tipc: add loopback device tracking

Since node internal messages are passed directly to the socket, it is not
possible to observe those messages via tcpdump or wireshark.

We now remedy this by making it possible to clone such messages and send
the clones to the loopback interface.  The clones are dropped at reception
and have no functional role except making the traffic visible.

The feature is enabled if network taps are active for the loopback device.
pcap filtering restrictions require the messages to be presented to the
receiving side of the loopback device.

v3 - Function dev_nit_active used to check for network taps.
   - Procedure netif_rx_ni used to send cloned messages to loopback device.

Signed-off-by: John Rutherford <john.rutherford@dektech.com.au>
Acked-by: Jon Maloy <jon.maloy@ericsson.com>
Acked-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 0 deletions

diff --git a/net/tipc/bearer.h b/net/tipc/bearer.h
index 7f4c569594a5..ea0f3c49cbed 100644
--- a/net/tipc/bearer.h
+++ b/net/tipc/bearer.h
@@ -232,6 +232,16 @@ void tipc_bearer_xmit(struct net *net, u32 bearer_id,
 		      struct tipc_media_addr *dst);
 void tipc_bearer_bc_xmit(struct net *net, u32 bearer_id,
 			 struct sk_buff_head *xmitq);
+void tipc_clone_to_loopback(struct net *net, struct sk_buff_head *pkts);
+int tipc_attach_loopback(struct net *net);
+void tipc_detach_loopback(struct net *net);
+
+static inline void tipc_loopback_trace(struct net *net,
+				       struct sk_buff_head *pkts)
+{
+	if (unlikely(dev_nit_active(net->loopback_dev)))
+		tipc_clone_to_loopback(net, pkts);
+}
 
 /* check if device MTU is too low for tipc headers */
 static inline bool tipc_mtu_bad(struct net_device *dev, unsigned int reserve)