Add WS2025 to Windows matcher and code optimizations

Signed-off-by: Kirtana Ashok <kiashok@microsoft.com>

Author: kiashok

platform_windows_compat.go

@@ -41,19 +41,31 @@ type windowsOSVersion struct {
 const (
 	// rs5 (version 1809, codename "Redstone 5") corresponds to Windows Server
 	// 2019 (ltsc2019), and Windows 10 (October 2018 Update).
-	rs5 = 17763
+	RS5 = 17763
+	// LTSC2019 (Windows Server 2019) is an alias for [RS5].
+	LTSC2019 = RS5
 
-	// v21H2Server corresponds to Windows Server 2022 (ltsc2022).
-	v21H2Server = 20348
+	// V21H2Server corresponds to Windows Server 2022 (ltsc2022).
+	V21H2Server = 20348
+	// LTSC2022 (Windows Server 2022) is an alias for [V21H2Server]
+	LTSC2022 = V21H2Server
 
-	// v22H2Win11 corresponds to Windows 11 (2022 Update).
-	v22H2Win11 = 22621
+	// V22H2Win11 corresponds to Windows 11 (2022 Update).
+	V22H2Win11 = 22621
+
+	// V23H2 is the 23H2 release in the Windows Server annual channel.
+	V23H2 = 25398
+
+	// Windows Server 2025 build 26100
+	V25H1Server = 26100
+	LTSC2025    = V25H1Server
 )
 
 // List of stable ABI compliant ltsc releases
 // Note: List must be sorted in ascending order
 var compatLTSCReleases = []uint16{
-	v21H2Server,
+	LTSC2022,
+	LTSC2025,
 }
 
 // CheckHostAndContainerCompat checks if given host and container
@@ -70,18 +82,27 @@ func checkWindowsHostAndContainerCompat(host, ctr windowsOSVersion) bool {
 	}
 
 	// If host is < WS 2022, exact version match is required
-	if host.Build < v21H2Server {
+	if host.Build < LTSC2022 {
 		return host.Build == ctr.Build
 	}
 
-	var supportedLtscRelease uint16
+	// Find the latest LTSC version that is earlier than the host version.
+	// This is the earliest version of container that the host can run.
+	//
+	// If the host version is an LTSC, then it supports compatibility with
+	// everything from the previous LTSC up to itself, so we want supportedLTSCRelease
+	// to be the previous entry.
+	//
+	// If no match is found, then we know that the host is LTSC2022 exactly,
+	// since we already checked that it's not less than LTSC2022.
+	var supportedLTSCRelease uint16 = LTSC2022
 	for i := len(compatLTSCReleases) - 1; i >= 0; i-- {
-		if host.Build >= compatLTSCReleases[i] {
-			supportedLtscRelease = compatLTSCReleases[i]
+		if host.Build > compatLTSCReleases[i] {
+			supportedLTSCRelease = compatLTSCReleases[i]
 			break
 		}
 	}
-	return ctr.Build >= supportedLtscRelease && ctr.Build <= host.Build
+	return supportedLTSCRelease <= ctr.Build && ctr.Build <= host.Build
 }
 
 func getWindowsOSVersion(osVersionPrefix string) windowsOSVersion {

platform_windows_compat_test.go

@@ -17,68 +17,86 @@
 package platforms
 
 import (
+	"fmt"
 	"testing"
 )
 
-// Test the platform compatibility of the different
-// OS Versions considering two ltsc container image
-// versions (ltsc2019, ltsc2022)
+// Test the platform compatibility of the different OS Versions
 func Test_PlatformCompat(t *testing.T) {
-	for testName, tc := range map[string]struct {
-		hostOs    uint16
-		ctrOs     uint16
+	for _, tc := range []struct {
+		hostOS    uint16
+		ctrOS     uint16
 		shouldRun bool
 	}{
-		"RS5Host_ltsc2019": {
-			hostOs:    rs5,
-			ctrOs:     rs5,
+		{
+			hostOS:    LTSC2019,
+			ctrOS:     LTSC2019,
 			shouldRun: true,
 		},
-		"RS5Host_ltsc2022": {
-			hostOs:    rs5,
-			ctrOs:     v21H2Server,
+		{
+			hostOS:    LTSC2019,
+			ctrOS:     LTSC2022,
 			shouldRun: false,
 		},
-		"WS2022Host_ltsc2019": {
-			hostOs:    v21H2Server,
-			ctrOs:     rs5,
+		{
+			hostOS:    LTSC2022,
+			ctrOS:     LTSC2019,
 			shouldRun: false,
 		},
-		"WS2022Host_ltsc2022": {
-			hostOs:    v21H2Server,
-			ctrOs:     v21H2Server,
+		{
+			hostOS:    LTSC2022,
+			ctrOS:     LTSC2022,
 			shouldRun: true,
 		},
-		"Wind11Host_ltsc2019": {
-			hostOs:    v22H2Win11,
-			ctrOs:     rs5,
+		{
+			hostOS:    V22H2Win11,
+			ctrOS:     LTSC2019,
 			shouldRun: false,
 		},
-		"Wind11Host_ltsc2022": {
-			hostOs:    v22H2Win11,
-			ctrOs:     v21H2Server,
+		{
+			hostOS:    V22H2Win11,
+			ctrOS:     LTSC2022,
+			shouldRun: true,
+		},
+		{
+			hostOS:    LTSC2025,
+			ctrOS:     LTSC2022,
+			shouldRun: true,
+		},
+		{
+			hostOS:    LTSC2022,
+			ctrOS:     LTSC2025,
+			shouldRun: false,
+		},
+		{
+			hostOS:    LTSC2022,
+			ctrOS:     V22H2Win11,
+			shouldRun: false,
+		},
+		{
+			hostOS:    LTSC2025,
+			ctrOS:     V22H2Win11,
 			shouldRun: true,
 		},
 	} {
-		// Check if ltsc2019/ltsc2022 guest images are compatible on
-		// the given host OS versions
-		//
-		hostOSVersion := windowsOSVersion{
-			MajorVersion: 10,
-			MinorVersion: 0,
-			Build:        tc.hostOs,
-		}
-		ctrOSVersion := windowsOSVersion{
-			MajorVersion: 10,
-			MinorVersion: 0,
-			Build:        tc.ctrOs,
-		}
-		if checkWindowsHostAndContainerCompat(hostOSVersion, ctrOSVersion) != tc.shouldRun {
-			var expectedResultStr string
-			if !tc.shouldRun {
-				expectedResultStr = " NOT"
+		t.Run(fmt.Sprintf("Host_%d_Ctr_%d", tc.hostOS, tc.ctrOS), func(t *testing.T) {
+			hostOSVersion := windowsOSVersion{
+				MajorVersion: 10,
+				MinorVersion: 0,
+				Build:        tc.hostOS,
+			}
+			ctrOSVersion := windowsOSVersion{
+				MajorVersion: 10,
+				MinorVersion: 0,
+				Build:        tc.ctrOS,
+			}
+			if checkWindowsHostAndContainerCompat(hostOSVersion, ctrOSVersion) != tc.shouldRun {
+				var expectedResultStr string
+				if !tc.shouldRun {
+					expectedResultStr = " NOT"
+				}
+				t.Fatalf("host %v should%s be able to run guest %v", tc.hostOS, expectedResultStr, tc.ctrOS)
 			}
-			t.Fatalf("Failed %v: host %v should%s be able to run guest %v", testName, tc.hostOs, expectedResultStr, tc.ctrOs)
-		}
+		})
 	}
 }