src/kernel/linux/v4.19/net/rxrpc/output.c - T800 - Gitiles

 /* RxRPC packet transmission
  *
  * Copyright (C) 2007 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 License
  * as published by the Free Software Foundation; either version
  * 2 of the License, 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 <net/sock.h>
 #include <net/af_rxrpc.h>
 #include "ar-internal.h"

 struct rxrpc_ack_buffer {
 	struct rxrpc_wire_header whdr;
 	struct rxrpc_ackpacket ack;
 	u8 acks[255];
 	u8 pad[3];
 	struct rxrpc_ackinfo ackinfo;
 };

 struct rxrpc_abort_buffer {
 	struct rxrpc_wire_header whdr;
 	__be32 abort_code;
 };

 static const char rxrpc_keepalive_string[] = "";

 /*
  * Increase Tx backoff on transmission failure and clear it on success.
  */
 static void rxrpc_tx_backoff(struct rxrpc_call *call, int ret)
 {
 	if (ret < 0) {
 		u16 tx_backoff = READ_ONCE(call->tx_backoff);

 		if (tx_backoff < HZ)
 			WRITE_ONCE(call->tx_backoff, tx_backoff + 1);
 	} else {
 		WRITE_ONCE(call->tx_backoff, 0);
 	}
 }

 /*
  * Arrange for a keepalive ping a certain time after we last transmitted.  This
  * lets the far side know we're still interested in this call and helps keep
  * the route through any intervening firewall open.
  *
  * Receiving a response to the ping will prevent the ->expect_rx_by timer from
  * expiring.
  */
 static void rxrpc_set_keepalive(struct rxrpc_call *call)
 {
 	unsigned long now = jiffies, keepalive_at = call->next_rx_timo / 6;

 	keepalive_at += now;
 	WRITE_ONCE(call->keepalive_at, keepalive_at);
 	rxrpc_reduce_call_timer(call, keepalive_at, now,
 				rxrpc_timer_set_for_keepalive);
 }

 /*
  * Fill out an ACK packet.
  */
 static size_t rxrpc_fill_out_ack(struct rxrpc_connection *conn,
 				 struct rxrpc_call *call,
 				 struct rxrpc_ack_buffer *pkt,
 				 rxrpc_seq_t *_hard_ack,
 				 rxrpc_seq_t *_top,
 				 u8 reason)
 {
 	rxrpc_serial_t serial;
 	rxrpc_seq_t hard_ack, top, seq;
 	int ix;
 	u32 mtu, jmax;
 	u8 *ackp = pkt->acks;

 	/* Barrier against rxrpc_input_data(). */
 	serial = call->ackr_serial;
 	hard_ack = READ_ONCE(call->rx_hard_ack);
 	top = smp_load_acquire(&call->rx_top);
 	*_hard_ack = hard_ack;
 	*_top = top;

 	pkt->ack.bufferSpace	= htons(8);
 	pkt->ack.maxSkew	= htons(call->ackr_skew);
 	pkt->ack.firstPacket	= htonl(hard_ack + 1);
 	pkt->ack.previousPacket	= htonl(call->ackr_prev_seq);
 	pkt->ack.serial		= htonl(serial);
 	pkt->ack.reason		= reason;
 	pkt->ack.nAcks		= top - hard_ack;

 	if (reason == RXRPC_ACK_PING)
 		pkt->whdr.flags |= RXRPC_REQUEST_ACK;

 	if (after(top, hard_ack)) {
 		seq = hard_ack + 1;
 		do {
 			ix = seq & RXRPC_RXTX_BUFF_MASK;
 			if (call->rxtx_buffer[ix])
 				*ackp++ = RXRPC_ACK_TYPE_ACK;
 			else
 				*ackp++ = RXRPC_ACK_TYPE_NACK;
 			seq++;
 		} while (before_eq(seq, top));
 	}

 	mtu = conn->params.peer->if_mtu;
 	mtu -= conn->params.peer->hdrsize;
 	jmax = (call->nr_jumbo_bad > 3) ? 1 : rxrpc_rx_jumbo_max;
 	pkt->ackinfo.rxMTU	= htonl(rxrpc_rx_mtu);
 	pkt->ackinfo.maxMTU	= htonl(mtu);
 	pkt->ackinfo.rwind	= htonl(call->rx_winsize);
 	pkt->ackinfo.jumbo_max	= htonl(jmax);

 	*ackp++ = 0;
 	*ackp++ = 0;
 	*ackp++ = 0;
 	return top - hard_ack + 3;
 }

 /*
  * Send an ACK call packet.
  */
 int rxrpc_send_ack_packet(struct rxrpc_call *call, bool ping,
 			  rxrpc_serial_t *_serial)
 {
 	struct rxrpc_connection *conn = NULL;
 	struct rxrpc_ack_buffer *pkt;
 	struct msghdr msg;
 	struct kvec iov[2];
 	rxrpc_serial_t serial;
 	rxrpc_seq_t hard_ack, top;
 	size_t len, n;
 	int ret;
 	u8 reason;

 	spin_lock_bh(&call->lock);
 	if (call->conn)
 		conn = rxrpc_get_connection_maybe(call->conn);
 	spin_unlock_bh(&call->lock);
 	if (!conn)
 		return -ECONNRESET;

 	pkt = kzalloc(sizeof(*pkt), GFP_KERNEL);
 	if (!pkt) {
 		rxrpc_put_connection(conn);
 		return -ENOMEM;
 	}

 	msg.msg_name	= &call->peer->srx.transport;
 	msg.msg_namelen	= call->peer->srx.transport_len;
 	msg.msg_control	= NULL;
 	msg.msg_controllen = 0;
 	msg.msg_flags	= 0;

 	pkt->whdr.epoch		= htonl(conn->proto.epoch);
 	pkt->whdr.cid		= htonl(call->cid);
 	pkt->whdr.callNumber	= htonl(call->call_id);
 	pkt->whdr.seq		= 0;
 	pkt->whdr.type		= RXRPC_PACKET_TYPE_ACK;
 	pkt->whdr.flags		= RXRPC_SLOW_START_OK | conn->out_clientflag;
 	pkt->whdr.userStatus	= 0;
 	pkt->whdr.securityIndex	= call->security_ix;
 	pkt->whdr._rsvd		= 0;
 	pkt->whdr.serviceId	= htons(call->service_id);

 	spin_lock_bh(&call->lock);
 	if (ping) {
 		reason = RXRPC_ACK_PING;
 	} else {
 		reason = call->ackr_reason;
 		if (!call->ackr_reason) {
 			spin_unlock_bh(&call->lock);
 			ret = 0;
 			goto out;
 		}
 		call->ackr_reason = 0;
 	}
 	n = rxrpc_fill_out_ack(conn, call, pkt, &hard_ack, &top, reason);

 	spin_unlock_bh(&call->lock);

 	iov[0].iov_base	= pkt;
 	iov[0].iov_len	= sizeof(pkt->whdr) + sizeof(pkt->ack) + n;
 	iov[1].iov_base = &pkt->ackinfo;
 	iov[1].iov_len	= sizeof(pkt->ackinfo);
 	len = iov[0].iov_len + iov[1].iov_len;

 	serial = atomic_inc_return(&conn->serial);
 	pkt->whdr.serial = htonl(serial);
 	trace_rxrpc_tx_ack(call->debug_id, serial,
 			   ntohl(pkt->ack.firstPacket),
 			   ntohl(pkt->ack.serial),
 			   pkt->ack.reason, pkt->ack.nAcks);
 	if (_serial)
 		*_serial = serial;

 	if (ping) {
 		call->ping_serial = serial;
 		smp_wmb();
 		/* We need to stick a time in before we send the packet in case
 		 * the reply gets back before kernel_sendmsg() completes - but
 		 * asking UDP to send the packet can take a relatively long
 		 * time.
 		 */
 		call->ping_time = ktime_get_real();
 		set_bit(RXRPC_CALL_PINGING, &call->flags);
 		trace_rxrpc_rtt_tx(call, rxrpc_rtt_tx_ping, serial);
 	}

 	ret = kernel_sendmsg(conn->params.local->socket, &msg, iov, 2, len);
 	conn->params.peer->last_tx_at = ktime_get_seconds();
 	if (ret < 0)
 		trace_rxrpc_tx_fail(call->debug_id, serial, ret,
 				    rxrpc_tx_point_call_ack);
 	else
 		trace_rxrpc_tx_packet(call->debug_id, &pkt->whdr,
 				      rxrpc_tx_point_call_ack);
 	rxrpc_tx_backoff(call, ret);

 	if (call->state < RXRPC_CALL_COMPLETE) {
 		if (ret < 0) {
 			if (ping)
 				clear_bit(RXRPC_CALL_PINGING, &call->flags);
 			rxrpc_propose_ACK(call, pkt->ack.reason,
 					  ntohs(pkt->ack.maxSkew),
 					  ntohl(pkt->ack.serial),
 					  false, true,
 					  rxrpc_propose_ack_retry_tx);
 		} else {
 			spin_lock_bh(&call->lock);
 			if (after(hard_ack, call->ackr_consumed))
 				call->ackr_consumed = hard_ack;
 			if (after(top, call->ackr_seen))
 				call->ackr_seen = top;
 			spin_unlock_bh(&call->lock);
 		}

 		rxrpc_set_keepalive(call);
 	}

 out:
 	rxrpc_put_connection(conn);
 	kfree(pkt);
 	return ret;
 }

 /*
  * Send an ABORT call packet.
  */
 int rxrpc_send_abort_packet(struct rxrpc_call *call)
 {
 	struct rxrpc_connection *conn = NULL;
 	struct rxrpc_abort_buffer pkt;
 	struct msghdr msg;
 	struct kvec iov[1];
 	rxrpc_serial_t serial;
 	int ret;

 	/* Don't bother sending aborts for a client call once the server has
 	 * hard-ACK'd all of its request data.  After that point, we're not
 	 * going to stop the operation proceeding, and whilst we might limit
 	 * the reply, it's not worth it if we can send a new call on the same
 	 * channel instead, thereby closing off this call.
 	 */
 	if (rxrpc_is_client_call(call) &&
 	    test_bit(RXRPC_CALL_TX_LAST, &call->flags))
 		return 0;

 	spin_lock_bh(&call->lock);
 	if (call->conn)
 		conn = rxrpc_get_connection_maybe(call->conn);
 	spin_unlock_bh(&call->lock);
 	if (!conn)
 		return -ECONNRESET;

 	msg.msg_name	= &call->peer->srx.transport;
 	msg.msg_namelen	= call->peer->srx.transport_len;
 	msg.msg_control	= NULL;
 	msg.msg_controllen = 0;
 	msg.msg_flags	= 0;

 	pkt.whdr.epoch		= htonl(conn->proto.epoch);
 	pkt.whdr.cid		= htonl(call->cid);
 	pkt.whdr.callNumber	= htonl(call->call_id);
 	pkt.whdr.seq		= 0;
 	pkt.whdr.type		= RXRPC_PACKET_TYPE_ABORT;
 	pkt.whdr.flags		= conn->out_clientflag;
 	pkt.whdr.userStatus	= 0;
 	pkt.whdr.securityIndex	= call->security_ix;
 	pkt.whdr._rsvd		= 0;
 	pkt.whdr.serviceId	= htons(call->service_id);
 	pkt.abort_code		= htonl(call->abort_code);

 	iov[0].iov_base	= &pkt;
 	iov[0].iov_len	= sizeof(pkt);

 	serial = atomic_inc_return(&conn->serial);
 	pkt.whdr.serial = htonl(serial);

 	ret = kernel_sendmsg(conn->params.local->socket,
 			     &msg, iov, 1, sizeof(pkt));
 	conn->params.peer->last_tx_at = ktime_get_seconds();
 	if (ret < 0)
 		trace_rxrpc_tx_fail(call->debug_id, serial, ret,
 				    rxrpc_tx_point_call_abort);
 	else
 		trace_rxrpc_tx_packet(call->debug_id, &pkt.whdr,
 				      rxrpc_tx_point_call_abort);
 	rxrpc_tx_backoff(call, ret);

 	rxrpc_put_connection(conn);
 	return ret;
 }

 /*
  * send a packet through the transport endpoint
  */
 int rxrpc_send_data_packet(struct rxrpc_call *call, struct sk_buff *skb,
 			   bool retrans)
 {
 	struct rxrpc_connection *conn = call->conn;
 	struct rxrpc_wire_header whdr;
 	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
 	struct msghdr msg;
 	struct kvec iov[2];
 	rxrpc_serial_t serial;
 	size_t len;
 	bool lost = false;
 	int ret, opt;

 	_enter(",{%d}", skb->len);

 	/* Each transmission of a Tx packet needs a new serial number */
 	serial = atomic_inc_return(&conn->serial);

 	whdr.epoch	= htonl(conn->proto.epoch);
 	whdr.cid	= htonl(call->cid);
 	whdr.callNumber	= htonl(call->call_id);
 	whdr.seq	= htonl(sp->hdr.seq);
 	whdr.serial	= htonl(serial);
 	whdr.type	= RXRPC_PACKET_TYPE_DATA;
 	whdr.flags	= sp->hdr.flags;
 	whdr.userStatus	= 0;
 	whdr.securityIndex = call->security_ix;
 	whdr._rsvd	= htons(sp->hdr._rsvd);
 	whdr.serviceId	= htons(call->service_id);

 	if (test_bit(RXRPC_CONN_PROBING_FOR_UPGRADE, &conn->flags) &&
 	    sp->hdr.seq == 1)
 		whdr.userStatus	= RXRPC_USERSTATUS_SERVICE_UPGRADE;

 	iov[0].iov_base = &whdr;
 	iov[0].iov_len = sizeof(whdr);
 	iov[1].iov_base = skb->head;
 	iov[1].iov_len = skb->len;
 	len = iov[0].iov_len + iov[1].iov_len;

 	msg.msg_name = &call->peer->srx.transport;
 	msg.msg_namelen = call->peer->srx.transport_len;
 	msg.msg_control = NULL;
 	msg.msg_controllen = 0;
 	msg.msg_flags = 0;

 	/* If our RTT cache needs working on, request an ACK.  Also request
 	 * ACKs if a DATA packet appears to have been lost.
 	 *
 	 * However, we mustn't request an ACK on the last reply packet of a
 	 * service call, lest OpenAFS incorrectly send us an ACK with some
 	 * soft-ACKs in it and then never follow up with a proper hard ACK.
 	 */
 	if ((!(sp->hdr.flags & RXRPC_LAST_PACKET) ||
 	     rxrpc_to_server(sp)
 	     ) &&
 	    (test_and_clear_bit(RXRPC_CALL_EV_ACK_LOST, &call->events) ||
 	     retrans ||
 	     call->cong_mode == RXRPC_CALL_SLOW_START ||
 	     (call->peer->rtt_usage < 3 && sp->hdr.seq & 1) ||
 	     ktime_before(ktime_add_ms(call->peer->rtt_last_req, 1000),
 			  ktime_get_real())))
 		whdr.flags |= RXRPC_REQUEST_ACK;

 	if (IS_ENABLED(CONFIG_AF_RXRPC_INJECT_LOSS)) {
 		static int lose;
 		if ((lose++ & 7) == 7) {
 			ret = 0;
 			lost = true;
 			goto done;
 		}
 	}

 	_proto("Tx DATA %%%u { #%u }", serial, sp->hdr.seq);

 	/* send the packet with the don't fragment bit set if we currently
 	 * think it's small enough */
 	if (iov[1].iov_len >= call->peer->maxdata)
 		goto send_fragmentable;

 	down_read(&conn->params.local->defrag_sem);

 	sp->hdr.serial = serial;
 	smp_wmb(); /* Set serial before timestamp */
 	skb->tstamp = ktime_get_real();

 	/* send the packet by UDP
 	 * - returns -EMSGSIZE if UDP would have to fragment the packet
 	 *   to go out of the interface
 	 *   - in which case, we'll have processed the ICMP error
 	 *     message and update the peer record
 	 */
 	ret = kernel_sendmsg(conn->params.local->socket, &msg, iov, 2, len);
 	conn->params.peer->last_tx_at = ktime_get_seconds();

 	up_read(&conn->params.local->defrag_sem);
 	if (ret < 0)
 		trace_rxrpc_tx_fail(call->debug_id, serial, ret,
 				    rxrpc_tx_point_call_data_nofrag);
 	else
 		trace_rxrpc_tx_packet(call->debug_id, &whdr,
 				      rxrpc_tx_point_call_data_nofrag);
 	rxrpc_tx_backoff(call, ret);
 	if (ret == -EMSGSIZE)
 		goto send_fragmentable;

 done:
 	trace_rxrpc_tx_data(call, sp->hdr.seq, serial, whdr.flags,
 			    retrans, lost);
 	if (ret >= 0) {
 		if (whdr.flags & RXRPC_REQUEST_ACK) {
 			call->peer->rtt_last_req = skb->tstamp;
 			trace_rxrpc_rtt_tx(call, rxrpc_rtt_tx_data, serial);
 			if (call->peer->rtt_usage > 1) {
 				unsigned long nowj = jiffies, ack_lost_at;

 				ack_lost_at = nsecs_to_jiffies(2 * call->peer->rtt);
 				if (ack_lost_at < 1)
 					ack_lost_at = 1;

 				ack_lost_at += nowj;
 				WRITE_ONCE(call->ack_lost_at, ack_lost_at);
 				rxrpc_reduce_call_timer(call, ack_lost_at, nowj,
 							rxrpc_timer_set_for_lost_ack);
 			}
 		}

 		if (sp->hdr.seq == 1 &&
 		    !test_and_set_bit(RXRPC_CALL_BEGAN_RX_TIMER,
 				      &call->flags)) {
 			unsigned long nowj = jiffies, expect_rx_by;

 			expect_rx_by = nowj + call->next_rx_timo;
 			WRITE_ONCE(call->expect_rx_by, expect_rx_by);
 			rxrpc_reduce_call_timer(call, expect_rx_by, nowj,
 						rxrpc_timer_set_for_normal);
 		}

 		rxrpc_set_keepalive(call);
 	} else {
 		/* Cancel the call if the initial transmission fails,
 		 * particularly if that's due to network routing issues that
 		 * aren't going away anytime soon.  The layer above can arrange
 		 * the retransmission.
 		 */
 		if (!test_and_set_bit(RXRPC_CALL_BEGAN_RX_TIMER, &call->flags))
 			rxrpc_set_call_completion(call, RXRPC_CALL_LOCAL_ERROR,
 						  RX_USER_ABORT, ret);
 	}

 	_leave(" = %d [%u]", ret, call->peer->maxdata);
 	return ret;

 send_fragmentable:
 	/* attempt to send this message with fragmentation enabled */
 	_debug("send fragment");

 	down_write(&conn->params.local->defrag_sem);

 	sp->hdr.serial = serial;
 	smp_wmb(); /* Set serial before timestamp */
 	skb->tstamp = ktime_get_real();

 	switch (conn->params.local->srx.transport.family) {
 	case AF_INET:
 		opt = IP_PMTUDISC_DONT;
 		ret = kernel_setsockopt(conn->params.local->socket,
 					SOL_IP, IP_MTU_DISCOVER,
 					(char *)&opt, sizeof(opt));
 		if (ret == 0) {
 			ret = kernel_sendmsg(conn->params.local->socket, &msg,
 					     iov, 2, len);
 			conn->params.peer->last_tx_at = ktime_get_seconds();

 			opt = IP_PMTUDISC_DO;
 			kernel_setsockopt(conn->params.local->socket, SOL_IP,
 					  IP_MTU_DISCOVER,
 					  (char *)&opt, sizeof(opt));
 		}
 		break;

 #ifdef CONFIG_AF_RXRPC_IPV6
 	case AF_INET6:
 		opt = IPV6_PMTUDISC_DONT;
 		ret = kernel_setsockopt(conn->params.local->socket,
 					SOL_IPV6, IPV6_MTU_DISCOVER,
 					(char *)&opt, sizeof(opt));
 		if (ret == 0) {
 			ret = kernel_sendmsg(conn->params.local->socket, &msg,
 					     iov, 2, len);
 			conn->params.peer->last_tx_at = ktime_get_seconds();

 			opt = IPV6_PMTUDISC_DO;
 			kernel_setsockopt(conn->params.local->socket,
 					  SOL_IPV6, IPV6_MTU_DISCOVER,
 					  (char *)&opt, sizeof(opt));
 		}
 		break;
 #endif
 	}

 	if (ret < 0)
 		trace_rxrpc_tx_fail(call->debug_id, serial, ret,
 				    rxrpc_tx_point_call_data_frag);
 	else
 		trace_rxrpc_tx_packet(call->debug_id, &whdr,
 				      rxrpc_tx_point_call_data_frag);
 	rxrpc_tx_backoff(call, ret);

 	up_write(&conn->params.local->defrag_sem);
 	goto done;
 }

 /*
  * reject packets through the local endpoint
  */
 void rxrpc_reject_packets(struct rxrpc_local *local)
 {
 	struct sockaddr_rxrpc srx;
 	struct rxrpc_skb_priv *sp;
 	struct rxrpc_wire_header whdr;
 	struct sk_buff *skb;
 	struct msghdr msg;
 	struct kvec iov[2];
 	size_t size;
 	__be32 code;
 	int ret, ioc;

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

 	iov[0].iov_base = &whdr;
 	iov[0].iov_len = sizeof(whdr);
 	iov[1].iov_base = &code;
 	iov[1].iov_len = sizeof(code);

 	msg.msg_name = &srx.transport;
 	msg.msg_control = NULL;
 	msg.msg_controllen = 0;
 	msg.msg_flags = 0;

 	memset(&whdr, 0, sizeof(whdr));

 	while ((skb = skb_dequeue(&local->reject_queue))) {
 		rxrpc_see_skb(skb, rxrpc_skb_rx_seen);
 		sp = rxrpc_skb(skb);

 		switch (skb->mark) {
 		case RXRPC_SKB_MARK_REJECT_BUSY:
 			whdr.type = RXRPC_PACKET_TYPE_BUSY;
 			size = sizeof(whdr);
 			ioc = 1;
 			break;
 		case RXRPC_SKB_MARK_REJECT_ABORT:
 			whdr.type = RXRPC_PACKET_TYPE_ABORT;
 			code = htonl(skb->priority);
 			size = sizeof(whdr) + sizeof(code);
 			ioc = 2;
 			break;
 		default:
 			rxrpc_free_skb(skb, rxrpc_skb_rx_freed);
 			continue;
 		}

 		if (rxrpc_extract_addr_from_skb(local, &srx, skb) == 0) {
 			msg.msg_namelen = srx.transport_len;

 			whdr.epoch	= htonl(sp->hdr.epoch);
 			whdr.cid	= htonl(sp->hdr.cid);
 			whdr.callNumber	= htonl(sp->hdr.callNumber);
 			whdr.serviceId	= htons(sp->hdr.serviceId);
 			whdr.flags	= sp->hdr.flags;
 			whdr.flags	^= RXRPC_CLIENT_INITIATED;
 			whdr.flags	&= RXRPC_CLIENT_INITIATED;

 			ret = kernel_sendmsg(local->socket, &msg,
 					     iov, ioc, size);
 			if (ret < 0)
 				trace_rxrpc_tx_fail(local->debug_id, 0, ret,
 						    rxrpc_tx_point_reject);
 			else
 				trace_rxrpc_tx_packet(local->debug_id, &whdr,
 						      rxrpc_tx_point_reject);
 		}

 		rxrpc_free_skb(skb, rxrpc_skb_rx_freed);
 	}

 	_leave("");
 }

 /*
  * Send a VERSION reply to a peer as a keepalive.
  */
 void rxrpc_send_keepalive(struct rxrpc_peer *peer)
 {
 	struct rxrpc_wire_header whdr;
 	struct msghdr msg;
 	struct kvec iov[2];
 	size_t len;
 	int ret;

 	_enter("");

 	msg.msg_name	= &peer->srx.transport;
 	msg.msg_namelen	= peer->srx.transport_len;
 	msg.msg_control	= NULL;
 	msg.msg_controllen = 0;
 	msg.msg_flags	= 0;

 	whdr.epoch	= htonl(peer->local->rxnet->epoch);
 	whdr.cid	= 0;
 	whdr.callNumber	= 0;
 	whdr.seq	= 0;
 	whdr.serial	= 0;
 	whdr.type	= RXRPC_PACKET_TYPE_VERSION; /* Not client-initiated */
 	whdr.flags	= RXRPC_LAST_PACKET;
 	whdr.userStatus	= 0;
 	whdr.securityIndex = 0;
 	whdr._rsvd	= 0;
 	whdr.serviceId	= 0;

 	iov[0].iov_base	= &whdr;
 	iov[0].iov_len	= sizeof(whdr);
 	iov[1].iov_base	= (char *)rxrpc_keepalive_string;
 	iov[1].iov_len	= sizeof(rxrpc_keepalive_string);

 	len = iov[0].iov_len + iov[1].iov_len;

 	_proto("Tx VERSION (keepalive)");

 	ret = kernel_sendmsg(peer->local->socket, &msg, iov, 2, len);
 	if (ret < 0)
 		trace_rxrpc_tx_fail(peer->debug_id, 0, ret,
 				    rxrpc_tx_point_version_keepalive);
 	else
 		trace_rxrpc_tx_packet(peer->debug_id, &whdr,
 				      rxrpc_tx_point_version_keepalive);

 	peer->last_tx_at = ktime_get_seconds();
 	_leave("");
 }
	/* RxRPC packet transmission
	*
	* Copyright (C) 2007 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 License
	* as published by the Free Software Foundation; either version
	* 2 of the License, 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 <net/sock.h>
	#include <net/af_rxrpc.h>
	#include "ar-internal.h"

	struct rxrpc_ack_buffer {
	struct rxrpc_wire_header whdr;
	struct rxrpc_ackpacket ack;
	u8 acks[255];
	u8 pad[3];
	struct rxrpc_ackinfo ackinfo;
	};

	struct rxrpc_abort_buffer {
	struct rxrpc_wire_header whdr;
	__be32 abort_code;
	};

	static const char rxrpc_keepalive_string[] = "";

	/*
	* Increase Tx backoff on transmission failure and clear it on success.
	*/
	static void rxrpc_tx_backoff(struct rxrpc_call *call, int ret)
	{
	if (ret < 0) {
	u16 tx_backoff = READ_ONCE(call->tx_backoff);

	if (tx_backoff < HZ)
	WRITE_ONCE(call->tx_backoff, tx_backoff + 1);
	} else {
	WRITE_ONCE(call->tx_backoff, 0);
	}
	}

	/*
	* Arrange for a keepalive ping a certain time after we last transmitted. This
	* lets the far side know we're still interested in this call and helps keep
	* the route through any intervening firewall open.
	*
	* Receiving a response to the ping will prevent the ->expect_rx_by timer from
	* expiring.
	*/
	static void rxrpc_set_keepalive(struct rxrpc_call *call)
	{
	unsigned long now = jiffies, keepalive_at = call->next_rx_timo / 6;

	keepalive_at += now;
	WRITE_ONCE(call->keepalive_at, keepalive_at);
	rxrpc_reduce_call_timer(call, keepalive_at, now,
	rxrpc_timer_set_for_keepalive);
	}

	/*
	* Fill out an ACK packet.
	*/
	static size_t rxrpc_fill_out_ack(struct rxrpc_connection *conn,
	struct rxrpc_call *call,
	struct rxrpc_ack_buffer *pkt,
	rxrpc_seq_t *_hard_ack,
	rxrpc_seq_t *_top,
	u8 reason)
	{
	rxrpc_serial_t serial;
	rxrpc_seq_t hard_ack, top, seq;
	int ix;
	u32 mtu, jmax;
	u8 *ackp = pkt->acks;

	/* Barrier against rxrpc_input_data(). */
	serial = call->ackr_serial;
	hard_ack = READ_ONCE(call->rx_hard_ack);
	top = smp_load_acquire(&call->rx_top);
	*_hard_ack = hard_ack;
	*_top = top;

	pkt->ack.bufferSpace = htons(8);
	pkt->ack.maxSkew = htons(call->ackr_skew);
	pkt->ack.firstPacket = htonl(hard_ack + 1);
	pkt->ack.previousPacket = htonl(call->ackr_prev_seq);
	pkt->ack.serial = htonl(serial);
	pkt->ack.reason = reason;
	pkt->ack.nAcks = top - hard_ack;

	if (reason == RXRPC_ACK_PING)
	pkt->whdr.flags \|= RXRPC_REQUEST_ACK;

	if (after(top, hard_ack)) {
	seq = hard_ack + 1;
	do {
	ix = seq & RXRPC_RXTX_BUFF_MASK;
	if (call->rxtx_buffer[ix])
	*ackp++ = RXRPC_ACK_TYPE_ACK;
	else
	*ackp++ = RXRPC_ACK_TYPE_NACK;
	seq++;
	} while (before_eq(seq, top));
	}

	mtu = conn->params.peer->if_mtu;
	mtu -= conn->params.peer->hdrsize;
	jmax = (call->nr_jumbo_bad > 3) ? 1 : rxrpc_rx_jumbo_max;
	pkt->ackinfo.rxMTU = htonl(rxrpc_rx_mtu);
	pkt->ackinfo.maxMTU = htonl(mtu);
	pkt->ackinfo.rwind = htonl(call->rx_winsize);
	pkt->ackinfo.jumbo_max = htonl(jmax);

	*ackp++ = 0;
	*ackp++ = 0;
	*ackp++ = 0;
	return top - hard_ack + 3;
	}

	/*
	* Send an ACK call packet.
	*/
	int rxrpc_send_ack_packet(struct rxrpc_call *call, bool ping,
	rxrpc_serial_t *_serial)
	{
	struct rxrpc_connection *conn = NULL;
	struct rxrpc_ack_buffer *pkt;
	struct msghdr msg;
	struct kvec iov[2];
	rxrpc_serial_t serial;
	rxrpc_seq_t hard_ack, top;
	size_t len, n;
	int ret;
	u8 reason;

	spin_lock_bh(&call->lock);
	if (call->conn)
	conn = rxrpc_get_connection_maybe(call->conn);
	spin_unlock_bh(&call->lock);
	if (!conn)
	return -ECONNRESET;

	pkt = kzalloc(sizeof(*pkt), GFP_KERNEL);
	if (!pkt) {
	rxrpc_put_connection(conn);
	return -ENOMEM;
	}

	msg.msg_name = &call->peer->srx.transport;
	msg.msg_namelen = call->peer->srx.transport_len;
	msg.msg_control = NULL;
	msg.msg_controllen = 0;
	msg.msg_flags = 0;

	pkt->whdr.epoch = htonl(conn->proto.epoch);
	pkt->whdr.cid = htonl(call->cid);
	pkt->whdr.callNumber = htonl(call->call_id);
	pkt->whdr.seq = 0;
	pkt->whdr.type = RXRPC_PACKET_TYPE_ACK;
	pkt->whdr.flags = RXRPC_SLOW_START_OK \| conn->out_clientflag;
	pkt->whdr.userStatus = 0;
	pkt->whdr.securityIndex = call->security_ix;
	pkt->whdr._rsvd = 0;
	pkt->whdr.serviceId = htons(call->service_id);

	spin_lock_bh(&call->lock);
	if (ping) {
	reason = RXRPC_ACK_PING;
	} else {
	reason = call->ackr_reason;
	if (!call->ackr_reason) {
	spin_unlock_bh(&call->lock);
	ret = 0;
	goto out;
	}
	call->ackr_reason = 0;
	}
	n = rxrpc_fill_out_ack(conn, call, pkt, &hard_ack, &top, reason);

	spin_unlock_bh(&call->lock);

	iov[0].iov_base = pkt;
	iov[0].iov_len = sizeof(pkt->whdr) + sizeof(pkt->ack) + n;
	iov[1].iov_base = &pkt->ackinfo;
	iov[1].iov_len = sizeof(pkt->ackinfo);
	len = iov[0].iov_len + iov[1].iov_len;

	serial = atomic_inc_return(&conn->serial);
	pkt->whdr.serial = htonl(serial);
	trace_rxrpc_tx_ack(call->debug_id, serial,
	ntohl(pkt->ack.firstPacket),
	ntohl(pkt->ack.serial),
	pkt->ack.reason, pkt->ack.nAcks);
	if (_serial)
	*_serial = serial;

	if (ping) {
	call->ping_serial = serial;
	smp_wmb();
	/* We need to stick a time in before we send the packet in case
	* the reply gets back before kernel_sendmsg() completes - but
	* asking UDP to send the packet can take a relatively long
	* time.
	*/
	call->ping_time = ktime_get_real();
	set_bit(RXRPC_CALL_PINGING, &call->flags);
	trace_rxrpc_rtt_tx(call, rxrpc_rtt_tx_ping, serial);
	}

	ret = kernel_sendmsg(conn->params.local->socket, &msg, iov, 2, len);
	conn->params.peer->last_tx_at = ktime_get_seconds();
	if (ret < 0)
	trace_rxrpc_tx_fail(call->debug_id, serial, ret,
	rxrpc_tx_point_call_ack);
	else
	trace_rxrpc_tx_packet(call->debug_id, &pkt->whdr,
	rxrpc_tx_point_call_ack);
	rxrpc_tx_backoff(call, ret);

	if (call->state < RXRPC_CALL_COMPLETE) {
	if (ret < 0) {
	if (ping)
	clear_bit(RXRPC_CALL_PINGING, &call->flags);
	rxrpc_propose_ACK(call, pkt->ack.reason,
	ntohs(pkt->ack.maxSkew),
	ntohl(pkt->ack.serial),
	false, true,
	rxrpc_propose_ack_retry_tx);
	} else {
	spin_lock_bh(&call->lock);
	if (after(hard_ack, call->ackr_consumed))
	call->ackr_consumed = hard_ack;
	if (after(top, call->ackr_seen))
	call->ackr_seen = top;
	spin_unlock_bh(&call->lock);
	}

	rxrpc_set_keepalive(call);
	}

	out:
	rxrpc_put_connection(conn);
	kfree(pkt);
	return ret;
	}

	/*
	* Send an ABORT call packet.
	*/
	int rxrpc_send_abort_packet(struct rxrpc_call *call)
	{
	struct rxrpc_connection *conn = NULL;
	struct rxrpc_abort_buffer pkt;
	struct msghdr msg;
	struct kvec iov[1];
	rxrpc_serial_t serial;
	int ret;

	/* Don't bother sending aborts for a client call once the server has
	* hard-ACK'd all of its request data. After that point, we're not
	* going to stop the operation proceeding, and whilst we might limit
	* the reply, it's not worth it if we can send a new call on the same
	* channel instead, thereby closing off this call.
	*/
	if (rxrpc_is_client_call(call) &&
	test_bit(RXRPC_CALL_TX_LAST, &call->flags))
	return 0;

	spin_lock_bh(&call->lock);
	if (call->conn)
	conn = rxrpc_get_connection_maybe(call->conn);
	spin_unlock_bh(&call->lock);
	if (!conn)
	return -ECONNRESET;

	msg.msg_name = &call->peer->srx.transport;
	msg.msg_namelen = call->peer->srx.transport_len;
	msg.msg_control = NULL;
	msg.msg_controllen = 0;
	msg.msg_flags = 0;

	pkt.whdr.epoch = htonl(conn->proto.epoch);
	pkt.whdr.cid = htonl(call->cid);
	pkt.whdr.callNumber = htonl(call->call_id);
	pkt.whdr.seq = 0;
	pkt.whdr.type = RXRPC_PACKET_TYPE_ABORT;
	pkt.whdr.flags = conn->out_clientflag;
	pkt.whdr.userStatus = 0;
	pkt.whdr.securityIndex = call->security_ix;
	pkt.whdr._rsvd = 0;
	pkt.whdr.serviceId = htons(call->service_id);
	pkt.abort_code = htonl(call->abort_code);

	iov[0].iov_base = &pkt;
	iov[0].iov_len = sizeof(pkt);

	serial = atomic_inc_return(&conn->serial);
	pkt.whdr.serial = htonl(serial);

	ret = kernel_sendmsg(conn->params.local->socket,
	&msg, iov, 1, sizeof(pkt));
	conn->params.peer->last_tx_at = ktime_get_seconds();
	if (ret < 0)
	trace_rxrpc_tx_fail(call->debug_id, serial, ret,
	rxrpc_tx_point_call_abort);
	else
	trace_rxrpc_tx_packet(call->debug_id, &pkt.whdr,
	rxrpc_tx_point_call_abort);
	rxrpc_tx_backoff(call, ret);

	rxrpc_put_connection(conn);
	return ret;
	}

	/*
	* send a packet through the transport endpoint
	*/
	int rxrpc_send_data_packet(struct rxrpc_call call, struct sk_buff skb,
	bool retrans)
	{
	struct rxrpc_connection *conn = call->conn;
	struct rxrpc_wire_header whdr;
	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
	struct msghdr msg;
	struct kvec iov[2];
	rxrpc_serial_t serial;
	size_t len;
	bool lost = false;
	int ret, opt;

	_enter(",{%d}", skb->len);

	/* Each transmission of a Tx packet needs a new serial number */
	serial = atomic_inc_return(&conn->serial);

	whdr.epoch = htonl(conn->proto.epoch);
	whdr.cid = htonl(call->cid);
	whdr.callNumber = htonl(call->call_id);
	whdr.seq = htonl(sp->hdr.seq);
	whdr.serial = htonl(serial);
	whdr.type = RXRPC_PACKET_TYPE_DATA;
	whdr.flags = sp->hdr.flags;
	whdr.userStatus = 0;
	whdr.securityIndex = call->security_ix;
	whdr._rsvd = htons(sp->hdr._rsvd);
	whdr.serviceId = htons(call->service_id);

	if (test_bit(RXRPC_CONN_PROBING_FOR_UPGRADE, &conn->flags) &&
	sp->hdr.seq == 1)
	whdr.userStatus = RXRPC_USERSTATUS_SERVICE_UPGRADE;

	iov[0].iov_base = &whdr;
	iov[0].iov_len = sizeof(whdr);
	iov[1].iov_base = skb->head;
	iov[1].iov_len = skb->len;
	len = iov[0].iov_len + iov[1].iov_len;

	msg.msg_name = &call->peer->srx.transport;
	msg.msg_namelen = call->peer->srx.transport_len;
	msg.msg_control = NULL;
	msg.msg_controllen = 0;
	msg.msg_flags = 0;

	/* If our RTT cache needs working on, request an ACK. Also request
	* ACKs if a DATA packet appears to have been lost.
	*
	* However, we mustn't request an ACK on the last reply packet of a
	* service call, lest OpenAFS incorrectly send us an ACK with some
	* soft-ACKs in it and then never follow up with a proper hard ACK.
	*/
	if ((!(sp->hdr.flags & RXRPC_LAST_PACKET) \|\|
	rxrpc_to_server(sp)
	) &&
	(test_and_clear_bit(RXRPC_CALL_EV_ACK_LOST, &call->events) \|\|
	retrans \|\|
	call->cong_mode == RXRPC_CALL_SLOW_START \|\|
	(call->peer->rtt_usage < 3 && sp->hdr.seq & 1) \|\|
	ktime_before(ktime_add_ms(call->peer->rtt_last_req, 1000),
	ktime_get_real())))
	whdr.flags \|= RXRPC_REQUEST_ACK;

	if (IS_ENABLED(CONFIG_AF_RXRPC_INJECT_LOSS)) {
	static int lose;
	if ((lose++ & 7) == 7) {
	ret = 0;
	lost = true;
	goto done;
	}
	}

	_proto("Tx DATA %%%u { #%u }", serial, sp->hdr.seq);

	/* send the packet with the don't fragment bit set if we currently
	* think it's small enough */
	if (iov[1].iov_len >= call->peer->maxdata)
	goto send_fragmentable;

	down_read(&conn->params.local->defrag_sem);

	sp->hdr.serial = serial;
	smp_wmb(); /* Set serial before timestamp */
	skb->tstamp = ktime_get_real();

	/* send the packet by UDP
	* - returns -EMSGSIZE if UDP would have to fragment the packet
	* to go out of the interface
	* - in which case, we'll have processed the ICMP error
	* message and update the peer record
	*/
	ret = kernel_sendmsg(conn->params.local->socket, &msg, iov, 2, len);
	conn->params.peer->last_tx_at = ktime_get_seconds();

	up_read(&conn->params.local->defrag_sem);
	if (ret < 0)
	trace_rxrpc_tx_fail(call->debug_id, serial, ret,
	rxrpc_tx_point_call_data_nofrag);
	else
	trace_rxrpc_tx_packet(call->debug_id, &whdr,
	rxrpc_tx_point_call_data_nofrag);
	rxrpc_tx_backoff(call, ret);
	if (ret == -EMSGSIZE)
	goto send_fragmentable;

	done:
	trace_rxrpc_tx_data(call, sp->hdr.seq, serial, whdr.flags,
	retrans, lost);
	if (ret >= 0) {
	if (whdr.flags & RXRPC_REQUEST_ACK) {
	call->peer->rtt_last_req = skb->tstamp;
	trace_rxrpc_rtt_tx(call, rxrpc_rtt_tx_data, serial);
	if (call->peer->rtt_usage > 1) {
	unsigned long nowj = jiffies, ack_lost_at;

	ack_lost_at = nsecs_to_jiffies(2 * call->peer->rtt);
	if (ack_lost_at < 1)
	ack_lost_at = 1;

	ack_lost_at += nowj;
	WRITE_ONCE(call->ack_lost_at, ack_lost_at);
	rxrpc_reduce_call_timer(call, ack_lost_at, nowj,
	rxrpc_timer_set_for_lost_ack);
	}
	}

	if (sp->hdr.seq == 1 &&
	!test_and_set_bit(RXRPC_CALL_BEGAN_RX_TIMER,
	&call->flags)) {
	unsigned long nowj = jiffies, expect_rx_by;

	expect_rx_by = nowj + call->next_rx_timo;
	WRITE_ONCE(call->expect_rx_by, expect_rx_by);
	rxrpc_reduce_call_timer(call, expect_rx_by, nowj,
	rxrpc_timer_set_for_normal);
	}

	rxrpc_set_keepalive(call);
	} else {
	/* Cancel the call if the initial transmission fails,
	* particularly if that's due to network routing issues that
	* aren't going away anytime soon. The layer above can arrange
	* the retransmission.
	*/
	if (!test_and_set_bit(RXRPC_CALL_BEGAN_RX_TIMER, &call->flags))
	rxrpc_set_call_completion(call, RXRPC_CALL_LOCAL_ERROR,
	RX_USER_ABORT, ret);
	}

	_leave(" = %d [%u]", ret, call->peer->maxdata);
	return ret;

	send_fragmentable:
	/* attempt to send this message with fragmentation enabled */
	_debug("send fragment");

	down_write(&conn->params.local->defrag_sem);

	sp->hdr.serial = serial;
	smp_wmb(); /* Set serial before timestamp */
	skb->tstamp = ktime_get_real();

	switch (conn->params.local->srx.transport.family) {
	case AF_INET:
	opt = IP_PMTUDISC_DONT;
	ret = kernel_setsockopt(conn->params.local->socket,
	SOL_IP, IP_MTU_DISCOVER,
	(char *)&opt, sizeof(opt));
	if (ret == 0) {
	ret = kernel_sendmsg(conn->params.local->socket, &msg,
	iov, 2, len);
	conn->params.peer->last_tx_at = ktime_get_seconds();

	opt = IP_PMTUDISC_DO;
	kernel_setsockopt(conn->params.local->socket, SOL_IP,
	IP_MTU_DISCOVER,
	(char *)&opt, sizeof(opt));
	}
	break;

	#ifdef CONFIG_AF_RXRPC_IPV6
	case AF_INET6:
	opt = IPV6_PMTUDISC_DONT;
	ret = kernel_setsockopt(conn->params.local->socket,
	SOL_IPV6, IPV6_MTU_DISCOVER,
	(char *)&opt, sizeof(opt));
	if (ret == 0) {
	ret = kernel_sendmsg(conn->params.local->socket, &msg,
	iov, 2, len);
	conn->params.peer->last_tx_at = ktime_get_seconds();

	opt = IPV6_PMTUDISC_DO;
	kernel_setsockopt(conn->params.local->socket,
	SOL_IPV6, IPV6_MTU_DISCOVER,
	(char *)&opt, sizeof(opt));
	}
	break;
	#endif
	}

	if (ret < 0)
	trace_rxrpc_tx_fail(call->debug_id, serial, ret,
	rxrpc_tx_point_call_data_frag);
	else
	trace_rxrpc_tx_packet(call->debug_id, &whdr,
	rxrpc_tx_point_call_data_frag);
	rxrpc_tx_backoff(call, ret);

	up_write(&conn->params.local->defrag_sem);
	goto done;
	}

	/*
	* reject packets through the local endpoint
	*/
	void rxrpc_reject_packets(struct rxrpc_local *local)
	{
	struct sockaddr_rxrpc srx;
	struct rxrpc_skb_priv *sp;
	struct rxrpc_wire_header whdr;
	struct sk_buff *skb;
	struct msghdr msg;
	struct kvec iov[2];
	size_t size;
	__be32 code;
	int ret, ioc;

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

	iov[0].iov_base = &whdr;
	iov[0].iov_len = sizeof(whdr);
	iov[1].iov_base = &code;
	iov[1].iov_len = sizeof(code);

	msg.msg_name = &srx.transport;
	msg.msg_control = NULL;
	msg.msg_controllen = 0;
	msg.msg_flags = 0;

	memset(&whdr, 0, sizeof(whdr));

	while ((skb = skb_dequeue(&local->reject_queue))) {
	rxrpc_see_skb(skb, rxrpc_skb_rx_seen);
	sp = rxrpc_skb(skb);

	switch (skb->mark) {
	case RXRPC_SKB_MARK_REJECT_BUSY:
	whdr.type = RXRPC_PACKET_TYPE_BUSY;
	size = sizeof(whdr);
	ioc = 1;
	break;
	case RXRPC_SKB_MARK_REJECT_ABORT:
	whdr.type = RXRPC_PACKET_TYPE_ABORT;
	code = htonl(skb->priority);
	size = sizeof(whdr) + sizeof(code);
	ioc = 2;
	break;
	default:
	rxrpc_free_skb(skb, rxrpc_skb_rx_freed);
	continue;
	}

	if (rxrpc_extract_addr_from_skb(local, &srx, skb) == 0) {
	msg.msg_namelen = srx.transport_len;

	whdr.epoch = htonl(sp->hdr.epoch);
	whdr.cid = htonl(sp->hdr.cid);
	whdr.callNumber = htonl(sp->hdr.callNumber);
	whdr.serviceId = htons(sp->hdr.serviceId);
	whdr.flags = sp->hdr.flags;
	whdr.flags ^= RXRPC_CLIENT_INITIATED;
	whdr.flags &= RXRPC_CLIENT_INITIATED;

	ret = kernel_sendmsg(local->socket, &msg,
	iov, ioc, size);
	if (ret < 0)
	trace_rxrpc_tx_fail(local->debug_id, 0, ret,
	rxrpc_tx_point_reject);
	else
	trace_rxrpc_tx_packet(local->debug_id, &whdr,
	rxrpc_tx_point_reject);
	}

	rxrpc_free_skb(skb, rxrpc_skb_rx_freed);
	}

	_leave("");
	}

	/*
	* Send a VERSION reply to a peer as a keepalive.
	*/
	void rxrpc_send_keepalive(struct rxrpc_peer *peer)
	{
	struct rxrpc_wire_header whdr;
	struct msghdr msg;
	struct kvec iov[2];
	size_t len;
	int ret;

	_enter("");

	msg.msg_name = &peer->srx.transport;
	msg.msg_namelen = peer->srx.transport_len;
	msg.msg_control = NULL;
	msg.msg_controllen = 0;
	msg.msg_flags = 0;

	whdr.epoch = htonl(peer->local->rxnet->epoch);
	whdr.cid = 0;
	whdr.callNumber = 0;
	whdr.seq = 0;
	whdr.serial = 0;
	whdr.type = RXRPC_PACKET_TYPE_VERSION; /* Not client-initiated */
	whdr.flags = RXRPC_LAST_PACKET;
	whdr.userStatus = 0;
	whdr.securityIndex = 0;
	whdr._rsvd = 0;
	whdr.serviceId = 0;

	iov[0].iov_base = &whdr;
	iov[0].iov_len = sizeof(whdr);
	iov[1].iov_base = (char *)rxrpc_keepalive_string;
	iov[1].iov_len = sizeof(rxrpc_keepalive_string);

	len = iov[0].iov_len + iov[1].iov_len;

	_proto("Tx VERSION (keepalive)");

	ret = kernel_sendmsg(peer->local->socket, &msg, iov, 2, len);
	if (ret < 0)
	trace_rxrpc_tx_fail(peer->debug_id, 0, ret,
	rxrpc_tx_point_version_keepalive);
	else
	trace_rxrpc_tx_packet(peer->debug_id, &whdr,
	rxrpc_tx_point_version_keepalive);

	peer->last_tx_at = ktime_get_seconds();
	_leave("");
	}