can: isotp: remove re-binding of bound socket

As a carry over from the CAN_RAW socket (which allows to change the CAN
interface while mantaining the filter setup) the re-binding of the
CAN_ISOTP socket needs to take care about CAN ID address information and
subscriptions. It turned out that this feature is so limited (e.g. the
sockopts remain fix) that it finally has never been needed/used.

In opposite to the stateless CAN_RAW socket the switching of the CAN ID
subscriptions might additionally lead to an interrupted ongoing PDU
reception. So better remove this unneeded complexity.

Fixes: e057dd3f ("can: add ISO 15765-2:2016 transport protocol")
Link: https://lore.kernel.org/all/20220422082337.1676-1-socketcan@hartkopp.net
Cc: stable@vger.kernel.org
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

net/can/isotp.c

@@ -1189,6 +1189,11 @@ static int isotp_bind(struct socket *sock, struct sockaddr *uaddr, int len)
 
 	lock_sock(sk);
 
+	if (so->bound) {
+		err = -EINVAL;
+		goto out;
+	}
+
 	/* do not register frame reception for functional addressing */
 	if (so->opt.flags & CAN_ISOTP_SF_BROADCAST)
 		do_rx_reg = 0;
@@ -1199,10 +1204,6 @@ static int isotp_bind(struct socket *sock, struct sockaddr *uaddr, int len)
 		goto out;
 	}
 
-	if (so->bound && addr->can_ifindex == so->ifindex &&
-	    rx_id == so->rxid && tx_id == so->txid)
-		goto out;
-
 	dev = dev_get_by_index(net, addr->can_ifindex);
 	if (!dev) {
 		err = -ENODEV;
@@ -1237,22 +1238,6 @@ static int isotp_bind(struct socket *sock, struct sockaddr *uaddr, int len)
 
 	dev_put(dev);
 
-	if (so->bound && do_rx_reg) {
-		/* unregister old filter */
-		if (so->ifindex) {
-			dev = dev_get_by_index(net, so->ifindex);
-			if (dev) {
-				can_rx_unregister(net, dev, so->rxid,
-						  SINGLE_MASK(so->rxid),
-						  isotp_rcv, sk);
-				can_rx_unregister(net, dev, so->txid,
-						  SINGLE_MASK(so->txid),
-						  isotp_rcv_echo, sk);
-				dev_put(dev);
-			}
-		}
-	}
-
 	/* switch to new settings */
 	so->ifindex = ifindex;
 	so->rxid = rx_id;