net, internal/syscall/windows: fix interface and address identification on windows

The current implementation including Go 1.5 through 1.5.2 misuses Windows API and mishandles the returned values from GetAdapterAddresses on Windows. This change fixes various issues related to network facility information by readjusting interface and interface address parsers. Updates #5395. Updates #10530. Updates #12301. Updates #12551. Updates #13542. Fixes #12691. Fixes #12811. Fixes #13476. Fixes #13544. Also fixes fragile screen scraping test cases in net_windows_test.go. Additional information for reviewers: It seems like almost all the issues above have the same root cause and it is misunderstanding of Windows API. If my interpretation of the information on MSDN is correctly, current implementation contains the following bugs: - SIO_GET_INTERFACE_LIST should not be used for IPv6. The behavior of SIO_GET_INTERFACE_LIST is different on kernels and probably it doesn't work correctly for IPv6 on old kernels such as Windows XP w/ SP2. Unfortunately MSDN doesn't describe the detail of SIO_GET_INTERFACE_LIST, but information on the net suggests so. - Fetching IP_ADAPTER_ADDRESSES structures with fixed size area may not work when using IPv6. IPv6 generates ton of interface addresses for various addressing scopes. We need to adjust the area appropriately. - PhysicalAddress field of IP_ADAPTER_ADDRESSES structure may have extra space. We cannot ignore PhysicalAddressLength field of IP_ADAPTER_ADDRESS structure. - Flags field of IP_ADAPTER_ADDRESSES structure doesn't represent any of administratively and operatinal statuses. It just represents settings for windows network adapter. - MTU field of IP_ADAPTER_ADDRESSES structure may have a uint32(-1) on 64-bit platform. We need to convert the value to interger appropriately. - IfType field of IP_ADAPTER_ADDRESSES structure is not a bit field. Bitwire operation for the field is completely wrong. - OperStatus field of IP_ADAPTER_ADDRESSES structure is not a bit field. Bitwire operation for the field is completely wrong. - IPv6IfIndex field of IP_ADAPTER_ADDRESSES structure is just a substitute for IfIndex field. We cannot prefer IPv6IfIndex to IfIndex. - Windows XP, 2003 server and below don't set OnLinkPrefixLength field of IP_ADAPTER_UNICAST_ADDRESS structure. We cannot rely on the field on old kernels. We can use FirstPrefix field of IP_ADAPTER_ADDRESSES structure and IP_ADAPTER_PREFIX structure instead. - Length field of IP_ADAPTER_{UNICAST,ANYCAST,MULTICAST}_ADDRESS sturecures doesn't represent an address prefix length. It just represents a socket address length. Change-Id: Icabdaf7bd1d41360a981d2dad0b830b02b584528 Reviewed-on: https://go-review.googlesource.com/17412 Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
2025-05-28 19:02:22 +00:00 · 2015-12-04 19:06:01 +09:00 · 2015-12-04 19:06:01 +09:00 · e05b48e22c
commit e05b48e22c
parent c2ef005486
6 changed files with 369 additions and 163 deletions
--- a/src/internal/syscall/windows/syscall_windows.go
+++ b/src/internal/syscall/windows/syscall_windows.go
@ -10,7 +10,17 @@ import "syscall"

 const GAA_FLAG_INCLUDE_PREFIX = 0x00000010

-const IF_TYPE_SOFTWARE_LOOPBACK = 24
+const (
+	IF_TYPE_OTHER              = 1
+	IF_TYPE_ETHERNET_CSMACD    = 6
+	IF_TYPE_ISO88025_TOKENRING = 9
+	IF_TYPE_PPP                = 23
+	IF_TYPE_SOFTWARE_LOOPBACK  = 24
+	IF_TYPE_ATM                = 37
+	IF_TYPE_IEEE80211          = 71
+	IF_TYPE_TUNNEL             = 131
+	IF_TYPE_IEEE1394           = 144
+)

 type SocketAddress struct {
 	Sockaddr       *syscall.RawSockaddrAny
@ -94,7 +104,7 @@ const (
 	IfOperStatusLowerLayerDown = 7
 )

-//sys GetAdaptersAddresses(family uint32, flags uint32, reserved uintptr, adapterAddresses *IpAdapterAddresses, sizeOfPointer *uint32) (errcode error) = iphlpapi.GetAdaptersAddresses
+//sys	GetAdaptersAddresses(family uint32, flags uint32, reserved uintptr, adapterAddresses *IpAdapterAddresses, sizePointer *uint32) (errcode error) = iphlpapi.GetAdaptersAddresses
 //sys	GetComputerNameEx(nameformat uint32, buf *uint16, n *uint32) (err error) = GetComputerNameExW
 //sys	MoveFileEx(from *uint16, to *uint16, flags uint32) (err error) = MoveFileExW

--- a/src/internal/syscall/windows/zsyscall_windows.go
+++ b/src/internal/syscall/windows/zsyscall_windows.go
@ -16,8 +16,8 @@ var (
 	procMoveFileExW          = modkernel32.NewProc("MoveFileExW")
 )

-func GetAdaptersAddresses(family uint32, flags uint32, reserved uintptr, adapterAddresses *IpAdapterAddresses, sizeOfPointer *uint32) (errcode error) {
-	r0, _, _ := syscall.Syscall6(procGetAdaptersAddresses.Addr(), 5, uintptr(family), uintptr(flags), uintptr(reserved), uintptr(unsafe.Pointer(adapterAddresses)), uintptr(unsafe.Pointer(sizeOfPointer)), 0)
+func GetAdaptersAddresses(family uint32, flags uint32, reserved uintptr, adapterAddresses *IpAdapterAddresses, sizePointer *uint32) (errcode error) {
+	r0, _, _ := syscall.Syscall6(procGetAdaptersAddresses.Addr(), 5, uintptr(family), uintptr(flags), uintptr(reserved), uintptr(unsafe.Pointer(adapterAddresses)), uintptr(unsafe.Pointer(sizePointer)), 0)
 	if r0 != 0 {
 		errcode = syscall.Errno(r0)
 	}
--- a/src/net/interface_test.go
+++ b/src/net/interface_test.go
@ -188,18 +188,39 @@ func testAddrs(t *testing.T, ifat []Addr) (naf4, naf6 int) {
 			prefixLen, maxPrefixLen := ifa.Mask.Size()
 			if ifa.IP.To4() != nil {
 				if 0 >= prefixLen || prefixLen > 8*IPv4len || maxPrefixLen != 8*IPv4len {
-					t.Errorf("unexpected prefix length: %v/%v", prefixLen, maxPrefixLen)
+					t.Errorf("unexpected prefix length: %d/%d", prefixLen, maxPrefixLen)
+					continue
+				}
+				if ifa.IP.IsLoopback() && (prefixLen != 8 && prefixLen != 8*IPv4len) { // see RFC 1122
+					t.Errorf("unexpected prefix length for IPv4 loopback: %d/%d", prefixLen, maxPrefixLen)
 					continue
 				}
 				naf4++
-			} else if ifa.IP.To16() != nil {
+			}
+			if ifa.IP.To16() != nil && ifa.IP.To4() == nil {
 				if 0 >= prefixLen || prefixLen > 8*IPv6len || maxPrefixLen != 8*IPv6len {
-					t.Errorf("unexpected prefix length: %v/%v", prefixLen, maxPrefixLen)
+					t.Errorf("unexpected prefix length: %d/%d", prefixLen, maxPrefixLen)
+					continue
+				}
+				if ifa.IP.IsLoopback() && prefixLen != 8*IPv6len { // see RFC 4291
+					t.Errorf("unexpected prefix length for IPv6 loopback: %d/%d", prefixLen, maxPrefixLen)
 					continue
 				}
 				naf6++
 			}
 			t.Logf("interface address %q", ifa.String())
+		case *IPAddr:
+			if ifa == nil || ifa.IP == nil || ifa.IP.IsUnspecified() || ifa.IP.IsMulticast() {
+				t.Errorf("unexpected value: %+v", ifa)
+				continue
+			}
+			if ifa.IP.To4() != nil {
+				naf4++
+			}
+			if ifa.IP.To16() != nil && ifa.IP.To4() == nil {
+				naf6++
+			}
+			t.Logf("interface address %s", ifa.String())
 		default:
 			t.Errorf("unexpected type: %T", ifa)
 		}
@ -217,7 +238,8 @@ func testMulticastAddrs(t *testing.T, ifmat []Addr) (nmaf4, nmaf6 int) {
 			}
 			if ifma.IP.To4() != nil {
 				nmaf4++
-			} else if ifma.IP.To16() != nil {
+			}
+			if ifma.IP.To16() != nil && ifma.IP.To4() == nil {
 				nmaf6++
 			}
 			t.Logf("joined group address %q", ifma.String())
--- a/src/net/interface_windows.go
+++ b/src/net/interface_windows.go
@ -11,131 +11,105 @@ import (
 	"unsafe"
 )

-func getAdapters() (*windows.IpAdapterAddresses, error) {
-	block := uint32(unsafe.Sizeof(windows.IpAdapterAddresses{}))
+// supportsVistaIP reports whether the platform implements new IP
+// stack and ABIs supported on Windows Vista and above.
+var supportsVistaIP bool

-	// pre-allocate a 15KB working buffer pointed to by the AdapterAddresses
-	// parameter.
-	// https://msdn.microsoft.com/en-us/library/windows/desktop/aa365915(v=vs.85).aspx
-	size := uint32(15000)
+func init() {
+	supportsVistaIP = probeWindowsIPStack()
+}

-	var addrs []windows.IpAdapterAddresses
+func probeWindowsIPStack() (supportsVistaIP bool) {
+	v, err := syscall.GetVersion()
+	if err != nil {
+		return true // Windows 10 and above will deprecate this API
+	}
+	if byte(v) < 6 { // major version of Windows Vista is 6
+		return false
+	}
+	return true
+}
+
+// adapterAddresses returns a list of IP adapter and address
+// structures. The structure contains an IP adapter and flattened
+// multiple IP addresses including unicast, anycast and multicast
+// addresses.
+func adapterAddresses() ([]*windows.IpAdapterAddresses, error) {
+	var b []byte
+	l := uint32(15000) // recommended initial size
 	for {
-		addrs = make([]windows.IpAdapterAddresses, size/block+1)
-		err := windows.GetAdaptersAddresses(syscall.AF_UNSPEC, windows.GAA_FLAG_INCLUDE_PREFIX, 0, &addrs[0], &size)
+		b = make([]byte, l)
+		err := windows.GetAdaptersAddresses(syscall.AF_UNSPEC, windows.GAA_FLAG_INCLUDE_PREFIX, 0, (*windows.IpAdapterAddresses)(unsafe.Pointer(&b[0])), &l)
 		if err == nil {
+			if l == 0 {
+				return nil, nil
+			}
 			break
 		}
 		if err.(syscall.Errno) != syscall.ERROR_BUFFER_OVERFLOW {
 			return nil, os.NewSyscallError("getadaptersaddresses", err)
 		}
-	}
-	return &addrs[0], nil
-}
-
-func getInterfaceInfos() ([]syscall.InterfaceInfo, error) {
-	s, err := sysSocket(syscall.AF_INET, syscall.SOCK_DGRAM, syscall.IPPROTO_UDP)
-	if err != nil {
-		return nil, err
-	}
-	defer closeFunc(s)
-
-	iia := [20]syscall.InterfaceInfo{}
-	ret := uint32(0)
-	size := uint32(unsafe.Sizeof(iia))
-	err = syscall.WSAIoctl(s, syscall.SIO_GET_INTERFACE_LIST, nil, 0, (*byte)(unsafe.Pointer(&iia[0])), size, &ret, nil, 0)
-	if err != nil {
-		return nil, os.NewSyscallError("wsaioctl", err)
-	}
-	iilen := ret / uint32(unsafe.Sizeof(iia[0]))
-	return iia[:iilen], nil
-}
-
-func bytesEqualIP(a []byte, b []int8) bool {
-	for i := 0; i < len(a); i++ {
-		if a[i] != byte(b[i]) {
-			return false
+		if l <= uint32(len(b)) {
+			return nil, os.NewSyscallError("getadaptersaddresses", err)
 		}
 	}
-	return true
+	var aas []*windows.IpAdapterAddresses
+	for aa := (*windows.IpAdapterAddresses)(unsafe.Pointer(&b[0])); aa != nil; aa = aa.Next {
+		aas = append(aas, aa)
 	}
-
-func findInterfaceInfo(iis []syscall.InterfaceInfo, paddr *windows.IpAdapterAddresses) *syscall.InterfaceInfo {
-	for _, ii := range iis {
-		iaddr := (*syscall.RawSockaddr)(unsafe.Pointer(&ii.Address))
-		puni := paddr.FirstUnicastAddress
-		for ; puni != nil; puni = puni.Next {
-			if iaddr.Family == puni.Address.Sockaddr.Addr.Family {
-				switch iaddr.Family {
-				case syscall.AF_INET:
-					a := (*syscall.RawSockaddrInet4)(unsafe.Pointer(&ii.Address)).Addr
-					if bytesEqualIP(a[:], puni.Address.Sockaddr.Addr.Data[2:]) {
-						return &ii
-					}
-				case syscall.AF_INET6:
-					a := (*syscall.RawSockaddrInet6)(unsafe.Pointer(&ii.Address)).Addr
-					if bytesEqualIP(a[:], puni.Address.Sockaddr.Addr.Data[2:]) {
-						return &ii
-					}
-				default:
-					continue
-				}
-			}
-		}
-	}
-	return nil
+	return aas, nil
 }

 // If the ifindex is zero, interfaceTable returns mappings of all
 // network interfaces.  Otherwise it returns a mapping of a specific
 // interface.
 func interfaceTable(ifindex int) ([]Interface, error) {
-	paddr, err := getAdapters()
+	aas, err := adapterAddresses()
 	if err != nil {
 		return nil, err
 	}
-
-	iis, err := getInterfaceInfos()
-	if err != nil {
-		return nil, err
-	}
-
 	var ift []Interface
-	for ; paddr != nil; paddr = paddr.Next {
-		index := paddr.IfIndex
-		if paddr.Ipv6IfIndex != 0 {
-			index = paddr.Ipv6IfIndex
+	for _, aa := range aas {
+		index := aa.IfIndex
+		if index == 0 { // ipv6IfIndex is a sustitute for ifIndex
+			index = aa.Ipv6IfIndex
 		}
 		if ifindex == 0 || ifindex == int(index) {
-			ii := findInterfaceInfo(iis, paddr)
-			if ii == nil {
-				continue
-			}
-			var flags Flags
-			if paddr.Flags&windows.IfOperStatusUp != 0 {
-				flags |= FlagUp
-			}
-			if paddr.IfType&windows.IF_TYPE_SOFTWARE_LOOPBACK != 0 {
-				flags |= FlagLoopback
-			}
-			if ii.Flags&syscall.IFF_BROADCAST != 0 {
-				flags |= FlagBroadcast
-			}
-			if ii.Flags&syscall.IFF_POINTTOPOINT != 0 {
-				flags |= FlagPointToPoint
-			}
-			if ii.Flags&syscall.IFF_MULTICAST != 0 {
-				flags |= FlagMulticast
-			}
 			ifi := Interface{
 				Index: int(index),
-				MTU:          int(paddr.Mtu),
-				Name:         syscall.UTF16ToString((*(*[10000]uint16)(unsafe.Pointer(paddr.FriendlyName)))[:]),
-				HardwareAddr: HardwareAddr(paddr.PhysicalAddress[:]),
-				Flags:        flags,
+				Name:  syscall.UTF16ToString((*(*[10000]uint16)(unsafe.Pointer(aa.FriendlyName)))[:]),
+			}
+			if aa.OperStatus == windows.IfOperStatusUp {
+				ifi.Flags |= FlagUp
+			}
+			// For now we need to infer link-layer service
+			// capabilities from media types.
+			// We will be able to use
+			// MIB_IF_ROW2.AccessType once we drop support
+			// for Windows XP.
+			switch aa.IfType {
+			case windows.IF_TYPE_ETHERNET_CSMACD, windows.IF_TYPE_ISO88025_TOKENRING, windows.IF_TYPE_IEEE80211, windows.IF_TYPE_IEEE1394:
+				ifi.Flags |= FlagBroadcast | FlagMulticast
+			case windows.IF_TYPE_PPP, windows.IF_TYPE_TUNNEL:
+				ifi.Flags |= FlagPointToPoint | FlagMulticast
+			case windows.IF_TYPE_SOFTWARE_LOOPBACK:
+				ifi.Flags |= FlagLoopback | FlagMulticast
+			case windows.IF_TYPE_ATM:
+				ifi.Flags |= FlagBroadcast |
+					FlagPointToPoint |
+					FlagMulticast // assume all services available; LANE, point-to-point and point-to-multipoint
+			}
+			if aa.Mtu == 0xffffffff {
+				ifi.MTU = -1
+			} else {
+				ifi.MTU = int(aa.Mtu)
+			}
+			if aa.PhysicalAddressLength > 0 {
+				ifi.HardwareAddr = make(HardwareAddr, aa.PhysicalAddressLength)
+				copy(ifi.HardwareAddr, aa.PhysicalAddress[:])
 			}
 			ift = append(ift, ifi)
-			if ifindex == int(ifi.Index) {
+			if ifindex == ifi.Index {
 				break
 			}
 		}
@ -147,86 +121,156 @@ func interfaceTable(ifindex int) ([]Interface, error) {
 // network interfaces.  Otherwise it returns addresses for a specific
 // interface.
 func interfaceAddrTable(ifi *Interface) ([]Addr, error) {
-	paddr, err := getAdapters()
+	aas, err := adapterAddresses()
 	if err != nil {
 		return nil, err
 	}
-
 	var ifat []Addr
-	for ; paddr != nil; paddr = paddr.Next {
-		index := paddr.IfIndex
-		if paddr.Ipv6IfIndex != 0 {
-			index = paddr.Ipv6IfIndex
+	for _, aa := range aas {
+		index := aa.IfIndex
+		if index == 0 { // ipv6IfIndex is a sustitute for ifIndex
+			index = aa.Ipv6IfIndex
+		}
+		var pfx4, pfx6 []IPNet
+		if !supportsVistaIP {
+			pfx4, pfx6, err = addrPrefixTable(aa)
+			if err != nil {
+				return nil, err
+			}
 		}
 		if ifi == nil || ifi.Index == int(index) {
-			puni := paddr.FirstUnicastAddress
-			for ; puni != nil; puni = puni.Next {
-				if sa, err := puni.Address.Sockaddr.Sockaddr(); err == nil {
-					switch sav := sa.(type) {
+			for puni := aa.FirstUnicastAddress; puni != nil; puni = puni.Next {
+				sa, err := puni.Address.Sockaddr.Sockaddr()
+				if err != nil {
+					return nil, os.NewSyscallError("sockaddr", err)
+				}
+				var l int
+				switch sa := sa.(type) {
 				case *syscall.SockaddrInet4:
-						ifa := &IPNet{IP: make(IP, IPv4len), Mask: CIDRMask(int(puni.Address.SockaddrLength), 8*IPv4len)}
-						copy(ifa.IP, sav.Addr[:])
+					if supportsVistaIP {
+						l = int(puni.OnLinkPrefixLength)
+					} else {
+						l = addrPrefixLen(pfx4, IP(sa.Addr[:]))
+					}
+					ifa := &IPNet{IP: make(IP, IPv4len), Mask: CIDRMask(l, 8*IPv4len)}
+					copy(ifa.IP, sa.Addr[:])
 					ifat = append(ifat, ifa)
 				case *syscall.SockaddrInet6:
-						ifa := &IPNet{IP: make(IP, IPv6len), Mask: CIDRMask(int(puni.Address.SockaddrLength), 8*IPv6len)}
-						copy(ifa.IP, sav.Addr[:])
+					if supportsVistaIP {
+						l = int(puni.OnLinkPrefixLength)
+					} else {
+						l = addrPrefixLen(pfx6, IP(sa.Addr[:]))
+					}
+					ifa := &IPNet{IP: make(IP, IPv6len), Mask: CIDRMask(l, 8*IPv6len)}
+					copy(ifa.IP, sa.Addr[:])
 					ifat = append(ifat, ifa)
 				}
 			}
+			for pany := aa.FirstAnycastAddress; pany != nil; pany = pany.Next {
+				sa, err := pany.Address.Sockaddr.Sockaddr()
+				if err != nil {
+					return nil, os.NewSyscallError("sockaddr", err)
 				}
-			pany := paddr.FirstAnycastAddress
-			for ; pany != nil; pany = pany.Next {
-				if sa, err := pany.Address.Sockaddr.Sockaddr(); err == nil {
-					switch sav := sa.(type) {
+				switch sa := sa.(type) {
 				case *syscall.SockaddrInet4:
-						ifa := &IPNet{IP: make(IP, IPv4len), Mask: CIDRMask(int(pany.Address.SockaddrLength), 8*IPv4len)}
-						copy(ifa.IP, sav.Addr[:])
+					ifa := &IPAddr{IP: make(IP, IPv4len)}
+					copy(ifa.IP, sa.Addr[:])
 					ifat = append(ifat, ifa)
 				case *syscall.SockaddrInet6:
-						ifa := &IPNet{IP: make(IP, IPv6len), Mask: CIDRMask(int(pany.Address.SockaddrLength), 8*IPv6len)}
-						copy(ifa.IP, sav.Addr[:])
+					ifa := &IPAddr{IP: make(IP, IPv6len)}
+					copy(ifa.IP, sa.Addr[:])
 					ifat = append(ifat, ifa)
 				}
 			}
 		}
 	}
+	return ifat, nil
 }

-	return ifat, nil
+func addrPrefixTable(aa *windows.IpAdapterAddresses) (pfx4, pfx6 []IPNet, err error) {
+	for p := aa.FirstPrefix; p != nil; p = p.Next {
+		sa, err := p.Address.Sockaddr.Sockaddr()
+		if err != nil {
+			return nil, nil, os.NewSyscallError("sockaddr", err)
+		}
+		switch sa := sa.(type) {
+		case *syscall.SockaddrInet4:
+			pfx := IPNet{IP: IP(sa.Addr[:]), Mask: CIDRMask(int(p.PrefixLength), 8*IPv4len)}
+			pfx4 = append(pfx4, pfx)
+		case *syscall.SockaddrInet6:
+			pfx := IPNet{IP: IP(sa.Addr[:]), Mask: CIDRMask(int(p.PrefixLength), 8*IPv6len)}
+			pfx6 = append(pfx6, pfx)
+		}
+	}
+	return
+}
+
+// addrPrefixLen returns an appropriate prefix length in bits for ip
+// from pfxs. It returns 32 or 128 when no appropriate on-link address
+// prefix found.
+//
+// NOTE: This is pretty naive implementation that contains many
+// allocations and non-effective linear search, and should not be used
+// freely.
+func addrPrefixLen(pfxs []IPNet, ip IP) int {
+	var l int
+	var cand *IPNet
+	for i := range pfxs {
+		if !pfxs[i].Contains(ip) {
+			continue
+		}
+		if cand == nil {
+			l, _ = pfxs[i].Mask.Size()
+			cand = &pfxs[i]
+			continue
+		}
+		m, _ := pfxs[i].Mask.Size()
+		if m > l {
+			l = m
+			cand = &pfxs[i]
+			continue
+		}
+	}
+	if l > 0 {
+		return l
+	}
+	if ip.To4() != nil {
+		return 8 * IPv4len
+	}
+	return 8 * IPv6len
 }

 // interfaceMulticastAddrTable returns addresses for a specific
 // interface.
 func interfaceMulticastAddrTable(ifi *Interface) ([]Addr, error) {
-	paddr, err := getAdapters()
+	aas, err := adapterAddresses()
 	if err != nil {
 		return nil, err
 	}
-
 	var ifat []Addr
-	for ; paddr != nil; paddr = paddr.Next {
-		index := paddr.IfIndex
-		if paddr.Ipv6IfIndex != 0 {
-			index = paddr.Ipv6IfIndex
+	for _, aa := range aas {
+		index := aa.IfIndex
+		if index == 0 { // ipv6IfIndex is a sustitute for ifIndex
+			index = aa.Ipv6IfIndex
 		}
 		if ifi == nil || ifi.Index == int(index) {
-			pmul := paddr.FirstMulticastAddress
-			for ; pmul != nil; pmul = pmul.Next {
-				if sa, err := pmul.Address.Sockaddr.Sockaddr(); err == nil {
-					switch sav := sa.(type) {
+			for pmul := aa.FirstMulticastAddress; pmul != nil; pmul = pmul.Next {
+				sa, err := pmul.Address.Sockaddr.Sockaddr()
+				if err != nil {
+					return nil, os.NewSyscallError("sockaddr", err)
+				}
+				switch sa := sa.(type) {
 				case *syscall.SockaddrInet4:
 					ifa := &IPAddr{IP: make(IP, IPv4len)}
-						copy(ifa.IP, sav.Addr[:])
+					copy(ifa.IP, sa.Addr[:])
 					ifat = append(ifat, ifa)
 				case *syscall.SockaddrInet6:
 					ifa := &IPAddr{IP: make(IP, IPv6len)}
-						copy(ifa.IP, sav.Addr[:])
+					copy(ifa.IP, sa.Addr[:])
 					ifat = append(ifat, ifa)
 				}
 			}
 		}
 	}
-	}
-
 	return ifat, nil
 }
--- a/src/net/interface_windows_test.go
+++ b/src/net/interface_windows_test.go
@ -0,0 +1,132 @@
+// Copyright 2015 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 net
+
+import (
+	"bytes"
+	"internal/syscall/windows"
+	"sort"
+	"testing"
+)
+
+func TestWindowsInterfaces(t *testing.T) {
+	aas, err := adapterAddresses()
+	if err != nil {
+		t.Fatal(err)
+	}
+	ift, err := Interfaces()
+	if err != nil {
+		t.Fatal(err)
+	}
+	for i, ifi := range ift {
+		aa := aas[i]
+		if len(ifi.HardwareAddr) != int(aa.PhysicalAddressLength) {
+			t.Errorf("got %d; want %d", len(ifi.HardwareAddr), aa.PhysicalAddressLength)
+		}
+		if ifi.MTU > 0x7fffffff {
+			t.Errorf("%s: got %d; want less than or equal to 1<<31 - 1", ifi.Name, ifi.MTU)
+		}
+		if ifi.Flags&FlagUp != 0 && aa.OperStatus != windows.IfOperStatusUp {
+			t.Errorf("%s: got %v; should not include FlagUp", ifi.Name, ifi.Flags)
+		}
+		if ifi.Flags&FlagLoopback != 0 && aa.IfType != windows.IF_TYPE_SOFTWARE_LOOPBACK {
+			t.Errorf("%s: got %v; should not include FlagLoopback", ifi.Name, ifi.Flags)
+		}
+		if _, _, err := addrPrefixTable(aa); err != nil {
+			t.Errorf("%s: %v", ifi.Name, err)
+		}
+	}
+}
+
+type byAddrLen []IPNet
+
+func (ps byAddrLen) Len() int { return len(ps) }
+
+func (ps byAddrLen) Less(i, j int) bool {
+	if n := bytes.Compare(ps[i].IP, ps[j].IP); n != 0 {
+		return n < 0
+	}
+	if n := bytes.Compare(ps[i].Mask, ps[j].Mask); n != 0 {
+		return n < 0
+	}
+	return false
+}
+
+func (ps byAddrLen) Swap(i, j int) { ps[i], ps[j] = ps[j], ps[i] }
+
+var windowsAddrPrefixLenTests = []struct {
+	pfxs []IPNet
+	ip   IP
+	out  int
+}{
+	{
+		[]IPNet{
+			{IP: IPv4(172, 16, 0, 0), Mask: IPv4Mask(255, 255, 0, 0)},
+			{IP: IPv4(192, 168, 0, 0), Mask: IPv4Mask(255, 255, 255, 0)},
+			{IP: IPv4(192, 168, 0, 0), Mask: IPv4Mask(255, 255, 255, 128)},
+			{IP: IPv4(192, 168, 0, 0), Mask: IPv4Mask(255, 255, 255, 192)},
+		},
+		IPv4(192, 168, 0, 1),
+		26,
+	},
+	{
+		[]IPNet{
+			{IP: ParseIP("2001:db8::"), Mask: IPMask(ParseIP("ffff:ffff:ffff:ffff:ffff:ffff:ffff:fff0"))},
+			{IP: ParseIP("2001:db8::"), Mask: IPMask(ParseIP("ffff:ffff:ffff:ffff:ffff:ffff:ffff:fff8"))},
+			{IP: ParseIP("2001:db8::"), Mask: IPMask(ParseIP("ffff:ffff:ffff:ffff:ffff:ffff:ffff:fffc"))},
+		},
+		ParseIP("2001:db8::1"),
+		126,
+	},
+
+	// Fallback cases. It may happen on Windows XP or 2003 server.
+	{
+		[]IPNet{
+			{IP: IPv4(127, 0, 0, 0).To4(), Mask: IPv4Mask(255, 0, 0, 0)},
+			{IP: IPv4(10, 0, 0, 0).To4(), Mask: IPv4Mask(255, 0, 0, 0)},
+			{IP: IPv4(172, 16, 0, 0).To4(), Mask: IPv4Mask(255, 255, 0, 0)},
+			{IP: IPv4(192, 168, 255, 0), Mask: IPv4Mask(255, 255, 255, 0)},
+			{IP: IPv4zero, Mask: IPv4Mask(0, 0, 0, 0)},
+		},
+		IPv4(192, 168, 0, 1),
+		8 * IPv4len,
+	},
+	{
+		nil,
+		IPv4(192, 168, 0, 1),
+		8 * IPv4len,
+	},
+	{
+		[]IPNet{
+			{IP: IPv6loopback, Mask: IPMask(ParseIP("ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff"))},
+			{IP: ParseIP("2001:db8:1::"), Mask: IPMask(ParseIP("ffff:ffff:ffff:ffff:ffff:ffff:ffff:fff0"))},
+			{IP: ParseIP("2001:db8:2::"), Mask: IPMask(ParseIP("ffff:ffff:ffff:ffff:ffff:ffff:ffff:fff8"))},
+			{IP: ParseIP("2001:db8:3::"), Mask: IPMask(ParseIP("ffff:ffff:ffff:ffff:ffff:ffff:ffff:fffc"))},
+			{IP: IPv6unspecified, Mask: IPMask(ParseIP("::"))},
+		},
+		ParseIP("2001:db8::1"),
+		8 * IPv6len,
+	},
+	{
+		nil,
+		ParseIP("2001:db8::1"),
+		8 * IPv6len,
+	},
+}
+
+func TestWindowsAddrPrefixLen(t *testing.T) {
+	for i, tt := range windowsAddrPrefixLenTests {
+		sort.Sort(byAddrLen(tt.pfxs))
+		l := addrPrefixLen(tt.pfxs, tt.ip)
+		if l != tt.out {
+			t.Errorf("#%d: got %d; want %d", i, l, tt.out)
+		}
+		sort.Sort(sort.Reverse(byAddrLen(tt.pfxs)))
+		l = addrPrefixLen(tt.pfxs, tt.ip)
+		if l != tt.out {
+			t.Errorf("#%d: got %d; want %d", i, l, tt.out)
+		}
+	}
+}
--- a/src/net/net_windows_test.go
+++ b/src/net/net_windows_test.go
@ -315,13 +315,12 @@ func netshInterfaceIPv6ShowAddress(name string) ([]string, error) {
 		}
 		// remove scope ID if present
 		f = bytes.Split(f[1], []byte{'%'})
-		addrs = append(addrs, string(bytes.TrimSpace(f[0])))
+		addrs = append(addrs, string(bytes.ToLower(bytes.TrimSpace(f[0]))))
 	}
 	return addrs, nil
 }

 func TestInterfaceAddrsWithNetsh(t *testing.T) {
-	t.Skip("skipping test; see https://golang.org/issue/12811")
 	if isWindowsXP(t) {
 		t.Skip("Windows XP netsh command does not provide required functionality")
 	}
@ -375,7 +374,6 @@ func TestInterfaceAddrsWithNetsh(t *testing.T) {
 }

 func TestInterfaceHardwareAddrWithGetmac(t *testing.T) {
-	t.Skip("skipping test; see https://golang.org/issue/12691")
 	if isWindowsXP(t) {
 		t.Skip("Windows XP does not have powershell command")
 	}
@ -386,7 +384,7 @@ func TestInterfaceHardwareAddrWithGetmac(t *testing.T) {
 	have := make([]string, 0)
 	for _, ifi := range ift {
 		if ifi.Flags&FlagLoopback != 0 {
-			// no MAC for loopback interfaces
+			// no MAC address for loopback interfaces
 			continue
 		}
 		have = append(have, ifi.Name+"="+ifi.HardwareAddr.String())
@ -436,7 +434,7 @@ func TestInterfaceHardwareAddrWithGetmac(t *testing.T) {
 			if len(f) != 2 {
 				t.Fatal("unexpected \"Physical Address\" line: %q", line)
 			}
-			addr := string(bytes.TrimSpace(f[1]))
+			addr := string(bytes.ToLower(bytes.TrimSpace(f[1])))
 			if addr == "" {
 				t.Fatal("empty address on \"Physical Address\" line: %q", line)
 			}