wgengine/filter: add a Clone method.

Signed-off-by: David Anderson <danderson@tailscale.com>

wgengine/filter/match.go

@@ -12,6 +12,8 @@ import (
 	"tailscale.com/net/packet"
 )
 
+//go:generate go run tailscale.com/cmd/cloner --type=Match --output=match_clone.go
+
 // PortRange is a range of TCP and UDP ports.
 type PortRange struct {
 	First, Last uint16 // inclusive

wgengine/filter/match_clone.go

@@ -0,0 +1,31 @@
+// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Code generated by tailscale.com/cmd/cloner -type Match; DO NOT EDIT.
+
+package filter
+
+import (
+	"inet.af/netaddr"
+)
+
+// Clone makes a deep copy of Match.
+// The result aliases no memory with the original.
+func (src *Match) Clone() *Match {
+	if src == nil {
+		return nil
+	}
+	dst := new(Match)
+	*dst = *src
+	dst.Dsts = append(src.Dsts[:0:0], src.Dsts...)
+	dst.Srcs = append(src.Srcs[:0:0], src.Srcs...)
+	return dst
+}
+
+// A compilation failure here means this code must be regenerated, with command:
+//   tailscale.com/cmd/cloner -type Match
+var _MatchNeedsRegeneration = Match(struct {
+	Dsts []NetPortRange
+	Srcs []netaddr.IPPrefix
+}{})