net: consolidate the existing Windows version checks

Change-Id: I9c0ad69bd61923e9e272f157dc380a9120f08423
Reviewed-on: https://go-review.googlesource.com/c/go/+/565595
Reviewed-by: Bryan Mills <bcmills@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Damien Neil <dneil@google.com>

src/internal/syscall/windows/net_windows.go

@@ -5,7 +5,6 @@
 package windows
 
 import (
-	"sync"
 	"syscall"
 	_ "unsafe"
 )
@@ -28,13 +27,3 @@ type TCP_INITIAL_RTO_PARAMETERS struct {
 	Rtt                   uint16
 	MaxSynRetransmissions uint8
 }
-
-var Support_TCP_INITIAL_RTO_NO_SYN_RETRANSMISSIONS = sync.OnceValue(func() bool {
-	var maj, min, build uint32
-	rtlGetNtVersionNumbers(&maj, &min, &build)
-	return maj >= 10 && build&0xffff >= 16299
-})
-
-//go:linkname rtlGetNtVersionNumbers syscall.rtlGetNtVersionNumbers
-//go:noescape
-func rtlGetNtVersionNumbers(majorVersion *uint32, minorVersion *uint32, buildNumber *uint32)

src/internal/syscall/windows/version_windows.go

@@ -4,7 +4,10 @@
 
 package windows
 
-import "sync"
+import (
+	"sync"
+	_ "unsafe" // for linkname
+)
 
 // Version retrieves the major, minor, and build version numbers
 // of the current Windows OS from the RtlGetNtVersionNumbers API
@@ -15,6 +18,10 @@ func Version() (major, minor, build uint32) {
 	return
 }
 
+//go:linkname rtlGetNtVersionNumbers syscall.rtlGetNtVersionNumbers
+//go:noescape
+func rtlGetNtVersionNumbers(majorVersion *uint32, minorVersion *uint32, buildNumber *uint32)
+
 // SupportFullTCPKeepAlive indicates whether the current Windows version
 // supports the full TCP keep-alive configurations, the minimal requirement
 // is Windows 10, version 1709.
@@ -22,3 +29,18 @@ var SupportFullTCPKeepAlive = sync.OnceValue(func() bool {
 	major, _, build := Version()
 	return major >= 10 && build >= 16299
 })
+
+// SupportTCPInitialRTONoSYNRetransmissions indicates whether the current
+// Windows version supports the TCP_INITIAL_RTO_NO_SYN_RETRANSMISSIONS, the
+// minimal requirement is Windows 10.0.16299.
+var SupportTCPInitialRTONoSYNRetransmissions = sync.OnceValue(func() bool {
+	major, _, build := Version()
+	return major >= 10 && build >= 16299
+})
+
+// SupportUnixSocket indicates whether the current Windows version supports
+// Unix Domain Sockets, the minimal requirement is Windows 10, build 17063.
+var SupportUnixSocket = sync.OnceValue(func() bool {
+	major, _, build := Version()
+	return major >= 10 && build >= 17063
+})

src/net/fd_windows.go

@@ -135,7 +135,7 @@ func (fd *netFD) connect(ctx context.Context, la, ra syscall.Sockaddr) (syscall.
 			Rtt:                   windows.TCP_INITIAL_RTO_UNSPECIFIED_RTT, // use the default or overridden by the Administrator
 			MaxSynRetransmissions: 1,                                       // minimum possible value before Windows 10.0.16299
 		}
-		if windows.Support_TCP_INITIAL_RTO_NO_SYN_RETRANSMISSIONS() {
+		if windows.SupportTCPInitialRTONoSYNRetransmissions() {
 			// In Windows 10.0.16299 TCP_INITIAL_RTO_NO_SYN_RETRANSMISSIONS makes ConnectEx() fails instantly.
 			params.MaxSynRetransmissions = windows.TCP_INITIAL_RTO_NO_SYN_RETRANSMISSIONS
 		}

src/net/unixsock_windows_test.go

@@ -7,34 +7,15 @@
 package net
 
 import (
-	"internal/syscall/windows/registry"
+	"internal/syscall/windows"
 	"os"
 	"reflect"
 	"runtime"
-	"strconv"
 	"testing"
 )
 
-func isBuild17063() bool {
-	k, err := registry.OpenKey(registry.LOCAL_MACHINE, `SOFTWARE\Microsoft\Windows NT\CurrentVersion`, registry.READ)
-	if err != nil {
-		return false
-	}
-	defer k.Close()
-
-	s, _, err := k.GetStringValue("CurrentBuild")
-	if err != nil {
-		return false
-	}
-	ver, err := strconv.Atoi(s)
-	if err != nil {
-		return false
-	}
-	return ver >= 17063
-}
-
 func skipIfUnixSocketNotSupported(t *testing.T) {
-	// TODO: the isBuild17063 check should be enough, investigate why 386 and arm
+	// TODO: the windows.SupportUnixSocket check should be enough, investigate why 386 and arm
 	// can't run these tests on newer Windows.
 	switch runtime.GOARCH {
 	case "386":
@@ -42,7 +23,7 @@ func skipIfUnixSocketNotSupported(t *testing.T) {
 	case "arm":
 		t.Skip("not supported on windows/arm, see golang.org/issue/28061")
 	}
-	if !isBuild17063() {
+	if !windows.SupportUnixSocket() {
 		t.Skip("unix test")
 	}
 }