net/{batching,packet},wgengine/magicsock: export batchingConn (#16848)

For eventual use by net/udprelay.Server.

Updates tailscale/corp#31164

Signed-off-by: Jordan Whited <jordan@tailscale.com>

net/packet/geneve_test.go

@@ -4,18 +4,21 @@
 package packet
 
 import (
+	"math"
 	"testing"
 
 	"github.com/google/go-cmp/cmp"
+	"github.com/google/go-cmp/cmp/cmpopts"
+	"tailscale.com/types/ptr"
 )
 
 func TestGeneveHeader(t *testing.T) {
 	in := GeneveHeader{
 		Version:  3,
 		Protocol: GeneveProtocolDisco,
-		VNI:      1<<24 - 1,
 		Control:  true,
 	}
+	in.VNI.Set(1<<24 - 1)
 	b := make([]byte, GeneveFixedHeaderLength)
 	err := in.Encode(b)
 	if err != nil {
@@ -26,7 +29,56 @@ func TestGeneveHeader(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	if diff := cmp.Diff(out, in); diff != "" {
+	if diff := cmp.Diff(out, in, cmpopts.EquateComparable(VirtualNetworkID{})); diff != "" {
 		t.Fatalf("wrong results (-got +want)\n%s", diff)
 	}
 }
+
+func TestVirtualNetworkID(t *testing.T) {
+	tests := []struct {
+		name string
+		set  *uint32
+		want uint32
+	}{
+		{
+			"don't Set",
+			nil,
+			0,
+		},
+		{
+			"Set 0",
+			ptr.To(uint32(0)),
+			0,
+		},
+		{
+			"Set 1",
+			ptr.To(uint32(1)),
+			1,
+		},
+		{
+			"Set math.MaxUint32",
+			ptr.To(uint32(math.MaxUint32)),
+			1<<24 - 1,
+		},
+		{
+			"Set max 3-byte value",
+			ptr.To(uint32(1<<24 - 1)),
+			1<<24 - 1,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			v := VirtualNetworkID{}
+			if tt.set != nil {
+				v.Set(*tt.set)
+			}
+			if v.IsSet() != (tt.set != nil) {
+				t.Fatalf("IsSet: %v != wantIsSet: %v", v.IsSet(), tt.set != nil)
+			}
+			if v.Get() != tt.want {
+				t.Fatalf("Get(): %v != want: %v", v.Get(), tt.want)
+			}
+		})
+	}
+}