net/rxrpc/sendmsg.c

/* AF_RXRPC sendmsg() implementation.
 *
 * Copyright (C) 2007, 2016 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/net.h>
#include <linux/gfp.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"

enum rxrpc_command {
	RXRPC_CMD_SEND_DATA,		/* send data message */
	RXRPC_CMD_SEND_ABORT,		/* request abort generation */
	RXRPC_CMD_ACCEPT,		/* [server] accept incoming call */
	RXRPC_CMD_REJECT_BUSY,		/* [server] reject a call as busy */
};

struct rxrpc_send_params {
	s64			tx_total_len;	/* Total Tx data length (if send data) */
	unsigned long		user_call_ID;	/* User's call ID */
	u32			abort_code;	/* Abort code to Tx (if abort) */
	enum rxrpc_command	command : 8;	/* The command to implement */
	bool			exclusive;	/* Shared or exclusive call */
	bool			upgrade;	/* If the connection is upgradeable */
};

/*
 * wait for space to appear in the transmit/ACK window
 * - caller holds the socket locked
 */
static int rxrpc_wait_for_tx_window(struct rxrpc_sock *rx,
				    struct rxrpc_call *call,
				    long *timeo)
{
	DECLARE_WAITQUEUE(myself, current);
	int ret;

	_enter(",{%u,%u,%u}",
	       call->tx_hard_ack, call->tx_top, call->tx_winsize);

	add_wait_queue(&call->waitq, &myself);

	for (;;) {
		set_current_state(TASK_INTERRUPTIBLE);
		ret = 0;
		if (call->tx_top - call->tx_hard_ack <
		    min_t(unsigned int, call->tx_winsize,
			  call->cong_cwnd + call->cong_extra))
			break;
		if (call->state >= RXRPC_CALL_COMPLETE) {
			ret = call->error;
			break;
		}
		if (signal_pending(current)) {
			ret = sock_intr_errno(*timeo);
			break;
		}

		trace_rxrpc_transmit(call, rxrpc_transmit_wait);
		mutex_unlock(&call->user_mutex);
		*timeo = schedule_timeout(*timeo);
		if (mutex_lock_interruptible(&call->user_mutex) < 0) {
			ret = sock_intr_errno(*timeo);
			break;
		}
	}

	remove_wait_queue(&call->waitq, &myself);
	set_current_state(TASK_RUNNING);
	_leave(" = %d", ret);
	return ret;
}

/*
 * Schedule an instant Tx resend.
 */
static inline void rxrpc_instant_resend(struct rxrpc_call *call, int ix)
{
	spin_lock_bh(&call->lock);

	if (call->state < RXRPC_CALL_COMPLETE) {
		call->rxtx_annotations[ix] =
			(call->rxtx_annotations[ix] & RXRPC_TX_ANNO_LAST) |
			RXRPC_TX_ANNO_RETRANS;
		if (!test_and_set_bit(RXRPC_CALL_EV_RESEND, &call->events))
			rxrpc_queue_call(call);
	}

	spin_unlock_bh(&call->lock);
}

/*
 * Notify the owner of the call that the transmit phase is ended and the last
 * packet has been queued.
 */
static void rxrpc_notify_end_tx(struct rxrpc_sock *rx, struct rxrpc_call *call,
				rxrpc_notify_end_tx_t notify_end_tx)
{
	if (notify_end_tx)
		notify_end_tx(&rx->sk, call, call->user_call_ID);
}

/*
 * Queue a DATA packet for transmission, set the resend timeout and send the
 * packet immediately
 */
static void rxrpc_queue_packet(struct rxrpc_sock *rx, struct rxrpc_call *call,
			       struct sk_buff *skb, bool last,
			       rxrpc_notify_end_tx_t notify_end_tx)
{
	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
	rxrpc_seq_t seq = sp->hdr.seq;
	int ret, ix;
	u8 annotation = RXRPC_TX_ANNO_UNACK;

	_net("queue skb %p [%d]", skb, seq);

	ASSERTCMP(seq, ==, call->tx_top + 1);

	if (last) {
		annotation |= RXRPC_TX_ANNO_LAST;
		set_bit(RXRPC_CALL_TX_LASTQ, &call->flags);
	}

	/* We have to set the timestamp before queueing as the retransmit
	 * algorithm can see the packet as soon as we queue it.
	 */
	skb->tstamp = ktime_get_real();

	ix = seq & RXRPC_RXTX_BUFF_MASK;
	rxrpc_get_skb(skb, rxrpc_skb_tx_got);
	call->rxtx_annotations[ix] = annotation;
	smp_wmb();
	call->rxtx_buffer[ix] = skb;
	call->tx_top = seq;
	if (last)
		trace_rxrpc_transmit(call, rxrpc_transmit_queue_last);
	else
		trace_rxrpc_transmit(call, rxrpc_transmit_queue);

	if (last || call->state == RXRPC_CALL_SERVER_ACK_REQUEST) {
		_debug("________awaiting reply/ACK__________");
		write_lock_bh(&call->state_lock);
		switch (call->state) {
		case RXRPC_CALL_CLIENT_SEND_REQUEST:
			call->state = RXRPC_CALL_CLIENT_AWAIT_REPLY;
			rxrpc_notify_end_tx(rx, call, notify_end_tx);
			break;
		case RXRPC_CALL_SERVER_ACK_REQUEST:
			call->state = RXRPC_CALL_SERVER_SEND_REPLY;
			call->ack_at = call->expire_at;
			if (call->ackr_reason == RXRPC_ACK_DELAY)
				call->ackr_reason = 0;
			__rxrpc_set_timer(call, rxrpc_timer_init_for_send_reply,
					  ktime_get_real());
			if (!last)
				break;
		case RXRPC_CALL_SERVER_SEND_REPLY:
			call->state = RXRPC_CALL_SERVER_AWAIT_ACK;
			rxrpc_notify_end_tx(rx, call, notify_end_tx);
			break;
		default:
			break;
		}
		write_unlock_bh(&call->state_lock);
	}

	if (seq == 1 && rxrpc_is_client_call(call))
		rxrpc_expose_client_call(call);

	ret = rxrpc_send_data_packet(call, skb, false);
	if (ret < 0) {
		_debug("need instant resend %d", ret);
		rxrpc_instant_resend(call, ix);
	} else {
		ktime_t now = ktime_get_real(), resend_at;

		resend_at = ktime_add_ms(now, rxrpc_resend_timeout);

		if (ktime_before(resend_at, call->resend_at)) {
			call->resend_at = resend_at;
			rxrpc_set_timer(call, rxrpc_timer_set_for_send, now);
		}
	}

	rxrpc_free_skb(skb, rxrpc_skb_tx_freed);
	_leave("");
}

/*
 * send data through a socket
 * - must be called in process context
 * - The caller holds the call user access mutex, but not the socket lock.
 */
static int rxrpc_send_data(struct rxrpc_sock *rx,
			   struct rxrpc_call *call,
			   struct msghdr *msg, size_t len,
			   rxrpc_notify_end_tx_t notify_end_tx)
{
	struct rxrpc_skb_priv *sp;
	struct sk_buff *skb;
	struct sock *sk = &rx->sk;
	long timeo;
	bool more;
	int ret, copied;

	timeo = sock_sndtimeo(sk, msg->msg_flags & MSG_DONTWAIT);

	/* this should be in poll */
	sk_clear_bit(SOCKWQ_ASYNC_NOSPACE, sk);

	if (sk->sk_shutdown & SEND_SHUTDOWN)
		return -EPIPE;

	more = msg->msg_flags & MSG_MORE;

	if (call->tx_total_len != -1) {
		if (len > call->tx_total_len)
			return -EMSGSIZE;
		if (!more && len != call->tx_total_len)
			return -EMSGSIZE;
	}

	skb = call->tx_pending;
	call->tx_pending = NULL;
	rxrpc_see_skb(skb, rxrpc_skb_tx_seen);

	copied = 0;
	do {
		/* Check to see if there's a ping ACK to reply to. */
		if (call->ackr_reason == RXRPC_ACK_PING_RESPONSE)
			rxrpc_send_ack_packet(call, false);

		if (!skb) {
			size_t size, chunk, max, space;

			_debug("alloc");

			if (call->tx_top - call->tx_hard_ack >=
			    min_t(unsigned int, call->tx_winsize,
				  call->cong_cwnd + call->cong_extra)) {
				ret = -EAGAIN;
				if (msg->msg_flags & MSG_DONTWAIT)
					goto maybe_error;
				ret = rxrpc_wait_for_tx_window(rx, call,
							       &timeo);
				if (ret < 0)
					goto maybe_error;
			}

			max = RXRPC_JUMBO_DATALEN;
			max -= call->conn->security_size;
			max &= ~(call->conn->size_align - 1UL);

			chunk = max;
			if (chunk > msg_data_left(msg) && !more)
				chunk = msg_data_left(msg);

			space = chunk + call->conn->size_align;
			space &= ~(call->conn->size_align - 1UL);

			size = space + call->conn->security_size;

			_debug("SIZE: %zu/%zu/%zu", chunk, space, size);

			/* create a buffer that we can retain until it's ACK'd */
			skb = sock_alloc_send_skb(
				sk, size, msg->msg_flags & MSG_DONTWAIT, &ret);
			if (!skb)
				goto maybe_error;

			rxrpc_new_skb(skb, rxrpc_skb_tx_new);

			_debug("ALLOC SEND %p", skb);

			ASSERTCMP(skb->mark, ==, 0);

			_debug("HS: %u", call->conn->security_size);
			skb_reserve(skb, call->conn->security_size);
			skb->len += call->conn->security_size;

			sp = rxrpc_skb(skb);
			sp->remain = chunk;
			if (sp->remain > skb_tailroom(skb))
				sp->remain = skb_tailroom(skb);

			_net("skb: hr %d, tr %d, hl %d, rm %d",
			       skb_headroom(skb),
			       skb_tailroom(skb),
			       skb_headlen(skb),
			       sp->remain);

			skb->ip_summed = CHECKSUM_UNNECESSARY;
		}

		_debug("append");
		sp = rxrpc_skb(skb);

		/* append next segment of data to the current buffer */
		if (msg_data_left(msg) > 0) {
			int copy = skb_tailroom(skb);
			ASSERTCMP(copy, >, 0);
			if (copy > msg_data_left(msg))
				copy = msg_data_left(msg);
			if (copy > sp->remain)
				copy = sp->remain;

			_debug("add");
			ret = skb_add_data(skb, &msg->msg_iter, copy);
			_debug("added");
			if (ret < 0)
				goto efault;
			sp->remain -= copy;
			skb->mark += copy;
			copied += copy;
			if (call->tx_total_len != -1)
				call->tx_total_len -= copy;
		}

		/* add the packet to the send queue if it's now full */
		if (sp->remain <= 0 ||
		    (msg_data_left(msg) == 0 && !more)) {
			struct rxrpc_connection *conn = call->conn;
			uint32_t seq;
			size_t pad;

			/* pad out if we're using security */
			if (conn->security_ix) {
				pad = conn->security_size + skb->mark;
				pad = conn->size_align - pad;
				pad &= conn->size_align - 1;
				_debug("pad %zu", pad);
				if (pad)
					skb_put_zero(skb, pad);
			}

			seq = call->tx_top + 1;

			sp->hdr.seq	= seq;
			sp->hdr._rsvd	= 0;
			sp->hdr.flags	= conn->out_clientflag;

			if (msg_data_left(msg) == 0 && !more)
				sp->hdr.flags |= RXRPC_LAST_PACKET;
			else if (call->tx_top - call->tx_hard_ack <
				 call->tx_winsize)
				sp->hdr.flags |= RXRPC_MORE_PACKETS;

			ret = conn->security->secure_packet(
				call, skb, skb->mark, skb->head);
			if (ret < 0)
				goto out;

			rxrpc_queue_packet(rx, call, skb,
					   !msg_data_left(msg) && !more,
					   notify_end_tx);
			skb = NULL;
		}

		/* Check for the far side aborting the call or a network error
		 * occurring.  If this happens, save any packet that was under
		 * construction so that in the case of a network error, the
		 * call can be retried or redirected.
		 */
		if (call->state == RXRPC_CALL_COMPLETE) {
			ret = call->error;
			goto out;
		}
	} while (msg_data_left(msg) > 0);

success:
	ret = copied;
	if (READ_ONCE(call->state) == RXRPC_CALL_COMPLETE) {
		read_lock_bh(&call->state_lock);
		if (call->error < 0)
			ret = call->error;
		read_unlock_bh(&call->state_lock);
	}
out:
	call->tx_pending = skb;
	_leave(" = %d", ret);
	return ret;

maybe_error:
	if (copied)
		goto success;
	goto out;

efault:
	ret = -EFAULT;
	goto out;
}

/*
 * extract control messages from the sendmsg() control buffer
 */
static int rxrpc_sendmsg_cmsg(struct msghdr *msg, struct rxrpc_send_params *p)
{
	struct cmsghdr *cmsg;
	bool got_user_ID = false;
	int len;

	if (msg->msg_controllen == 0)
		return -EINVAL;

	for_each_cmsghdr(cmsg, msg) {
		if (!CMSG_OK(msg, cmsg))
			return -EINVAL;

		len = cmsg->cmsg_len - sizeof(struct cmsghdr);
		_debug("CMSG %d, %d, %d",
		       cmsg->cmsg_level, cmsg->cmsg_type, len);

		if (cmsg->cmsg_level != SOL_RXRPC)
			continue;

		switch (cmsg->cmsg_type) {
		case RXRPC_USER_CALL_ID:
			if (msg->msg_flags & MSG_CMSG_COMPAT) {
				if (len != sizeof(u32))
					return -EINVAL;
				p->user_call_ID = *(u32 *)CMSG_DATA(cmsg);
			} else {
				if (len != sizeof(unsigned long))
					return -EINVAL;
				p->user_call_ID = *(unsigned long *)
					CMSG_DATA(cmsg);
			}
			got_user_ID = true;
			break;

		case RXRPC_ABORT:
			if (p->command != RXRPC_CMD_SEND_DATA)
				return -EINVAL;
			p->command = RXRPC_CMD_SEND_ABORT;
			if (len != sizeof(p->abort_code))
				return -EINVAL;
			p->abort_code = *(unsigned int *)CMSG_DATA(cmsg);
			if (p->abort_code == 0)
				return -EINVAL;
			break;

		case RXRPC_ACCEPT:
			if (p->command != RXRPC_CMD_SEND_DATA)
				return -EINVAL;
			p->command = RXRPC_CMD_ACCEPT;
			if (len != 0)
				return -EINVAL;
			break;

		case RXRPC_EXCLUSIVE_CALL:
			p->exclusive = true;
			if (len != 0)
				return -EINVAL;
			break;

		case RXRPC_UPGRADE_SERVICE:
			p->upgrade = true;
			if (len != 0)
				return -EINVAL;
			break;

		case RXRPC_TX_LENGTH:
			if (p->tx_total_len != -1 || len != sizeof(__s64))
				return -EINVAL;
			p->tx_total_len = *(__s64 *)CMSG_DATA(cmsg);
			if (p->tx_total_len < 0)
				return -EINVAL;
			break;

		default:
			return -EINVAL;
		}
	}

	if (!got_user_ID)
		return -EINVAL;
	if (p->tx_total_len != -1 && p->command != RXRPC_CMD_SEND_DATA)
		return -EINVAL;
	_leave(" = 0");
	return 0;
}

/*
 * Create a new client call for sendmsg().
 * - Called with the socket lock held, which it must release.
 * - If it returns a call, the call's lock will need releasing by the caller.
 */
static struct rxrpc_call *
rxrpc_new_client_call_for_sendmsg(struct rxrpc_sock *rx, struct msghdr *msg,
				  struct rxrpc_send_params *p)
	__releases(&rx->sk.sk_lock.slock)
{
	struct rxrpc_conn_parameters cp;
	struct rxrpc_call *call;
	struct key *key;

	DECLARE_SOCKADDR(struct sockaddr_rxrpc *, srx, msg->msg_name);

	_enter("");

	if (!msg->msg_name) {
		release_sock(&rx->sk);
		return ERR_PTR(-EDESTADDRREQ);
	}

	key = rx->key;
	if (key && !rx->key->payload.data[0])
		key = NULL;

	memset(&cp, 0, sizeof(cp));
	cp.local		= rx->local;
	cp.key			= rx->key;
	cp.security_level	= rx->min_sec_level;
	cp.exclusive		= rx->exclusive | p->exclusive;
	cp.upgrade		= p->upgrade;
	cp.service_id		= srx->srx_service;
	call = rxrpc_new_client_call(rx, &cp, srx, p->user_call_ID,
				     p->tx_total_len, GFP_KERNEL);
	/* The socket is now unlocked */

	_leave(" = %p\n", call);
	return call;
}

/*
 * send a message forming part of a client call through an RxRPC socket
 * - caller holds the socket locked
 * - the socket may be either a client socket or a server socket
 */
int rxrpc_do_sendmsg(struct rxrpc_sock *rx, struct msghdr *msg, size_t len)
	__releases(&rx->sk.sk_lock.slock)
{
	enum rxrpc_call_state state;
	struct rxrpc_call *call;
	int ret;

	struct rxrpc_send_params p = {
		.tx_total_len	= -1,
		.user_call_ID	= 0,
		.abort_code	= 0,
		.command	= RXRPC_CMD_SEND_DATA,
		.exclusive	= false,
		.upgrade	= true,
	};

	_enter("");

	ret = rxrpc_sendmsg_cmsg(msg, &p);
	if (ret < 0)
		goto error_release_sock;

	if (p.command == RXRPC_CMD_ACCEPT) {
		ret = -EINVAL;
		if (rx->sk.sk_state != RXRPC_SERVER_LISTENING)
			goto error_release_sock;
		call = rxrpc_accept_call(rx, p.user_call_ID, NULL);
		/* The socket is now unlocked. */
		if (IS_ERR(call))
			return PTR_ERR(call);
		ret = 0;
		goto out_put_unlock;
	}

	call = rxrpc_find_call_by_user_ID(rx, p.user_call_ID);
	if (!call) {
		ret = -EBADSLT;
		if (p.command != RXRPC_CMD_SEND_DATA)
			goto error_release_sock;
		call = rxrpc_new_client_call_for_sendmsg(rx, msg, &p);
		/* The socket is now unlocked... */
		if (IS_ERR(call))
			return PTR_ERR(call);
		/* ... and we have the call lock. */
		ret = 0;
		if (READ_ONCE(call->state) == RXRPC_CALL_COMPLETE)
			goto out_put_unlock;
	} else {
		switch (READ_ONCE(call->state)) {
		case RXRPC_CALL_UNINITIALISED:
		case RXRPC_CALL_CLIENT_AWAIT_CONN:
		case RXRPC_CALL_SERVER_PREALLOC:
		case RXRPC_CALL_SERVER_SECURING:
		case RXRPC_CALL_SERVER_ACCEPTING:
			rxrpc_put_call(call, rxrpc_call_put);
			ret = -EBUSY;
			goto error_release_sock;
		default:
			break;
		}

		ret = mutex_lock_interruptible(&call->user_mutex);
		release_sock(&rx->sk);
		if (ret < 0) {
			ret = -ERESTARTSYS;
			goto error_put;
		}

		if (p.tx_total_len != -1) {
			ret = -EINVAL;
			if (call->tx_total_len != -1 ||
			    call->tx_pending ||
			    call->tx_top != 0)
				goto error_put;
			call->tx_total_len = p.tx_total_len;
		}
	}

	state = READ_ONCE(call->state);
	_debug("CALL %d USR %lx ST %d on CONN %p",
	       call->debug_id, call->user_call_ID, state, call->conn);

	if (state >= RXRPC_CALL_COMPLETE) {
		/* it's too late for this call */
		ret = -ESHUTDOWN;
	} else if (p.command == RXRPC_CMD_SEND_ABORT) {
		ret = 0;
		if (rxrpc_abort_call("CMD", call, 0, p.abort_code, -ECONNABORTED))
			ret = rxrpc_send_abort_packet(call);
	} else if (p.command != RXRPC_CMD_SEND_DATA) {
		ret = -EINVAL;
	} else if (rxrpc_is_client_call(call) &&
		   state != RXRPC_CALL_CLIENT_SEND_REQUEST) {
		/* request phase complete for this client call */
		ret = -EPROTO;
	} else if (rxrpc_is_service_call(call) &&
		   state != RXRPC_CALL_SERVER_ACK_REQUEST &&
		   state != RXRPC_CALL_SERVER_SEND_REPLY) {
		/* Reply phase not begun or not complete for service call. */
		ret = -EPROTO;
	} else {
		ret = rxrpc_send_data(rx, call, msg, len, NULL);
	}

out_put_unlock:
	mutex_unlock(&call->user_mutex);
error_put:
	rxrpc_put_call(call, rxrpc_call_put);
	_leave(" = %d", ret);
	return ret;

error_release_sock:
	release_sock(&rx->sk);
	return ret;
}

/**
 * rxrpc_kernel_send_data - Allow a kernel service to send data on a call
 * @sock: The socket the call is on
 * @call: The call to send data through
 * @msg: The data to send
 * @len: The amount of data to send
 * @notify_end_tx: Notification that the last packet is queued.
 *
 * Allow a kernel service to send data on a call.  The call must be in an state
 * appropriate to sending data.  No control data should be supplied in @msg,
 * nor should an address be supplied.  MSG_MORE should be flagged if there's
 * more data to come, otherwise this data will end the transmission phase.
 */
int rxrpc_kernel_send_data(struct socket *sock, struct rxrpc_call *call,
			   struct msghdr *msg, size_t len,
			   rxrpc_notify_end_tx_t notify_end_tx)
{
	int ret;

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

	ASSERTCMP(msg->msg_name, ==, NULL);
	ASSERTCMP(msg->msg_control, ==, NULL);

	mutex_lock(&call->user_mutex);

	_debug("CALL %d USR %lx ST %d on CONN %p",
	       call->debug_id, call->user_call_ID, call->state, call->conn);

	switch (READ_ONCE(call->state)) {
	case RXRPC_CALL_CLIENT_SEND_REQUEST:
	case RXRPC_CALL_SERVER_ACK_REQUEST:
	case RXRPC_CALL_SERVER_SEND_REPLY:
		ret = rxrpc_send_data(rxrpc_sk(sock->sk), call, msg, len,
				      notify_end_tx);
		break;
	case RXRPC_CALL_COMPLETE:
		read_lock_bh(&call->state_lock);
		ret = call->error;
		read_unlock_bh(&call->state_lock);
		break;
	default:
		/* Request phase complete for this client call */
		trace_rxrpc_rx_eproto(call, 0, tracepoint_string("late_send"));
		ret = -EPROTO;
		break;
	}

	mutex_unlock(&call->user_mutex);
	_leave(" = %d", ret);
	return ret;
}
EXPORT_SYMBOL(rxrpc_kernel_send_data);

/**
 * rxrpc_kernel_abort_call - Allow a kernel service to abort a call
 * @sock: The socket the call is on
 * @call: The call to be aborted
 * @abort_code: The abort code to stick into the ABORT packet
 * @error: Local error value
 * @why: 3-char string indicating why.
 *
 * Allow a kernel service to abort a call, if it's still in an abortable state
 * and return true if the call was aborted, false if it was already complete.
 */
bool rxrpc_kernel_abort_call(struct socket *sock, struct rxrpc_call *call,
			     u32 abort_code, int error, const char *why)
{
	bool aborted;

	_enter("{%d},%d,%d,%s", call->debug_id, abort_code, error, why);

	mutex_lock(&call->user_mutex);

	aborted = rxrpc_abort_call(why, call, 0, abort_code, error);
	if (aborted)
		rxrpc_send_abort_packet(call);

	mutex_unlock(&call->user_mutex);
	return aborted;
}
EXPORT_SYMBOL(rxrpc_kernel_abort_call);

/**
 * rxrpc_kernel_set_tx_length - Set the total Tx length on a call
 * @sock: The socket the call is on
 * @call: The call to be informed
 * @tx_total_len: The amount of data to be transmitted for this call
 *
 * Allow a kernel service to set the total transmit length on a call.  This
 * allows buffer-to-packet encrypt-and-copy to be performed.
 *
 * This function is primarily for use for setting the reply length since the
 * request length can be set when beginning the call.
 */
void rxrpc_kernel_set_tx_length(struct socket *sock, struct rxrpc_call *call,
				s64 tx_total_len)
{
	WARN_ON(call->tx_total_len != -1);
	call->tx_total_len = tx_total_len;
}
EXPORT_SYMBOL(rxrpc_kernel_set_tx_length);