fix(client): resolve STUN hostnames in the main process

Chromium's P2P socket manager failed every STUN hostname with
ERR_NAME_NOT_RESOLVED in a restricted-resolver environment (a Windows KVM
guest), even though its own general network stack, the OS resolver and
Node's resolver all resolved the same names -- and mapping the names to IPs
with --host-resolver-rules changed nothing, so it is not ordinary
resolution. WebRTC was left with no server-reflexive candidate.

The desktop client now resolves the STUN hostnames in the main process
(`ice:resolve-stun`, Node's dns.resolve4) and hands `transport.js` the
IP form; a name that will not resolve (the decommissioned Mozilla host) is
dropped. In a browser there is no `meshbay` bridge and the hostnames are
used unchanged -- a browser resolves them fine, so that path is untouched.
Falls back to the hostname form if the bridge call throws.

Also, scoped to win32: disable WebRtcHideLocalIpsWithMdns, so the client
publishes its real local IP instead of a `.local` name the node's ICE stack
cannot resolve across the KVM bridge. Changes nothing on Linux/macOS.
Test-env workaround, revisit before release.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

2 files changed, 34 insertions, 0 deletions

diff --git a/packages/meshbay-client/src/main.js b/packages/meshbay-client/src/main.js
index 2a97246..9c27cfe 100644
--- a/packages/meshbay-client/src/main.js
+++ b/packages/meshbay-client/src/main.js
@@ -40,6 +40,17 @@ const { pathToFileURL } = require('node:url');
 // runs (`electron .`) consistent with it.
 app.commandLine.appendSwitch('class', 'MeshBay');
 
+// TEST-ENV WORKAROUND (Windows libvirt/KVM guest) — REVISIT BEFORE RELEASE.
+// In that guest Chromium hides the host candidate behind a random `.local`
+// mDNS name that the node's ICE stack cannot resolve across the KVM bridge,
+// so the one working candidate pair is present on some attempts and missing
+// on others (60 s ICE timeouts, "2nd connection hangs"). Publishing the real
+// local IP removes the dependency. Scoped to win32 so it changes nothing on
+// Linux/macOS, where mDNS concealment works and should stay on.
+if (process.platform === 'win32') {
+  app.commandLine.appendSwitch('disable-features', 'WebRtcHideLocalIpsWithMdns');
+}
+
 const UI_DIR = path.join(__dirname, '..', 'ui');
 const SCHEME = 'app';
 
@@ -497,6 +508,23 @@ function registerBridge() {
     };
   });
 
+  ipcMain.handle('ice:resolve-stun', async (_e, urls) => {
+    const dns = require('node:dns').promises;
+    const list = Array.isArray(urls) ? urls : [];
+    const out = [];
+    for (const u of list) {
+      const m = /^(stuns?):(\[?[^\]]+\]?|[^:]+):(\d+)$/.exec(String(u));
+      if (!m) { out.push(String(u)); continue; }
+      const [, scheme, host, port] = m;
+      if (/^[\d.]+$/.test(host) || host.includes(':')) { out.push(String(u)); continue; }
+      try {
+        const [ip] = await dns.resolve4(host);
+        if (ip) out.push(`${scheme}:${ip}:${port}`);
+      } catch { /* unresolvable (e.g. a decommissioned host) — drop it */ }
+    }
+    return out;
+  });
+
   ipcMain.handle('hub:probe', async (_e, url) => {
     const target = String(url || config.hubBase || '').replace(/\/+$/, '');
     if (!target) return null;
diff --git a/packages/meshbay-client/src/preload.js b/packages/meshbay-client/src/preload.js
index 7ffdf66..96d6790 100644
--- a/packages/meshbay-client/src/preload.js
+++ b/packages/meshbay-client/src/preload.js
@@ -47,6 +47,12 @@ contextBridge.exposeInMainWorld('meshbay', {
   // which CORS refuses and which is not a credential anyway.
   fetch: (url, init) => ipcRenderer.invoke('hub:fetch', url, init),
 
+  // Resolve STUN `stun:host:port` URLs to `stun:ip:port` using Node's resolver.
+  // Chromium's P2P socket manager fails STUN hostnames outright in some
+  // restricted-resolver environments; the renderer cannot do DNS, so it asks
+  // here. Unresolvable entries are dropped.
+  resolveStun: (urls) => ipcRenderer.invoke('ice:resolve-stun', urls),
+
   // The device's hub key. Generated, held and used entirely in the main
   // process: the interface asks for a signature and never sees a key, because
   // it is the part of this application that parses hostile input.