[libtrusty-rs] Add recv variant that uses Vec<u8>
* Add new `recv` method that takes a `Vec<u8>` and automatically
allocates extra buffer space and retries the read call if the buffer
does not have enough capacity.
* Rename the existing `recv` method to `recv_no_alloc`, and update docs
to clarify the behaviors of both methods.
* Add tests for the new `recv` method and update existing tests to use
`recv_no_alloc` instead.
Test: tipc-test-rs -m 1024 -t echo
Bug: 226659377
Change-Id: Ic437b617751e865da119fe0c4ef8aa456a63bf3c
diff --git a/trusty/libtrusty-rs/Android.bp b/trusty/libtrusty-rs/Android.bp
index 47c64b7..bc1dcf6 100644
--- a/trusty/libtrusty-rs/Android.bp
+++ b/trusty/libtrusty-rs/Android.bp
@@ -24,6 +24,7 @@
],
rustlibs: [
"libnix",
+ "liblibc",
],
}
@@ -33,5 +34,6 @@
srcs: ["tests/test.rs"],
rustlibs: [
"libtrusty-rs",
+ "liblibc",
]
}
diff --git a/trusty/libtrusty-rs/src/lib.rs b/trusty/libtrusty-rs/src/lib.rs
index b3102f8..28ea075 100644
--- a/trusty/libtrusty-rs/src/lib.rs
+++ b/trusty/libtrusty-rs/src/lib.rs
@@ -51,8 +51,8 @@
//!
//! chann.send("Hello, world!".as_bytes()).unwrap();
//!
-//! let mut read_buf = [0u8; 1024];
-//! let read_len = stream.read(&mut read_buf[..]).unwrap();
+//! let mut read_buf = Vec::new();
+//! let read_len = stream.recv(&mut read_buf).unwrap();
//!
//! let response = std::str::from_utf8(&read_buf[..read_len]).unwrap();
//! assert_eq!("Hello, world!", response);
@@ -63,8 +63,8 @@
use crate::sys::tipc_connect;
use std::ffi::CString;
use std::fs::File;
-use std::io;
use std::io::prelude::*;
+use std::io::{ErrorKind, Result};
use std::os::unix::prelude::AsRawFd;
use std::path::Path;
@@ -73,6 +73,12 @@
/// The default filesystem path for the Trusty IPC device.
pub const DEFAULT_DEVICE: &str = "/dev/trusty-ipc-dev0";
+/// The maximum size an incoming TIPC message can be.
+///
+/// This can be used to pre-allocate buffer space in order to ensure that your
+/// read buffer can always hold an incoming message.
+pub const MAX_MESSAGE_SIZE: usize = 4096;
+
/// A channel for communicating with a Trusty service.
///
/// See the [crate-level documentation][crate] for usage details and examples.
@@ -92,7 +98,7 @@
/// bytes. This is handled with a panic because the service names are all
/// hard-coded constants, and so such an error should always be indicative of a
/// bug in the calling code.
- pub fn connect(device: impl AsRef<Path>, service: &str) -> io::Result<Self> {
+ pub fn connect(device: impl AsRef<Path>, service: &str) -> Result<Self> {
let file = File::options().read(true).write(true).open(device)?;
let srv_name = CString::new(service).expect("Service name contained null bytes");
@@ -107,7 +113,7 @@
///
/// The entire contents of `buf` will be sent as a single message to the
/// connected service.
- pub fn send(&mut self, buf: &[u8]) -> io::Result<()> {
+ pub fn send(&mut self, buf: &[u8]) -> Result<()> {
let write_len = self.0.write(buf)?;
// Verify that the expected number of bytes were written. The entire message
@@ -125,19 +131,91 @@
Ok(())
}
- /// Receives a message from the connected service.
+ /// Reads the next incoming message.
///
- /// Returns the number of bytes in the received message, or any error that
- /// occurred when reading the message. Blocks until there is a message to
- /// receive if none is already ready to read.
+ /// Attempts to read the next incoming message from the connected service if any
+ /// exist. If the initial capacity of `buf` is not enough to hold the incoming
+ /// message the function repeatedly attempts to reserve additional space until
+ /// it is able to fully read the message.
+ ///
+ /// Blocks until there is an incoming message if there is not already a message
+ /// ready to be received.
///
/// # Errors
///
- /// Returns an error with native error code 90 (`EMSGSIZE`) if `buf` isn't large
+ /// If this function encounters an error of the kind [`ErrorKind::Interrupted`]
+ /// then the error is ignored and the operation will be tried again.
+ ///
+ /// If this function encounters an error with the error code `EMSGSIZE` then
+ /// additional space will be reserved in `buf` and the operation will be tried
+ /// again.
+ ///
+ /// If any other read error is encountered then this function immediately
+ /// returns the error to the caller, and the length of `buf` is set to 0.
+ pub fn recv(&mut self, buf: &mut Vec<u8>) -> Result<()> {
+ // If no space has been allocated in the buffer reserve enough space to hold any
+ // incoming message.
+ if buf.capacity() == 0 {
+ buf.reserve(MAX_MESSAGE_SIZE);
+ }
+
+ loop {
+ // Resize the vec to make its full capacity available to write into.
+ buf.resize(buf.capacity(), 0);
+
+ match self.0.read(buf.as_mut_slice()) {
+ Ok(len) => {
+ buf.truncate(len);
+ return Ok(());
+ }
+
+ Err(err) => {
+ if let Some(libc::EMSGSIZE) = err.raw_os_error() {
+ // Ensure that we didn't get `EMSGSIZE` when we already had enough capacity
+ // to contain the maximum message size. This should never happen, but if it
+ // does we don't want to hang by looping infinitely.
+ assert!(
+ buf.capacity() < MAX_MESSAGE_SIZE,
+ "Received `EMSGSIZE` error when buffer capacity was already at maximum",
+ );
+
+ // If we didn't have enough space to hold the incoming message, reserve
+ // enough space to fit the maximum message size regardless of how much
+ // capacity the buffer already had.
+ buf.reserve(MAX_MESSAGE_SIZE - buf.capacity());
+ } else if err.kind() == ErrorKind::Interrupted {
+ // If we get an interrupted error the operation can be retried as-is, i.e.
+ // we don't need to allocate additional space.
+ continue;
+ } else {
+ buf.truncate(0);
+ return Err(err);
+ }
+ }
+ }
+ }
+ }
+
+ /// Reads the next incoming message without allocating.
+ ///
+ /// Returns the number of bytes in the received message, or any error that
+ /// occurred when reading the message.
+ ///
+ /// Blocks until there is an incoming message if there is not already a message
+ /// ready to be received.
+ ///
+ /// # Errors
+ ///
+ /// Returns an error with native error code `EMSGSIZE` if `buf` isn't large
/// enough to contain the incoming message. Use
/// [`raw_os_error`][std::io::Error::raw_os_error] to check the error code to
- /// determine if you need to increase the size of `buf`.
- pub fn recv(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+ /// determine if you need to increase the size of `buf`. If error code
+ /// `EMSGSIZE` is returned the incoming message will not be dropped, and a
+ /// subsequent call to `recv_no_alloc` can still read it.
+ ///
+ /// An error of the [`ErrorKind::Interrupted`] kind is non-fatal and the read
+ /// operation should be retried if there is nothing else to do.
+ pub fn recv_no_alloc(&mut self, buf: &mut [u8]) -> Result<usize> {
self.0.read(buf)
}
diff --git a/trusty/libtrusty-rs/tests/test.rs b/trusty/libtrusty-rs/tests/test.rs
index a6f1370..6bff479 100644
--- a/trusty/libtrusty-rs/tests/test.rs
+++ b/trusty/libtrusty-rs/tests/test.rs
@@ -3,7 +3,7 @@
const ECHO_NAME: &str = "com.android.ipc-unittest.srv.echo";
#[test]
-fn echo() {
+fn recv_no_alloc() {
let mut connection = TipcChannel::connect(DEFAULT_DEVICE, ECHO_NAME)
.expect("Failed to connect to Trusty service");
@@ -11,9 +11,10 @@
let send_buf = [7u8; 32];
connection.send(send_buf.as_slice()).unwrap();
- // Receive the response message from the TA.
+ // Receive the response message from the TA. The response message will be the
+ // same as the message we just sent.
let mut recv_buf = [0u8; 32];
- let read_len = connection.recv(&mut recv_buf).expect("Failed to read from connection");
+ let read_len = connection.recv_no_alloc(recv_buf.as_mut_slice()).unwrap();
assert_eq!(
send_buf.len(),
@@ -24,3 +25,62 @@
);
assert_eq!(send_buf, recv_buf, "Received data does not match sent data");
}
+
+#[test]
+fn recv_small_buf() {
+ let mut connection = TipcChannel::connect(DEFAULT_DEVICE, ECHO_NAME)
+ .expect("Failed to connect to Trusty service");
+
+ // Send a long message to the echo service so that we can test receiving a long
+ // message.
+ let send_buf = [7u8; 2048];
+ connection.send(send_buf.as_slice()).unwrap();
+
+ // Attempt to receive the response message with a buffer that is too small to
+ // contain the message.
+ let mut recv_buf = [0u8; 32];
+ let err = connection.recv_no_alloc(recv_buf.as_mut_slice()).unwrap_err();
+
+ assert_eq!(
+ Some(libc::EMSGSIZE),
+ err.raw_os_error(),
+ "Unexpected error err when receiving incoming message: {:?}",
+ err,
+ );
+}
+
+#[test]
+fn recv_empty_vec() {
+ let mut connection = TipcChannel::connect(DEFAULT_DEVICE, ECHO_NAME)
+ .expect("Failed to connect to Trusty service");
+
+ // Send a message to the echo TA.
+ let send_buf = [7u8; 2048];
+ connection.send(send_buf.as_slice()).unwrap();
+
+ // Receive the response message. `recv_buf` is initially empty, and `recv` is
+ // responsible for allocating enough space to hold the message.
+ let mut recv_buf = Vec::new();
+ connection.recv(&mut recv_buf).unwrap();
+
+ assert_eq!(send_buf.as_slice(), recv_buf, "Received data does not match sent data");
+}
+
+#[test]
+fn recv_vec_existing_capacity() {
+ let mut connection = TipcChannel::connect(DEFAULT_DEVICE, ECHO_NAME)
+ .expect("Failed to connect to Trusty service");
+
+ // Send a message to the echo TA.
+ let send_buf = [7u8; 2048];
+ connection.send(send_buf.as_slice()).unwrap();
+
+ // Receive the response message into a buffer that already has enough capacity
+ // to hold the message. No additional capacity should be allocated when
+ // receiving the message.
+ let mut recv_buf = Vec::with_capacity(2048);
+ connection.recv(&mut recv_buf).unwrap();
+
+ assert_eq!(send_buf.as_slice(), recv_buf, "Received data does not match sent data");
+ assert_eq!(2048, recv_buf.capacity(), "Additional capacity was allocated when not needed");
+}