can: gw: indicate and count deleted frames due to misconfiguration

Add a statistic counter to detect deleted frames due to misconfiguration with
a new read-only CGW_DELETED netlink attribute for the CAN gateway.

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

2 files changed, 12 insertions, 1 deletions

diff --git a/include/uapi/linux/can/gw.h b/include/uapi/linux/can/gw.h
index 0505c7f86213..ae07bec74f4b 100644
--- a/include/uapi/linux/can/gw.h
+++ b/include/uapi/linux/can/gw.h
@@ -44,6 +44,7 @@ enum {
         CGW_SRC_IF,     /* ifindex of source network interface */
         CGW_DST_IF,     /* ifindex of destination network interface */
         CGW_FILTER,     /* specify struct can_filter on source CAN device */
+        CGW_DELETED,    /* number of deleted CAN frames (see max_hops param) */
         __CGW_MAX
 };
 
diff --git a/net/can/gw.c b/net/can/gw.c
index 4216a80618cb..acdd4656cc3b 100644
--- a/net/can/gw.c
+++ b/net/can/gw.c
@@ -131,6 +131,7 @@ struct cgw_job {
         struct rcu_head rcu;
         u32 handled_frames;
         u32 dropped_frames;
+        u32 deleted_frames;
         struct cf_mod mod;
         union {
                 /* CAN frame data source */
@@ -367,8 +368,11 @@ static void can_can_gw_rcv(struct sk_buff *skb, void *data)
 
         BUG_ON(skb->ip_summed != CHECKSUM_UNNECESSARY);
 
-        if (cgw_hops(skb) >= max_hops)
+        if (cgw_hops(skb) >= max_hops) {
+                /* indicate deleted frames due to misconfiguration */
+                gwj->deleted_frames++;
                 return;
+        }
 
         if (!(gwj->dst.dev->flags & IFF_UP)) {
                 gwj->dropped_frames++;
@@ -500,6 +504,11 @@ static int cgw_put_job(struct sk_buff *skb, struct cgw_job *gwj, int type,
                         goto cancel;
         }
 
+        if (gwj->deleted_frames) {
+                if (nla_put_u32(skb, CGW_DELETED, gwj->deleted_frames) < 0)
+                        goto cancel;
+        }
+
         /* check non default settings of attributes */
 
         if (gwj->mod.modtype.and) {
@@ -799,6 +808,7 @@ static int cgw_create_job(struct sk_buff *skb,  struct nlmsghdr *nlh,
 
         gwj->handled_frames = 0;
         gwj->dropped_frames = 0;
+        gwj->deleted_frames = 0;
         gwj->flags = r->flags;
         gwj->gwtype = r->gwtype;