From 7dbdd698ae7f364bdd2377a8a0e8828f0714d387 Mon Sep 17 00:00:00 2001
From: Jeroen Simonetti <jeroen@simonetti.nl>
Date: Thu, 28 Dec 2023 18:35:27 +0100
Subject: [PATCH] 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 <jeroen@simonetti.nl>
---
 neigh.go      | 10 ++--------
 neigh_test.go | 14 --------------
 2 files changed, 2 insertions(+), 22 deletions(-)

diff --git a/neigh.go b/neigh.go
index 22b9f83..2ea824f 100644
--- a/neigh.go
+++ b/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{}
diff --git a/neigh_test.go b/neigh_test.go
index 2a132f2..8f5b22b 100644
--- a/neigh_test.go
+++ b/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{