net, syscall: more accurate parsers for routing messages on BSD variants

This changes fixes two issues with regard to handling routing messages
as follows:
- Misparsing on platforms (such as FreeBSD) supporting multiple
  architectures in the same kernel (kern.supported_archs="amd64 i386")
- Misparsing with unimplemented messages such as route, interface
  address state notifications

To fix those issues, this change implements all the required socket
address parsers, adds a processor architecture identifying function to
FreeBSD and tests.

Fixes #9707.
Fixes #8203.

Change-Id: I7ed7b4a0b6f10f54b29edc681a2f35603f2d8d45
Reviewed-on: https://go-review.googlesource.com/4330
Reviewed-by: Ian Lance Taylor <iant@golang.org>

14 files changed, 740 insertions, 250 deletions

diff --git a/src/net/interface_bsd.go b/src/net/interface_bsd.go
index 16775579d0..2f66e4fc31 100644
--- a/src/net/interface_bsd.go
+++ b/src/net/interface_bsd.go
@@ -54,24 +54,22 @@ func newLink(m *syscall.InterfaceMessage) (*Interface, error) {
 		return nil, os.NewSyscallError("route sockaddr", err)
 	}
 	ifi := &Interface{Index: int(m.Header.Index), Flags: linkFlags(m.Header.Flags)}
-	for _, sa := range sas {
-		switch sa := sa.(type) {
-		case *syscall.SockaddrDatalink:
-			// NOTE: SockaddrDatalink.Data is minimum work area,
-			// can be larger.
-			m.Data = m.Data[unsafe.Offsetof(sa.Data):]
-			var name [syscall.IFNAMSIZ]byte
-			for i := 0; i < int(sa.Nlen); i++ {
-				name[i] = byte(m.Data[i])
-			}
-			ifi.Name = string(name[:sa.Nlen])
-			ifi.MTU = int(m.Header.Data.Mtu)
-			addr := make([]byte, sa.Alen)
-			for i := 0; i < int(sa.Alen); i++ {
-				addr[i] = byte(m.Data[int(sa.Nlen)+i])
-			}
-			ifi.HardwareAddr = addr[:sa.Alen]
+	sa, _ := sas[syscall.RTAX_IFP].(*syscall.SockaddrDatalink)
+	if sa != nil {
+		// NOTE: SockaddrDatalink.Data is minimum work area,
+		// can be larger.
+		m.Data = m.Data[unsafe.Offsetof(sa.Data):]
+		var name [syscall.IFNAMSIZ]byte
+		for i := 0; i < int(sa.Nlen); i++ {
+			name[i] = byte(m.Data[i])
 		}
+		ifi.Name = string(name[:sa.Nlen])
+		ifi.MTU = int(m.Header.Data.Mtu)
+		addr := make([]byte, sa.Alen)
+		for i := 0; i < int(sa.Alen); i++ {
+			addr[i] = byte(m.Data[int(sa.Nlen)+i])
+		}
+		ifi.HardwareAddr = addr[:sa.Alen]
 	}
 	return ifi, nil
 }
@@ -144,39 +142,34 @@ func interfaceAddrTable(ifi *Interface) ([]Addr, error) {
 	return ifat, nil
 }
 
-func newAddr(ifi *Interface, m *syscall.InterfaceAddrMessage) (Addr, error) {
+func newAddr(ifi *Interface, m *syscall.InterfaceAddrMessage) (*IPNet, error) {
 	sas, err := syscall.ParseRoutingSockaddr(m)
 	if err != nil {
 		return nil, os.NewSyscallError("route sockaddr", err)
 	}
 	ifa := &IPNet{}
-	for i, sa := range sas {
-		switch sa := sa.(type) {
-		case *syscall.SockaddrInet4:
-			switch i {
-			case 0:
-				ifa.Mask = IPv4Mask(sa.Addr[0], sa.Addr[1], sa.Addr[2], sa.Addr[3])
-			case 1:
-				ifa.IP = IPv4(sa.Addr[0], sa.Addr[1], sa.Addr[2], sa.Addr[3])
-			}
-		case *syscall.SockaddrInet6:
-			switch i {
-			case 0:
-				ifa.Mask = make(IPMask, IPv6len)
-				copy(ifa.Mask, sa.Addr[:])
-			case 1:
-				ifa.IP = make(IP, IPv6len)
-				copy(ifa.IP, sa.Addr[:])
-				// NOTE: KAME based IPv6 protcol stack usually embeds
-				// the interface index in the interface-local or link-
-				// local address as the kernel-internal form.
-				if ifa.IP.IsLinkLocalUnicast() {
-					ifa.IP[2], ifa.IP[3] = 0, 0
-				}
-			}
-		default: // Sockaddrs contain syscall.SockaddrDatalink on NetBSD
-			return nil, nil
+	switch sa := sas[syscall.RTAX_NETMASK].(type) {
+	case *syscall.SockaddrInet4:
+		ifa.Mask = IPv4Mask(sa.Addr[0], sa.Addr[1], sa.Addr[2], sa.Addr[3])
+	case *syscall.SockaddrInet6:
+		ifa.Mask = make(IPMask, IPv6len)
+		copy(ifa.Mask, sa.Addr[:])
+	}
+	switch sa := sas[syscall.RTAX_IFA].(type) {
+	case *syscall.SockaddrInet4:
+		ifa.IP = IPv4(sa.Addr[0], sa.Addr[1], sa.Addr[2], sa.Addr[3])
+	case *syscall.SockaddrInet6:
+		ifa.IP = make(IP, IPv6len)
+		copy(ifa.IP, sa.Addr[:])
+		// NOTE: KAME based IPv6 protcol stack usually embeds
+		// the interface index in the interface-local or
+		// link-local address as the kernel-internal form.
+		if ifa.IP.IsLinkLocalUnicast() {
+			ifa.IP[2], ifa.IP[3] = 0, 0
 		}
 	}
+	if ifa.IP == nil || ifa.Mask == nil {
+		return nil, nil // Sockaddrs contain syscall.SockaddrDatalink on NetBSD
+	}
 	return ifa, nil
 }
diff --git a/src/net/interface_darwin.go b/src/net/interface_darwin.go
index ad0937db04..475b8611ce 100644
--- a/src/net/interface_darwin.go
+++ b/src/net/interface_darwin.go
@@ -29,35 +29,34 @@ func interfaceMulticastAddrTable(ifi *Interface) ([]Addr, error) {
 				if err != nil {
 					return nil, err
 				}
-				ifmat = append(ifmat, ifma...)
+				if ifma != nil {
+					ifmat = append(ifmat, ifma)
+				}
 			}
 		}
 	}
 	return ifmat, nil
 }
 
-func newMulticastAddr(ifi *Interface, m *syscall.InterfaceMulticastAddrMessage) ([]Addr, error) {
+func newMulticastAddr(ifi *Interface, m *syscall.InterfaceMulticastAddrMessage) (*IPAddr, error) {
 	sas, err := syscall.ParseRoutingSockaddr(m)
 	if err != nil {
 		return nil, os.NewSyscallError("route sockaddr", err)
 	}
-	var ifmat []Addr
-	for _, sa := range sas {
-		switch sa := sa.(type) {
-		case *syscall.SockaddrInet4:
-			ifma := &IPAddr{IP: IPv4(sa.Addr[0], sa.Addr[1], sa.Addr[2], sa.Addr[3])}
-			ifmat = append(ifmat, ifma.toAddr())
-		case *syscall.SockaddrInet6:
-			ifma := &IPAddr{IP: make(IP, IPv6len)}
-			copy(ifma.IP, sa.Addr[:])
-			// NOTE: KAME based IPv6 protocol stack usually embeds
-			// the interface index in the interface-local or link-
-			// local address as the kernel-internal form.
-			if ifma.IP.IsInterfaceLocalMulticast() || ifma.IP.IsLinkLocalMulticast() {
-				ifma.IP[2], ifma.IP[3] = 0, 0
-			}
-			ifmat = append(ifmat, ifma.toAddr())
+	switch sa := sas[syscall.RTAX_IFA].(type) {
+	case *syscall.SockaddrInet4:
+		return &IPAddr{IP: IPv4(sa.Addr[0], sa.Addr[1], sa.Addr[2], sa.Addr[3])}, nil
+	case *syscall.SockaddrInet6:
+		ifma := IPAddr{IP: make(IP, IPv6len)}
+		copy(ifma.IP, sa.Addr[:])
+		// NOTE: KAME based IPv6 protcol stack usually embeds
+		// the interface index in the interface-local or
+		// link-local address as the kernel-internal form.
+		if ifma.IP.IsInterfaceLocalMulticast() || ifma.IP.IsLinkLocalMulticast() {
+			ifma.IP[2], ifma.IP[3] = 0, 0
 		}
+		return &ifma, nil
+	default:
+		return nil, nil
 	}
-	return ifmat, nil
 }
diff --git a/src/net/interface_freebsd.go b/src/net/interface_freebsd.go
index 5df767910e..13bf438103 100644
--- a/src/net/interface_freebsd.go
+++ b/src/net/interface_freebsd.go
@@ -29,35 +29,34 @@ func interfaceMulticastAddrTable(ifi *Interface) ([]Addr, error) {
 				if err != nil {
 					return nil, err
 				}
-				ifmat = append(ifmat, ifma...)
+				if ifma != nil {
+					ifmat = append(ifmat, ifma)
+				}
 			}
 		}
 	}
 	return ifmat, nil
 }
 
-func newMulticastAddr(ifi *Interface, m *syscall.InterfaceMulticastAddrMessage) ([]Addr, error) {
+func newMulticastAddr(ifi *Interface, m *syscall.InterfaceMulticastAddrMessage) (*IPAddr, error) {
 	sas, err := syscall.ParseRoutingSockaddr(m)
 	if err != nil {
 		return nil, os.NewSyscallError("route sockaddr", err)
 	}
-	var ifmat []Addr
-	for _, sa := range sas {
-		switch sa := sa.(type) {
-		case *syscall.SockaddrInet4:
-			ifma := &IPAddr{IP: IPv4(sa.Addr[0], sa.Addr[1], sa.Addr[2], sa.Addr[3])}
-			ifmat = append(ifmat, ifma.toAddr())
-		case *syscall.SockaddrInet6:
-			ifma := &IPAddr{IP: make(IP, IPv6len)}
-			copy(ifma.IP, sa.Addr[:])
-			// NOTE: KAME based IPv6 protocol stack usually embeds
-			// the interface index in the interface-local or link-
-			// local address as the kernel-internal form.
-			if ifma.IP.IsInterfaceLocalMulticast() || ifma.IP.IsLinkLocalMulticast() {
-				ifma.IP[2], ifma.IP[3] = 0, 0
-			}
-			ifmat = append(ifmat, ifma.toAddr())
+	switch sa := sas[syscall.RTAX_IFA].(type) {
+	case *syscall.SockaddrInet4:
+		return &IPAddr{IP: IPv4(sa.Addr[0], sa.Addr[1], sa.Addr[2], sa.Addr[3])}, nil
+	case *syscall.SockaddrInet6:
+		ifma := IPAddr{IP: make(IP, IPv6len)}
+		copy(ifma.IP, sa.Addr[:])
+		// NOTE: KAME based IPv6 protcol stack usually embeds
+		// the interface index in the interface-local or
+		// link-local address as the kernel-internal form.
+		if ifma.IP.IsInterfaceLocalMulticast() || ifma.IP.IsLinkLocalMulticast() {
+			ifma.IP[2], ifma.IP[3] = 0, 0
 		}
+		return &ifma, nil
+	default:
+		return nil, nil
 	}
-	return ifmat, nil
 }
diff --git a/src/syscall/route_bsd.go b/src/syscall/route_bsd.go
index 1dabe42531..bc5de69bed 100644
--- a/src/syscall/route_bsd.go
+++ b/src/syscall/route_bsd.go
@@ -4,23 +4,37 @@
 
 // +build darwin dragonfly freebsd netbsd openbsd
 
-// Routing sockets and messages
-
 package syscall
 
-import "unsafe"
+import (
+	"runtime"
+	"unsafe"
+)
+
+var (
+	freebsdConfArch       string // "machine $arch" line in kern.conftxt on freebsd
+	minRoutingSockaddrLen = rsaAlignOf(0)
+)
 
 // Round the length of a raw sockaddr up to align it properly.
 func rsaAlignOf(salen int) int {
 	salign := sizeofPtr
-	// NOTE: It seems like 64-bit Darwin kernel still requires
-	// 32-bit aligned access to BSD subsystem. Also NetBSD 6
-	// kernel and beyond require 64-bit aligned access to routing
-	// facilities.
 	if darwin64Bit {
+		// Darwin kernels require 32-bit aligned access to
+		// routing facilities.
 		salign = 4
 	} else if netbsd32Bit {
+		// NetBSD 6 and beyond kernels require 64-bit aligned
+		// access to routing facilities.
 		salign = 8
+	} else if runtime.GOOS == "freebsd" {
+		// In the case of kern.supported_archs="amd64 i386",
+		// we need to know the underlying kernel's
+		// architecture because the alignment for routing
+		// facilities are set at the build time of the kernel.
+		if freebsdConfArch == "amd64" {
+			salign = 8
+		}
 	}
 	if salen == 0 {
 		return salign
@@ -28,6 +42,124 @@ func rsaAlignOf(salen int) int {
 	return (salen + salign - 1) & ^(salign - 1)
 }
 
+// parseSockaddrLink parses b as a datalink socket address.
+func parseSockaddrLink(b []byte) (*SockaddrDatalink, error) {
+	sa, _, err := parseLinkLayerAddr(b[4:])
+	if err != nil {
+		return nil, err
+	}
+	rsa := (*RawSockaddrDatalink)(unsafe.Pointer(&b[0]))
+	sa.Len = rsa.Len
+	sa.Family = rsa.Family
+	sa.Index = rsa.Index
+	return sa, nil
+}
+
+// parseLinkLayerAddr parses b as a datalink socket address in
+// conventional BSD kernel form.
+func parseLinkLayerAddr(b []byte) (*SockaddrDatalink, int, error) {
+	// The encoding looks like the follwoing:
+	// +----------------------------+
+	// | Type             (1 octet) |
+	// +----------------------------+
+	// | Name length      (1 octet) |
+	// +----------------------------+
+	// | Address length   (1 octet) |
+	// +----------------------------+
+	// | Selector length  (1 octet) |
+	// +----------------------------+
+	// | Data            (variable) |
+	// +----------------------------+
+	type linkLayerAddr struct {
+		Type byte
+		Nlen byte
+		Alen byte
+		Slen byte
+	}
+	lla := (*linkLayerAddr)(unsafe.Pointer(&b[0]))
+	l := rsaAlignOf(int(4 + lla.Nlen + lla.Alen + lla.Slen))
+	if len(b) < l {
+		return nil, 0, EINVAL
+	}
+	b = b[4:]
+	sa := &SockaddrDatalink{Type: lla.Type, Nlen: lla.Nlen, Alen: lla.Alen, Slen: lla.Slen}
+	for i := 0; len(sa.Data) > i && i < int(lla.Nlen+lla.Alen+lla.Slen); i++ {
+		sa.Data[i] = int8(b[i])
+	}
+	return sa, l, nil
+}
+
+// parseSockaddrInet parses b as an internet socket address.
+func parseSockaddrInet(b []byte, family byte) (Sockaddr, error) {
+	switch family {
+	case AF_INET:
+		if len(b) < SizeofSockaddrInet4 {
+			return nil, EINVAL
+		}
+		rsa := (*RawSockaddrAny)(unsafe.Pointer(&b[0]))
+		return anyToSockaddr(rsa)
+	case AF_INET6:
+		if len(b) < SizeofSockaddrInet6 {
+			return nil, EINVAL
+		}
+		rsa := (*RawSockaddrAny)(unsafe.Pointer(&b[0]))
+		return anyToSockaddr(rsa)
+	default:
+		return nil, EINVAL
+	}
+}
+
+const (
+	offsetofInet4 = int(unsafe.Offsetof(RawSockaddrInet4{}.Addr))
+	offsetofInet6 = int(unsafe.Offsetof(RawSockaddrInet6{}.Addr))
+)
+
+// parseNetworkLayerAddr parses b as an internet socket address in
+// conventional BSD kernel form.
+func parseNetworkLayerAddr(b []byte, family byte) (Sockaddr, error) {
+	// The encoding looks similar to the NLRI encoding.
+	// +----------------------------+
+	// | Length           (1 octet) |
+	// +----------------------------+
+	// | Address prefix  (variable) |
+	// +----------------------------+
+	//
+	// The differences between the kernel form and the NLRI
+	// encoding are:
+	//
+	// - The length field of the kernel form indicates the prefix
+	//   length in bytes, not in bits
+	//
+	// - In the kernel form, zero value of the length field
+	//   doesn't mean 0.0.0.0/0 or ::/0
+	//
+	// - The kernel form appends leading bytes to the prefix field
+	//   to make the <length, prefix> tuple to be conformed with
+	//   the routing messeage boundary
+	l := int(rsaAlignOf(int(b[0])))
+	if len(b) < l {
+		return nil, EINVAL
+	}
+	switch family {
+	case AF_INET6:
+		sa := &SockaddrInet6{}
+		if l-1 < offsetofInet6 {
+			copy(sa.Addr[:], b[1:l])
+		} else {
+			copy(sa.Addr[:], b[l-offsetofInet6:l])
+		}
+		return sa, nil
+	default: // an old fashion, AF_UNSPEC or unknown means AF_INET
+		sa := &SockaddrInet4{}
+		if l-1 < offsetofInet4 {
+			copy(sa.Addr[:], b[1:l])
+		} else {
+			copy(sa.Addr[:], b[l-offsetofInet4:l])
+		}
+		return sa, nil
+	}
+}
+
 // RouteRIB returns routing information base, as known as RIB,
 // which consists of network facility information, states and
 // parameters.
@@ -50,7 +182,7 @@ func RouteRIB(facility, param int) ([]byte, error) {
 
 // RoutingMessage represents a routing message.
 type RoutingMessage interface {
-	sockaddr() []Sockaddr
+	sockaddr() ([]Sockaddr, error)
 }
 
 const anyMessageLen = int(unsafe.Sizeof(anyMessage{}))
@@ -68,50 +200,41 @@ type RouteMessage struct {
 	Data   []byte
 }
 
-const rtaRtMask = RTA_DST | RTA_GATEWAY | RTA_NETMASK | RTA_GENMASK
-
-func (m *RouteMessage) sockaddr() []Sockaddr {
-	var (
-		af  int
-		sas [4]Sockaddr
-	)
+func (m *RouteMessage) sockaddr() ([]Sockaddr, error) {
+	var sas [RTAX_MAX]Sockaddr
 	b := m.Data[:]
-	for i := uint(0); i < RTAX_MAX; i++ {
-		if m.Header.Addrs&rtaRtMask&(1<<i) == 0 {
+	family := uint8(AF_UNSPEC)
+	for i := uint(0); i < RTAX_MAX && len(b) >= minRoutingSockaddrLen; i++ {
+		if m.Header.Addrs&(1<<i) == 0 {
 			continue
 		}
 		rsa := (*RawSockaddr)(unsafe.Pointer(&b[0]))
-		switch i {
-		case RTAX_DST, RTAX_GATEWAY:
-			sa, err := anyToSockaddr((*RawSockaddrAny)(unsafe.Pointer(rsa)))
+		switch rsa.Family {
+		case AF_LINK:
+			sa, err := parseSockaddrLink(b)
 			if err != nil {
-				return nil
+				return nil, err
 			}
-			if i == RTAX_DST {
-				af = int(rsa.Family)
+			sas[i] = sa
+			b = b[rsaAlignOf(int(rsa.Len)):]
+		case AF_INET, AF_INET6:
+			sa, err := parseSockaddrInet(b, rsa.Family)
+			if err != nil {
+				return nil, err
 			}
 			sas[i] = sa
-		case RTAX_NETMASK, RTAX_GENMASK:
-			switch af {
-			case AF_INET:
-				rsa4 := (*RawSockaddrInet4)(unsafe.Pointer(&b[0]))
-				sa := new(SockaddrInet4)
-				for j := 0; rsa4.Len > 0 && j < int(rsa4.Len)-int(unsafe.Offsetof(rsa4.Addr)); j++ {
-					sa.Addr[j] = rsa4.Addr[j]
-				}
-				sas[i] = sa
-			case AF_INET6:
-				rsa6 := (*RawSockaddrInet6)(unsafe.Pointer(&b[0]))
-				sa := new(SockaddrInet6)
-				for j := 0; rsa6.Len > 0 && j < int(rsa6.Len)-int(unsafe.Offsetof(rsa6.Addr)); j++ {
-					sa.Addr[j] = rsa6.Addr[j]
-				}
-				sas[i] = sa
+			b = b[rsaAlignOf(int(rsa.Len)):]
+			family = rsa.Family
+		default:
+			sa, err := parseNetworkLayerAddr(b, family)
+			if err != nil {
+				return nil, err
 			}
+			sas[i] = sa
+			b = b[rsaAlignOf(int(b[0])):]
 		}
-		b = b[rsaAlignOf(int(rsa.Len)):]
 	}
-	return sas[:]
+	return sas[:], nil
 }
 
 // InterfaceMessage represents a routing message containing
@@ -121,15 +244,17 @@ type InterfaceMessage struct {
 	Data   []byte
 }
 
-func (m *InterfaceMessage) sockaddr() (sas []Sockaddr) {
+func (m *InterfaceMessage) sockaddr() ([]Sockaddr, error) {
+	var sas [RTAX_MAX]Sockaddr
 	if m.Header.Addrs&RTA_IFP == 0 {
-		return nil
+		return nil, nil
 	}
-	sa, err := anyToSockaddr((*RawSockaddrAny)(unsafe.Pointer(&m.Data[0])))
+	sa, err := parseSockaddrLink(m.Data[:])
 	if err != nil {
-		return nil
+		return nil, err
 	}
-	return append(sas, sa)
+	sas[RTAX_IFP] = sa
+	return sas[:], nil
 }
 
 // InterfaceAddrMessage represents a routing message containing
@@ -139,79 +264,63 @@ type InterfaceAddrMessage struct {
 	Data   []byte
 }
 
-const rtaIfaMask = RTA_IFA | RTA_NETMASK | RTA_BRD
-
-func (m *InterfaceAddrMessage) sockaddr() (sas []Sockaddr) {
-	if m.Header.Addrs&rtaIfaMask == 0 {
-		return nil
-	}
+func (m *InterfaceAddrMessage) sockaddr() ([]Sockaddr, error) {
+	var sas [RTAX_MAX]Sockaddr
 	b := m.Data[:]
-	// We still see AF_UNSPEC in socket addresses on some
-	// platforms. To identify each address family correctly, we
-	// will use the address family of RTAX_NETMASK as a preferred
-	// one on the 32-bit NetBSD kernel, also use the length of
-	// RTAX_NETMASK socket address on the FreeBSD kernel.
-	preferredFamily := uint8(AF_UNSPEC)
-	for i := uint(0); i < RTAX_MAX; i++ {
+	family := uint8(AF_UNSPEC)
+	for i := uint(0); i < RTAX_MAX && len(b) >= minRoutingSockaddrLen; i++ {
 		if m.Header.Addrs&(1<<i) == 0 {
 			continue
 		}
 		rsa := (*RawSockaddr)(unsafe.Pointer(&b[0]))
-		switch i {
-		case RTAX_IFA:
-			if rsa.Family == AF_UNSPEC {
-				rsa.Family = preferredFamily
-			}
-			sa, err := anyToSockaddr((*RawSockaddrAny)(unsafe.Pointer(rsa)))
+		switch rsa.Family {
+		case AF_LINK:
+			sa, err := parseSockaddrLink(b)
 			if err != nil {
-				return nil
+				return nil, err
 			}
-			sas = append(sas, sa)
-		case RTAX_NETMASK:
-			switch rsa.Family {
-			case AF_UNSPEC:
-				switch rsa.Len {
-				case SizeofSockaddrInet4:
-					rsa.Family = AF_INET
-				case SizeofSockaddrInet6:
-					rsa.Family = AF_INET6
-				default:
-					rsa.Family = AF_INET // an old fashion, AF_UNSPEC means AF_INET
-				}
-			case AF_INET, AF_INET6:
-				preferredFamily = rsa.Family
-			default:
-				return nil
+			sas[i] = sa
+			b = b[rsaAlignOf(int(rsa.Len)):]
+		case AF_INET, AF_INET6:
+			sa, err := parseSockaddrInet(b, rsa.Family)
+			if err != nil {
+				return nil, err
 			}
-			sa, err := anyToSockaddr((*RawSockaddrAny)(unsafe.Pointer(rsa)))
+			sas[i] = sa
+			b = b[rsaAlignOf(int(rsa.Len)):]
+			family = rsa.Family
+		default:
+			sa, err := parseNetworkLayerAddr(b, family)
 			if err != nil {
-				return nil
+				return nil, err
 			}
-			sas = append(sas, sa)
-		case RTAX_BRD:
-			// nothing to do
+			sas[i] = sa
+			b = b[rsaAlignOf(int(b[0])):]
 		}
-		b = b[rsaAlignOf(int(rsa.Len)):]
 	}
-	return sas
+	return sas[:], nil
 }
 
 // ParseRoutingMessage parses b as routing messages and returns the
 // slice containing the RoutingMessage interfaces.
 func ParseRoutingMessage(b []byte) (msgs []RoutingMessage, err error) {
-	msgCount := 0
+	nmsgs, nskips := 0, 0
 	for len(b) >= anyMessageLen {
-		msgCount++
+		nmsgs++
 		any := (*anyMessage)(unsafe.Pointer(&b[0]))
 		if any.Version != RTM_VERSION {
 			b = b[any.Msglen:]
 			continue
 		}
-		msgs = append(msgs, any.toRoutingMessage(b))
+		if m := any.toRoutingMessage(b); m == nil {
+			nskips++
+		} else {
+			msgs = append(msgs, m)
+		}
 		b = b[any.Msglen:]
 	}
 	// We failed to parse any of the messages - version mismatch?
-	if msgCount > 0 && len(msgs) == 0 {
+	if nmsgs != len(msgs)+nskips {
 		return nil, EINVAL
 	}
 	return msgs, nil
@@ -219,6 +328,10 @@ func ParseRoutingMessage(b []byte) (msgs []RoutingMessage, err error) {
 
 // ParseRoutingMessage parses msg's payload as raw sockaddrs and
 // returns the slice containing the Sockaddr interfaces.
-func ParseRoutingSockaddr(msg RoutingMessage) (sas []Sockaddr, err error) {
-	return append(sas, msg.sockaddr()...), nil
+func ParseRoutingSockaddr(msg RoutingMessage) ([]Sockaddr, error) {
+	sas, err := msg.sockaddr()
+	if err != nil {
+		return nil, err
+	}
+	return sas, nil
 }
diff --git a/src/syscall/route_bsd_test.go b/src/syscall/route_bsd_test.go
new file mode 100644
index 0000000000..471f4a25a5
--- /dev/null
+++ b/src/syscall/route_bsd_test.go
@@ -0,0 +1,197 @@
+// 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.
+
+// +build darwin dragonfly freebsd netbsd openbsd
+
+package syscall_test
+
+import (
+	"fmt"
+	"net"
+	"os"
+	"syscall"
+	"testing"
+	"time"
+)
+
+func TestRouteRIB(t *testing.T) {
+	for _, facility := range []int{syscall.NET_RT_DUMP, syscall.NET_RT_IFLIST} {
+		for _, param := range []int{syscall.AF_UNSPEC, syscall.AF_INET, syscall.AF_INET6} {
+			b, err := syscall.RouteRIB(facility, param)
+			if err != nil {
+				t.Error(facility, param, err)
+				continue
+			}
+			msgs, err := syscall.ParseRoutingMessage(b)
+			if err != nil {
+				t.Error(facility, param, err)
+				continue
+			}
+			var ipv4loopback, ipv6loopback bool
+			for _, m := range msgs {
+				flags, err := parseRoutingMessageHeader(m)
+				if err != nil {
+					t.Error(err)
+					continue
+				}
+				sas, err := parseRoutingSockaddrs(m)
+				if err != nil {
+					t.Error(err)
+					continue
+				}
+				if flags&(syscall.RTA_DST|syscall.RTA_IFA) != 0 {
+					sa := sas[syscall.RTAX_DST]
+					if sa == nil {
+						sa = sas[syscall.RTAX_IFA]
+					}
+					switch sa := sa.(type) {
+					case *syscall.SockaddrInet4:
+						if net.IP(sa.Addr[:]).IsLoopback() {
+							ipv4loopback = true
+						}
+					case *syscall.SockaddrInet6:
+						if net.IP(sa.Addr[:]).IsLoopback() {
+							ipv6loopback = true
+						}
+					}
+				}
+				t.Log(facility, param, flags, sockaddrs(sas))
+			}
+			if param == syscall.AF_UNSPEC && len(msgs) > 0 && !ipv4loopback && !ipv6loopback {
+				t.Errorf("no loopback facility found: ipv4/ipv6=%v/%v, %v", ipv4loopback, ipv6loopback, len(msgs))
+				continue
+			}
+		}
+	}
+}
+
+func TestRouteMonitor(t *testing.T) {
+	if testing.Short() || os.Getuid() != 0 {
+		t.Skip("must be root")
+	}
+
+	s, err := syscall.Socket(syscall.AF_ROUTE, syscall.SOCK_RAW, syscall.AF_UNSPEC)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer syscall.Close(s)
+
+	tmo := time.After(30 * time.Second)
+	go func() {
+		b := make([]byte, os.Getpagesize())
+		for {
+			n, err := syscall.Read(s, b)
+			if err != nil {
+				return
+			}
+			msgs, err := syscall.ParseRoutingMessage(b[:n])
+			if err != nil {
+				t.Error(err)
+				return
+			}
+			for _, m := range msgs {
+				flags, err := parseRoutingMessageHeader(m)
+				if err != nil {
+					t.Error(err)
+					continue
+				}
+				sas, err := parseRoutingSockaddrs(m)
+				if err != nil {
+					t.Error(err)
+					continue
+				}
+				t.Log(flags, sockaddrs(sas))
+			}
+		}
+	}()
+	<-tmo
+}
+
+type addrFamily byte
+
+func (f addrFamily) String() string {
+	switch f {
+	case syscall.AF_UNSPEC:
+		return "unspec"
+	case syscall.AF_LINK:
+		return "link"
+	case syscall.AF_INET:
+		return "inet4"
+	case syscall.AF_INET6:
+		return "inet6"
+	default:
+		return fmt.Sprintf("unknown %d", f)
+	}
+}
+
+type addrFlags uint32
+
+var addrFlagNames = [...]string{
+	"dst",
+	"gateway",
+	"netmask",
+	"genmask",
+	"ifp",
+	"ifa",
+	"author",
+	"brd",
+	"mpls1,tag,src", // sockaddr_mpls=dragonfly,netbsd, sockaddr_in/in6=openbsd
+	"mpls2,srcmask", // sockaddr_mpls=dragonfly, sockaddr_in/in6=openbsd
+	"mpls3,label",   // sockaddr_mpls=dragonfly, sockaddr_rtlabel=openbsd
+}
+
+func (f addrFlags) String() string {
+	var s string
+	for i, name := range addrFlagNames {
+		if f&(1<<uint(i)) != 0 {
+			if s != "" {
+				s += "|"
+			}
+			s += name
+		}
+	}
+	if s == "" {
+		return "<nil>"
+	}
+	return s
+}
+
+type sockaddrs []syscall.Sockaddr
+
+func (sas sockaddrs) String() string {
+	var s string
+	for _, sa := range sas {
+		if sa == nil {
+			continue
+		}
+		if len(s) > 0 {
+			s += " "
+		}
+		switch sa := sa.(type) {
+		case *syscall.SockaddrDatalink:
+			s += fmt.Sprintf("[%v/%v/%v t/n/a/s=%v/%v/%v/%v]", sa.Len, addrFamily(sa.Family), sa.Index, sa.Type, sa.Nlen, sa.Alen, sa.Slen)
+		case *syscall.SockaddrInet4:
+			s += fmt.Sprintf("%v", net.IP(sa.Addr[:]).To4())
+		case *syscall.SockaddrInet6:
+			s += fmt.Sprintf("%v", net.IP(sa.Addr[:]).To16())
+		}
+	}
+	if s == "" {
+		return "<nil>"
+	}
+	return s
+}
+
+func (sas sockaddrs) match(flags addrFlags) error {
+	var f addrFlags
+	for i := range sas {
+		if sas[i] != nil {
+			f |= 1 << uint(i)
+		}
+	}
+	if f != flags {
+		return fmt.Errorf("got %v; want %v", f, flags)
+	}
+	return nil
+}
diff --git a/src/syscall/route_darwin.go b/src/syscall/route_darwin.go
index ad27907230..89bca12f3e 100644
--- a/src/syscall/route_darwin.go
+++ b/src/syscall/route_darwin.go
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// Routing sockets and messages for Darwin
-
 package syscall
 
 import "unsafe"
@@ -33,29 +31,37 @@ type InterfaceMulticastAddrMessage struct {
 	Data   []byte
 }
 
-const rtaIfmaMask = RTA_GATEWAY | RTA_IFP | RTA_IFA
-
-func (m *InterfaceMulticastAddrMessage) sockaddr() (sas []Sockaddr) {
-	if m.Header.Addrs&rtaIfmaMask == 0 {
-		return nil
-	}
+func (m *InterfaceMulticastAddrMessage) sockaddr() ([]Sockaddr, error) {
+	var sas [RTAX_MAX]Sockaddr
 	b := m.Data[:]
-	for i := uint(0); i < RTAX_MAX; i++ {
-		if m.Header.Addrs&rtaIfmaMask&(1<<i) == 0 {
+	for i := uint(0); i < RTAX_MAX && len(b) >= minRoutingSockaddrLen; i++ {
+		if m.Header.Addrs&(1<<i) == 0 {
 			continue
 		}
 		rsa := (*RawSockaddr)(unsafe.Pointer(&b[0]))
-		switch i {
-		case RTAX_IFA:
-			sa, e := anyToSockaddr((*RawSockaddrAny)(unsafe.Pointer(rsa)))
-			if e != nil {
-				return nil
+		switch rsa.Family {
+		case AF_LINK:
+			sa, err := parseSockaddrLink(b)
+			if err != nil {
+				return nil, err
+			}
+			sas[i] = sa
+			b = b[rsaAlignOf(int(rsa.Len)):]
+		case AF_INET, AF_INET6:
+			sa, err := parseSockaddrInet(b, rsa.Family)
+			if err != nil {
+				return nil, err
+			}
+			sas[i] = sa
+			b = b[rsaAlignOf(int(rsa.Len)):]
+		default:
+			sa, l, err := parseLinkLayerAddr(b)
+			if err != nil {
+				return nil, err
 			}
-			sas = append(sas, sa)
-		case RTAX_GATEWAY, RTAX_IFP:
-			// nothing to do
+			sas[i] = sa
+			b = b[l:]
 		}
-		b = b[rsaAlignOf(int(rsa.Len)):]
 	}
-	return sas
+	return sas[:], nil
 }
diff --git a/src/syscall/route_dragonfly.go b/src/syscall/route_dragonfly.go
index 79190d2b01..5226f7f2e4 100644
--- a/src/syscall/route_dragonfly.go
+++ b/src/syscall/route_dragonfly.go
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// Routing sockets and messages for Dragonfly
-
 package syscall
 
 import "unsafe"
@@ -12,6 +10,8 @@ func (any *anyMessage) toRoutingMessage(b []byte) RoutingMessage {
 	switch any.Type {
 	case RTM_ADD, RTM_DELETE, RTM_CHANGE, RTM_GET, RTM_LOSING, RTM_REDIRECT, RTM_MISS, RTM_LOCK, RTM_RESOLVE:
 		p := (*RouteMessage)(unsafe.Pointer(any))
+		// We don't support sockaddr_mpls for now.
+		p.Header.Addrs &= RTA_DST | RTA_GATEWAY | RTA_NETMASK | RTA_GENMASK | RTA_IFA | RTA_IFP | RTA_BRD | RTA_AUTHOR
 		return &RouteMessage{Header: p.Header, Data: b[SizeofRtMsghdr:any.Msglen]}
 	case RTM_IFINFO:
 		p := (*InterfaceMessage)(unsafe.Pointer(any))
@@ -35,7 +35,7 @@ type InterfaceAnnounceMessage struct {
 	Header IfAnnounceMsghdr
 }
 
-func (m *InterfaceAnnounceMessage) sockaddr() (sas []Sockaddr) { return nil }
+func (m *InterfaceAnnounceMessage) sockaddr() ([]Sockaddr, error) { return nil, nil }
 
 // InterfaceMulticastAddrMessage represents a routing message
 // containing network interface address entries.
@@ -44,29 +44,37 @@ type InterfaceMulticastAddrMessage struct {
 	Data   []byte
 }
 
-const rtaIfmaMask = RTA_GATEWAY | RTA_IFP | RTA_IFA
-
-func (m *InterfaceMulticastAddrMessage) sockaddr() (sas []Sockaddr) {
-	if m.Header.Addrs&rtaIfmaMask == 0 {
-		return nil
-	}
+func (m *InterfaceMulticastAddrMessage) sockaddr() ([]Sockaddr, error) {
+	var sas [RTAX_MAX]Sockaddr
 	b := m.Data[:]
-	for i := uint(0); i < RTAX_MAX; i++ {
-		if m.Header.Addrs&rtaIfmaMask&(1<<i) == 0 {
+	for i := uint(0); i < RTAX_MAX && len(b) >= minRoutingSockaddrLen; i++ {
+		if m.Header.Addrs&(1<<i) == 0 {
 			continue
 		}
 		rsa := (*RawSockaddr)(unsafe.Pointer(&b[0]))
-		switch i {
-		case RTAX_IFA:
-			sa, e := anyToSockaddr((*RawSockaddrAny)(unsafe.Pointer(rsa)))
-			if e != nil {
-				return nil
+		switch rsa.Family {
+		case AF_LINK:
+			sa, err := parseSockaddrLink(b)
+			if err != nil {
+				return nil, err
+			}
+			sas[i] = sa
+			b = b[rsaAlignOf(int(rsa.Len)):]
+		case AF_INET, AF_INET6:
+			sa, err := parseSockaddrInet(b, rsa.Family)
+			if err != nil {
+				return nil, err
+			}
+			sas[i] = sa
+			b = b[rsaAlignOf(int(rsa.Len)):]
+		default:
+			sa, l, err := parseLinkLayerAddr(b)
+			if err != nil {
+				return nil, err
 			}
-			sas = append(sas, sa)
-		case RTAX_GATEWAY, RTAX_IFP:
-			// nothing to do
+			sas[i] = sa
+			b = b[l:]
 		}
-		b = b[rsaAlignOf(int(rsa.Len)):]
 	}
-	return sas
+	return sas[:], nil
 }
diff --git a/src/syscall/route_freebsd.go b/src/syscall/route_freebsd.go
index 15897b1aca..0e18103855 100644
--- a/src/syscall/route_freebsd.go
+++ b/src/syscall/route_freebsd.go
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// Routing sockets and messages for FreeBSD
-
 package syscall
 
 import "unsafe"
@@ -13,13 +11,31 @@ var freebsdVersion uint32
 
 func init() {
 	freebsdVersion, _ = SysctlUint32("kern.osreldate")
+	conf, _ := Sysctl("kern.conftxt")
+	for i, j := 0, 0; j < len(conf); j++ {
+		if conf[j] != '\n' {
+			continue
+		}
+		s := conf[i:j]
+		i = j + 1
+		if len(s) > len("machine") && s[:len("machine")] == "machine" {
+			s = s[len("machine"):]
+			for k := 0; k < len(s); k++ {
+				if s[k] == ' ' || s[k] == '\t' {
+					s = s[1:]
+				}
+				break
+			}
+			freebsdConfArch = s
+			break
+		}
+	}
 }
 
 func (any *anyMessage) toRoutingMessage(b []byte) RoutingMessage {
 	switch any.Type {
 	case RTM_ADD, RTM_DELETE, RTM_CHANGE, RTM_GET, RTM_LOSING, RTM_REDIRECT, RTM_MISS, RTM_LOCK, RTM_RESOLVE:
-		p := (*RouteMessage)(unsafe.Pointer(any))
-		return &RouteMessage{Header: p.Header, Data: b[SizeofRtMsghdr:any.Msglen]}
+		return any.parseRouteMessage(b)
 	case RTM_IFINFO:
 		return any.parseInterfaceMessage(b)
 	case RTM_IFANNOUNCE:
@@ -41,7 +57,7 @@ type InterfaceAnnounceMessage struct {
 	Header IfAnnounceMsghdr
 }
 
-func (m *InterfaceAnnounceMessage) sockaddr() (sas []Sockaddr) { return nil }
+func (m *InterfaceAnnounceMessage) sockaddr() ([]Sockaddr, error) { return nil, nil }
 
 // InterfaceMulticastAddrMessage represents a routing message
 // containing network interface address entries.
@@ -50,29 +66,37 @@ type InterfaceMulticastAddrMessage struct {
 	Data   []byte
 }
 
-const rtaIfmaMask = RTA_GATEWAY | RTA_IFP | RTA_IFA
-
-func (m *InterfaceMulticastAddrMessage) sockaddr() (sas []Sockaddr) {
-	if m.Header.Addrs&rtaIfmaMask == 0 {
-		return nil
-	}
+func (m *InterfaceMulticastAddrMessage) sockaddr() ([]Sockaddr, error) {
+	var sas [RTAX_MAX]Sockaddr
 	b := m.Data[:]
-	for i := uint(0); i < RTAX_MAX; i++ {
-		if m.Header.Addrs&rtaIfmaMask&(1<<i) == 0 {
+	for i := uint(0); i < RTAX_MAX && len(b) >= minRoutingSockaddrLen; i++ {
+		if m.Header.Addrs&(1<<i) == 0 {
 			continue
 		}
 		rsa := (*RawSockaddr)(unsafe.Pointer(&b[0]))
-		switch i {
-		case RTAX_IFA:
-			sa, e := anyToSockaddr((*RawSockaddrAny)(unsafe.Pointer(rsa)))
-			if e != nil {
-				return nil
+		switch rsa.Family {
+		case AF_LINK:
+			sa, err := parseSockaddrLink(b)
+			if err != nil {
+				return nil, err
+			}
+			sas[i] = sa
+			b = b[rsaAlignOf(int(rsa.Len)):]
+		case AF_INET, AF_INET6:
+			sa, err := parseSockaddrInet(b, rsa.Family)
+			if err != nil {
+				return nil, err
+			}
+			sas[i] = sa
+			b = b[rsaAlignOf(int(rsa.Len)):]
+		default:
+			sa, l, err := parseLinkLayerAddr(b)
+			if err != nil {
+				return nil, err
 			}
-			sas = append(sas, sa)
-		case RTAX_GATEWAY, RTAX_IFP:
-			// nothing to do
+			sas[i] = sa
+			b = b[l:]
 		}
-		b = b[rsaAlignOf(int(rsa.Len)):]
 	}
-	return sas
+	return sas[:], nil
 }
diff --git a/src/syscall/route_freebsd_32bit.go b/src/syscall/route_freebsd_32bit.go
index 93efdddb3b..5c10b05e24 100644
--- a/src/syscall/route_freebsd_32bit.go
+++ b/src/syscall/route_freebsd_32bit.go
@@ -8,6 +8,15 @@ package syscall
 
 import "unsafe"
 
+func (any *anyMessage) parseRouteMessage(b []byte) *RouteMessage {
+	p := (*RouteMessage)(unsafe.Pointer(any))
+	off := int(unsafe.Offsetof(p.Header.Rmx)) + SizeofRtMetrics
+	if freebsdConfArch == "amd64" {
+		off += SizeofRtMetrics // rt_metrics on amd64 is simply doubled
+	}
+	return &RouteMessage{Header: p.Header, Data: b[rsaAlignOf(off):any.Msglen]}
+}
+
 func (any *anyMessage) parseInterfaceMessage(b []byte) *InterfaceMessage {
 	p := (*InterfaceMessage)(unsafe.Pointer(any))
 	// FreeBSD 10 and beyond have a restructured mbuf
@@ -18,7 +27,7 @@ func (any *anyMessage) parseInterfaceMessage(b []byte) *InterfaceMessage {
 		p.Header.Data.Hwassist = uint32(m.Data.Hwassist)
 		p.Header.Data.Epoch = m.Data.Epoch
 		p.Header.Data.Lastchange = m.Data.Lastchange
-		return &InterfaceMessage{Header: p.Header, Data: b[sizeofIfMsghdr:any.Msglen]}
+		return &InterfaceMessage{Header: p.Header, Data: b[int(unsafe.Offsetof(p.Header.Data))+int(p.Header.Data.Datalen) : any.Msglen]}
 	}
-	return &InterfaceMessage{Header: p.Header, Data: b[SizeofIfMsghdr:any.Msglen]}
+	return &InterfaceMessage{Header: p.Header, Data: b[int(unsafe.Offsetof(p.Header.Data))+int(p.Header.Data.Datalen) : any.Msglen]}
 }
diff --git a/src/syscall/route_freebsd_64bit.go b/src/syscall/route_freebsd_64bit.go
index 9377f2fedc..728837ebb5 100644
--- a/src/syscall/route_freebsd_64bit.go
+++ b/src/syscall/route_freebsd_64bit.go
@@ -8,7 +8,12 @@ package syscall
 
 import "unsafe"
 
+func (any *anyMessage) parseRouteMessage(b []byte) *RouteMessage {
+	p := (*RouteMessage)(unsafe.Pointer(any))
+	return &RouteMessage{Header: p.Header, Data: b[rsaAlignOf(int(unsafe.Offsetof(p.Header.Rmx))+SizeofRtMetrics):any.Msglen]}
+}
+
 func (any *anyMessage) parseInterfaceMessage(b []byte) *InterfaceMessage {
 	p := (*InterfaceMessage)(unsafe.Pointer(any))
-	return &InterfaceMessage{Header: p.Header, Data: b[SizeofIfMsghdr:any.Msglen]}
+	return &InterfaceMessage{Header: p.Header, Data: b[int(unsafe.Offsetof(p.Header.Data))+int(p.Header.Data.Datalen) : any.Msglen]}
 }
diff --git a/src/syscall/route_ifma_test.go b/src/syscall/route_ifma_test.go
new file mode 100644
index 0000000000..af2b67dc24
--- /dev/null
+++ b/src/syscall/route_ifma_test.go
@@ -0,0 +1,74 @@
+// 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.
+
+// +build darwin dragonfly freebsd
+
+package syscall_test
+
+import (
+	"fmt"
+	"syscall"
+)
+
+func parseRoutingMessageHeader(m syscall.RoutingMessage) (addrFlags, error) {
+	switch m := m.(type) {
+	case *syscall.RouteMessage:
+		errno := syscall.Errno(uintptr(m.Header.Errno))
+		if errno != 0 {
+			return 0, fmt.Errorf("%T: %v, %#v", m, errno, m.Header)
+		}
+		return addrFlags(m.Header.Addrs), nil
+	case *syscall.InterfaceMessage:
+		return addrFlags(m.Header.Addrs), nil
+	case *syscall.InterfaceAddrMessage:
+		return addrFlags(m.Header.Addrs), nil
+	case *syscall.InterfaceMulticastAddrMessage:
+		return addrFlags(m.Header.Addrs), nil
+	default:
+		panic(fmt.Sprintf("unknown routing message type: %T", m))
+	}
+}
+
+func parseRoutingSockaddrs(m syscall.RoutingMessage) ([]syscall.Sockaddr, error) {
+	switch m := m.(type) {
+	case *syscall.RouteMessage:
+		sas, err := syscall.ParseRoutingSockaddr(m)
+		if err != nil {
+			return nil, fmt.Errorf("%T: %v, %#v", m, err, m.Data)
+		}
+		if err = sockaddrs(sas).match(addrFlags(m.Header.Addrs)); err != nil {
+			return nil, err
+		}
+		return sas, nil
+	case *syscall.InterfaceMessage:
+		sas, err := syscall.ParseRoutingSockaddr(m)
+		if err != nil {
+			return nil, fmt.Errorf("%T: %v, %#v", m, err, m.Data)
+		}
+		if err = sockaddrs(sas).match(addrFlags(m.Header.Addrs)); err != nil {
+			return nil, err
+		}
+		return sas, nil
+	case *syscall.InterfaceAddrMessage:
+		sas, err := syscall.ParseRoutingSockaddr(m)
+		if err != nil {
+			return nil, fmt.Errorf("%T: %v, %#v", m, err, m.Data)
+		}
+		if err = sockaddrs(sas).match(addrFlags(m.Header.Addrs)); err != nil {
+			return nil, err
+		}
+		return sas, nil
+	case *syscall.InterfaceMulticastAddrMessage:
+		sas, err := syscall.ParseRoutingSockaddr(m)
+		if err != nil {
+			return nil, fmt.Errorf("%T: %v, %#v", m, err, m.Data)
+		}
+		if err = sockaddrs(sas).match(addrFlags(m.Header.Addrs)); err != nil {
+			return nil, err
+		}
+		return sas, nil
+	default:
+		panic(fmt.Sprintf("unknown routing message type: %T", m))
+	}
+}
diff --git a/src/syscall/route_netbsd.go b/src/syscall/route_netbsd.go
index 9883aebaf5..d605ffa30f 100644
--- a/src/syscall/route_netbsd.go
+++ b/src/syscall/route_netbsd.go
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// Routing sockets and messages for NetBSD
-
 package syscall
 
 import "unsafe"
@@ -12,6 +10,8 @@ func (any *anyMessage) toRoutingMessage(b []byte) RoutingMessage {
 	switch any.Type {
 	case RTM_ADD, RTM_DELETE, RTM_CHANGE, RTM_GET, RTM_LOSING, RTM_REDIRECT, RTM_MISS, RTM_LOCK, RTM_RESOLVE:
 		p := (*RouteMessage)(unsafe.Pointer(any))
+		// We don't support sockaddr_mpls for now.
+		p.Header.Addrs &= RTA_DST | RTA_GATEWAY | RTA_NETMASK | RTA_GENMASK | RTA_IFA | RTA_IFP | RTA_BRD | RTA_AUTHOR
 		return &RouteMessage{Header: p.Header, Data: b[SizeofRtMsghdr:any.Msglen]}
 	case RTM_IFINFO:
 		p := (*InterfaceMessage)(unsafe.Pointer(any))
@@ -32,4 +32,4 @@ type InterfaceAnnounceMessage struct {
 	Header IfAnnounceMsghdr
 }
 
-func (m *InterfaceAnnounceMessage) sockaddr() (sas []Sockaddr) { return nil }
+func (m *InterfaceAnnounceMessage) sockaddr() ([]Sockaddr, error) { return nil, nil }
diff --git a/src/syscall/route_noifma_test.go b/src/syscall/route_noifma_test.go
new file mode 100644
index 0000000000..19d5d8ebbf
--- /dev/null
+++ b/src/syscall/route_noifma_test.go
@@ -0,0 +1,63 @@
+// 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.
+
+// +build netbsd openbsd
+
+package syscall_test
+
+import (
+	"fmt"
+	"syscall"
+)
+
+func parseRoutingMessageHeader(m syscall.RoutingMessage) (addrFlags, error) {
+	switch m := m.(type) {
+	case *syscall.RouteMessage:
+		errno := syscall.Errno(uintptr(m.Header.Errno))
+		if errno != 0 {
+			return 0, fmt.Errorf("%T: %v, %#v", m, errno, m.Header)
+		}
+		return addrFlags(m.Header.Addrs), nil
+	case *syscall.InterfaceMessage:
+		return addrFlags(m.Header.Addrs), nil
+	case *syscall.InterfaceAddrMessage:
+		return addrFlags(m.Header.Addrs), nil
+	default:
+		panic(fmt.Sprintf("unknown routing message type: %T", m))
+	}
+}
+
+func parseRoutingSockaddrs(m syscall.RoutingMessage) ([]syscall.Sockaddr, error) {
+	switch m := m.(type) {
+	case *syscall.RouteMessage:
+		sas, err := syscall.ParseRoutingSockaddr(m)
+		if err != nil {
+			return nil, fmt.Errorf("%T: %v, %#v", m, err, m.Data)
+		}
+		if err = sockaddrs(sas).match(addrFlags(m.Header.Addrs)); err != nil {
+			return nil, err
+		}
+		return sas, nil
+	case *syscall.InterfaceMessage:
+		sas, err := syscall.ParseRoutingSockaddr(m)
+		if err != nil {
+			return nil, fmt.Errorf("%T: %v, %#v", m, err, m.Data)
+		}
+		if err = sockaddrs(sas).match(addrFlags(m.Header.Addrs)); err != nil {
+			return nil, err
+		}
+		return sas, nil
+	case *syscall.InterfaceAddrMessage:
+		sas, err := syscall.ParseRoutingSockaddr(m)
+		if err != nil {
+			return nil, fmt.Errorf("%T: %v, %#v", m, err, m.Data)
+		}
+		if err = sockaddrs(sas).match(addrFlags(m.Header.Addrs)); err != nil {
+			return nil, err
+		}
+		return sas, nil
+	default:
+		panic(fmt.Sprintf("unknown routing message type: %T", m))
+	}
+}
diff --git a/src/syscall/route_openbsd.go b/src/syscall/route_openbsd.go
index e5086400c5..7804a08910 100644
--- a/src/syscall/route_openbsd.go
+++ b/src/syscall/route_openbsd.go
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// Routing sockets and messages for OpenBSD
-
 package syscall
 
 import "unsafe"
@@ -12,6 +10,8 @@ func (any *anyMessage) toRoutingMessage(b []byte) RoutingMessage {
 	switch any.Type {
 	case RTM_ADD, RTM_DELETE, RTM_CHANGE, RTM_GET, RTM_LOSING, RTM_REDIRECT, RTM_MISS, RTM_LOCK, RTM_RESOLVE:
 		p := (*RouteMessage)(unsafe.Pointer(any))
+		// We don't support sockaddr_rtlabel for now.
+		p.Header.Addrs &= RTA_DST | RTA_GATEWAY | RTA_NETMASK | RTA_GENMASK | RTA_IFA | RTA_IFP | RTA_BRD | RTA_AUTHOR | RTA_SRC | RTA_SRCMASK
 		return &RouteMessage{Header: p.Header, Data: b[p.Header.Hdrlen:any.Msglen]}
 	case RTM_IFINFO:
 		p := (*InterfaceMessage)(unsafe.Pointer(any))
@@ -32,4 +32,4 @@ type InterfaceAnnounceMessage struct {
 	Header IfAnnounceMsghdr
 }
 
-func (m *InterfaceAnnounceMessage) sockaddr() (sas []Sockaddr) { return nil }
+func (m *InterfaceAnnounceMessage) sockaddr() ([]Sockaddr, error) { return nil, nil }