fix(gateway): guard interface discovery failures

Closes #44180.
Refs #47590.
Co-authored-by: Peter Steinberger <steipete@gmail.com>

src/gateway/net.test.ts

@@ -360,6 +360,13 @@ describe("pickPrimaryLanIPv4", () => {
       vi.restoreAllMocks();
     }
   });
+
+  it("returns undefined when interface discovery throws", () => {
+    vi.spyOn(os, "networkInterfaces").mockImplementation(() => {
+      throw new Error("uv_interface_addresses failed");
+    });
+    expect(pickPrimaryLanIPv4()).toBeUndefined();
+  });
 });
 
 describe("isPrivateOrLoopbackAddress", () => {

src/gateway/net.ts

@@ -15,7 +15,12 @@ import {
  * Prefers common interface names (en0, eth0) then falls back to any external IPv4.
  */
 export function pickPrimaryLanIPv4(): string | undefined {
-  const nets = os.networkInterfaces();
+  let nets: ReturnType<typeof os.networkInterfaces>;
+  try {
+    nets = os.networkInterfaces();
+  } catch {
+    return undefined;
+  }
   const preferredNames = ["en0", "eth0"];
   for (const name of preferredNames) {
     const list = nets[name];

src/infra/infra-runtime.test.ts

@@ -240,5 +240,13 @@ describe("infra runtime", () => {
       expect(out.ipv4).toEqual(["100.123.224.76"]);
       expect(out.ipv6).toEqual(["fd7a:115c:a1e0::8801:e04c"]);
     });
+
+    it("returns empty address lists when interface discovery throws", () => {
+      vi.spyOn(os, "networkInterfaces").mockImplementation(() => {
+        throw new Error("uv_interface_addresses failed");
+      });
+
+      expect(listTailnetAddresses()).toEqual({ ipv4: [], ipv6: [] });
+    });
   });
 });

src/infra/tailnet.ts

@@ -25,7 +25,12 @@ export function listTailnetAddresses(): TailnetAddresses {
   const ipv4: string[] = [];
   const ipv6: string[] = [];
 
-  const ifaces = os.networkInterfaces();
+  let ifaces: ReturnType<typeof os.networkInterfaces>;
+  try {
+    ifaces = os.networkInterfaces();
+  } catch {
+    return { ipv4, ipv6 };
+  }
   for (const entries of Object.values(ifaces)) {
     if (!entries) {
       continue;

src/pairing/setup-code.test.ts

@@ -368,6 +368,27 @@ describe("pairing setup code", () => {
     });
   });
 
+  it("returns a bind-specific error when interface discovery throws", async () => {
+    const resolved = await resolvePairingSetupFromConfig(
+      {
+        gateway: {
+          bind: "lan",
+          auth: { mode: "token", token: "tok" },
+        },
+      },
+      {
+        networkInterfaces: () => {
+          throw new Error("uv_interface_addresses failed");
+        },
+      },
+    );
+
+    expect(resolved).toEqual({
+      ok: false,
+      error: "gateway.bind=lan set, but no private LAN IP was found.",
+    });
+  });
+
   it("prefers gateway.remote.url over tailscale when requested", async () => {
     const runCommandWithTimeout = createTailnetDnsRunner();
 

src/pairing/setup-code.ts

@@ -118,7 +118,12 @@ function pickIPv4Matching(
   networkInterfaces: () => ReturnType<typeof os.networkInterfaces>,
   matches: (address: string) => boolean,
 ): string | null {
-  const nets = networkInterfaces();
+  let nets: ReturnType<typeof os.networkInterfaces>;
+  try {
+    nets = networkInterfaces();
+  } catch {
+    return null;
+  }
   for (const entries of Object.values(nets)) {
     if (!entries) {
       continue;