From 228a01e268c478bf5bb3717aa11ad37728ac4276 Mon Sep 17 00:00:00 2001
From: Norman Maurer <norman_maurer@apple.com>
Date: Wed, 18 Aug 2021 12:11:48 +0200
Subject: [PATCH] Use StandardSocketOptions#IP_MULTICAST_IF as default source
 when joing multicast groups (#11585)

Motivation:

We should use StandardSocketOptions#IP_MULTICAST_IF as default source when joing multicast groups and only try to use the localAddress if this returns null.

Modifications:

First check if StandardSocketOptions#IP_MULTICAST_IF was set and if so use the network interface when joining mulicast groups

Result:

Fixes https://github.com/netty/netty/issues/11541
---
 .../io/netty/channel/epoll/EpollDatagramChannel.java     | 8 +++++---
 .../io/netty/channel/kqueue/KQueueDatagramChannel.java   | 9 +++++----
 .../io/netty/channel/socket/nio/NioDatagramChannel.java  | 8 +++++---
 3 files changed, 15 insertions(+), 10 deletions(-)

diff --git a/transport-native-epoll/src/main/java/io/netty/channel/epoll/EpollDatagramChannel.java b/transport-native-epoll/src/main/java/io/netty/channel/epoll/EpollDatagramChannel.java
index 87cf0e39d6..79e1fbfddc 100644
--- a/transport-native-epoll/src/main/java/io/netty/channel/epoll/EpollDatagramChannel.java
+++ b/transport-native-epoll/src/main/java/io/netty/channel/epoll/EpollDatagramChannel.java
@@ -141,9 +141,11 @@ public final class EpollDatagramChannel extends AbstractEpollChannel implements
     @Override
     public ChannelFuture joinGroup(InetAddress multicastAddress, ChannelPromise promise) {
         try {
-            return joinGroup(
-                    multicastAddress,
-                    NetworkInterface.getByInetAddress(localAddress().getAddress()), null, promise);
+            NetworkInterface iface = config().getNetworkInterface();
+            if (iface == null) {
+                iface = NetworkInterface.getByInetAddress(localAddress().getAddress());
+            }
+            return joinGroup(multicastAddress, iface, null, promise);
         } catch (IOException e) {
             promise.setFailure(e);
         }
diff --git a/transport-native-kqueue/src/main/java/io/netty/channel/kqueue/KQueueDatagramChannel.java b/transport-native-kqueue/src/main/java/io/netty/channel/kqueue/KQueueDatagramChannel.java
index 3901d051dd..af99bcc9bd 100644
--- a/transport-native-kqueue/src/main/java/io/netty/channel/kqueue/KQueueDatagramChannel.java
+++ b/transport-native-kqueue/src/main/java/io/netty/channel/kqueue/KQueueDatagramChannel.java
@@ -99,10 +99,11 @@ public final class KQueueDatagramChannel extends AbstractKQueueDatagramChannel i
     @Override
     public ChannelFuture joinGroup(InetAddress multicastAddress, ChannelPromise promise) {
         try {
-            return joinGroup(
-                    multicastAddress,
-                    NetworkInterface.getByInetAddress(localAddress().getAddress()),
-                    null, promise);
+            NetworkInterface iface = config().getNetworkInterface();
+            if (iface == null) {
+                iface = NetworkInterface.getByInetAddress(localAddress().getAddress());
+            }
+            return joinGroup(multicastAddress, iface, null, promise);
         } catch (SocketException e) {
             promise.setFailure(e);
         }
diff --git a/transport/src/main/java/io/netty/channel/socket/nio/NioDatagramChannel.java b/transport/src/main/java/io/netty/channel/socket/nio/NioDatagramChannel.java
index 701e873cd7..1cd356ed9b 100644
--- a/transport/src/main/java/io/netty/channel/socket/nio/NioDatagramChannel.java
+++ b/transport/src/main/java/io/netty/channel/socket/nio/NioDatagramChannel.java
@@ -369,10 +369,12 @@ public final class NioDatagramChannel
     @Override
     public ChannelFuture joinGroup(InetAddress multicastAddress, ChannelPromise promise) {
         try {
+            NetworkInterface iface = config.getNetworkInterface();
+            if (iface == null) {
+                iface = NetworkInterface.getByInetAddress(localAddress().getAddress());
+            }
             return joinGroup(
-                    multicastAddress,
-                    NetworkInterface.getByInetAddress(localAddress().getAddress()),
-                    null, promise);
+                    multicastAddress, iface, null, promise);
         } catch (SocketException e) {
             promise.setFailure(e);
         }