libbinder: RPC know when connections setup
Previously, there was a race where:
a. client creates connection to server
b. client sends request for reverse connection to server (but this
may still be traveling on the wire)
c. client sends transaction to server
d. server tries to make a callback
e. server fails to make callback because no reverse connection is setup
Now, when a new connection is setup, a header on this connection is
setup. So, we can wait on this header to be received in (b).
Note: currently, (e) results in an abort, this is tracked in b/167966510
with a TODO in the ExclusiveConnection code. This would make a less
obvious flake (or perhaps the problem would be ignored), but this race
still needs to be fixed for well-behaved clients to be able to function
reliably.
Fixes: 190639665
Test: binderRpcTest (callback test 10,000s of times)
Change-Id: I13bc912692d63ea73d46c5441fa7d51121df2f58
diff --git a/libs/binder/RpcWireFormat.h b/libs/binder/RpcWireFormat.h
index 649c1ee..b5e5bc1 100644
--- a/libs/binder/RpcWireFormat.h
+++ b/libs/binder/RpcWireFormat.h
@@ -26,12 +26,28 @@
RPC_CONNECTION_OPTION_REVERSE = 0x1,
};
+/**
+ * This is sent to an RpcServer in order to request a new connection is created,
+ * either as part of a new session or an existing session
+ */
struct RpcConnectionHeader {
int32_t sessionId;
uint8_t options;
uint8_t reserved[3];
};
+#define RPC_CONNECTION_INIT_OKAY "cci"
+
+/**
+ * Whenever a client connection is setup, this is sent as the initial
+ * transaction. The main use of this is in order to control the timing for when
+ * a reverse connection is setup.
+ */
+struct RpcClientConnectionInit {
+ char msg[4];
+ uint8_t reserved[4];
+};
+
enum : uint32_t {
/**
* follows is RpcWireTransaction, if flags != oneway, reply w/ RPC_COMMAND_REPLY expected