fix(gateway): harden tailscale cleanup recovery

src/gateway/server-tailscale.test.ts

@@ -0,0 +1,359 @@
+import { beforeEach, describe, expect, it, vi } from "vitest";
+
+const tailscaleState = vi.hoisted(() => ({
+  enableServe: vi.fn(async (_port: number) => {}),
+  disableServe: vi.fn(async () => {}),
+  enableFunnel: vi.fn(async (_port: number) => {}),
+  disableFunnel: vi.fn(async () => {}),
+  getHost: vi.fn(async () => "gateway.tailnet.ts.net"),
+}));
+
+vi.mock("../infra/tailscale.js", () => ({
+  enableTailscaleServe: (port: number) => tailscaleState.enableServe(port),
+  disableTailscaleServe: () => tailscaleState.disableServe(),
+  enableTailscaleFunnel: (port: number) => tailscaleState.enableFunnel(port),
+  disableTailscaleFunnel: () => tailscaleState.disableFunnel(),
+  getTailnetHostname: () => tailscaleState.getHost(),
+}));
+
+import { startGatewayTailscaleExposure } from "./server-tailscale.js";
+
+function createOwnerStore() {
+  let currentOwner: null | {
+    token: string;
+    mode: "serve" | "funnel";
+    port: number;
+    pid: number;
+    claimedAt: string;
+    phase: "active" | "cleaning";
+    cleanupStartedAt?: string;
+    alive: boolean;
+  } = null;
+  let nextPid = process.pid - 1;
+
+  return {
+    async claim(mode: "serve" | "funnel", port: number) {
+      const previousOwner = currentOwner;
+      const owner = {
+        token: `owner-${++nextPid}`,
+        mode,
+        port,
+        pid: nextPid,
+        claimedAt: new Date(0).toISOString(),
+        phase: "active" as const,
+        alive: true,
+      };
+      currentOwner = owner;
+      return { owner, previousOwner };
+    },
+    async replaceIfCurrent(token: string, nextOwner: typeof currentOwner | null) {
+      if (currentOwner?.token !== token) {
+        return false;
+      }
+      currentOwner = nextOwner;
+      return true;
+    },
+    async runCleanupIfCurrentOwner(token: string, cleanup: () => Promise<void>) {
+      if (!currentOwner) {
+        return false;
+      }
+      if (currentOwner.token !== token && currentOwner.alive) {
+        return false;
+      }
+      currentOwner = {
+        ...currentOwner,
+        phase: "cleaning",
+        cleanupStartedAt: new Date(0).toISOString(),
+      };
+      await cleanup();
+      currentOwner = null;
+      return true;
+    },
+    markCurrentOwnerDead() {
+      if (currentOwner) {
+        currentOwner = { ...currentOwner, alive: false };
+      }
+    },
+  };
+}
+
+const modeCases = [
+  {
+    mode: "serve" as const,
+    enableMock: tailscaleState.enableServe,
+    disableMock: tailscaleState.disableServe,
+  },
+  {
+    mode: "funnel" as const,
+    enableMock: tailscaleState.enableFunnel,
+    disableMock: tailscaleState.disableFunnel,
+  },
+];
+
+describe.each(modeCases)(
+  "startGatewayTailscaleExposure ($mode)",
+  ({ mode, enableMock, disableMock }) => {
+    beforeEach(() => {
+      vi.restoreAllMocks();
+      vi.clearAllMocks();
+    });
+
+    it("skips stale cleanup after a newer gateway takes ownership", async () => {
+      const ownerStore = createOwnerStore();
+      const logTailscale = {
+        info: vi.fn(),
+        warn: vi.fn(),
+      };
+
+      const cleanupA = await startGatewayTailscaleExposure({
+        tailscaleMode: mode,
+        resetOnExit: true,
+        port: 18789,
+        logTailscale,
+        ownerStore,
+      });
+      const cleanupB = await startGatewayTailscaleExposure({
+        tailscaleMode: mode,
+        resetOnExit: true,
+        port: 18789,
+        logTailscale,
+        ownerStore,
+      });
+
+      await cleanupA?.();
+      expect(disableMock).not.toHaveBeenCalled();
+      expect(logTailscale.info).toHaveBeenCalledWith(
+        `${mode} cleanup skipped: not the current owner`,
+      );
+
+      await cleanupB?.();
+      expect(disableMock).toHaveBeenCalledTimes(1);
+    });
+
+    it("restores the previous live owner after a takeover startup failure", async () => {
+      const ownerStore = createOwnerStore();
+      const logTailscale = {
+        info: vi.fn(),
+        warn: vi.fn(),
+      };
+
+      const cleanupA = await startGatewayTailscaleExposure({
+        tailscaleMode: mode,
+        resetOnExit: true,
+        port: 18789,
+        logTailscale,
+        ownerStore,
+      });
+
+      enableMock.mockRejectedValueOnce(new Error("boom"));
+
+      const cleanupB = await startGatewayTailscaleExposure({
+        tailscaleMode: mode,
+        resetOnExit: true,
+        port: 18789,
+        logTailscale,
+        ownerStore,
+      });
+
+      expect(cleanupB).not.toBeNull();
+      expect(logTailscale.warn).toHaveBeenCalledWith(`${mode} failed: boom`);
+
+      await cleanupB?.();
+      expect(disableMock).not.toHaveBeenCalled();
+      expect(logTailscale.info).toHaveBeenCalledWith(
+        `${mode} cleanup skipped: not the current owner`,
+      );
+
+      await cleanupA?.();
+      expect(disableMock).toHaveBeenCalledTimes(1);
+    });
+
+    it("keeps the failed owner when the previous owner is already gone", async () => {
+      const ownerStore = createOwnerStore();
+      const logTailscale = {
+        info: vi.fn(),
+        warn: vi.fn(),
+      };
+
+      const cleanupA = await startGatewayTailscaleExposure({
+        tailscaleMode: mode,
+        resetOnExit: true,
+        port: 18789,
+        logTailscale,
+        ownerStore,
+      });
+
+      vi.spyOn(process, "kill").mockImplementation(((pid: number) => {
+        if (pid === process.pid) {
+          const err = new Error("gone") as NodeJS.ErrnoException;
+          err.code = "ESRCH";
+          throw err;
+        }
+        return true;
+      }) as typeof process.kill);
+      enableMock.mockRejectedValueOnce(new Error("boom"));
+
+      const cleanupB = await startGatewayTailscaleExposure({
+        tailscaleMode: mode,
+        resetOnExit: true,
+        port: 18789,
+        logTailscale,
+        ownerStore,
+      });
+
+      expect(cleanupB).not.toBeNull();
+      expect(logTailscale.warn).toHaveBeenCalledWith(`${mode} failed: boom`);
+
+      await cleanupA?.();
+      expect(disableMock).not.toHaveBeenCalled();
+      expect(logTailscale.info).toHaveBeenCalledWith(
+        `${mode} cleanup skipped: not the current owner`,
+      );
+
+      await cleanupB?.();
+      expect(disableMock).toHaveBeenCalledTimes(1);
+    });
+
+    it("reclaims cleanup from a dead newer owner before exit", async () => {
+      const ownerStore = createOwnerStore();
+      const logTailscale = {
+        info: vi.fn(),
+        warn: vi.fn(),
+      };
+
+      const cleanupA = await startGatewayTailscaleExposure({
+        tailscaleMode: mode,
+        resetOnExit: true,
+        port: 18789,
+        logTailscale,
+        ownerStore,
+      });
+      await startGatewayTailscaleExposure({
+        tailscaleMode: mode,
+        resetOnExit: true,
+        port: 18789,
+        logTailscale,
+        ownerStore,
+      });
+      ownerStore.markCurrentOwnerDead();
+
+      await cleanupA?.();
+      expect(disableMock).toHaveBeenCalledTimes(1);
+      expect(logTailscale.info).not.toHaveBeenCalledWith(
+        `${mode} cleanup skipped: not the current owner`,
+      );
+    });
+
+    it("falls back to unguarded cleanup when the ownership guard cannot claim", async () => {
+      const logTailscale = {
+        info: vi.fn(),
+        warn: vi.fn(),
+      };
+
+      const cleanup = await startGatewayTailscaleExposure({
+        tailscaleMode: mode,
+        resetOnExit: true,
+        port: 18789,
+        logTailscale,
+        ownerStore: {
+          async claim() {
+            throw new Error("lock dir unavailable");
+          },
+          async replaceIfCurrent() {
+            return false;
+          },
+          async runCleanupIfCurrentOwner() {
+            return false;
+          },
+        },
+      });
+
+      expect(cleanup).not.toBeNull();
+      expect(enableMock).toHaveBeenCalledTimes(1);
+      expect(logTailscale.warn).toHaveBeenCalledWith(
+        `${mode} ownership guard unavailable: lock dir unavailable`,
+      );
+
+      await cleanup?.();
+      expect(disableMock).toHaveBeenCalledTimes(1);
+    });
+
+    it("skips unguarded fallback while a previous cleanup is still in progress", async () => {
+      const logTailscale = {
+        info: vi.fn(),
+        warn: vi.fn(),
+      };
+
+      const cleanup = await startGatewayTailscaleExposure({
+        tailscaleMode: mode,
+        resetOnExit: true,
+        port: 18789,
+        logTailscale,
+        ownerStore: {
+          async claim() {
+            const err = new Error("busy");
+            err.name = "TailscaleExposureCleanupInProgressError";
+            throw err;
+          },
+          async replaceIfCurrent() {
+            return false;
+          },
+          async runCleanupIfCurrentOwner() {
+            return false;
+          },
+        },
+      });
+
+      expect(cleanup).toBeNull();
+      expect(enableMock).not.toHaveBeenCalled();
+      expect(disableMock).not.toHaveBeenCalled();
+      expect(logTailscale.warn).toHaveBeenCalledWith(
+        `${mode} ownership cleanup still in progress; skipping external exposure`,
+      );
+    });
+
+    it("falls back to a direct reset when guarded cleanup bookkeeping fails", async () => {
+      const logTailscale = {
+        info: vi.fn(),
+        warn: vi.fn(),
+      };
+
+      const cleanup = await startGatewayTailscaleExposure({
+        tailscaleMode: mode,
+        resetOnExit: true,
+        port: 18789,
+        logTailscale,
+        ownerStore: {
+          async claim() {
+            return {
+              owner: {
+                token: "owner-1",
+                mode,
+                port: 18789,
+                pid: process.pid,
+                claimedAt: new Date(0).toISOString(),
+                phase: "active" as const,
+              },
+              previousOwner: null,
+            };
+          },
+          async replaceIfCurrent() {
+            return true;
+          },
+          async runCleanupIfCurrentOwner() {
+            throw new Error("lock dir unavailable");
+          },
+        },
+      });
+
+      await cleanup?.();
+      expect(disableMock).toHaveBeenCalledTimes(1);
+      expect(logTailscale.warn).toHaveBeenCalledWith(
+        `${mode} cleanup failed: lock dir unavailable`,
+      );
+      expect(logTailscale.warn).toHaveBeenCalledWith(
+        `${mode} cleanup guard failed; applied direct reset fallback`,
+      );
+    });
+  },
+);

src/gateway/server-tailscale.ts

@@ -1,3 +1,7 @@
+import { randomUUID } from "node:crypto";
+import fs from "node:fs/promises";
+import path from "node:path";
+import { resolveGatewayLockDir } from "../config/paths.js";
 import {
   disableTailscaleFunnel,
   disableTailscaleServe,
@@ -6,17 +10,293 @@ import {
   getTailnetHostname,
 } from "../infra/tailscale.js";
 
+type GatewayTailscaleMode = "off" | "serve" | "funnel";
+
+type TailscaleExposureOwnerRecord = {
+  token: string;
+  mode: Exclude<GatewayTailscaleMode, "off">;
+  port: number;
+  pid: number;
+  claimedAt: string;
+  phase: "active" | "cleaning";
+  cleanupStartedAt?: string;
+};
+
+type TailscaleExposureOwnerStore = {
+  claim(
+    mode: Exclude<GatewayTailscaleMode, "off">,
+    port: number,
+  ): Promise<{
+    owner: TailscaleExposureOwnerRecord;
+    previousOwner: TailscaleExposureOwnerRecord | null;
+  }>;
+  replaceIfCurrent(token: string, nextOwner: TailscaleExposureOwnerRecord | null): Promise<boolean>;
+  runCleanupIfCurrentOwner(token: string, cleanup: () => Promise<void>): Promise<boolean>;
+};
+
+function isPidAlive(pid: number): boolean {
+  try {
+    process.kill(pid, 0);
+    return true;
+  } catch (err) {
+    return (err as NodeJS.ErrnoException | undefined)?.code !== "ESRCH";
+  }
+}
+
+function createCleanupInProgressError(pid: number): Error {
+  const err = new Error(`previous cleanup still in progress (pid ${pid})`);
+  err.name = "TailscaleExposureCleanupInProgressError";
+  return err;
+}
+
+function isCleanupInProgressError(err: unknown): err is Error {
+  return err instanceof Error && err.name === "TailscaleExposureCleanupInProgressError";
+}
+
+function createTailscaleExposureOwnerStore(): TailscaleExposureOwnerStore {
+  const ownerFilePath = path.join(resolveGatewayLockDir(), "tailscale-exposure-owner.json");
+  const ownerLockPath = path.join(resolveGatewayLockDir(), "tailscale-exposure-owner.lock");
+  const lockRetryMs = 25;
+  const lockStaleMs = 60_000;
+  const cleanupClaimWaitMs = 20_000;
+  let ensureLockDirReady: Promise<void> | null = null;
+
+  async function readOwner(): Promise<TailscaleExposureOwnerRecord | null> {
+    try {
+      const raw = await fs.readFile(ownerFilePath, "utf8");
+      const parsed = JSON.parse(raw);
+      if (
+        parsed &&
+        typeof parsed === "object" &&
+        typeof parsed.token === "string" &&
+        typeof parsed.mode === "string" &&
+        typeof parsed.port === "number" &&
+        typeof parsed.pid === "number" &&
+        typeof parsed.claimedAt === "string"
+      ) {
+        return {
+          ...(parsed as Omit<TailscaleExposureOwnerRecord, "phase">),
+          phase: parsed.phase === "cleaning" ? "cleaning" : "active",
+          cleanupStartedAt:
+            typeof parsed.cleanupStartedAt === "string" ? parsed.cleanupStartedAt : undefined,
+        };
+      }
+    } catch {
+      // ENOENT means the file does not exist yet. Any other parse/read error is
+      // also ignored so the ownership guard remains best-effort and non-fatal.
+    }
+    return null;
+  }
+
+  async function sleep(ms: number) {
+    await new Promise((resolve) => setTimeout(resolve, ms));
+  }
+
+  function ensureLockDir() {
+    if (!ensureLockDirReady) {
+      ensureLockDirReady = fs
+        .mkdir(path.dirname(ownerLockPath), { recursive: true })
+        .catch((err: unknown) => {
+          ensureLockDirReady = null;
+          throw err;
+        });
+    }
+    return ensureLockDirReady;
+  }
+
+  async function breakStaleLock() {
+    try {
+      const stat = await fs.stat(ownerLockPath);
+      if (Date.now() - stat.mtimeMs < lockStaleMs) {
+        return;
+      }
+      try {
+        const raw = await fs.readFile(ownerLockPath, "utf8");
+        const parsed = JSON.parse(raw) as { pid?: unknown };
+        if (typeof parsed.pid === "number" && isPidAlive(parsed.pid)) {
+          return;
+        }
+      } catch {
+        // Unreadable lock state is treated as stale so a dead holder cannot block recovery.
+      }
+      await fs.unlink(ownerLockPath).catch(() => {});
+    } catch {
+      // Ignore malformed or unreadable lock state and retry.
+    }
+  }
+
+  async function withOwnerLock<T>(fn: () => Promise<T>): Promise<T> {
+    await ensureLockDir();
+
+    while (true) {
+      try {
+        const handle = await fs.open(ownerLockPath, "wx");
+        try {
+          await handle.writeFile(
+            JSON.stringify({ pid: process.pid, acquiredAt: new Date().toISOString() }),
+          );
+          return await fn();
+        } finally {
+          await handle.close().catch(() => {});
+          await fs.unlink(ownerLockPath).catch(() => {});
+        }
+      } catch (err) {
+        if ((err as NodeJS.ErrnoException | undefined)?.code !== "EEXIST") {
+          throw err;
+        }
+        await breakStaleLock();
+        await sleep(lockRetryMs);
+      }
+    }
+  }
+
+  async function deleteOwnerFile() {
+    await fs.unlink(ownerFilePath).catch((err: unknown) => {
+      if ((err as NodeJS.ErrnoException | undefined)?.code !== "ENOENT") {
+        throw err;
+      }
+    });
+  }
+
+  return {
+    async claim(mode, port) {
+      const claimDeadline = Date.now() + cleanupClaimWaitMs;
+      while (true) {
+        const result = await withOwnerLock(async () => {
+          const previousOwner = await readOwner();
+          if (previousOwner?.phase === "cleaning" && isPidAlive(previousOwner.pid)) {
+            if (Date.now() < claimDeadline) {
+              return { type: "wait" as const };
+            }
+            return { type: "blocked" as const, previousOwner };
+          }
+
+          const owner: TailscaleExposureOwnerRecord = {
+            token: randomUUID(),
+            mode,
+            port,
+            pid: process.pid,
+            claimedAt: new Date().toISOString(),
+            phase: "active",
+          };
+          await fs.writeFile(ownerFilePath, JSON.stringify(owner), "utf8");
+          return { type: "claimed" as const, owner, previousOwner };
+        });
+
+        if (result.type === "claimed") {
+          return result;
+        }
+        if (result.type === "blocked") {
+          throw createCleanupInProgressError(result.previousOwner.pid);
+        }
+        await sleep(lockRetryMs);
+      }
+    },
+    async replaceIfCurrent(token, nextOwner) {
+      return await withOwnerLock(async () => {
+        const current = await readOwner();
+        if (current?.token !== token) {
+          return false;
+        }
+        if (nextOwner) {
+          await fs.writeFile(ownerFilePath, JSON.stringify(nextOwner), "utf8");
+        } else {
+          await deleteOwnerFile();
+        }
+        return true;
+      });
+    },
+    async runCleanupIfCurrentOwner(token, cleanup) {
+      const cleanupOwner = await withOwnerLock(async () => {
+        const current = await readOwner();
+        if (!current) {
+          return null;
+        }
+        if (current.token !== token && isPidAlive(current.pid)) {
+          return null;
+        }
+        // If a newer owner died without cleaning up, reclaim its stale exposure
+        // before this older process exits so resetOnExit still clears Tailscale.
+        // Mark cleanup in progress before releasing the lock so overlapping
+        // startups cannot claim exposure until this reset finishes or fails.
+        const nextOwner: TailscaleExposureOwnerRecord = {
+          ...current,
+          phase: "cleaning",
+          cleanupStartedAt: new Date().toISOString(),
+        };
+        await fs.writeFile(ownerFilePath, JSON.stringify(nextOwner), "utf8");
+        return nextOwner;
+      });
+      if (!cleanupOwner) {
+        return false;
+      }
+
+      try {
+        await cleanup();
+      } catch (err) {
+        await withOwnerLock(async () => {
+          const current = await readOwner();
+          if (current?.token !== token || current.phase !== "cleaning") {
+            return;
+          }
+          await fs.writeFile(
+            ownerFilePath,
+            JSON.stringify({
+              ...cleanupOwner,
+              phase: "active",
+              cleanupStartedAt: undefined,
+            }),
+            "utf8",
+          );
+        }).catch(() => {});
+        throw err;
+      }
+
+      await withOwnerLock(async () => {
+        const current = await readOwner();
+        if (current?.token !== token || current.phase !== "cleaning") {
+          return;
+        }
+        await deleteOwnerFile();
+      }).catch(() => {
+        // Tailscale cleanup already succeeded. If owner-file deletion fails, leave
+        // the stale cleaning record for best-effort recovery after this process exits.
+      });
+      return true;
+    },
+  };
+}
+
 export async function startGatewayTailscaleExposure(params: {
-  tailscaleMode: "off" | "serve" | "funnel";
+  tailscaleMode: GatewayTailscaleMode;
   resetOnExit?: boolean;
   port: number;
   controlUiBasePath?: string;
   logTailscale: { info: (msg: string) => void; warn: (msg: string) => void };
+  ownerStore?: TailscaleExposureOwnerStore;
 }): Promise<(() => Promise<void>) | null> {
   if (params.tailscaleMode === "off") {
     return null;
   }
 
+  const ownerStore = params.ownerStore ?? createTailscaleExposureOwnerStore();
+  let owner: TailscaleExposureOwnerRecord | null = null;
+  let previousOwner: TailscaleExposureOwnerRecord | null = null;
+
+  try {
+    ({ owner, previousOwner } = await ownerStore.claim(params.tailscaleMode, params.port));
+  } catch (err) {
+    if (isCleanupInProgressError(err)) {
+      params.logTailscale.warn(
+        `${params.tailscaleMode} ownership cleanup still in progress; skipping external exposure`,
+      );
+      return null;
+    }
+    params.logTailscale.warn(
+      `${params.tailscaleMode} ownership guard unavailable: ${err instanceof Error ? err.message : String(err)}`,
+    );
+  }
+
   try {
     if (params.tailscaleMode === "serve") {
       await enableTailscaleServe(params.port);
@@ -33,6 +313,18 @@ export async function startGatewayTailscaleExposure(params: {
       params.logTailscale.info(`${params.tailscaleMode} enabled`);
     }
   } catch (err) {
+    if (owner) {
+      // Restore the previous owner's original token so its own cleanup hook can
+      // still prove ownership later, or keep this failed owner if it needs to
+      // reset any partial/orphaned Tailscale state on exit.
+      const nextOwner =
+        previousOwner && isPidAlive(previousOwner.pid)
+          ? previousOwner
+          : params.resetOnExit
+            ? owner
+            : null;
+      await ownerStore.replaceIfCurrent(owner.token, nextOwner).catch(() => {});
+    }
     params.logTailscale.warn(
       `${params.tailscaleMode} failed: ${err instanceof Error ? err.message : String(err)}`,
     );
@@ -42,17 +334,46 @@ export async function startGatewayTailscaleExposure(params: {
     return null;
   }
 
-  return async () => {
-    try {
+  const disableExposure = async () => {
     if (params.tailscaleMode === "serve") {
       await disableTailscaleServe();
     } else {
       await disableTailscaleFunnel();
     }
+  };
+
+  return async () => {
+    try {
+      if (owner) {
+        // A failed enable can still leave behind partial or orphaned Tailscale
+        // config, so shutdown cleanup intentionally re-runs the global reset.
+        const cleanedUp = await ownerStore.runCleanupIfCurrentOwner(owner.token, async () => {
+          await disableExposure();
+        });
+        if (!cleanedUp) {
+          params.logTailscale.info(
+            `${params.tailscaleMode} cleanup skipped: not the current owner`,
+          );
+        }
+        return;
+      }
+
+      await disableExposure();
     } catch (err) {
       params.logTailscale.warn(
         `${params.tailscaleMode} cleanup failed: ${err instanceof Error ? err.message : String(err)}`,
       );
+      if (!owner) {
+        return;
+      }
+      try {
+        await disableExposure();
+        params.logTailscale.warn(
+          `${params.tailscaleMode} cleanup guard failed; applied direct reset fallback`,
+        );
+      } catch {
+        // The direct reset failed too; keep the original warning above.
+      }
     }
   };
 }