util/netconv: add package to convert between netip and netaddr types

Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>

util/netconv/netconv.go

@@ -0,0 +1,63 @@
+// Copyright (c) 2022 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.
+
+// Package netconv provides utilities to convert between netaddr and netip.
+// To convert from a net.IP, use the netaddr/netip API.
+package netconv
+
+import (
+	"net/netip"
+
+	"inet.af/netaddr"
+)
+
+// AsIP returns a as a netaddr.IP.
+func AsIP(a netip.Addr) netaddr.IP {
+	switch {
+	case a.Is4():
+		return netaddr.IPFrom4(a.As4())
+	case a.Is6():
+		return netaddr.IPv6Raw(a.As16()).WithZone(a.Zone())
+	}
+	return netaddr.IP{}
+}
+
+// AsAddr returns a as a netip.IP.
+func AsAddr(a netaddr.IP) netip.Addr {
+	switch {
+	case a.Is4():
+		return netip.AddrFrom4(a.As4())
+	case a.Is6():
+		return netip.AddrFrom16(a.As16()).WithZone(a.Zone())
+	}
+	return netip.Addr{}
+}
+
+// AsIPPrefix returns a as a netaddr.IPPrefix.
+// If a has Bits of -1, indicating an invalid bits,
+// the returned IPPrefix will have Bits of 255.
+// AsIPPrefix and AsPrefix do not
+// round trip for invalid Bits values.
+func AsIPPrefix(a netip.Prefix) netaddr.IPPrefix {
+	return netaddr.IPPrefixFrom(AsIP(a.Addr()), uint8(a.Bits()))
+}
+
+// AsPrefix returns a as a netip.Prefix.
+// If a has an invalid Bits value,
+// the returned Prefix will have Bits of -1.
+// AsIPPrefix and AsPrefix do not
+// round trip for invalid Bits values.
+func AsPrefix(a netaddr.IPPrefix) netip.Prefix {
+	return netip.PrefixFrom(AsAddr(a.IP()), int(a.Bits()))
+}
+
+// AsIPPort returns a as a netaddr.IPPort.
+func AsIPPort(a netip.AddrPort) netaddr.IPPort {
+	return netaddr.IPPortFrom(AsIP(a.Addr()), a.Port())
+}
+
+// AsAddrPort returns a as a netip.AddrPort.
+func AsAddrPort(a netaddr.IPPort) netip.AddrPort {
+	return netip.AddrPortFrom(AsAddr(a.IP()), a.Port())
+}