can: isotp: add SF_BROADCAST support for functional addressing

can: isotp: add SF_BROADCAST support for functional addressing

When CAN_ISOTP_SF_BROADCAST is set in the CAN_ISOTP_OPTS flags the CAN_ISOTP
socket is switched into functional addressing mode, where only single frame
(SF) protocol data units can be send on the specified CAN interface and the
given tp.tx_id after bind().

In opposite to normal and extended addressing this socket does not register a
CAN-ID for reception which would be needed for a 1-to-1 ISOTP connection with a
segmented bi-directional data transfer.

Sending SFs on this socket is therefore a TX-only 'broadcast' operation.

Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Thomas Wagner <thwa1@web.de>
Link: https://lore.kernel.org/r/20201206144731.4609-1-socketcan@hartkopp.net
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>