From 1843b318850ac7a3990c13b1d275e0e37491301e Mon Sep 17 00:00:00 2001
From: Norman Maurer <norman_maurer@apple.com>
Date: Wed, 15 Feb 2017 19:43:52 +0100
Subject: [PATCH] Guard against having NetworkInterface.getNetworkInterfaces()
 return null

Motivation:

NetworkInterface.getNetworkInterfaces() may return null if no network interfaces are found. We should guard against it.

Modifications:

Check for null return value.

Result:

Fixes [#6384]
---
 .../src/main/java/io/netty/util/NetUtil.java  | 13 ++++++++-----
 .../netty/util/internal/MacAddressUtil.java   | 19 +++++++++++--------
 2 files changed, 19 insertions(+), 13 deletions(-)

diff --git a/common/src/main/java/io/netty/util/NetUtil.java b/common/src/main/java/io/netty/util/NetUtil.java
index 97570fa165..88d4cdd015 100644
--- a/common/src/main/java/io/netty/util/NetUtil.java
+++ b/common/src/main/java/io/netty/util/NetUtil.java
@@ -163,11 +163,14 @@ public final class NetUtil {
         // Retrieve the list of available network interfaces.
         List<NetworkInterface> ifaces = new ArrayList<NetworkInterface>();
         try {
-            for (Enumeration<NetworkInterface> i = NetworkInterface.getNetworkInterfaces(); i.hasMoreElements();) {
-                NetworkInterface iface = i.nextElement();
-                // Use the interface with proper INET addresses only.
-                if (SocketUtils.addressesFromNetworkInterface(iface).hasMoreElements()) {
-                    ifaces.add(iface);
+            Enumeration<NetworkInterface> interfaces = NetworkInterface.getNetworkInterfaces();
+            if (interfaces != null) {
+                while (interfaces.hasMoreElements()) {
+                    NetworkInterface iface = interfaces.nextElement();
+                    // Use the interface with proper INET addresses only.
+                    if (SocketUtils.addressesFromNetworkInterface(iface).hasMoreElements()) {
+                        ifaces.add(iface);
+                    }
                 }
             }
         } catch (SocketException e) {
diff --git a/common/src/main/java/io/netty/util/internal/MacAddressUtil.java b/common/src/main/java/io/netty/util/internal/MacAddressUtil.java
index 4ac088750c..ca4dc75a05 100644
--- a/common/src/main/java/io/netty/util/internal/MacAddressUtil.java
+++ b/common/src/main/java/io/netty/util/internal/MacAddressUtil.java
@@ -52,14 +52,17 @@ public final class MacAddressUtil {
         // Retrieve the list of available network interfaces.
         Map<NetworkInterface, InetAddress> ifaces = new LinkedHashMap<NetworkInterface, InetAddress>();
         try {
-            for (Enumeration<NetworkInterface> i = NetworkInterface.getNetworkInterfaces(); i.hasMoreElements();) {
-                NetworkInterface iface = i.nextElement();
-                // Use the interface with proper INET addresses only.
-                Enumeration<InetAddress> addrs = SocketUtils.addressesFromNetworkInterface(iface);
-                if (addrs.hasMoreElements()) {
-                    InetAddress a = addrs.nextElement();
-                    if (!a.isLoopbackAddress()) {
-                        ifaces.put(iface, a);
+            Enumeration<NetworkInterface> interfaces = NetworkInterface.getNetworkInterfaces();
+            if (interfaces != null) {
+                while (interfaces.hasMoreElements()) {
+                    NetworkInterface iface = interfaces.nextElement();
+                    // Use the interface with proper INET addresses only.
+                    Enumeration<InetAddress> addrs = SocketUtils.addressesFromNetworkInterface(iface);
+                    if (addrs.hasMoreElements()) {
+                        InetAddress a = addrs.nextElement();
+                        if (!a.isLoopbackAddress()) {
+                            ifaces.put(iface, a);
+                        }
                     }
                 }
             }