Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 733 insertions, 0 deletions

diff --git a/net/rxrpc/output.c b/net/rxrpc/output.c
new file mode 100644
index 0000000000..a0906145e8
--- /dev/null
+++ b/net/rxrpc/output.c
@@ -0,0 +1,733 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* RxRPC packet transmission
+ *
+ * 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/gfp.h>
+#include <linux/skbuff.h>
+#include <linux/export.h>
+#include <net/sock.h>
+#include <net/af_rxrpc.h>
+#include <net/udp.h>
+#include "ar-internal.h"
+
+extern int udpv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len);
+
+static ssize_t do_udp_sendmsg(struct socket *socket, struct msghdr *msg, size_t len)
+{
+	struct sockaddr *sa = msg->msg_name;
+	struct sock *sk = socket->sk;
+
+	if (IS_ENABLED(CONFIG_AF_RXRPC_IPV6)) {
+		if (sa->sa_family == AF_INET6) {
+			if (sk->sk_family != AF_INET6) {
+				pr_warn("AF_INET6 address on AF_INET socket\n");
+				return -ENOPROTOOPT;
+			}
+			return udpv6_sendmsg(sk, msg, len);
+		}
+	}
+	return udp_sendmsg(sk, msg, len);
+}
+
+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_txbuf *txb,
+				 u16 *_rwind)
+{
+	struct rxrpc_ackinfo ackinfo;
+	unsigned int qsize, sack, wrap, to;
+	rxrpc_seq_t window, wtop;
+	int rsize;
+	u32 mtu, jmax;
+	u8 *ackp = txb->acks;
+
+	call->ackr_nr_unacked = 0;
+	atomic_set(&call->ackr_nr_consumed, 0);
+	rxrpc_inc_stat(call->rxnet, stat_tx_ack_fill);
+	clear_bit(RXRPC_CALL_RX_IS_IDLE, &call->flags);
+
+	window = call->ackr_window;
+	wtop   = call->ackr_wtop;
+	sack   = call->ackr_sack_base % RXRPC_SACK_SIZE;
+	txb->ack.firstPacket = htonl(window);
+	txb->ack.nAcks = wtop - window;
+
+	if (after(wtop, window)) {
+		wrap = RXRPC_SACK_SIZE - sack;
+		to = min_t(unsigned int, txb->ack.nAcks, RXRPC_SACK_SIZE);
+
+		if (sack + txb->ack.nAcks <= RXRPC_SACK_SIZE) {
+			memcpy(txb->acks, call->ackr_sack_table + sack, txb->ack.nAcks);
+		} else {
+			memcpy(txb->acks, call->ackr_sack_table + sack, wrap);
+			memcpy(txb->acks + wrap, call->ackr_sack_table,
+			       to - wrap);
+		}
+
+		ackp += to;
+	} else if (before(wtop, window)) {
+		pr_warn("ack window backward %x %x", window, wtop);
+	} else if (txb->ack.reason == RXRPC_ACK_DELAY) {
+		txb->ack.reason = RXRPC_ACK_IDLE;
+	}
+
+	mtu = conn->peer->if_mtu;
+	mtu -= conn->peer->hdrsize;
+	jmax = rxrpc_rx_jumbo_max;
+	qsize = (window - 1) - call->rx_consumed;
+	rsize = max_t(int, call->rx_winsize - qsize, 0);
+	*_rwind = rsize;
+	ackinfo.rxMTU		= htonl(rxrpc_rx_mtu);
+	ackinfo.maxMTU		= htonl(mtu);
+	ackinfo.rwind		= htonl(rsize);
+	ackinfo.jumbo_max	= htonl(jmax);
+
+	*ackp++ = 0;
+	*ackp++ = 0;
+	*ackp++ = 0;
+	memcpy(ackp, &ackinfo, sizeof(ackinfo));
+	return txb->ack.nAcks + 3 + sizeof(ackinfo);
+}
+
+/*
+ * Record the beginning of an RTT probe.
+ */
+static int rxrpc_begin_rtt_probe(struct rxrpc_call *call, rxrpc_serial_t serial,
+				 enum rxrpc_rtt_tx_trace why)
+{
+	unsigned long avail = call->rtt_avail;
+	int rtt_slot = 9;
+
+	if (!(avail & RXRPC_CALL_RTT_AVAIL_MASK))
+		goto no_slot;
+
+	rtt_slot = __ffs(avail & RXRPC_CALL_RTT_AVAIL_MASK);
+	if (!test_and_clear_bit(rtt_slot, &call->rtt_avail))
+		goto no_slot;
+
+	call->rtt_serial[rtt_slot] = serial;
+	call->rtt_sent_at[rtt_slot] = ktime_get_real();
+	smp_wmb(); /* Write data before avail bit */
+	set_bit(rtt_slot + RXRPC_CALL_RTT_PEND_SHIFT, &call->rtt_avail);
+
+	trace_rxrpc_rtt_tx(call, why, rtt_slot, serial);
+	return rtt_slot;
+
+no_slot:
+	trace_rxrpc_rtt_tx(call, rxrpc_rtt_tx_no_slot, rtt_slot, serial);
+	return -1;
+}
+
+/*
+ * Cancel an RTT probe.
+ */
+static void rxrpc_cancel_rtt_probe(struct rxrpc_call *call,
+				   rxrpc_serial_t serial, int rtt_slot)
+{
+	if (rtt_slot != -1) {
+		clear_bit(rtt_slot + RXRPC_CALL_RTT_PEND_SHIFT, &call->rtt_avail);
+		smp_wmb(); /* Clear pending bit before setting slot */
+		set_bit(rtt_slot, &call->rtt_avail);
+		trace_rxrpc_rtt_tx(call, rxrpc_rtt_tx_cancel, rtt_slot, serial);
+	}
+}
+
+/*
+ * Transmit an ACK packet.
+ */
+int rxrpc_send_ack_packet(struct rxrpc_call *call, struct rxrpc_txbuf *txb)
+{
+	struct rxrpc_connection *conn;
+	struct msghdr msg;
+	struct kvec iov[1];
+	rxrpc_serial_t serial;
+	size_t len, n;
+	int ret, rtt_slot = -1;
+	u16 rwind;
+
+	if (test_bit(RXRPC_CALL_DISCONNECTED, &call->flags))
+		return -ECONNRESET;
+
+	conn = call->conn;
+
+	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 (txb->ack.reason == RXRPC_ACK_PING)
+		txb->wire.flags |= RXRPC_REQUEST_ACK;
+
+	n = rxrpc_fill_out_ack(conn, call, txb, &rwind);
+	if (n == 0)
+		return 0;
+
+	iov[0].iov_base	= &txb->wire;
+	iov[0].iov_len	= sizeof(txb->wire) + sizeof(txb->ack) + n;
+	len = iov[0].iov_len;
+
+	serial = atomic_inc_return(&conn->serial);
+	txb->wire.serial = htonl(serial);
+	trace_rxrpc_tx_ack(call->debug_id, serial,
+			   ntohl(txb->ack.firstPacket),
+			   ntohl(txb->ack.serial), txb->ack.reason, txb->ack.nAcks,
+			   rwind);
+
+	if (txb->ack.reason == RXRPC_ACK_PING)
+		rtt_slot = rxrpc_begin_rtt_probe(call, serial, rxrpc_rtt_tx_ping);
+
+	rxrpc_inc_stat(call->rxnet, stat_tx_ack_send);
+
+	/* Grab the highest received seq as late as possible */
+	txb->ack.previousPacket	= htonl(call->rx_highest_seq);
+
+	iov_iter_kvec(&msg.msg_iter, WRITE, iov, 1, len);
+	ret = do_udp_sendmsg(conn->local->socket, &msg, len);
+	call->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, &txb->wire,
+				      rxrpc_tx_point_call_ack);
+		if (txb->wire.flags & RXRPC_REQUEST_ACK)
+			call->peer->rtt_last_req = ktime_get_real();
+	}
+	rxrpc_tx_backoff(call, ret);
+
+	if (!__rxrpc_call_is_complete(call)) {
+		if (ret < 0)
+			rxrpc_cancel_rtt_probe(call, serial, rtt_slot);
+		rxrpc_set_keepalive(call);
+	}
+
+	return ret;
+}
+
+/*
+ * Send an ABORT call packet.
+ */
+int rxrpc_send_abort_packet(struct rxrpc_call *call)
+{
+	struct rxrpc_connection *conn;
+	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_ALL_ACKED, &call->flags))
+		return 0;
+
+	if (test_bit(RXRPC_CALL_DISCONNECTED, &call->flags))
+		return -ECONNRESET;
+
+	conn = call->conn;
+
+	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->dest_srx.srx_service);
+	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);
+
+	iov_iter_kvec(&msg.msg_iter, WRITE, iov, 1, sizeof(pkt));
+	ret = do_udp_sendmsg(conn->local->socket, &msg, sizeof(pkt));
+	conn->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);
+	return ret;
+}
+
+/*
+ * send a packet through the transport endpoint
+ */
+int rxrpc_send_data_packet(struct rxrpc_call *call, struct rxrpc_txbuf *txb)
+{
+	enum rxrpc_req_ack_trace why;
+	struct rxrpc_connection *conn = call->conn;
+	struct msghdr msg;
+	struct kvec iov[1];
+	rxrpc_serial_t serial;
+	size_t len;
+	int ret, rtt_slot = -1;
+
+	_enter("%x,{%d}", txb->seq, txb->len);
+
+	/* Each transmission of a Tx packet needs a new serial number */
+	serial = atomic_inc_return(&conn->serial);
+	txb->wire.serial = htonl(serial);
+
+	if (test_bit(RXRPC_CONN_PROBING_FOR_UPGRADE, &conn->flags) &&
+	    txb->seq == 1)
+		txb->wire.userStatus = RXRPC_USERSTATUS_SERVICE_UPGRADE;
+
+	iov[0].iov_base = &txb->wire;
+	iov[0].iov_len = sizeof(txb->wire) + txb->len;
+	len = iov[0].iov_len;
+	iov_iter_kvec(&msg.msg_iter, WRITE, iov, 1, 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 (txb->wire.flags & RXRPC_REQUEST_ACK)
+		why = rxrpc_reqack_already_on;
+	else if (test_bit(RXRPC_TXBUF_LAST, &txb->flags) && rxrpc_sending_to_client(txb))
+		why = rxrpc_reqack_no_srv_last;
+	else if (test_and_clear_bit(RXRPC_CALL_EV_ACK_LOST, &call->events))
+		why = rxrpc_reqack_ack_lost;
+	else if (test_bit(RXRPC_TXBUF_RESENT, &txb->flags))
+		why = rxrpc_reqack_retrans;
+	else if (call->cong_mode == RXRPC_CALL_SLOW_START && call->cong_cwnd <= 2)
+		why = rxrpc_reqack_slow_start;
+	else if (call->tx_winsize <= 2)
+		why = rxrpc_reqack_small_txwin;
+	else if (call->peer->rtt_count < 3 && txb->seq & 1)
+		why = rxrpc_reqack_more_rtt;
+	else if (ktime_before(ktime_add_ms(call->peer->rtt_last_req, 1000), ktime_get_real()))
+		why = rxrpc_reqack_old_rtt;
+	else
+		goto dont_set_request_ack;
+
+	rxrpc_inc_stat(call->rxnet, stat_why_req_ack[why]);
+	trace_rxrpc_req_ack(call->debug_id, txb->seq, why);
+	if (why != rxrpc_reqack_no_srv_last)
+		txb->wire.flags |= RXRPC_REQUEST_ACK;
+dont_set_request_ack:
+
+	if (IS_ENABLED(CONFIG_AF_RXRPC_INJECT_LOSS)) {
+		static int lose;
+		if ((lose++ & 7) == 7) {
+			ret = 0;
+			trace_rxrpc_tx_data(call, txb->seq, serial,
+					    txb->wire.flags,
+					    test_bit(RXRPC_TXBUF_RESENT, &txb->flags),
+					    true);
+			goto done;
+		}
+	}
+
+	trace_rxrpc_tx_data(call, txb->seq, serial, txb->wire.flags,
+			    test_bit(RXRPC_TXBUF_RESENT, &txb->flags), false);
+
+	/* Track what we've attempted to transmit at least once so that the
+	 * retransmission algorithm doesn't try to resend what we haven't sent
+	 * yet.  However, this can race as we can receive an ACK before we get
+	 * to this point.  But, OTOH, if we won't get an ACK mentioning this
+	 * packet unless the far side received it (though it could have
+	 * discarded it anyway and NAK'd it).
+	 */
+	cmpxchg(&call->tx_transmitted, txb->seq - 1, txb->seq);
+
+	/* send the packet with the don't fragment bit set if we currently
+	 * think it's small enough */
+	if (txb->len >= call->peer->maxdata)
+		goto send_fragmentable;
+
+	txb->last_sent = ktime_get_real();
+	if (txb->wire.flags & RXRPC_REQUEST_ACK)
+		rtt_slot = rxrpc_begin_rtt_probe(call, serial, rxrpc_rtt_tx_data);
+
+	/* 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
+	 */
+	rxrpc_inc_stat(call->rxnet, stat_tx_data_send);
+	ret = do_udp_sendmsg(conn->local->socket, &msg, len);
+	conn->peer->last_tx_at = ktime_get_seconds();
+
+	if (ret < 0) {
+		rxrpc_inc_stat(call->rxnet, stat_tx_data_send_fail);
+		rxrpc_cancel_rtt_probe(call, serial, rtt_slot);
+		trace_rxrpc_tx_fail(call->debug_id, serial, ret,
+				    rxrpc_tx_point_call_data_nofrag);
+	} else {
+		trace_rxrpc_tx_packet(call->debug_id, &txb->wire,
+				      rxrpc_tx_point_call_data_nofrag);
+	}
+
+	rxrpc_tx_backoff(call, ret);
+	if (ret == -EMSGSIZE)
+		goto send_fragmentable;
+
+done:
+	if (ret >= 0) {
+		call->tx_last_sent = txb->last_sent;
+		if (txb->wire.flags & RXRPC_REQUEST_ACK) {
+			call->peer->rtt_last_req = txb->last_sent;
+			if (call->peer->rtt_count > 1) {
+				unsigned long nowj = jiffies, ack_lost_at;
+
+				ack_lost_at = rxrpc_get_rto_backoff(call->peer, false);
+				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 (txb->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");
+
+	txb->last_sent = ktime_get_real();
+	if (txb->wire.flags & RXRPC_REQUEST_ACK)
+		rtt_slot = rxrpc_begin_rtt_probe(call, serial, rxrpc_rtt_tx_data);
+
+	switch (conn->local->srx.transport.family) {
+	case AF_INET6:
+	case AF_INET:
+		rxrpc_local_dont_fragment(conn->local, false);
+		rxrpc_inc_stat(call->rxnet, stat_tx_data_send_frag);
+		ret = do_udp_sendmsg(conn->local->socket, &msg, len);
+		conn->peer->last_tx_at = ktime_get_seconds();
+
+		rxrpc_local_dont_fragment(conn->local, true);
+		break;
+
+	default:
+		BUG();
+	}
+
+	if (ret < 0) {
+		rxrpc_inc_stat(call->rxnet, stat_tx_data_send_fail);
+		rxrpc_cancel_rtt_probe(call, serial, rtt_slot);
+		trace_rxrpc_tx_fail(call->debug_id, serial, ret,
+				    rxrpc_tx_point_call_data_frag);
+	} else {
+		trace_rxrpc_tx_packet(call->debug_id, &txb->wire,
+				      rxrpc_tx_point_call_data_frag);
+	}
+	rxrpc_tx_backoff(call, ret);
+	goto done;
+}
+
+/*
+ * Transmit a connection-level abort.
+ */
+void rxrpc_send_conn_abort(struct rxrpc_connection *conn)
+{
+	struct rxrpc_wire_header whdr;
+	struct msghdr msg;
+	struct kvec iov[2];
+	__be32 word;
+	size_t len;
+	u32 serial;
+	int ret;
+
+	msg.msg_name	= &conn->peer->srx.transport;
+	msg.msg_namelen	= conn->peer->srx.transport_len;
+	msg.msg_control	= NULL;
+	msg.msg_controllen = 0;
+	msg.msg_flags	= 0;
+
+	whdr.epoch	= htonl(conn->proto.epoch);
+	whdr.cid	= htonl(conn->proto.cid);
+	whdr.callNumber	= 0;
+	whdr.seq	= 0;
+	whdr.type	= RXRPC_PACKET_TYPE_ABORT;
+	whdr.flags	= conn->out_clientflag;
+	whdr.userStatus	= 0;
+	whdr.securityIndex = conn->security_ix;
+	whdr._rsvd	= 0;
+	whdr.serviceId	= htons(conn->service_id);
+
+	word		= htonl(conn->abort_code);
+
+	iov[0].iov_base	= &whdr;
+	iov[0].iov_len	= sizeof(whdr);
+	iov[1].iov_base	= &word;
+	iov[1].iov_len	= sizeof(word);
+
+	len = iov[0].iov_len + iov[1].iov_len;
+
+	serial = atomic_inc_return(&conn->serial);
+	whdr.serial = htonl(serial);
+
+	iov_iter_kvec(&msg.msg_iter, WRITE, iov, 2, len);
+	ret = do_udp_sendmsg(conn->local->socket, &msg, len);
+	if (ret < 0) {
+		trace_rxrpc_tx_fail(conn->debug_id, serial, ret,
+				    rxrpc_tx_point_conn_abort);
+		_debug("sendmsg failed: %d", ret);
+		return;
+	}
+
+	trace_rxrpc_tx_packet(conn->debug_id, &whdr, rxrpc_tx_point_conn_abort);
+
+	conn->peer->last_tx_at = ktime_get_seconds();
+}
+
+/*
+ * Reject a packet through the local endpoint.
+ */
+void rxrpc_reject_packet(struct rxrpc_local *local, struct sk_buff *skb)
+{
+	struct rxrpc_wire_header whdr;
+	struct sockaddr_rxrpc srx;
+	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
+	struct msghdr msg;
+	struct kvec iov[2];
+	size_t size;
+	__be32 code;
+	int ret, ioc;
+
+	rxrpc_see_skb(skb, rxrpc_skb_see_reject);
+
+	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));
+
+	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:
+		return;
+	}
+
+	if (rxrpc_extract_addr_from_skb(&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;
+
+		iov_iter_kvec(&msg.msg_iter, WRITE, iov, ioc, size);
+		ret = do_udp_sendmsg(local->socket, &msg, 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);
+	}
+}
+
+/*
+ * 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;
+
+	iov_iter_kvec(&msg.msg_iter, WRITE, iov, 2, len);
+	ret = do_udp_sendmsg(peer->local->socket, &msg, 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("");
+}
+
+/*
+ * Schedule an instant Tx resend.
+ */
+static inline void rxrpc_instant_resend(struct rxrpc_call *call,
+					struct rxrpc_txbuf *txb)
+{
+	if (!__rxrpc_call_is_complete(call))
+		kdebug("resend");
+}
+
+/*
+ * Transmit one packet.
+ */
+void rxrpc_transmit_one(struct rxrpc_call *call, struct rxrpc_txbuf *txb)
+{
+	int ret;
+
+	ret = rxrpc_send_data_packet(call, txb);
+	if (ret < 0) {
+		switch (ret) {
+		case -ENETUNREACH:
+		case -EHOSTUNREACH:
+		case -ECONNREFUSED:
+			rxrpc_set_call_completion(call, RXRPC_CALL_LOCAL_ERROR,
+						  0, ret);
+			break;
+		default:
+			_debug("need instant resend %d", ret);
+			rxrpc_instant_resend(call, txb);
+		}
+	} else {
+		unsigned long now = jiffies;
+		unsigned long resend_at = now + call->peer->rto_j;
+
+		WRITE_ONCE(call->resend_at, resend_at);
+		rxrpc_reduce_call_timer(call, resend_at, now,
+					rxrpc_timer_set_for_send);
+	}
+}