aes67-ESP32-P4/components/spotify/patches/cspot/0001-mercury-reconnect-race-pr3.patch

From philippe44/cspot PR #3 (open, 2026-08): "MercurySession: crash when a request
races the reconnection (null conn/shanConn)". Our sessions reconnect every ~6 min, so the
race is hit regularly. Drop this patch once the fix is in the pinned cspot commit.

diff --git a/cspot/include/Session.h b/cspot/include/Session.h
index df7f03c8..7cc8e32f 100644
--- a/cspot/include/Session.h
+++ b/cspot/include/Session.h
@@ -2,6 +2,7 @@
 
 #include <stdint.h>  // for uint8_t
 #include <memory>    // for shared_ptr, unique_ptr
+#include <mutex>     // for mutex
 #include <string>    // for string
 #include <vector>    // for vector
 
@@ -23,6 +24,11 @@ class Session {
   std::shared_ptr<cspot::PlainConnection> conn;
   std::shared_ptr<LoginBlob> authBlob;
 
+  /* conn and shanConn are swapped by the session's task during reconnection,
+   * but other tasks send through them; they must hold this while copying the
+   * pointers, and the session's task while replacing them */
+  std::mutex connMutex;
+
   std::string deviceId = "142137fd329622137a14901634264e6f332e2411";
 
  public:
diff --git a/cspot/src/MercurySession.cpp b/cspot/src/MercurySession.cpp
index 7aafbb76..29a6e546 100644
--- a/cspot/src/MercurySession.cpp
+++ b/cspot/src/MercurySession.cpp
@@ -66,8 +66,11 @@ void MercurySession::reconnect() {
   isReconnecting = true;
 
   try {
-    this->conn = nullptr;
-    this->shanConn = nullptr;
+    {
+      std::scoped_lock lock(connMutex);
+      this->conn = nullptr;
+      this->shanConn = nullptr;
+    }
 
     this->connectWithRandomAp();
     this->authenticate(this->authBlob);
@@ -127,7 +130,17 @@ void MercurySession::unregisterAudioKey(uint32_t sequenceId) {
 void MercurySession::disconnect() {
   CSPOT_LOG(info, "Disconnecting mercury session");
   this->isRunning = false;
-  conn->close();
+
+  /* conn is null while a reconnection is in flight; isRunning above already
+   * makes the retry loop exit, closing is just to unblock a pending read */
+  std::shared_ptr<PlainConnection> conn;
+  {
+    std::scoped_lock lock(connMutex);
+    conn = this->conn;
+  }
+  if (conn)
+    conn->close();
+
   std::scoped_lock lock(this->isRunningMutex);
 }
 
@@ -305,8 +318,22 @@ uint64_t MercurySession::executeSubscription(RequestType method,
   // Bump sequence id
   this->sequenceId += 1;
 
+  /* the session's task may be swapping shanConn for a reconnection right now,
+   * and dereferencing it here would not be a catchable failure, so take a
+   * snapshot; when disconnected, the request is simply lost */
+  std::shared_ptr<ShannonConnection> shanConn;
+  {
+    std::scoped_lock lock(connMutex);
+    shanConn = this->shanConn;
+  }
+
+  if (!shanConn) {
+    CSPOT_LOG(info, "Mercury request skipped, session is reconnecting");
+    return this->sequenceId - 1;
+  }
+
   try {
-    this->shanConn->sendPacket(
+    shanConn->sendPacket(
         static_cast<std::underlying_type<RequestType>::type>(method),
         sequenceIdBytes);
   } catch (...) {
@@ -337,8 +364,21 @@ uint32_t MercurySession::requestAudioKey(const std::vector<uint8_t>& trackId,
 
   // Used for broken connection detection
   // this->lastRequestTimestamp = timeProvider->getSyncedTimestamp();
+
+  // same snapshot as executeSubscription: this runs on the track queue's task
+  std::shared_ptr<ShannonConnection> shanConn;
+  {
+    std::scoped_lock lock(connMutex);
+    shanConn = this->shanConn;
+  }
+
+  if (!shanConn) {
+    CSPOT_LOG(info, "Audio key request skipped, session is reconnecting");
+    return audioKeySequence - 1;
+  }
+
   try {
-    this->shanConn->sendPacket(
+    shanConn->sendPacket(
         static_cast<uint8_t>(RequestType::AUDIO_KEY_REQUEST_COMMAND), buffer);
   } catch (...) {
     // @TODO: Handle disconnect
diff --git a/cspot/src/Session.cpp b/cspot/src/Session.cpp
index 74bd0633..be154bbe 100644
--- a/cspot/src/Session.cpp
+++ b/cspot/src/Session.cpp
@@ -4,6 +4,7 @@
 #include <cstdint>      // for uint8_t
 #include <functional>   // for __base
 #include <memory>       // for shared_ptr, unique_ptr, make_unique
+#include <mutex>        // for scoped_lock
 #include <random>       // for default_random_engine, independent_bi...
 #include <type_traits>  // for remove_extent_t
 #include <utility>      // for move
@@ -33,7 +34,10 @@ Session::Session() {
 Session::~Session() {}
 
 void Session::connect(std::unique_ptr<cspot::PlainConnection> connection) {
-  this->conn = std::move(connection);
+  {
+    std::scoped_lock lock(connMutex);
+    this->conn = std::move(connection);
+  }
   conn->timeoutHandler = [this]() {
     return this->triggerTimeout();
   };
@@ -48,11 +52,15 @@ void Session::connect(std::unique_ptr<cspot::PlainConnection> connection) {
   CSPOT_LOG(debug, "Received shannon keys");
 
   // Generates the public and priv key
-  this->shanConn = std::make_shared<ShannonConnection>();
+  auto shanConn = std::make_shared<ShannonConnection>();
+
+  // Init shanno-encrypted connection, and only then publish it so another
+  // task cannot pick up a connection that is not wrapped yet
+  shanConn->wrapConnection(this->conn, challenges->shanSendKey,
+                           challenges->shanRecvKey);
 
-  // Init shanno-encrypted connection
-  this->shanConn->wrapConnection(this->conn, challenges->shanSendKey,
-                                 challenges->shanRecvKey);
+  std::scoped_lock lock(connMutex);
+  this->shanConn = shanConn;
 }
 
 void Session::connectWithRandomAp() {
diff --git a/cspot/src/TrackReference.cpp b/cspot/src/TrackReference.cpp
index b4fafcb5..203fe041 100644
--- a/cspot/src/TrackReference.cpp
+++ b/cspot/src/TrackReference.cpp
@@ -43,9 +43,9 @@ bool TrackReference::pbEncodeTrackList(pb_ostream_t* stream,
   // concurrent rebuild cannot reallocate the vector under us
   std::scoped_lock lock(*locked->mutex);
   auto& trackQueue = *locked->tracks;
-#ifdef ESP_PLATFORM  
+#ifdef ESP_PLATFORM
   static TrackRef msg = TrackRef_init_zero;
-#else  
+#else
   TrackRef msg = TrackRef_init_zero;
 #endif