fix(sync): support custom koreader sync server hosted in LAN, closes #1800 (#1830)

apps/readest-app/src/utils/network.ts

@@ -0,0 +1,55 @@
+export const isLanAddress = (url: string) => {
+  try {
+    const urlObj = new URL(url);
+    const hostname = urlObj.hostname;
+
+    if (hostname === 'localhost' || hostname === '127.0.0.1') {
+      return true;
+    }
+
+    // Check for IPv4 private ranges
+    const ipv4Regex = /^(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})$/;
+    const match = hostname.match(ipv4Regex);
+
+    if (match) {
+      const [, a, b, c, d] = match.map(Number);
+      if (a === undefined || b === undefined || c === undefined || d === undefined) {
+        return false;
+      }
+
+      // Validate IP format
+      if (a > 255 || b > 255 || c > 255 || d > 255) {
+        return false;
+      }
+
+      // Check private IP ranges:
+      // 10.0.0.0/8 (10.0.0.0 to 10.255.255.255)
+      if (a === 10) return true;
+
+      // 172.16.0.0/12 (172.16.0.0 to 172.31.255.255)
+      if (a === 172 && b >= 16 && b <= 31) return true;
+
+      // 192.168.0.0/16 (192.168.0.0 to 192.168.255.255)
+      if (a === 192 && b === 168) return true;
+
+      // 169.254.0.0/16 (link-local addresses)
+      if (a === 169 && b === 254) return true;
+    }
+
+    // Check for IPv6 private addresses (simplified check)
+    if (hostname.includes(':')) {
+      if (
+        hostname.startsWith('::1') ||
+        hostname.startsWith('fe80:') ||
+        hostname.startsWith('fc00:') ||
+        hostname.startsWith('fd00:')
+      ) {
+        return true;
+      }
+    }
+
+    return false;
+  } catch {
+    return false;
+  }
+};