Releive length check for NeighAttributes

The attribute length has more context then previously presumed.
Especially when using tunnels and other link types, the attributes
can use different lengths then expected.

Signed-off-by: Jeroen Simonetti <[email protected]>

neigh.go

@@ -13,9 +13,6 @@ import (
 var (
 	// errInvalidNeighMessage is returned when a LinkMessage is malformed.
 	errInvalidNeighMessage = errors.New("rtnetlink NeighMessage is invalid or too short")
-
-	// errInvalidNeighMessageAttr is returned when neigh attributes are malformed.
-	errInvalidNeighMessageAttr = errors.New("rtnetlink NeighMessage has a wrong attribute data length")
 )
 
 var _ Message = &NeighMessage{}
@@ -186,8 +183,8 @@ func (a *NeighAttributes) decode(ad *netlink.AttributeDecoder) error {
 			// unused attribute
 		case unix.NDA_DST:
 			l := len(ad.Bytes())
-			if l != 4 && l != 16 {
-				return errInvalidNeighMessageAttr
+			if l == 0 {
+				continue
 			}
 			a.Address = ad.Bytes()
 		case unix.NDA_LLADDR:
@@ -198,9 +195,6 @@ func (a *NeighAttributes) decode(ad *netlink.AttributeDecoder) error {
 				// Ignore empty addresses.
 				continue
 			}
-			if l != 6 && l != 8 && l != 20 {
-				return errInvalidNeighMessageAttr
-			}
 			a.LLAddress = ad.Bytes()
 		case unix.NDA_CACHEINFO:
 			a.CacheInfo = &NeighCacheInfo{}

neigh_test.go

@@ -142,20 +142,6 @@ func TestNeighMessageUnmarshalBinary(t *testing.T) {
 			b:    make([]byte, 11),
 			err:  errInvalidNeighMessage,
 		},
-		{
-			name: "invalid attr",
-			b: []byte{
-				0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-				0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-				0x06, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-				0x04, 0x00, 0x01, 0x00, 0x04, 0x00, 0x02, 0x00,
-				0x05, 0x00, 0x03, 0x00, 0x00, 0x00, 0x00, 0x00,
-				0x08, 0x00, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00,
-				0x08, 0x00, 0x05, 0x00, 0x00, 0x00, 0x00, 0x00,
-				0x05, 0x00, 0x06, 0x00, 0x00, 0x00, 0x00, 0x00,
-			},
-			err: errInvalidNeighMessageAttr,
-		},
 		{
 			name: "data",
 			b: []byte{