Added HV Socket known IDs, Dial, bug fixes (#239)

* Added HV Socket known IDs, Dial, bug fixes

Added:
* Well-know Hyper-V VMIDs for parents, children, and loopback.
* VSock interop service GUID.
* `Dial()` and `DialContext()` to dial a specific Hyper-V socket at a
  known address (along with a corresponding `HvsockDialer` struct.

Bug fixes:
* Dial (and Listen) now properly initialize and set properties of their
  sockets after ConnectEx (and AcceptEx).
* The `socketError` used by `bind` was incorrect, it should be `int32(-1)`,
  not `uintptr(^0)`
* Return errors for `(*HvsockConn) SetDeadline`

Created a `sockets` package, currently only with syscalls to `Bind`,
`ConnectEx` and `GetSockName`, bypassing `syscall/windows` restrictions
on the types that can do so.

Signed-off-by: Hamza El-Saawy <hamzaelsaawy@microsoft.com>

* PR: error handling bug, rebase, unexport, naming

* comments and todos statements
* spelling
* removed dead code
* changed names to be more conventional
* unexported socket code
* made `(*HvsockDialer) Dial` take `Context`, removed `DialContext`
* added default `Dial` function
* rebased onto main
* cleaned up `Dial(` retry loop

Signed-off-by: Hamza El-Saawy <hamzaelsaawy@microsoft.com>

* PR: RawSockaddr validation, `.As(` style

Signed-off-by: Hamza El-Saawy <hamzaelsaawy@microsoft.com>

file.go

@@ -178,6 +178,8 @@ func ioCompletionProcessor(h syscall.Handle) {
 	}
 }
 
+// todo: helsaawy - create an asyncIO version that takes a context
+
 // asyncIo processes the return value from ReadFile or WriteFile, blocking until
 // the operation has actually completed.
 func (f *win32File) asyncIo(c *ioOperation, d *deadlineHandler, bytes uint32, err error) (int, error) {
@@ -221,6 +223,7 @@ func (f *win32File) asyncIo(c *ioOperation, d *deadlineHandler, bytes uint32, er
 	// runtime.KeepAlive is needed, as c is passed via native
 	// code to ioCompletionProcessor, c must remain alive
 	// until the channel read is complete.
+	// todo: (de)allocate *ioOperation via win32 heap functions, instead of needing to KeepAlive?
 	runtime.KeepAlive(c)
 	return int(r.bytes), err
 }

hvsock.go

@@ -4,6 +4,8 @@
 package winio
 
 import (
+	"context"
+	"errors"
 	"fmt"
 	"io"
 	"net"
@@ -12,16 +14,87 @@ import (
 	"time"
 	"unsafe"
 
+	"golang.org/x/sys/windows"
+
+	"github.com/Microsoft/go-winio/internal/socket"
 	"github.com/Microsoft/go-winio/pkg/guid"
 )
 
-//sys bind(s syscall.Handle, name unsafe.Pointer, namelen int32) (err error) [failretval==socketError] = ws2_32.bind
+const afHvSock = 34 // AF_HYPERV
 
-const (
-	afHvSock = 34 // AF_HYPERV
+// Well known Service and VM IDs
+//https://docs.microsoft.com/en-us/virtualization/hyper-v-on-windows/user-guide/make-integration-service#vmid-wildcards
 
-	socketError = ^uintptr(0)
-)
+// HvsockGUIDWildcard is the wildcard VmId for accepting connections from all partitions.
+func HvsockGUIDWildcard() guid.GUID { // 00000000-0000-0000-0000-000000000000
+	return guid.GUID{}
+}
+
+// HvsockGUIDBroadcast is the wildcard VmId for broadcasting sends to all partitions
+func HvsockGUIDBroadcast() guid.GUID { //ffffffff-ffff-ffff-ffff-ffffffffffff
+	return guid.GUID{
+		Data1: 0xffffffff,
+		Data2: 0xffff,
+		Data3: 0xffff,
+		Data4: [8]uint8{0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff},
+	}
+}
+
+// HvsockGUIDLoopback is the Loopback VmId for accepting connections to the same partition as the connector.
+func HvsockGUIDLoopback() guid.GUID { // e0e16197-dd56-4a10-9195-5ee7a155a838
+	return guid.GUID{
+		Data1: 0xe0e16197,
+		Data2: 0xdd56,
+		Data3: 0x4a10,
+		Data4: [8]uint8{0x91, 0x95, 0x5e, 0xe7, 0xa1, 0x55, 0xa8, 0x38},
+	}
+}
+
+// HvsockGUIDSiloHost is the address of a silo's host partition:
+// - The silo host of a hosted silo is the utility VM.
+// - The silo host of a silo on a physical host is the physical host.
+func HvsockGUIDSiloHost() guid.GUID { // 36bd0c5c-7276-4223-88ba-7d03b654c568
+	return guid.GUID{
+		Data1: 0x36bd0c5c,
+		Data2: 0x7276,
+		Data3: 0x4223,
+		Data4: [8]byte{0x88, 0xba, 0x7d, 0x03, 0xb6, 0x54, 0xc5, 0x68},
+	}
+}
+
+// HvsockGUIDChildren is the wildcard VmId for accepting connections from the connector's child partitions.
+func HvsockGUIDChildren() guid.GUID { // 90db8b89-0d35-4f79-8ce9-49ea0ac8b7cd
+	return guid.GUID{
+		Data1: 0x90db8b89,
+		Data2: 0xd35,
+		Data3: 0x4f79,
+		Data4: [8]uint8{0x8c, 0xe9, 0x49, 0xea, 0xa, 0xc8, 0xb7, 0xcd},
+	}
+}
+
+// HvsockGUIDParent is the wildcard VmId for accepting connections from the connector's parent partition.
+// Listening on this VmId accepts connection from:
+// - Inside silos: silo host partition.
+// - Inside hosted silo: host of the VM.
+// - Inside VM: VM host.
+// - Physical host: Not supported.
+func HvsockGUIDParent() guid.GUID { // a42e7cda-d03f-480c-9cc2-a4de20abb878
+	return guid.GUID{
+		Data1: 0xa42e7cda,
+		Data2: 0xd03f,
+		Data3: 0x480c,
+		Data4: [8]uint8{0x9c, 0xc2, 0xa4, 0xde, 0x20, 0xab, 0xb8, 0x78},
+	}
+}
+
+// hvsockVsockServiceTemplate is the Service GUID used for the VSOCK protocol
+func hvsockVsockServiceTemplate() guid.GUID { // 00000000-facb-11e6-bd58-64006a7986d3
+	return guid.GUID{
+		Data2: 0xfacb,
+		Data3: 0x11e6,
+		Data4: [8]uint8{0xbd, 0x58, 0x64, 0x00, 0x6a, 0x79, 0x86, 0xd3},
+	}
+}
 
 // An HvsockAddr is an address for a AF_HYPERV socket.
 type HvsockAddr struct {
@@ -36,6 +109,8 @@ type rawHvsockAddr struct {
 	ServiceID guid.GUID
 }
 
+var _ socket.RawSockaddr = &rawHvsockAddr{}
+
 // Network returns the address's network name, "hvsock".
 func (addr *HvsockAddr) Network() string {
 	return "hvsock"
@@ -47,7 +122,7 @@ func (addr *HvsockAddr) String() string {
 
 // VsockServiceID returns an hvsock service ID corresponding to the specified AF_VSOCK port.
 func VsockServiceID(port uint32) guid.GUID {
-	g, _ := guid.FromString("00000000-facb-11e6-bd58-64006a7986d3")
+	g := hvsockVsockServiceTemplate() // make a copy
 	g.Data1 = port
 	return g
 }
@@ -65,18 +140,46 @@ func (addr *HvsockAddr) fromRaw(raw *rawHvsockAddr) {
 	addr.ServiceID = raw.ServiceID
 }
 
+// Sockaddr returns a pointer to and the size of this struct.
+//
+// Implements the [socket.RawSockaddr] interface, and allows use in
+// [socket.Bind()] and [socket.ConnectEx()]
+func (r *rawHvsockAddr) Sockaddr() (unsafe.Pointer, int32, error) {
+	return unsafe.Pointer(r), int32(unsafe.Sizeof(rawHvsockAddr{})), nil
+}
+
+// Sockaddr interface allows use with `sockets.Bind()` and `.ConnectEx()`
+func (r *rawHvsockAddr) FromBytes(b []byte) error {
+	n := int(unsafe.Sizeof(rawHvsockAddr{}))
+
+	if len(b) < n {
+		return fmt.Errorf("got %d, want %d: %w", len(b), n, socket.ErrBufferSize)
+	}
+
+	copy(unsafe.Slice((*byte)(unsafe.Pointer(r)), n), b[:n])
+	if r.Family != afHvSock {
+		return fmt.Errorf("got %d, want %d: %w", r.Family, afHvSock, socket.ErrAddrFamily)
+	}
+
+	return nil
+}
+
 // HvsockListener is a socket listener for the AF_HYPERV address family.
 type HvsockListener struct {
 	sock *win32File
 	addr HvsockAddr
 }
 
+var _ net.Listener = &HvsockListener{}
+
 // HvsockConn is a connected socket of the AF_HYPERV address family.
 type HvsockConn struct {
 	sock          *win32File
 	local, remote HvsockAddr
 }
 
+var _ net.Conn = &HvsockConn{}
+
 func newHvSocket() (*win32File, error) {
 	fd, err := syscall.Socket(afHvSock, syscall.SOCK_STREAM, 1)
 	if err != nil {
@@ -99,7 +202,7 @@ func ListenHvsock(addr *HvsockAddr) (_ *HvsockListener, err error) {
 		return nil, l.opErr("listen", err)
 	}
 	sa := addr.raw()
-	err = bind(sock.handle, unsafe.Pointer(&sa), int32(unsafe.Sizeof(sa)))
+	err = socket.Bind(windows.Handle(sock.handle), &sa)
 	if err != nil {
 		return nil, l.opErr("listen", os.NewSyscallError("socket", err))
 	}
@@ -136,21 +239,35 @@ func (l *HvsockListener) Accept() (_ net.Conn, err error) {
 	}
 	defer l.sock.wg.Done()
 
-	// AcceptEx, per documentation, requires an extra 16 bytes per address.
+	// AcceptEx, per documentation, requires an extra 16 bytes per address:
+	// https://docs.microsoft.com/en-us/windows/win32/api/mswsock/nf-mswsock-acceptex
 	const addrlen = uint32(16 + unsafe.Sizeof(rawHvsockAddr{}))
 	var addrbuf [addrlen * 2]byte
 
 	var bytes uint32
-	err = syscall.AcceptEx(l.sock.handle, sock.handle, &addrbuf[0], 0, addrlen, addrlen, &bytes, &c.o)
-	_, err = l.sock.asyncIo(c, nil, bytes, err)
-	if err != nil {
+	err = syscall.AcceptEx(l.sock.handle, sock.handle, &addrbuf[0], 0 /*rxdatalen*/, addrlen, addrlen, &bytes, &c.o)
+	if _, err = l.sock.asyncIo(c, nil, bytes, err); err != nil {
 		return nil, l.opErr("accept", os.NewSyscallError("acceptex", err))
 	}
+
 	conn := &HvsockConn{
 		sock: sock,
 	}
+	// The local address returned in the AcceptEx buffer is the same as the Listener socket's
+	// address. However, the service GUID reported by GetSockName is different from the Listeners
+	// socket, and is sometimes the same as the local address of the socket that dialed the
+	// address, with the service GUID.Data1 incremented, but othertimes is different.
+	// todo: does the local address matter? is the listener's address or the actual address appropriate?
 	conn.local.fromRaw((*rawHvsockAddr)(unsafe.Pointer(&addrbuf[0])))
 	conn.remote.fromRaw((*rawHvsockAddr)(unsafe.Pointer(&addrbuf[addrlen])))
+
+	// initialize the accepted socket and update its properties with those of the listening socket
+	if err = windows.Setsockopt(windows.Handle(sock.handle),
+		windows.SOL_SOCKET, windows.SO_UPDATE_ACCEPT_CONTEXT,
+		(*byte)(unsafe.Pointer(&l.sock.handle)), int32(unsafe.Sizeof(l.sock.handle))); err != nil {
+		return nil, conn.opErr("accept", os.NewSyscallError("setsockopt", err))
+	}
+
 	sock = nil
 	return conn, nil
 }
@@ -160,38 +277,165 @@ func (l *HvsockListener) Close() error {
 	return l.sock.Close()
 }
 
-/* Need to finish ConnectEx handling
-func DialHvsock(ctx context.Context, addr *HvsockAddr) (*HvsockConn, error) {
+// HvsockDialer configures and dials a Hyper-V Socket (ie, [HvsockConn]).
+type HvsockDialer struct {
+	// Deadline is the time the Dial operation must connect before erroring.
+	Deadline time.Time
+
+	// Retries is the number of additional connects to try if the connection times out, is refused,
+	// or the host is unreachable
+	Retries uint
+
+	// RetryWait is the time to wait after a connection error to retry
+	RetryWait time.Duration
+
+	rt *time.Timer // redial wait timer
+}
+
+// Dial the Hyper-V socket at addr.
+//
+// See (*HvsockDialer).Dial for more information.
+func Dial(ctx context.Context, addr *HvsockAddr) (conn *HvsockConn, err error) {
+	return (&HvsockDialer{}).Dial(ctx, addr)
+}
+
+// Dial attempts to connect to the Hyper-V socket at addr, and returns a connection if successful.
+// Will attempt (HvsockDialer).Retries if dialing fails, waiting (HvsockDialer).RetryWait between
+// retries.
+// Dialing can be cancelled either by providing (HvsockDialer).Deadline, or cancelling ctx.
+func (d *HvsockDialer) Dial(ctx context.Context, addr *HvsockAddr) (conn *HvsockConn, err error) {
+	op := "dial"
+	// create the conn early to use opErr()
+	conn = &HvsockConn{
+		remote: *addr,
+	}
+
+	if !d.Deadline.IsZero() {
+		var cancel context.CancelFunc
+		ctx, cancel = context.WithDeadline(ctx, d.Deadline)
+		defer cancel()
+	}
+
+	// preemptive timeout/cancellation check
+	if err = ctx.Err(); err != nil {
+		return nil, conn.opErr(op, err)
+	}
+
 	sock, err := newHvSocket()
 	if err != nil {
-		return nil, err
+		return nil, conn.opErr(op, err)
 	}
 	defer func() {
 		if sock != nil {
 			sock.Close()
 		}
 	}()
+
+	sa := addr.raw()
+	err = socket.Bind(windows.Handle(sock.handle), &sa)
+	if err != nil {
+		return nil, conn.opErr(op, os.NewSyscallError("bind", err))
+	}
+
 	c, err := sock.prepareIo()
 	if err != nil {
-		return nil, err
+		return nil, conn.opErr(op, err)
 	}
 	defer sock.wg.Done()
 	var bytes uint32
-	err = windows.ConnectEx(windows.Handle(sock.handle), sa, nil, 0, &bytes, &c.o)
-	_, err = sock.asyncIo(ctx, c, nil, bytes, err)
+	for i := uint(0); i <= d.Retries; i++ {
+		err = socket.ConnectEx(
+			windows.Handle(sock.handle),
+			&sa,
+			nil, // sendBuf
+			0,   // sendDataLen
+			&bytes,
+			(*windows.Overlapped)(unsafe.Pointer(&c.o)))
+		_, err = sock.asyncIo(c, nil, bytes, err)
+		if i < d.Retries && canRedial(err) {
+			if err = d.redialWait(ctx); err == nil {
+				continue
+			}
+		}
+		break
+	}
 	if err != nil {
-		return nil, err
+		return nil, conn.opErr(op, os.NewSyscallError("connectex", err))
 	}
-	conn := &HvsockConn{
-		sock:   sock,
-		remote: *addr,
+
+	// update the connection properties, so shutdown can be used
+	if err = windows.Setsockopt(
+		windows.Handle(sock.handle),
+		windows.SOL_SOCKET,
+		windows.SO_UPDATE_CONNECT_CONTEXT,
+		nil, // optvalue
+		0,   // optlen
+	); err != nil {
+		return nil, conn.opErr(op, os.NewSyscallError("setsockopt", err))
 	}
+
+	// get the local name
+	var sal rawHvsockAddr
+	err = socket.GetSockName(windows.Handle(sock.handle), &sal)
+	if err != nil {
+		return nil, conn.opErr(op, os.NewSyscallError("getsockname", err))
+	}
+	conn.local.fromRaw(&sal)
+
+	// one last check for timeout, since asyncIO doesnt check the context
+	if err = ctx.Err(); err != nil {
+		return nil, conn.opErr(op, err)
+	}
+
+	conn.sock = sock
 	sock = nil
+
 	return conn, nil
 }
-*/
+
+// redialWait waits before attempting to redial, resetting the timer as appropriate
+func (d *HvsockDialer) redialWait(ctx context.Context) (err error) {
+	if d.RetryWait == 0 {
+		return nil
+	}
+
+	if d.rt == nil {
+		d.rt = time.NewTimer(d.RetryWait)
+	} else {
+		// should already be stopped and drained
+		d.rt.Reset(d.RetryWait)
+	}
+
+	select {
+	case <-ctx.Done():
+	case <-d.rt.C:
+		return nil
+	}
+
+	// stop and drain the timer
+	if !d.rt.Stop() {
+		<-d.rt.C
+	}
+	return ctx.Err()
+}
+
+// assumes error is a plain, unwrapped syscall.Errno provided by direct syscall
+func canRedial(err error) bool {
+	// nolint:errorlint
+	switch err {
+	case windows.WSAECONNREFUSED, windows.WSAENETUNREACH, windows.WSAETIMEDOUT,
+		windows.ERROR_CONNECTION_REFUSED, windows.ERROR_CONNECTION_UNAVAIL:
+		return true
+	default:
+		return false
+	}
+}
 
 func (conn *HvsockConn) opErr(op string, err error) error {
+	// translate from "file closed" to "socket closed"
+	if errors.Is(err, ErrFileClosed) {
+		err = socket.ErrSocketClosed
+	}
 	return &net.OpError{Op: op, Net: "hvsock", Source: &conn.local, Addr: &conn.remote, Err: err}
 }
 
@@ -206,8 +450,9 @@ func (conn *HvsockConn) Read(b []byte) (int, error) {
 	err = syscall.WSARecv(conn.sock.handle, &buf, 1, &bytes, &flags, &c.o, nil)
 	n, err := conn.sock.asyncIo(c, &conn.sock.readDeadline, bytes, err)
 	if err != nil {
-		if _, ok := err.(syscall.Errno); ok {
-			err = os.NewSyscallError("wsarecv", err)
+		var eno windows.Errno
+		if errors.As(err, &eno) {
+			err = os.NewSyscallError("wsarecv", eno)
 		}
 		return 0, conn.opErr("read", err)
 	} else if n == 0 {
@@ -240,8 +485,9 @@ func (conn *HvsockConn) write(b []byte) (int, error) {
 	err = syscall.WSASend(conn.sock.handle, &buf, 1, &bytes, 0, &c.o, nil)
 	n, err := conn.sock.asyncIo(c, &conn.sock.writeDeadline, bytes, err)
 	if err != nil {
-		if _, ok := err.(syscall.Errno); ok {
-			err = os.NewSyscallError("wsasend", err)
+		var eno windows.Errno
+		if errors.As(err, &eno) {
+			err = os.NewSyscallError("wsasend", eno)
 		}
 		return 0, conn.opErr("write", err)
 	}
@@ -257,13 +503,19 @@ func (conn *HvsockConn) IsClosed() bool {
 	return conn.sock.IsClosed()
 }
 
+// shutdown disables sending or receiving on a socket
 func (conn *HvsockConn) shutdown(how int) error {
 	if conn.IsClosed() {
-		return ErrFileClosed
+		return socket.ErrSocketClosed
 	}
 
 	err := syscall.Shutdown(conn.sock.handle, how)
 	if err != nil {
+		// If the connection was closed, shutdowns fail with "not connected"
+		if errors.Is(err, windows.WSAENOTCONN) ||
+			errors.Is(err, windows.WSAESHUTDOWN) {
+			err = socket.ErrSocketClosed
+		}
 		return os.NewSyscallError("shutdown", err)
 	}
 	return nil
@@ -273,7 +525,7 @@ func (conn *HvsockConn) shutdown(how int) error {
 func (conn *HvsockConn) CloseRead() error {
 	err := conn.shutdown(syscall.SHUT_RD)
 	if err != nil {
-		return conn.opErr("close", err)
+		return conn.opErr("closeread", err)
 	}
 	return nil
 }
@@ -283,7 +535,7 @@ func (conn *HvsockConn) CloseRead() error {
 func (conn *HvsockConn) CloseWrite() error {
 	err := conn.shutdown(syscall.SHUT_WR)
 	if err != nil {
-		return conn.opErr("close", err)
+		return conn.opErr("closewrite", err)
 	}
 	return nil
 }
@@ -300,8 +552,13 @@ func (conn *HvsockConn) RemoteAddr() net.Addr {
 
 // SetDeadline implements the net.Conn SetDeadline method.
 func (conn *HvsockConn) SetDeadline(t time.Time) error {
-	conn.SetReadDeadline(t)
-	conn.SetWriteDeadline(t)
+	// todo: implement `SetDeadline` for `win32File`
+	if err := conn.SetReadDeadline(t); err != nil {
+		return fmt.Errorf("set read deadline: %w", err)
+	}
+	if err := conn.SetWriteDeadline(t); err != nil {
+		return fmt.Errorf("set write deadline: %w", err)
+	}
 	return nil
 }
 

internal/socket/rawaddr.go

@@ -0,0 +1,20 @@
+package socket
+
+import (
+	"unsafe"
+)
+
+// RawSockaddr allows structs to be used with [Bind] and [ConnectEx]. The
+// struct must meet the Win32 sockaddr requirements specified here:
+// https://docs.microsoft.com/en-us/windows/win32/winsock/sockaddr-2
+//
+// Specifically, the struct size must be least larger than an int16 (unsigned short)
+// for the address family.
+type RawSockaddr interface {
+	// Sockaddr returns a pointer to the RawSockaddr and its struct size, allowing
+	// for the RawSockaddr's data to be overwritten by syscalls (if necessary).
+	//
+	// It is the callers responsibility to validate that the values are valid; invalid
+	// pointers or size can cause a panic.
+	Sockaddr() (unsafe.Pointer, int32, error)
+}

internal/socket/socket.go

@@ -0,0 +1,153 @@
+//go:build windows
+
+package socket
+
+import (
+	"errors"
+	"fmt"
+	"net"
+	"sync"
+	"syscall"
+	"unsafe"
+
+	"github.com/Microsoft/go-winio/pkg/guid"
+	"golang.org/x/sys/windows"
+)
+
+//go:generate go run golang.org/x/sys/windows/mkwinsyscall -output zsyscall_windows.go socket.go
+
+//sys getsockname(s windows.Handle, name unsafe.Pointer, namelen *int32) (err error) [failretval==socketError] = ws2_32.getsockname
+//sys getpeername(s windows.Handle, name unsafe.Pointer, namelen *int32) (err error) [failretval==socketError] = ws2_32.getpeername
+//sys bind(s windows.Handle, name unsafe.Pointer, namelen int32) (err error) [failretval==socketError] = ws2_32.bind
+
+const socketError = uintptr(^uint32(0))
+
+var (
+	// todo(helsaawy): create custom error types to store the desired vs actual size and addr family?
+
+	ErrBufferSize     = errors.New("buffer size")
+	ErrAddrFamily     = errors.New("address family")
+	ErrInvalidPointer = errors.New("invalid pointer")
+	ErrSocketClosed   = fmt.Errorf("socket closed: %w", net.ErrClosed)
+)
+
+// todo(helsaawy): replace these with generics, ie: GetSockName[S RawSockaddr](s windows.Handle) (S, error)
+
+// GetSockName writes the local address of socket s to the [RawSockaddr] rsa.
+// If rsa is not large enough, the [windows.WSAEFAULT] is returned.
+func GetSockName(s windows.Handle, rsa RawSockaddr) error {
+	ptr, l, err := rsa.Sockaddr()
+	if err != nil {
+		return fmt.Errorf("could not retrieve socket pointer and size: %w", err)
+	}
+
+	// although getsockname returns WSAEFAULT if the buffer is too small, it does not set
+	// &l to the correct size, so--apart from doubling the buffer repeatedly--there is no remedy
+	return getsockname(s, ptr, &l)
+}
+
+// GetPeerName returns the remote address the socket is connected to.
+//
+// See [GetSockName] for more information.
+func GetPeerName(s windows.Handle, rsa RawSockaddr) error {
+	ptr, l, err := rsa.Sockaddr()
+	if err != nil {
+		return fmt.Errorf("could not retrieve socket pointer and size: %w", err)
+	}
+
+	return getpeername(s, ptr, &l)
+}
+
+func Bind(s windows.Handle, rsa RawSockaddr) (err error) {
+	ptr, l, err := rsa.Sockaddr()
+	if err != nil {
+		return fmt.Errorf("could not retrieve socket pointer and size: %w", err)
+	}
+
+	return bind(s, ptr, l)
+}
+
+// "golang.org/x/sys/windows".ConnectEx and .Bind only accept internal implementations of the
+// their sockaddr interface, so they cannot be used with HvsockAddr
+// Replicate functionality here from
+// https://cs.opensource.google/go/x/sys/+/master:windows/syscall_windows.go
+
+// The function pointers to `AcceptEx`, `ConnectEx` and `GetAcceptExSockaddrs` must be loaded at
+// runtime via a WSAIoctl call:
+// https://docs.microsoft.com/en-us/windows/win32/api/Mswsock/nc-mswsock-lpfn_connectex#remarks
+
+type runtimeFunc struct {
+	id   guid.GUID
+	once sync.Once
+	addr uintptr
+	err  error
+}
+
+func (f *runtimeFunc) Load() error {
+	f.once.Do(func() {
+		var s windows.Handle
+		s, f.err = windows.Socket(windows.AF_INET, windows.SOCK_STREAM, windows.IPPROTO_TCP)
+		if f.err != nil {
+			return
+		}
+		defer windows.CloseHandle(s) //nolint:errcheck
+
+		var n uint32
+		f.err = windows.WSAIoctl(s,
+			windows.SIO_GET_EXTENSION_FUNCTION_POINTER,
+			(*byte)(unsafe.Pointer(&f.id)),
+			uint32(unsafe.Sizeof(f.id)),
+			(*byte)(unsafe.Pointer(&f.addr)),
+			uint32(unsafe.Sizeof(f.addr)),
+			&n,
+			nil, //overlapped
+			0,   //completionRoutine
+		)
+	})
+	return f.err
+}
+
+var (
+	// todo: add `AcceptEx` and `GetAcceptExSockaddrs`
+	WSAID_CONNECTEX = guid.GUID{ //nolint:revive,stylecheck
+		Data1: 0x25a207b9,
+		Data2: 0xddf3,
+		Data3: 0x4660,
+		Data4: [8]byte{0x8e, 0xe9, 0x76, 0xe5, 0x8c, 0x74, 0x06, 0x3e},
+	}
+
+	connectExFunc = runtimeFunc{id: WSAID_CONNECTEX}
+)
+
+func ConnectEx(fd windows.Handle, rsa RawSockaddr, sendBuf *byte, sendDataLen uint32, bytesSent *uint32, overlapped *windows.Overlapped) error {
+	if err := connectExFunc.Load(); err != nil {
+		return fmt.Errorf("failed to load ConnectEx function pointer: %w", err)
+	}
+	ptr, n, err := rsa.Sockaddr()
+	if err != nil {
+		return err
+	}
+	return connectEx(fd, ptr, n, sendBuf, sendDataLen, bytesSent, overlapped)
+}
+
+// BOOL LpfnConnectex(
+//   [in]           SOCKET s,
+//   [in]           const sockaddr *name,
+//   [in]           int namelen,
+//   [in, optional] PVOID lpSendBuffer,
+//   [in]           DWORD dwSendDataLength,
+//   [out]          LPDWORD lpdwBytesSent,
+//   [in]           LPOVERLAPPED lpOverlapped
+// )
+func connectEx(s windows.Handle, name unsafe.Pointer, namelen int32, sendBuf *byte, sendDataLen uint32, bytesSent *uint32, overlapped *windows.Overlapped) (err error) {
+	// todo: after upgrading to 1.18, switch from syscall.Syscall9 to syscall.SyscallN
+	r1, _, e1 := syscall.Syscall9(connectExFunc.addr, 7, uintptr(s), uintptr(name), uintptr(namelen), uintptr(unsafe.Pointer(sendBuf)), uintptr(sendDataLen), uintptr(unsafe.Pointer(bytesSent)), uintptr(unsafe.Pointer(overlapped)), 0, 0)
+	if r1 == 0 {
+		if e1 != 0 {
+			err = error(e1)
+		} else {
+			err = syscall.EINVAL
+		}
+	}
+	return
+}

internal/socket/zsyscall_windows.go

@@ -0,0 +1,70 @@
+// Code generated by 'go generate'; DO NOT EDIT.
+
+package socket
+
+import (
+	"syscall"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+var _ unsafe.Pointer
+
+// Do the interface allocations only once for common
+// Errno values.
+const (
+	errnoERROR_IO_PENDING = 997
+)
+
+var (
+	errERROR_IO_PENDING error = syscall.Errno(errnoERROR_IO_PENDING)
+	errERROR_EINVAL     error = syscall.EINVAL
+)
+
+// errnoErr returns common boxed Errno values, to prevent
+// allocations at runtime.
+func errnoErr(e syscall.Errno) error {
+	switch e {
+	case 0:
+		return errERROR_EINVAL
+	case errnoERROR_IO_PENDING:
+		return errERROR_IO_PENDING
+	}
+	// TODO: add more here, after collecting data on the common
+	// error values see on Windows. (perhaps when running
+	// all.bat?)
+	return e
+}
+
+var (
+	modws2_32 = windows.NewLazySystemDLL("ws2_32.dll")
+
+	procbind        = modws2_32.NewProc("bind")
+	procgetpeername = modws2_32.NewProc("getpeername")
+	procgetsockname = modws2_32.NewProc("getsockname")
+)
+
+func bind(s windows.Handle, name unsafe.Pointer, namelen int32) (err error) {
+	r1, _, e1 := syscall.Syscall(procbind.Addr(), 3, uintptr(s), uintptr(name), uintptr(namelen))
+	if r1 == socketError {
+		err = errnoErr(e1)
+	}
+	return
+}
+
+func getpeername(s windows.Handle, name unsafe.Pointer, namelen *int32) (err error) {
+	r1, _, e1 := syscall.Syscall(procgetpeername.Addr(), 3, uintptr(s), uintptr(name), uintptr(unsafe.Pointer(namelen)))
+	if r1 == socketError {
+		err = errnoErr(e1)
+	}
+	return
+}
+
+func getsockname(s windows.Handle, name unsafe.Pointer, namelen *int32) (err error) {
+	r1, _, e1 := syscall.Syscall(procgetsockname.Addr(), 3, uintptr(s), uintptr(name), uintptr(unsafe.Pointer(namelen)))
+	if r1 == socketError {
+		err = errnoErr(e1)
+	}
+	return
+}

zsyscall_windows.go

@@ -78,7 +78,6 @@ var (
 	procRtlDosPathNameToNtPathName_U                         = modntdll.NewProc("RtlDosPathNameToNtPathName_U")
 	procRtlNtStatusToDosErrorNoTeb                           = modntdll.NewProc("RtlNtStatusToDosErrorNoTeb")
 	procWSAGetOverlappedResult                               = modws2_32.NewProc("WSAGetOverlappedResult")
-	procbind                                                 = modws2_32.NewProc("bind")
 )
 
 func adjustTokenPrivileges(token windows.Token, releaseAll bool, input *byte, outputSize uint32, output *byte, requiredSize *uint32) (success bool, err error) {
@@ -437,11 +436,3 @@ func wsaGetOverlappedResult(h syscall.Handle, o *syscall.Overlapped, bytes *uint
 	}
 	return
 }
-
-func bind(s syscall.Handle, name unsafe.Pointer, namelen int32) (err error) {
-	r1, _, e1 := syscall.Syscall(procbind.Addr(), 3, uintptr(s), uintptr(name), uintptr(namelen))
-	if r1 == socketError {
-		err = errnoErr(e1)
-	}
-	return
-}