feat(routes): parse device routes from ip route output

src/server/utils/routes.ts

@@ -99,8 +99,40 @@ function collectDesiredRoutes(
   return desired;
 }
 
+/**
+ * Parse `ip route show dev <inf>` output into routes tagged with whether wg-easy
+ * manages them. Kernel-installed routes (the connected subnet, link-local,
+ * multicast) are present but flagged unmanaged, so they are never removed and
+ * never re-added.
+ */
+function parseDeviceRoutes(output: string): DeviceRoute[] {
+  const result: DeviceRoute[] = [];
+
+  for (const line of output.trim().split('\n')) {
+    const trimmed = line.trim();
+    if (!trimmed) {
+      continue;
+    }
+    const dest = trimmed.split(/\s+/)[0];
+    if (!dest || dest === 'default') {
+      continue;
+    }
+    const normalized = normalizeRoute(dest);
+    if (!normalized) {
+      continue;
+    }
+    const managed =
+      !trimmed.includes('proto kernel') &&
+      isManageable(normalized.cidr, normalized.version);
+    result.push({ cidr: normalized.cidr, managed });
+  }
+
+  return result;
+}
+
 export const routesTestExports = {
   normalizeRoute,
   isManageable,
   collectDesiredRoutes,
+  parseDeviceRoutes,
 };

src/test/unit/routes.spec.ts

@@ -2,8 +2,12 @@ import { describe, expect, test } from 'vitest';
 
 import { routesTestExports } from '#server/utils/routes';
 
-const { normalizeRoute, isManageable, collectDesiredRoutes } =
-  routesTestExports;
+const {
+  normalizeRoute,
+  isManageable,
+  collectDesiredRoutes,
+  parseDeviceRoutes,
+} = routesTestExports;
 
 describe('routes', () => {
   describe('normalizeRoute', () => {
@@ -110,4 +114,34 @@ describe('routes', () => {
       expect([...result[4]]).toEqual(['10.0.0.0/24']);
     });
   });
+
+  describe('parseDeviceRoutes', () => {
+    test('flags the kernel connected route as unmanaged', () => {
+      const output = [
+        '100.255.1.0/24 proto kernel scope link src 100.255.1.1',
+        '192.168.120.0/22 scope link',
+      ].join('\n');
+      expect(parseDeviceRoutes(output)).toEqual([
+        { cidr: '100.255.1.0/24', managed: false },
+        { cidr: '192.168.120.0/22', managed: true },
+      ]);
+    });
+    test('skips default routes', () => {
+      expect(parseDeviceRoutes('default via 10.0.0.1')).toEqual([]);
+    });
+    test('handles empty output', () => {
+      expect(parseDeviceRoutes('')).toEqual([]);
+      expect(parseDeviceRoutes('\n  \n')).toEqual([]);
+    });
+    test('flags IPv6 link-local kernel route as unmanaged', () => {
+      const output = [
+        'fe80::/64 proto kernel metric 256 pref medium',
+        '2001:db8::/64 metric 1024 pref medium',
+      ].join('\n');
+      expect(parseDeviceRoutes(output)).toEqual([
+        { cidr: 'fe80::/64', managed: false },
+        { cidr: '2001:db8::/64', managed: true },
+      ]);
+    });
+  });
 });