[PATCH] can-isotp: enable RX timeout handling in listen-only mode

[Oliver Hartkopp <socketcan@hartkopp.net>]

As reported by Thomas Wagner here
https://github.com/hartkopp/can-isotp/issues/34
the timeout handling for data frames is not enabled when the isotp socket
is used in listen-only mode (sockopt CAN_ISOTP_LISTEN_MODE).
This mode is enabled by the isotpsniffer application which therefore
became inconsistend with the strict rx timeout rules when running the
isotp protocol in the operational mode.

This patch fixes this inconsistency by moving the return condition for the
listen-only mode behind the timeout handling code.

Reported-by: Thomas Wagner <thwa1@web.de>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
 net/can/isotp.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/can/isotp.c b/net/can/isotp.c
index 4c2062875893..a79287ef86da 100644
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -567,22 +567,22 @@ static int isotp_rcv_cf(struct sock *sk, struct canfd_frame *cf, int ae,
 		nskb->dev = skb->dev;
 		isotp_rcv_skb(nskb, sk);
 		return 0;
 	}
 
-	/* no creation of flow control frames */
-	if (so->opt.flags & CAN_ISOTP_LISTEN_MODE)
-		return 0;
-
 	/* perform blocksize handling, if enabled */
 	if (!so->rxfc.bs || ++so->rx.bs < so->rxfc.bs) {
 		/* start rx timeout watchdog */
 		hrtimer_start(&so->rxtimer, ktime_set(1, 0),
 			      HRTIMER_MODE_REL_SOFT);
 		return 0;
 	}
 
+	/* no creation of flow control frames */
+	if (so->opt.flags & CAN_ISOTP_LISTEN_MODE)
+		return 0;
+
 	/* we reached the specified blocksize so->rxfc.bs */
 	isotp_send_fc(sk, ae, ISOTP_FC_CTS);
 	return 0;
 }
 
-- 
2.28.0