libbinder: Stricter protocol and code for receiving FDs
This is a slight change the to wire protocol. Now out-of-band FDs must
be sent along with the command header bytes.
The code changes exploit that by only using the more complex `recvmsg`
call when reading the command header. Additionally, we explicitly pass
around the list of FDs so that there is no risk of accumulating them.
The same (somewhat ugly) vector type is used everywhere now so that
there is only one allocation to capture the FDs and pass them to the
`Parcel` object.
Test: binderRpcTest
Bug: 185909244
Change-Id: I1f55995ca82338ab9716fb2246c954ac8b16cfe5
diff --git a/libs/binder/RpcWireFormat.h b/libs/binder/RpcWireFormat.h
index 13989e5..ff1b01a 100644
--- a/libs/binder/RpcWireFormat.h
+++ b/libs/binder/RpcWireFormat.h
@@ -109,6 +109,10 @@
// serialization is like:
// |RpcWireHeader|struct desginated by 'command'| (over and over again)
+//
+// When file descriptors are included in out-of-band data (e.g. in unix domain
+// sockets), they are always paired with the RpcWireHeader bytes of the
+// transaction or reply the file descriptors belong to.
struct RpcWireHeader {
uint32_t command; // RPC_COMMAND_*