This is a note to let you know that I've just added the patch titled can: j1939: do not wait 250 ms if the same addr was already claimed to the 5.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: can-j1939-do-not-wait-250-ms-if-the-same-addr-was-already-claimed.patch and it can be found in the queue-5.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 4ae5e1e97c44f4654516c1d41591a462ed62fa7b Mon Sep 17 00:00:00 2001 From: Devid Antonio Filoni <devid.filoni@xxxxxxxxxxxxxxxxxxxxx> Date: Fri, 25 Nov 2022 18:04:18 +0100 Subject: can: j1939: do not wait 250 ms if the same addr was already claimed From: Devid Antonio Filoni <devid.filoni@xxxxxxxxxxxxxxxxxxxxx> commit 4ae5e1e97c44f4654516c1d41591a462ed62fa7b 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@xxxxxxxxxxxxxxxxxxxxx> Acked-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx> Link: https://lore.kernel.org/all/20221125170418.34575-1-devid.filoni@xxxxxxxxxxxxxxxxxxxxx Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol") Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- net/can/j1939/address-claim.c | 40 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 40 insertions(+) --- a/net/can/j1939/address-claim.c +++ b/net/can/j1939/address-claim.c @@ -165,6 +165,46 @@ static void j1939_ac_process(struct j193 * leaving this function. */ ecu = j1939_ecu_get_by_name_locked(priv, name); + + if (ecu && ecu->addr == skcb->addr.sa) { + /* 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). + */ + goto out_ecu_put; + } + if (!ecu && j1939_address_is_unicast(skcb->addr.sa)) ecu = j1939_ecu_create_locked(priv, name); Patches currently in stable-queue which might be from devid.filoni@xxxxxxxxxxxxxxxxxxxxx are queue-5.15/can-j1939-do-not-wait-250-ms-if-the-same-addr-was-already-claimed.patch