syscall: update routing socket parser for NetBSD 6 and beyond

NetBSD 6 kernel and beyond require 64-bit aligned access to routing
facilities.

Fixes #6226.

R=golang-dev, bsiegert, bradfitz
CC=golang-dev
https://golang.org/cl/13170043

src/pkg/net/interface_test.go

@@ -109,14 +109,14 @@ func testAddrs(t *testing.T, ifat []Addr) {
 	for _, ifa := range ifat {
 		switch ifa := ifa.(type) {
 		case *IPAddr:
-			if ifa == nil {
-				t.Errorf("\tunexpected value: %v", ifa)
+			if ifa == nil || ifa.IP == nil {
+				t.Errorf("\tunexpected value: %v, %v", ifa, ifa.IP)
 			} else {
 				t.Logf("\tinterface address %q", ifa.String())
 			}
 		case *IPNet:
-			if ifa == nil {
-				t.Errorf("\tunexpected value: %v", ifa)
+			if ifa == nil || ifa.IP == nil || ifa.Mask == nil {
+				t.Errorf("\tunexpected value: %v, %v, %v", ifa, ifa.IP, ifa.Mask)
 			} else {
 				_, prefixLen := ifa.Mask.Size()
 				if ifa.IP.To4() != nil && prefixLen != 8*IPv4len || ifa.IP.To16() != nil && ifa.IP.To4() == nil && prefixLen != 8*IPv6len {

src/pkg/syscall/route_bsd.go

@@ -13,10 +13,14 @@ import "unsafe"
 // 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.
-	if darwinAMD64 {
+	// 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 {
 		salign = 4
+	} else if netbsd32Bit {
+		salign = 8
 	}
 	if salen == 0 {
 		return salign
@@ -142,6 +146,12 @@ func (m *InterfaceAddrMessage) sockaddr() (sas []Sockaddr) {
 		return nil
 	}
 	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++ {
 		if m.Header.Addrs&rtaIfaMask&(1<<i) == 0 {
 			continue
@@ -149,21 +159,29 @@ func (m *InterfaceAddrMessage) sockaddr() (sas []Sockaddr) {
 		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)))
 			if err != nil {
 				return nil
 			}
 			sas = append(sas, sa)
 		case RTAX_NETMASK:
-			if rsa.Family == AF_UNSPEC {
+			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 fasion, AF_UNSPEC means AF_INET
+					rsa.Family = AF_INET // an old fashion, AF_UNSPEC means AF_INET
 				}
+			case AF_INET, AF_INET6:
+				preferredFamily = rsa.Family
+			default:
+				return nil
 			}
 			sa, err := anyToSockaddr((*RawSockaddrAny)(unsafe.Pointer(rsa)))
 			if err != nil {

src/pkg/syscall/sockcmsg_unix.go

@@ -15,7 +15,7 @@ func cmsgAlignOf(salen int) int {
 	salign := sizeofPtr
 	// NOTE: It seems like 64-bit Darwin kernel still requires 32-bit
 	// aligned access to BSD subsystem.
-	if darwinAMD64 {
+	if darwin64Bit {
 		salign = 4
 	}
 	return (salen + salign - 1) & ^(salign - 1)

src/pkg/syscall/syscall_unix.go

@@ -18,7 +18,10 @@ var (
 	Stderr = 2
 )
 
-const darwinAMD64 = runtime.GOOS == "darwin" && runtime.GOARCH == "amd64"
+const (
+	darwin64Bit = runtime.GOOS == "darwin" && sizeofPtr == 8
+	netbsd32Bit = runtime.GOOS == "netbsd" && sizeofPtr == 4
+)
 
 func Syscall(trap, a1, a2, a3 uintptr) (r1, r2 uintptr, err Errno)
 func Syscall6(trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2 uintptr, err Errno)