feat: hostname dual support

Author: abishekve

ThingConnect.Pulse.Server/Services/Monitoring/DiscoveryService.cs

@@ -174,62 +174,37 @@ public enum IPv6Format
         Full
     }
 
-    private IEnumerable<string> ExpandIPv6Host(string host, IPv6Format format = IPv6Format.Compressed)
-    {
-        string hostPart = host;
-        string? zoneIndex = null;
-
-        if (host.Contains('%'))
-        {
-            var split = host.Split('%');
-            hostPart = split[0];
-            zoneIndex = split[1];
-        }
-
-        if (!IPAddress.TryParse(hostPart, out var ip)) yield break;
-        if (ip.AddressFamily != AddressFamily.InterNetworkV6) yield break;
-
-        string compressed = ip.ToString();
-
-        // Full form (always 8 groups of 4 hex digits)
-        string full = string.Join(":", Enumerable.Range(0, 8)
-            .Select(i => ((ushort)((ip.GetAddressBytes()[i * 2] << 8) |
-                                    ip.GetAddressBytes()[i * 2 + 1])).ToString("x4")));
-
-        string ApplyZone(string addr) => zoneIndex != null ? $"{addr}%{zoneIndex}" : addr;
-
-        if (format == IPv6Format.Compressed)
-        {
-            yield return ApplyZone(compressed);
-        }
-        else if (format == IPv6Format.Full)
-        {
-            yield return ApplyZone(full);
-        }
-    }
-
    public async Task<IEnumerable<string>> ResolveHostnameAsync(string hostname, CancellationToken cancellationToken = default)
     {
+        var ipv4Addresses = new List<string>();
+        var ipv6Addresses = new List<string>();
+
         try
         {
             IPAddress[] addresses = await Dns.GetHostAddressesAsync(hostname);
-            return addresses
-                .Where(addr => addr.AddressFamily == AddressFamily.InterNetwork || addr.AddressFamily == AddressFamily.InterNetworkV6)
-                .Select(addr =>
-                {
-                    // Include zone index for IPv6 link-local
-                    if (addr.AddressFamily == AddressFamily.InterNetworkV6 && addr.IsIPv6LinkLocal && addr.ScopeId != 0)
-                        return addr + "%" + addr.ScopeId;
 
-                    return addr.ToString();
-                })
-                .ToList();
+            foreach (var addr in addresses)
+            {
+                if (addr.AddressFamily == AddressFamily.InterNetwork) // IPv4
+                {
+                    ipv4Addresses.Add(addr.ToString());
+                }
+                else if (addr.AddressFamily == AddressFamily.InterNetworkV6) // IPv6
+                {
+                    string address = addr.IsIPv6LinkLocal && addr.ScopeId != 0
+                        ? addr + "%" + addr.ScopeId
+                        : addr.ToString();
+                    ipv6Addresses.Add(address);
+                }
+            }
         }
         catch (Exception ex)
         {
             _logger.LogWarning(ex, "Failed to resolve hostname: {Hostname}", hostname);
-            return Enumerable.Empty<string>();
         }
+
+        // Always return both IPv4 and IPv6 if available
+        return ipv6Addresses.Concat(ipv4Addresses);
     }
 
     public async Task<IEnumerable<Data.Endpoint>> ExpandTargetsAsync(IEnumerable<dynamic> configTargets,
@@ -257,6 +232,40 @@ public async Task<IEnumerable<string>> ResolveHostnameAsync(string hostname, Can
         return endpoints;
     }
 
+    private IEnumerable<string> ExpandIPv6Host(string host, IPv6Format format = IPv6Format.Compressed)
+    {
+        string hostPart = host;
+        string? zoneIndex = null;
+
+        if (host.Contains('%'))
+        {
+            var split = host.Split('%');
+            hostPart = split[0];
+            zoneIndex = split[1];
+        }
+
+        if (!IPAddress.TryParse(hostPart, out var ip)) yield break;
+        if (ip.AddressFamily != AddressFamily.InterNetworkV6) yield break;
+
+        string compressed = ip.ToString();
+
+        // Full form (always 8 groups of 4 hex digits)
+        string full = string.Join(":", Enumerable.Range(0, 8)
+            .Select(i => ((ushort)((ip.GetAddressBytes()[i * 2] << 8) |
+                                    ip.GetAddressBytes()[i * 2 + 1])).ToString("x4")));
+
+        string ApplyZone(string addr) => zoneIndex != null ? $"{addr}%{zoneIndex}" : addr;
+
+        if (format == IPv6Format.Compressed)
+        {
+            yield return ApplyZone(compressed);
+        }
+        else if (format == IPv6Format.Full)
+        {
+            yield return ApplyZone(full);
+        }
+    }
+
     private async Task<IEnumerable<Data.Endpoint>> ExpandSingleTargetAsync(dynamic target,
         CancellationToken cancellationToken)
     {
@@ -270,25 +279,28 @@ public async Task<IEnumerable<string>> ResolveHostnameAsync(string hostname, Can
 
             if (IPAddress.TryParse(host, out var ip))
             {
-                // Expand IPv6 host into compressed and full forms
                 if (ip.AddressFamily == AddressFamily.InterNetworkV6)
+                {
                     hosts.AddRange(ExpandIPv6Host(host));
+                }
                 else
+                {
                     hosts.Add(host); // IPv4
+                }
             }
             else
             {
                 // Hostname
                 IEnumerable<string> resolvedHosts = await ResolveHostnameAsync(host, cancellationToken);
-                hosts.AddRange(resolvedHosts.SelectMany(resolvedHost =>
+                hosts.AddRange(resolvedHosts.Select(resolvedHost =>
                 {
                     if (IPAddress.TryParse(resolvedHost, out var resolvedIp) &&
                         resolvedIp.AddressFamily == AddressFamily.InterNetworkV6)
                     {
-                        return ExpandIPv6Host(resolvedHost);
+                        return ExpandIPv6Host(resolvedHost, IPv6Format.Compressed);
                     }
                     return new[] { resolvedHost };
-                }));
+                }).SelectMany(x => x));
             }
         }
         else if (target.cidr != null)