From 32a57e63dbf7385d4da1ada31bb9a205919d8e7d Mon Sep 17 00:00:00 2001
From: Peter Bourgon <peter@bourgon.org>
Date: Tue, 29 Sep 2015 15:11:02 +0200
Subject: [PATCH] probe/endpoint: NATMapper missed an edge case

NATMapper can be created with a nil Conntracker if
ConntrackerModulePresent is false, e.g. on Darwin.
Check for that in ApplyNAT.
---
 probe/endpoint/nat.go      | 9 ++++++---
 probe/endpoint/nat_test.go | 4 ++--
 probe/endpoint/reporter.go | 2 +-
 3 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/probe/endpoint/nat.go b/probe/endpoint/nat.go
index fe9927155..18ae534d1 100644
--- a/probe/endpoint/nat.go
+++ b/probe/endpoint/nat.go
@@ -21,8 +21,8 @@ type NATMapper struct {
 	Conntracker
 }
 
-// NewNATMapper is exposed for testing
-func NewNATMapper(ct Conntracker) NATMapper {
+// MakeNATMapper is exposed for testing
+func MakeNATMapper(ct Conntracker) NATMapper {
 	return NATMapper{ct}
 }
 
@@ -50,7 +50,10 @@ func toMapping(f Flow) *endpointMapping {
 // ApplyNAT duplicates Nodes in the endpoint topology of a
 // report, based on the NAT table as returns by natTable.
 func (n NATMapper) ApplyNAT(rpt report.Report, scope string) {
-	n.WalkFlows(func(f Flow) {
+	if n.Conntracker == nil {
+		return
+	}
+	n.Conntracker.WalkFlows(func(f Flow) {
 		var (
 			mapping          = toMapping(f)
 			realEndpointID   = report.MakeEndpointNodeID(scope, mapping.originalIP, strconv.Itoa(mapping.originalPort))
diff --git a/probe/endpoint/nat_test.go b/probe/endpoint/nat_test.go
index 65b2c16ea..49580d512 100644
--- a/probe/endpoint/nat_test.go
+++ b/probe/endpoint/nat_test.go
@@ -55,7 +55,7 @@ func TestNat(t *testing.T) {
 			"foo":         "bar",
 		}))
 
-		natmapper := endpoint.NewNATMapper(ct)
+		natmapper := endpoint.MakeNATMapper(ct)
 		natmapper.ApplyNAT(have, "host1")
 		if !reflect.DeepEqual(want, have) {
 			t.Fatal(test.Diff(want, have))
@@ -88,7 +88,7 @@ func TestNat(t *testing.T) {
 			"foo":         "baz",
 		}))
 
-		natmapper := endpoint.NewNATMapper(ct)
+		natmapper := endpoint.MakeNATMapper(ct)
 		natmapper.ApplyNAT(have, "host1")
 		if !reflect.DeepEqual(want, have) {
 			t.Fatal(test.Diff(want, have))
diff --git a/probe/endpoint/reporter.go b/probe/endpoint/reporter.go
index b5b67d7fb..ec239cc3e 100644
--- a/probe/endpoint/reporter.go
+++ b/probe/endpoint/reporter.go
@@ -66,7 +66,7 @@ func NewReporter(hostID, hostName string, includeProcesses bool, useConntrack bo
 		if err != nil {
 			log.Printf("Failed to start conntracker for natmapper: %v", err)
 		}
-		natmapper = NewNATMapper(ct)
+		natmapper = MakeNATMapper(ct)
 	}
 	return &Reporter{
 		hostID:           hostID,