vmm: move migration socket helpers into transport module

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

vmm/src/migration_transport.rs

@@ -0,0 +1,83 @@
+// Copyright © 2026 Contributors to the Cloud Hypervisor project
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+
+use std::net::{TcpListener, TcpStream};
+use std::os::unix::net::{UnixListener, UnixStream};
+use std::path::PathBuf;
+use std::result::Result;
+
+use anyhow::anyhow;
+use log::info;
+use vm_migration::MigratableError;
+
+use crate::SocketStream;
+
+/// Extract a UNIX socket path from a "unix:" migration URL.
+fn socket_url_to_path(url: &str) -> Result<PathBuf, anyhow::Error> {
+    url.strip_prefix("unix:")
+        .ok_or_else(|| anyhow!("Could not extract path from URL: {url}"))
+        .map(|s| s.into())
+}
+
+/// Connect to a migration endpoint and return the established stream.
+pub(crate) fn send_migration_socket(
+    destination_url: &str,
+) -> Result<SocketStream, MigratableError> {
+    if let Some(address) = destination_url.strip_prefix("tcp:") {
+        info!("Connecting to TCP socket at {address}");
+
+        let socket = TcpStream::connect(address).map_err(|e| {
+            MigratableError::MigrateSend(anyhow!("Error connecting to TCP socket: {e}"))
+        })?;
+
+        Ok(SocketStream::Tcp(socket))
+    } else {
+        let path = socket_url_to_path(destination_url).map_err(MigratableError::MigrateSend)?;
+        info!("Connecting to UNIX socket at {path:?}");
+
+        let socket = UnixStream::connect(&path).map_err(|e| {
+            MigratableError::MigrateSend(anyhow!("Error connecting to UNIX socket: {e}"))
+        })?;
+
+        Ok(SocketStream::Unix(socket))
+    }
+}
+
+/// Bind and accept a migration connection for the receiver side.
+pub(crate) fn receive_migration_socket(
+    receiver_url: &str,
+) -> Result<SocketStream, MigratableError> {
+    if let Some(address) = receiver_url.strip_prefix("tcp:") {
+        let listener = TcpListener::bind(address).map_err(|e| {
+            MigratableError::MigrateReceive(anyhow!("Error binding to TCP socket: {e}"))
+        })?;
+
+        let (socket, _addr) = listener.accept().map_err(|e| {
+            MigratableError::MigrateReceive(anyhow!(
+                "Error accepting connection on TCP socket: {e}"
+            ))
+        })?;
+
+        Ok(SocketStream::Tcp(socket))
+    } else {
+        let path = socket_url_to_path(receiver_url).map_err(MigratableError::MigrateSend)?;
+        let listener = UnixListener::bind(&path).map_err(|e| {
+            MigratableError::MigrateReceive(anyhow!("Error binding to UNIX socket: {e}"))
+        })?;
+
+        let (socket, _addr) = listener.accept().map_err(|e| {
+            MigratableError::MigrateReceive(anyhow!(
+                "Error accepting connection on UNIX socket: {e}"
+            ))
+        })?;
+
+        // Remove the UNIX socket file after accepting the connection
+        std::fs::remove_file(&path).map_err(|e| {
+            MigratableError::MigrateReceive(anyhow!("Error removing UNIX socket file: {e}"))
+        })?;
+
+        Ok(SocketStream::Unix(socket))
+    }
+}