From 640a5606a855a275cda5b8862221ae32b09b6a35 Mon Sep 17 00:00:00 2001
From: kiashok <99994218+kiashok@users.noreply.github.com>
Date: Wed, 5 Jul 2023 09:51:20 -0700
Subject: [PATCH] Add support for platform compatibility check for windows
 (#1821)

Signed-off-by: Kirtana Ashok <kiashok@microsoft.com>
---
 osversion/platform_compat_windows.go      | 35 ++++++++++++
 osversion/platform_compat_windows_test.go | 68 +++++++++++++++++++++++
 2 files changed, 103 insertions(+)
 create mode 100644 osversion/platform_compat_windows.go
 create mode 100644 osversion/platform_compat_windows_test.go

diff --git a/osversion/platform_compat_windows.go b/osversion/platform_compat_windows.go
new file mode 100644
index 0000000000..f8d411ad7e
--- /dev/null
+++ b/osversion/platform_compat_windows.go
@@ -0,0 +1,35 @@
+package osversion
+
+// List of stable ABI compliant ltsc releases
+// Note: List must be sorted in ascending order
+var compatLTSCReleases = []uint16{
+	V21H2Server,
+}
+
+// CheckHostAndContainerCompat checks if given host and container
+// OS versions are compatible.
+// It includes support for stable ABI compliant versions as well.
+// Every release after WS 2022 will support the previous ltsc
+// container image. Stable ABI is in preview mode for windows 11 client.
+// Refer: https://learn.microsoft.com/en-us/virtualization/windowscontainers/deploy-containers/version-compatibility?tabs=windows-server-2022%2Cwindows-10#windows-server-host-os-compatibility
+func CheckHostAndContainerCompat(host, ctr OSVersion) bool {
+	// check major minor versions of host and guest
+	if host.MajorVersion != ctr.MajorVersion ||
+		host.MinorVersion != ctr.MinorVersion {
+		return false
+	}
+
+	// If host is < WS 2022, exact version match is required
+	if host.Build < V21H2Server {
+		return host.Build == ctr.Build
+	}
+
+	var supportedLtscRelease uint16
+	for i := len(compatLTSCReleases) - 1; i >= 0; i-- {
+		if host.Build >= compatLTSCReleases[i] {
+			supportedLtscRelease = compatLTSCReleases[i]
+			break
+		}
+	}
+	return ctr.Build >= supportedLtscRelease && ctr.Build <= host.Build
+}
diff --git a/osversion/platform_compat_windows_test.go b/osversion/platform_compat_windows_test.go
new file mode 100644
index 0000000000..bafa612d13
--- /dev/null
+++ b/osversion/platform_compat_windows_test.go
@@ -0,0 +1,68 @@
+package osversion
+
+import (
+	"testing"
+)
+
+// Test the platform compatibility of the different
+// OS Versions considering two ltsc container image
+// versions (ltsc2019, ltsc2022)
+func Test_PlatformCompat(t *testing.T) {
+	for testName, tc := range map[string]struct {
+		hostOs    uint16
+		ctrOs     uint16
+		shouldRun bool
+	}{
+		"RS5Host_ltsc2019": {
+			hostOs:    RS5,
+			ctrOs:     RS5,
+			shouldRun: true,
+		},
+		"RS5Host_ltsc2022": {
+			hostOs:    RS5,
+			ctrOs:     V21H2Server,
+			shouldRun: false,
+		},
+		"WS2022Host_ltsc2019": {
+			hostOs:    V21H2Server,
+			ctrOs:     RS5,
+			shouldRun: false,
+		},
+		"WS2022Host_ltsc2022": {
+			hostOs:    V21H2Server,
+			ctrOs:     V21H2Server,
+			shouldRun: true,
+		},
+		"Wind11Host_ltsc2019": {
+			hostOs:    V22H2Win11,
+			ctrOs:     RS5,
+			shouldRun: false,
+		},
+		"Wind11Host_ltsc2022": {
+			hostOs:    V22H2Win11,
+			ctrOs:     V21H2Server,
+			shouldRun: true,
+		},
+	} {
+		// Check if ltsc2019/ltsc2022 guest images are compatible on
+		// the given host OS versions
+		//
+		hostOSVersion := OSVersion{
+			MajorVersion: 10,
+			MinorVersion: 0,
+			Build:        tc.hostOs,
+		}
+		ctrOSVersion := OSVersion{
+			MajorVersion: 10,
+			MinorVersion: 0,
+			Build:        tc.ctrOs,
+		}
+		if CheckHostAndContainerCompat(hostOSVersion, ctrOSVersion) != tc.shouldRun {
+			var expectedResultStr string
+			if !tc.shouldRun {
+				expectedResultStr = " NOT"
+			}
+			t.Fatalf("Failed %v: host %v should%s be able to run guest %v", testName, tc.hostOs, expectedResultStr, tc.ctrOs)
+		}
+	}
+}