netdev - [net 14/27] can: isotp: isotp_rcv_cf(): enable RX timeout handling in listen-only mode

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Date:   Tue,  3 Nov 2020 23:06:23 +0100
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     netdev@...r.kernel.org
Cc:     davem@...emloft.net, kuba@...nel.org, linux-can@...r.kernel.org,
        kernel@...gutronix.de, Oliver Hartkopp <socketcan@...tkopp.net>,
        Thomas Wagner <thwa1@....de>,
        Marc Kleine-Budde <mkl@...gutronix.de>
Subject: [net 14/27] can: isotp: isotp_rcv_cf(): enable RX timeout handling in listen-only mode

From: Oliver Hartkopp <socketcan@...tkopp.net>

As reported by Thomas Wagner:

    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@....de>
Signed-off-by: Oliver Hartkopp <socketcan@...tkopp.net>
Fixes: e057dd3fc20f ("can: add ISO 15765-2:2016 transport protocol")
Link: https://github.com/hartkopp/can-isotp/issues/34
Link: https://lore.kernel.org/r/20201019120229.89326-1-socketcan@hartkopp.net
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
---
 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
@@ -569,10 +569,6 @@ static int isotp_rcv_cf(struct sock *sk, struct canfd_frame *cf, int ae,
 		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 */
@@ -581,6 +577,10 @@ static int isotp_rcv_cf(struct sock *sk, struct canfd_frame *cf, int ae,
 		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