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, 64 insertions, 0 deletions

diff --git a/net/tipc/bearer.c b/net/tipc/bearer.c
index a809c0ec8d15..0214aa1c4427 100644
--- a/net/tipc/bearer.c
+++ b/net/tipc/bearer.c
@@ -389,6 +389,11 @@ int tipc_enable_l2_media(struct net *net, struct tipc_bearer *b,
 		dev_put(dev);
 		return -EINVAL;
 	}
+	if (dev == net->loopback_dev) {
+		dev_put(dev);
+		pr_info("Enabling <%s> not permitted\n", b->name);
+		return -EINVAL;
+	}
 
 	/* Autoconfigure own node identity if needed */
 	if (!tipc_own_id(net) && hwaddr_len <= NODE_ID_LEN) {
@@ -674,6 +679,65 @@ void tipc_bearer_stop(struct net *net)
 	}
 }
 
+void tipc_clone_to_loopback(struct net *net, struct sk_buff_head *pkts)
+{
+	struct net_device *dev = net->loopback_dev;
+	struct sk_buff *skb, *_skb;
+	int exp;
+
+	skb_queue_walk(pkts, _skb) {
+		skb = pskb_copy(_skb, GFP_ATOMIC);
+		if (!skb)
+			continue;
+
+		exp = SKB_DATA_ALIGN(dev->hard_header_len - skb_headroom(skb));
+		if (exp > 0 && pskb_expand_head(skb, exp, 0, GFP_ATOMIC)) {
+			kfree_skb(skb);
+			continue;
+		}
+
+		skb_reset_network_header(skb);
+		dev_hard_header(skb, dev, ETH_P_TIPC, dev->dev_addr,
+				dev->dev_addr, skb->len);
+		skb->dev = dev;
+		skb->pkt_type = PACKET_HOST;
+		skb->ip_summed = CHECKSUM_UNNECESSARY;
+		skb->protocol = eth_type_trans(skb, dev);
+		netif_rx_ni(skb);
+	}
+}
+
+static int tipc_loopback_rcv_pkt(struct sk_buff *skb, struct net_device *dev,
+				 struct packet_type *pt, struct net_device *od)
+{
+	consume_skb(skb);
+	return NET_RX_SUCCESS;
+}
+
+int tipc_attach_loopback(struct net *net)
+{
+	struct net_device *dev = net->loopback_dev;
+	struct tipc_net *tn = tipc_net(net);
+
+	if (!dev)
+		return -ENODEV;
+
+	dev_hold(dev);
+	tn->loopback_pt.dev = dev;
+	tn->loopback_pt.type = htons(ETH_P_TIPC);
+	tn->loopback_pt.func = tipc_loopback_rcv_pkt;
+	dev_add_pack(&tn->loopback_pt);
+	return 0;
+}
+
+void tipc_detach_loopback(struct net *net)
+{
+	struct tipc_net *tn = tipc_net(net);
+
+	dev_remove_pack(&tn->loopback_pt);
+	dev_put(net->loopback_dev);
+}
+
 /* Caller should hold rtnl_lock to protect the bearer */
 static int __tipc_nl_add_bearer(struct tipc_nl_msg *msg,
 				struct tipc_bearer *bearer, int nlflags)