From 072efe0625dcf33a57fef4233d589fec96cfa944 Mon Sep 17 00:00:00 2001
From: Kenneth Skovhede <kenneth@hexad.dk>
Date: Fri, 25 Oct 2024 11:17:30 +0200
Subject: [PATCH] Implemented explict support for IPv6 listener in the
 webserver. Using any/all/* will now listen on both IPv4 and IPv6 if
 available. To force IPv4-any, use `0.0.0.0` and similar `[::]` for IPv6. The
 loopback value listens on IPv4 and the new ipv6loopback value selects IPv6
 loopback. It is not possible to get both loopback values at the same time.

---
 Duplicati/Library/RestAPI/Strings.cs          |  2 +-
 Duplicati/Server/WebServerLoader.cs           |  2 ++
 Duplicati/WebserverCore/DuplicatiWebserver.cs | 20 +++++++++++++++----
 3 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/Duplicati/Library/RestAPI/Strings.cs b/Duplicati/Library/RestAPI/Strings.cs
index 8115953df..0210afdf0 100644
--- a/Duplicati/Library/RestAPI/Strings.cs
+++ b/Duplicati/Library/RestAPI/Strings.cs
@@ -32,7 +32,7 @@ Error message: {0}", error); }
                 public static string WebserverPortDescription { get { return LC.L(@"The port the webserver listens on. Multiple values may be supplied with a comma in between."); } }
                 public static string WebserverCertificateFileDescription { get { return LC.L(@"The certificate and key file in PKCS #12 format the webserver use for SSL. Only RSA/DSA keys are supported."); } }
                 public static string WebserverCertificatePasswordDescription { get { return LC.L(@"The password for decryption of certificate PKCS #12 file."); } }
-                public static string WebserverInterfaceDescription { get { return LC.L(@"The interface the webserver listens on. The special values ""*"" and ""any"" means any interface. The special value ""loopback"" means the loopback adapter."); } }
+                public static string WebserverInterfaceDescription { get { return LC.L(@"The interface the webserver listens on. The special values ""*"" and ""any"" means any interface. The special value ""loopback"" means the loopback adapter and ""ipv6loopback"" means IPv6 loopback."); } }
                 public static string WebserverPasswordDescription { get { return LC.L(@"The password required to access the webserver. This option is saved so you do not need to set it on each run. Setting an empty value disables the password."); } }
                 public static string WebserverAllowedhostnamesDescription { get { return LC.L(@"The hostnames that are accepted, separated with semicolons. If any of the hostnames are ""*"", all hostnames are allowed and the hostname checking is disabled."); } }
                 public static string PingpongkeepaliveLong { get { return LC.L(@"When running as a server, the service daemon must verify that the process is responding. If this option is enabled, the server reads stdin and writes a reply to each line read."); } }
diff --git a/Duplicati/Server/WebServerLoader.cs b/Duplicati/Server/WebServerLoader.cs
index 43724d688..6be89523d 100644
--- a/Duplicati/Server/WebServerLoader.cs
+++ b/Duplicati/Server/WebServerLoader.cs
@@ -173,6 +173,8 @@ public static class WebServerLoader
         interfacestring = interfacestring.Trim();
         if (new[] { "*", "all", "any" }.Any(x => x.Equals(interfacestring, StringComparison.OrdinalIgnoreCase)))
             listenInterface = System.Net.IPAddress.Any;
+        else if (interfacestring == "ipv6loopback")
+            listenInterface = System.Net.IPAddress.IPv6Loopback;
         else if (interfacestring != "loopback")
             listenInterface = System.Net.IPAddress.Parse(interfacestring);
 
diff --git a/Duplicati/WebserverCore/DuplicatiWebserver.cs b/Duplicati/WebserverCore/DuplicatiWebserver.cs
index e48706ffe..c66b6aa3a 100644
--- a/Duplicati/WebserverCore/DuplicatiWebserver.cs
+++ b/Duplicati/WebserverCore/DuplicatiWebserver.cs
@@ -98,11 +98,23 @@ public partial class DuplicatiWebserver
 
         builder.WebHost.ConfigureKestrel(options =>
         {
-            options.Listen(settings.Interface, settings.Port, listenOptions =>
+            // Handle IPv6 addresses
+            if (settings.Interface == System.Net.IPAddress.Any)
             {
-                if (settings.Certificate != null)
-                    listenOptions.UseHttps(settings.Certificate);
-            });
+                options.ListenAnyIP(settings.Port, listenOptions =>
+                {
+                    if (settings.Certificate != null)
+                        listenOptions.UseHttps(settings.Certificate);
+                });
+            }
+            else
+            {
+                options.Listen(settings.Interface, settings.Port, listenOptions =>
+                {
+                    if (settings.Certificate != null)
+                        listenOptions.UseHttps(settings.Certificate);
+                });
+            }
         });
 
         builder.Services.Configure<JsonOptions>(opt =>