RPC Binder: Shut down the session on disconnect

For parity with the Android code, RpcServerTrusty now
calls shutdownAndWait whenever a channel disconnects.
This should also mitigate some server-side leaks, since
the session shutdown code also clears RpcState.

Bug: 267235876
Test: trusty_stats_test 80 times consecutively
Change-Id: I35c3cd9fd419aa51e70297d1ffe3aa5dab7a0816
diff --git a/libs/binder/trusty/RpcServerTrusty.cpp b/libs/binder/trusty/RpcServerTrusty.cpp
index 109da75..3a99606 100644
--- a/libs/binder/trusty/RpcServerTrusty.cpp
+++ b/libs/binder/trusty/RpcServerTrusty.cpp
@@ -154,8 +154,18 @@
     return NO_ERROR;
 }
 
-void RpcServerTrusty::handleDisconnect(const tipc_port* /*port*/, handle_t /*chan*/,
-                                       void* /*ctx*/) {}
+void RpcServerTrusty::handleDisconnect(const tipc_port* /*port*/, handle_t /*chan*/, void* ctx) {
+    auto* channelContext = reinterpret_cast<ChannelContext*>(ctx);
+    if (channelContext == nullptr) {
+        // Connections marked "incoming" (outgoing from the server's side)
+        // do not have a valid channel context because joinFn does not get
+        // called for them. We ignore them here.
+        return;
+    }
+
+    auto& session = channelContext->session;
+    (void)session->shutdownAndWait(false);
+}
 
 void RpcServerTrusty::handleChannelCleanup(void* ctx) {
     auto* channelContext = reinterpret_cast<ChannelContext*>(ctx);