1 files changed, 27 insertions, 0 deletions
diff --git a/src/Agent.Windows/Network/NetworkAllowanceSnapshot.cs b/src/Agent.Windows/Network/NetworkAllowanceSnapshot.cs
new file mode 100644
index 0000000..5feb457
--- /dev/null
+++ b/src/Agent.Windows/Network/NetworkAllowanceSnapshot.cs
@@ -0,0 +1,27 @@
+using System.Net;
+
+namespace Agent.Windows.Network;
+
+public sealed record NetworkEndpoint(IPAddress Address, ushort Port);
+
+public static class NetworkAllowanceSnapshot
+{
+    public static async Task<IReadOnlyList<NetworkEndpoint>> ResolveAsync(IEnumerable<(string Host, IReadOnlyList<int> Ports)> allowances,
+        CancellationToken cancellationToken)
+    {
+        var endpoints = new HashSet<NetworkEndpoint>();
+        foreach ((string host, IReadOnlyList<int> ports) in allowances)
+        {
+            IPAddress[] addresses = await Dns.GetHostAddressesAsync(host, cancellationToken).ConfigureAwait(false);
+            foreach (int port in ports)
+            {
+                if (port is < 1 or > 65535) throw new ArgumentOutOfRangeException(nameof(allowances), $"Invalid network port {port}.");
+                foreach (IPAddress address in addresses.Where(static item => item.AddressFamily is
+                    System.Net.Sockets.AddressFamily.InterNetwork or System.Net.Sockets.AddressFamily.InterNetworkV6))
+                    endpoints.Add(new(address, (ushort)port));
+            }
+        }
+        return endpoints.OrderBy(static item => item.Address.ToString(), StringComparer.Ordinal)
+            .ThenBy(static item => item.Port).ToArray();
+    }
+}