From 146681f0ba927b6c2d1e392a2b157a28c36e1a6b Mon Sep 17 00:00:00 2001
From: john janzen <git@johnjanzen.me>
Date: Sun, 21 Dec 2025 15:37:22 +0100
Subject: [PATCH] Warn server administrator when IPv6 is enabled but
 unsupported by OS

---
 Jellyfin.Server/ServerSetupApp/SetupServer.cs     |  2 +-
 src/Jellyfin.Networking/Manager/NetworkManager.cs | 10 ++++++++--
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/Jellyfin.Server/ServerSetupApp/SetupServer.cs b/Jellyfin.Server/ServerSetupApp/SetupServer.cs
index 4340969a30..1aa39f97b6 100644
--- a/Jellyfin.Server/ServerSetupApp/SetupServer.cs
+++ b/Jellyfin.Server/ServerSetupApp/SetupServer.cs
@@ -162,7 +162,7 @@ public sealed class SetupServer : IDisposable
                                 {
                                     var knownBindInterfaces = NetworkManager.GetInterfacesCore(_loggerFactory.CreateLogger<SetupServer>(), config.EnableIPv4, config.EnableIPv6);
                                     knownBindInterfaces = NetworkManager.FilterBindSettings(config, knownBindInterfaces.ToList(), config.EnableIPv4, config.EnableIPv6);
-                                    var bindInterfaces = NetworkManager.GetAllBindInterfaces(false, _configurationManager, knownBindInterfaces, config.EnableIPv4, config.EnableIPv6);
+                                    var bindInterfaces = NetworkManager.GetAllBindInterfaces(_loggerFactory.CreateLogger<NetworkManager>(), false, _configurationManager, knownBindInterfaces, config.EnableIPv4, config.EnableIPv6);
                                     Extensions.WebHostBuilderExtensions.SetupJellyfinWebServer(
                                         bindInterfaces,
                                         config.InternalHttpPort,
diff --git a/src/Jellyfin.Networking/Manager/NetworkManager.cs b/src/Jellyfin.Networking/Manager/NetworkManager.cs
index e82e854417..88f16d8c50 100644
--- a/src/Jellyfin.Networking/Manager/NetworkManager.cs
+++ b/src/Jellyfin.Networking/Manager/NetworkManager.cs
@@ -753,12 +753,13 @@ public class NetworkManager : INetworkManager, IDisposable
     /// <inheritdoc/>
     public IReadOnlyList<IPData> GetAllBindInterfaces(bool individualInterfaces = false)
     {
-        return NetworkManager.GetAllBindInterfaces(individualInterfaces, _configurationManager, _interfaces, IsIPv4Enabled, IsIPv6Enabled);
+        return NetworkManager.GetAllBindInterfaces(_logger, individualInterfaces, _configurationManager, _interfaces, IsIPv4Enabled, IsIPv6Enabled);
     }
 
     /// <summary>
     /// Reads the jellyfin configuration of the configuration manager and produces a list of interfaces that should be bound.
     /// </summary>
+    /// <param name="logger">Logger to use for messages.</param>
     /// <param name="individualInterfaces">Defines that only known interfaces should be used.</param>
     /// <param name="configurationManager">The ConfigurationManager.</param>
     /// <param name="knownInterfaces">The known interfaces that gets returned if possible or instructed.</param>
@@ -766,6 +767,7 @@ public class NetworkManager : INetworkManager, IDisposable
     /// <param name="readIpv6">Include IPV6 type interfaces.</param>
     /// <returns>A list of ip address of which jellyfin should bind to.</returns>
     public static IReadOnlyList<IPData> GetAllBindInterfaces(
+        ILogger<NetworkManager> logger,
         bool individualInterfaces,
         IConfigurationManager configurationManager,
         IReadOnlyList<IPData> knownInterfaces,
@@ -780,7 +782,11 @@ public class NetworkManager : INetworkManager, IDisposable
         }
 
         // TODO: remove when upgrade to dotnet 11 is done
-        readIpv6 &= Socket.OSSupportsIPv6;
+        if (readIpv6 && !Socket.OSSupportsIPv6)
+        {
+            logger.LogWarning("IPv6 Unsupported by OS, not listening on IPv6");
+            readIpv6 = false;
+        }
 
         // No bind address and no exclusions, so listen on all interfaces.
         var result = new List<IPData>();