syscall: fix parsing ipv6 address prefix on dragonfly

This change fixes a missing case that a routing address contains an
invalid address family label but it holds a valid length of address
structure.

Also makes test robust.

Fixes #10041.

Change-Id: I2480ba273929e859896697382d1a75b01a116b98
Reviewed-on: https://go-review.googlesource.com/6391Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/net/interface_test.go

@@ -48,9 +48,6 @@ func ipv6LinkLocalUnicastAddr(ifi *Interface) string {
 }
 
 func TestInterfaces(t *testing.T) {
-	if runtime.GOOS == "dragonfly" {
-		t.Skip("fail on dragonfly - issue 10041")
-	}
 	ift, err := Interfaces()
 	if err != nil {
 		t.Fatal(err)
@@ -108,9 +105,6 @@ func TestInterfaces(t *testing.T) {
 }
 
 func TestInterfaceAddrs(t *testing.T) {
-	if runtime.GOOS == "dragonfly" {
-		t.Skip("fail on dragonfly - issue 10041")
-	}
 	ift, err := Interfaces()
 	if err != nil {
 		t.Fatal(err)

src/syscall/route_bsd.go

@@ -140,8 +140,14 @@ func parseNetworkLayerAddr(b []byte, family byte) (Sockaddr, error) {
 	if len(b) < l {
 		return nil, EINVAL
 	}
-	switch family {
-	case AF_INET6:
+	// Don't reorder case expressions.
+	// The case expressions for IPv6 must come first.
+	switch {
+	case b[0] == SizeofSockaddrInet6:
+		sa := &SockaddrInet6{}
+		copy(sa.Addr[:], b[offsetofInet6:])
+		return sa, nil
+	case family == AF_INET6:
 		sa := &SockaddrInet6{}
 		if l-1 < offsetofInet6 {
 			copy(sa.Addr[:], b[1:l])
@@ -149,6 +155,10 @@ func parseNetworkLayerAddr(b []byte, family byte) (Sockaddr, error) {
 			copy(sa.Addr[:], b[l-offsetofInet6:l])
 		}
 		return sa, nil
+	case b[0] == SizeofSockaddrInet4:
+		sa := &SockaddrInet4{}
+		copy(sa.Addr[:], b[offsetofInet4:])
+		return sa, nil
 	default: // an old fashion, AF_UNSPEC or unknown means AF_INET
 		sa := &SockaddrInet4{}
 		if l-1 < offsetofInet4 {

src/syscall/route_bsd_test.go

@@ -18,7 +18,18 @@ import (
 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)
+			var err error
+			var b []byte
+			// The VM allocator wrapper functions can
+			// return ENOMEM easily.
+			for i := 0; i < 3; i++ {
+				b, err = syscall.RouteRIB(facility, param)
+				if err != nil {
+					time.Sleep(5 * time.Millisecond)
+					continue
+				}
+				break
+			}
 			if err != nil {
 				t.Error(facility, param, err)
 				continue
@@ -185,10 +196,27 @@ func (sas sockaddrs) String() string {
 
 func (sas sockaddrs) match(flags addrFlags) error {
 	var f addrFlags
+	family := syscall.AF_UNSPEC
 	for i := range sas {
 		if sas[i] != nil {
 			f |= 1 << uint(i)
 		}
+		switch sas[i].(type) {
+		case *syscall.SockaddrInet4:
+			if family == syscall.AF_UNSPEC {
+				family = syscall.AF_INET
+			}
+			if family != syscall.AF_INET {
+				return fmt.Errorf("got %v; want %v", sockaddrs(sas), family)
+			}
+		case *syscall.SockaddrInet6:
+			if family == syscall.AF_UNSPEC {
+				family = syscall.AF_INET6
+			}
+			if family != syscall.AF_INET6 {
+				return fmt.Errorf("got %v; want %v", sockaddrs(sas), family)
+			}
+		}
 	}
 	if f != flags {
 		return fmt.Errorf("got %v; want %v", f, flags)