net: support IPv6 scoped addressing zone

This CL provides IPv6 scoped addressing zone support as defined
in RFC 4007 for internet protocol family connection setups.

Follwoing types and functions allow a literal IPv6 address with
zone identifer as theirs parameter.

pkg net, func Dial(string, string) (Conn, error)
pkg net, func DialOpt(string, ...DialOption) (Conn, error)
pkg net, func DialTimeout(string, string, time.Duration) (Conn, error)
pkg net, func Listen(string, string) (Listener, error)
pkg net, func ListenPacket(string, string) (PacketConn, error)
pkg net, func ResolveIPAddr(string, string) (*IPAddr, error)
pkg net, func ResolveTCPAddr(string, string) (*TCPAddr, error)
pkg net, func ResolveUDPAddr(string, string) (*UDPAddr, error)
pkg net, type IPAddr struct, Zone string
pkg net, type TCPAddr struct, Zone string
pkg net, type UDPAddr struct, Zone string

Also follwoing methods return a literal IPv6 address with zone
identifier string if possible.

pkg net, method (*IPAddr) String() string
pkg net, method (*TCPAddr) String() string
pkg net, method (*UDPAddr) String() string

Fixes #4234.
Fixes #4501.
Update #5081.

R=rsc, iant
CC=golang-dev
https://golang.org/cl/6816116

src/pkg/net/dial.go

@@ -169,22 +169,27 @@ func resolveAddr(op, net, addr string, deadline time.Time) (Addr, error) {
 // "unixpacket".
 //
 // For TCP and UDP networks, addresses have the form host:port.
-// If host is a literal IPv6 address, it must be enclosed
+// If host is a literal IPv6 address or host name, it must be enclosed
-// in square brackets.  The functions JoinHostPort and SplitHostPort
+// in square brackets as in "[::1]:80", "[ipv6-host]:http" or
-// manipulate addresses in this form.
+// "[ipv6-host%zone]:80".
+// The functions JoinHostPort and SplitHostPort manipulate addresses
+// in this form.
 //
 // Examples:
 //	Dial("tcp", "12.34.56.78:80")
-//	Dial("tcp", "google.com:80")
+//	Dial("tcp", "google.com:http")
-//	Dial("tcp", "[de:ad:be:ef::ca:fe]:80")
+//	Dial("tcp", "[2001:db8::1]:http")
+//	Dial("tcp", "[fe80::1%lo0]:80")
 //
-// For IP networks, net must be "ip", "ip4" or "ip6" followed
+// For IP networks, the net must be "ip", "ip4" or "ip6" followed by a
-// by a colon and a protocol number or name.
+// colon and a protocol number or name and the addr must be a literal
+// IP address.
 //
 // Examples:
 //	Dial("ip4:1", "127.0.0.1")
 //	Dial("ip6:ospf", "::1")
 //
+// For Unix networks, the addr must be a file system path.
 func Dial(net, addr string) (Conn, error) {
 	return DialOpt(addr, dialNetwork(net))
 }
@@ -290,8 +295,9 @@ func (a stringAddr) Network() string { return a.net }
 func (a stringAddr) String() string  { return a.addr }
 
 // Listen announces on the local network address laddr.
-// The network string net must be a stream-oriented network:
+// The network net must be a stream-oriented network: "tcp", "tcp4",
-// "tcp", "tcp4", "tcp6", "unix" or "unixpacket".
+// "tcp6", "unix" or "unixpacket".
+// See Dial for the syntax of laddr.
 func Listen(net, laddr string) (Listener, error) {
 	la, err := resolveAddr("listen", net, laddr, noDeadline)
 	if err != nil {
@@ -307,8 +313,9 @@ func Listen(net, laddr string) (Listener, error) {
 }
 
 // ListenPacket announces on the local network address laddr.
-// The network string net must be a packet-oriented network:
+// The network net must be a packet-oriented network: "udp", "udp4",
-// "udp", "udp4", "udp6", "ip", "ip4", "ip6" or "unixgram".
+// "udp6", "ip", "ip4", "ip6" or "unixgram".
+// See Dial for the syntax of laddr.
 func ListenPacket(net, laddr string) (PacketConn, error) {
 	la, err := resolveAddr("listen", net, laddr, noDeadline)
 	if err != nil {

src/pkg/net/interface_test.go

@@ -25,6 +25,32 @@ func loopbackInterface() *Interface {
 	return nil
 }
 
+// ipv6LinkLocalUnicastAddr returns an IPv6 link-local unicast address
+// on the given network interface for tests. It returns "" if no
+// suitable address is found.
+func ipv6LinkLocalUnicastAddr(ifi *Interface) string {
+	if ifi == nil {
+		return ""
+	}
+	ifat, err := ifi.Addrs()
+	if err != nil {
+		return ""
+	}
+	for _, ifa := range ifat {
+		switch ifa := ifa.(type) {
+		case *IPAddr:
+			if ifa.IP.To4() == nil && ifa.IP.IsLinkLocalUnicast() {
+				return ifa.IP.String()
+			}
+		case *IPNet:
+			if ifa.IP.To4() == nil && ifa.IP.IsLinkLocalUnicast() {
+				return ifa.IP.String()
+			}
+		}
+	}
+	return ""
+}
+
 func TestInterfaces(t *testing.T) {
 	ift, err := Interfaces()
 	if err != nil {
@@ -81,9 +107,9 @@ func testInterfaceMulticastAddrs(t *testing.T, ifi *Interface) {
 
 func testAddrs(t *testing.T, ifat []Addr) {
 	for _, ifa := range ifat {
-		switch v := ifa.(type) {
+		switch ifa := ifa.(type) {
 		case *IPAddr, *IPNet:
-			if v == nil {
+			if ifa == nil {
 				t.Errorf("\tunexpected value: %v", ifa)
 			} else {
 				t.Logf("\tinterface address %q", ifa.String())
@@ -96,9 +122,9 @@ func testAddrs(t *testing.T, ifat []Addr) {
 
 func testMulticastAddrs(t *testing.T, ifmat []Addr) {
 	for _, ifma := range ifmat {
-		switch v := ifma.(type) {
+		switch ifma := ifma.(type) {
 		case *IPAddr:
-			if v == nil {
+			if ifma == nil {
 				t.Errorf("\tunexpected value: %v", ifma)
 			} else {
 				t.Logf("\tjoined group address %q", ifma.String())

src/pkg/net/ip.go

@@ -431,6 +431,9 @@ func (n *IPNet) Contains(ip IP) bool {
 	return true
 }
 
+// Network returns the address's network name, "ip+net".
+func (n *IPNet) Network() string { return "ip+net" }
+
 // String returns the CIDR notation of n like "192.168.100.1/24"
 // or "2001:DB8::/48" as defined in RFC 4632 and RFC 4291.
 // If the mask is not in the canonical form, it returns the
@@ -449,9 +452,6 @@ func (n *IPNet) String() string {
 	return nn.String() + "/" + itod(uint(l))
 }
 
-// Network returns the address's network name, "ip+net".
-func (n *IPNet) Network() string { return "ip+net" }
-
 // Parse IPv4 address (d.d.d.d).
 func parseIPv4(s string) IP {
 	var p [IPv4len]byte
@@ -483,26 +483,26 @@ func parseIPv4(s string) IP {
 	return IPv4(p[0], p[1], p[2], p[3])
 }
 
-// Parse IPv6 address.  Many forms.
+// parseIPv6 parses s as a literal IPv6 address described in RFC 4291
-// The basic form is a sequence of eight colon-separated
+// and RFC 5952.  It can also parse a literal scoped IPv6 address with
-// 16-bit hex numbers separated by colons,
+// zone identifier which is described in RFC 4007 when zoneAllowed is
-// as in 0123:4567:89ab:cdef:0123:4567:89ab:cdef.
+// true.
-// Two exceptions:
+func parseIPv6(s string, zoneAllowed bool) (ip IP, zone string) {
-//	* A run of zeros can be replaced with "::".
+	ip = make(IP, IPv6len)
-//	* The last 32 bits can be in IPv4 form.
-// Thus, ::ffff:1.2.3.4 is the IPv4 address 1.2.3.4.
-func parseIPv6(s string) IP {
-	p := make(IP, IPv6len)
 	ellipsis := -1 // position of ellipsis in p
 	i := 0         // index in string s
 
+	if zoneAllowed {
+		s, zone = splitHostZone(s)
+	}
+
 	// Might have leading ellipsis
 	if len(s) >= 2 && s[0] == ':' && s[1] == ':' {
 		ellipsis = 0
 		i = 2
 		// Might be only ellipsis
 		if i == len(s) {
-			return p
+			return ip, zone
 		}
 	}
 
@@ -512,35 +512,35 @@ func parseIPv6(s string) IP {
 		// Hex number.
 		n, i1, ok := xtoi(s, i)
 		if !ok || n > 0xFFFF {
-			return nil
+			return nil, zone
 		}
 
 		// If followed by dot, might be in trailing IPv4.
 		if i1 < len(s) && s[i1] == '.' {
 			if ellipsis < 0 && j != IPv6len-IPv4len {
 				// Not the right place.
-				return nil
+				return nil, zone
 			}
 			if j+IPv4len > IPv6len {
 				// Not enough room.
-				return nil
+				return nil, zone
 			}
-			p4 := parseIPv4(s[i:])
+			ip4 := parseIPv4(s[i:])
-			if p4 == nil {
+			if ip4 == nil {
-				return nil
+				return nil, zone
 			}
-			p[j] = p4[12]
+			ip[j] = ip4[12]
-			p[j+1] = p4[13]
+			ip[j+1] = ip4[13]
-			p[j+2] = p4[14]
+			ip[j+2] = ip4[14]
-			p[j+3] = p4[15]
+			ip[j+3] = ip4[15]
 			i = len(s)
 			j += IPv4len
 			break
 		}
 
 		// Save this 16-bit chunk.
-		p[j] = byte(n >> 8)
+		ip[j] = byte(n >> 8)
-		p[j+1] = byte(n)
+		ip[j+1] = byte(n)
 		j += 2
 
 		// Stop at end of string.
@@ -551,14 +551,14 @@ func parseIPv6(s string) IP {
 
 		// Otherwise must be followed by colon and more.
 		if s[i] != ':' || i+1 == len(s) {
-			return nil
+			return nil, zone
 		}
 		i++
 
 		// Look for ellipsis.
 		if s[i] == ':' {
 			if ellipsis >= 0 { // already have one
-				return nil
+				return nil, zone
 			}
 			ellipsis = j
 			if i++; i == len(s) { // can be at end
@@ -569,23 +569,23 @@ func parseIPv6(s string) IP {
 
 	// Must have used entire string.
 	if i != len(s) {
-		return nil
+		return nil, zone
 	}
 
 	// If didn't parse enough, expand ellipsis.
 	if j < IPv6len {
 		if ellipsis < 0 {
-			return nil
+			return nil, zone
 		}
 		n := IPv6len - j
 		for k := j - 1; k >= ellipsis; k-- {
-			p[k+n] = p[k]
+			ip[k+n] = ip[k]
 		}
 		for k := ellipsis + n - 1; k >= ellipsis; k-- {
-			p[k] = 0
+			ip[k] = 0
 		}
 	}
-	return p
+	return ip, zone
 }
 
 // A ParseError represents a malformed text string and the type of string that was expected.
@@ -598,26 +598,17 @@ func (e *ParseError) Error() string {
 	return "invalid " + e.Type + ": " + e.Text
 }
 
-func parseIP(s string) IP {
-	if p := parseIPv4(s); p != nil {
-		return p
-	}
-	if p := parseIPv6(s); p != nil {
-		return p
-	}
-	return nil
-}
-
 // ParseIP parses s as an IP address, returning the result.
 // The string s can be in dotted decimal ("74.125.19.99")
 // or IPv6 ("2001:4860:0:2001::68") form.
 // If s is not a valid textual representation of an IP address,
 // ParseIP returns nil.
 func ParseIP(s string) IP {
-	if p := parseIPv4(s); p != nil {
+	if ip := parseIPv4(s); ip != nil {
-		return p
+		return ip
 	}
-	return parseIPv6(s)
+	ip, _ := parseIPv6(s, false)
+	return ip
 }
 
 // ParseCIDR parses s as a CIDR notation IP address and mask,
@@ -632,15 +623,15 @@ func ParseCIDR(s string) (IP, *IPNet, error) {
 	if i < 0 {
 		return nil, nil, &ParseError{"CIDR address", s}
 	}
-	ipstr, maskstr := s[:i], s[i+1:]
+	addr, mask := s[:i], s[i+1:]
 	iplen := IPv4len
-	ip := parseIPv4(ipstr)
+	ip := parseIPv4(addr)
 	if ip == nil {
 		iplen = IPv6len
-		ip = parseIPv6(ipstr)
+		ip, _ = parseIPv6(addr, false)
 	}
-	n, i, ok := dtoi(maskstr, 0)
+	n, i, ok := dtoi(mask, 0)
-	if ip == nil || !ok || i != len(maskstr) || n < 0 || n > 8*iplen {
+	if ip == nil || !ok || i != len(mask) || n < 0 || n > 8*iplen {
 		return nil, nil, &ParseError{"CIDR address", s}
 	}
 	m := CIDRMask(n, 8*iplen)

src/pkg/net/ip_test.go

@@ -22,6 +22,8 @@ var parseIPTests = []struct {
 	{"::ffff:127.0.0.1", IPv4(127, 0, 0, 1)},
 	{"2001:4860:0:2001::68", IP{0x20, 0x01, 0x48, 0x60, 0, 0, 0x20, 0x01, 0, 0, 0, 0, 0, 0, 0x00, 0x68}},
 	{"::ffff:4a7d:1363", IPv4(74, 125, 19, 99)},
+	{"fe80::1%lo0", nil},
+	{"fe80::1%911", nil},
 	{"", nil},
 }
 
@@ -37,7 +39,6 @@ var ipStringTests = []struct {
 	in  IP
 	out string // see RFC 5952
 }{
-
 	{IP{0x20, 0x1, 0xd, 0xb8, 0, 0, 0, 0, 0, 0, 0x1, 0x23, 0, 0x12, 0, 0x1}, "2001:db8::123:12:1"},
 	{IP{0x20, 0x1, 0xd, 0xb8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x1}, "2001:db8::1"},
 	{IP{0x20, 0x1, 0xd, 0xb8, 0, 0, 0, 0x1, 0, 0, 0, 0x1, 0, 0, 0, 0x1}, "2001:db8:0:1:0:1:0:1"},
@@ -257,8 +258,11 @@ var splitJoinTests = []struct {
 	{"www.google.com", "80", "www.google.com:80"},
 	{"127.0.0.1", "1234", "127.0.0.1:1234"},
 	{"::1", "80", "[::1]:80"},
-	{"google.com", "https%foo", "google.com:https%foo"}, // Go 1.0 behavior
+	{"fe80::1%lo0", "80", "[fe80::1%lo0]:80"},
+	{"localhost%lo0", "80", "[localhost%lo0]:80"},
 	{"", "0", ":0"},
+
+	{"google.com", "https%foo", "google.com:https%foo"}, // Go 1.0 behavior
 	{"127.0.0.1", "", "127.0.0.1:"},                     // Go 1.0 behaviour
 	{"www.google.com", "", "www.google.com:"},           // Go 1.0 behaviour
 }
@@ -270,15 +274,27 @@ var splitFailureTests = []struct {
 	{"www.google.com", "missing port in address"},
 	{"127.0.0.1", "missing port in address"},
 	{"[::1]", "missing port in address"},
+	{"[fe80::1%lo0]", "missing port in address"},
+	{"[localhost%lo0]", "missing port in address"},
+	{"localhost%lo0", "missing port in address"},
+
 	{"::1", "too many colons in address"},
+	{"fe80::1%lo0", "too many colons in address"},
+	{"fe80::1%lo0:80", "too many colons in address"},
+
+	{"localhost%lo0:80", "missing brackets in address"},
 
 	// Test cases that didn't fail in Go 1.0
+
 	{"[foo:bar]", "missing port in address"},
 	{"[foo:bar]baz", "missing port in address"},
-	{"[foo]:[bar]:baz", "too many colons in address"},
 	{"[foo]bar:baz", "missing port in address"},
+
+	{"[foo]:[bar]:baz", "too many colons in address"},
+
 	{"[foo]:[bar]baz", "unexpected '[' in address"},
 	{"foo[bar]:baz", "unexpected '[' in address"},
+
 	{"foo]bar:baz", "unexpected ']' in address"},
 }
 

src/pkg/net/ipraw_test.go

@@ -7,6 +7,7 @@ package net
 import (
 	"bytes"
 	"errors"
+	"fmt"
 	"os"
 	"reflect"
 	"testing"
@@ -27,6 +28,11 @@ var resolveIPAddrTests = []struct {
 	{"ip6", "::1", &IPAddr{IP: ParseIP("::1")}, nil},
 	{"ip6:icmp", "::1", &IPAddr{IP: ParseIP("::1")}, nil},
 
+	{"ip", "::1%en0", &IPAddr{IP: ParseIP("::1"), Zone: "en0"}, nil},
+	{"ip6", "::1%911", &IPAddr{IP: ParseIP("::1"), Zone: "911"}, nil},
+	{"ip6", "fe80::1", &IPAddr{IP: ParseIP("fe80::1"), Zone: "name"}, nil},
+	{"ip6", "fe80::1", &IPAddr{IP: ParseIP("fe80::1"), Zone: "index"}, nil},
+
 	{"", "127.0.0.1", &IPAddr{IP: IPv4(127, 0, 0, 1)}, nil}, // Go 1.0 behavior
 	{"", "::1", &IPAddr{IP: ParseIP("::1")}, nil},           // Go 1.0 behavior
 
@@ -37,6 +43,21 @@ var resolveIPAddrTests = []struct {
 
 func TestResolveIPAddr(t *testing.T) {
 	for _, tt := range resolveIPAddrTests {
+		if tt.addr != nil && (tt.addr.Zone == "name" || tt.addr.Zone == "index") {
+			ifi := loopbackInterface()
+			if ifi == nil {
+				continue
+			}
+			switch tt.addr.Zone {
+			case "name":
+				tt.litAddr += "%" + ifi.Name
+				tt.addr.Zone = zoneToString(ifi.Index)
+			case "index":
+				index := fmt.Sprintf("%v", ifi.Index)
+				tt.litAddr += "%" + index
+				tt.addr.Zone = index
+			}
+		}
 		addr, err := ResolveIPAddr(tt.net, tt.litAddr)
 		if err != tt.err {
 			t.Fatalf("ResolveIPAddr(%v, %v) failed: %v", tt.net, tt.litAddr, err)

src/pkg/net/iprawsock.go

@@ -19,12 +19,15 @@ func (a *IPAddr) String() string {
 	if a == nil {
 		return "<nil>"
 	}
+	if a.Zone != "" {
+		return a.IP.String() + "%" + a.Zone
+	}
 	return a.IP.String()
 }
 
-// ResolveIPAddr parses addr as an IP address and resolves domain
+// ResolveIPAddr parses addr as an IP address of the form "host" or
-// names to numeric addresses on the network net, which must be
+// "ipv6-host%zone" and resolves the domain name on the network net,
-// "ip", "ip4" or "ip6".
+// which must be "ip", "ip4" or "ip6".
 func ResolveIPAddr(net, addr string) (*IPAddr, error) {
 	if net == "" { // a hint wildcard for Go 1.0 undocumented behavior
 		net = "ip"

src/pkg/net/ipsock.go

@@ -68,15 +68,12 @@ func (e InvalidAddrError) Error() string   { return string(e) }
 func (e InvalidAddrError) Timeout() bool   { return false }
 func (e InvalidAddrError) Temporary() bool { return false }
 
-// SplitHostPort splits a network address of the form
+// SplitHostPort splits a network address of the form "host:port",
-// "host:port" or "[host]:port" into host and port.
+// "[host]:port" or "[ipv6-host%zone]:port" into host or
-// The latter form must be used when host contains a colon.
+// ipv6-host%zone and port.  A literal address or host name for IPv6
+// must be enclosed in square brackets, as in "[::1]:80",
+// "[ipv6-host]:http" or "[ipv6-host%zone]:80".
 func SplitHostPort(hostport string) (host, port string, err error) {
-	host, port, _, err = splitHostPort(hostport)
-	return
-}
-
-func splitHostPort(hostport string) (host, port, zone string, err error) {
 	j, k := 0, 0
 
 	// The port starts after the last colon.
@@ -110,10 +107,12 @@ func splitHostPort(hostport string) (host, port, zone string, err error) {
 		j, k = 1, end+1 // there can't be a '[' resp. ']' before these positions
 	} else {
 		host = hostport[:i]
-
 		if byteIndex(host, ':') >= 0 {
 			goto tooManyColons
 		}
+		if byteIndex(host, '%') >= 0 {
+			goto missingBrackets
+		}
 	}
 	if byteIndex(hostport[j:], '[') >= 0 {
 		err = &AddrError{"unexpected '[' in address", hostport}
@@ -134,13 +133,29 @@ missingPort:
 tooManyColons:
 	err = &AddrError{"too many colons in address", hostport}
 	return
+
+missingBrackets:
+	err = &AddrError{"missing brackets in address", hostport}
+	return
 }
 
-// JoinHostPort combines host and port into a network address
+func splitHostZone(s string) (host, zone string) {
-// of the form "host:port" or, if host contains a colon, "[host]:port".
+	// The IPv6 scoped addressing zone identifer starts after the
+	// last percent sign.
+	if i := last(s, '%'); i > 0 {
+		host, zone = s[:i], s[i+1:]
+	} else {
+		host = s
+	}
+	return
+}
+
+// JoinHostPort combines host and port into a network address of the
+// form "host:port" or, if host contains a colon or a percent sign,
+// "[host]:port".
 func JoinHostPort(host, port string) string {
-	// If host has colons, have to bracket it.
+	// If host has colons or a percent sign, have to bracket it.
-	if byteIndex(host, ':') >= 0 {
+	if byteIndex(host, ':') >= 0 || byteIndex(host, '%') >= 0 {
 		return "[" + host + "]:" + port
 	}
 	return host + ":" + port
@@ -155,7 +170,7 @@ func resolveInternetAddr(net, addr string, deadline time.Time) (Addr, error) {
 	switch net {
 	case "tcp", "tcp4", "tcp6", "udp", "udp4", "udp6":
 		if addr != "" {
-			if host, port, zone, err = splitHostPort(addr); err != nil {
+			if host, port, err = SplitHostPort(addr); err != nil {
 				return nil, err
 			}
 			if portnum, err = parsePort(net, port); err != nil {
@@ -184,21 +199,25 @@ func resolveInternetAddr(net, addr string, deadline time.Time) (Addr, error) {
 		return inetaddr(net, nil, portnum, zone), nil
 	}
 	// Try as an IP address.
-	if ip := ParseIP(host); ip != nil {
+	if ip := parseIPv4(host); ip != nil {
 		return inetaddr(net, ip, portnum, zone), nil
 	}
+	if ip, zone := parseIPv6(host, true); ip != nil {
+		return inetaddr(net, ip, portnum, zone), nil
+	}
+	// Try as a domain name.
+	host, zone = splitHostZone(host)
+	addrs, err := lookupHostDeadline(host, deadline)
+	if err != nil {
+		return nil, err
+	}
 	var filter func(IP) IP
 	if net != "" && net[len(net)-1] == '4' {
 		filter = ipv4only
 	}
-	if net != "" && net[len(net)-1] == '6' {
+	if net != "" && net[len(net)-1] == '6' || zone != "" {
 		filter = ipv6only
 	}
-	// Try as a DNS name.
-	addrs, err := lookupHostDeadline(host, deadline)
-	if err != nil {
-		return nil, err
-	}
 	ip := firstFavoriteAddr(filter, addrs)
 	if ip == nil {
 		// should not happen

src/pkg/net/tcp_test.go

@@ -5,6 +5,7 @@
 package net
 
 import (
+	"fmt"
 	"reflect"
 	"runtime"
 	"testing"
@@ -158,6 +159,11 @@ var resolveTCPAddrTests = []struct {
 	{"tcp", "[::1]:1", &TCPAddr{IP: ParseIP("::1"), Port: 1}, nil},
 	{"tcp6", "[::1]:65534", &TCPAddr{IP: ParseIP("::1"), Port: 65534}, nil},
 
+	{"tcp", "[::1%en0]:1", &TCPAddr{IP: ParseIP("::1"), Port: 1, Zone: "en0"}, nil},
+	{"tcp6", "[::1%911]:2", &TCPAddr{IP: ParseIP("::1"), Port: 2, Zone: "911"}, nil},
+	{"tcp6", "[fe80::1]:3", &TCPAddr{IP: ParseIP("fe80::1"), Port: 3, Zone: "name"}, nil},
+	{"tcp6", "[fe80::1]:4", &TCPAddr{IP: ParseIP("fe80::1"), Port: 4, Zone: "index"}, nil},
+
 	{"", "127.0.0.1:0", &TCPAddr{IP: IPv4(127, 0, 0, 1), Port: 0}, nil}, // Go 1.0 behavior
 	{"", "[::1]:0", &TCPAddr{IP: ParseIP("::1"), Port: 0}, nil},         // Go 1.0 behavior
 
@@ -166,6 +172,24 @@ var resolveTCPAddrTests = []struct {
 
 func TestResolveTCPAddr(t *testing.T) {
 	for _, tt := range resolveTCPAddrTests {
+		if tt.addr != nil && (tt.addr.Zone == "name" || tt.addr.Zone == "index") {
+			ifi := loopbackInterface()
+			if ifi == nil {
+				continue
+			}
+			i := last(tt.litAddr, ']')
+			if i > 0 {
+				switch tt.addr.Zone {
+				case "name":
+					tt.litAddr = tt.litAddr[:i] + "%" + ifi.Name + tt.litAddr[i:]
+					tt.addr.Zone = zoneToString(ifi.Index)
+				case "index":
+					index := fmt.Sprintf("%v", ifi.Index)
+					tt.litAddr = tt.litAddr[:i] + "%" + index + tt.litAddr[i:]
+					tt.addr.Zone = index
+				}
+			}
+		}
 		addr, err := ResolveTCPAddr(tt.net, tt.litAddr)
 		if err != tt.err {
 			t.Fatalf("ResolveTCPAddr(%v, %v) failed: %v", tt.net, tt.litAddr, err)
@@ -204,3 +228,79 @@ func TestTCPListenerName(t *testing.T) {
 		}
 	}
 }
+
+func TestIPv6LinkLocalUnicastTCP(t *testing.T) {
+	if testing.Short() || !*testExternal {
+		t.Skip("skipping test to avoid external network")
+	}
+	if !supportsIPv6 {
+		t.Skip("ipv6 is not supported")
+	}
+	ifi := loopbackInterface()
+	if ifi == nil {
+		t.Skip("loopback interface not found")
+	}
+	laddr := ipv6LinkLocalUnicastAddr(ifi)
+	if laddr == "" {
+		t.Skip("ipv6 unicast address on loopback not found")
+	}
+
+	type test struct {
+		net, addr  string
+		nameLookup bool
+	}
+	var tests = []test{
+		{"tcp", "[" + laddr + "%" + ifi.Name + "]:0", false},
+		{"tcp6", "[" + laddr + "%" + ifi.Name + "]:0", false},
+	}
+	switch runtime.GOOS {
+	case "darwin", "freebsd", "opensbd", "netbsd":
+		tests = append(tests, []test{
+			{"tcp", "[localhost%" + ifi.Name + "]:0", true},
+			{"tcp6", "[localhost%" + ifi.Name + "]:0", true},
+		}...)
+	case "linux":
+		tests = append(tests, []test{
+			{"tcp", "[ip6-localhost%" + ifi.Name + "]:0", true},
+			{"tcp6", "[ip6-localhost%" + ifi.Name + "]:0", true},
+		}...)
+	}
+	for _, tt := range tests {
+		ln, err := Listen(tt.net, tt.addr)
+		if err != nil {
+			// It might return "LookupHost returned no
+			// suitable address" error on some platforms.
+			t.Logf("Listen failed: %v", err)
+			continue
+		}
+		defer ln.Close()
+		if la, ok := ln.Addr().(*TCPAddr); !ok || !tt.nameLookup && la.Zone == "" {
+			t.Fatalf("got %v; expected a proper address with zone identifier", la)
+		}
+
+		done := make(chan int)
+		go transponder(t, ln, done)
+
+		c, err := Dial(tt.net, ln.Addr().String())
+		if err != nil {
+			t.Fatalf("Dial failed: %v", err)
+		}
+		defer c.Close()
+		if la, ok := c.LocalAddr().(*TCPAddr); !ok || !tt.nameLookup && la.Zone == "" {
+			t.Fatalf("got %v; expected a proper address with zone identifier", la)
+		}
+		if ra, ok := c.RemoteAddr().(*TCPAddr); !ok || !tt.nameLookup && ra.Zone == "" {
+			t.Fatalf("got %v; expected a proper address with zone identifier", ra)
+		}
+
+		if _, err := c.Write([]byte("TCP OVER IPV6 LINKLOCAL TEST")); err != nil {
+			t.Fatalf("Conn.Write failed: %v", err)
+		}
+		b := make([]byte, 32)
+		if _, err := c.Read(b); err != nil {
+			t.Fatalf("Conn.Read failed: %v", err)
+		}
+
+		<-done
+	}
+}

src/pkg/net/tcpsock.go

@@ -20,14 +20,18 @@ func (a *TCPAddr) String() string {
 	if a == nil {
 		return "<nil>"
 	}
+	if a.Zone != "" {
+		return JoinHostPort(a.IP.String()+"%"+a.Zone, itoa(a.Port))
+	}
 	return JoinHostPort(a.IP.String(), itoa(a.Port))
 }
 
-// ResolveTCPAddr parses addr as a TCP address of the form
+// ResolveTCPAddr parses addr as a TCP address of the form "host:port"
-// host:port and resolves domain names or port names to
+// or "[ipv6-host%zone]:port" and resolves a pair of domain name and
-// numeric addresses on the network net, which must be "tcp",
+// port name on the network net, which must be "tcp", "tcp4" or
-// "tcp4" or "tcp6".  A literal IPv6 host address must be
+// "tcp6".  A literal address or host name for IPv6 must be enclosed
-// enclosed in square brackets, as in "[::]:80".
+// in square brackets, as in "[::1]:80", "[ipv6-host]:http" or
+// "[ipv6-host%zone]:80".
 func ResolveTCPAddr(net, addr string) (*TCPAddr, error) {
 	switch net {
 	case "tcp", "tcp4", "tcp6":

src/pkg/net/udp_test.go

@@ -5,6 +5,7 @@
 package net
 
 import (
+	"fmt"
 	"reflect"
 	"runtime"
 	"testing"
@@ -22,6 +23,11 @@ var resolveUDPAddrTests = []struct {
 	{"udp", "[::1]:1", &UDPAddr{IP: ParseIP("::1"), Port: 1}, nil},
 	{"udp6", "[::1]:65534", &UDPAddr{IP: ParseIP("::1"), Port: 65534}, nil},
 
+	{"udp", "[::1%en0]:1", &UDPAddr{IP: ParseIP("::1"), Port: 1, Zone: "en0"}, nil},
+	{"udp6", "[::1%911]:2", &UDPAddr{IP: ParseIP("::1"), Port: 2, Zone: "911"}, nil},
+	{"udp6", "[fe80::1]:3", &UDPAddr{IP: ParseIP("fe80::1"), Port: 3, Zone: "name"}, nil},
+	{"udp6", "[fe80::1]:4", &UDPAddr{IP: ParseIP("fe80::1"), Port: 4, Zone: "index"}, nil},
+
 	{"", "127.0.0.1:0", &UDPAddr{IP: IPv4(127, 0, 0, 1), Port: 0}, nil}, // Go 1.0 behavior
 	{"", "[::1]:0", &UDPAddr{IP: ParseIP("::1"), Port: 0}, nil},         // Go 1.0 behavior
 
@@ -30,6 +36,24 @@ var resolveUDPAddrTests = []struct {
 
 func TestResolveUDPAddr(t *testing.T) {
 	for _, tt := range resolveUDPAddrTests {
+		if tt.addr != nil && (tt.addr.Zone == "name" || tt.addr.Zone == "index") {
+			ifi := loopbackInterface()
+			if ifi == nil {
+				continue
+			}
+			i := last(tt.litAddr, ']')
+			if i > 0 {
+				switch tt.addr.Zone {
+				case "name":
+					tt.litAddr = tt.litAddr[:i] + "%" + ifi.Name + tt.litAddr[i:]
+					tt.addr.Zone = zoneToString(ifi.Index)
+				case "index":
+					index := fmt.Sprintf("%v", ifi.Index)
+					tt.litAddr = tt.litAddr[:i] + "%" + index + tt.litAddr[i:]
+					tt.addr.Zone = index
+				}
+			}
+		}
 		addr, err := ResolveUDPAddr(tt.net, tt.litAddr)
 		if err != tt.err {
 			t.Fatalf("ResolveUDPAddr(%v, %v) failed: %v", tt.net, tt.litAddr, err)
@@ -146,3 +170,78 @@ func TestUDPConnLocalName(t *testing.T) {
 		}
 	}
 }
+
+func TestIPv6LinkLocalUnicastUDP(t *testing.T) {
+	if testing.Short() || !*testExternal {
+		t.Skip("skipping test to avoid external network")
+	}
+	if !supportsIPv6 {
+		t.Skip("ipv6 is not supported")
+	}
+	ifi := loopbackInterface()
+	if ifi == nil {
+		t.Skip("loopback interface not found")
+	}
+	laddr := ipv6LinkLocalUnicastAddr(ifi)
+	if laddr == "" {
+		t.Skip("ipv6 unicast address on loopback not found")
+	}
+
+	type test struct {
+		net, addr  string
+		nameLookup bool
+	}
+	var tests = []test{
+		{"udp", "[" + laddr + "%" + ifi.Name + "]:0", false},
+		{"udp6", "[" + laddr + "%" + ifi.Name + "]:0", false},
+	}
+	switch runtime.GOOS {
+	case "darwin", "freebsd", "openbsd", "netbsd":
+		tests = append(tests, []test{
+			{"udp", "[localhost%" + ifi.Name + "]:0", true},
+			{"udp6", "[localhost%" + ifi.Name + "]:0", true},
+		}...)
+	case "linux":
+		tests = append(tests, []test{
+			{"udp", "[ip6-localhost%" + ifi.Name + "]:0", true},
+			{"udp6", "[ip6-localhost%" + ifi.Name + "]:0", true},
+		}...)
+	}
+	for _, tt := range tests {
+		c1, err := ListenPacket(tt.net, tt.addr)
+		if err != nil {
+			// It might return "LookupHost returned no
+			// suitable address" error on some platforms.
+			t.Logf("ListenPacket failed: %v", err)
+			continue
+		}
+		defer c1.Close()
+		if la, ok := c1.LocalAddr().(*UDPAddr); !ok || !tt.nameLookup && la.Zone == "" {
+			t.Fatalf("got %v; expected a proper address with zone identifier", la)
+		}
+
+		c2, err := Dial(tt.net, c1.LocalAddr().String())
+		if err != nil {
+			t.Fatalf("Dial failed: %v", err)
+		}
+		defer c2.Close()
+		if la, ok := c2.LocalAddr().(*UDPAddr); !ok || !tt.nameLookup && la.Zone == "" {
+			t.Fatalf("got %v; expected a proper address with zone identifier", la)
+		}
+		if ra, ok := c2.RemoteAddr().(*UDPAddr); !ok || !tt.nameLookup && ra.Zone == "" {
+			t.Fatalf("got %v; expected a proper address with zone identifier", ra)
+		}
+
+		if _, err := c2.Write([]byte("UDP OVER IPV6 LINKLOCAL TEST")); err != nil {
+			t.Fatalf("Conn.Write failed: %v", err)
+		}
+		b := make([]byte, 32)
+		if _, from, err := c1.ReadFrom(b); err != nil {
+			t.Fatalf("PacketConn.ReadFrom failed: %v", err)
+		} else {
+			if ra, ok := from.(*UDPAddr); !ok || !tt.nameLookup && ra.Zone == "" {
+				t.Fatalf("got %v; expected a proper address with zone identifier", ra)
+			}
+		}
+	}
+}

src/pkg/net/udpsock.go

@@ -24,14 +24,18 @@ func (a *UDPAddr) String() string {
 	if a == nil {
 		return "<nil>"
 	}
+	if a.Zone != "" {
+		return JoinHostPort(a.IP.String()+"%"+a.Zone, itoa(a.Port))
+	}
 	return JoinHostPort(a.IP.String(), itoa(a.Port))
 }
 
-// ResolveUDPAddr parses addr as a UDP address of the form
+// ResolveUDPAddr parses addr as a UDP address of the form "host:port"
-// host:port and resolves domain names or port names to
+// or "[ipv6-host%zone]:port" and resolves a pair of domain name and
-// numeric addresses on the network net, which must be "udp",
+// port name on the network net, which must be "udp", "udp4" or
-// "udp4" or "udp6".  A literal IPv6 host address must be
+// "udp6".  A literal address or host name for IPv6 must be enclosed
-// enclosed in square brackets, as in "[::]:80".
+// in square brackets, as in "[::1]:80", "[ipv6-host]:http" or
+// "[ipv6-host%zone]:80".
 func ResolveUDPAddr(net, addr string) (*UDPAddr, error) {
 	switch net {
 	case "udp", "udp4", "udp6":