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linux/net/can/j1939
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Devid Antonio Filoni c86e6d30c5 can: j1939: do not wait 250 ms if the same addr was already claimed 
commit 4ae5e1e97c upstream.

The ISO 11783-5 standard, in "4.5.2 - Address claim requirements", states:
  d) No CF shall begin, or resume, transmission on the network until 250
     ms after it has successfully claimed an address except when
     responding to a request for address-claimed.

But "Figure 6" and "Figure 7" in "4.5.4.2 - Address-claim
prioritization" show that the CF begins the transmission after 250 ms
from the first AC (address-claimed) message even if it sends another AC
message during that time window to resolve the address contention with
another CF.

As stated in "4.4.2.3 - Address-claimed message":
  In order to successfully claim an address, the CF sending an address
  claimed message shall not receive a contending claim from another CF
  for at least 250 ms.

As stated in "4.4.3.2 - NAME management (NM) message":
  1) A commanding CF can
     d) request that a CF with a specified NAME transmit the address-
        claimed message with its current NAME.
  2) A target CF shall
     d) send an address-claimed message in response to a request for a
        matching NAME

Taking the above arguments into account, the 250 ms wait is requested
only during network initialization.

Do not restart the timer on AC message if both the NAME and the address
match and so if the address has already been claimed (timer has expired)
or the AC message has been sent to resolve the contention with another
CF (timer is still running).

Signed-off-by: Devid Antonio Filoni <devid.filoni@egluetechnologies.com>
Acked-by: Oleksij Rempel <o.rempel@pengutronix.de>
Link: https://lore.kernel.org/all/20221125170418.34575-1-devid.filoni@egluetechnologies.com
Fixes: 9d71dd0c70 ("can: add support of SAE J1939 protocol")
Cc: stable@vger.kernel.org
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2023-02-14 19:11:42 +01:00
..
address-claim.c can: j1939: do not wait 250 ms if the same addr was already claimed 2023-02-14 19:11:42 +01:00
bus.c can: add support of SAE J1939 protocol 2019-09-04 14:22:33 +02:00
j1939-priv.h can: j1939: j1939_xtp_rx_rts_session_new(): abort TP less than 9 bytes 2021-10-17 14:12:57 +02:00
Kconfig can: add support of SAE J1939 protocol 2019-09-04 14:22:33 +02:00
main.c can: j1939: j1939_send_one(): fix missing CAN header initialization 2022-11-07 14:00:27 +01:00
Makefile can: add support of SAE J1939 protocol 2019-09-04 14:22:33 +02:00
socket.c can: j1939: j1939_sk_queue_activate_next_locked(): replace WARN_ON_ONCE with netdev_warn_once() 2022-08-09 09:05:06 +02:00
transport.c can: j1939: fix errant WARN_ON_ONCE in j1939_session_deactivate 2023-02-09 11:28:10 +01:00