4, ctx, fds, clients);
884 			else if (fds[i].fd == sock6)
885 				do_accept(sock6, ctx, fds, clients);
886 			else
887 				clients[i].state(&fds[i], &clients[i]);
888 		}
889 	}
890 }