libgo: update to Go1.18beta2

gotools/
	* Makefile.am (go_cmd_cgo_files): Add ast_go118.go
	(check-go-tool): Copy golang.org/x/tools directories.
	* Makefile.in: Regenerate.

Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/384695

1 files changed, 1974 insertions, 0 deletions

diff --git a/libgo/go/net/netip/netip_test.go b/libgo/go/net/netip/netip_test.go
new file mode 100644
index 00000000000..d988864827b
--- /dev/null
+++ b/libgo/go/net/netip/netip_test.go
@@ -0,0 +1,1974 @@
+// Copyright 2020 The Go 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 netip_test
+
+import (
+	"bytes"
+	"encoding/json"
+	"flag"
+	"fmt"
+	"internal/intern"
+	"net"
+	. "net/netip"
+	"reflect"
+	"sort"
+	"strings"
+	"testing"
+)
+
+var long = flag.Bool("long", false, "run long tests")
+
+type uint128 = Uint128
+
+var (
+	mustPrefix = MustParsePrefix
+	mustIP     = MustParseAddr
+	mustIPPort = MustParseAddrPort
+)
+
+func TestParseAddr(t *testing.T) {
+	var validIPs = []struct {
+		in      string
+		ip      Addr   // output of ParseAddr()
+		str     string // output of String(). If "", use in.
+		wantErr string
+	}{
+		// Basic zero IPv4 address.
+		{
+			in: "0.0.0.0",
+			ip: MkAddr(Mk128(0, 0xffff00000000), Z4),
+		},
+		// Basic non-zero IPv4 address.
+		{
+			in: "192.168.140.255",
+			ip: MkAddr(Mk128(0, 0xffffc0a88cff), Z4),
+		},
+		// IPv4 address in windows-style "print all the digits" form.
+		{
+			in:      "010.000.015.001",
+			wantErr: `ParseAddr("010.000.015.001"): IPv4 field has octet with leading zero`,
+		},
+		// IPv4 address with a silly amount of leading zeros.
+		{
+			in:      "000001.00000002.00000003.000000004",
+			wantErr: `ParseAddr("000001.00000002.00000003.000000004"): IPv4 field has octet with leading zero`,
+		},
+		// 4-in-6 with octet with leading zero
+		{
+			in:      "::ffff:1.2.03.4",
+			wantErr: `ParseAddr("::ffff:1.2.03.4"): ParseAddr("1.2.03.4"): IPv4 field has octet with leading zero (at "1.2.03.4")`,
+		},
+		// Basic zero IPv6 address.
+		{
+			in: "::",
+			ip: MkAddr(Mk128(0, 0), Z6noz),
+		},
+		// Localhost IPv6.
+		{
+			in: "::1",
+			ip: MkAddr(Mk128(0, 1), Z6noz),
+		},
+		// Fully expanded IPv6 address.
+		{
+			in: "fd7a:115c:a1e0:ab12:4843:cd96:626b:430b",
+			ip: MkAddr(Mk128(0xfd7a115ca1e0ab12, 0x4843cd96626b430b), Z6noz),
+		},
+		// IPv6 with elided fields in the middle.
+		{
+			in: "fd7a:115c::626b:430b",
+			ip: MkAddr(Mk128(0xfd7a115c00000000, 0x00000000626b430b), Z6noz),
+		},
+		// IPv6 with elided fields at the end.
+		{
+			in: "fd7a:115c:a1e0:ab12:4843:cd96::",
+			ip: MkAddr(Mk128(0xfd7a115ca1e0ab12, 0x4843cd9600000000), Z6noz),
+		},
+		// IPv6 with single elided field at the end.
+		{
+			in:  "fd7a:115c:a1e0:ab12:4843:cd96:626b::",
+			ip:  MkAddr(Mk128(0xfd7a115ca1e0ab12, 0x4843cd96626b0000), Z6noz),
+			str: "fd7a:115c:a1e0:ab12:4843:cd96:626b:0",
+		},
+		// IPv6 with single elided field in the middle.
+		{
+			in:  "fd7a:115c:a1e0::4843:cd96:626b:430b",
+			ip:  MkAddr(Mk128(0xfd7a115ca1e00000, 0x4843cd96626b430b), Z6noz),
+			str: "fd7a:115c:a1e0:0:4843:cd96:626b:430b",
+		},
+		// IPv6 with the trailing 32 bits written as IPv4 dotted decimal. (4in6)
+		{
+			in:  "::ffff:192.168.140.255",
+			ip:  MkAddr(Mk128(0, 0x0000ffffc0a88cff), Z6noz),
+			str: "::ffff:192.168.140.255",
+		},
+		// IPv6 with a zone specifier.
+		{
+			in: "fd7a:115c:a1e0:ab12:4843:cd96:626b:430b%eth0",
+			ip: MkAddr(Mk128(0xfd7a115ca1e0ab12, 0x4843cd96626b430b), intern.Get("eth0")),
+		},
+		// IPv6 with dotted decimal and zone specifier.
+		{
+			in:  "1:2::ffff:192.168.140.255%eth1",
+			ip:  MkAddr(Mk128(0x0001000200000000, 0x0000ffffc0a88cff), intern.Get("eth1")),
+			str: "1:2::ffff:c0a8:8cff%eth1",
+		},
+		// 4-in-6 with zone
+		{
+			in:  "::ffff:192.168.140.255%eth1",
+			ip:  MkAddr(Mk128(0, 0x0000ffffc0a88cff), intern.Get("eth1")),
+			str: "::ffff:192.168.140.255%eth1",
+		},
+		// IPv6 with capital letters.
+		{
+			in:  "FD9E:1A04:F01D::1",
+			ip:  MkAddr(Mk128(0xfd9e1a04f01d0000, 0x1), Z6noz),
+			str: "fd9e:1a04:f01d::1",
+		},
+	}
+
+	for _, test := range validIPs {
+		t.Run(test.in, func(t *testing.T) {
+			got, err := ParseAddr(test.in)
+			if err != nil {
+				if err.Error() == test.wantErr {
+					return
+				}
+				t.Fatal(err)
+			}
+			if test.wantErr != "" {
+				t.Fatalf("wanted error %q; got none", test.wantErr)
+			}
+			if got != test.ip {
+				t.Errorf("got %#v, want %#v", got, test.ip)
+			}
+
+			// Check that ParseAddr is a pure function.
+			got2, err := ParseAddr(test.in)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if got != got2 {
+				t.Errorf("ParseAddr(%q) got 2 different results: %#v, %#v", test.in, got, got2)
+			}
+
+			// Check that ParseAddr(ip.String()) is the identity function.
+			s := got.String()
+			got3, err := ParseAddr(s)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if got != got3 {
+				t.Errorf("ParseAddr(%q) != ParseAddr(ParseIP(%q).String()). Got %#v, want %#v", test.in, test.in, got3, got)
+			}
+
+			// Check that the slow-but-readable parser produces the same result.
+			slow, err := parseIPSlow(test.in)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if got != slow {
+				t.Errorf("ParseAddr(%q) = %#v, parseIPSlow(%q) = %#v", test.in, got, test.in, slow)
+			}
+
+			// Check that the parsed IP formats as expected.
+			s = got.String()
+			wants := test.str
+			if wants == "" {
+				wants = test.in
+			}
+			if s != wants {
+				t.Errorf("ParseAddr(%q).String() got %q, want %q", test.in, s, wants)
+			}
+
+			// Check that AppendTo matches MarshalText.
+			TestAppendToMarshal(t, got)
+
+			// Check that MarshalText/UnmarshalText work similarly to
+			// ParseAddr/String (see TestIPMarshalUnmarshal for
+			// marshal-specific behavior that's not common with
+			// ParseAddr/String).
+			js := `"` + test.in + `"`
+			var jsgot Addr
+			if err := json.Unmarshal([]byte(js), &jsgot); err != nil {
+				t.Fatal(err)
+			}
+			if jsgot != got {
+				t.Errorf("json.Unmarshal(%q) = %#v, want %#v", test.in, jsgot, got)
+			}
+			jsb, err := json.Marshal(jsgot)
+			if err != nil {
+				t.Fatal(err)
+			}
+			jswant := `"` + wants + `"`
+			jsback := string(jsb)
+			if jsback != jswant {
+				t.Errorf("Marshal(Unmarshal(%q)) = %s, want %s", test.in, jsback, jswant)
+			}
+		})
+	}
+
+	var invalidIPs = []string{
+		// Empty string
+		"",
+		// Garbage non-IP
+		"bad",
+		// Single number. Some parsers accept this as an IPv4 address in
+		// big-endian uint32 form, but we don't.
+		"1234",
+		// IPv4 with a zone specifier
+		"1.2.3.4%eth0",
+		// IPv4 field must have at least one digit
+		".1.2.3",
+		"1.2.3.",
+		"1..2.3",
+		// IPv4 address too long
+		"1.2.3.4.5",
+		// IPv4 in dotted octal form
+		"0300.0250.0214.0377",
+		// IPv4 in dotted hex form
+		"0xc0.0xa8.0x8c.0xff",
+		// IPv4 in class B form
+		"192.168.12345",
+		// IPv4 in class B form, with a small enough number to be
+		// parseable as a regular dotted decimal field.
+		"127.0.1",
+		// IPv4 in class A form
+		"192.1234567",
+		// IPv4 in class A form, with a small enough number to be
+		// parseable as a regular dotted decimal field.
+		"127.1",
+		// IPv4 field has value >255
+		"192.168.300.1",
+		// IPv4 with too many fields
+		"192.168.0.1.5.6",
+		// IPv6 with not enough fields
+		"1:2:3:4:5:6:7",
+		// IPv6 with too many fields
+		"1:2:3:4:5:6:7:8:9",
+		// IPv6 with 8 fields and a :: expander
+		"1:2:3:4::5:6:7:8",
+		// IPv6 with a field bigger than 2b
+		"fe801::1",
+		// IPv6 with non-hex values in field
+		"fe80:tail:scal:e::",
+		// IPv6 with a zone delimiter but no zone.
+		"fe80::1%",
+		// IPv6 (without ellipsis) with too many fields for trailing embedded IPv4.
+		"ffff:ffff:ffff:ffff:ffff:ffff:ffff:192.168.140.255",
+		// IPv6 (with ellipsis) with too many fields for trailing embedded IPv4.
+		"ffff::ffff:ffff:ffff:ffff:ffff:ffff:192.168.140.255",
+		// IPv6 with invalid embedded IPv4.
+		"::ffff:192.168.140.bad",
+		// IPv6 with multiple ellipsis ::.
+		"fe80::1::1",
+		// IPv6 with invalid non hex/colon character.
+		"fe80:1?:1",
+		// IPv6 with truncated bytes after single colon.
+		"fe80:",
+	}
+
+	for _, s := range invalidIPs {
+		t.Run(s, func(t *testing.T) {
+			got, err := ParseAddr(s)
+			if err == nil {
+				t.Errorf("ParseAddr(%q) = %#v, want error", s, got)
+			}
+
+			slow, err := parseIPSlow(s)
+			if err == nil {
+				t.Errorf("parseIPSlow(%q) = %#v, want error", s, slow)
+			}
+
+			std := net.ParseIP(s)
+			if std != nil {
+				t.Errorf("net.ParseIP(%q) = %#v, want error", s, std)
+			}
+
+			if s == "" {
+				// Don't test unmarshaling of "" here, do it in
+				// IPMarshalUnmarshal.
+				return
+			}
+			var jsgot Addr
+			js := []byte(`"` + s + `"`)
+			if err := json.Unmarshal(js, &jsgot); err == nil {
+				t.Errorf("json.Unmarshal(%q) = %#v, want error", s, jsgot)
+			}
+		})
+	}
+}
+
+func TestIPv4Constructors(t *testing.T) {
+	if AddrFrom4([4]byte{1, 2, 3, 4}) != MustParseAddr("1.2.3.4") {
+		t.Errorf("don't match")
+	}
+}
+
+func TestAddrMarshalUnmarshalBinary(t *testing.T) {
+	tests := []struct {
+		ip       string
+		wantSize int
+	}{
+		{"", 0}, // zero IP
+		{"1.2.3.4", 4},
+		{"fd7a:115c:a1e0:ab12:4843:cd96:626b:430b", 16},
+		{"::ffff:c000:0280", 16},
+		{"::ffff:c000:0280%eth0", 20},
+	}
+	for _, tc := range tests {
+		var ip Addr
+		if len(tc.ip) > 0 {
+			ip = mustIP(tc.ip)
+		}
+		b, err := ip.MarshalBinary()
+		if err != nil {
+			t.Fatal(err)
+		}
+		if len(b) != tc.wantSize {
+			t.Fatalf("%q encoded to size %d; want %d", tc.ip, len(b), tc.wantSize)
+		}
+		var ip2 Addr
+		if err := ip2.UnmarshalBinary(b); err != nil {
+			t.Fatal(err)
+		}
+		if ip != ip2 {
+			t.Fatalf("got %v; want %v", ip2, ip)
+		}
+	}
+
+	// Cannot unmarshal from unexpected IP length.
+	for _, n := range []int{3, 5} {
+		var ip2 Addr
+		if err := ip2.UnmarshalBinary(bytes.Repeat([]byte{1}, n)); err == nil {
+			t.Fatalf("unmarshaled from unexpected IP length %d", n)
+		}
+	}
+}
+
+func TestAddrPortMarshalTextString(t *testing.T) {
+	tests := []struct {
+		in   AddrPort
+		want string
+	}{
+		{mustIPPort("1.2.3.4:80"), "1.2.3.4:80"},
+		{mustIPPort("[1::CAFE]:80"), "[1::cafe]:80"},
+		{mustIPPort("[1::CAFE%en0]:80"), "[1::cafe%en0]:80"},
+		{mustIPPort("[::FFFF:192.168.140.255]:80"), "[::ffff:192.168.140.255]:80"},
+		{mustIPPort("[::FFFF:192.168.140.255%en0]:80"), "[::ffff:192.168.140.255%en0]:80"},
+	}
+	for i, tt := range tests {
+		if got := tt.in.String(); got != tt.want {
+			t.Errorf("%d. for (%v, %v) String = %q; want %q", i, tt.in.Addr(), tt.in.Port(), got, tt.want)
+		}
+		mt, err := tt.in.MarshalText()
+		if err != nil {
+			t.Errorf("%d. for (%v, %v) MarshalText error: %v", i, tt.in.Addr(), tt.in.Port(), err)
+			continue
+		}
+		if string(mt) != tt.want {
+			t.Errorf("%d. for (%v, %v) MarshalText = %q; want %q", i, tt.in.Addr(), tt.in.Port(), mt, tt.want)
+		}
+	}
+}
+
+func TestAddrPortMarshalUnmarshalBinary(t *testing.T) {
+	tests := []struct {
+		ipport   string
+		wantSize int
+	}{
+		{"1.2.3.4:51820", 4 + 2},
+		{"[fd7a:115c:a1e0:ab12:4843:cd96:626b:430b]:80", 16 + 2},
+		{"[::ffff:c000:0280]:65535", 16 + 2},
+		{"[::ffff:c000:0280%eth0]:1", 20 + 2},
+	}
+	for _, tc := range tests {
+		var ipport AddrPort
+		if len(tc.ipport) > 0 {
+			ipport = mustIPPort(tc.ipport)
+		}
+		b, err := ipport.MarshalBinary()
+		if err != nil {
+			t.Fatal(err)
+		}
+		if len(b) != tc.wantSize {
+			t.Fatalf("%q encoded to size %d; want %d", tc.ipport, len(b), tc.wantSize)
+		}
+		var ipport2 AddrPort
+		if err := ipport2.UnmarshalBinary(b); err != nil {
+			t.Fatal(err)
+		}
+		if ipport != ipport2 {
+			t.Fatalf("got %v; want %v", ipport2, ipport)
+		}
+	}
+
+	// Cannot unmarshal from unexpected lengths.
+	for _, n := range []int{3, 7} {
+		var ipport2 AddrPort
+		if err := ipport2.UnmarshalBinary(bytes.Repeat([]byte{1}, n)); err == nil {
+			t.Fatalf("unmarshaled from unexpected length %d", n)
+		}
+	}
+}
+
+func TestPrefixMarshalTextString(t *testing.T) {
+	tests := []struct {
+		in   Prefix
+		want string
+	}{
+		{mustPrefix("1.2.3.4/24"), "1.2.3.4/24"},
+		{mustPrefix("fd7a:115c:a1e0:ab12:4843:cd96:626b:430b/118"), "fd7a:115c:a1e0:ab12:4843:cd96:626b:430b/118"},
+		{mustPrefix("::ffff:c000:0280/96"), "::ffff:192.0.2.128/96"},
+		{mustPrefix("::ffff:c000:0280%eth0/37"), "::ffff:192.0.2.128/37"}, // Zone should be stripped
+		{mustPrefix("::ffff:192.168.140.255/8"), "::ffff:192.168.140.255/8"},
+	}
+	for i, tt := range tests {
+		if got := tt.in.String(); got != tt.want {
+			t.Errorf("%d. for %v String = %q; want %q", i, tt.in, got, tt.want)
+		}
+		mt, err := tt.in.MarshalText()
+		if err != nil {
+			t.Errorf("%d. for %v MarshalText error: %v", i, tt.in, err)
+			continue
+		}
+		if string(mt) != tt.want {
+			t.Errorf("%d. for %v MarshalText = %q; want %q", i, tt.in, mt, tt.want)
+		}
+	}
+}
+
+func TestPrefixMarshalUnmarshalBinary(t *testing.T) {
+	type testCase struct {
+		prefix   Prefix
+		wantSize int
+	}
+	tests := []testCase{
+		{mustPrefix("1.2.3.4/24"), 4 + 1},
+		{mustPrefix("fd7a:115c:a1e0:ab12:4843:cd96:626b:430b/118"), 16 + 1},
+		{mustPrefix("::ffff:c000:0280/96"), 16 + 1},
+		{mustPrefix("::ffff:c000:0280%eth0/37"), 16 + 1}, // Zone should be stripped
+	}
+	tests = append(tests,
+		testCase{PrefixFrom(tests[0].prefix.Addr(), 33), tests[0].wantSize},
+		testCase{PrefixFrom(tests[1].prefix.Addr(), 129), tests[1].wantSize})
+	for _, tc := range tests {
+		prefix := tc.prefix
+		b, err := prefix.MarshalBinary()
+		if err != nil {
+			t.Fatal(err)
+		}
+		if len(b) != tc.wantSize {
+			t.Fatalf("%q encoded to size %d; want %d", tc.prefix, len(b), tc.wantSize)
+		}
+		var prefix2 Prefix
+		if err := prefix2.UnmarshalBinary(b); err != nil {
+			t.Fatal(err)
+		}
+		if prefix != prefix2 {
+			t.Fatalf("got %v; want %v", prefix2, prefix)
+		}
+	}
+
+	// Cannot unmarshal from unexpected lengths.
+	for _, n := range []int{3, 6} {
+		var prefix2 Prefix
+		if err := prefix2.UnmarshalBinary(bytes.Repeat([]byte{1}, n)); err == nil {
+			t.Fatalf("unmarshaled from unexpected length %d", n)
+		}
+	}
+}
+
+func TestAddrMarshalUnmarshal(t *testing.T) {
+	// This only tests the cases where Marshal/Unmarshal diverges from
+	// the behavior of ParseAddr/String. For the rest of the test cases,
+	// see TestParseAddr above.
+	orig := `""`
+	var ip Addr
+	if err := json.Unmarshal([]byte(orig), &ip); err != nil {
+		t.Fatalf("Unmarshal(%q) got error %v", orig, err)
+	}
+	if ip != (Addr{}) {
+		t.Errorf("Unmarshal(%q) is not the zero Addr", orig)
+	}
+
+	jsb, err := json.Marshal(ip)
+	if err != nil {
+		t.Fatalf("Marshal(%v) got error %v", ip, err)
+	}
+	back := string(jsb)
+	if back != orig {
+		t.Errorf("Marshal(Unmarshal(%q)) got %q, want %q", orig, back, orig)
+	}
+}
+
+func TestAddrFrom16(t *testing.T) {
+	tests := []struct {
+		name string
+		in   [16]byte
+		want Addr
+	}{
+		{
+			name: "v6-raw",
+			in:   [...]byte{15: 1},
+			want: MkAddr(Mk128(0, 1), Z6noz),
+		},
+		{
+			name: "v4-raw",
+			in:   [...]byte{10: 0xff, 11: 0xff, 12: 1, 13: 2, 14: 3, 15: 4},
+			want: MkAddr(Mk128(0, 0xffff01020304), Z6noz),
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := AddrFrom16(tt.in)
+			if got != tt.want {
+				t.Errorf("got %#v; want %#v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestIPProperties(t *testing.T) {
+	var (
+		nilIP Addr
+
+		unicast4           = mustIP("192.0.2.1")
+		unicast6           = mustIP("2001:db8::1")
+		unicastZone6       = mustIP("2001:db8::1%eth0")
+		unicast6Unassigned = mustIP("4000::1") // not in 2000::/3.
+
+		multicast4     = mustIP("224.0.0.1")
+		multicast6     = mustIP("ff02::1")
+		multicastZone6 = mustIP("ff02::1%eth0")
+
+		llu4     = mustIP("169.254.0.1")
+		llu6     = mustIP("fe80::1")
+		llu6Last = mustIP("febf:ffff:ffff:ffff:ffff:ffff:ffff:ffff")
+		lluZone6 = mustIP("fe80::1%eth0")
+
+		loopback4 = mustIP("127.0.0.1")
+		loopback6 = mustIP("::1")
+
+		ilm6     = mustIP("ff01::1")
+		ilmZone6 = mustIP("ff01::1%eth0")
+
+		private4a = mustIP("10.0.0.1")
+		private4b = mustIP("172.16.0.1")
+		private4c = mustIP("192.168.1.1")
+		private6  = mustIP("fd00::1")
+
+		unspecified4 = AddrFrom4([4]byte{})
+		unspecified6 = IPv6Unspecified()
+	)
+
+	tests := []struct {
+		name                    string
+		ip                      Addr
+		globalUnicast           bool
+		interfaceLocalMulticast bool
+		linkLocalMulticast      bool
+		linkLocalUnicast        bool
+		loopback                bool
+		multicast               bool
+		private                 bool
+		unspecified             bool
+	}{
+		{
+			name: "nil",
+			ip:   nilIP,
+		},
+		{
+			name:          "unicast v4Addr",
+			ip:            unicast4,
+			globalUnicast: true,
+		},
+		{
+			name:          "unicast v6Addr",
+			ip:            unicast6,
+			globalUnicast: true,
+		},
+		{
+			name:          "unicast v6AddrZone",
+			ip:            unicastZone6,
+			globalUnicast: true,
+		},
+		{
+			name:          "unicast v6Addr unassigned",
+			ip:            unicast6Unassigned,
+			globalUnicast: true,
+		},
+		{
+			name:               "multicast v4Addr",
+			ip:                 multicast4,
+			linkLocalMulticast: true,
+			multicast:          true,
+		},
+		{
+			name:               "multicast v6Addr",
+			ip:                 multicast6,
+			linkLocalMulticast: true,
+			multicast:          true,
+		},
+		{
+			name:               "multicast v6AddrZone",
+			ip:                 multicastZone6,
+			linkLocalMulticast: true,
+			multicast:          true,
+		},
+		{
+			name:             "link-local unicast v4Addr",
+			ip:               llu4,
+			linkLocalUnicast: true,
+		},
+		{
+			name:             "link-local unicast v6Addr",
+			ip:               llu6,
+			linkLocalUnicast: true,
+		},
+		{
+			name:             "link-local unicast v6Addr upper bound",
+			ip:               llu6Last,
+			linkLocalUnicast: true,
+		},
+		{
+			name:             "link-local unicast v6AddrZone",
+			ip:               lluZone6,
+			linkLocalUnicast: true,
+		},
+		{
+			name:     "loopback v4Addr",
+			ip:       loopback4,
+			loopback: true,
+		},
+		{
+			name:     "loopback v6Addr",
+			ip:       loopback6,
+			loopback: true,
+		},
+		{
+			name:                    "interface-local multicast v6Addr",
+			ip:                      ilm6,
+			interfaceLocalMulticast: true,
+			multicast:               true,
+		},
+		{
+			name:                    "interface-local multicast v6AddrZone",
+			ip:                      ilmZone6,
+			interfaceLocalMulticast: true,
+			multicast:               true,
+		},
+		{
+			name:          "private v4Addr 10/8",
+			ip:            private4a,
+			globalUnicast: true,
+			private:       true,
+		},
+		{
+			name:          "private v4Addr 172.16/12",
+			ip:            private4b,
+			globalUnicast: true,
+			private:       true,
+		},
+		{
+			name:          "private v4Addr 192.168/16",
+			ip:            private4c,
+			globalUnicast: true,
+			private:       true,
+		},
+		{
+			name:          "private v6Addr",
+			ip:            private6,
+			globalUnicast: true,
+			private:       true,
+		},
+		{
+			name:        "unspecified v4Addr",
+			ip:          unspecified4,
+			unspecified: true,
+		},
+		{
+			name:        "unspecified v6Addr",
+			ip:          unspecified6,
+			unspecified: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			gu := tt.ip.IsGlobalUnicast()
+			if gu != tt.globalUnicast {
+				t.Errorf("IsGlobalUnicast(%v) = %v; want %v", tt.ip, gu, tt.globalUnicast)
+			}
+
+			ilm := tt.ip.IsInterfaceLocalMulticast()
+			if ilm != tt.interfaceLocalMulticast {
+				t.Errorf("IsInterfaceLocalMulticast(%v) = %v; want %v", tt.ip, ilm, tt.interfaceLocalMulticast)
+			}
+
+			llu := tt.ip.IsLinkLocalUnicast()
+			if llu != tt.linkLocalUnicast {
+				t.Errorf("IsLinkLocalUnicast(%v) = %v; want %v", tt.ip, llu, tt.linkLocalUnicast)
+			}
+
+			llm := tt.ip.IsLinkLocalMulticast()
+			if llm != tt.linkLocalMulticast {
+				t.Errorf("IsLinkLocalMulticast(%v) = %v; want %v", tt.ip, llm, tt.linkLocalMulticast)
+			}
+
+			lo := tt.ip.IsLoopback()
+			if lo != tt.loopback {
+				t.Errorf("IsLoopback(%v) = %v; want %v", tt.ip, lo, tt.loopback)
+			}
+
+			multicast := tt.ip.IsMulticast()
+			if multicast != tt.multicast {
+				t.Errorf("IsMulticast(%v) = %v; want %v", tt.ip, multicast, tt.multicast)
+			}
+
+			private := tt.ip.IsPrivate()
+			if private != tt.private {
+				t.Errorf("IsPrivate(%v) = %v; want %v", tt.ip, private, tt.private)
+			}
+
+			unspecified := tt.ip.IsUnspecified()
+			if unspecified != tt.unspecified {
+				t.Errorf("IsUnspecified(%v) = %v; want %v", tt.ip, unspecified, tt.unspecified)
+			}
+		})
+	}
+}
+
+func TestAddrWellKnown(t *testing.T) {
+	tests := []struct {
+		name string
+		ip   Addr
+		std  net.IP
+	}{
+		{
+			name: "IPv6 link-local all nodes",
+			ip:   IPv6LinkLocalAllNodes(),
+			std:  net.IPv6linklocalallnodes,
+		},
+		{
+			name: "IPv6 unspecified",
+			ip:   IPv6Unspecified(),
+			std:  net.IPv6unspecified,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			want := tt.std.String()
+			got := tt.ip.String()
+
+			if got != want {
+				t.Fatalf("got %s, want %s", got, want)
+			}
+		})
+	}
+}
+
+func TestLessCompare(t *testing.T) {
+	tests := []struct {
+		a, b Addr
+		want bool
+	}{
+		{Addr{}, Addr{}, false},
+		{Addr{}, mustIP("1.2.3.4"), true},
+		{mustIP("1.2.3.4"), Addr{}, false},
+
+		{mustIP("1.2.3.4"), mustIP("0102:0304::0"), true},
+		{mustIP("0102:0304::0"), mustIP("1.2.3.4"), false},
+		{mustIP("1.2.3.4"), mustIP("1.2.3.4"), false},
+
+		{mustIP("::1"), mustIP("::2"), true},
+		{mustIP("::1"), mustIP("::1%foo"), true},
+		{mustIP("::1%foo"), mustIP("::2"), true},
+		{mustIP("::2"), mustIP("::3"), true},
+
+		{mustIP("::"), mustIP("0.0.0.0"), false},
+		{mustIP("0.0.0.0"), mustIP("::"), true},
+
+		{mustIP("::1%a"), mustIP("::1%b"), true},
+		{mustIP("::1%a"), mustIP("::1%a"), false},
+		{mustIP("::1%b"), mustIP("::1%a"), false},
+	}
+	for _, tt := range tests {
+		got := tt.a.Less(tt.b)
+		if got != tt.want {
+			t.Errorf("Less(%q, %q) = %v; want %v", tt.a, tt.b, got, tt.want)
+		}
+		cmp := tt.a.Compare(tt.b)
+		if got && cmp != -1 {
+			t.Errorf("Less(%q, %q) = true, but Compare = %v (not -1)", tt.a, tt.b, cmp)
+		}
+		if cmp < -1 || cmp > 1 {
+			t.Errorf("bogus Compare return value %v", cmp)
+		}
+		if cmp == 0 && tt.a != tt.b {
+			t.Errorf("Compare(%q, %q) = 0; but not equal", tt.a, tt.b)
+		}
+		if cmp == 1 && !tt.b.Less(tt.a) {
+			t.Errorf("Compare(%q, %q) = 1; but b.Less(a) isn't true", tt.a, tt.b)
+		}
+
+		// Also check inverse.
+		if got == tt.want && got {
+			got2 := tt.b.Less(tt.a)
+			if got2 {
+				t.Errorf("Less(%q, %q) was correctly %v, but so was Less(%q, %q)", tt.a, tt.b, got, tt.b, tt.a)
+			}
+		}
+	}
+
+	// And just sort.
+	values := []Addr{
+		mustIP("::1"),
+		mustIP("::2"),
+		Addr{},
+		mustIP("1.2.3.4"),
+		mustIP("8.8.8.8"),
+		mustIP("::1%foo"),
+	}
+	sort.Slice(values, func(i, j int) bool { return values[i].Less(values[j]) })
+	got := fmt.Sprintf("%s", values)
+	want := `[invalid IP 1.2.3.4 8.8.8.8 ::1 ::1%foo ::2]`
+	if got != want {
+		t.Errorf("unexpected sort\n got: %s\nwant: %s\n", got, want)
+	}
+}
+
+func TestIPStringExpanded(t *testing.T) {
+	tests := []struct {
+		ip Addr
+		s  string
+	}{
+		{
+			ip: Addr{},
+			s:  "invalid IP",
+		},
+		{
+			ip: mustIP("192.0.2.1"),
+			s:  "192.0.2.1",
+		},
+		{
+			ip: mustIP("::ffff:192.0.2.1"),
+			s:  "0000:0000:0000:0000:0000:ffff:c000:0201",
+		},
+		{
+			ip: mustIP("2001:db8::1"),
+			s:  "2001:0db8:0000:0000:0000:0000:0000:0001",
+		},
+		{
+			ip: mustIP("2001:db8::1%eth0"),
+			s:  "2001:0db8:0000:0000:0000:0000:0000:0001%eth0",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.ip.String(), func(t *testing.T) {
+			want := tt.s
+			got := tt.ip.StringExpanded()
+
+			if got != want {
+				t.Fatalf("got %s, want %s", got, want)
+			}
+		})
+	}
+}
+
+func TestPrefixMasking(t *testing.T) {
+	type subtest struct {
+		ip   Addr
+		bits uint8
+		p    Prefix
+		ok   bool
+	}
+
+	// makeIPv6 produces a set of IPv6 subtests with an optional zone identifier.
+	makeIPv6 := func(zone string) []subtest {
+		if zone != "" {
+			zone = "%" + zone
+		}
+
+		return []subtest{
+			{
+				ip:   mustIP(fmt.Sprintf("2001:db8::1%s", zone)),
+				bits: 255,
+			},
+			{
+				ip:   mustIP(fmt.Sprintf("2001:db8::1%s", zone)),
+				bits: 32,
+				p:    mustPrefix(fmt.Sprintf("2001:db8::%s/32", zone)),
+				ok:   true,
+			},
+			{
+				ip:   mustIP(fmt.Sprintf("fe80::dead:beef:dead:beef%s", zone)),
+				bits: 96,
+				p:    mustPrefix(fmt.Sprintf("fe80::dead:beef:0:0%s/96", zone)),
+				ok:   true,
+			},
+			{
+				ip:   mustIP(fmt.Sprintf("aaaa::%s", zone)),
+				bits: 4,
+				p:    mustPrefix(fmt.Sprintf("a000::%s/4", zone)),
+				ok:   true,
+			},
+			{
+				ip:   mustIP(fmt.Sprintf("::%s", zone)),
+				bits: 63,
+				p:    mustPrefix(fmt.Sprintf("::%s/63", zone)),
+				ok:   true,
+			},
+		}
+	}
+
+	tests := []struct {
+		family   string
+		subtests []subtest
+	}{
+		{
+			family: "nil",
+			subtests: []subtest{
+				{
+					bits: 255,
+					ok:   true,
+				},
+				{
+					bits: 16,
+					ok:   true,
+				},
+			},
+		},
+		{
+			family: "IPv4",
+			subtests: []subtest{
+				{
+					ip:   mustIP("192.0.2.0"),
+					bits: 255,
+				},
+				{
+					ip:   mustIP("192.0.2.0"),
+					bits: 16,
+					p:    mustPrefix("192.0.0.0/16"),
+					ok:   true,
+				},
+				{
+					ip:   mustIP("255.255.255.255"),
+					bits: 20,
+					p:    mustPrefix("255.255.240.0/20"),
+					ok:   true,
+				},
+				{
+					// Partially masking one byte that contains both
+					// 1s and 0s on either side of the mask limit.
+					ip:   mustIP("100.98.156.66"),
+					bits: 10,
+					p:    mustPrefix("100.64.0.0/10"),
+					ok:   true,
+				},
+			},
+		},
+		{
+			family:   "IPv6",
+			subtests: makeIPv6(""),
+		},
+		{
+			family:   "IPv6 zone",
+			subtests: makeIPv6("eth0"),
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.family, func(t *testing.T) {
+			for _, st := range tt.subtests {
+				t.Run(st.p.String(), func(t *testing.T) {
+					// Ensure st.ip is not mutated.
+					orig := st.ip.String()
+
+					p, err := st.ip.Prefix(int(st.bits))
+					if st.ok && err != nil {
+						t.Fatalf("failed to produce prefix: %v", err)
+					}
+					if !st.ok && err == nil {
+						t.Fatal("expected an error, but none occurred")
+					}
+					if err != nil {
+						t.Logf("err: %v", err)
+						return
+					}
+
+					if !reflect.DeepEqual(p, st.p) {
+						t.Errorf("prefix = %q, want %q", p, st.p)
+					}
+
+					if got := st.ip.String(); got != orig {
+						t.Errorf("IP was mutated: %q, want %q", got, orig)
+					}
+				})
+			}
+		})
+	}
+}
+
+func TestPrefixMarshalUnmarshal(t *testing.T) {
+	tests := []string{
+		"",
+		"1.2.3.4/32",
+		"0.0.0.0/0",
+		"::/0",
+		"::1/128",
+		"2001:db8::/32",
+	}
+
+	for _, s := range tests {
+		t.Run(s, func(t *testing.T) {
+			// Ensure that JSON  (and by extension, text) marshaling is
+			// sane by entering quoted input.
+			orig := `"` + s + `"`
+
+			var p Prefix
+			if err := json.Unmarshal([]byte(orig), &p); err != nil {
+				t.Fatalf("failed to unmarshal: %v", err)
+			}
+
+			pb, err := json.Marshal(p)
+			if err != nil {
+				t.Fatalf("failed to marshal: %v", err)
+			}
+
+			back := string(pb)
+			if orig != back {
+				t.Errorf("Marshal = %q; want %q", back, orig)
+			}
+		})
+	}
+}
+
+func TestPrefixMarshalUnmarshalZone(t *testing.T) {
+	orig := `"fe80::1cc0:3e8c:119f:c2e1%ens18/128"`
+	unzoned := `"fe80::1cc0:3e8c:119f:c2e1/128"`
+
+	var p Prefix
+	if err := json.Unmarshal([]byte(orig), &p); err != nil {
+		t.Fatalf("failed to unmarshal: %v", err)
+	}
+
+	pb, err := json.Marshal(p)
+	if err != nil {
+		t.Fatalf("failed to marshal: %v", err)
+	}
+
+	back := string(pb)
+	if back != unzoned {
+		t.Errorf("Marshal = %q; want %q", back, unzoned)
+	}
+}
+
+func TestPrefixUnmarshalTextNonZero(t *testing.T) {
+	ip := mustPrefix("fe80::/64")
+	if err := ip.UnmarshalText([]byte("xxx")); err == nil {
+		t.Fatal("unmarshaled into non-empty Prefix")
+	}
+}
+
+func TestIs4AndIs6(t *testing.T) {
+	tests := []struct {
+		ip  Addr
+		is4 bool
+		is6 bool
+	}{
+		{Addr{}, false, false},
+		{mustIP("1.2.3.4"), true, false},
+		{mustIP("127.0.0.2"), true, false},
+		{mustIP("::1"), false, true},
+		{mustIP("::ffff:192.0.2.128"), false, true},
+		{mustIP("::fffe:c000:0280"), false, true},
+		{mustIP("::1%eth0"), false, true},
+	}
+	for _, tt := range tests {
+		got4 := tt.ip.Is4()
+		if got4 != tt.is4 {
+			t.Errorf("Is4(%q) = %v; want %v", tt.ip, got4, tt.is4)
+		}
+
+		got6 := tt.ip.Is6()
+		if got6 != tt.is6 {
+			t.Errorf("Is6(%q) = %v; want %v", tt.ip, got6, tt.is6)
+		}
+	}
+}
+
+func TestIs4In6(t *testing.T) {
+	tests := []struct {
+		ip        Addr
+		want      bool
+		wantUnmap Addr
+	}{
+		{Addr{}, false, Addr{}},
+		{mustIP("::ffff:c000:0280"), true, mustIP("192.0.2.128")},
+		{mustIP("::ffff:192.0.2.128"), true, mustIP("192.0.2.128")},
+		{mustIP("::ffff:192.0.2.128%eth0"), true, mustIP("192.0.2.128")},
+		{mustIP("::fffe:c000:0280"), false, mustIP("::fffe:c000:0280")},
+		{mustIP("::ffff:127.1.2.3"), true, mustIP("127.1.2.3")},
+		{mustIP("::ffff:7f01:0203"), true, mustIP("127.1.2.3")},
+		{mustIP("0:0:0:0:0000:ffff:127.1.2.3"), true, mustIP("127.1.2.3")},
+		{mustIP("0:0:0:0:000000:ffff:127.1.2.3"), true, mustIP("127.1.2.3")},
+		{mustIP("0:0:0:0::ffff:127.1.2.3"), true, mustIP("127.1.2.3")},
+		{mustIP("::1"), false, mustIP("::1")},
+		{mustIP("1.2.3.4"), false, mustIP("1.2.3.4")},
+	}
+	for _, tt := range tests {
+		got := tt.ip.Is4In6()
+		if got != tt.want {
+			t.Errorf("Is4In6(%q) = %v; want %v", tt.ip, got, tt.want)
+		}
+		u := tt.ip.Unmap()
+		if u != tt.wantUnmap {
+			t.Errorf("Unmap(%q) = %v; want %v", tt.ip, u, tt.wantUnmap)
+		}
+	}
+}
+
+func TestPrefixMasked(t *testing.T) {
+	tests := []struct {
+		prefix Prefix
+		masked Prefix
+	}{
+		{
+			prefix: mustPrefix("192.168.0.255/24"),
+			masked: mustPrefix("192.168.0.0/24"),
+		},
+		{
+			prefix: mustPrefix("2100::/3"),
+			masked: mustPrefix("2000::/3"),
+		},
+		{
+			prefix: PrefixFrom(mustIP("2000::"), 129),
+			masked: Prefix{},
+		},
+		{
+			prefix: PrefixFrom(mustIP("1.2.3.4"), 33),
+			masked: Prefix{},
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.prefix.String(), func(t *testing.T) {
+			got := test.prefix.Masked()
+			if got != test.masked {
+				t.Errorf("Masked=%s, want %s", got, test.masked)
+			}
+		})
+	}
+}
+
+func TestPrefix(t *testing.T) {
+	tests := []struct {
+		prefix      string
+		ip          Addr
+		bits        int
+		str         string
+		contains    []Addr
+		notContains []Addr
+	}{
+		{
+			prefix:      "192.168.0.0/24",
+			ip:          mustIP("192.168.0.0"),
+			bits:        24,
+			contains:    mustIPs("192.168.0.1", "192.168.0.55"),
+			notContains: mustIPs("192.168.1.1", "1.1.1.1"),
+		},
+		{
+			prefix:      "192.168.1.1/32",
+			ip:          mustIP("192.168.1.1"),
+			bits:        32,
+			contains:    mustIPs("192.168.1.1"),
+			notContains: mustIPs("192.168.1.2"),
+		},
+		{
+			prefix:      "100.64.0.0/10", // CGNAT range; prefix not multiple of 8
+			ip:          mustIP("100.64.0.0"),
+			bits:        10,
+			contains:    mustIPs("100.64.0.0", "100.64.0.1", "100.81.251.94", "100.100.100.100", "100.127.255.254", "100.127.255.255"),
+			notContains: mustIPs("100.63.255.255", "100.128.0.0"),
+		},
+		{
+			prefix:      "2001:db8::/96",
+			ip:          mustIP("2001:db8::"),
+			bits:        96,
+			contains:    mustIPs("2001:db8::aaaa:bbbb", "2001:db8::1"),
+			notContains: mustIPs("2001:db8::1:aaaa:bbbb", "2001:db9::"),
+		},
+		{
+			prefix:      "0.0.0.0/0",
+			ip:          mustIP("0.0.0.0"),
+			bits:        0,
+			contains:    mustIPs("192.168.0.1", "1.1.1.1"),
+			notContains: append(mustIPs("2001:db8::1"), Addr{}),
+		},
+		{
+			prefix:      "::/0",
+			ip:          mustIP("::"),
+			bits:        0,
+			contains:    mustIPs("::1", "2001:db8::1"),
+			notContains: mustIPs("192.0.2.1"),
+		},
+		{
+			prefix:      "2000::/3",
+			ip:          mustIP("2000::"),
+			bits:        3,
+			contains:    mustIPs("2001:db8::1"),
+			notContains: mustIPs("fe80::1"),
+		},
+		{
+			prefix:      "::%0/00/80",
+			ip:          mustIP("::"),
+			bits:        80,
+			str:         "::/80",
+			contains:    mustIPs("::"),
+			notContains: mustIPs("ff::%0/00", "ff::%1/23", "::%0/00", "::%1/23"),
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.prefix, func(t *testing.T) {
+			prefix, err := ParsePrefix(test.prefix)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if prefix.Addr() != test.ip {
+				t.Errorf("IP=%s, want %s", prefix.Addr(), test.ip)
+			}
+			if prefix.Bits() != test.bits {
+				t.Errorf("bits=%d, want %d", prefix.Bits(), test.bits)
+			}
+			for _, ip := range test.contains {
+				if !prefix.Contains(ip) {
+					t.Errorf("does not contain %s", ip)
+				}
+			}
+			for _, ip := range test.notContains {
+				if prefix.Contains(ip) {
+					t.Errorf("contains %s", ip)
+				}
+			}
+			want := test.str
+			if want == "" {
+				want = test.prefix
+			}
+			if got := prefix.String(); got != want {
+				t.Errorf("prefix.String()=%q, want %q", got, want)
+			}
+
+			TestAppendToMarshal(t, prefix)
+		})
+	}
+}
+
+func TestPrefixFromInvalidBits(t *testing.T) {
+	v4 := MustParseAddr("1.2.3.4")
+	v6 := MustParseAddr("66::66")
+	tests := []struct {
+		ip       Addr
+		in, want int
+	}{
+		{v4, 0, 0},
+		{v6, 0, 0},
+		{v4, 1, 1},
+		{v4, 33, -1},
+		{v6, 33, 33},
+		{v6, 127, 127},
+		{v6, 128, 128},
+		{v4, 254, -1},
+		{v4, 255, -1},
+		{v4, -1, -1},
+		{v6, -1, -1},
+		{v4, -5, -1},
+		{v6, -5, -1},
+	}
+	for _, tt := range tests {
+		p := PrefixFrom(tt.ip, tt.in)
+		if got := p.Bits(); got != tt.want {
+			t.Errorf("for (%v, %v), Bits out = %v; want %v", tt.ip, tt.in, got, tt.want)
+		}
+	}
+}
+
+func TestParsePrefixAllocs(t *testing.T) {
+	tests := []struct {
+		ip    string
+		slash string
+	}{
+		{"192.168.1.0", "/24"},
+		{"aaaa:bbbb:cccc::", "/24"},
+	}
+	for _, test := range tests {
+		prefix := test.ip + test.slash
+		t.Run(prefix, func(t *testing.T) {
+			ipAllocs := int(testing.AllocsPerRun(5, func() {
+				ParseAddr(test.ip)
+			}))
+			prefixAllocs := int(testing.AllocsPerRun(5, func() {
+				ParsePrefix(prefix)
+			}))
+			if got := prefixAllocs - ipAllocs; got != 0 {
+				t.Errorf("allocs=%d, want 0", got)
+			}
+		})
+	}
+}
+
+func TestParsePrefixError(t *testing.T) {
+	tests := []struct {
+		prefix string
+		errstr string
+	}{
+		{
+			prefix: "192.168.0.0",
+			errstr: "no '/'",
+		},
+		{
+			prefix: "1.257.1.1/24",
+			errstr: "value >255",
+		},
+		{
+			prefix: "1.1.1.0/q",
+			errstr: "bad bits",
+		},
+		{
+			prefix: "1.1.1.0/-1",
+			errstr: "out of range",
+		},
+		{
+			prefix: "1.1.1.0/33",
+			errstr: "out of range",
+		},
+		{
+			prefix: "2001::/129",
+			errstr: "out of range",
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.prefix, func(t *testing.T) {
+			_, err := ParsePrefix(test.prefix)
+			if err == nil {
+				t.Fatal("no error")
+			}
+			if got := err.Error(); !strings.Contains(got, test.errstr) {
+				t.Errorf("error is missing substring %q: %s", test.errstr, got)
+			}
+		})
+	}
+}
+
+func TestPrefixIsSingleIP(t *testing.T) {
+	tests := []struct {
+		ipp  Prefix
+		want bool
+	}{
+		{ipp: mustPrefix("127.0.0.1/32"), want: true},
+		{ipp: mustPrefix("127.0.0.1/31"), want: false},
+		{ipp: mustPrefix("127.0.0.1/0"), want: false},
+		{ipp: mustPrefix("::1/128"), want: true},
+		{ipp: mustPrefix("::1/127"), want: false},
+		{ipp: mustPrefix("::1/0"), want: false},
+		{ipp: Prefix{}, want: false},
+	}
+	for _, tt := range tests {
+		got := tt.ipp.IsSingleIP()
+		if got != tt.want {
+			t.Errorf("IsSingleIP(%v) = %v want %v", tt.ipp, got, tt.want)
+		}
+	}
+}
+
+func mustIPs(strs ...string) []Addr {
+	var res []Addr
+	for _, s := range strs {
+		res = append(res, mustIP(s))
+	}
+	return res
+}
+
+func BenchmarkBinaryMarshalRoundTrip(b *testing.B) {
+	b.ReportAllocs()
+	tests := []struct {
+		name string
+		ip   string
+	}{
+		{"ipv4", "1.2.3.4"},
+		{"ipv6", "2001:db8::1"},
+		{"ipv6+zone", "2001:db8::1%eth0"},
+	}
+	for _, tc := range tests {
+		b.Run(tc.name, func(b *testing.B) {
+			ip := mustIP(tc.ip)
+			for i := 0; i < b.N; i++ {
+				bt, err := ip.MarshalBinary()
+				if err != nil {
+					b.Fatal(err)
+				}
+				var ip2 Addr
+				if err := ip2.UnmarshalBinary(bt); err != nil {
+					b.Fatal(err)
+				}
+			}
+		})
+	}
+}
+
+func BenchmarkStdIPv4(b *testing.B) {
+	b.ReportAllocs()
+	ips := []net.IP{}
+	for i := 0; i < b.N; i++ {
+		ip := net.IPv4(8, 8, 8, 8)
+		ips = ips[:0]
+		for i := 0; i < 100; i++ {
+			ips = append(ips, ip)
+		}
+	}
+}
+
+func BenchmarkIPv4(b *testing.B) {
+	b.ReportAllocs()
+	ips := []Addr{}
+	for i := 0; i < b.N; i++ {
+		ip := IPv4(8, 8, 8, 8)
+		ips = ips[:0]
+		for i := 0; i < 100; i++ {
+			ips = append(ips, ip)
+		}
+	}
+}
+
+// ip4i was one of the possible representations of IP that came up in
+// discussions, inlining IPv4 addresses, but having an "overflow"
+// interface for IPv6 or IPv6 + zone. This is here for benchmarking.
+type ip4i struct {
+	ip4    [4]byte
+	flags1 byte
+	flags2 byte
+	flags3 byte
+	flags4 byte
+	ipv6   any
+}
+
+func newip4i_v4(a, b, c, d byte) ip4i {
+	return ip4i{ip4: [4]byte{a, b, c, d}}
+}
+
+// BenchmarkIPv4_inline benchmarks the candidate representation, ip4i.
+func BenchmarkIPv4_inline(b *testing.B) {
+	b.ReportAllocs()
+	ips := []ip4i{}
+	for i := 0; i < b.N; i++ {
+		ip := newip4i_v4(8, 8, 8, 8)
+		ips = ips[:0]
+		for i := 0; i < 100; i++ {
+			ips = append(ips, ip)
+		}
+	}
+}
+
+func BenchmarkStdIPv6(b *testing.B) {
+	b.ReportAllocs()
+	ips := []net.IP{}
+	for i := 0; i < b.N; i++ {
+		ip := net.ParseIP("2001:db8::1")
+		ips = ips[:0]
+		for i := 0; i < 100; i++ {
+			ips = append(ips, ip)
+		}
+	}
+}
+
+func BenchmarkIPv6(b *testing.B) {
+	b.ReportAllocs()
+	ips := []Addr{}
+	for i := 0; i < b.N; i++ {
+		ip := mustIP("2001:db8::1")
+		ips = ips[:0]
+		for i := 0; i < 100; i++ {
+			ips = append(ips, ip)
+		}
+	}
+}
+
+func BenchmarkIPv4Contains(b *testing.B) {
+	b.ReportAllocs()
+	prefix := PrefixFrom(IPv4(192, 168, 1, 0), 24)
+	ip := IPv4(192, 168, 1, 1)
+	for i := 0; i < b.N; i++ {
+		prefix.Contains(ip)
+	}
+}
+
+func BenchmarkIPv6Contains(b *testing.B) {
+	b.ReportAllocs()
+	prefix := MustParsePrefix("::1/128")
+	ip := MustParseAddr("::1")
+	for i := 0; i < b.N; i++ {
+		prefix.Contains(ip)
+	}
+}
+
+var parseBenchInputs = []struct {
+	name string
+	ip   string
+}{
+	{"v4", "192.168.1.1"},
+	{"v6", "fd7a:115c:a1e0:ab12:4843:cd96:626b:430b"},
+	{"v6_ellipsis", "fd7a:115c::626b:430b"},
+	{"v6_v4", "::ffff:192.168.140.255"},
+	{"v6_zone", "1:2::ffff:192.168.140.255%eth1"},
+}
+
+func BenchmarkParseAddr(b *testing.B) {
+	sinkInternValue = intern.Get("eth1") // Pin to not benchmark the intern package
+	for _, test := range parseBenchInputs {
+		b.Run(test.name, func(b *testing.B) {
+			b.ReportAllocs()
+			for i := 0; i < b.N; i++ {
+				sinkIP, _ = ParseAddr(test.ip)
+			}
+		})
+	}
+}
+
+func BenchmarkStdParseIP(b *testing.B) {
+	for _, test := range parseBenchInputs {
+		b.Run(test.name, func(b *testing.B) {
+			b.ReportAllocs()
+			for i := 0; i < b.N; i++ {
+				sinkStdIP = net.ParseIP(test.ip)
+			}
+		})
+	}
+}
+
+func BenchmarkIPString(b *testing.B) {
+	for _, test := range parseBenchInputs {
+		ip := MustParseAddr(test.ip)
+		b.Run(test.name, func(b *testing.B) {
+			b.ReportAllocs()
+			for i := 0; i < b.N; i++ {
+				sinkString = ip.String()
+			}
+		})
+	}
+}
+
+func BenchmarkIPStringExpanded(b *testing.B) {
+	for _, test := range parseBenchInputs {
+		ip := MustParseAddr(test.ip)
+		b.Run(test.name, func(b *testing.B) {
+			b.ReportAllocs()
+			for i := 0; i < b.N; i++ {
+				sinkString = ip.StringExpanded()
+			}
+		})
+	}
+}
+
+func BenchmarkIPMarshalText(b *testing.B) {
+	b.ReportAllocs()
+	ip := MustParseAddr("66.55.44.33")
+	for i := 0; i < b.N; i++ {
+		sinkBytes, _ = ip.MarshalText()
+	}
+}
+
+func BenchmarkAddrPortString(b *testing.B) {
+	for _, test := range parseBenchInputs {
+		ip := MustParseAddr(test.ip)
+		ipp := AddrPortFrom(ip, 60000)
+		b.Run(test.name, func(b *testing.B) {
+			b.ReportAllocs()
+			for i := 0; i < b.N; i++ {
+				sinkString = ipp.String()
+			}
+		})
+	}
+}
+
+func BenchmarkAddrPortMarshalText(b *testing.B) {
+	for _, test := range parseBenchInputs {
+		ip := MustParseAddr(test.ip)
+		ipp := AddrPortFrom(ip, 60000)
+		b.Run(test.name, func(b *testing.B) {
+			b.ReportAllocs()
+			for i := 0; i < b.N; i++ {
+				sinkBytes, _ = ipp.MarshalText()
+			}
+		})
+	}
+}
+
+func BenchmarkPrefixMasking(b *testing.B) {
+	tests := []struct {
+		name string
+		ip   Addr
+		bits int
+	}{
+		{
+			name: "IPv4 /32",
+			ip:   IPv4(192, 0, 2, 0),
+			bits: 32,
+		},
+		{
+			name: "IPv4 /17",
+			ip:   IPv4(192, 0, 2, 0),
+			bits: 17,
+		},
+		{
+			name: "IPv4 /0",
+			ip:   IPv4(192, 0, 2, 0),
+			bits: 0,
+		},
+		{
+			name: "IPv6 /128",
+			ip:   mustIP("2001:db8::1"),
+			bits: 128,
+		},
+		{
+			name: "IPv6 /65",
+			ip:   mustIP("2001:db8::1"),
+			bits: 65,
+		},
+		{
+			name: "IPv6 /0",
+			ip:   mustIP("2001:db8::1"),
+			bits: 0,
+		},
+		{
+			name: "IPv6 zone /128",
+			ip:   mustIP("2001:db8::1%eth0"),
+			bits: 128,
+		},
+		{
+			name: "IPv6 zone /65",
+			ip:   mustIP("2001:db8::1%eth0"),
+			bits: 65,
+		},
+		{
+			name: "IPv6 zone /0",
+			ip:   mustIP("2001:db8::1%eth0"),
+			bits: 0,
+		},
+	}
+
+	for _, tt := range tests {
+		b.Run(tt.name, func(b *testing.B) {
+			b.ReportAllocs()
+
+			for i := 0; i < b.N; i++ {
+				sinkPrefix, _ = tt.ip.Prefix(tt.bits)
+			}
+		})
+	}
+}
+
+func BenchmarkPrefixMarshalText(b *testing.B) {
+	b.ReportAllocs()
+	ipp := MustParsePrefix("66.55.44.33/22")
+	for i := 0; i < b.N; i++ {
+		sinkBytes, _ = ipp.MarshalText()
+	}
+}
+
+func BenchmarkParseAddrPort(b *testing.B) {
+	for _, test := range parseBenchInputs {
+		var ipp string
+		if strings.HasPrefix(test.name, "v6") {
+			ipp = fmt.Sprintf("[%s]:1234", test.ip)
+		} else {
+			ipp = fmt.Sprintf("%s:1234", test.ip)
+		}
+		b.Run(test.name, func(b *testing.B) {
+			b.ReportAllocs()
+
+			for i := 0; i < b.N; i++ {
+				sinkAddrPort, _ = ParseAddrPort(ipp)
+			}
+		})
+	}
+}
+
+func TestAs4(t *testing.T) {
+	tests := []struct {
+		ip        Addr
+		want      [4]byte
+		wantPanic bool
+	}{
+		{
+			ip:   mustIP("1.2.3.4"),
+			want: [4]byte{1, 2, 3, 4},
+		},
+		{
+			ip:   AddrFrom16(mustIP("1.2.3.4").As16()), // IPv4-in-IPv6
+			want: [4]byte{1, 2, 3, 4},
+		},
+		{
+			ip:   mustIP("0.0.0.0"),
+			want: [4]byte{0, 0, 0, 0},
+		},
+		{
+			ip:        Addr{},
+			wantPanic: true,
+		},
+		{
+			ip:        mustIP("::1"),
+			wantPanic: true,
+		},
+	}
+	as4 := func(ip Addr) (v [4]byte, gotPanic bool) {
+		defer func() {
+			if recover() != nil {
+				gotPanic = true
+				return
+			}
+		}()
+		v = ip.As4()
+		return
+	}
+	for i, tt := range tests {
+		got, gotPanic := as4(tt.ip)
+		if gotPanic != tt.wantPanic {
+			t.Errorf("%d. panic on %v = %v; want %v", i, tt.ip, gotPanic, tt.wantPanic)
+			continue
+		}
+		if got != tt.want {
+			t.Errorf("%d. %v = %v; want %v", i, tt.ip, got, tt.want)
+		}
+	}
+}
+
+func TestPrefixOverlaps(t *testing.T) {
+	pfx := mustPrefix
+	tests := []struct {
+		a, b Prefix
+		want bool
+	}{
+		{Prefix{}, pfx("1.2.0.0/16"), false},    // first zero
+		{pfx("1.2.0.0/16"), Prefix{}, false},    // second zero
+		{pfx("::0/3"), pfx("0.0.0.0/3"), false}, // different families
+
+		{pfx("1.2.0.0/16"), pfx("1.2.0.0/16"), true}, // equal
+
+		{pfx("1.2.0.0/16"), pfx("1.2.3.0/24"), true},
+		{pfx("1.2.3.0/24"), pfx("1.2.0.0/16"), true},
+
+		{pfx("1.2.0.0/16"), pfx("1.2.3.0/32"), true},
+		{pfx("1.2.3.0/32"), pfx("1.2.0.0/16"), true},
+
+		// Match /0 either order
+		{pfx("1.2.3.0/32"), pfx("0.0.0.0/0"), true},
+		{pfx("0.0.0.0/0"), pfx("1.2.3.0/32"), true},
+
+		{pfx("1.2.3.0/32"), pfx("5.5.5.5/0"), true}, // normalization not required; /0 means true
+
+		// IPv6 overlapping
+		{pfx("5::1/128"), pfx("5::0/8"), true},
+		{pfx("5::0/8"), pfx("5::1/128"), true},
+
+		// IPv6 not overlapping
+		{pfx("1::1/128"), pfx("2::2/128"), false},
+		{pfx("0100::0/8"), pfx("::1/128"), false},
+
+		// v6-mapped v4 should not overlap with IPv4.
+		{PrefixFrom(AddrFrom16(mustIP("1.2.0.0").As16()), 16), pfx("1.2.3.0/24"), false},
+
+		// Invalid prefixes
+		{PrefixFrom(mustIP("1.2.3.4"), 33), pfx("1.2.3.0/24"), false},
+		{PrefixFrom(mustIP("2000::"), 129), pfx("2000::/64"), false},
+	}
+	for i, tt := range tests {
+		if got := tt.a.Overlaps(tt.b); got != tt.want {
+			t.Errorf("%d. (%v).Overlaps(%v) = %v; want %v", i, tt.a, tt.b, got, tt.want)
+		}
+		// Overlaps is commutative
+		if got := tt.b.Overlaps(tt.a); got != tt.want {
+			t.Errorf("%d. (%v).Overlaps(%v) = %v; want %v", i, tt.b, tt.a, got, tt.want)
+		}
+	}
+}
+
+// Sink variables are here to force the compiler to not elide
+// seemingly useless work in benchmarks and allocation tests. If you
+// were to just `_ = foo()` within a test function, the compiler could
+// correctly deduce that foo() does nothing and doesn't need to be
+// called. By writing results to a global variable, we hide that fact
+// from the compiler and force it to keep the code under test.
+var (
+	sinkIP          Addr
+	sinkStdIP       net.IP
+	sinkAddrPort    AddrPort
+	sinkPrefix      Prefix
+	sinkPrefixSlice []Prefix
+	sinkInternValue *intern.Value
+	sinkIP16        [16]byte
+	sinkIP4         [4]byte
+	sinkBool        bool
+	sinkString      string
+	sinkBytes       []byte
+	sinkUDPAddr     = &net.UDPAddr{IP: make(net.IP, 0, 16)}
+)
+
+func TestNoAllocs(t *testing.T) {
+	// Wrappers that panic on error, to prove that our alloc-free
+	// methods are returning successfully.
+	panicIP := func(ip Addr, err error) Addr {
+		if err != nil {
+			panic(err)
+		}
+		return ip
+	}
+	panicPfx := func(pfx Prefix, err error) Prefix {
+		if err != nil {
+			panic(err)
+		}
+		return pfx
+	}
+	panicIPP := func(ipp AddrPort, err error) AddrPort {
+		if err != nil {
+			panic(err)
+		}
+		return ipp
+	}
+	test := func(name string, f func()) {
+		t.Run(name, func(t *testing.T) {
+			n := testing.AllocsPerRun(1000, f)
+			if n != 0 {
+				t.Fatalf("allocs = %d; want 0", int(n))
+			}
+		})
+	}
+
+	// IP constructors
+	test("IPv4", func() { sinkIP = IPv4(1, 2, 3, 4) })
+	test("AddrFrom4", func() { sinkIP = AddrFrom4([4]byte{1, 2, 3, 4}) })
+	test("AddrFrom16", func() { sinkIP = AddrFrom16([16]byte{}) })
+	test("ParseAddr/4", func() { sinkIP = panicIP(ParseAddr("1.2.3.4")) })
+	test("ParseAddr/6", func() { sinkIP = panicIP(ParseAddr("::1")) })
+	test("MustParseAddr", func() { sinkIP = MustParseAddr("1.2.3.4") })
+	test("IPv6LinkLocalAllNodes", func() { sinkIP = IPv6LinkLocalAllNodes() })
+	test("IPv6Unspecified", func() { sinkIP = IPv6Unspecified() })
+
+	// IP methods
+	test("IP.IsZero", func() { sinkBool = MustParseAddr("1.2.3.4").IsZero() })
+	test("IP.BitLen", func() { sinkBool = MustParseAddr("1.2.3.4").BitLen() == 8 })
+	test("IP.Zone/4", func() { sinkBool = MustParseAddr("1.2.3.4").Zone() == "" })
+	test("IP.Zone/6", func() { sinkBool = MustParseAddr("fe80::1").Zone() == "" })
+	test("IP.Zone/6zone", func() { sinkBool = MustParseAddr("fe80::1%zone").Zone() == "" })
+	test("IP.Compare", func() {
+		a := MustParseAddr("1.2.3.4")
+		b := MustParseAddr("2.3.4.5")
+		sinkBool = a.Compare(b) == 0
+	})
+	test("IP.Less", func() {
+		a := MustParseAddr("1.2.3.4")
+		b := MustParseAddr("2.3.4.5")
+		sinkBool = a.Less(b)
+	})
+	test("IP.Is4", func() { sinkBool = MustParseAddr("1.2.3.4").Is4() })
+	test("IP.Is6", func() { sinkBool = MustParseAddr("fe80::1").Is6() })
+	test("IP.Is4In6", func() { sinkBool = MustParseAddr("fe80::1").Is4In6() })
+	test("IP.Unmap", func() { sinkIP = MustParseAddr("ffff::2.3.4.5").Unmap() })
+	test("IP.WithZone", func() { sinkIP = MustParseAddr("fe80::1").WithZone("") })
+	test("IP.IsGlobalUnicast", func() { sinkBool = MustParseAddr("2001:db8::1").IsGlobalUnicast() })
+	test("IP.IsInterfaceLocalMulticast", func() { sinkBool = MustParseAddr("fe80::1").IsInterfaceLocalMulticast() })
+	test("IP.IsLinkLocalMulticast", func() { sinkBool = MustParseAddr("fe80::1").IsLinkLocalMulticast() })
+	test("IP.IsLinkLocalUnicast", func() { sinkBool = MustParseAddr("fe80::1").IsLinkLocalUnicast() })
+	test("IP.IsLoopback", func() { sinkBool = MustParseAddr("fe80::1").IsLoopback() })
+	test("IP.IsMulticast", func() { sinkBool = MustParseAddr("fe80::1").IsMulticast() })
+	test("IP.IsPrivate", func() { sinkBool = MustParseAddr("fd00::1").IsPrivate() })
+	test("IP.IsUnspecified", func() { sinkBool = IPv6Unspecified().IsUnspecified() })
+	test("IP.Prefix/4", func() { sinkPrefix = panicPfx(MustParseAddr("1.2.3.4").Prefix(20)) })
+	test("IP.Prefix/6", func() { sinkPrefix = panicPfx(MustParseAddr("fe80::1").Prefix(64)) })
+	test("IP.As16", func() { sinkIP16 = MustParseAddr("1.2.3.4").As16() })
+	test("IP.As4", func() { sinkIP4 = MustParseAddr("1.2.3.4").As4() })
+	test("IP.Next", func() { sinkIP = MustParseAddr("1.2.3.4").Next() })
+	test("IP.Prev", func() { sinkIP = MustParseAddr("1.2.3.4").Prev() })
+
+	// AddrPort constructors
+	test("AddrPortFrom", func() { sinkAddrPort = AddrPortFrom(IPv4(1, 2, 3, 4), 22) })
+	test("ParseAddrPort", func() { sinkAddrPort = panicIPP(ParseAddrPort("[::1]:1234")) })
+	test("MustParseAddrPort", func() { sinkAddrPort = MustParseAddrPort("[::1]:1234") })
+
+	// Prefix constructors
+	test("PrefixFrom", func() { sinkPrefix = PrefixFrom(IPv4(1, 2, 3, 4), 32) })
+	test("ParsePrefix/4", func() { sinkPrefix = panicPfx(ParsePrefix("1.2.3.4/20")) })
+	test("ParsePrefix/6", func() { sinkPrefix = panicPfx(ParsePrefix("fe80::1/64")) })
+	test("MustParsePrefix", func() { sinkPrefix = MustParsePrefix("1.2.3.4/20") })
+
+	// Prefix methods
+	test("Prefix.Contains", func() { sinkBool = MustParsePrefix("1.2.3.0/24").Contains(MustParseAddr("1.2.3.4")) })
+	test("Prefix.Overlaps", func() {
+		a, b := MustParsePrefix("1.2.3.0/24"), MustParsePrefix("1.2.0.0/16")
+		sinkBool = a.Overlaps(b)
+	})
+	test("Prefix.IsZero", func() { sinkBool = MustParsePrefix("1.2.0.0/16").IsZero() })
+	test("Prefix.IsSingleIP", func() { sinkBool = MustParsePrefix("1.2.3.4/32").IsSingleIP() })
+	test("IPPRefix.Masked", func() { sinkPrefix = MustParsePrefix("1.2.3.4/16").Masked() })
+}
+
+func TestPrefixString(t *testing.T) {
+	tests := []struct {
+		ipp  Prefix
+		want string
+	}{
+		{Prefix{}, "invalid Prefix"},
+		{PrefixFrom(Addr{}, 8), "invalid Prefix"},
+		{PrefixFrom(MustParseAddr("1.2.3.4"), 88), "invalid Prefix"},
+	}
+
+	for _, tt := range tests {
+		if got := tt.ipp.String(); got != tt.want {
+			t.Errorf("(%#v).String() = %q want %q", tt.ipp, got, tt.want)
+		}
+	}
+}
+
+func TestInvalidAddrPortString(t *testing.T) {
+	tests := []struct {
+		ipp  AddrPort
+		want string
+	}{
+		{AddrPort{}, "invalid AddrPort"},
+		{AddrPortFrom(Addr{}, 80), "invalid AddrPort"},
+	}
+
+	for _, tt := range tests {
+		if got := tt.ipp.String(); got != tt.want {
+			t.Errorf("(%#v).String() = %q want %q", tt.ipp, got, tt.want)
+		}
+	}
+}
+
+func TestAsSlice(t *testing.T) {
+	tests := []struct {
+		in   Addr
+		want []byte
+	}{
+		{in: Addr{}, want: nil},
+		{in: mustIP("1.2.3.4"), want: []byte{1, 2, 3, 4}},
+		{in: mustIP("ffff::1"), want: []byte{0xff, 0xff, 15: 1}},
+	}
+
+	for _, test := range tests {
+		got := test.in.AsSlice()
+		if !bytes.Equal(got, test.want) {
+			t.Errorf("%v.AsSlice() = %v want %v", test.in, got, test.want)
+		}
+	}
+}
+
+var sink16 [16]byte
+
+func BenchmarkAs16(b *testing.B) {
+	addr := MustParseAddr("1::10")
+	for i := 0; i < b.N; i++ {
+		sink16 = addr.As16()
+	}
+}