Rust new_vsock use assigned port feature

The RpcServer::setupVsockServer allows callers to pass VMADDR_PORT_ANY
as the port to use any available port number to create the vsock
connection on.
This change uses that functionality in the available Rust types.

Test: atest vm_accessor_test
Bug: 372381104

Change-Id: I482ea58149f1989258164511191f256fc563a8d9

Author: devinmoore-goog

libs/binder/include_rpc_unstable/binder_rpc_unstable.hpp

@@ -37,8 +37,12 @@ enum class ARpcSession_FileDescriptorTransportMode {
 // Set `cid` to VMADDR_CID_LOCAL to only bind to the local vsock interface.
 // Returns an opaque handle to the running server instance, or null if the server
 // could not be started.
+// Set |port| to VMADDR_PORT_ANY to pick an available ephemeral port.
+// |assignedPort| will be set to the assigned port number if it is not null.
+// This will be the provided |port|, or the chosen available ephemeral port when
+// |port| is VMADDR_PORT_ANY.
 [[nodiscard]] ARpcServer* ARpcServer_newVsock(AIBinder* service, unsigned int cid,
-                                              unsigned int port);
+                                              unsigned int port, unsigned int* assignedPort);
 
 // Starts a Unix domain RPC server with an open raw socket file descriptor
 // and a given root IBinder object.

libs/binder/libbinder_rpc_unstable.cpp

@@ -81,7 +81,8 @@ RpcSession::FileDescriptorTransportMode toTransportMode(
 extern "C" {
 
 #ifndef __TRUSTY__
-ARpcServer* ARpcServer_newVsock(AIBinder* service, unsigned int cid, unsigned int port) {
+ARpcServer* ARpcServer_newVsock(AIBinder* service, unsigned int cid, unsigned int port,
+                                unsigned int* assignedPort) {
     auto server = RpcServer::make();
 
     unsigned int bindCid = VMADDR_CID_ANY; // bind to the remote interface
@@ -90,7 +91,7 @@ ARpcServer* ARpcServer_newVsock(AIBinder* service, unsigned int cid, unsigned in
         cid = VMADDR_CID_ANY;       // no need for a connection filter
     }
 
-    if (status_t status = server->setupVsockServer(bindCid, port); status != OK) {
+    if (status_t status = server->setupVsockServer(bindCid, port, assignedPort); status != OK) {
         ALOGE("Failed to set up vsock server with port %u error: %s", port,
               statusToString(status).c_str());
         return nullptr;

libs/binder/ndk/binder_rpc.cpp

@@ -104,8 +104,8 @@ struct OnDeleteProviderHolder {
 };
 
 ABinderRpc_AccessorProvider* ABinderRpc_registerAccessorProvider(
-        ABinderRpc_AccessorProvider_getAccessorCallback provider, const char** instances,
-        size_t numInstances, void* data,
+        ABinderRpc_AccessorProvider_getAccessorCallback provider,
+        const char* const* const instances, size_t numInstances, void* data,
         ABinderRpc_AccessorProviderUserData_deleteCallback onDelete) {
     if (provider == nullptr) {
         ALOGE("Null provider passed to ABinderRpc_registerAccessorProvider");

libs/binder/ndk/include_platform/android/binder_rpc.h

@@ -144,8 +144,9 @@ typedef void (*ABinderRpc_AccessorProviderUserData_deleteCallback)(void* _Nullab
  */
 ABinderRpc_AccessorProvider* _Nullable ABinderRpc_registerAccessorProvider(
         ABinderRpc_AccessorProvider_getAccessorCallback _Nonnull provider,
-        const char* _Nullable* _Nonnull instances, size_t numInstances, void* _Nullable data,
-        ABinderRpc_AccessorProviderUserData_deleteCallback _Nullable onDelete) __INTRODUCED_IN(36);
+        const char* _Nullable const* const _Nonnull instances, size_t numInstances,
+        void* _Nullable data, ABinderRpc_AccessorProviderUserData_deleteCallback _Nullable onDelete)
+        __INTRODUCED_IN(36);
 
 /**
  * Remove an ABinderRpc_AccessorProvider from libbinder. This will remove references

libs/binder/rust/rpcbinder/src/server/android.rs

@@ -18,7 +18,7 @@ use crate::session::FileDescriptorTransportMode;
 use binder::{unstable_api::AsNative, SpIBinder};
 use binder_rpc_unstable_bindgen::ARpcServer;
 use foreign_types::{foreign_type, ForeignType, ForeignTypeRef};
-use std::ffi::CString;
+use std::ffi::{c_uint, CString};
 use std::io::{Error, ErrorKind};
 use std::os::unix::io::{IntoRawFd, OwnedFd};
 
@@ -42,18 +42,29 @@ impl RpcServer {
     /// Creates a binder RPC server, serving the supplied binder service implementation on the given
     /// vsock port. Only connections from the given CID are accepted.
     ///
-    // Set `cid` to libc::VMADDR_CID_ANY to accept connections from any client.
-    // Set `cid` to libc::VMADDR_CID_LOCAL to only bind to the local vsock interface.
-    pub fn new_vsock(mut service: SpIBinder, cid: u32, port: u32) -> Result<RpcServer, Error> {
+    /// Set `cid` to [`libc::VMADDR_CID_ANY`] to accept connections from any client.
+    /// Set `cid` to [`libc::VMADDR_CID_LOCAL`] to only bind to the local vsock interface.
+    /// Set `port` to [`libc::VMADDR_PORT_ANY`] to pick an ephemeral port.
+    /// The assigned port is returned with RpcServer.
+    pub fn new_vsock(
+        mut service: SpIBinder,
+        cid: u32,
+        port: u32,
+    ) -> Result<(RpcServer, u32 /* assigned_port */), Error> {
         let service = service.as_native_mut();
 
+        let mut assigned_port: c_uint = 0;
         // SAFETY: Service ownership is transferring to the server and won't be valid afterward.
         // Plus the binder objects are threadsafe.
-        unsafe {
+        let server = unsafe {
             Self::checked_from_ptr(binder_rpc_unstable_bindgen::ARpcServer_newVsock(
-                service, cid, port,
-            ))
-        }
+                service,
+                cid,
+                port,
+                &mut assigned_port,
+            ))?
+        };
+        Ok((server, assigned_port as _))
     }
 
     /// Creates a binder RPC server, serving the supplied binder service implementation on the given