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-rw-r--r--net/can/j1939/address-claim.c40
1 files changed, 40 insertions, 0 deletions
diff --git a/net/can/j1939/address-claim.c b/net/can/j1939/address-claim.c
index f33c47327927..ca4ad6cdd5cb 100644
--- a/net/can/j1939/address-claim.c
+++ b/net/can/j1939/address-claim.c
@@ -165,6 +165,46 @@ static void j1939_ac_process(struct j1939_priv *priv, struct sk_buff *skb)
* 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);