feat: detect an agent's public IPv4 and IPv6 addresses automatically, manual values still win [CI]

backend/shared/MoShiro.Protocol/PublicAddress.cs

@@ -0,0 +1,46 @@
+using System.Net;
+using System.Net.Sockets;
+
+namespace MoShiro.Protocol;
+
+/// <summary>哪些地址算「公网上能拨进来的地址」：Agent 上报本机地址和面板自动识别共用同一套判断。</summary>
+public static class PublicAddress
+{
+    public static bool IsPublicIpv4(IPAddress address)
+    {
+        if (address.AddressFamily != AddressFamily.InterNetwork)
+        {
+            return false;
+        }
+
+        byte[] b = address.GetAddressBytes();
+        return !(b[0] is 0 or 10 or 127 or >= 224
+            || (b[0] == 100 && b[1] is >= 64 and <= 127)
+            || (b[0] == 169 && b[1] == 254)
+            || (b[0] == 172 && b[1] is >= 16 and <= 31)
+            || (b[0] == 192 && b[1] == 168)
+            || (b[0] == 192 && b[1] == 0 && b[2] is 0 or 2)
+            || (b[0] == 198 && b[1] is 18 or 19)
+            || (b[0] == 198 && b[1] == 51 && b[2] == 100)
+            || (b[0] == 203 && b[1] == 0 && b[2] == 113));
+    }
+
+    public static bool IsGlobalIpv6(IPAddress address)
+    {
+        if (address.AddressFamily != AddressFamily.InterNetworkV6 || address.IsIPv4MappedToIPv6)
+        {
+            return false;
+        }
+
+        byte[] b = address.GetAddressBytes();
+        if ((b[0] & 0xE0) != 0x20)
+        {
+            return false;
+        }
+
+        // 2001:db8::/32 文档、2002::/16 6to4、2001::/32 Teredo
+        return !((b[0] == 0x20 && b[1] == 0x01 && b[2] == 0x0d && b[3] == 0xb8)
+            || (b[0] == 0x20 && b[1] == 0x02)
+            || (b[0] == 0x20 && b[1] == 0x01 && b[2] == 0 && b[3] == 0));
+    }
+}