From 9fbc388f824c68df07f495f1335e282488988343 Mon Sep 17 00:00:00 2001
From: Matthias Radestock <matthias.radestock@gmail.com>
Date: Tue, 28 Nov 2017 08:21:06 +0000
Subject: [PATCH] filter internet adjacencies

Edges between the incoming and outgoing internet nodes are typically
artifacts of imperfect connection tracking, e.g. when VIPs and NAT
traversal are in use.

So lets filter them out.
---
 render/filters.go | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/render/filters.go b/render/filters.go
index 6620344c7..395a18ccf 100644
--- a/render/filters.go
+++ b/render/filters.go
@@ -144,6 +144,27 @@ func connected(nodes report.Nodes) map[string]struct{} {
 	return res
 }
 
+// filterInternetAdjacencies filters out edges between the incoming
+// and outgoing internet node. These are typically artifacts of
+// imperfect connection tracking, e.g. when VIPs and NAT traversal are
+// in use.
+func filterInternetAdjacencies(nodes report.Nodes) report.Nodes {
+	incomingInternet, ok := nodes[IncomingInternetID]
+	if !ok {
+		return nodes
+	}
+	newAdjacency := report.MakeIDList()
+	for _, dstID := range incomingInternet.Adjacency {
+		if dstID != OutgoingInternetID {
+			newAdjacency = newAdjacency.Add(dstID)
+		}
+	}
+	incomingInternet.Adjacency = newAdjacency
+	output := nodes.Copy()
+	output[IncomingInternetID] = incomingInternet
+	return output
+}
+
 // ColorConnected colors nodes with the IsConnectedMark key if they
 // have edges to or from them.  Edges to/from yourself are not counted
 // here (see #656).
@@ -166,13 +187,14 @@ type filterUnconnected struct {
 
 // Transform implements Transformer
 func (f filterUnconnected) Transform(input Nodes) Nodes {
-	connected := connected(input.Nodes)
+	output := filterInternetAdjacencies(input.Nodes)
+	connected := connected(output)
 	return FilterFunc(func(node report.Node) bool {
 		if _, ok := connected[node.ID]; ok || (f.onlyPseudo && !IsPseudoTopology(node)) {
 			return true
 		}
 		return false
-	}).Transform(input)
+	}).Transform(Nodes{Nodes: output, Filtered: input.Filtered})
 }
 
 // FilterUnconnected is a transformer that filters unconnected nodes