proxy_pollmgr.c@ 73747

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1	/* $Id: proxy_pollmgr.c 69500 2017-10-28 15:14:05Z vboxsync $ */
2	/** @file
3	* NAT Network - poll manager.
4	*/
5
6	/*
7	* Copyright (C) 2013-2017 Oracle Corporation
8	*
9	* This file is part of VirtualBox Open Source Edition (OSE), as
10	* available from http://www.virtualbox.org. This file is free software;
11	* you can redistribute it and/or modify it under the terms of the GNU
12	* General Public License (GPL) as published by the Free Software
13	* Foundation, in version 2 as it comes in the "COPYING" file of the
14	* VirtualBox OSE distribution. VirtualBox OSE is distributed in the
15	* hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
16	*/
17
18	#define LOG_GROUP LOG_GROUP_NAT_SERVICE
19
20	#include "winutils.h"
21
22	#include "proxy_pollmgr.h"
23	#include "proxy.h"
24
25	#ifndef RT_OS_WINDOWS
26	#include <sys/socket.h>
27	#include <netinet/in.h>
28	#include <err.h>
29	#include <errno.h>
30	#include <fcntl.h>
31	#include <poll.h>
32	#include <stdio.h>
33	#include <stdlib.h>
34	#include <string.h>
35	#include <time.h>
36	#include <unistd.h>
37	#else
38	#include <iprt/err.h>
39	#include <stdlib.h>
40	#include <string.h>
41	#include "winpoll.h"
42	#endif
43
44	#include <iprt/req.h>
45	#include <iprt/err.h>
46
47
48	#define POLLMGR_GARBAGE (-1)
49
50
51	enum {
52	POLLMGR_QUEUE = 0,
53
54	POLLMGR_SLOT_STATIC_COUNT,
55	POLLMGR_SLOT_FIRST_DYNAMIC = POLLMGR_SLOT_STATIC_COUNT
56	};
57
58
59	struct pollmgr_chan {
60	struct pollmgr_handler *handler;
61	void *arg;
62	bool arg_valid;
63	};
64
65	struct pollmgr {
66	struct pollfd *fds;
67	struct pollmgr_handler **handlers;
68	nfds_t capacity; /* allocated size of the arrays */
69	nfds_t nfds; /* part of the arrays in use */
70
71	/* channels (socketpair) for static slots */
72	SOCKET chan[POLLMGR_SLOT_STATIC_COUNT][2];
73	#define POLLMGR_CHFD_RD 0 /* - pollmgr side */
74	#define POLLMGR_CHFD_WR 1 /* - client side */
75
76
77	/* emulate channels with request queue */
78	RTREQQUEUE queue;
79	struct pollmgr_handler queue_handler;
80	struct pollmgr_chan chan_handlers[POLLMGR_CHAN_COUNT];
81	} pollmgr;
82
83
84	static int pollmgr_queue_callback(struct pollmgr_handler *, SOCKET, int);
85	static void pollmgr_chan_call_handler(int, void *);
86
87	static void pollmgr_loop(void);
88
89	static void pollmgr_add_at(int, struct pollmgr_handler *, SOCKET, int);
90	static void pollmgr_refptr_delete(struct pollmgr_refptr *);
91
92
93	/*
94	* We cannot portably peek at the length of the incoming datagram and
95	* pre-allocate pbuf chain to recvmsg() directly to it. On Linux it's
96	* possible to recv with MSG_PEEK\|MSG_TRUC, but extra syscall is
97	* probably more expensive (haven't measured) than doing an extra copy
98	* of data, since typical UDP datagrams are small enough to avoid
99	* fragmentation.
100	*
101	* We can use shared buffer here since we read from sockets
102	* sequentially in a loop over pollfd.
103	*/
104	u8_t pollmgr_udpbuf[64 * 1024];
105
106
107	int
108	pollmgr_init(void)
109	{
110	struct pollfd *newfds;
111	struct pollmgr_handler **newhdls;
112	nfds_t newcap;
113	int rc, status;
114	nfds_t i;
115
116	rc = RTReqQueueCreate(&pollmgr.queue);
117	if (RT_FAILURE(rc))
118	return -1;
119
120	pollmgr.fds = NULL;
121	pollmgr.handlers = NULL;
122	pollmgr.capacity = 0;
123	pollmgr.nfds = 0;
124
125	for (i = 0; i < POLLMGR_SLOT_STATIC_COUNT; ++i) {
126	pollmgr.chan[i][POLLMGR_CHFD_RD] = INVALID_SOCKET;
127	pollmgr.chan[i][POLLMGR_CHFD_WR] = INVALID_SOCKET;
128	}
129
130	for (i = 0; i < POLLMGR_SLOT_STATIC_COUNT; ++i) {
131	#ifndef RT_OS_WINDOWS
132	int j;
133
134	status = socketpair(PF_LOCAL, SOCK_DGRAM, 0, pollmgr.chan[i]);
135	if (status < 0) {
136	DPRINTF(("socketpair: %R[sockerr]\n", SOCKERRNO()));
137	goto cleanup_close;
138	}
139
140	/* now manually make them O_NONBLOCK */
141	for (j = 0; j < 2; ++j) {
142	int s = pollmgr.chan[i][j];
143	int sflags;
144
145	sflags = fcntl(s, F_GETFL, 0);
146	if (sflags < 0) {
147	DPRINTF0(("F_GETFL: %R[sockerr]\n", errno));
148	goto cleanup_close;
149	}
150
151	status = fcntl(s, F_SETFL, sflags \| O_NONBLOCK);
152	if (status < 0) {
153	DPRINTF0(("O_NONBLOCK: %R[sockerr]\n", errno));
154	goto cleanup_close;
155	}
156	}
157	#else
158	status = RTWinSocketPair(PF_INET, SOCK_DGRAM, 0, pollmgr.chan[i]);
159	if (RT_FAILURE(status)) {
160	goto cleanup_close;
161	}
162	#endif
163	}
164
165
166	newcap = 16; /* XXX: magic */
167	LWIP_ASSERT1(newcap >= POLLMGR_SLOT_STATIC_COUNT);
168
169	newfds = (struct pollfd *)
170	malloc(newcap * sizeof(*pollmgr.fds));
171	if (newfds == NULL) {
172	DPRINTF(("%s: Failed to allocate fds array\n", __func__));
173	goto cleanup_close;
174	}
175
176	newhdls = (struct pollmgr_handler **)
177	malloc(newcap * sizeof(*pollmgr.handlers));
178	if (newhdls == NULL) {
179	DPRINTF(("%s: Failed to allocate handlers array\n", __func__));
180	free(newfds);
181	goto cleanup_close;
182	}
183
184	pollmgr.capacity = newcap;
185	pollmgr.fds = newfds;
186	pollmgr.handlers = newhdls;
187
188	pollmgr.nfds = POLLMGR_SLOT_STATIC_COUNT;
189
190	for (i = 0; i < pollmgr.capacity; ++i) {
191	pollmgr.fds[i].fd = INVALID_SOCKET;
192	pollmgr.fds[i].events = 0;
193	pollmgr.fds[i].revents = 0;
194	}
195
196	/* add request queue notification */
197	pollmgr.queue_handler.callback = pollmgr_queue_callback;
198	pollmgr.queue_handler.data = NULL;
199	pollmgr.queue_handler.slot = -1;
200
201	pollmgr_add_at(POLLMGR_QUEUE, &pollmgr.queue_handler,
202	pollmgr.chan[POLLMGR_QUEUE][POLLMGR_CHFD_RD],
203	POLLIN);
204
205	return 0;
206
207	cleanup_close:
208	for (i = 0; i < POLLMGR_SLOT_STATIC_COUNT; ++i) {
209	SOCKET *chan = pollmgr.chan[i];
210	if (chan[POLLMGR_CHFD_RD] != INVALID_SOCKET) {
211	closesocket(chan[POLLMGR_CHFD_RD]);
212	closesocket(chan[POLLMGR_CHFD_WR]);
213	}
214	}
215
216	return -1;
217	}
218
219
220	/*
221	* Add new channel. We now implement channels with request queue, so
222	* all channels get the same socket that triggers queue processing.
223	*
224	* Must be called before pollmgr loop is started, so no locking.
225	*/
226	SOCKET
227	pollmgr_add_chan(int slot, struct pollmgr_handler *handler)
228	{
229	AssertReturn(0 <= slot && slot < POLLMGR_CHAN_COUNT, INVALID_SOCKET);
230	AssertReturn(handler != NULL && handler->callback != NULL, INVALID_SOCKET);
231
232	handler->slot = slot;
233	pollmgr.chan_handlers[slot].handler = handler;
234	return pollmgr.chan[POLLMGR_QUEUE][POLLMGR_CHFD_WR];
235	}
236
237
238	/*
239	* This used to actually send data over the channel's socket. Now we
240	* queue a request and send single byte notification over shared
241	* POLLMGR_QUEUE socket.
242	*/
243	ssize_t
244	pollmgr_chan_send(int slot, void *buf, size_t nbytes)
245	{
246	static const char notification = 0x5a;
247
248	void *ptr;
249	SOCKET fd;
250	ssize_t nsent;
251	int rc;
252
253	AssertReturn(0 <= slot && slot < POLLMGR_CHAN_COUNT, -1);
254
255	/*
256	* XXX: Hack alert. We only ever "sent" single pointer which was
257	* simultaneously both the wakeup event for the poll and the
258	* argument for the channel handler that it read from the channel.
259	* So now we pass this pointer to the request and arrange for the
260	* handler to "read" it when it asks for it.
261	*/
262	if (nbytes != sizeof(void *)) {
263	return -1;
264	}
265
266	ptr = (void *)buf;
267
268	rc = RTReqQueueCallEx(pollmgr.queue, NULL, 0,
269	RTREQFLAGS_VOID \| RTREQFLAGS_NO_WAIT,
270	(PFNRT)pollmgr_chan_call_handler, 2,
271	slot, ptr);
272
273	fd = pollmgr.chan[POLLMGR_QUEUE][POLLMGR_CHFD_WR];
274	nsent = send(fd, &notification, 1, 0);
275	if (nsent == SOCKET_ERROR) {
276	DPRINTF(("send on chan %d: %R[sockerr]\n", slot, SOCKERRNO()));
277	return -1;
278	}
279	else if ((size_t)nsent != 1) {
280	DPRINTF(("send on chan %d: datagram truncated to %u bytes",
281	slot, (unsigned int)nsent));
282	return -1;
283	}
284
285	/* caller thinks it's sending the pointer */
286	return sizeof(void *);
287	}
288
289
290	/*
291	* pollmgr_chan_send() sent us a notification, process the queue.
292	*/
293	static int
294	pollmgr_queue_callback(struct pollmgr_handler *handler, SOCKET fd, int revents)
295	{
296	ssize_t nread;
297	int sockerr;
298	int rc;
299
300	RT_NOREF(handler, revents);
301	Assert(pollmgr.queue != NIL_RTREQQUEUE);
302
303	nread = recv(fd, (char *)pollmgr_udpbuf, sizeof(pollmgr_udpbuf), 0);
304	sockerr = SOCKERRNO(); /* save now, may be clobbered */
305
306	if (nread == SOCKET_ERROR) {
307	DPRINTF0(("%s: recv: %R[sockerr]\n", __func__, sockerr));
308	return POLLIN;
309	}
310
311	DPRINTF2(("%s: read %zd\n", __func__, nread));
312	if (nread == 0) {
313	return POLLIN;
314	}
315
316	rc = RTReqQueueProcess(pollmgr.queue, 0);
317	if (RT_UNLIKELY(rc != VERR_TIMEOUT && RT_FAILURE_NP(rc))) {
318	DPRINTF0(("%s: RTReqQueueProcess: %Rrc\n", __func__, rc));
319	}
320
321	return POLLIN;
322	}
323
324
325	/*
326	* Queued requests use this function to emulate the call to the
327	* handler's callback.
328	*/
329	static void
330	pollmgr_chan_call_handler(int slot, void *arg)
331	{
332	struct pollmgr_handler *handler;
333	int nevents;
334
335	AssertReturnVoid(0 <= slot && slot < POLLMGR_CHAN_COUNT);
336
337	handler = pollmgr.chan_handlers[slot].handler;
338	AssertReturnVoid(handler != NULL && handler->callback != NULL);
339
340	/* arrange for pollmgr_chan_recv_ptr() to "receive" the arg */
341	pollmgr.chan_handlers[slot].arg = arg;
342	pollmgr.chan_handlers[slot].arg_valid = true;
343
344	nevents = handler->callback(handler, INVALID_SOCKET, POLLIN);
345	if (nevents != POLLIN) {
346	DPRINTF2(("%s: nevents=0x%x!\n", __func__, nevents));
347	}
348	}
349
350
351	/*
352	* "Receive" a pointer "sent" over poll manager channel.
353	*/
354	void *
355	pollmgr_chan_recv_ptr(struct pollmgr_handler *handler, SOCKET fd, int revents)
356	{
357	int slot;
358	void *ptr;
359
360	RT_NOREF(fd);
361
362	slot = handler->slot;
363	Assert(0 <= slot && slot < POLLMGR_CHAN_COUNT);
364
365	if (revents & POLLNVAL) {
366	errx(EXIT_FAILURE, "chan %d: fd invalid", (int)handler->slot);
367	/* NOTREACHED */
368	}
369
370	if (revents & (POLLERR \| POLLHUP)) {
371	errx(EXIT_FAILURE, "chan %d: fd error", (int)handler->slot);
372	/* NOTREACHED */
373	}
374
375	LWIP_ASSERT1(revents & POLLIN);
376
377	if (!pollmgr.chan_handlers[slot].arg_valid) {
378	err(EXIT_FAILURE, "chan %d: recv", (int)handler->slot);
379	/* NOTREACHED */
380	}
381
382	ptr = pollmgr.chan_handlers[slot].arg;
383	pollmgr.chan_handlers[slot].arg_valid = false;
384
385	return ptr;
386	}
387
388
389	/*
390	* Must be called from pollmgr loop (via callbacks), so no locking.
391	*/
392	int
393	pollmgr_add(struct pollmgr_handler *handler, SOCKET fd, int events)
394	{
395	int slot;
396
397	DPRINTF2(("%s: new fd %d\n", __func__, fd));
398
399	if (pollmgr.nfds == pollmgr.capacity) {
400	struct pollfd *newfds;
401	struct pollmgr_handler **newhdls;
402	nfds_t newcap;
403	nfds_t i;
404
405	newcap = pollmgr.capacity * 2;
406
407	newfds = (struct pollfd *)
408	realloc(pollmgr.fds, newcap * sizeof(*pollmgr.fds));
409	if (newfds == NULL) {
410	DPRINTF(("%s: Failed to reallocate fds array\n", __func__));
411	handler->slot = -1;
412	return -1;
413	}
414
415	pollmgr.fds = newfds; /* don't crash/leak if realloc(handlers) fails */
416	/* but don't update capacity yet! */
417
418	newhdls = (struct pollmgr_handler **)
419	realloc(pollmgr.handlers, newcap * sizeof(*pollmgr.handlers));
420	if (newhdls == NULL) {
421	DPRINTF(("%s: Failed to reallocate handlers array\n", __func__));
422	/* if we failed to realloc here, then fds points to the
423	* new array, but we pretend we still has old capacity */
424	handler->slot = -1;
425	return -1;
426	}
427
428	pollmgr.handlers = newhdls;
429	pollmgr.capacity = newcap;
430
431	for (i = pollmgr.nfds; i < newcap; ++i) {
432	newfds[i].fd = INVALID_SOCKET;
433	newfds[i].events = 0;
434	newfds[i].revents = 0;
435	newhdls[i] = NULL;
436	}
437	}
438
439	slot = pollmgr.nfds;
440	++pollmgr.nfds;
441
442	pollmgr_add_at(slot, handler, fd, events);
443	return slot;
444	}
445
446
447	static void
448	pollmgr_add_at(int slot, struct pollmgr_handler *handler, SOCKET fd, int events)
449	{
450	pollmgr.fds[slot].fd = fd;
451	pollmgr.fds[slot].events = events;
452	pollmgr.fds[slot].revents = 0;
453	pollmgr.handlers[slot] = handler;
454
455	handler->slot = slot;
456	}
457
458
459	void
460	pollmgr_update_events(int slot, int events)
461	{
462	LWIP_ASSERT1(slot >= POLLMGR_SLOT_FIRST_DYNAMIC);
463	LWIP_ASSERT1((nfds_t)slot < pollmgr.nfds);
464
465	pollmgr.fds[slot].events = events;
466	}
467
468
469	void
470	pollmgr_del_slot(int slot)
471	{
472	LWIP_ASSERT1(slot >= POLLMGR_SLOT_FIRST_DYNAMIC);
473
474	DPRINTF2(("%s(%d): fd %d ! DELETED\n",
475	__func__, slot, pollmgr.fds[slot].fd));
476
477	pollmgr.fds[slot].fd = INVALID_SOCKET; /* see poll loop */
478	}
479
480
481	void
482	pollmgr_thread(void *ignored)
483	{
484	LWIP_UNUSED_ARG(ignored);
485	pollmgr_loop();
486	}
487
488
489	static void
490	pollmgr_loop(void)
491	{
492	int nready;
493	SOCKET delfirst;
494	SOCKET *pdelprev;
495	int i;
496
497	for (;;) {
498	#ifndef RT_OS_WINDOWS
499	nready = poll(pollmgr.fds, pollmgr.nfds, -1);
500	#else
501	int rc = RTWinPoll(pollmgr.fds, pollmgr.nfds,RT_INDEFINITE_WAIT, &nready);
502	if (RT_FAILURE(rc)) {
503	err(EXIT_FAILURE, "poll"); /* XXX: what to do on error? */
504	/* NOTREACHED*/
505	}
506	#endif
507
508	DPRINTF2(("%s: ready %d fd%s\n",
509	__func__, nready, (nready == 1 ? "" : "s")));
510
511	if (nready < 0) {
512	if (errno == EINTR) {
513	continue;
514	}
515
516	err(EXIT_FAILURE, "poll"); /* XXX: what to do on error? */
517	/* NOTREACHED*/
518	}
519	else if (nready == 0) { /* cannot happen, we wait forever (-1) */
520	continue; /* - but be defensive */
521	}
522
523
524	delfirst = INVALID_SOCKET;
525	pdelprev = &delfirst;
526
527	for (i = 0; (nfds_t)i < pollmgr.nfds && nready > 0; ++i) {
528	struct pollmgr_handler *handler;
529	SOCKET fd;
530	int revents, nevents;
531
532	fd = pollmgr.fds[i].fd;
533	revents = pollmgr.fds[i].revents;
534
535	/*
536	* Channel handlers can request deletion of dynamic slots
537	* by calling pollmgr_del_slot() that clobbers slot's fd.
538	*/
539	if (fd == INVALID_SOCKET && i >= POLLMGR_SLOT_FIRST_DYNAMIC) {
540	/* adjust count if events were pending for that slot */
541	if (revents != 0) {
542	--nready;
543	}
544
545	/* pretend that slot handler requested deletion */
546	nevents = -1;
547	goto update_events;
548	}
549
550	if (revents == 0) {
551	continue; /* next fd */
552	}
553	--nready;
554
555	handler = pollmgr.handlers[i];
556
557	if (handler != NULL && handler->callback != NULL) {
558	#ifdef LWIP_PROXY_DEBUG
559	# if LWIP_PROXY_DEBUG /* DEBUG */
560	if (i < POLLMGR_SLOT_FIRST_DYNAMIC) {
561	if (revents == POLLIN) {
562	DPRINTF2(("%s: ch %d\n", __func__, i));
563	}
564	else {
565	DPRINTF2(("%s: ch %d @ revents 0x%x!\n",
566	__func__, i, revents));
567	}
568	}
569	else {
570	DPRINTF2(("%s: fd %d @ revents 0x%x\n",
571	__func__, fd, revents));
572	}
573	# endif /* LWIP_PROXY_DEBUG / DEBUG */
574	#endif
575	nevents = (*handler->callback)(handler, fd, revents);
576	}
577	else {
578	DPRINTF0(("%s: invalid handler for fd %d: ", __func__, fd));
579	if (handler == NULL) {
580	DPRINTF0(("NULL\n"));
581	}
582	else {
583	DPRINTF0(("%p (callback = NULL)\n", (void *)handler));
584	}
585	nevents = -1; /* delete it */
586	}
587
588	update_events:
589	if (nevents >= 0) {
590	if (nevents != pollmgr.fds[i].events) {
591	DPRINTF2(("%s: fd %d ! nevents 0x%x\n",
592	__func__, fd, nevents));
593	}
594	pollmgr.fds[i].events = nevents;
595	}
596	else if (i < POLLMGR_SLOT_FIRST_DYNAMIC) {
597	/* Don't garbage-collect channels. */
598	DPRINTF2(("%s: fd %d ! DELETED (channel %d)\n",
599	__func__, fd, i));
600	pollmgr.fds[i].fd = INVALID_SOCKET;
601	pollmgr.fds[i].events = 0;
602	pollmgr.fds[i].revents = 0;
603	pollmgr.handlers[i] = NULL;
604	}
605	else {
606	DPRINTF2(("%s: fd %d ! DELETED\n", __func__, fd));
607
608	/* schedule for deletion (see g/c loop for details) */
609	pdelprev = i; / make previous entry point to us */
610	pdelprev = &pollmgr.fds[i].fd;
611
612	pollmgr.fds[i].fd = INVALID_SOCKET; /* end of list (for now) */
613	pollmgr.fds[i].events = POLLMGR_GARBAGE;
614	pollmgr.fds[i].revents = 0;
615	pollmgr.handlers[i] = NULL;
616	}
617	} /* processing loop */
618
619
620	/*
621	* Garbage collect and compact the array.
622	*
623	* We overload pollfd::fd of garbage entries to store the
624	* index of the next garbage entry. The garbage list is
625	* co-directional with the fds array. The index of the first
626	* entry is in "delfirst", the last entry "points to"
627	* INVALID_SOCKET.
628	*
629	* See update_events code for nevents < 0 at the end of the
630	* processing loop above.
631	*/
632	while (delfirst != INVALID_SOCKET) {
633	const int last = pollmgr.nfds - 1;
634
635	/*
636	* We want a live entry in the last slot to swap into the
637	* freed slot, so make sure we have one.
638	*/
639	if (pollmgr.fds[last].events == POLLMGR_GARBAGE /* garbage */
640	\|\| pollmgr.fds[last].fd == INVALID_SOCKET) /* or killed */
641	{
642	/* drop garbage entry at the end of the array */
643	--pollmgr.nfds;
644
645	if (delfirst == (SOCKET)last) {
646	/* congruent to delnext >= pollmgr.nfds test below */
647	delfirst = INVALID_SOCKET; /* done */
648	}
649	}
650	else {
651	const SOCKET delnext = pollmgr.fds[delfirst].fd;
652
653	/* copy live entry at the end to the first slot being freed */
654	pollmgr.fds[delfirst] = pollmgr.fds[last]; /* struct copy */
655	pollmgr.handlers[delfirst] = pollmgr.handlers[last];
656	pollmgr.handlers[delfirst]->slot = (int)delfirst;
657	--pollmgr.nfds;
658
659	if ((nfds_t)delnext >= pollmgr.nfds) {
660	delfirst = INVALID_SOCKET; /* done */
661	}
662	else {
663	delfirst = delnext;
664	}
665	}
666
667	pollmgr.fds[last].fd = INVALID_SOCKET;
668	pollmgr.fds[last].events = 0;
669	pollmgr.fds[last].revents = 0;
670	pollmgr.handlers[last] = NULL;
671	}
672	} /* poll loop */
673	}
674
675
676	/**
677	* Create strongly held refptr.
678	*/
679	struct pollmgr_refptr *
680	pollmgr_refptr_create(struct pollmgr_handler *ptr)
681	{
682	struct pollmgr_refptr *rp;
683
684	LWIP_ASSERT1(ptr != NULL);
685
686	rp = (struct pollmgr_refptr )malloc(sizeof (rp));
687	if (rp == NULL) {
688	return NULL;
689	}
690
691	sys_mutex_new(&rp->lock);
692	rp->ptr = ptr;
693	rp->strong = 1;
694	rp->weak = 0;
695
696	return rp;
697	}
698
699
700	static void
701	pollmgr_refptr_delete(struct pollmgr_refptr *rp)
702	{
703	if (rp == NULL) {
704	return;
705	}
706
707	LWIP_ASSERT1(rp->strong == 0);
708	LWIP_ASSERT1(rp->weak == 0);
709
710	sys_mutex_free(&rp->lock);
711	free(rp);
712	}
713
714
715	/**
716	* Add weak reference before "rp" is sent over a poll manager channel.
717	*/
718	void
719	pollmgr_refptr_weak_ref(struct pollmgr_refptr *rp)
720	{
721	sys_mutex_lock(&rp->lock);
722
723	LWIP_ASSERT1(rp->ptr != NULL);
724	LWIP_ASSERT1(rp->strong > 0);
725
726	++rp->weak;
727
728	sys_mutex_unlock(&rp->lock);
729	}
730
731
732	/**
733	* Try to get the pointer from implicitely weak reference we've got
734	* from a channel.
735	*
736	* If we detect that the object is still strongly referenced, but no
737	* longer registered with the poll manager we abort strengthening
738	* conversion here b/c lwip thread callback is already scheduled to
739	* destruct the object.
740	*/
741	struct pollmgr_handler *
742	pollmgr_refptr_get(struct pollmgr_refptr *rp)
743	{
744	struct pollmgr_handler *handler;
745	size_t weak;
746
747	sys_mutex_lock(&rp->lock);
748
749	LWIP_ASSERT1(rp->weak > 0);
750	weak = --rp->weak;
751
752	handler = rp->ptr;
753	if (handler == NULL) {
754	LWIP_ASSERT1(rp->strong == 0);
755	sys_mutex_unlock(&rp->lock);
756	if (weak == 0) {
757	pollmgr_refptr_delete(rp);
758	}
759	return NULL;
760	}
761
762	LWIP_ASSERT1(rp->strong == 1);
763
764	/*
765	* Here we woild do:
766	*
767	* ++rp->strong;
768	*
769	* and then, after channel handler is done, we would decrement it
770	* back.
771	*
772	* Instead we check that the object is still registered with poll
773	* manager. If it is, there's no race with lwip thread trying to
774	* drop its strong reference, as lwip thread callback to destruct
775	* the object is always scheduled by its poll manager callback.
776	*
777	* Conversly, if we detect that the object is no longer registered
778	* with poll manager, we immediately abort. Since channel handler
779	* can't do anything useful anyway and would have to return
780	* immediately.
781	*
782	* Since channel handler would always find rp->strong as it had
783	* left it, just elide extra strong reference creation to avoid
784	* the whole back-and-forth.
785	*/
786
787	if (handler->slot < 0) { /* no longer polling */
788	sys_mutex_unlock(&rp->lock);
789	return NULL;
790	}
791
792	sys_mutex_unlock(&rp->lock);
793	return handler;
794	}
795
796
797	/**
798	* Remove (the only) strong reference.
799	*
800	* If it were real strong/weak pointers, we should also call
801	* destructor for the referenced object, but
802	*/
803	void
804	pollmgr_refptr_unref(struct pollmgr_refptr *rp)
805	{
806	sys_mutex_lock(&rp->lock);
807
808	LWIP_ASSERT1(rp->strong == 1);
809	--rp->strong;
810
811	if (rp->strong > 0) {
812	sys_mutex_unlock(&rp->lock);
813	}
814	else {
815	size_t weak;
816
817	/* void ptr = rp->ptr; /
818	rp->ptr = NULL;
819
820	/* delete ptr; // see doc comment */
821
822	weak = rp->weak;
823	sys_mutex_unlock(&rp->lock);
824	if (weak == 0) {
825	pollmgr_refptr_delete(rp);
826	}
827	}
828	}

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source: vbox/trunk/src/VBox/NetworkServices/NAT/proxy_pollmgr.c@ 73747

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