net/rxrpc/recvmsg.c - third_party/linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /* RxRPC recvmsg() implementation
  *
  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
  * Written by David Howells (dhowells@redhat.com)
  */

 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

 #include <linux/net.h>
 #include <linux/skbuff.h>
 #include <linux/export.h>
 #include <linux/sched/signal.h>

 #include <net/sock.h>
 #include <net/af_rxrpc.h>
 #include "ar-internal.h"

 /*
  * Post a call for attention by the socket or kernel service.  Further
  * notifications are suppressed by putting recvmsg_link on a dummy queue.
  */
 void rxrpc_notify_socket(struct rxrpc_call *call)
 {
 	struct rxrpc_sock *rx;
 	struct sock *sk;

 	_enter("%d", call->debug_id);

 	if (!list_empty(&call->recvmsg_link))
 		return;

 	rcu_read_lock();

 	rx = rcu_dereference(call->socket);
 	sk = &rx->sk;
 	if (rx && sk->sk_state < RXRPC_CLOSE) {
 		if (call->notify_rx) {
 			spin_lock_bh(&call->notify_lock);
 			call->notify_rx(sk, call, call->user_call_ID);
 			spin_unlock_bh(&call->notify_lock);
 		} else {
 			write_lock_bh(&rx->recvmsg_lock);
 			if (list_empty(&call->recvmsg_link)) {
 				rxrpc_get_call(call, rxrpc_call_got);
 				list_add_tail(&call->recvmsg_link, &rx->recvmsg_q);
 			}
 			write_unlock_bh(&rx->recvmsg_lock);

 			if (!sock_flag(sk, SOCK_DEAD)) {
 				_debug("call %ps", sk->sk_data_ready);
 				sk->sk_data_ready(sk);
 			}
 		}
 	}

 	rcu_read_unlock();
 	_leave("");
 }

 /*
  * Transition a call to the complete state.
  */
 bool __rxrpc_set_call_completion(struct rxrpc_call *call,
 				 enum rxrpc_call_completion compl,
 				 u32 abort_code,
 				 int error)
 {
 	if (call->state < RXRPC_CALL_COMPLETE) {
 		call->abort_code = abort_code;
 		call->error = error;
 		call->completion = compl;
 		call->state = RXRPC_CALL_COMPLETE;
 		trace_rxrpc_call_complete(call);
 		wake_up(&call->waitq);
 		rxrpc_notify_socket(call);
 		return true;
 	}
 	return false;
 }

 bool rxrpc_set_call_completion(struct rxrpc_call *call,
 			       enum rxrpc_call_completion compl,
 			       u32 abort_code,
 			       int error)
 {
 	bool ret = false;

 	if (call->state < RXRPC_CALL_COMPLETE) {
 		write_lock_bh(&call->state_lock);
 		ret = __rxrpc_set_call_completion(call, compl, abort_code, error);
 		write_unlock_bh(&call->state_lock);
 	}
 	return ret;
 }

 /*
  * Record that a call successfully completed.
  */
 bool __rxrpc_call_completed(struct rxrpc_call *call)
 {
 	return __rxrpc_set_call_completion(call, RXRPC_CALL_SUCCEEDED, 0, 0);
 }

 bool rxrpc_call_completed(struct rxrpc_call *call)
 {
 	bool ret = false;

 	if (call->state < RXRPC_CALL_COMPLETE) {
 		write_lock_bh(&call->state_lock);
 		ret = __rxrpc_call_completed(call);
 		write_unlock_bh(&call->state_lock);
 	}
 	return ret;
 }

 /*
  * Record that a call is locally aborted.
  */
 bool __rxrpc_abort_call(const char *why, struct rxrpc_call *call,
 			rxrpc_seq_t seq, u32 abort_code, int error)
 {
 	trace_rxrpc_abort(call->debug_id, why, call->cid, call->call_id, seq,
 			  abort_code, error);
 	return __rxrpc_set_call_completion(call, RXRPC_CALL_LOCALLY_ABORTED,
 					   abort_code, error);
 }

 bool rxrpc_abort_call(const char *why, struct rxrpc_call *call,
 		      rxrpc_seq_t seq, u32 abort_code, int error)
 {
 	bool ret;

 	write_lock_bh(&call->state_lock);
 	ret = __rxrpc_abort_call(why, call, seq, abort_code, error);
 	write_unlock_bh(&call->state_lock);
 	return ret;
 }

 /*
  * Pass a call terminating message to userspace.
  */
 static int rxrpc_recvmsg_term(struct rxrpc_call *call, struct msghdr *msg)
 {
 	u32 tmp = 0;
 	int ret;

 	switch (call->completion) {
 	case RXRPC_CALL_SUCCEEDED:
 		ret = 0;
 		if (rxrpc_is_service_call(call))
 			ret = put_cmsg(msg, SOL_RXRPC, RXRPC_ACK, 0, &tmp);
 		break;
 	case RXRPC_CALL_REMOTELY_ABORTED:
 		tmp = call->abort_code;
 		ret = put_cmsg(msg, SOL_RXRPC, RXRPC_ABORT, 4, &tmp);
 		break;
 	case RXRPC_CALL_LOCALLY_ABORTED:
 		tmp = call->abort_code;
 		ret = put_cmsg(msg, SOL_RXRPC, RXRPC_ABORT, 4, &tmp);
 		break;
 	case RXRPC_CALL_NETWORK_ERROR:
 		tmp = -call->error;
 		ret = put_cmsg(msg, SOL_RXRPC, RXRPC_NET_ERROR, 4, &tmp);
 		break;
 	case RXRPC_CALL_LOCAL_ERROR:
 		tmp = -call->error;
 		ret = put_cmsg(msg, SOL_RXRPC, RXRPC_LOCAL_ERROR, 4, &tmp);
 		break;
 	default:
 		pr_err("Invalid terminal call state %u\n", call->state);
 		BUG();
 		break;
 	}

 	trace_rxrpc_recvmsg(call, rxrpc_recvmsg_terminal, call->rx_hard_ack,
 			    call->rx_pkt_offset, call->rx_pkt_len, ret);
 	return ret;
 }

 /*
  * End the packet reception phase.
  */
 static void rxrpc_end_rx_phase(struct rxrpc_call *call, rxrpc_serial_t serial)
 {
 	_enter("%d,%s", call->debug_id, rxrpc_call_states[call->state]);

 	trace_rxrpc_receive(call, rxrpc_receive_end, 0, call->rx_top);
 	ASSERTCMP(call->rx_hard_ack, ==, call->rx_top);

 	if (call->state == RXRPC_CALL_CLIENT_RECV_REPLY) {
 		rxrpc_propose_ACK(call, RXRPC_ACK_IDLE, serial, false, true,
 				  rxrpc_propose_ack_terminal_ack);
 		//rxrpc_send_ack_packet(call, false, NULL);
 	}

 	write_lock_bh(&call->state_lock);

 	switch (call->state) {
 	case RXRPC_CALL_CLIENT_RECV_REPLY:
 		__rxrpc_call_completed(call);
 		write_unlock_bh(&call->state_lock);
 		break;

 	case RXRPC_CALL_SERVER_RECV_REQUEST:
 		call->tx_phase = true;
 		call->state = RXRPC_CALL_SERVER_ACK_REQUEST;
 		call->expect_req_by = jiffies + MAX_JIFFY_OFFSET;
 		write_unlock_bh(&call->state_lock);
 		rxrpc_propose_ACK(call, RXRPC_ACK_DELAY, serial, false, true,
 				  rxrpc_propose_ack_processing_op);
 		break;
 	default:
 		write_unlock_bh(&call->state_lock);
 		break;
 	}
 }

 /*
  * Discard a packet we've used up and advance the Rx window by one.
  */
 static void rxrpc_rotate_rx_window(struct rxrpc_call *call)
 {
 	struct rxrpc_skb_priv *sp;
 	struct sk_buff *skb;
 	rxrpc_serial_t serial;
 	rxrpc_seq_t hard_ack, top;
 	bool last = false;
 	u8 subpacket;
 	int ix;

 	_enter("%d", call->debug_id);

 	hard_ack = call->rx_hard_ack;
 	top = smp_load_acquire(&call->rx_top);
 	ASSERT(before(hard_ack, top));

 	hard_ack++;
 	ix = hard_ack & RXRPC_RXTX_BUFF_MASK;
 	skb = call->rxtx_buffer[ix];
 	rxrpc_see_skb(skb, rxrpc_skb_rotated);
 	sp = rxrpc_skb(skb);

 	subpacket = call->rxtx_annotations[ix] & RXRPC_RX_ANNO_SUBPACKET;
 	serial = sp->hdr.serial + subpacket;

 	if (subpacket == sp->nr_subpackets - 1 &&
 	    sp->rx_flags & RXRPC_SKB_INCL_LAST)
 		last = true;

 	call->rxtx_buffer[ix] = NULL;
 	call->rxtx_annotations[ix] = 0;
 	/* Barrier against rxrpc_input_data(). */
 	smp_store_release(&call->rx_hard_ack, hard_ack);

 	rxrpc_free_skb(skb, rxrpc_skb_freed);

 	trace_rxrpc_receive(call, rxrpc_receive_rotate, serial, hard_ack);
 	if (last) {
 		rxrpc_end_rx_phase(call, serial);
 	} else {
 		/* Check to see if there's an ACK that needs sending. */
 		if (atomic_inc_return(&call->ackr_nr_consumed) > 2)
 			rxrpc_propose_ACK(call, RXRPC_ACK_IDLE, serial,
 					  true, false,
 					  rxrpc_propose_ack_rotate_rx);
 		if (call->ackr_reason && call->ackr_reason != RXRPC_ACK_DELAY)
 			rxrpc_send_ack_packet(call, false, NULL);
 	}
 }

 /*
  * Decrypt and verify a (sub)packet.  The packet's length may be changed due to
  * padding, but if this is the case, the packet length will be resident in the
  * socket buffer.  Note that we can't modify the master skb info as the skb may
  * be the home to multiple subpackets.
  */
 static int rxrpc_verify_packet(struct rxrpc_call *call, struct sk_buff *skb,
 			       u8 annotation,
 			       unsigned int offset, unsigned int len)
 {
 	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
 	rxrpc_seq_t seq = sp->hdr.seq;
 	u16 cksum = sp->hdr.cksum;
 	u8 subpacket = annotation & RXRPC_RX_ANNO_SUBPACKET;

 	_enter("");

 	/* For all but the head jumbo subpacket, the security checksum is in a
 	 * jumbo header immediately prior to the data.
 	 */
 	if (subpacket > 0) {
 		__be16 tmp;
 		if (skb_copy_bits(skb, offset - 2, &tmp, 2) < 0)
 			BUG();
 		cksum = ntohs(tmp);
 		seq += subpacket;
 	}

 	return call->security->verify_packet(call, skb, offset, len,
 					     seq, cksum);
 }

 /*
  * Locate the data within a packet.  This is complicated by:
  *
  * (1) An skb may contain a jumbo packet - so we have to find the appropriate
  *     subpacket.
  *
  * (2) The (sub)packets may be encrypted and, if so, the encrypted portion
  *     contains an extra header which includes the true length of the data,
  *     excluding any encrypted padding.
  */
 static int rxrpc_locate_data(struct rxrpc_call *call, struct sk_buff *skb,
 			     u8 *_annotation,
 			     unsigned int *_offset, unsigned int *_len,
 			     bool *_last)
 {
 	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
 	unsigned int offset = sizeof(struct rxrpc_wire_header);
 	unsigned int len;
 	bool last = false;
 	int ret;
 	u8 annotation = *_annotation;
 	u8 subpacket = annotation & RXRPC_RX_ANNO_SUBPACKET;

 	/* Locate the subpacket */
 	offset += subpacket * RXRPC_JUMBO_SUBPKTLEN;
 	len = skb->len - offset;
 	if (subpacket < sp->nr_subpackets - 1)
 		len = RXRPC_JUMBO_DATALEN;
 	else if (sp->rx_flags & RXRPC_SKB_INCL_LAST)
 		last = true;

 	if (!(annotation & RXRPC_RX_ANNO_VERIFIED)) {
 		ret = rxrpc_verify_packet(call, skb, annotation, offset, len);
 		if (ret < 0)
 			return ret;
 		*_annotation |= RXRPC_RX_ANNO_VERIFIED;
 	}

 	*_offset = offset;
 	*_len = len;
 	*_last = last;
 	call->security->locate_data(call, skb, _offset, _len);
 	return 0;
 }

 /*
  * Deliver messages to a call.  This keeps processing packets until the buffer
  * is filled and we find either more DATA (returns 0) or the end of the DATA
  * (returns 1).  If more packets are required, it returns -EAGAIN.
  */
 static int rxrpc_recvmsg_data(struct socket *sock, struct rxrpc_call *call,
 			      struct msghdr *msg, struct iov_iter *iter,
 			      size_t len, int flags, size_t *_offset)
 {
 	struct rxrpc_skb_priv *sp;
 	struct sk_buff *skb;
 	rxrpc_serial_t serial;
 	rxrpc_seq_t hard_ack, top, seq;
 	size_t remain;
 	bool rx_pkt_last;
 	unsigned int rx_pkt_offset, rx_pkt_len;
 	int ix, copy, ret = -EAGAIN, ret2;

 	if (test_and_clear_bit(RXRPC_CALL_RX_UNDERRUN, &call->flags) &&
 	    call->ackr_reason)
 		rxrpc_send_ack_packet(call, false, NULL);

 	rx_pkt_offset = call->rx_pkt_offset;
 	rx_pkt_len = call->rx_pkt_len;
 	rx_pkt_last = call->rx_pkt_last;

 	if (call->state >= RXRPC_CALL_SERVER_ACK_REQUEST) {
 		seq = call->rx_hard_ack;
 		ret = 1;
 		goto done;
 	}

 	/* Barriers against rxrpc_input_data(). */
 	hard_ack = call->rx_hard_ack;
 	seq = hard_ack + 1;

 	while (top = smp_load_acquire(&call->rx_top),
 	       before_eq(seq, top)
 	       ) {
 		ix = seq & RXRPC_RXTX_BUFF_MASK;
 		skb = call->rxtx_buffer[ix];
 		if (!skb) {
 			trace_rxrpc_recvmsg(call, rxrpc_recvmsg_hole, seq,
 					    rx_pkt_offset, rx_pkt_len, 0);
 			break;
 		}
 		smp_rmb();
 		rxrpc_see_skb(skb, rxrpc_skb_seen);
 		sp = rxrpc_skb(skb);

 		if (!(flags & MSG_PEEK)) {
 			serial = sp->hdr.serial;
 			serial += call->rxtx_annotations[ix] & RXRPC_RX_ANNO_SUBPACKET;
 			trace_rxrpc_receive(call, rxrpc_receive_front,
 					    serial, seq);
 		}

 		if (msg)
 			sock_recv_timestamp(msg, sock->sk, skb);

 		if (rx_pkt_offset == 0) {
 			ret2 = rxrpc_locate_data(call, skb,
 						 &call->rxtx_annotations[ix],
 						 &rx_pkt_offset, &rx_pkt_len,
 						 &rx_pkt_last);
 			trace_rxrpc_recvmsg(call, rxrpc_recvmsg_next, seq,
 					    rx_pkt_offset, rx_pkt_len, ret2);
 			if (ret2 < 0) {
 				ret = ret2;
 				goto out;
 			}
 		} else {
 			trace_rxrpc_recvmsg(call, rxrpc_recvmsg_cont, seq,
 					    rx_pkt_offset, rx_pkt_len, 0);
 		}

 		/* We have to handle short, empty and used-up DATA packets. */
 		remain = len - *_offset;
 		copy = rx_pkt_len;
 		if (copy > remain)
 			copy = remain;
 		if (copy > 0) {
 			ret2 = skb_copy_datagram_iter(skb, rx_pkt_offset, iter,
 						      copy);
 			if (ret2 < 0) {
 				ret = ret2;
 				goto out;
 			}

 			/* handle piecemeal consumption of data packets */
 			rx_pkt_offset += copy;
 			rx_pkt_len -= copy;
 			*_offset += copy;
 		}

 		if (rx_pkt_len > 0) {
 			trace_rxrpc_recvmsg(call, rxrpc_recvmsg_full, seq,
 					    rx_pkt_offset, rx_pkt_len, 0);
 			ASSERTCMP(*_offset, ==, len);
 			ret = 0;
 			break;
 		}

 		/* The whole packet has been transferred. */
 		if (!(flags & MSG_PEEK))
 			rxrpc_rotate_rx_window(call);
 		rx_pkt_offset = 0;
 		rx_pkt_len = 0;

 		if (rx_pkt_last) {
 			ASSERTCMP(seq, ==, READ_ONCE(call->rx_top));
 			ret = 1;
 			goto out;
 		}

 		seq++;
 	}

 out:
 	if (!(flags & MSG_PEEK)) {
 		call->rx_pkt_offset = rx_pkt_offset;
 		call->rx_pkt_len = rx_pkt_len;
 		call->rx_pkt_last = rx_pkt_last;
 	}
 done:
 	trace_rxrpc_recvmsg(call, rxrpc_recvmsg_data_return, seq,
 			    rx_pkt_offset, rx_pkt_len, ret);
 	if (ret == -EAGAIN)
 		set_bit(RXRPC_CALL_RX_UNDERRUN, &call->flags);
 	return ret;
 }

 /*
  * Receive a message from an RxRPC socket
  * - we need to be careful about two or more threads calling recvmsg
  *   simultaneously
  */
 int rxrpc_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
 		  int flags)
 {
 	struct rxrpc_call *call;
 	struct rxrpc_sock *rx = rxrpc_sk(sock->sk);
 	struct list_head *l;
 	size_t copied = 0;
 	long timeo;
 	int ret;

 	DEFINE_WAIT(wait);

 	trace_rxrpc_recvmsg(NULL, rxrpc_recvmsg_enter, 0, 0, 0, 0);

 	if (flags & (MSG_OOB | MSG_TRUNC))
 		return -EOPNOTSUPP;

 	timeo = sock_rcvtimeo(&rx->sk, flags & MSG_DONTWAIT);

 try_again:
 	lock_sock(&rx->sk);

 	/* Return immediately if a client socket has no outstanding calls */
 	if (RB_EMPTY_ROOT(&rx->calls) &&
 	    list_empty(&rx->recvmsg_q) &&
 	    rx->sk.sk_state != RXRPC_SERVER_LISTENING) {
 		release_sock(&rx->sk);
 		return -EAGAIN;
 	}

 	if (list_empty(&rx->recvmsg_q)) {
 		ret = -EWOULDBLOCK;
 		if (timeo == 0) {
 			call = NULL;
 			goto error_no_call;
 		}

 		release_sock(&rx->sk);

 		/* Wait for something to happen */
 		prepare_to_wait_exclusive(sk_sleep(&rx->sk), &wait,
 					  TASK_INTERRUPTIBLE);
 		ret = sock_error(&rx->sk);
 		if (ret)
 			goto wait_error;

 		if (list_empty(&rx->recvmsg_q)) {
 			if (signal_pending(current))
 				goto wait_interrupted;
 			trace_rxrpc_recvmsg(NULL, rxrpc_recvmsg_wait,
 					    0, 0, 0, 0);
 			timeo = schedule_timeout(timeo);
 		}
 		finish_wait(sk_sleep(&rx->sk), &wait);
 		goto try_again;
 	}

 	/* Find the next call and dequeue it if we're not just peeking.  If we
 	 * do dequeue it, that comes with a ref that we will need to release.
 	 */
 	write_lock_bh(&rx->recvmsg_lock);
 	l = rx->recvmsg_q.next;
 	call = list_entry(l, struct rxrpc_call, recvmsg_link);
 	if (!(flags & MSG_PEEK))
 		list_del_init(&call->recvmsg_link);
 	else
 		rxrpc_get_call(call, rxrpc_call_got);
 	write_unlock_bh(&rx->recvmsg_lock);

 	trace_rxrpc_recvmsg(call, rxrpc_recvmsg_dequeue, 0, 0, 0, 0);

 	/* We're going to drop the socket lock, so we need to lock the call
 	 * against interference by sendmsg.
 	 */
 	if (!mutex_trylock(&call->user_mutex)) {
 		ret = -EWOULDBLOCK;
 		if (flags & MSG_DONTWAIT)
 			goto error_requeue_call;
 		ret = -ERESTARTSYS;
 		if (mutex_lock_interruptible(&call->user_mutex) < 0)
 			goto error_requeue_call;
 	}

 	release_sock(&rx->sk);

 	if (test_bit(RXRPC_CALL_RELEASED, &call->flags))
 		BUG();

 	if (test_bit(RXRPC_CALL_HAS_USERID, &call->flags)) {
 		if (flags & MSG_CMSG_COMPAT) {
 			unsigned int id32 = call->user_call_ID;

 			ret = put_cmsg(msg, SOL_RXRPC, RXRPC_USER_CALL_ID,
 				       sizeof(unsigned int), &id32);
 		} else {
 			unsigned long idl = call->user_call_ID;

 			ret = put_cmsg(msg, SOL_RXRPC, RXRPC_USER_CALL_ID,
 				       sizeof(unsigned long), &idl);
 		}
 		if (ret < 0)
 			goto error_unlock_call;
 	}

 	if (msg->msg_name && call->peer) {
 		struct sockaddr_rxrpc *srx = msg->msg_name;
 		size_t len = sizeof(call->peer->srx);

 		memcpy(msg->msg_name, &call->peer->srx, len);
 		srx->srx_service = call->service_id;
 		msg->msg_namelen = len;
 	}

 	switch (READ_ONCE(call->state)) {
 	case RXRPC_CALL_CLIENT_RECV_REPLY:
 	case RXRPC_CALL_SERVER_RECV_REQUEST:
 	case RXRPC_CALL_SERVER_ACK_REQUEST:
 		ret = rxrpc_recvmsg_data(sock, call, msg, &msg->msg_iter, len,
 					 flags, &copied);
 		if (ret == -EAGAIN)
 			ret = 0;

 		if (after(call->rx_top, call->rx_hard_ack) &&
 		    call->rxtx_buffer[(call->rx_hard_ack + 1) & RXRPC_RXTX_BUFF_MASK])
 			rxrpc_notify_socket(call);
 		break;
 	default:
 		ret = 0;
 		break;
 	}

 	if (ret < 0)
 		goto error_unlock_call;

 	if (call->state == RXRPC_CALL_COMPLETE) {
 		ret = rxrpc_recvmsg_term(call, msg);
 		if (ret < 0)
 			goto error_unlock_call;
 		if (!(flags & MSG_PEEK))
 			rxrpc_release_call(rx, call);
 		msg->msg_flags |= MSG_EOR;
 		ret = 1;
 	}

 	if (ret == 0)
 		msg->msg_flags |= MSG_MORE;
 	else
 		msg->msg_flags &= ~MSG_MORE;
 	ret = copied;

 error_unlock_call:
 	mutex_unlock(&call->user_mutex);
 	rxrpc_put_call(call, rxrpc_call_put);
 	trace_rxrpc_recvmsg(call, rxrpc_recvmsg_return, 0, 0, 0, ret);
 	return ret;

 error_requeue_call:
 	if (!(flags & MSG_PEEK)) {
 		write_lock_bh(&rx->recvmsg_lock);
 		list_add(&call->recvmsg_link, &rx->recvmsg_q);
 		write_unlock_bh(&rx->recvmsg_lock);
 		trace_rxrpc_recvmsg(call, rxrpc_recvmsg_requeue, 0, 0, 0, 0);
 	} else {
 		rxrpc_put_call(call, rxrpc_call_put);
 	}
 error_no_call:
 	release_sock(&rx->sk);
 error_trace:
 	trace_rxrpc_recvmsg(call, rxrpc_recvmsg_return, 0, 0, 0, ret);
 	return ret;

 wait_interrupted:
 	ret = sock_intr_errno(timeo);
 wait_error:
 	finish_wait(sk_sleep(&rx->sk), &wait);
 	call = NULL;
 	goto error_trace;
 }

 /**
  * rxrpc_kernel_recv_data - Allow a kernel service to receive data/info
  * @sock: The socket that the call exists on
  * @call: The call to send data through
  * @iter: The buffer to receive into
  * @_len: The amount of data we want to receive (decreased on return)
  * @want_more: True if more data is expected to be read
  * @_abort: Where the abort code is stored if -ECONNABORTED is returned
  * @_service: Where to store the actual service ID (may be upgraded)
  *
  * Allow a kernel service to receive data and pick up information about the
  * state of a call.  Returns 0 if got what was asked for and there's more
  * available, 1 if we got what was asked for and we're at the end of the data
  * and -EAGAIN if we need more data.
  *
  * Note that we may return -EAGAIN to drain empty packets at the end of the
  * data, even if we've already copied over the requested data.
  *
  * *_abort should also be initialised to 0.
  */
 int rxrpc_kernel_recv_data(struct socket *sock, struct rxrpc_call *call,
 			   struct iov_iter *iter, size_t *_len,
 			   bool want_more, u32 *_abort, u16 *_service)
 {
 	size_t offset = 0;
 	int ret;

 	_enter("{%d,%s},%zu,%d",
 	       call->debug_id, rxrpc_call_states[call->state],
 	       *_len, want_more);

 	ASSERTCMP(call->state, !=, RXRPC_CALL_SERVER_SECURING);

 	mutex_lock(&call->user_mutex);

 	switch (READ_ONCE(call->state)) {
 	case RXRPC_CALL_CLIENT_RECV_REPLY:
 	case RXRPC_CALL_SERVER_RECV_REQUEST:
 	case RXRPC_CALL_SERVER_ACK_REQUEST:
 		ret = rxrpc_recvmsg_data(sock, call, NULL, iter,
 					 *_len, 0, &offset);
 		*_len -= offset;
 		if (ret < 0)
 			goto out;

 		/* We can only reach here with a partially full buffer if we
 		 * have reached the end of the data.  We must otherwise have a
 		 * full buffer or have been given -EAGAIN.
 		 */
 		if (ret == 1) {
 			if (iov_iter_count(iter) > 0)
 				goto short_data;
 			if (!want_more)
 				goto read_phase_complete;
 			ret = 0;
 			goto out;
 		}

 		if (!want_more)
 			goto excess_data;
 		goto out;

 	case RXRPC_CALL_COMPLETE:
 		goto call_complete;

 	default:
 		ret = -EINPROGRESS;
 		goto out;
 	}

 read_phase_complete:
 	ret = 1;
 out:
 	switch (call->ackr_reason) {
 	case RXRPC_ACK_IDLE:
 		break;
 	case RXRPC_ACK_DELAY:
 		if (ret != -EAGAIN)
 			break;
 		fallthrough;
 	default:
 		rxrpc_send_ack_packet(call, false, NULL);
 	}

 	if (_service)
 		*_service = call->service_id;
 	mutex_unlock(&call->user_mutex);
 	_leave(" = %d [%zu,%d]", ret, iov_iter_count(iter), *_abort);
 	return ret;

 short_data:
 	trace_rxrpc_rx_eproto(call, 0, tracepoint_string("short_data"));
 	ret = -EBADMSG;
 	goto out;
 excess_data:
 	trace_rxrpc_rx_eproto(call, 0, tracepoint_string("excess_data"));
 	ret = -EMSGSIZE;
 	goto out;
 call_complete:
 	*_abort = call->abort_code;
 	ret = call->error;
 	if (call->completion == RXRPC_CALL_SUCCEEDED) {
 		ret = 1;
 		if (iov_iter_count(iter) > 0)
 			ret = -ECONNRESET;
 	}
 	goto out;
 }
 EXPORT_SYMBOL(rxrpc_kernel_recv_data);
	// SPDX-License-Identifier: GPL-2.0-or-later
	/* RxRPC recvmsg() implementation
	*
	* Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
	* Written by David Howells (dhowells@redhat.com)
	*/

	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

	#include <linux/net.h>
	#include <linux/skbuff.h>
	#include <linux/export.h>
	#include <linux/sched/signal.h>

	#include <net/sock.h>
	#include <net/af_rxrpc.h>
	#include "ar-internal.h"

	/*
	* Post a call for attention by the socket or kernel service. Further
	* notifications are suppressed by putting recvmsg_link on a dummy queue.
	*/
	void rxrpc_notify_socket(struct rxrpc_call *call)
	{
	struct rxrpc_sock *rx;
	struct sock *sk;

	_enter("%d", call->debug_id);

	if (!list_empty(&call->recvmsg_link))
	return;

	rcu_read_lock();

	rx = rcu_dereference(call->socket);
	sk = &rx->sk;
	if (rx && sk->sk_state < RXRPC_CLOSE) {
	if (call->notify_rx) {
	spin_lock_bh(&call->notify_lock);
	call->notify_rx(sk, call, call->user_call_ID);
	spin_unlock_bh(&call->notify_lock);
	} else {
	write_lock_bh(&rx->recvmsg_lock);
	if (list_empty(&call->recvmsg_link)) {
	rxrpc_get_call(call, rxrpc_call_got);
	list_add_tail(&call->recvmsg_link, &rx->recvmsg_q);
	}
	write_unlock_bh(&rx->recvmsg_lock);

	if (!sock_flag(sk, SOCK_DEAD)) {
	_debug("call %ps", sk->sk_data_ready);
	sk->sk_data_ready(sk);
	}
	}
	}

	rcu_read_unlock();
	_leave("");
	}

	/*
	* Transition a call to the complete state.
	*/
	bool __rxrpc_set_call_completion(struct rxrpc_call *call,
	enum rxrpc_call_completion compl,
	u32 abort_code,
	int error)
	{
	if (call->state < RXRPC_CALL_COMPLETE) {
	call->abort_code = abort_code;
	call->error = error;
	call->completion = compl;
	call->state = RXRPC_CALL_COMPLETE;
	trace_rxrpc_call_complete(call);
	wake_up(&call->waitq);
	rxrpc_notify_socket(call);
	return true;
	}
	return false;
	}

	bool rxrpc_set_call_completion(struct rxrpc_call *call,
	enum rxrpc_call_completion compl,
	u32 abort_code,
	int error)
	{
	bool ret = false;

	if (call->state < RXRPC_CALL_COMPLETE) {
	write_lock_bh(&call->state_lock);
	ret = __rxrpc_set_call_completion(call, compl, abort_code, error);
	write_unlock_bh(&call->state_lock);
	}
	return ret;
	}

	/*
	* Record that a call successfully completed.
	*/
	bool __rxrpc_call_completed(struct rxrpc_call *call)
	{
	return __rxrpc_set_call_completion(call, RXRPC_CALL_SUCCEEDED, 0, 0);
	}

	bool rxrpc_call_completed(struct rxrpc_call *call)
	{
	bool ret = false;

	if (call->state < RXRPC_CALL_COMPLETE) {
	write_lock_bh(&call->state_lock);
	ret = __rxrpc_call_completed(call);
	write_unlock_bh(&call->state_lock);
	}
	return ret;
	}

	/*
	* Record that a call is locally aborted.
	*/
	bool __rxrpc_abort_call(const char why, struct rxrpc_call call,
	rxrpc_seq_t seq, u32 abort_code, int error)
	{
	trace_rxrpc_abort(call->debug_id, why, call->cid, call->call_id, seq,
	abort_code, error);
	return __rxrpc_set_call_completion(call, RXRPC_CALL_LOCALLY_ABORTED,
	abort_code, error);
	}

	bool rxrpc_abort_call(const char why, struct rxrpc_call call,
	rxrpc_seq_t seq, u32 abort_code, int error)
	{
	bool ret;

	write_lock_bh(&call->state_lock);
	ret = __rxrpc_abort_call(why, call, seq, abort_code, error);
	write_unlock_bh(&call->state_lock);
	return ret;
	}

	/*
	* Pass a call terminating message to userspace.
	*/
	static int rxrpc_recvmsg_term(struct rxrpc_call call, struct msghdr msg)
	{
	u32 tmp = 0;
	int ret;

	switch (call->completion) {
	case RXRPC_CALL_SUCCEEDED:
	ret = 0;
	if (rxrpc_is_service_call(call))
	ret = put_cmsg(msg, SOL_RXRPC, RXRPC_ACK, 0, &tmp);
	break;
	case RXRPC_CALL_REMOTELY_ABORTED:
	tmp = call->abort_code;
	ret = put_cmsg(msg, SOL_RXRPC, RXRPC_ABORT, 4, &tmp);
	break;
	case RXRPC_CALL_LOCALLY_ABORTED:
	tmp = call->abort_code;
	ret = put_cmsg(msg, SOL_RXRPC, RXRPC_ABORT, 4, &tmp);
	break;
	case RXRPC_CALL_NETWORK_ERROR:
	tmp = -call->error;
	ret = put_cmsg(msg, SOL_RXRPC, RXRPC_NET_ERROR, 4, &tmp);
	break;
	case RXRPC_CALL_LOCAL_ERROR:
	tmp = -call->error;
	ret = put_cmsg(msg, SOL_RXRPC, RXRPC_LOCAL_ERROR, 4, &tmp);
	break;
	default:
	pr_err("Invalid terminal call state %u\n", call->state);
	BUG();
	break;
	}

	trace_rxrpc_recvmsg(call, rxrpc_recvmsg_terminal, call->rx_hard_ack,
	call->rx_pkt_offset, call->rx_pkt_len, ret);
	return ret;
	}

	/*
	* End the packet reception phase.
	*/
	static void rxrpc_end_rx_phase(struct rxrpc_call *call, rxrpc_serial_t serial)
	{
	_enter("%d,%s", call->debug_id, rxrpc_call_states[call->state]);

	trace_rxrpc_receive(call, rxrpc_receive_end, 0, call->rx_top);
	ASSERTCMP(call->rx_hard_ack, ==, call->rx_top);

	if (call->state == RXRPC_CALL_CLIENT_RECV_REPLY) {
	rxrpc_propose_ACK(call, RXRPC_ACK_IDLE, serial, false, true,
	rxrpc_propose_ack_terminal_ack);
	//rxrpc_send_ack_packet(call, false, NULL);
	}

	write_lock_bh(&call->state_lock);

	switch (call->state) {
	case RXRPC_CALL_CLIENT_RECV_REPLY:
	__rxrpc_call_completed(call);
	write_unlock_bh(&call->state_lock);
	break;

	case RXRPC_CALL_SERVER_RECV_REQUEST:
	call->tx_phase = true;
	call->state = RXRPC_CALL_SERVER_ACK_REQUEST;
	call->expect_req_by = jiffies + MAX_JIFFY_OFFSET;
	write_unlock_bh(&call->state_lock);
	rxrpc_propose_ACK(call, RXRPC_ACK_DELAY, serial, false, true,
	rxrpc_propose_ack_processing_op);
	break;
	default:
	write_unlock_bh(&call->state_lock);
	break;
	}
	}

	/*
	* Discard a packet we've used up and advance the Rx window by one.
	*/
	static void rxrpc_rotate_rx_window(struct rxrpc_call *call)
	{
	struct rxrpc_skb_priv *sp;
	struct sk_buff *skb;
	rxrpc_serial_t serial;
	rxrpc_seq_t hard_ack, top;
	bool last = false;
	u8 subpacket;
	int ix;

	_enter("%d", call->debug_id);

	hard_ack = call->rx_hard_ack;
	top = smp_load_acquire(&call->rx_top);
	ASSERT(before(hard_ack, top));

	hard_ack++;
	ix = hard_ack & RXRPC_RXTX_BUFF_MASK;
	skb = call->rxtx_buffer[ix];
	rxrpc_see_skb(skb, rxrpc_skb_rotated);
	sp = rxrpc_skb(skb);

	subpacket = call->rxtx_annotations[ix] & RXRPC_RX_ANNO_SUBPACKET;
	serial = sp->hdr.serial + subpacket;

	if (subpacket == sp->nr_subpackets - 1 &&
	sp->rx_flags & RXRPC_SKB_INCL_LAST)
	last = true;

	call->rxtx_buffer[ix] = NULL;
	call->rxtx_annotations[ix] = 0;
	/* Barrier against rxrpc_input_data(). */
	smp_store_release(&call->rx_hard_ack, hard_ack);

	rxrpc_free_skb(skb, rxrpc_skb_freed);

	trace_rxrpc_receive(call, rxrpc_receive_rotate, serial, hard_ack);
	if (last) {
	rxrpc_end_rx_phase(call, serial);
	} else {
	/* Check to see if there's an ACK that needs sending. */
	if (atomic_inc_return(&call->ackr_nr_consumed) > 2)
	rxrpc_propose_ACK(call, RXRPC_ACK_IDLE, serial,
	true, false,
	rxrpc_propose_ack_rotate_rx);
	if (call->ackr_reason && call->ackr_reason != RXRPC_ACK_DELAY)
	rxrpc_send_ack_packet(call, false, NULL);
	}
	}

	/*
	* Decrypt and verify a (sub)packet. The packet's length may be changed due to
	* padding, but if this is the case, the packet length will be resident in the
	* socket buffer. Note that we can't modify the master skb info as the skb may
	* be the home to multiple subpackets.
	*/
	static int rxrpc_verify_packet(struct rxrpc_call call, struct sk_buff skb,
	u8 annotation,
	unsigned int offset, unsigned int len)
	{
	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
	rxrpc_seq_t seq = sp->hdr.seq;
	u16 cksum = sp->hdr.cksum;
	u8 subpacket = annotation & RXRPC_RX_ANNO_SUBPACKET;

	_enter("");

	/* For all but the head jumbo subpacket, the security checksum is in a
	* jumbo header immediately prior to the data.
	*/
	if (subpacket > 0) {
	__be16 tmp;
	if (skb_copy_bits(skb, offset - 2, &tmp, 2) < 0)
	BUG();
	cksum = ntohs(tmp);
	seq += subpacket;
	}

	return call->security->verify_packet(call, skb, offset, len,
	seq, cksum);
	}

	/*
	* Locate the data within a packet. This is complicated by:
	*
	* (1) An skb may contain a jumbo packet - so we have to find the appropriate
	* subpacket.
	*
	* (2) The (sub)packets may be encrypted and, if so, the encrypted portion
	* contains an extra header which includes the true length of the data,
	* excluding any encrypted padding.
	*/
	static int rxrpc_locate_data(struct rxrpc_call call, struct sk_buff skb,
	u8 *_annotation,
	unsigned int _offset, unsigned int _len,
	bool *_last)
	{
	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
	unsigned int offset = sizeof(struct rxrpc_wire_header);
	unsigned int len;
	bool last = false;
	int ret;
	u8 annotation = *_annotation;
	u8 subpacket = annotation & RXRPC_RX_ANNO_SUBPACKET;

	/* Locate the subpacket */
	offset += subpacket * RXRPC_JUMBO_SUBPKTLEN;
	len = skb->len - offset;
	if (subpacket < sp->nr_subpackets - 1)
	len = RXRPC_JUMBO_DATALEN;
	else if (sp->rx_flags & RXRPC_SKB_INCL_LAST)
	last = true;

	if (!(annotation & RXRPC_RX_ANNO_VERIFIED)) {
	ret = rxrpc_verify_packet(call, skb, annotation, offset, len);
	if (ret < 0)
	return ret;
	*_annotation \|= RXRPC_RX_ANNO_VERIFIED;
	}

	*_offset = offset;
	*_len = len;
	*_last = last;
	call->security->locate_data(call, skb, _offset, _len);
	return 0;
	}

	/*
	* Deliver messages to a call. This keeps processing packets until the buffer
	* is filled and we find either more DATA (returns 0) or the end of the DATA
	* (returns 1). If more packets are required, it returns -EAGAIN.
	*/
	static int rxrpc_recvmsg_data(struct socket sock, struct rxrpc_call call,
	struct msghdr msg, struct iov_iter iter,
	size_t len, int flags, size_t *_offset)
	{
	struct rxrpc_skb_priv *sp;
	struct sk_buff *skb;
	rxrpc_serial_t serial;
	rxrpc_seq_t hard_ack, top, seq;
	size_t remain;
	bool rx_pkt_last;
	unsigned int rx_pkt_offset, rx_pkt_len;
	int ix, copy, ret = -EAGAIN, ret2;

	if (test_and_clear_bit(RXRPC_CALL_RX_UNDERRUN, &call->flags) &&
	call->ackr_reason)
	rxrpc_send_ack_packet(call, false, NULL);

	rx_pkt_offset = call->rx_pkt_offset;
	rx_pkt_len = call->rx_pkt_len;
	rx_pkt_last = call->rx_pkt_last;

	if (call->state >= RXRPC_CALL_SERVER_ACK_REQUEST) {
	seq = call->rx_hard_ack;
	ret = 1;
	goto done;
	}

	/* Barriers against rxrpc_input_data(). */
	hard_ack = call->rx_hard_ack;
	seq = hard_ack + 1;

	while (top = smp_load_acquire(&call->rx_top),
	before_eq(seq, top)
	) {
	ix = seq & RXRPC_RXTX_BUFF_MASK;
	skb = call->rxtx_buffer[ix];
	if (!skb) {
	trace_rxrpc_recvmsg(call, rxrpc_recvmsg_hole, seq,
	rx_pkt_offset, rx_pkt_len, 0);
	break;
	}
	smp_rmb();
	rxrpc_see_skb(skb, rxrpc_skb_seen);
	sp = rxrpc_skb(skb);

	if (!(flags & MSG_PEEK)) {
	serial = sp->hdr.serial;
	serial += call->rxtx_annotations[ix] & RXRPC_RX_ANNO_SUBPACKET;
	trace_rxrpc_receive(call, rxrpc_receive_front,
	serial, seq);
	}

	if (msg)
	sock_recv_timestamp(msg, sock->sk, skb);

	if (rx_pkt_offset == 0) {
	ret2 = rxrpc_locate_data(call, skb,
	&call->rxtx_annotations[ix],
	&rx_pkt_offset, &rx_pkt_len,
	&rx_pkt_last);
	trace_rxrpc_recvmsg(call, rxrpc_recvmsg_next, seq,
	rx_pkt_offset, rx_pkt_len, ret2);
	if (ret2 < 0) {
	ret = ret2;
	goto out;
	}
	} else {
	trace_rxrpc_recvmsg(call, rxrpc_recvmsg_cont, seq,
	rx_pkt_offset, rx_pkt_len, 0);
	}

	/* We have to handle short, empty and used-up DATA packets. */
	remain = len - *_offset;
	copy = rx_pkt_len;
	if (copy > remain)
	copy = remain;
	if (copy > 0) {
	ret2 = skb_copy_datagram_iter(skb, rx_pkt_offset, iter,
	copy);
	if (ret2 < 0) {
	ret = ret2;
	goto out;
	}

	/* handle piecemeal consumption of data packets */
	rx_pkt_offset += copy;
	rx_pkt_len -= copy;
	*_offset += copy;
	}

	if (rx_pkt_len > 0) {
	trace_rxrpc_recvmsg(call, rxrpc_recvmsg_full, seq,
	rx_pkt_offset, rx_pkt_len, 0);
	ASSERTCMP(*_offset, ==, len);
	ret = 0;
	break;
	}

	/* The whole packet has been transferred. */
	if (!(flags & MSG_PEEK))
	rxrpc_rotate_rx_window(call);
	rx_pkt_offset = 0;
	rx_pkt_len = 0;

	if (rx_pkt_last) {
	ASSERTCMP(seq, ==, READ_ONCE(call->rx_top));
	ret = 1;
	goto out;
	}

	seq++;
	}

	out:
	if (!(flags & MSG_PEEK)) {
	call->rx_pkt_offset = rx_pkt_offset;
	call->rx_pkt_len = rx_pkt_len;
	call->rx_pkt_last = rx_pkt_last;
	}
	done:
	trace_rxrpc_recvmsg(call, rxrpc_recvmsg_data_return, seq,
	rx_pkt_offset, rx_pkt_len, ret);
	if (ret == -EAGAIN)
	set_bit(RXRPC_CALL_RX_UNDERRUN, &call->flags);
	return ret;
	}

	/*
	* Receive a message from an RxRPC socket
	* - we need to be careful about two or more threads calling recvmsg
	* simultaneously
	*/
	int rxrpc_recvmsg(struct socket sock, struct msghdr msg, size_t len,
	int flags)
	{
	struct rxrpc_call *call;
	struct rxrpc_sock *rx = rxrpc_sk(sock->sk);
	struct list_head *l;
	size_t copied = 0;
	long timeo;
	int ret;

	DEFINE_WAIT(wait);

	trace_rxrpc_recvmsg(NULL, rxrpc_recvmsg_enter, 0, 0, 0, 0);

	if (flags & (MSG_OOB \| MSG_TRUNC))
	return -EOPNOTSUPP;

	timeo = sock_rcvtimeo(&rx->sk, flags & MSG_DONTWAIT);

	try_again:
	lock_sock(&rx->sk);

	/* Return immediately if a client socket has no outstanding calls */
	if (RB_EMPTY_ROOT(&rx->calls) &&
	list_empty(&rx->recvmsg_q) &&
	rx->sk.sk_state != RXRPC_SERVER_LISTENING) {
	release_sock(&rx->sk);
	return -EAGAIN;
	}

	if (list_empty(&rx->recvmsg_q)) {
	ret = -EWOULDBLOCK;
	if (timeo == 0) {
	call = NULL;
	goto error_no_call;
	}

	release_sock(&rx->sk);

	/* Wait for something to happen */
	prepare_to_wait_exclusive(sk_sleep(&rx->sk), &wait,
	TASK_INTERRUPTIBLE);
	ret = sock_error(&rx->sk);
	if (ret)
	goto wait_error;

	if (list_empty(&rx->recvmsg_q)) {
	if (signal_pending(current))
	goto wait_interrupted;
	trace_rxrpc_recvmsg(NULL, rxrpc_recvmsg_wait,
	0, 0, 0, 0);
	timeo = schedule_timeout(timeo);
	}
	finish_wait(sk_sleep(&rx->sk), &wait);
	goto try_again;
	}

	/* Find the next call and dequeue it if we're not just peeking. If we
	* do dequeue it, that comes with a ref that we will need to release.
	*/
	write_lock_bh(&rx->recvmsg_lock);
	l = rx->recvmsg_q.next;
	call = list_entry(l, struct rxrpc_call, recvmsg_link);
	if (!(flags & MSG_PEEK))
	list_del_init(&call->recvmsg_link);
	else
	rxrpc_get_call(call, rxrpc_call_got);
	write_unlock_bh(&rx->recvmsg_lock);

	trace_rxrpc_recvmsg(call, rxrpc_recvmsg_dequeue, 0, 0, 0, 0);

	/* We're going to drop the socket lock, so we need to lock the call
	* against interference by sendmsg.
	*/
	if (!mutex_trylock(&call->user_mutex)) {
	ret = -EWOULDBLOCK;
	if (flags & MSG_DONTWAIT)
	goto error_requeue_call;
	ret = -ERESTARTSYS;
	if (mutex_lock_interruptible(&call->user_mutex) < 0)
	goto error_requeue_call;
	}

	release_sock(&rx->sk);

	if (test_bit(RXRPC_CALL_RELEASED, &call->flags))
	BUG();

	if (test_bit(RXRPC_CALL_HAS_USERID, &call->flags)) {
	if (flags & MSG_CMSG_COMPAT) {
	unsigned int id32 = call->user_call_ID;

	ret = put_cmsg(msg, SOL_RXRPC, RXRPC_USER_CALL_ID,
	sizeof(unsigned int), &id32);
	} else {
	unsigned long idl = call->user_call_ID;

	ret = put_cmsg(msg, SOL_RXRPC, RXRPC_USER_CALL_ID,
	sizeof(unsigned long), &idl);
	}
	if (ret < 0)
	goto error_unlock_call;
	}

	if (msg->msg_name && call->peer) {
	struct sockaddr_rxrpc *srx = msg->msg_name;
	size_t len = sizeof(call->peer->srx);

	memcpy(msg->msg_name, &call->peer->srx, len);
	srx->srx_service = call->service_id;
	msg->msg_namelen = len;
	}

	switch (READ_ONCE(call->state)) {
	case RXRPC_CALL_CLIENT_RECV_REPLY:
	case RXRPC_CALL_SERVER_RECV_REQUEST:
	case RXRPC_CALL_SERVER_ACK_REQUEST:
	ret = rxrpc_recvmsg_data(sock, call, msg, &msg->msg_iter, len,
	flags, &copied);
	if (ret == -EAGAIN)
	ret = 0;

	if (after(call->rx_top, call->rx_hard_ack) &&
	call->rxtx_buffer[(call->rx_hard_ack + 1) & RXRPC_RXTX_BUFF_MASK])
	rxrpc_notify_socket(call);
	break;
	default:
	ret = 0;
	break;
	}

	if (ret < 0)
	goto error_unlock_call;

	if (call->state == RXRPC_CALL_COMPLETE) {
	ret = rxrpc_recvmsg_term(call, msg);
	if (ret < 0)
	goto error_unlock_call;
	if (!(flags & MSG_PEEK))
	rxrpc_release_call(rx, call);
	msg->msg_flags \|= MSG_EOR;
	ret = 1;
	}

	if (ret == 0)
	msg->msg_flags \|= MSG_MORE;
	else
	msg->msg_flags &= ~MSG_MORE;
	ret = copied;

	error_unlock_call:
	mutex_unlock(&call->user_mutex);
	rxrpc_put_call(call, rxrpc_call_put);
	trace_rxrpc_recvmsg(call, rxrpc_recvmsg_return, 0, 0, 0, ret);
	return ret;

	error_requeue_call:
	if (!(flags & MSG_PEEK)) {
	write_lock_bh(&rx->recvmsg_lock);
	list_add(&call->recvmsg_link, &rx->recvmsg_q);
	write_unlock_bh(&rx->recvmsg_lock);
	trace_rxrpc_recvmsg(call, rxrpc_recvmsg_requeue, 0, 0, 0, 0);
	} else {
	rxrpc_put_call(call, rxrpc_call_put);
	}
	error_no_call:
	release_sock(&rx->sk);
	error_trace:
	trace_rxrpc_recvmsg(call, rxrpc_recvmsg_return, 0, 0, 0, ret);
	return ret;

	wait_interrupted:
	ret = sock_intr_errno(timeo);
	wait_error:
	finish_wait(sk_sleep(&rx->sk), &wait);
	call = NULL;
	goto error_trace;
	}

	/**
	* rxrpc_kernel_recv_data - Allow a kernel service to receive data/info
	* @sock: The socket that the call exists on
	* @call: The call to send data through
	* @iter: The buffer to receive into
	* @_len: The amount of data we want to receive (decreased on return)
	* @want_more: True if more data is expected to be read
	* @_abort: Where the abort code is stored if -ECONNABORTED is returned
	* @_service: Where to store the actual service ID (may be upgraded)
	*
	* Allow a kernel service to receive data and pick up information about the
	* state of a call. Returns 0 if got what was asked for and there's more
	* available, 1 if we got what was asked for and we're at the end of the data
	* and -EAGAIN if we need more data.
	*
	* Note that we may return -EAGAIN to drain empty packets at the end of the
	* data, even if we've already copied over the requested data.
	*
	* *_abort should also be initialised to 0.
	*/
	int rxrpc_kernel_recv_data(struct socket sock, struct rxrpc_call call,
	struct iov_iter iter, size_t _len,
	bool want_more, u32 _abort, u16 _service)
	{
	size_t offset = 0;
	int ret;

	_enter("{%d,%s},%zu,%d",
	call->debug_id, rxrpc_call_states[call->state],
	*_len, want_more);

	ASSERTCMP(call->state, !=, RXRPC_CALL_SERVER_SECURING);

	mutex_lock(&call->user_mutex);

	switch (READ_ONCE(call->state)) {
	case RXRPC_CALL_CLIENT_RECV_REPLY:
	case RXRPC_CALL_SERVER_RECV_REQUEST:
	case RXRPC_CALL_SERVER_ACK_REQUEST:
	ret = rxrpc_recvmsg_data(sock, call, NULL, iter,
	*_len, 0, &offset);
	*_len -= offset;
	if (ret < 0)
	goto out;

	/* We can only reach here with a partially full buffer if we
	* have reached the end of the data. We must otherwise have a
	* full buffer or have been given -EAGAIN.
	*/
	if (ret == 1) {
	if (iov_iter_count(iter) > 0)
	goto short_data;
	if (!want_more)
	goto read_phase_complete;
	ret = 0;
	goto out;
	}

	if (!want_more)
	goto excess_data;
	goto out;

	case RXRPC_CALL_COMPLETE:
	goto call_complete;

	default:
	ret = -EINPROGRESS;
	goto out;
	}

	read_phase_complete:
	ret = 1;
	out:
	switch (call->ackr_reason) {
	case RXRPC_ACK_IDLE:
	break;
	case RXRPC_ACK_DELAY:
	if (ret != -EAGAIN)
	break;
	fallthrough;
	default:
	rxrpc_send_ack_packet(call, false, NULL);
	}

	if (_service)
	*_service = call->service_id;
	mutex_unlock(&call->user_mutex);
	_leave(" = %d [%zu,%d]", ret, iov_iter_count(iter), *_abort);
	return ret;

	short_data:
	trace_rxrpc_rx_eproto(call, 0, tracepoint_string("short_data"));
	ret = -EBADMSG;
	goto out;
	excess_data:
	trace_rxrpc_rx_eproto(call, 0, tracepoint_string("excess_data"));
	ret = -EMSGSIZE;
	goto out;
	call_complete:
	*_abort = call->abort_code;
	ret = call->error;
	if (call->completion == RXRPC_CALL_SUCCEEDED) {
	ret = 1;
	if (iov_iter_count(iter) > 0)
	ret = -ECONNRESET;
	}
	goto out;
	}
	EXPORT_SYMBOL(rxrpc_kernel_recv_data);