xref: /openbmc/linux/net/rxrpc/recvmsg.c (revision 20acbd9a)
1 /* RxRPC recvmsg() implementation
2  *
3  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
4  * Written by David Howells (dhowells@redhat.com)
5  *
6  * This program is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU General Public License
8  * as published by the Free Software Foundation; either version
9  * 2 of the License, or (at your option) any later version.
10  */
11 
12 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
13 
14 #include <linux/net.h>
15 #include <linux/skbuff.h>
16 #include <linux/export.h>
17 #include <linux/sched/signal.h>
18 
19 #include <net/sock.h>
20 #include <net/af_rxrpc.h>
21 #include "ar-internal.h"
22 
23 /*
24  * Post a call for attention by the socket or kernel service.  Further
25  * notifications are suppressed by putting recvmsg_link on a dummy queue.
26  */
27 void rxrpc_notify_socket(struct rxrpc_call *call)
28 {
29 	struct rxrpc_sock *rx;
30 	struct sock *sk;
31 
32 	_enter("%d", call->debug_id);
33 
34 	if (!list_empty(&call->recvmsg_link))
35 		return;
36 
37 	rcu_read_lock();
38 
39 	rx = rcu_dereference(call->socket);
40 	sk = &rx->sk;
41 	if (rx && sk->sk_state < RXRPC_CLOSE) {
42 		if (call->notify_rx) {
43 			spin_lock_bh(&call->notify_lock);
44 			call->notify_rx(sk, call, call->user_call_ID);
45 			spin_unlock_bh(&call->notify_lock);
46 		} else {
47 			write_lock_bh(&rx->recvmsg_lock);
48 			if (list_empty(&call->recvmsg_link)) {
49 				rxrpc_get_call(call, rxrpc_call_got);
50 				list_add_tail(&call->recvmsg_link, &rx->recvmsg_q);
51 			}
52 			write_unlock_bh(&rx->recvmsg_lock);
53 
54 			if (!sock_flag(sk, SOCK_DEAD)) {
55 				_debug("call %ps", sk->sk_data_ready);
56 				sk->sk_data_ready(sk);
57 			}
58 		}
59 	}
60 
61 	rcu_read_unlock();
62 	_leave("");
63 }
64 
65 /*
66  * Pass a call terminating message to userspace.
67  */
68 static int rxrpc_recvmsg_term(struct rxrpc_call *call, struct msghdr *msg)
69 {
70 	u32 tmp = 0;
71 	int ret;
72 
73 	switch (call->completion) {
74 	case RXRPC_CALL_SUCCEEDED:
75 		ret = 0;
76 		if (rxrpc_is_service_call(call))
77 			ret = put_cmsg(msg, SOL_RXRPC, RXRPC_ACK, 0, &tmp);
78 		break;
79 	case RXRPC_CALL_REMOTELY_ABORTED:
80 		tmp = call->abort_code;
81 		ret = put_cmsg(msg, SOL_RXRPC, RXRPC_ABORT, 4, &tmp);
82 		break;
83 	case RXRPC_CALL_LOCALLY_ABORTED:
84 		tmp = call->abort_code;
85 		ret = put_cmsg(msg, SOL_RXRPC, RXRPC_ABORT, 4, &tmp);
86 		break;
87 	case RXRPC_CALL_NETWORK_ERROR:
88 		tmp = -call->error;
89 		ret = put_cmsg(msg, SOL_RXRPC, RXRPC_NET_ERROR, 4, &tmp);
90 		break;
91 	case RXRPC_CALL_LOCAL_ERROR:
92 		tmp = -call->error;
93 		ret = put_cmsg(msg, SOL_RXRPC, RXRPC_LOCAL_ERROR, 4, &tmp);
94 		break;
95 	default:
96 		pr_err("Invalid terminal call state %u\n", call->state);
97 		BUG();
98 		break;
99 	}
100 
101 	trace_rxrpc_recvmsg(call, rxrpc_recvmsg_terminal, call->rx_hard_ack,
102 			    call->rx_pkt_offset, call->rx_pkt_len, ret);
103 	return ret;
104 }
105 
106 /*
107  * Pass back notification of a new call.  The call is added to the
108  * to-be-accepted list.  This means that the next call to be accepted might not
109  * be the last call seen awaiting acceptance, but unless we leave this on the
110  * front of the queue and block all other messages until someone gives us a
111  * user_ID for it, there's not a lot we can do.
112  */
113 static int rxrpc_recvmsg_new_call(struct rxrpc_sock *rx,
114 				  struct rxrpc_call *call,
115 				  struct msghdr *msg, int flags)
116 {
117 	int tmp = 0, ret;
118 
119 	ret = put_cmsg(msg, SOL_RXRPC, RXRPC_NEW_CALL, 0, &tmp);
120 
121 	if (ret == 0 && !(flags & MSG_PEEK)) {
122 		_debug("to be accepted");
123 		write_lock_bh(&rx->recvmsg_lock);
124 		list_del_init(&call->recvmsg_link);
125 		write_unlock_bh(&rx->recvmsg_lock);
126 
127 		rxrpc_get_call(call, rxrpc_call_got);
128 		write_lock(&rx->call_lock);
129 		list_add_tail(&call->accept_link, &rx->to_be_accepted);
130 		write_unlock(&rx->call_lock);
131 	}
132 
133 	trace_rxrpc_recvmsg(call, rxrpc_recvmsg_to_be_accepted, 1, 0, 0, ret);
134 	return ret;
135 }
136 
137 /*
138  * End the packet reception phase.
139  */
140 static void rxrpc_end_rx_phase(struct rxrpc_call *call, rxrpc_serial_t serial)
141 {
142 	_enter("%d,%s", call->debug_id, rxrpc_call_states[call->state]);
143 
144 	trace_rxrpc_receive(call, rxrpc_receive_end, 0, call->rx_top);
145 	ASSERTCMP(call->rx_hard_ack, ==, call->rx_top);
146 
147 	if (call->state == RXRPC_CALL_CLIENT_RECV_REPLY) {
148 		rxrpc_propose_ACK(call, RXRPC_ACK_IDLE, 0, serial, true, false,
149 				  rxrpc_propose_ack_terminal_ack);
150 		rxrpc_send_ack_packet(call, false);
151 	}
152 
153 	write_lock_bh(&call->state_lock);
154 
155 	switch (call->state) {
156 	case RXRPC_CALL_CLIENT_RECV_REPLY:
157 		__rxrpc_call_completed(call);
158 		write_unlock_bh(&call->state_lock);
159 		break;
160 
161 	case RXRPC_CALL_SERVER_RECV_REQUEST:
162 		call->tx_phase = true;
163 		call->state = RXRPC_CALL_SERVER_ACK_REQUEST;
164 		call->ack_at = call->expire_at;
165 		write_unlock_bh(&call->state_lock);
166 		rxrpc_propose_ACK(call, RXRPC_ACK_DELAY, 0, serial, false, true,
167 				  rxrpc_propose_ack_processing_op);
168 		break;
169 	default:
170 		write_unlock_bh(&call->state_lock);
171 		break;
172 	}
173 }
174 
175 /*
176  * Discard a packet we've used up and advance the Rx window by one.
177  */
178 static void rxrpc_rotate_rx_window(struct rxrpc_call *call)
179 {
180 	struct rxrpc_skb_priv *sp;
181 	struct sk_buff *skb;
182 	rxrpc_serial_t serial;
183 	rxrpc_seq_t hard_ack, top;
184 	u8 flags;
185 	int ix;
186 
187 	_enter("%d", call->debug_id);
188 
189 	hard_ack = call->rx_hard_ack;
190 	top = smp_load_acquire(&call->rx_top);
191 	ASSERT(before(hard_ack, top));
192 
193 	hard_ack++;
194 	ix = hard_ack & RXRPC_RXTX_BUFF_MASK;
195 	skb = call->rxtx_buffer[ix];
196 	rxrpc_see_skb(skb, rxrpc_skb_rx_rotated);
197 	sp = rxrpc_skb(skb);
198 	flags = sp->hdr.flags;
199 	serial = sp->hdr.serial;
200 	if (call->rxtx_annotations[ix] & RXRPC_RX_ANNO_JUMBO)
201 		serial += (call->rxtx_annotations[ix] & RXRPC_RX_ANNO_JUMBO) - 1;
202 
203 	call->rxtx_buffer[ix] = NULL;
204 	call->rxtx_annotations[ix] = 0;
205 	/* Barrier against rxrpc_input_data(). */
206 	smp_store_release(&call->rx_hard_ack, hard_ack);
207 
208 	rxrpc_free_skb(skb, rxrpc_skb_rx_freed);
209 
210 	_debug("%u,%u,%02x", hard_ack, top, flags);
211 	trace_rxrpc_receive(call, rxrpc_receive_rotate, serial, hard_ack);
212 	if (flags & RXRPC_LAST_PACKET) {
213 		rxrpc_end_rx_phase(call, serial);
214 	} else {
215 		/* Check to see if there's an ACK that needs sending. */
216 		if (after_eq(hard_ack, call->ackr_consumed + 2) ||
217 		    after_eq(top, call->ackr_seen + 2) ||
218 		    (hard_ack == top && after(hard_ack, call->ackr_consumed)))
219 			rxrpc_propose_ACK(call, RXRPC_ACK_DELAY, 0, serial,
220 					  true, false,
221 					  rxrpc_propose_ack_rotate_rx);
222 		if (call->ackr_reason)
223 			rxrpc_send_ack_packet(call, false);
224 	}
225 }
226 
227 /*
228  * Decrypt and verify a (sub)packet.  The packet's length may be changed due to
229  * padding, but if this is the case, the packet length will be resident in the
230  * socket buffer.  Note that we can't modify the master skb info as the skb may
231  * be the home to multiple subpackets.
232  */
233 static int rxrpc_verify_packet(struct rxrpc_call *call, struct sk_buff *skb,
234 			       u8 annotation,
235 			       unsigned int offset, unsigned int len)
236 {
237 	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
238 	rxrpc_seq_t seq = sp->hdr.seq;
239 	u16 cksum = sp->hdr.cksum;
240 
241 	_enter("");
242 
243 	/* For all but the head jumbo subpacket, the security checksum is in a
244 	 * jumbo header immediately prior to the data.
245 	 */
246 	if ((annotation & RXRPC_RX_ANNO_JUMBO) > 1) {
247 		__be16 tmp;
248 		if (skb_copy_bits(skb, offset - 2, &tmp, 2) < 0)
249 			BUG();
250 		cksum = ntohs(tmp);
251 		seq += (annotation & RXRPC_RX_ANNO_JUMBO) - 1;
252 	}
253 
254 	return call->conn->security->verify_packet(call, skb, offset, len,
255 						   seq, cksum);
256 }
257 
258 /*
259  * Locate the data within a packet.  This is complicated by:
260  *
261  * (1) An skb may contain a jumbo packet - so we have to find the appropriate
262  *     subpacket.
263  *
264  * (2) The (sub)packets may be encrypted and, if so, the encrypted portion
265  *     contains an extra header which includes the true length of the data,
266  *     excluding any encrypted padding.
267  */
268 static int rxrpc_locate_data(struct rxrpc_call *call, struct sk_buff *skb,
269 			     u8 *_annotation,
270 			     unsigned int *_offset, unsigned int *_len)
271 {
272 	unsigned int offset = sizeof(struct rxrpc_wire_header);
273 	unsigned int len = *_len;
274 	int ret;
275 	u8 annotation = *_annotation;
276 
277 	/* Locate the subpacket */
278 	len = skb->len - offset;
279 	if ((annotation & RXRPC_RX_ANNO_JUMBO) > 0) {
280 		offset += (((annotation & RXRPC_RX_ANNO_JUMBO) - 1) *
281 			   RXRPC_JUMBO_SUBPKTLEN);
282 		len = (annotation & RXRPC_RX_ANNO_JLAST) ?
283 			skb->len - offset : RXRPC_JUMBO_SUBPKTLEN;
284 	}
285 
286 	if (!(annotation & RXRPC_RX_ANNO_VERIFIED)) {
287 		ret = rxrpc_verify_packet(call, skb, annotation, offset, len);
288 		if (ret < 0)
289 			return ret;
290 		*_annotation |= RXRPC_RX_ANNO_VERIFIED;
291 	}
292 
293 	*_offset = offset;
294 	*_len = len;
295 	call->conn->security->locate_data(call, skb, _offset, _len);
296 	return 0;
297 }
298 
299 /*
300  * Deliver messages to a call.  This keeps processing packets until the buffer
301  * is filled and we find either more DATA (returns 0) or the end of the DATA
302  * (returns 1).  If more packets are required, it returns -EAGAIN.
303  */
304 static int rxrpc_recvmsg_data(struct socket *sock, struct rxrpc_call *call,
305 			      struct msghdr *msg, struct iov_iter *iter,
306 			      size_t len, int flags, size_t *_offset)
307 {
308 	struct rxrpc_skb_priv *sp;
309 	struct sk_buff *skb;
310 	rxrpc_seq_t hard_ack, top, seq;
311 	size_t remain;
312 	bool last;
313 	unsigned int rx_pkt_offset, rx_pkt_len;
314 	int ix, copy, ret = -EAGAIN, ret2;
315 
316 	rx_pkt_offset = call->rx_pkt_offset;
317 	rx_pkt_len = call->rx_pkt_len;
318 
319 	if (call->state >= RXRPC_CALL_SERVER_ACK_REQUEST) {
320 		seq = call->rx_hard_ack;
321 		ret = 1;
322 		goto done;
323 	}
324 
325 	/* Barriers against rxrpc_input_data(). */
326 	hard_ack = call->rx_hard_ack;
327 	seq = hard_ack + 1;
328 	while (top = smp_load_acquire(&call->rx_top),
329 	       before_eq(seq, top)
330 	       ) {
331 		ix = seq & RXRPC_RXTX_BUFF_MASK;
332 		skb = call->rxtx_buffer[ix];
333 		if (!skb) {
334 			trace_rxrpc_recvmsg(call, rxrpc_recvmsg_hole, seq,
335 					    rx_pkt_offset, rx_pkt_len, 0);
336 			break;
337 		}
338 		smp_rmb();
339 		rxrpc_see_skb(skb, rxrpc_skb_rx_seen);
340 		sp = rxrpc_skb(skb);
341 
342 		if (!(flags & MSG_PEEK))
343 			trace_rxrpc_receive(call, rxrpc_receive_front,
344 					    sp->hdr.serial, seq);
345 
346 		if (msg)
347 			sock_recv_timestamp(msg, sock->sk, skb);
348 
349 		if (rx_pkt_offset == 0) {
350 			ret2 = rxrpc_locate_data(call, skb,
351 						 &call->rxtx_annotations[ix],
352 						 &rx_pkt_offset, &rx_pkt_len);
353 			trace_rxrpc_recvmsg(call, rxrpc_recvmsg_next, seq,
354 					    rx_pkt_offset, rx_pkt_len, ret2);
355 			if (ret2 < 0) {
356 				ret = ret2;
357 				goto out;
358 			}
359 		} else {
360 			trace_rxrpc_recvmsg(call, rxrpc_recvmsg_cont, seq,
361 					    rx_pkt_offset, rx_pkt_len, 0);
362 		}
363 
364 		/* We have to handle short, empty and used-up DATA packets. */
365 		remain = len - *_offset;
366 		copy = rx_pkt_len;
367 		if (copy > remain)
368 			copy = remain;
369 		if (copy > 0) {
370 			ret2 = skb_copy_datagram_iter(skb, rx_pkt_offset, iter,
371 						      copy);
372 			if (ret2 < 0) {
373 				ret = ret2;
374 				goto out;
375 			}
376 
377 			/* handle piecemeal consumption of data packets */
378 			rx_pkt_offset += copy;
379 			rx_pkt_len -= copy;
380 			*_offset += copy;
381 		}
382 
383 		if (rx_pkt_len > 0) {
384 			trace_rxrpc_recvmsg(call, rxrpc_recvmsg_full, seq,
385 					    rx_pkt_offset, rx_pkt_len, 0);
386 			ASSERTCMP(*_offset, ==, len);
387 			ret = 0;
388 			break;
389 		}
390 
391 		/* The whole packet has been transferred. */
392 		last = sp->hdr.flags & RXRPC_LAST_PACKET;
393 		if (!(flags & MSG_PEEK))
394 			rxrpc_rotate_rx_window(call);
395 		rx_pkt_offset = 0;
396 		rx_pkt_len = 0;
397 
398 		if (last) {
399 			ASSERTCMP(seq, ==, READ_ONCE(call->rx_top));
400 			ret = 1;
401 			goto out;
402 		}
403 
404 		seq++;
405 	}
406 
407 out:
408 	if (!(flags & MSG_PEEK)) {
409 		call->rx_pkt_offset = rx_pkt_offset;
410 		call->rx_pkt_len = rx_pkt_len;
411 	}
412 done:
413 	trace_rxrpc_recvmsg(call, rxrpc_recvmsg_data_return, seq,
414 			    rx_pkt_offset, rx_pkt_len, ret);
415 	return ret;
416 }
417 
418 /*
419  * Receive a message from an RxRPC socket
420  * - we need to be careful about two or more threads calling recvmsg
421  *   simultaneously
422  */
423 int rxrpc_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
424 		  int flags)
425 {
426 	struct rxrpc_call *call;
427 	struct rxrpc_sock *rx = rxrpc_sk(sock->sk);
428 	struct list_head *l;
429 	size_t copied = 0;
430 	long timeo;
431 	int ret;
432 
433 	DEFINE_WAIT(wait);
434 
435 	trace_rxrpc_recvmsg(NULL, rxrpc_recvmsg_enter, 0, 0, 0, 0);
436 
437 	if (flags & (MSG_OOB | MSG_TRUNC))
438 		return -EOPNOTSUPP;
439 
440 	timeo = sock_rcvtimeo(&rx->sk, flags & MSG_DONTWAIT);
441 
442 try_again:
443 	lock_sock(&rx->sk);
444 
445 	/* Return immediately if a client socket has no outstanding calls */
446 	if (RB_EMPTY_ROOT(&rx->calls) &&
447 	    list_empty(&rx->recvmsg_q) &&
448 	    rx->sk.sk_state != RXRPC_SERVER_LISTENING) {
449 		release_sock(&rx->sk);
450 		return -ENODATA;
451 	}
452 
453 	if (list_empty(&rx->recvmsg_q)) {
454 		ret = -EWOULDBLOCK;
455 		if (timeo == 0) {
456 			call = NULL;
457 			goto error_no_call;
458 		}
459 
460 		release_sock(&rx->sk);
461 
462 		/* Wait for something to happen */
463 		prepare_to_wait_exclusive(sk_sleep(&rx->sk), &wait,
464 					  TASK_INTERRUPTIBLE);
465 		ret = sock_error(&rx->sk);
466 		if (ret)
467 			goto wait_error;
468 
469 		if (list_empty(&rx->recvmsg_q)) {
470 			if (signal_pending(current))
471 				goto wait_interrupted;
472 			trace_rxrpc_recvmsg(NULL, rxrpc_recvmsg_wait,
473 					    0, 0, 0, 0);
474 			timeo = schedule_timeout(timeo);
475 		}
476 		finish_wait(sk_sleep(&rx->sk), &wait);
477 		goto try_again;
478 	}
479 
480 	/* Find the next call and dequeue it if we're not just peeking.  If we
481 	 * do dequeue it, that comes with a ref that we will need to release.
482 	 */
483 	write_lock_bh(&rx->recvmsg_lock);
484 	l = rx->recvmsg_q.next;
485 	call = list_entry(l, struct rxrpc_call, recvmsg_link);
486 	if (!(flags & MSG_PEEK))
487 		list_del_init(&call->recvmsg_link);
488 	else
489 		rxrpc_get_call(call, rxrpc_call_got);
490 	write_unlock_bh(&rx->recvmsg_lock);
491 
492 	trace_rxrpc_recvmsg(call, rxrpc_recvmsg_dequeue, 0, 0, 0, 0);
493 
494 	/* We're going to drop the socket lock, so we need to lock the call
495 	 * against interference by sendmsg.
496 	 */
497 	if (!mutex_trylock(&call->user_mutex)) {
498 		ret = -EWOULDBLOCK;
499 		if (flags & MSG_DONTWAIT)
500 			goto error_requeue_call;
501 		ret = -ERESTARTSYS;
502 		if (mutex_lock_interruptible(&call->user_mutex) < 0)
503 			goto error_requeue_call;
504 	}
505 
506 	release_sock(&rx->sk);
507 
508 	if (test_bit(RXRPC_CALL_RELEASED, &call->flags))
509 		BUG();
510 
511 	if (test_bit(RXRPC_CALL_HAS_USERID, &call->flags)) {
512 		if (flags & MSG_CMSG_COMPAT) {
513 			unsigned int id32 = call->user_call_ID;
514 
515 			ret = put_cmsg(msg, SOL_RXRPC, RXRPC_USER_CALL_ID,
516 				       sizeof(unsigned int), &id32);
517 		} else {
518 			ret = put_cmsg(msg, SOL_RXRPC, RXRPC_USER_CALL_ID,
519 				       sizeof(unsigned long),
520 				       &call->user_call_ID);
521 		}
522 		if (ret < 0)
523 			goto error_unlock_call;
524 	}
525 
526 	if (msg->msg_name) {
527 		struct sockaddr_rxrpc *srx = msg->msg_name;
528 		size_t len = sizeof(call->peer->srx);
529 
530 		memcpy(msg->msg_name, &call->peer->srx, len);
531 		srx->srx_service = call->service_id;
532 		msg->msg_namelen = len;
533 	}
534 
535 	switch (READ_ONCE(call->state)) {
536 	case RXRPC_CALL_SERVER_ACCEPTING:
537 		ret = rxrpc_recvmsg_new_call(rx, call, msg, flags);
538 		break;
539 	case RXRPC_CALL_CLIENT_RECV_REPLY:
540 	case RXRPC_CALL_SERVER_RECV_REQUEST:
541 	case RXRPC_CALL_SERVER_ACK_REQUEST:
542 		ret = rxrpc_recvmsg_data(sock, call, msg, &msg->msg_iter, len,
543 					 flags, &copied);
544 		if (ret == -EAGAIN)
545 			ret = 0;
546 
547 		if (after(call->rx_top, call->rx_hard_ack) &&
548 		    call->rxtx_buffer[(call->rx_hard_ack + 1) & RXRPC_RXTX_BUFF_MASK])
549 			rxrpc_notify_socket(call);
550 		break;
551 	default:
552 		ret = 0;
553 		break;
554 	}
555 
556 	if (ret < 0)
557 		goto error_unlock_call;
558 
559 	if (call->state == RXRPC_CALL_COMPLETE) {
560 		ret = rxrpc_recvmsg_term(call, msg);
561 		if (ret < 0)
562 			goto error_unlock_call;
563 		if (!(flags & MSG_PEEK))
564 			rxrpc_release_call(rx, call);
565 		msg->msg_flags |= MSG_EOR;
566 		ret = 1;
567 	}
568 
569 	if (ret == 0)
570 		msg->msg_flags |= MSG_MORE;
571 	else
572 		msg->msg_flags &= ~MSG_MORE;
573 	ret = copied;
574 
575 error_unlock_call:
576 	mutex_unlock(&call->user_mutex);
577 	rxrpc_put_call(call, rxrpc_call_put);
578 	trace_rxrpc_recvmsg(call, rxrpc_recvmsg_return, 0, 0, 0, ret);
579 	return ret;
580 
581 error_requeue_call:
582 	if (!(flags & MSG_PEEK)) {
583 		write_lock_bh(&rx->recvmsg_lock);
584 		list_add(&call->recvmsg_link, &rx->recvmsg_q);
585 		write_unlock_bh(&rx->recvmsg_lock);
586 		trace_rxrpc_recvmsg(call, rxrpc_recvmsg_requeue, 0, 0, 0, 0);
587 	} else {
588 		rxrpc_put_call(call, rxrpc_call_put);
589 	}
590 error_no_call:
591 	release_sock(&rx->sk);
592 	trace_rxrpc_recvmsg(call, rxrpc_recvmsg_return, 0, 0, 0, ret);
593 	return ret;
594 
595 wait_interrupted:
596 	ret = sock_intr_errno(timeo);
597 wait_error:
598 	finish_wait(sk_sleep(&rx->sk), &wait);
599 	call = NULL;
600 	goto error_no_call;
601 }
602 
603 /**
604  * rxrpc_kernel_recv_data - Allow a kernel service to receive data/info
605  * @sock: The socket that the call exists on
606  * @call: The call to send data through
607  * @buf: The buffer to receive into
608  * @size: The size of the buffer, including data already read
609  * @_offset: The running offset into the buffer.
610  * @want_more: True if more data is expected to be read
611  * @_abort: Where the abort code is stored if -ECONNABORTED is returned
612  * @_service: Where to store the actual service ID (may be upgraded)
613  *
614  * Allow a kernel service to receive data and pick up information about the
615  * state of a call.  Returns 0 if got what was asked for and there's more
616  * available, 1 if we got what was asked for and we're at the end of the data
617  * and -EAGAIN if we need more data.
618  *
619  * Note that we may return -EAGAIN to drain empty packets at the end of the
620  * data, even if we've already copied over the requested data.
621  *
622  * This function adds the amount it transfers to *_offset, so this should be
623  * precleared as appropriate.  Note that the amount remaining in the buffer is
624  * taken to be size - *_offset.
625  *
626  * *_abort should also be initialised to 0.
627  */
628 int rxrpc_kernel_recv_data(struct socket *sock, struct rxrpc_call *call,
629 			   void *buf, size_t size, size_t *_offset,
630 			   bool want_more, u32 *_abort, u16 *_service)
631 {
632 	struct iov_iter iter;
633 	struct kvec iov;
634 	int ret;
635 
636 	_enter("{%d,%s},%zu/%zu,%d",
637 	       call->debug_id, rxrpc_call_states[call->state],
638 	       *_offset, size, want_more);
639 
640 	ASSERTCMP(*_offset, <=, size);
641 	ASSERTCMP(call->state, !=, RXRPC_CALL_SERVER_ACCEPTING);
642 
643 	iov.iov_base = buf + *_offset;
644 	iov.iov_len = size - *_offset;
645 	iov_iter_kvec(&iter, ITER_KVEC | READ, &iov, 1, size - *_offset);
646 
647 	mutex_lock(&call->user_mutex);
648 
649 	switch (READ_ONCE(call->state)) {
650 	case RXRPC_CALL_CLIENT_RECV_REPLY:
651 	case RXRPC_CALL_SERVER_RECV_REQUEST:
652 	case RXRPC_CALL_SERVER_ACK_REQUEST:
653 		ret = rxrpc_recvmsg_data(sock, call, NULL, &iter, size, 0,
654 					 _offset);
655 		if (ret < 0)
656 			goto out;
657 
658 		/* We can only reach here with a partially full buffer if we
659 		 * have reached the end of the data.  We must otherwise have a
660 		 * full buffer or have been given -EAGAIN.
661 		 */
662 		if (ret == 1) {
663 			if (*_offset < size)
664 				goto short_data;
665 			if (!want_more)
666 				goto read_phase_complete;
667 			ret = 0;
668 			goto out;
669 		}
670 
671 		if (!want_more)
672 			goto excess_data;
673 		goto out;
674 
675 	case RXRPC_CALL_COMPLETE:
676 		goto call_complete;
677 
678 	default:
679 		ret = -EINPROGRESS;
680 		goto out;
681 	}
682 
683 read_phase_complete:
684 	ret = 1;
685 out:
686 	if (_service)
687 		*_service = call->service_id;
688 	mutex_unlock(&call->user_mutex);
689 	_leave(" = %d [%zu,%d]", ret, *_offset, *_abort);
690 	return ret;
691 
692 short_data:
693 	trace_rxrpc_rx_eproto(call, 0, tracepoint_string("short_data"));
694 	ret = -EBADMSG;
695 	goto out;
696 excess_data:
697 	trace_rxrpc_rx_eproto(call, 0, tracepoint_string("excess_data"));
698 	ret = -EMSGSIZE;
699 	goto out;
700 call_complete:
701 	*_abort = call->abort_code;
702 	ret = call->error;
703 	if (call->completion == RXRPC_CALL_SUCCEEDED) {
704 		ret = 1;
705 		if (size > 0)
706 			ret = -ECONNRESET;
707 	}
708 	goto out;
709 }
710 EXPORT_SYMBOL(rxrpc_kernel_recv_data);
711