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>

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
+}