diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h
index 45307463b7dd..a6e6cae82c30 100644
--- a/net/rxrpc/ar-internal.h
+++ b/net/rxrpc/ar-internal.h
@@ -302,6 +302,7 @@ struct rxrpc_peer {
 
 	/* calculated RTT cache */
 #define RXRPC_RTT_CACHE_SIZE 32
+	spinlock_t		rtt_input_lock;	/* RTT lock for input routine */
 	ktime_t			rtt_last_req;	/* Time of last RTT request */
 	u64			rtt;		/* Current RTT estimate (in nS) */
 	u64			rtt_sum;	/* Sum of cache contents */
@@ -447,7 +448,7 @@ struct rxrpc_connection {
 	atomic_t		serial;		/* packet serial number counter */
 	unsigned int		hi_serial;	/* highest serial number received */
 	u32			security_nonce;	/* response re-use preventer */
-	u16			service_id;	/* Service ID, possibly upgraded */
+	u32			service_id;	/* Service ID, possibly upgraded */
 	u8			size_align;	/* data size alignment (for security) */
 	u8			security_size;	/* security header size */
 	u8			security_ix;	/* security type */
@@ -635,6 +636,8 @@ struct rxrpc_call {
 	bool			tx_phase;	/* T if transmission phase, F if receive phase */
 	u8			nr_jumbo_bad;	/* Number of jumbo dups/exceeds-windows */
 
+	spinlock_t		input_lock;	/* Lock for packet input to this call */
+
 	/* receive-phase ACK management */
 	u8			ackr_reason;	/* reason to ACK */
 	u16			ackr_skew;	/* skew on packet being ACK'd */
@@ -720,8 +723,6 @@ int rxrpc_service_prealloc(struct rxrpc_sock *, gfp_t);
 void rxrpc_discard_prealloc(struct rxrpc_sock *);
 struct rxrpc_call *rxrpc_new_incoming_call(struct rxrpc_local *,
 					   struct rxrpc_sock *,
-					   struct rxrpc_peer *,
-					   struct rxrpc_connection *,
 					   struct sk_buff *);
 void rxrpc_accept_incoming_calls(struct rxrpc_local *);
 struct rxrpc_call *rxrpc_accept_call(struct rxrpc_sock *, unsigned long,
diff --git a/net/rxrpc/call_accept.c b/net/rxrpc/call_accept.c
index 1c4ebc0cb25b..652e314de38e 100644
--- a/net/rxrpc/call_accept.c
+++ b/net/rxrpc/call_accept.c
@@ -333,11 +333,11 @@ static struct rxrpc_call *rxrpc_alloc_incoming_call(struct rxrpc_sock *rx,
  */
 struct rxrpc_call *rxrpc_new_incoming_call(struct rxrpc_local *local,
 					   struct rxrpc_sock *rx,
-					   struct rxrpc_peer *peer,
-					   struct rxrpc_connection *conn,
 					   struct sk_buff *skb)
 {
 	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
+	struct rxrpc_connection *conn;
+	struct rxrpc_peer *peer;
 	struct rxrpc_call *call;
 
 	_enter("");
@@ -354,6 +354,13 @@ struct rxrpc_call *rxrpc_new_incoming_call(struct rxrpc_local *local,
 		goto out;
 	}
 
+	/* The peer, connection and call may all have sprung into existence due
+	 * to a duplicate packet being handled on another CPU in parallel, so
+	 * we have to recheck the routing.  However, we're now holding
+	 * rx->incoming_lock, so the values should remain stable.
+	 */
+	conn = rxrpc_find_connection_rcu(local, skb, &peer);
+
 	call = rxrpc_alloc_incoming_call(rx, local, peer, conn, skb);
 	if (!call) {
 		skb->mark = RXRPC_SKB_MARK_REJECT_BUSY;
@@ -396,10 +403,12 @@ struct rxrpc_call *rxrpc_new_incoming_call(struct rxrpc_local *local,
 
 	case RXRPC_CONN_SERVICE:
 		write_lock(&call->state_lock);
-		if (rx->discard_new_call)
-			call->state = RXRPC_CALL_SERVER_RECV_REQUEST;
-		else
-			call->state = RXRPC_CALL_SERVER_ACCEPTING;
+		if (call->state < RXRPC_CALL_COMPLETE) {
+			if (rx->discard_new_call)
+				call->state = RXRPC_CALL_SERVER_RECV_REQUEST;
+			else
+				call->state = RXRPC_CALL_SERVER_ACCEPTING;
+		}
 		write_unlock(&call->state_lock);
 		break;
 
diff --git a/net/rxrpc/call_object.c b/net/rxrpc/call_object.c
index 0ca2c2dfd196..8f1a8f85b1f9 100644
--- a/net/rxrpc/call_object.c
+++ b/net/rxrpc/call_object.c
@@ -138,6 +138,7 @@ struct rxrpc_call *rxrpc_alloc_call(struct rxrpc_sock *rx, gfp_t gfp,
 	init_waitqueue_head(&call->waitq);
 	spin_lock_init(&call->lock);
 	spin_lock_init(&call->notify_lock);
+	spin_lock_init(&call->input_lock);
 	rwlock_init(&call->state_lock);
 	atomic_set(&call->usage, 1);
 	call->debug_id = debug_id;
diff --git a/net/rxrpc/input.c b/net/rxrpc/input.c
index 04213a65c1ac..570b49d2da42 100644
--- a/net/rxrpc/input.c
+++ b/net/rxrpc/input.c
@@ -459,13 +459,15 @@ static void rxrpc_input_data(struct rxrpc_call *call, struct sk_buff *skb,
 		}
 	}
 
+	spin_lock(&call->input_lock);
+
 	/* Received data implicitly ACKs all of the request packets we sent
 	 * when we're acting as a client.
 	 */
 	if ((state == RXRPC_CALL_CLIENT_SEND_REQUEST ||
 	     state == RXRPC_CALL_CLIENT_AWAIT_REPLY) &&
 	    !rxrpc_receiving_reply(call))
-		return;
+		goto unlock;
 
 	call->ackr_prev_seq = seq;
 
@@ -495,12 +497,16 @@ next_subpacket:
 
 	if (flags & RXRPC_LAST_PACKET) {
 		if (test_bit(RXRPC_CALL_RX_LAST, &call->flags) &&
-		    seq != call->rx_top)
-			return rxrpc_proto_abort("LSN", call, seq);
+		    seq != call->rx_top) {
+			rxrpc_proto_abort("LSN", call, seq);
+			goto unlock;
+		}
 	} else {
 		if (test_bit(RXRPC_CALL_RX_LAST, &call->flags) &&
-		    after_eq(seq, call->rx_top))
-			return rxrpc_proto_abort("LSA", call, seq);
+		    after_eq(seq, call->rx_top)) {
+			rxrpc_proto_abort("LSA", call, seq);
+			goto unlock;
+		}
 	}
 
 	trace_rxrpc_rx_data(call->debug_id, seq, serial, flags, annotation);
@@ -567,8 +573,10 @@ next_subpacket:
 skip:
 	offset += len;
 	if (flags & RXRPC_JUMBO_PACKET) {
-		if (skb_copy_bits(skb, offset, &flags, 1) < 0)
-			return rxrpc_proto_abort("XJF", call, seq);
+		if (skb_copy_bits(skb, offset, &flags, 1) < 0) {
+			rxrpc_proto_abort("XJF", call, seq);
+			goto unlock;
+		}
 		offset += sizeof(struct rxrpc_jumbo_header);
 		seq++;
 		serial++;
@@ -608,6 +616,9 @@ ack:
 		trace_rxrpc_notify_socket(call->debug_id, serial);
 		rxrpc_notify_socket(call);
 	}
+
+unlock:
+	spin_unlock(&call->input_lock);
 	_leave(" [queued]");
 }
 
@@ -694,15 +705,14 @@ static void rxrpc_input_ping_response(struct rxrpc_call *call,
 
 	ping_time = call->ping_time;
 	smp_rmb();
-	ping_serial = call->ping_serial;
+	ping_serial = READ_ONCE(call->ping_serial);
 
 	if (orig_serial == call->acks_lost_ping)
 		rxrpc_input_check_for_lost_ack(call);
 
-	if (!test_bit(RXRPC_CALL_PINGING, &call->flags) ||
-	    before(orig_serial, ping_serial))
+	if (before(orig_serial, ping_serial) ||
+	    !test_and_clear_bit(RXRPC_CALL_PINGING, &call->flags))
 		return;
-	clear_bit(RXRPC_CALL_PINGING, &call->flags);
 	if (after(orig_serial, ping_serial))
 		return;
 
@@ -869,24 +879,31 @@ static void rxrpc_input_ack(struct rxrpc_call *call, struct sk_buff *skb,
 	}
 
 	/* Discard any out-of-order or duplicate ACKs. */
-	if (before_eq(sp->hdr.serial, call->acks_latest)) {
-		_debug("discard ACK %d <= %d",
-		       sp->hdr.serial, call->acks_latest);
+	if (before_eq(sp->hdr.serial, call->acks_latest))
 		return;
-	}
+
+	buf.info.rxMTU = 0;
+	ioffset = offset + nr_acks + 3;
+	if (skb->len >= ioffset + sizeof(buf.info) &&
+	    skb_copy_bits(skb, ioffset, &buf.info, sizeof(buf.info)) < 0)
+		return rxrpc_proto_abort("XAI", call, 0);
+
+	spin_lock(&call->input_lock);
+
+	/* Discard any out-of-order or duplicate ACKs. */
+	if (before_eq(sp->hdr.serial, call->acks_latest))
+		goto out;
 	call->acks_latest_ts = skb->tstamp;
 	call->acks_latest = sp->hdr.serial;
 
 	/* Parse rwind and mtu sizes if provided. */
-	ioffset = offset + nr_acks + 3;
-	if (skb->len >= ioffset + sizeof(buf.info)) {
-		if (skb_copy_bits(skb, ioffset, &buf.info, sizeof(buf.info)) < 0)
-			return rxrpc_proto_abort("XAI", call, 0);
+	if (buf.info.rxMTU)
 		rxrpc_input_ackinfo(call, skb, &buf.info);
-	}
 
-	if (first_soft_ack == 0)
-		return rxrpc_proto_abort("AK0", call, 0);
+	if (first_soft_ack == 0) {
+		rxrpc_proto_abort("AK0", call, 0);
+		goto out;
+	}
 
 	/* Ignore ACKs unless we are or have just been transmitting. */
 	switch (READ_ONCE(call->state)) {
@@ -896,25 +913,31 @@ static void rxrpc_input_ack(struct rxrpc_call *call, struct sk_buff *skb,
 	case RXRPC_CALL_SERVER_AWAIT_ACK:
 		break;
 	default:
-		return;
+		goto out;
 	}
 
 	if (before(hard_ack, call->tx_hard_ack) ||
-	    after(hard_ack, call->tx_top))
-		return rxrpc_proto_abort("AKW", call, 0);
-	if (nr_acks > call->tx_top - hard_ack)
-		return rxrpc_proto_abort("AKN", call, 0);
+	    after(hard_ack, call->tx_top)) {
+		rxrpc_proto_abort("AKW", call, 0);
+		goto out;
+	}
+	if (nr_acks > call->tx_top - hard_ack) {
+		rxrpc_proto_abort("AKN", call, 0);
+		goto out;
+	}
 
 	if (after(hard_ack, call->tx_hard_ack)) {
 		if (rxrpc_rotate_tx_window(call, hard_ack, &summary)) {
 			rxrpc_end_tx_phase(call, false, "ETA");
-			return;
+			goto out;
 		}
 	}
 
 	if (nr_acks > 0) {
-		if (skb_copy_bits(skb, offset, buf.acks, nr_acks) < 0)
-			return rxrpc_proto_abort("XSA", call, 0);
+		if (skb_copy_bits(skb, offset, buf.acks, nr_acks) < 0) {
+			rxrpc_proto_abort("XSA", call, 0);
+			goto out;
+		}
 		rxrpc_input_soft_acks(call, buf.acks, first_soft_ack, nr_acks,
 				      &summary);
 	}
@@ -927,7 +950,9 @@ static void rxrpc_input_ack(struct rxrpc_call *call, struct sk_buff *skb,
 				  false, true,
 				  rxrpc_propose_ack_ping_for_lost_reply);
 
-	return rxrpc_congestion_management(call, skb, &summary, acked_serial);
+	rxrpc_congestion_management(call, skb, &summary, acked_serial);
+out:
+	spin_unlock(&call->input_lock);
 }
 
 /*
@@ -940,8 +965,12 @@ static void rxrpc_input_ackall(struct rxrpc_call *call, struct sk_buff *skb)
 
 	_proto("Rx ACKALL %%%u", sp->hdr.serial);
 
+	spin_lock(&call->input_lock);
+
 	if (rxrpc_rotate_tx_window(call, call->tx_top, &summary))
 		rxrpc_end_tx_phase(call, false, "ETL");
+
+	spin_unlock(&call->input_lock);
 }
 
 /*
@@ -1024,18 +1053,19 @@ static void rxrpc_input_call_packet(struct rxrpc_call *call,
 }
 
 /*
- * Handle a new call on a channel implicitly completing the preceding call on
- * that channel.
+ * Handle a new service call on a channel implicitly completing the preceding
+ * call on that channel.  This does not apply to client conns.
  *
  * TODO: If callNumber > call_id + 1, renegotiate security.
  */
-static void rxrpc_input_implicit_end_call(struct rxrpc_connection *conn,
+static void rxrpc_input_implicit_end_call(struct rxrpc_sock *rx,
+					  struct rxrpc_connection *conn,
 					  struct rxrpc_call *call)
 {
 	switch (READ_ONCE(call->state)) {
 	case RXRPC_CALL_SERVER_AWAIT_ACK:
 		rxrpc_call_completed(call);
-		break;
+		/* Fall through */
 	case RXRPC_CALL_COMPLETE:
 		break;
 	default:
@@ -1043,11 +1073,13 @@ static void rxrpc_input_implicit_end_call(struct rxrpc_connection *conn,
 			set_bit(RXRPC_CALL_EV_ABORT, &call->events);
 			rxrpc_queue_call(call);
 		}
+		trace_rxrpc_improper_term(call);
 		break;
 	}
 
-	trace_rxrpc_improper_term(call);
+	spin_lock(&rx->incoming_lock);
 	__rxrpc_disconnect_call(conn, call);
+	spin_unlock(&rx->incoming_lock);
 	rxrpc_notify_socket(call);
 }
 
@@ -1244,10 +1276,16 @@ int rxrpc_input_packet(struct sock *udp_sk, struct sk_buff *skb)
 			goto wrong_security;
 
 		if (sp->hdr.serviceId != conn->service_id) {
-			if (!test_bit(RXRPC_CONN_PROBING_FOR_UPGRADE, &conn->flags) ||
-			    conn->service_id != conn->params.service_id)
+			int old_id;
+
+			if (!test_bit(RXRPC_CONN_PROBING_FOR_UPGRADE, &conn->flags))
+				goto reupgrade;
+			old_id = cmpxchg(&conn->service_id, conn->params.service_id,
+					 sp->hdr.serviceId);
+
+			if (old_id != conn->params.service_id &&
+			    old_id != sp->hdr.serviceId)
 				goto reupgrade;
-			conn->service_id = sp->hdr.serviceId;
 		}
 
 		if (sp->hdr.callNumber == 0) {
@@ -1305,7 +1343,7 @@ int rxrpc_input_packet(struct sock *udp_sk, struct sk_buff *skb)
 			if (rxrpc_to_client(sp))
 				goto reject_packet;
 			if (call)
-				rxrpc_input_implicit_end_call(conn, call);
+				rxrpc_input_implicit_end_call(rx, conn, call);
 			call = NULL;
 		}
 
@@ -1325,7 +1363,7 @@ int rxrpc_input_packet(struct sock *udp_sk, struct sk_buff *skb)
 			goto bad_message;
 		if (sp->hdr.seq != 1)
 			goto discard;
-		call = rxrpc_new_incoming_call(local, rx, peer, conn, skb);
+		call = rxrpc_new_incoming_call(local, rx, skb);
 		if (!call)
 			goto reject_packet;
 		rxrpc_send_ping(call, skb, skew);
diff --git a/net/rxrpc/peer_event.c b/net/rxrpc/peer_event.c
index f3e6fc670da2..05b51bdbdd41 100644
--- a/net/rxrpc/peer_event.c
+++ b/net/rxrpc/peer_event.c
@@ -301,6 +301,8 @@ void rxrpc_peer_add_rtt(struct rxrpc_call *call, enum rxrpc_rtt_rx_trace why,
 	if (rtt < 0)
 		return;
 
+	spin_lock(&peer->rtt_input_lock);
+
 	/* Replace the oldest datum in the RTT buffer */
 	sum -= peer->rtt_cache[cursor];
 	sum += rtt;
@@ -312,6 +314,8 @@ void rxrpc_peer_add_rtt(struct rxrpc_call *call, enum rxrpc_rtt_rx_trace why,
 		peer->rtt_usage = usage;
 	}
 
+	spin_unlock(&peer->rtt_input_lock);
+
 	/* Now recalculate the average */
 	if (usage == RXRPC_RTT_CACHE_SIZE) {
 		avg = sum / RXRPC_RTT_CACHE_SIZE;
@@ -320,6 +324,7 @@ void rxrpc_peer_add_rtt(struct rxrpc_call *call, enum rxrpc_rtt_rx_trace why,
 		do_div(avg, usage);
 	}
 
+	/* Don't need to update this under lock */
 	peer->rtt = avg;
 	trace_rxrpc_rtt_rx(call, why, send_serial, resp_serial, rtt,
 			   usage, avg);
diff --git a/net/rxrpc/peer_object.c b/net/rxrpc/peer_object.c
index 2d39eaf19620..5691b7d266ca 100644
--- a/net/rxrpc/peer_object.c
+++ b/net/rxrpc/peer_object.c
@@ -225,6 +225,7 @@ struct rxrpc_peer *rxrpc_alloc_peer(struct rxrpc_local *local, gfp_t gfp)
 		peer->service_conns = RB_ROOT;
 		seqlock_init(&peer->service_conn_lock);
 		spin_lock_init(&peer->lock);
+		spin_lock_init(&peer->rtt_input_lock);
 		peer->debug_id = atomic_inc_return(&rxrpc_debug_id);
 
 		if (RXRPC_TX_SMSS > 2190)