initial capver packet tracking version (#2391)

* initial capver packet tracking version

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>

* Log the minimum version as client version, not only capver

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>

* remove old versions

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>

* use capver for integration tests

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>

* changelog

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>

* patch through m and n key

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>

---------

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>

hscontrol/capver/capver_test.go

@@ -0,0 +1,53 @@
+package capver
+
+import (
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+	"tailscale.com/tailcfg"
+)
+
+func TestTailscaleLatestMajorMinor(t *testing.T) {
+	tests := []struct {
+		n        int
+		stripV   bool
+		expected []string
+	}{
+		{3, false, []string{"v1.74", "v1.76", "v1.78"}},
+		{2, true, []string{"1.76", "1.78"}},
+		{0, false, nil},
+	}
+
+	for _, test := range tests {
+		t.Run("", func(t *testing.T) {
+			output := TailscaleLatestMajorMinor(test.n, test.stripV)
+			if diff := cmp.Diff(output, test.expected); diff != "" {
+				t.Errorf("TailscaleLatestMajorMinor(%d, %v) mismatch (-want +got):\n%s", test.n, test.stripV, diff)
+			}
+		})
+	}
+}
+
+func TestCapVerMinimumTailscaleVersion(t *testing.T) {
+	tests := []struct {
+		input    tailcfg.CapabilityVersion
+		expected string
+	}{
+		{85, "v1.58.0"},
+		{90, "v1.64.0"},
+		{95, "v1.66.0"},
+		{106, "v1.74.0"},
+		{109, "v1.78.0"},
+		{9001, ""}, // Test case for a version higher than any in the map
+		{60, ""},   // Test case for a version lower than any in the map
+	}
+
+	for _, test := range tests {
+		t.Run("", func(t *testing.T) {
+			output := TailscaleVersion(test.input)
+			if output != test.expected {
+				t.Errorf("CapVerFromTailscaleVersion(%d) = %s; want %s", test.input, output, test.expected)
+			}
+		})
+	}
+}