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())
+}

util/netconv/netconv_test.go

@@ -0,0 +1,76 @@
+// 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
+
+import (
+	"net/netip"
+	"testing"
+
+	qt "github.com/frankban/quicktest"
+	"inet.af/netaddr"
+)
+
+func TestAddr(t *testing.T) {
+	c := qt.New(t)
+
+	c.Assert(netip.Addr{}, qt.Equals, AsAddr(netaddr.IP{}))
+	c.Assert(netaddr.IP{}, qt.Equals, AsIP(netip.Addr{}))
+
+	// Cover IPv4, IPv6, 4in6, and zones.
+	addrStrs := []string{
+		"0.0.0.0",
+		"123.45.67.89",
+		"::",
+		"fd7a:115c:a1e0:ab12:4843:cd96:626b:430b",
+		"fd7a:115c:a1e0:ab12:4843:cd96:626b:430b%eth0",
+		"::ffff:192.0.2.128",
+		"::ffff:192.0.2.128%eth0",
+	}
+	for _, s := range addrStrs {
+		ip := netaddr.MustParseIP(s)
+		addr := netip.MustParseAddr(s)
+		c.Assert(addr, qt.Equals, AsAddr(ip))
+		c.Assert(ip, qt.Equals, AsIP(addr))
+	}
+}
+
+func TestAddrPort(t *testing.T) {
+	c := qt.New(t)
+
+	c.Assert(netip.AddrPort{}, qt.Equals, AsAddrPort(netaddr.IPPort{}))
+	c.Assert(netaddr.IPPort{}, qt.Equals, AsIPPort(netip.AddrPort{}))
+
+	// Test just a single AddrPort conversion;
+	// there's almost nothing happening in the code.
+	portStr := "1.2.4.5:8"
+	ipPort := netaddr.MustParseIPPort(portStr)
+	ap := netip.MustParseAddrPort(portStr)
+	c.Assert(ipPort, qt.Equals, AsIPPort(ap))
+	c.Assert(ap, qt.Equals, AsAddrPort(ipPort))
+}
+
+func TestPrefix(t *testing.T) {
+	c := qt.New(t)
+
+	// The interesting Prefix cases are invalid bits.
+	addr := netip.MustParseAddr("1.2.3.4")
+	ip := AsIP(addr)
+
+	tests := []struct {
+		ipp netaddr.IPPrefix // input IPPrefix, output from converting pfx
+		pfx netip.Prefix     // input Prefix, output from converting ipp
+		out netaddr.IPPrefix // output from converting pfx
+	}{
+		{netaddr.IPPrefix{}, netip.Prefix{}, netaddr.IPPrefix{}},
+		{netaddr.IPPrefixFrom(ip, 24), netip.PrefixFrom(addr, 24), netaddr.IPPrefixFrom(ip, 24)},
+		{netaddr.IPPrefixFrom(ip, 255), netip.PrefixFrom(addr, -1), netaddr.IPPrefixFrom(ip, 255)},
+		{netaddr.IPPrefixFrom(ip, 204), netip.PrefixFrom(addr, -1), netaddr.IPPrefixFrom(ip, 255)},
+	}
+
+	for _, test := range tests {
+		c.Assert(test.out, qt.Equals, AsIPPrefix(test.pfx))
+		c.Assert(test.pfx, qt.Equals, AsPrefix(test.ipp))
+	}
+}