can: gw: make routing to the incoming CAN interface configurable

Introduce new configuration flag CGW_FLAGS_CAN_IIF_TX_OK to configure if a
CAN sk_buff that has been routed with can-gw is allowed to be send back to
the originating CAN interface.

Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

2 files changed, 9 insertions, 0 deletions

diff --git a/include/uapi/linux/can/gw.h b/include/uapi/linux/can/gw.h
index 8e1db18c3cb6..0505c7f86213 100644
--- a/include/uapi/linux/can/gw.h
+++ b/include/uapi/linux/can/gw.h
@@ -51,6 +51,7 @@ enum {
 
 #define CGW_FLAGS_CAN_ECHO 0x01
 #define CGW_FLAGS_CAN_SRC_TSTAMP 0x02
+#define CGW_FLAGS_CAN_IIF_TX_OK 0x04
 
 #define CGW_MOD_FUNCS 4 /* AND OR XOR SET */
 
diff --git a/net/can/gw.c b/net/can/gw.c
index 574dda78eb0f..37a3efb7cc9d 100644
--- a/net/can/gw.c
+++ b/net/can/gw.c
@@ -52,6 +52,7 @@
 #include <linux/skbuff.h>
 #include <linux/can.h>
 #include <linux/can/core.h>
+#include <linux/can/skb.h>
 #include <linux/can/gw.h>
 #include <net/rtnetlink.h>
 #include <net/net_namespace.h>
@@ -347,6 +348,13 @@ static void can_can_gw_rcv(struct sk_buff *skb, void *data)
                 return;
         }
 
+        /* is sending the skb back to the incoming interface not allowed? */
+        if (!(gwj->flags & CGW_FLAGS_CAN_IIF_TX_OK) &&
+            skb_headroom(skb) == sizeof(struct can_skb_priv) &&
+            (((struct can_skb_priv *)(skb->head))->ifindex ==
+             gwj->dst.dev->ifindex))
+                return;
+
         /*
          * clone the given skb, which has not been done in can_rcv()
          *