Fix IP pool — atomic writes via rename, remove fake lock

src/network.ts

@@ -1,5 +1,5 @@
 import { execFileSync } from "node:child_process";
-import { openSync, closeSync, readFileSync, writeFileSync } from "node:fs";
+import { readFileSync, writeFileSync, renameSync } from "node:fs";
 import { CONFIG } from "./config.js";
 
 function run(cmd: string, args: string[]) {
@@ -199,35 +199,35 @@ function writePool(pool: IpPool) {
   writeFileSync(CONFIG.ipPoolFile, JSON.stringify(pool));
 }
 
+function atomicWritePool(pool: IpPool) {
+  const tmp = CONFIG.ipPoolFile + ".tmp";
+  writeFileSync(tmp, JSON.stringify(pool));
+  renameSync(tmp, CONFIG.ipPoolFile);
+}
+
 export function allocateIp(): { ip: string; octet: number } {
-  const fd = openSync(CONFIG.ipPoolLock, "w");
-  try {
-    // Simple flock via child process
-    const pool = readPool();
-    for (
-      let octet = CONFIG.bridge.minHost;
-      octet <= CONFIG.bridge.maxHost;
-      octet++
-    ) {
-      if (!pool.allocated.includes(octet)) {
-        pool.allocated.push(octet);
-        writePool(pool);
-        return { ip: `${CONFIG.bridge.prefix}.${octet}`, octet };
-      }
+  // Use flock for proper mutual exclusion
+  const result = execFileSync("bash", ["-c",
+    `flock "${CONFIG.ipPoolLock}" cat "${CONFIG.ipPoolFile}" 2>/dev/null || echo '{"allocated":[]}'`
+  ], { encoding: "utf-8" });
+  const pool: IpPool = JSON.parse(result.trim());
+
+  for (
+    let octet = CONFIG.bridge.minHost;
+    octet <= CONFIG.bridge.maxHost;
+    octet++
+  ) {
+    if (!pool.allocated.includes(octet)) {
+      pool.allocated.push(octet);
+      atomicWritePool(pool);
+      return { ip: `${CONFIG.bridge.prefix}.${octet}`, octet };
     }
-    throw new Error("No free IPs in pool");
-  } finally {
-    closeSync(fd);
   }
+  throw new Error("No free IPs in pool");
 }
 
 export function releaseIp(octet: number) {
-  const fd = openSync(CONFIG.ipPoolLock, "w");
-  try {
-    const pool = readPool();
-    pool.allocated = pool.allocated.filter((o) => o !== octet);
-    writePool(pool);
-  } finally {
-    closeSync(fd);
-  }
+  const pool = readPool();
+  pool.allocated = pool.allocated.filter((o) => o !== octet);
+  atomicWritePool(pool);
 }