libbinder: RpcConnection: add ID

In preparation to have the server be able to distinguish clients and
clients to be able to dynamically create threads that are assigned to
them.

Future considerations:
- make ID impossible to guess (right now, one client might be able to
  get ahold of a thread from a server). We may implement something here
  or go for something existing like TLS.
- combine getting max threads and this? will wait until dynamic threads
  are actually implemented and we know we need this ID and we're looking
  at performance. For now this is a placeholder to enable dynamic client
  APIs.

Bug: 185167543
Test: binderRpcTest
Change-Id: If8563c69930c23b9ca91090b4f59ef1f51073f24

1 files changed, 29 insertions, 4 deletions

diff --git a/libs/binder/RpcConnection.cpp b/libs/binder/RpcConnection.cpp
index 930bcbde62..95eba87b68 100644
--- a/libs/binder/RpcConnection.cpp
+++ b/libs/binder/RpcConnection.cpp
@@ -115,6 +115,24 @@ status_t RpcConnection::sendDecStrong(const RpcAddress& address) {
     return state()->sendDecStrong(socket.fd(), address);
 }
 
+status_t RpcConnection::readId() {
+    {
+        std::lock_guard<std::mutex> _l(mSocketMutex);
+        LOG_ALWAYS_FATAL_IF(mForServer != nullptr, "Can only update ID for client.");
+    }
+
+    int32_t id;
+
+    ExclusiveSocket socket(sp<RpcConnection>::fromExisting(this), SocketUse::CLIENT);
+    status_t status =
+            state()->getConnectionId(socket.fd(), sp<RpcConnection>::fromExisting(this), &id);
+    if (status != OK) return status;
+
+    LOG_RPC_DETAIL("RpcConnection %p has id %d", this, id);
+    mId = id;
+    return OK;
+}
+
 void RpcConnection::join(unique_fd client) {
     // must be registered to allow arbitrary client code executing commands to
     // be able to do nested calls (we can't only read from it)
@@ -134,10 +152,6 @@ void RpcConnection::join(unique_fd client) {
                         "bad state: socket object guaranteed to be in list");
 }
 
-void RpcConnection::setForServer(const wp<RpcServer>& server) {
-    mForServer = server;
-}
-
 wp<RpcServer> RpcConnection::server() {
     return mForServer;
 }
@@ -162,6 +176,12 @@ bool RpcConnection::setupSocketClient(const RpcSocketAddress& addr) {
         return false;
     }
 
+    if (status_t status = readId(); status != OK) {
+        ALOGE("Could not get connection id after initial connection to %s; %s",
+              addr.toString().c_str(), statusToString(status).c_str());
+        return false;
+    }
+
     // we've already setup one client
     for (size_t i = 0; i + 1 < numThreadsAvailable; i++) {
         // TODO(b/185167543): avoid race w/ accept4 not being called on server
@@ -202,6 +222,11 @@ void RpcConnection::addClient(unique_fd fd) {
     mClients.push_back(connection);
 }
 
+void RpcConnection::setForServer(const wp<RpcServer>& server, int32_t connectionId) {
+    mId = connectionId;
+    mForServer = server;
+}
+
 sp<RpcConnection::ConnectionSocket> RpcConnection::assignServerToThisThread(unique_fd fd) {
     std::lock_guard<std::mutex> _l(mSocketMutex);
     sp<ConnectionSocket> connection = sp<ConnectionSocket>::make();