Add vsock support for MacOS VM

conn_darwin.go

@@ -0,0 +1,62 @@
+//go:build darwin
+// +build darwin
+
+package vsock
+
+import (
+	"context"
+
+	"github.com/mdlayher/socket"
+	"golang.org/x/sys/unix"
+)
+
+// A conn is the net.Conn implementation for connection-oriented VM sockets.
+// We can use socket.Conn directly on Linux to implement all of the necessary
+// methods.
+type conn = socket.Conn
+
+// dial is the entry point for Dial on Linux.
+func dial(ctx context.Context, cid, port uint32, _ *Config) (*Conn, error) {
+	// TODO(mdlayher): Config default nil check and initialize. Pass options to
+	// socket.Config where necessary.
+
+	c, err := socket.Socket(unix.AF_VSOCK, unix.SOCK_STREAM, 0, "vsock", nil)
+	if err != nil {
+		return nil, err
+	}
+
+	sa := &unix.SockaddrVM{CID: cid, Port: port}
+	rsa, err := c.Connect(ctx, sa)
+	if err != nil {
+		_ = c.Close()
+		return nil, err
+	}
+
+	// TODO(mdlayher): getpeername(2) appears to return nil in the GitHub CI
+	// environment, so in the event of a nil sockaddr, fall back to the previous
+	// method of synthesizing the remote address.
+	if rsa == nil {
+		rsa = sa
+	}
+
+	lsa, err := c.Getsockname()
+	if err != nil {
+		_ = c.Close()
+		return nil, err
+	}
+
+	lsavm := lsa.(*unix.SockaddrVM)
+	rsavm := rsa.(*unix.SockaddrVM)
+
+	return &Conn{
+		c: c,
+		local: &Addr{
+			ContextID: lsavm.CID,
+			Port:      lsavm.Port,
+		},
+		remote: &Addr{
+			ContextID: rsavm.CID,
+			Port:      rsavm.Port,
+		},
+	}, nil
+}

conn_linux.go

@@ -16,7 +16,7 @@ import (
 type conn = socket.Conn
 
 // dial is the entry point for Dial on Linux.
-func dial(cid, port uint32, _ *Config) (*Conn, error) {
+func dial(ctx context.Context, cid, port uint32, _ *Config) (*Conn, error) {
 	// TODO(mdlayher): Config default nil check and initialize. Pass options to
 	// socket.Config where necessary.
 
@@ -26,7 +26,7 @@ func dial(cid, port uint32, _ *Config) (*Conn, error) {
 	}
 
 	sa := &unix.SockaddrVM{CID: cid, Port: port}
-	rsa, err := c.Connect(context.Background(), sa)
+	rsa, err := c.Connect(ctx, sa)
 	if err != nil {
 		_ = c.Close()
 		return nil, err

fd_darwin.go

@@ -0,0 +1,37 @@
+package vsock
+
+import (
+	"fmt"
+
+	"golang.org/x/sys/unix"
+)
+
+// contextID retrieves the local context ID for this system.
+func contextID() (uint32, error) {
+	if fd, err := unix.Socket(unix.AF_VSOCK, unix.SOCK_STREAM, 0); err != nil {
+		return 2, nil
+	} else {
+		defer unix.Close(fd)
+
+		cid, err := unix.IoctlGetInt(fd, unix.IOCTL_VM_SOCKETS_GET_LOCAL_CID)
+
+		return uint32(cid), err
+	}
+}
+
+// isErrno determines if an error a matches UNIX error number.
+func isErrno(err error, errno int) bool {
+	switch errno {
+	case ebadf:
+		return err == unix.EBADF
+	case enotconn:
+		return err == unix.ENOTCONN
+	default:
+		panicf("vsock: isErrno called with unhandled error number parameter: %d", errno)
+		return false
+	}
+}
+
+func panicf(format string, a ...interface{}) {
+	panic(fmt.Sprintf(format, a...))
+}

go.mod

@@ -3,9 +3,9 @@ module github.com/mdlayher/vsock
 go 1.20
 
 require (
-	github.com/google/go-cmp v0.5.9
-	github.com/mdlayher/socket v0.4.1
-	golang.org/x/net v0.9.0
-	golang.org/x/sync v0.1.0
-	golang.org/x/sys v0.7.0
+	github.com/google/go-cmp v0.6.0
+	github.com/mdlayher/socket v0.5.1
+	golang.org/x/net v0.33.0
+	golang.org/x/sync v0.10.0
+	golang.org/x/sys v0.28.0
 )

go.sum

@@ -1,16 +1,10 @@
-github.com/google/go-cmp v0.5.9 h1:O2Tfq5qg4qc4AmwVlvv0oLiVAGB7enBSJ2x2DqQFi38=
-github.com/google/go-cmp v0.5.9/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
-github.com/mdlayher/socket v0.4.0 h1:280wsy40IC9M9q1uPGcLBwXpcTQDtoGwVt+BNoITxIw=
-github.com/mdlayher/socket v0.4.0/go.mod h1:xxFqz5GRCUN3UEOm9CZqEJsAbe1C8OwSK46NlmWuVoc=
-github.com/mdlayher/socket v0.4.1 h1:eM9y2/jlbs1M615oshPQOHZzj6R6wMT7bX5NPiQvn2U=
-github.com/mdlayher/socket v0.4.1/go.mod h1:cAqeGjoufqdxWkD7DkpyS+wcefOtmu5OQ8KuoJGIReA=
-golang.org/x/net v0.2.0 h1:sZfSu1wtKLGlWI4ZZayP0ck9Y73K1ynO6gqzTdBVdPU=
-golang.org/x/net v0.2.0/go.mod h1:KqCZLdyyvdV855qA2rE3GC2aiw5xGR5TEjj8smXukLY=
-golang.org/x/net v0.9.0 h1:aWJ/m6xSmxWBx+V0XRHTlrYrPG56jKsLdTFmsSsCzOM=
-golang.org/x/net v0.9.0/go.mod h1:d48xBJpPfHeWQsugry2m+kC02ZBRGRgulfHnEXEuWns=
-golang.org/x/sync v0.1.0 h1:wsuoTGHzEhffawBOhz5CYhcrV4IdKZbEyZjBMuTp12o=
-golang.org/x/sync v0.1.0/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sys v0.2.0 h1:ljd4t30dBnAvMZaQCevtY0xLLD0A+bRZXbgLMLU1F/A=
-golang.org/x/sys v0.2.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.7.0 h1:3jlCCIQZPdOYu1h8BkNvLz8Kgwtae2cagcG/VamtZRU=
-golang.org/x/sys v0.7.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
+github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
+github.com/mdlayher/socket v0.5.1 h1:VZaqt6RkGkt2OE9l3GcC6nZkqD3xKeQLyfleW/uBcos=
+github.com/mdlayher/socket v0.5.1/go.mod h1:TjPLHI1UgwEv5J1B5q0zTZq12A/6H7nKmtTanQE37IQ=
+golang.org/x/net v0.33.0 h1:74SYHlV8BIgHIFC/LrYkOGIwL19eTYXQ5wc6TBuO36I=
+golang.org/x/net v0.33.0/go.mod h1:HXLR5J+9DxmrqMwG9qjGCxZ+zKXxBru04zlTvWlWuN4=
+golang.org/x/sync v0.10.0 h1:3NQrjDixjgGwUOCaF8w2+VYHv0Ve/vGYSbdkTa98gmQ=
+golang.org/x/sync v0.10.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
+golang.org/x/sys v0.28.0 h1:Fksou7UEQUWlKvIdsqzJmUmCX3cZuD2+P3XyyzwMhlA=
+golang.org/x/sys v0.28.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=

listener_darwin.go

@@ -0,0 +1,133 @@
+//go:build darwin
+// +build darwin
+
+package vsock
+
+import (
+	"context"
+	"net"
+	"os"
+	"time"
+
+	"github.com/mdlayher/socket"
+	"golang.org/x/sys/unix"
+)
+
+var _ net.Listener = &listener{}
+
+// A listener is the net.Listener implementation for connection-oriented
+// VM sockets.
+type listener struct {
+	c    *socket.Conn
+	addr *Addr
+}
+
+// Addr and Close implement the net.Listener interface for listener.
+func (l *listener) Addr() net.Addr                { return l.addr }
+func (l *listener) Close() error                  { return l.c.Close() }
+func (l *listener) SetDeadline(t time.Time) error { return l.c.SetDeadline(t) }
+
+// Accept accepts a single connection from the listener, and sets up
+// a net.Conn backed by conn.
+func (l *listener) Accept() (net.Conn, error) {
+	c, rsa, err := l.c.Accept(context.Background(), 0)
+	if err != nil {
+		return nil, err
+	}
+
+	savm := rsa.(*unix.SockaddrVM)
+	remote := &Addr{
+		ContextID: savm.CID,
+		Port:      savm.Port,
+	}
+
+	return &Conn{
+		c:      c,
+		local:  l.addr,
+		remote: remote,
+	}, nil
+}
+
+// name is the socket name passed to package socket.
+const name = "vsock"
+
+// listen is the entry point for Listen on Linux.
+func listen(cid, port uint32, _ *Config) (*Listener, error) {
+	// TODO(mdlayher): Config default nil check and initialize. Pass options to
+	// socket.Config where necessary.
+
+	c, err := socket.Socket(unix.AF_VSOCK, unix.SOCK_STREAM, 0, name, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	// Be sure to close the Conn if any of the system calls fail before we
+	// return the Conn to the caller.
+
+	if port == 0 {
+		port = unix.VMADDR_PORT_ANY
+	}
+
+	if err := c.Bind(&unix.SockaddrVM{CID: cid, Port: port}); err != nil {
+		_ = c.Close()
+		return nil, err
+	}
+
+	if err := c.Listen(unix.SOMAXCONN); err != nil {
+		_ = c.Close()
+		return nil, err
+	}
+
+	l, err := newListener(c)
+	if err != nil {
+		_ = c.Close()
+		return nil, err
+	}
+
+	return l, nil
+}
+
+// fileListener is the entry point for FileListener on Linux.
+func fileListener(f *os.File) (*Listener, error) {
+	c, err := socket.FileConn(f, name)
+	if err != nil {
+		return nil, err
+	}
+
+	l, err := newListener(c)
+	if err != nil {
+		_ = c.Close()
+		return nil, err
+	}
+
+	return l, nil
+}
+
+// newListener creates a Listener from a raw socket.Conn.
+func newListener(c *socket.Conn) (*Listener, error) {
+	lsa, err := c.Getsockname()
+	if err != nil {
+		return nil, err
+	}
+
+	// Now that the library can also accept arbitrary os.Files, we have to
+	// verify the address family so we don't accidentally create a
+	// *vsock.Listener backed by TCP or some other socket type.
+	lsavm, ok := lsa.(*unix.SockaddrVM)
+	if !ok {
+		// All errors should wrapped with os.SyscallError.
+		return nil, os.NewSyscallError("listen", unix.EINVAL)
+	}
+
+	addr := &Addr{
+		ContextID: lsavm.CID,
+		Port:      lsavm.Port,
+	}
+
+	return &Listener{
+		l: &listener{
+			c:    c,
+			addr: addr,
+		},
+	}, nil
+}

vsock.go

@@ -1,11 +1,12 @@
 package vsock
 
 import (
-	"errors"
+	"context"
 	"fmt"
 	"io"
 	"net"
 	"os"
+	"runtime"
 	"strings"
 	"syscall"
 	"time"
@@ -54,6 +55,10 @@ const (
 	opWrite       = "write"
 )
 
+// errUnimplemented is returned by all functions on platforms that
+// cannot make use of VM sockets.
+var errUnimplemented = fmt.Errorf("vsock: not implemented on %s", runtime.GOOS)
+
 // TODO(mdlayher): plumb through socket.Config.NetNS if it makes sense.
 
 // Config contains options for a Conn or Listener.
@@ -176,7 +181,21 @@ func (l *Listener) opError(op string, err error) error {
 // When the connection is no longer needed, Close must be called to free
 // resources.
 func Dial(contextID, port uint32, cfg *Config) (*Conn, error) {
-	c, err := dial(contextID, port, cfg)
+	return dial(context.Background(), contextID, port, cfg)
+}
+
+// DialWithContext connects to the address on the named network using
+// the provided context.
+//
+// The provided Context must be non-nil. If the context expires before
+// the connection is complete, an error is returned. Once successfully
+// connected, any expiration of the context will not affect the
+// connection.
+//
+// See func Dial for a description of the contextID and port
+// parameters.
+func DialWithContext(ctx context.Context, contextID, port uint32, cfg *Config) (*Conn, error) {
+	c, err := dial(ctx, contextID, port, cfg)
 	if err != nil {
 		// No local address, but we have a remote address we can return.
 		return nil, opError(opDial, err, nil, &Addr{
@@ -403,7 +422,7 @@ func opError(op string, err error, local, remote net.Addr) error {
 		//
 		// To rectify the differences, net.TCPConn uses an error with this text
 		// from internal/poll for the backing file already being closed.
-		err = errors.New("use of closed network connection")
+		err = net.ErrClosed
 	default:
 		// Nothing to do, return this directly.
 	}