fix(spa): say when the device refuses the local network

Android 17 makes the local network a permission of the application, and
Chrome 155 targets it: without it the node's LAN addresses are dropped
and a group on the phone's own Wi-Fi failed with "DataChannel closed".
The transport now names that refusal and the group page says what to
allow.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 84 insertions, 5 deletions

diff --git a/packages/meshbay-hub/src/meshbay_hub/static/transport.js b/packages/meshbay-hub/src/meshbay_hub/static/transport.js
index 15c7b09a..0d987d9a 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/transport.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/transport.js
@@ -103,6 +103,71 @@ function _retiredBundleError() {
   return err;
 }
 
+// ── A device that refuses the local network ──────────────────────────────────
+//
+// Android 17 makes reaching the local network a permission of the application
+// (ACCESS_LOCAL_NETWORK), enforced for any application that targets it. Chrome
+// does from 155, and holds the permission only once the person grants it. Until
+// then the browser drops the node's addresses on the phone's own subnet: they
+// are absent from getStats, no check goes out to them, the node's own checks
+// get no answer, ICE fails and the channel closes. "DataChannel closed" was all
+// this page could say, and on mobile data the same group opened, over the
+// node's public address. Measured on a Pixel, Android 17, Chrome 155,
+// 2026-10-16 (tests/test_local_network_refused.py).
+
+const _PRIVATE_V4 = /^(10\.|192\.168\.|172\.(1[6-9]|2\d|3[01])\.)/;
+const _IPV4 = /^\d{1,3}(\.\d{1,3}){3}$/;
+
+function _sdpCandidates(sdp) {
+  const out = [];
+  for (const line of String(sdp || '').split(/\r?\n/)) {
+    if (!line.startsWith('a=candidate:')) continue;
+    const parts = line.split(' ');
+    if (parts.length >= 8) out.push({ address: parts[4], type: parts[7] });
+  }
+  return out;
+}
+
+const _slash24 = (address) => address.split('.').slice(0, 3).join('.');
+
+/**
+ * Whether this device dropped the node's local addresses rather than failed to
+ * reach them.
+ *
+ * A browser pairs every remote address of a family with each local candidate
+ * of that family, and getStats lists each one that was paired, answered or
+ * not: desktop Chrome 152, 155 and 157 listed all six of a node's. So a private
+ * IPv4 address of the node that is missing, while we have IPv4 of our own, was
+ * refused here. A desktop browser hides its own addresses behind `.local`
+ * names, which are on a local network by construction. With nothing paired at
+ * all there is no comparison to make, and only an address on our own subnet
+ * says it.
+ */
+function localNetworkRefused(offerSdp, answerSdp, remoteAddresses) {
+  const paired = new Set(remoteAddresses);
+  const refused = _sdpCandidates(answerSdp)
+    .filter((c) => c.type === 'host' && _PRIVATE_V4.test(c.address) && !paired.has(c.address))
+    .map((c) => c.address);
+  if (!refused.length) return false;
+  const ours = _sdpCandidates(offerSdp);
+  const ourV4 = ours.filter((c) => _IPV4.test(c.address)).map((c) => c.address);
+  if (!ourV4.length && !ours.some((c) => c.address.endsWith('.local'))) return false;
+  if (paired.size > 0) return true;
+  return ourV4.some((a) => refused.some((r) => _slash24(r) === _slash24(a)));
+}
+
+async function _localNetworkRefusedBy(pc, offerSdp, answerSdp) {
+  try {
+    const remote = [];
+    (await pc.getStats()).forEach((r) => {
+      if (r.type === 'remote-candidate') remote.push(r.address || r.ip);
+    });
+    return localNetworkRefused(offerSdp, answerSdp, remote);
+  } catch {
+    return false;   // a closed connection has no stats: the old error stands
+  }
+}
+
 // Segments of 256 KB: 24 in flight is 6 MB, enough to keep playback fed over a
 // slow link and small enough that nothing accumulates.
 // How long to collect ICE candidates before sending the offer anyway. Long
@@ -886,6 +951,9 @@ class MeshBayTransport {
     // whatever is current — the `pc === this._pc` check below is what that
     // buys.
     const pc = this._pc;
+    // Whether a candidate pair ever answered on this connection: a failure
+    // after that is not the local network being refused.
+    let iceReached = false;
     pc.onconnectionstatechange = () => {
       console.log('[MeshBay] PC state:', pc.connectionState);
       trace('pc_state', { state: pc.connectionState });
@@ -913,10 +981,9 @@ class MeshBayTransport {
       // `connected`/`completed` is the first moment this browser knows the peer
       // is there at all: a candidate pair answered. `checking` is not — it is
       // this side trying addresses that may all be dead.
-      if (pc === this._pc
-          && (pc.iceConnectionState === 'connected'
-           || pc.iceConnectionState === 'completed')) {
-        this._noteConnectProgress('ice_connected');
+      if (pc.iceConnectionState === 'connected' || pc.iceConnectionState === 'completed') {
+        iceReached = true;
+        if (pc === this._pc) this._noteConnectProgress('ice_connected');
       }
     };
 
@@ -1029,9 +1096,20 @@ class MeshBayTransport {
 
     const answer = await resp.json();
     this._rawAnswerSdp = answer.sdp;
+    const offerSdp = this._pc.localDescription.sdp;
     await this._pc.setRemoteDescription({ type: 'answer', sdp: answer.sdp });
 
-    await channelReady;
+    try {
+      await channelReady;
+    } catch (err) {
+      if (!iceReached && await _localNetworkRefusedBy(pc, offerSdp, answer.sdp)) {
+        trace('local_network_refused', {});
+        const refused = new Error('This device refused to reach the local network');
+        refused.reason = 'local_network_blocked';
+        throw refused;
+      }
+      throw err;
+    }
     console.log('[MeshBay] DataChannel open, sending handshake for group', groupId,
                 'channel=', this._channel?.readyState,
                 'crypto=', !!window.MeshBayCrypto);
@@ -2581,4 +2659,5 @@ function extendTransport(part) {
 }
 
 // Export
+MeshBayTransport.localNetworkRefused = localNetworkRefused;
 window.MeshBayTransport = MeshBayTransport;