don't exclude NATed connections in mapping to processes

We used to ignore source endpoints that are associated with multiple
destination endpoints, which is a partial workaround for our inability
to correctly represent two connections from the same source ip/port
but different processes, or the same destination ip/port but different
processes. See #2665.

However, that condition is too coarse. In particular, we end up
ignoring endpoints that are connected to NATed destinations, since the
latter are represented by two (or more) endpoints.

The change here corrects that.

render/process.go

@@ -2,6 +2,7 @@ package render
 
 import (
 	"github.com/weaveworks/scope/probe/docker"
+	"github.com/weaveworks/scope/probe/endpoint"
 	"github.com/weaveworks/scope/probe/process"
 	"github.com/weaveworks/scope/report"
 )
@@ -98,11 +99,7 @@ func (e endpoints2Processes) Render(rpt report.Report) Nodes {
 			if !ok {
 				continue
 			}
-
-			if len(n.Adjacency) > 1 {
-				// We cannot be sure that the pid is associated with all the
-				// connections. It is better to drop such an endpoint than
-				// risk rendering bogus connections.
+			if hasMoreThanOneConnection(n, endpoints.Nodes) {
 				continue
 			}
 
@@ -124,6 +121,33 @@ func (e endpoints2Processes) Render(rpt report.Report) Nodes {
 	return ret.result()
 }
 
+// When there is more than one connection originating from a source
+// endpoint, we cannot be sure that its pid is associated with all of
+// them, since the source endpoint may have been re-used by a
+// different process. See #2665. It is better to drop such an endpoint
+// than risk rendering bogus connections.  Aliased connections - when
+// all the remote endpoints represent the same logical endpoint, due
+// to NATing - are fine though.
+func hasMoreThanOneConnection(n report.Node, endpoints report.Nodes) bool {
+	if len(n.Adjacency) < 2 {
+		return false
+	}
+	firstRealEndpointID := ""
+	for _, endpointID := range n.Adjacency {
+		if ep, ok := endpoints[endpointID]; ok {
+			if copyID, _, ok := ep.Latest.LookupEntry(endpoint.CopyOf); ok {
+				endpointID = copyID
+			}
+		}
+		if firstRealEndpointID == "" {
+			firstRealEndpointID = endpointID
+		} else if firstRealEndpointID != endpointID {
+			return true
+		}
+	}
+	return false
+}
+
 // processes2Names maps process Nodes to Nodes for each process name.
 func processes2Names(processes Nodes) Nodes {
 	ret := newJoinResults()