can: isotp: support dynamic flow control parameters

The ISO15765-2 standard supports to take the PDUs communication parameters
blocksize (BS) and Separation Time minimum (STmin) either from the first
received flow control (FC) "static" or from every received FC "dynamic".

Add a new CAN_ISOTP_DYN_FC_PARMS flag to support dynamic FC parameters.

Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Link: https://lore.kernel.org/all/20231208165729.3011-1-socketcan@hartkopp.net
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

diff --git a/include/uapi/linux/can/isotp.h b/include/uapi/linux/can/isotp.h
index 439c982..6cde623 100644 (file)
--- a/include/uapi/linux/can/isotp.h
+++ b/include/uapi/linux/can/isotp.h
@@ -137,6 +137,7 @@ struct can_isotp_ll_options {
 #define CAN_ISOTP_WAIT_TX_DONE 0x0400  /* wait for tx completion */
 #define CAN_ISOTP_SF_BROADCAST 0x0800  /* 1-to-N functional addressing */
 #define CAN_ISOTP_CF_BROADCAST 0x1000  /* 1-to-N transmission w/o FC */
+#define CAN_ISOTP_DYN_FC_PARMS 0x2000  /* dynamic FC parameters BS/STmin */
 
 /* protocol machine default values */
 

diff --git a/net/can/isotp.c b/net/can/isotp.c
index d1c6f20..25bac0f 100644 (file)
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -381,8 +381,9 @@ static int isotp_rcv_fc(struct isotp_sock *so, struct canfd_frame *cf, int ae)
                return 1;
        }
 
-       /* get communication parameters only from the first FC frame */
-       if (so->tx.state == ISOTP_WAIT_FIRST_FC) {
+       /* get static/dynamic communication params from first/every FC frame */
+       if (so->tx.state == ISOTP_WAIT_FIRST_FC ||
+           so->opt.flags & CAN_ISOTP_DYN_FC_PARMS) {
                so->txfc.bs = cf->data[ae + 1];
                so->txfc.stmin = cf->data[ae + 2];