crosvm: use seqpacket rather than datagram sockets

The advantage of seqpacket is that they are connection oriented. A
listener can be created that accepts new connections, useful for the
path based VM control sockets. Previously, the only bidirectional
sockets in crosvm were either stream based or made using socketpair.

This change also whitelists sendmsg and recvmsg for the common device
policy.

TEST=cargo test
BUG=chromium:848187

Change-Id: I83fd46f54bce105a7730632cd013b5e7047db22b
Reviewed-on: https://chromium-review.googlesource.com/1470917
Commit-Ready: Zach Reizner <zachr@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
Tested-by: Zach Reizner <zachr@chromium.org>
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>

1 files changed, 7 insertions, 3 deletions

diff --git a/msg_socket/src/msg_on_socket.rs b/msg_socket/src/msg_on_socket.rs
index 493c57c..8b01850 100644
--- a/msg_socket/src/msg_on_socket.rs
+++ b/msg_socket/src/msg_on_socket.rs
@@ -23,8 +23,8 @@ pub enum MsgError {
     /// The type of a received request or response is unknown.
     InvalidType,
     /// There was not the expected amount of data when receiving a message. The inner
-    /// value is how much data is needed.
-    BadRecvSize(usize),
+    /// value is how much data is expected and how much data was actually received.
+    BadRecvSize { expected: usize, actual: usize },
     /// There was no associated file descriptor received for a request that expected it.
     ExpectFd,
     /// There was some associated file descriptor received but not used when deserialize.
@@ -47,7 +47,11 @@ impl Display for MsgError {
             Send(e) => write!(f, "failed to send request or response: {}", e),
             Recv(e) => write!(f, "failed to receive request or response: {}", e),
             InvalidType => write!(f, "invalid type"),
-            BadRecvSize(n) => write!(f, "wrong amount of data received; expected {} bytes", n),
+            BadRecvSize { expected, actual } => write!(
+                f,
+                "wrong amount of data received; expected {} bytes; got {} bytes",
+                expected, actual
+            ),
             ExpectFd => write!(f, "missing associated file descriptor for request"),
             NotExpectFd => write!(f, "unexpected file descriptor is unused"),
             WrongFdBufferSize => write!(f, "fd buffer size too small"),