Add new admin panel, failover, dns fallback, providers, limiters. Update XHTTP

examples/dns_fallback/client.json

@@ -0,0 +1,62 @@
+{
+  "log": {
+    "level": "debug"
+  },
+  "dns": {
+    "servers": [
+      {
+        "type": "udp",
+        "tag": "dns-cloudflare",
+        "server": "1.2.3.4"
+      },
+      {
+        "type": "udp",
+        "tag": "dns-google",
+        "server": "1.2.3.4"
+      },
+      {
+        "type": "https",
+        "tag": "dns-quad9-doh",
+        "server": "1.1.1.1"
+      },
+      {
+        "type": "fallback",
+        "tag": "dns-fallback",
+        "servers": [
+          "dns-cloudflare",
+          "dns-google",
+          "dns-quad9-doh"
+        ],
+        // Strategies:
+        //   - "sequential" (default): query servers in order; on each error move
+        //     to the next one. Returns the first successful response, or the
+        //     last error if all servers failed.
+        //   - "parallel":             query all servers concurrently. Returns
+        //     the first successful response (cancelling the rest), or the last
+        //     error if all servers failed.
+        "strategy": "sequential"
+      }
+    ],
+    "disable_cache": true,
+    "independent_cache": true,
+    "final": "dns-fallback"
+  },
+  "inbounds": [
+    {
+      "type": "mixed",
+      "tag": "mixed-in",
+      "listen_port": 7897
+    }
+  ],
+  "outbounds": [
+    {
+      "type": "direct",
+      "tag": "direct"
+    }
+  ],
+  "route": {
+    "final": "direct",
+    "default_domain_resolver": "dns-fallback",
+    "auto_detect_interface": true
+  }
+}