vmm: Add support for cross-host live migration over TCP

Add support for cross-host live migration over TCP, which
significantly improves performance in cross-host live migration
scenarios compared to the Unix socket forwarding method.

Signed-off-by: Jinrong Liang <cloudliang@tencent.com>

vmm/src/lib.rs

@@ -11,6 +11,7 @@ extern crate log;
 use std::collections::HashMap;
 use std::fs::File;
 use std::io::{stdout, Read, Write};
+use std::net::{TcpListener, TcpStream};
 use std::os::unix::io::{AsRawFd, FromRawFd, RawFd};
 use std::os::unix::net::{UnixListener, UnixStream};
 use std::panic::AssertUnwindSafe;
@@ -36,8 +37,8 @@ use serde::{Deserialize, Serialize};
 use signal_hook::iterator::{Handle, Signals};
 use thiserror::Error;
 use tracer::trace_scoped;
-use vm_memory::bitmap::AtomicBitmap;
-use vm_memory::{ReadVolatile, WriteVolatile};
+use vm_memory::bitmap::{AtomicBitmap, BitmapSlice};
+use vm_memory::{ReadVolatile, VolatileMemoryError, VolatileSlice, WriteVolatile};
 use vm_migration::protocol::*;
 use vm_migration::{Migratable, MigratableError, Pausable, Snapshot, Snapshottable, Transportable};
 use vmm_sys_util::eventfd::EventFd;
@@ -235,6 +236,89 @@ impl From<u64> for EpollDispatch {
     }
 }
 
+enum SocketStream {
+    Unix(UnixStream),
+    Tcp(TcpStream),
+}
+
+impl Read for SocketStream {
+    fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
+        match self {
+            SocketStream::Unix(stream) => stream.read(buf),
+            SocketStream::Tcp(stream) => stream.read(buf),
+        }
+    }
+}
+
+impl Write for SocketStream {
+    fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
+        match self {
+            SocketStream::Unix(stream) => stream.write(buf),
+            SocketStream::Tcp(stream) => stream.write(buf),
+        }
+    }
+
+    fn flush(&mut self) -> std::io::Result<()> {
+        match self {
+            SocketStream::Unix(stream) => stream.flush(),
+            SocketStream::Tcp(stream) => stream.flush(),
+        }
+    }
+}
+
+impl AsRawFd for SocketStream {
+    fn as_raw_fd(&self) -> RawFd {
+        match self {
+            SocketStream::Unix(s) => s.as_raw_fd(),
+            SocketStream::Tcp(s) => s.as_raw_fd(),
+        }
+    }
+}
+
+impl ReadVolatile for SocketStream {
+    fn read_volatile<B: BitmapSlice>(
+        &mut self,
+        buf: &mut VolatileSlice<B>,
+    ) -> std::result::Result<usize, VolatileMemoryError> {
+        match self {
+            SocketStream::Unix(s) => s.read_volatile(buf),
+            SocketStream::Tcp(s) => s.read_volatile(buf),
+        }
+    }
+
+    fn read_exact_volatile<B: BitmapSlice>(
+        &mut self,
+        buf: &mut VolatileSlice<B>,
+    ) -> std::result::Result<(), VolatileMemoryError> {
+        match self {
+            SocketStream::Unix(s) => s.read_exact_volatile(buf),
+            SocketStream::Tcp(s) => s.read_exact_volatile(buf),
+        }
+    }
+}
+
+impl WriteVolatile for SocketStream {
+    fn write_volatile<B: BitmapSlice>(
+        &mut self,
+        buf: &VolatileSlice<B>,
+    ) -> std::result::Result<usize, VolatileMemoryError> {
+        match self {
+            SocketStream::Unix(s) => s.write_volatile(buf),
+            SocketStream::Tcp(s) => s.write_volatile(buf),
+        }
+    }
+
+    fn write_all_volatile<B: BitmapSlice>(
+        &mut self,
+        buf: &VolatileSlice<B>,
+    ) -> std::result::Result<(), VolatileMemoryError> {
+        match self {
+            SocketStream::Unix(s) => s.write_all_volatile(buf),
+            SocketStream::Tcp(s) => s.write_all_volatile(buf),
+        }
+    }
+}
+
 pub struct EpollContext {
     epoll_file: File,
 }
@@ -921,14 +1005,72 @@ impl Vmm {
             .map(|s| s.into())
     }
 
+    fn send_migration_socket(
+        destination_url: &str,
+    ) -> std::result::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 = Vmm::socket_url_to_path(destination_url)?;
+            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))
+        }
+    }
+
+    fn receive_migration_socket(
+        receiver_url: &str,
+    ) -> std::result::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 = Vmm::socket_url_to_path(receiver_url)?;
+            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))
+        }
+    }
+
     // Returns true if there were dirty pages to send
-    fn vm_maybe_send_dirty_pages<T>(
+    fn vm_maybe_send_dirty_pages(
         vm: &mut Vm,
-        socket: &mut T,
-    ) -> result::Result<bool, MigratableError>
-    where
-        T: Read + Write + WriteVolatile,
-    {
+        socket: &mut SocketStream,
+    ) -> result::Result<bool, MigratableError> {
         // Send (dirty) memory table
         let table = vm.dirty_log()?;
 
@@ -956,10 +1098,8 @@ impl Vmm {
         >,
         send_data_migration: VmSendMigrationData,
     ) -> result::Result<(), MigratableError> {
-        let path = Self::socket_url_to_path(&send_data_migration.destination_url)?;
-        let mut socket = UnixStream::connect(path).map_err(|e| {
-            MigratableError::MigrateSend(anyhow!("Error connecting to UNIX socket: {}", e))
-        })?;
+        // Set up the socket connection
+        let mut socket = Self::send_migration_socket(&send_data_migration.destination_url)?;
 
         // Start the migration
         Request::start().write_to(&mut socket)?;
@@ -999,7 +1139,17 @@ impl Vmm {
         };
 
         if send_data_migration.local {
-            vm.send_memory_fds(&mut socket)?;
+            match &mut socket {
+                SocketStream::Unix(unix_socket) => {
+                    // Proceed with sending memory file descriptors over UNIX socket
+                    vm.send_memory_fds(unix_socket)?;
+                }
+                SocketStream::Tcp(_tcp_socket) => {
+                    return Err(MigratableError::MigrateSend(anyhow!(
+                        "--local option is not supported with TCP sockets",
+                    )));
+                }
+            }
         }
 
         let vm_migration_config = VmMigrationConfig {
@@ -1960,16 +2110,8 @@ impl RequestHandler for Vmm {
             receive_data_migration.receiver_url
         );
 
-        let path = Self::socket_url_to_path(&receive_data_migration.receiver_url)?;
-        let listener = UnixListener::bind(&path).map_err(|e| {
-            MigratableError::MigrateReceive(anyhow!("Error binding to UNIX socket: {}", e))
-        })?;
-        let (mut socket, _addr) = listener.accept().map_err(|e| {
-            MigratableError::MigrateReceive(anyhow!("Error accepting on UNIX socket: {}", e))
-        })?;
-        std::fs::remove_file(&path).map_err(|e| {
-            MigratableError::MigrateReceive(anyhow!("Error unlinking UNIX socket: {}", e))
-        })?;
+        // Accept the connection and get the socket
+        let mut socket = Vmm::receive_migration_socket(&receive_data_migration.receiver_url)?;
 
         let mut started = false;
         let mut memory_manager: Option<Arc<Mutex<MemoryManager>>> = None;
@@ -2037,24 +2179,35 @@ impl RequestHandler for Vmm {
                         continue;
                     }
 
-                    let mut buf = [0u8; 4];
-                    let (_, file) = socket.recv_with_fd(&mut buf).map_err(|e| {
-                        MigratableError::MigrateReceive(anyhow!(
-                            "Error receiving slot from socket: {}",
-                            e
-                        ))
-                    })?;
+                    match &mut socket {
+                        SocketStream::Unix(unix_socket) => {
+                            let mut buf = [0u8; 4];
+                            let (_, file) = unix_socket.recv_with_fd(&mut buf).map_err(|e| {
+                                MigratableError::MigrateReceive(anyhow!(
+                                    "Error receiving slot from socket: {}",
+                                    e
+                                ))
+                            })?;
 
-                    if existing_memory_files.is_none() {
-                        existing_memory_files = Some(HashMap::default())
+                            if existing_memory_files.is_none() {
+                                existing_memory_files = Some(HashMap::default())
+                            }
+
+                            if let Some(ref mut existing_memory_files) = existing_memory_files {
+                                let slot = u32::from_le_bytes(buf);
+                                existing_memory_files.insert(slot, file.unwrap());
+                            }
+
+                            Response::ok().write_to(&mut socket)?;
+                        }
+                        SocketStream::Tcp(_tcp_socket) => {
+                            // For TCP sockets, we cannot transfer file descriptors
+                            warn!(
+                                "MemoryFd command received over TCP socket, which is not supported"
+                            );
+                            Response::error().write_to(&mut socket)?;
+                        }
                     }
-
-                    if let Some(ref mut existing_memory_files) = existing_memory_files {
-                        let slot = u32::from_le_bytes(buf);
-                        existing_memory_files.insert(slot, file.unwrap());
-                    }
-
-                    Response::ok().write_to(&mut socket)?;
                 }
                 Command::Complete => {
                     info!("Complete Command Received");