vm-migration: client-side of a TLS connection

TLS connections have a TLS server (listens for incoming connections) and
a TLS client (initiates the connection). This commit adds the code for
the client side, which is the sender of a migration

On-behalf-of: SAP sebastian.eydam@sap.com
Signed-off-by: Sebastian Eydam <sebastian.eydam@cyberus-technology.de>

vm-migration/src/lib.rs

@@ -19,6 +19,7 @@ use crate::protocol::MemoryRangeTable;
 mod bitpos_iterator;
 mod context;
 pub mod protocol;
+pub mod tls;
 
 #[derive(Error, Debug)]
 pub enum UffdError {
@@ -102,6 +103,9 @@ pub enum MigratableError {
 
     #[error("Lifecycle operation skipped for disconnected component {0}")]
     DeviceDisconnected(String),
+
+    #[error("Error setting up a TLS-encrypted connection")]
+    Tls(#[source] tls::TlsError),
 }
 
 /// A Pausable component can be paused and resumed.