net, cmd/fix: add IPv6 scoped addressing zone to INET, INET6 address structs

This CL starts to introduce IPv6 scoped addressing capability
into the net package.

The Public API changes are:
+pkg net, type IPAddr struct, Zone string
+pkg net, type IPNet struct, Zone string
+pkg net, type TCPAddr struct, Zone string
+pkg net, type UDPAddr struct, Zone string

Update #4234.

R=rsc, bradfitz, iant
CC=golang-dev
https://golang.org/cl/6849045

14 files changed, 137 insertions, 117 deletions

diff --git a/src/pkg/net/ip.go b/src/pkg/net/ip.go
index 979d7acd53..0aac3d187a 100644
--- a/src/pkg/net/ip.go
+++ b/src/pkg/net/ip.go
@@ -36,6 +36,7 @@ type IPMask []byte
 type IPNet struct {
 	IP   IP     // network number
 	Mask IPMask // network mask
+	Zone string // IPv6 scoped addressing zone
 }
 
 // IPv4 returns the IP address (in 16-byte form) of the
@@ -645,5 +646,5 @@ func ParseCIDR(s string) (IP, *IPNet, error) {
 		return nil, nil, &ParseError{"CIDR address", s}
 	}
 	m := CIDRMask(n, 8*iplen)
-	return ip, &IPNet{ip.Mask(m), m}, nil
+	return ip, &IPNet{IP: ip.Mask(m), Mask: m}, nil
 }
diff --git a/src/pkg/net/ip_test.go b/src/pkg/net/ip_test.go
index df647ef73c..dc8a35270b 100644
--- a/src/pkg/net/ip_test.go
+++ b/src/pkg/net/ip_test.go
@@ -114,23 +114,23 @@ var parsecidrtests = []struct {
 	net *IPNet
 	err error
 }{
-	{"135.104.0.0/32", IPv4(135, 104, 0, 0), &IPNet{IPv4(135, 104, 0, 0), IPv4Mask(255, 255, 255, 255)}, nil},
-	{"0.0.0.0/24", IPv4(0, 0, 0, 0), &IPNet{IPv4(0, 0, 0, 0), IPv4Mask(255, 255, 255, 0)}, nil},
-	{"135.104.0.0/24", IPv4(135, 104, 0, 0), &IPNet{IPv4(135, 104, 0, 0), IPv4Mask(255, 255, 255, 0)}, nil},
-	{"135.104.0.1/32", IPv4(135, 104, 0, 1), &IPNet{IPv4(135, 104, 0, 1), IPv4Mask(255, 255, 255, 255)}, nil},
-	{"135.104.0.1/24", IPv4(135, 104, 0, 1), &IPNet{IPv4(135, 104, 0, 0), IPv4Mask(255, 255, 255, 0)}, nil},
-	{"::1/128", ParseIP("::1"), &IPNet{ParseIP("::1"), IPMask(ParseIP("ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff"))}, nil},
-	{"abcd:2345::/127", ParseIP("abcd:2345::"), &IPNet{ParseIP("abcd:2345::"), IPMask(ParseIP("ffff:ffff:ffff:ffff:ffff:ffff:ffff:fffe"))}, nil},
-	{"abcd:2345::/65", ParseIP("abcd:2345::"), &IPNet{ParseIP("abcd:2345::"), IPMask(ParseIP("ffff:ffff:ffff:ffff:8000::"))}, nil},
-	{"abcd:2345::/64", ParseIP("abcd:2345::"), &IPNet{ParseIP("abcd:2345::"), IPMask(ParseIP("ffff:ffff:ffff:ffff::"))}, nil},
-	{"abcd:2345::/63", ParseIP("abcd:2345::"), &IPNet{ParseIP("abcd:2345::"), IPMask(ParseIP("ffff:ffff:ffff:fffe::"))}, nil},
-	{"abcd:2345::/33", ParseIP("abcd:2345::"), &IPNet{ParseIP("abcd:2345::"), IPMask(ParseIP("ffff:ffff:8000::"))}, nil},
-	{"abcd:2345::/32", ParseIP("abcd:2345::"), &IPNet{ParseIP("abcd:2345::"), IPMask(ParseIP("ffff:ffff::"))}, nil},
-	{"abcd:2344::/31", ParseIP("abcd:2344::"), &IPNet{ParseIP("abcd:2344::"), IPMask(ParseIP("ffff:fffe::"))}, nil},
-	{"abcd:2300::/24", ParseIP("abcd:2300::"), &IPNet{ParseIP("abcd:2300::"), IPMask(ParseIP("ffff:ff00::"))}, nil},
-	{"abcd:2345::/24", ParseIP("abcd:2345::"), &IPNet{ParseIP("abcd:2300::"), IPMask(ParseIP("ffff:ff00::"))}, nil},
-	{"2001:DB8::/48", ParseIP("2001:DB8::"), &IPNet{ParseIP("2001:DB8::"), IPMask(ParseIP("ffff:ffff:ffff::"))}, nil},
-	{"2001:DB8::1/48", ParseIP("2001:DB8::1"), &IPNet{ParseIP("2001:DB8::"), IPMask(ParseIP("ffff:ffff:ffff::"))}, nil},
+	{"135.104.0.0/32", IPv4(135, 104, 0, 0), &IPNet{IP: IPv4(135, 104, 0, 0), Mask: IPv4Mask(255, 255, 255, 255)}, nil},
+	{"0.0.0.0/24", IPv4(0, 0, 0, 0), &IPNet{IP: IPv4(0, 0, 0, 0), Mask: IPv4Mask(255, 255, 255, 0)}, nil},
+	{"135.104.0.0/24", IPv4(135, 104, 0, 0), &IPNet{IP: IPv4(135, 104, 0, 0), Mask: IPv4Mask(255, 255, 255, 0)}, nil},
+	{"135.104.0.1/32", IPv4(135, 104, 0, 1), &IPNet{IP: IPv4(135, 104, 0, 1), Mask: IPv4Mask(255, 255, 255, 255)}, nil},
+	{"135.104.0.1/24", IPv4(135, 104, 0, 1), &IPNet{IP: IPv4(135, 104, 0, 0), Mask: IPv4Mask(255, 255, 255, 0)}, nil},
+	{"::1/128", ParseIP("::1"), &IPNet{IP: ParseIP("::1"), Mask: IPMask(ParseIP("ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff"))}, nil},
+	{"abcd:2345::/127", ParseIP("abcd:2345::"), &IPNet{IP: ParseIP("abcd:2345::"), Mask: IPMask(ParseIP("ffff:ffff:ffff:ffff:ffff:ffff:ffff:fffe"))}, nil},
+	{"abcd:2345::/65", ParseIP("abcd:2345::"), &IPNet{IP: ParseIP("abcd:2345::"), Mask: IPMask(ParseIP("ffff:ffff:ffff:ffff:8000::"))}, nil},
+	{"abcd:2345::/64", ParseIP("abcd:2345::"), &IPNet{IP: ParseIP("abcd:2345::"), Mask: IPMask(ParseIP("ffff:ffff:ffff:ffff::"))}, nil},
+	{"abcd:2345::/63", ParseIP("abcd:2345::"), &IPNet{IP: ParseIP("abcd:2345::"), Mask: IPMask(ParseIP("ffff:ffff:ffff:fffe::"))}, nil},
+	{"abcd:2345::/33", ParseIP("abcd:2345::"), &IPNet{IP: ParseIP("abcd:2345::"), Mask: IPMask(ParseIP("ffff:ffff:8000::"))}, nil},
+	{"abcd:2345::/32", ParseIP("abcd:2345::"), &IPNet{IP: ParseIP("abcd:2345::"), Mask: IPMask(ParseIP("ffff:ffff::"))}, nil},
+	{"abcd:2344::/31", ParseIP("abcd:2344::"), &IPNet{IP: ParseIP("abcd:2344::"), Mask: IPMask(ParseIP("ffff:fffe::"))}, nil},
+	{"abcd:2300::/24", ParseIP("abcd:2300::"), &IPNet{IP: ParseIP("abcd:2300::"), Mask: IPMask(ParseIP("ffff:ff00::"))}, nil},
+	{"abcd:2345::/24", ParseIP("abcd:2345::"), &IPNet{IP: ParseIP("abcd:2300::"), Mask: IPMask(ParseIP("ffff:ff00::"))}, nil},
+	{"2001:DB8::/48", ParseIP("2001:DB8::"), &IPNet{IP: ParseIP("2001:DB8::"), Mask: IPMask(ParseIP("ffff:ffff:ffff::"))}, nil},
+	{"2001:DB8::1/48", ParseIP("2001:DB8::1"), &IPNet{IP: ParseIP("2001:DB8::"), Mask: IPMask(ParseIP("ffff:ffff:ffff::"))}, nil},
 	{"192.168.1.1/255.255.255.0", nil, nil, &ParseError{"CIDR address", "192.168.1.1/255.255.255.0"}},
 	{"192.168.1.1/35", nil, nil, &ParseError{"CIDR address", "192.168.1.1/35"}},
 	{"2001:db8::1/-1", nil, nil, &ParseError{"CIDR address", "2001:db8::1/-1"}},
@@ -154,14 +154,14 @@ var ipnetcontainstests = []struct {
 	net *IPNet
 	ok  bool
 }{
-	{IPv4(172, 16, 1, 1), &IPNet{IPv4(172, 16, 0, 0), CIDRMask(12, 32)}, true},
-	{IPv4(172, 24, 0, 1), &IPNet{IPv4(172, 16, 0, 0), CIDRMask(13, 32)}, false},
-	{IPv4(192, 168, 0, 3), &IPNet{IPv4(192, 168, 0, 0), IPv4Mask(0, 0, 255, 252)}, true},
-	{IPv4(192, 168, 0, 4), &IPNet{IPv4(192, 168, 0, 0), IPv4Mask(0, 255, 0, 252)}, false},
-	{ParseIP("2001:db8:1:2::1"), &IPNet{ParseIP("2001:db8:1::"), CIDRMask(47, 128)}, true},
-	{ParseIP("2001:db8:1:2::1"), &IPNet{ParseIP("2001:db8:2::"), CIDRMask(47, 128)}, false},
-	{ParseIP("2001:db8:1:2::1"), &IPNet{ParseIP("2001:db8:1::"), IPMask(ParseIP("ffff:0:ffff::"))}, true},
-	{ParseIP("2001:db8:1:2::1"), &IPNet{ParseIP("2001:db8:1::"), IPMask(ParseIP("0:0:0:ffff::"))}, false},
+	{IPv4(172, 16, 1, 1), &IPNet{IP: IPv4(172, 16, 0, 0), Mask: CIDRMask(12, 32)}, true},
+	{IPv4(172, 24, 0, 1), &IPNet{IP: IPv4(172, 16, 0, 0), Mask: CIDRMask(13, 32)}, false},
+	{IPv4(192, 168, 0, 3), &IPNet{IP: IPv4(192, 168, 0, 0), Mask: IPv4Mask(0, 0, 255, 252)}, true},
+	{IPv4(192, 168, 0, 4), &IPNet{IP: IPv4(192, 168, 0, 0), Mask: IPv4Mask(0, 255, 0, 252)}, false},
+	{ParseIP("2001:db8:1:2::1"), &IPNet{IP: ParseIP("2001:db8:1::"), Mask: CIDRMask(47, 128)}, true},
+	{ParseIP("2001:db8:1:2::1"), &IPNet{IP: ParseIP("2001:db8:2::"), Mask: CIDRMask(47, 128)}, false},
+	{ParseIP("2001:db8:1:2::1"), &IPNet{IP: ParseIP("2001:db8:1::"), Mask: IPMask(ParseIP("ffff:0:ffff::"))}, true},
+	{ParseIP("2001:db8:1:2::1"), &IPNet{IP: ParseIP("2001:db8:1::"), Mask: IPMask(ParseIP("0:0:0:ffff::"))}, false},
 }
 
 func TestIPNetContains(t *testing.T) {
@@ -176,10 +176,10 @@ var ipnetstringtests = []struct {
 	in  *IPNet
 	out string
 }{
-	{&IPNet{IPv4(192, 168, 1, 0), CIDRMask(26, 32)}, "192.168.1.0/26"},
-	{&IPNet{IPv4(192, 168, 1, 0), IPv4Mask(255, 0, 255, 0)}, "192.168.1.0/ff00ff00"},
-	{&IPNet{ParseIP("2001:db8::"), CIDRMask(55, 128)}, "2001:db8::/55"},
-	{&IPNet{ParseIP("2001:db8::"), IPMask(ParseIP("8000:f123:0:cafe::"))}, "2001:db8::/8000f1230000cafe0000000000000000"},
+	{&IPNet{IP: IPv4(192, 168, 1, 0), Mask: CIDRMask(26, 32)}, "192.168.1.0/26"},
+	{&IPNet{IP: IPv4(192, 168, 1, 0), Mask: IPv4Mask(255, 0, 255, 0)}, "192.168.1.0/ff00ff00"},
+	{&IPNet{IP: ParseIP("2001:db8::"), Mask: CIDRMask(55, 128)}, "2001:db8::/55"},
+	{&IPNet{IP: ParseIP("2001:db8::"), Mask: IPMask(ParseIP("8000:f123:0:cafe::"))}, "2001:db8::/8000f1230000cafe0000000000000000"},
 }
 
 func TestIPNetString(t *testing.T) {
@@ -233,27 +233,27 @@ var networknumberandmasktests = []struct {
 	in  IPNet
 	out IPNet
 }{
-	{IPNet{v4addr, v4mask}, IPNet{v4addr, v4mask}},
-	{IPNet{v4addr, v4mappedv6mask}, IPNet{v4addr, v4mask}},
-	{IPNet{v4mappedv6addr, v4mappedv6mask}, IPNet{v4addr, v4mask}},
-	{IPNet{v4mappedv6addr, v6mask}, IPNet{v4addr, v4maskzero}},
-	{IPNet{v4addr, v6mask}, IPNet{v4addr, v4maskzero}},
-	{IPNet{v6addr, v6mask}, IPNet{v6addr, v6mask}},
-	{IPNet{v6addr, v4mappedv6mask}, IPNet{v6addr, v4mappedv6mask}},
-	{in: IPNet{v6addr, v4mask}},
-	{in: IPNet{v4addr, badmask}},
-	{in: IPNet{v4mappedv6addr, badmask}},
-	{in: IPNet{v6addr, badmask}},
-	{in: IPNet{badaddr, v4mask}},
-	{in: IPNet{badaddr, v4mappedv6mask}},
-	{in: IPNet{badaddr, v6mask}},
-	{in: IPNet{badaddr, badmask}},
+	{IPNet{IP: v4addr, Mask: v4mask}, IPNet{IP: v4addr, Mask: v4mask}},
+	{IPNet{IP: v4addr, Mask: v4mappedv6mask}, IPNet{IP: v4addr, Mask: v4mask}},
+	{IPNet{IP: v4mappedv6addr, Mask: v4mappedv6mask}, IPNet{IP: v4addr, Mask: v4mask}},
+	{IPNet{IP: v4mappedv6addr, Mask: v6mask}, IPNet{IP: v4addr, Mask: v4maskzero}},
+	{IPNet{IP: v4addr, Mask: v6mask}, IPNet{IP: v4addr, Mask: v4maskzero}},
+	{IPNet{IP: v6addr, Mask: v6mask}, IPNet{IP: v6addr, Mask: v6mask}},
+	{IPNet{IP: v6addr, Mask: v4mappedv6mask}, IPNet{IP: v6addr, Mask: v4mappedv6mask}},
+	{in: IPNet{IP: v6addr, Mask: v4mask}},
+	{in: IPNet{IP: v4addr, Mask: badmask}},
+	{in: IPNet{IP: v4mappedv6addr, Mask: badmask}},
+	{in: IPNet{IP: v6addr, Mask: badmask}},
+	{in: IPNet{IP: badaddr, Mask: v4mask}},
+	{in: IPNet{IP: badaddr, Mask: v4mappedv6mask}},
+	{in: IPNet{IP: badaddr, Mask: v6mask}},
+	{in: IPNet{IP: badaddr, Mask: badmask}},
 }
 
 func TestNetworkNumberAndMask(t *testing.T) {
 	for _, tt := range networknumberandmasktests {
 		ip, m := networkNumberAndMask(&tt.in)
-		out := &IPNet{ip, m}
+		out := &IPNet{IP: ip, Mask: m}
 		if !reflect.DeepEqual(&tt.out, out) {
 			t.Errorf("networkNumberAndMask(%v) = %v; want %v", tt.in, out, &tt.out)
 		}
diff --git a/src/pkg/net/iprawsock.go b/src/pkg/net/iprawsock.go
index d7bffc69e9..a141e6aee7 100644
--- a/src/pkg/net/iprawsock.go
+++ b/src/pkg/net/iprawsock.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// (Raw) IP sockets
+// Raw IP sockets
 
 package net
 
@@ -12,7 +12,8 @@ import (
 
 // IPAddr represents the address of an IP end point.
 type IPAddr struct {
-	IP IP
+	IP   IP
+	Zone string // IPv6 scoped addressing zone
 }
 
 // Network returns the address's network name, "ip".
@@ -38,7 +39,7 @@ func resolveIPAddr(net, addr string, deadline time.Time) (*IPAddr, error) {
 	if err != nil {
 		return nil, err
 	}
-	return &IPAddr{ip}, nil
+	return &IPAddr{IP: ip}, nil
 }
 
 // Convert "host" into IP address.
diff --git a/src/pkg/net/iprawsock_plan9.go b/src/pkg/net/iprawsock_plan9.go
index e77c5476af..9a28256251 100644
--- a/src/pkg/net/iprawsock_plan9.go
+++ b/src/pkg/net/iprawsock_plan9.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// (Raw) IP sockets stubs for Plan 9
+// Raw IP sockets for Plan 9
 
 package net
 
@@ -77,8 +77,6 @@ func (c *IPConn) Close() error {
 	return syscall.EPLAN9
 }
 
-// IP-specific methods.
-
 // ReadFromIP reads an IP packet from c, copying the payload into b.
 // It returns the number of bytes copied into b and the return address
 // that was on the packet.
diff --git a/src/pkg/net/iprawsock_posix.go b/src/pkg/net/iprawsock_posix.go
index 00e87cfbf0..7a8cd4470d 100644
--- a/src/pkg/net/iprawsock_posix.go
+++ b/src/pkg/net/iprawsock_posix.go
@@ -4,7 +4,7 @@
 
 // +build darwin freebsd linux netbsd openbsd windows
 
-// (Raw) IP sockets
+// Raw IP sockets for POSIX
 
 package net
 
@@ -16,9 +16,9 @@ import (
 func sockaddrToIP(sa syscall.Sockaddr) Addr {
 	switch sa := sa.(type) {
 	case *syscall.SockaddrInet4:
-		return &IPAddr{sa.Addr[0:]}
+		return &IPAddr{IP: sa.Addr[0:]}
 	case *syscall.SockaddrInet6:
-		return &IPAddr{sa.Addr[0:]}
+		return &IPAddr{IP: sa.Addr[0:], Zone: zoneToString(int(sa.ZoneId))}
 	}
 	return nil
 }
@@ -41,7 +41,7 @@ func (a *IPAddr) isWildcard() bool {
 }
 
 func (a *IPAddr) sockaddr(family int) (syscall.Sockaddr, error) {
-	return ipToSockaddr(family, a.IP, 0)
+	return ipToSockaddr(family, a.IP, 0, a.Zone)
 }
 
 func (a *IPAddr) toAddr() sockaddr {
@@ -59,8 +59,6 @@ type IPConn struct {
 
 func newIPConn(fd *netFD) *IPConn { return &IPConn{conn{fd}} }
 
-// IP-specific methods.
-
 // ReadFromIP reads an IP packet from c, copying the payload into b.
 // It returns the number of bytes copied into b and the return address
 // that was on the packet.
@@ -78,14 +76,14 @@ func (c *IPConn) ReadFromIP(b []byte) (int, *IPAddr, error) {
 	n, sa, err := c.fd.ReadFrom(b)
 	switch sa := sa.(type) {
 	case *syscall.SockaddrInet4:
-		addr = &IPAddr{sa.Addr[0:]}
+		addr = &IPAddr{IP: sa.Addr[0:]}
 		if len(b) >= IPv4len { // discard ipv4 header
 			hsize := (int(b[0]) & 0xf) * 4
 			copy(b, b[hsize:])
 			n -= hsize
 		}
 	case *syscall.SockaddrInet6:
-		addr = &IPAddr{sa.Addr[0:]}
+		addr = &IPAddr{IP: sa.Addr[0:], Zone: zoneToString(int(sa.ZoneId))}
 	}
 	return n, addr, err
 }
@@ -95,8 +93,8 @@ func (c *IPConn) ReadFrom(b []byte) (int, Addr, error) {
 	if !c.ok() {
 		return 0, nil, syscall.EINVAL
 	}
-	n, uaddr, err := c.ReadFromIP(b)
-	return n, uaddr.toAddr(), err
+	n, addr, err := c.ReadFromIP(b)
+	return n, addr.toAddr(), err
 }
 
 // ReadMsgIP reads a packet from c, copying the payload into b and the
@@ -111,9 +109,9 @@ func (c *IPConn) ReadMsgIP(b, oob []byte) (n, oobn, flags int, addr *IPAddr, err
 	n, oobn, flags, sa, err = c.fd.ReadMsg(b, oob)
 	switch sa := sa.(type) {
 	case *syscall.SockaddrInet4:
-		addr = &IPAddr{sa.Addr[0:]}
+		addr = &IPAddr{IP: sa.Addr[0:]}
 	case *syscall.SockaddrInet6:
-		addr = &IPAddr{sa.Addr[0:]}
+		addr = &IPAddr{IP: sa.Addr[0:], Zone: zoneToString(int(sa.ZoneId))}
 	}
 	return
 }
diff --git a/src/pkg/net/ipsock.go b/src/pkg/net/ipsock.go
index 9d48e8c103..bd6fe7a0e0 100644
--- a/src/pkg/net/ipsock.go
+++ b/src/pkg/net/ipsock.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// IP sockets
+// Internet protocol family sockets
 
 package net
 
@@ -143,3 +143,24 @@ func hostPortToIP(net, hostport string, deadline time.Time) (ip IP, iport int, e
 
 	return addr, p, nil
 }
+
+func zoneToString(zone int) string {
+	if zone == 0 {
+		return ""
+	}
+	if ifi, err := InterfaceByIndex(zone); err == nil {
+		return ifi.Name
+	}
+	return itod(uint(zone))
+}
+
+func zoneToInt(zone string) int {
+	if zone == "" {
+		return 0
+	}
+	if ifi, err := InterfaceByName(zone); err == nil {
+		return ifi.Index
+	}
+	n, _, _ := dtoi(zone, 0)
+	return n
+}
diff --git a/src/pkg/net/ipsock_plan9.go b/src/pkg/net/ipsock_plan9.go
index 138c3b4855..eaef768fd0 100644
--- a/src/pkg/net/ipsock_plan9.go
+++ b/src/pkg/net/ipsock_plan9.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// IP sockets stubs for Plan 9
+// Internet protocol family sockets for Plan 9
 
 package net
 
@@ -59,9 +59,9 @@ func readPlan9Addr(proto, filename string) (addr Addr, err error) {
 	}
 	switch proto {
 	case "tcp":
-		addr = &TCPAddr{ip, port}
+		addr = &TCPAddr{IP: ip, Port: port}
 	case "udp":
-		addr = &UDPAddr{ip, port}
+		addr = &UDPAddr{IP: ip, Port: port}
 	default:
 		return nil, errors.New("unknown protocol " + proto)
 	}
diff --git a/src/pkg/net/ipsock_posix.go b/src/pkg/net/ipsock_posix.go
index 87a2288973..4c37616ecf 100644
--- a/src/pkg/net/ipsock_posix.go
+++ b/src/pkg/net/ipsock_posix.go
@@ -4,6 +4,8 @@
 
 // +build darwin freebsd linux netbsd openbsd windows
 
+// Internet protocol family sockets for POSIX
+
 package net
 
 import (
@@ -155,7 +157,7 @@ Error:
 	return nil, &OpError{mode, net, addr, err}
 }
 
-func ipToSockaddr(family int, ip IP, port int) (syscall.Sockaddr, error) {
+func ipToSockaddr(family int, ip IP, port int, zone string) (syscall.Sockaddr, error) {
 	switch family {
 	case syscall.AF_INET:
 		if len(ip) == 0 {
@@ -164,12 +166,12 @@ func ipToSockaddr(family int, ip IP, port int) (syscall.Sockaddr, error) {
 		if ip = ip.To4(); ip == nil {
 			return nil, InvalidAddrError("non-IPv4 address")
 		}
-		s := new(syscall.SockaddrInet4)
+		sa := new(syscall.SockaddrInet4)
 		for i := 0; i < IPv4len; i++ {
-			s.Addr[i] = ip[i]
+			sa.Addr[i] = ip[i]
 		}
-		s.Port = port
-		return s, nil
+		sa.Port = port
+		return sa, nil
 	case syscall.AF_INET6:
 		if len(ip) == 0 {
 			ip = IPv6zero
@@ -183,12 +185,13 @@ func ipToSockaddr(family int, ip IP, port int) (syscall.Sockaddr, error) {
 		if ip = ip.To16(); ip == nil {
 			return nil, InvalidAddrError("non-IPv6 address")
 		}
-		s := new(syscall.SockaddrInet6)
+		sa := new(syscall.SockaddrInet6)
 		for i := 0; i < IPv6len; i++ {
-			s.Addr[i] = ip[i]
+			sa.Addr[i] = ip[i]
 		}
-		s.Port = port
-		return s, nil
+		sa.Port = port
+		sa.ZoneId = uint32(zoneToInt(zone))
+		return sa, nil
 	}
 	return nil, InvalidAddrError("unexpected socket family")
 }
diff --git a/src/pkg/net/multicast_posix_test.go b/src/pkg/net/multicast_posix_test.go
index d4a8a35627..bcc13ee851 100644
--- a/src/pkg/net/multicast_posix_test.go
+++ b/src/pkg/net/multicast_posix_test.go
@@ -21,26 +21,26 @@ var multicastListenerTests = []struct {
 }{
 	// cf. RFC 4727: Experimental Values in IPv4, IPv6, ICMPv4, ICMPv6, UDP, and TCP Headers
 
-	{"udp", &UDPAddr{IPv4(224, 0, 0, 254), 12345}, FlagUp | FlagLoopback, false},
-	{"udp", &UDPAddr{IPv4(224, 0, 0, 254), 12345}, 0, false},
-	{"udp", &UDPAddr{ParseIP("ff0e::114"), 12345}, FlagUp | FlagLoopback, true},
-	{"udp", &UDPAddr{ParseIP("ff0e::114"), 12345}, 0, true},
+	{"udp", &UDPAddr{IP: IPv4(224, 0, 0, 254), Port: 12345}, FlagUp | FlagLoopback, false},
+	{"udp", &UDPAddr{IP: IPv4(224, 0, 0, 254), Port: 12345}, 0, false},
+	{"udp", &UDPAddr{IP: ParseIP("ff0e::114"), Port: 12345}, FlagUp | FlagLoopback, true},
+	{"udp", &UDPAddr{IP: ParseIP("ff0e::114"), Port: 12345}, 0, true},
 
-	{"udp4", &UDPAddr{IPv4(224, 0, 0, 254), 12345}, FlagUp | FlagLoopback, false},
-	{"udp4", &UDPAddr{IPv4(224, 0, 0, 254), 12345}, 0, false},
+	{"udp4", &UDPAddr{IP: IPv4(224, 0, 0, 254), Port: 12345}, FlagUp | FlagLoopback, false},
+	{"udp4", &UDPAddr{IP: IPv4(224, 0, 0, 254), Port: 12345}, 0, false},
 
-	{"udp6", &UDPAddr{ParseIP("ff01::114"), 12345}, FlagUp | FlagLoopback, true},
-	{"udp6", &UDPAddr{ParseIP("ff01::114"), 12345}, 0, true},
-	{"udp6", &UDPAddr{ParseIP("ff02::114"), 12345}, FlagUp | FlagLoopback, true},
-	{"udp6", &UDPAddr{ParseIP("ff02::114"), 12345}, 0, true},
-	{"udp6", &UDPAddr{ParseIP("ff04::114"), 12345}, FlagUp | FlagLoopback, true},
-	{"udp6", &UDPAddr{ParseIP("ff04::114"), 12345}, 0, true},
-	{"udp6", &UDPAddr{ParseIP("ff05::114"), 12345}, FlagUp | FlagLoopback, true},
-	{"udp6", &UDPAddr{ParseIP("ff05::114"), 12345}, 0, true},
-	{"udp6", &UDPAddr{ParseIP("ff08::114"), 12345}, FlagUp | FlagLoopback, true},
-	{"udp6", &UDPAddr{ParseIP("ff08::114"), 12345}, 0, true},
-	{"udp6", &UDPAddr{ParseIP("ff0e::114"), 12345}, FlagUp | FlagLoopback, true},
-	{"udp6", &UDPAddr{ParseIP("ff0e::114"), 12345}, 0, true},
+	{"udp6", &UDPAddr{IP: ParseIP("ff01::114"), Port: 12345}, FlagUp | FlagLoopback, true},
+	{"udp6", &UDPAddr{IP: ParseIP("ff01::114"), Port: 12345}, 0, true},
+	{"udp6", &UDPAddr{IP: ParseIP("ff02::114"), Port: 12345}, FlagUp | FlagLoopback, true},
+	{"udp6", &UDPAddr{IP: ParseIP("ff02::114"), Port: 12345}, 0, true},
+	{"udp6", &UDPAddr{IP: ParseIP("ff04::114"), Port: 12345}, FlagUp | FlagLoopback, true},
+	{"udp6", &UDPAddr{IP: ParseIP("ff04::114"), Port: 12345}, 0, true},
+	{"udp6", &UDPAddr{IP: ParseIP("ff05::114"), Port: 12345}, FlagUp | FlagLoopback, true},
+	{"udp6", &UDPAddr{IP: ParseIP("ff05::114"), Port: 12345}, 0, true},
+	{"udp6", &UDPAddr{IP: ParseIP("ff08::114"), Port: 12345}, FlagUp | FlagLoopback, true},
+	{"udp6", &UDPAddr{IP: ParseIP("ff08::114"), Port: 12345}, 0, true},
+	{"udp6", &UDPAddr{IP: ParseIP("ff0e::114"), Port: 12345}, FlagUp | FlagLoopback, true},
+	{"udp6", &UDPAddr{IP: ParseIP("ff0e::114"), Port: 12345}, 0, true},
 }
 
 // TestMulticastListener tests both single and double listen to a test
diff --git a/src/pkg/net/tcpsock.go b/src/pkg/net/tcpsock.go
index 6aba1f89fc..acded26528 100644
--- a/src/pkg/net/tcpsock.go
+++ b/src/pkg/net/tcpsock.go
@@ -12,6 +12,7 @@ import "time"
 type TCPAddr struct {
 	IP   IP
 	Port int
+	Zone string // IPv6 scoped addressing zone
 }
 
 // Network returns the address's network name, "tcp".
@@ -38,5 +39,5 @@ func resolveTCPAddr(net, addr string, deadline time.Time) (*TCPAddr, error) {
 	if err != nil {
 		return nil, err
 	}
-	return &TCPAddr{ip, port}, nil
+	return &TCPAddr{IP: ip, Port: port}, nil
 }
diff --git a/src/pkg/net/tcpsock_posix.go b/src/pkg/net/tcpsock_posix.go
index e5b3a09f75..2d70165647 100644
--- a/src/pkg/net/tcpsock_posix.go
+++ b/src/pkg/net/tcpsock_posix.go
@@ -23,9 +23,9 @@ import (
 func sockaddrToTCP(sa syscall.Sockaddr) Addr {
 	switch sa := sa.(type) {
 	case *syscall.SockaddrInet4:
-		return &TCPAddr{sa.Addr[0:], sa.Port}
+		return &TCPAddr{IP: sa.Addr[0:], Port: sa.Port}
 	case *syscall.SockaddrInet6:
-		return &TCPAddr{sa.Addr[0:], sa.Port}
+		return &TCPAddr{IP: sa.Addr[0:], Port: sa.Port, Zone: zoneToString(int(sa.ZoneId))}
 	default:
 		if sa != nil {
 			// Diagnose when we will turn a non-nil sockaddr into a nil.
@@ -53,7 +53,7 @@ func (a *TCPAddr) isWildcard() bool {
 }
 
 func (a *TCPAddr) sockaddr(family int) (syscall.Sockaddr, error) {
-	return ipToSockaddr(family, a.IP, a.Port)
+	return ipToSockaddr(family, a.IP, a.Port, a.Zone)
 }
 
 func (a *TCPAddr) toAddr() sockaddr {
diff --git a/src/pkg/net/udpsock.go b/src/pkg/net/udpsock.go
index bf2107b03a..66f795185c 100644
--- a/src/pkg/net/udpsock.go
+++ b/src/pkg/net/udpsock.go
@@ -17,6 +17,7 @@ var ErrWriteToConnected = errors.New("use of WriteTo with pre-connected UDP")
 type UDPAddr struct {
 	IP   IP
 	Port int
+	Zone string // IPv6 scoped addressing zone
 }
 
 // Network returns the address's network name, "udp".
@@ -43,5 +44,5 @@ func resolveUDPAddr(net, addr string, deadline time.Time) (*UDPAddr, error) {
 	if err != nil {
 		return nil, err
 	}
-	return &UDPAddr{ip, port}, nil
+	return &UDPAddr{IP: ip, Port: port}, nil
 }
diff --git a/src/pkg/net/udpsock_plan9.go b/src/pkg/net/udpsock_plan9.go
index 6a828e14d2..46d2de2380 100644
--- a/src/pkg/net/udpsock_plan9.go
+++ b/src/pkg/net/udpsock_plan9.go
@@ -19,8 +19,6 @@ type UDPConn struct {
 	conn
 }
 
-// UDP-specific methods.
-
 // ReadFromUDP reads a UDP packet from c, copying the payload into b.
 // It returns the number of bytes copied into b and the return address
 // that was on the packet.
@@ -50,7 +48,7 @@ func (c *UDPConn) ReadFromUDP(b []byte) (n int, addr *UDPAddr, err error) {
 
 	h, buf := unmarshalUDPHeader(buf)
 	n = copy(b, buf)
-	return n, &UDPAddr{h.raddr, int(h.rport)}, nil
+	return n, &UDPAddr{IP: h.raddr, Port: int(h.rport)}, nil
 }
 
 // ReadFrom implements the PacketConn ReadFrom method.
diff --git a/src/pkg/net/udpsock_posix.go b/src/pkg/net/udpsock_posix.go
index d7329bf32f..b7de678f92 100644
--- a/src/pkg/net/udpsock_posix.go
+++ b/src/pkg/net/udpsock_posix.go
@@ -4,7 +4,7 @@
 
 // +build darwin freebsd linux netbsd openbsd windows
 
-// UDP sockets
+// UDP sockets for POSIX
 
 package net
 
@@ -16,9 +16,9 @@ import (
 func sockaddrToUDP(sa syscall.Sockaddr) Addr {
 	switch sa := sa.(type) {
 	case *syscall.SockaddrInet4:
-		return &UDPAddr{sa.Addr[0:], sa.Port}
+		return &UDPAddr{IP: sa.Addr[0:], Port: sa.Port}
 	case *syscall.SockaddrInet6:
-		return &UDPAddr{sa.Addr[0:], sa.Port}
+		return &UDPAddr{IP: sa.Addr[0:], Port: sa.Port, Zone: zoneToString(int(sa.ZoneId))}
 	}
 	return nil
 }
@@ -41,7 +41,7 @@ func (a *UDPAddr) isWildcard() bool {
 }
 
 func (a *UDPAddr) sockaddr(family int) (syscall.Sockaddr, error) {
-	return ipToSockaddr(family, a.IP, a.Port)
+	return ipToSockaddr(family, a.IP, a.Port, a.Zone)
 }
 
 func (a *UDPAddr) toAddr() sockaddr {
@@ -59,8 +59,6 @@ type UDPConn struct {
 
 func newUDPConn(fd *netFD) *UDPConn { return &UDPConn{conn{fd}} }
 
-// UDP-specific methods.
-
 // ReadFromUDP reads a UDP packet from c, copying the payload into b.
 // It returns the number of bytes copied into b and the return address
 // that was on the packet.
@@ -74,9 +72,9 @@ func (c *UDPConn) ReadFromUDP(b []byte) (n int, addr *UDPAddr, err error) {
 	n, sa, err := c.fd.ReadFrom(b)
 	switch sa := sa.(type) {
 	case *syscall.SockaddrInet4:
-		addr = &UDPAddr{sa.Addr[0:], sa.Port}
+		addr = &UDPAddr{IP: sa.Addr[0:], Port: sa.Port}
 	case *syscall.SockaddrInet6:
-		addr = &UDPAddr{sa.Addr[0:], sa.Port}
+		addr = &UDPAddr{IP: sa.Addr[0:], Port: sa.Port, Zone: zoneToString(int(sa.ZoneId))}
 	}
 	return
 }
@@ -86,8 +84,8 @@ func (c *UDPConn) ReadFrom(b []byte) (int, Addr, error) {
 	if !c.ok() {
 		return 0, nil, syscall.EINVAL
 	}
-	n, uaddr, err := c.ReadFromUDP(b)
-	return n, uaddr.toAddr(), err
+	n, addr, err := c.ReadFromUDP(b)
+	return n, addr.toAddr(), err
 }
 
 // ReadMsgUDP reads a packet from c, copying the payload into b and
@@ -103,9 +101,9 @@ func (c *UDPConn) ReadMsgUDP(b, oob []byte) (n, oobn, flags int, addr *UDPAddr,
 	n, oobn, flags, sa, err = c.fd.ReadMsg(b, oob)
 	switch sa := sa.(type) {
 	case *syscall.SockaddrInet4:
-		addr = &UDPAddr{sa.Addr[0:], sa.Port}
+		addr = &UDPAddr{IP: sa.Addr[0:], Port: sa.Port}
 	case *syscall.SockaddrInet6:
-		addr = &UDPAddr{sa.Addr[0:], sa.Port}
+		addr = &UDPAddr{IP: sa.Addr[0:], Port: sa.Port, Zone: zoneToString(int(sa.ZoneId))}
 	}
 	return
 }
@@ -276,7 +274,7 @@ func listenIPv6MulticastUDP(c *UDPConn, ifi *Interface, ip IP) error {
 func joinIPv4GroupUDP(c *UDPConn, ifi *Interface, ip IP) error {
 	err := joinIPv4Group(c.fd, ifi, ip)
 	if err != nil {
-		return &OpError{"joinipv4group", c.fd.net, &IPAddr{ip}, err}
+		return &OpError{"joinipv4group", c.fd.net, &IPAddr{IP: ip}, err}
 	}
 	return nil
 }
@@ -284,7 +282,7 @@ func joinIPv4GroupUDP(c *UDPConn, ifi *Interface, ip IP) error {
 func joinIPv6GroupUDP(c *UDPConn, ifi *Interface, ip IP) error {
 	err := joinIPv6Group(c.fd, ifi, ip)
 	if err != nil {
-		return &OpError{"joinipv6group", c.fd.net, &IPAddr{ip}, err}
+		return &OpError{"joinipv6group", c.fd.net, &IPAddr{IP: ip}, err}
 	}
 	return nil
 }