2 files changed, 44 insertions, 10 deletions
diff --git a/packet/bgp/bgp.go b/packet/bgp/bgp.go
index a911c411..3afb7a9e 100644
--- a/packet/bgp/bgp.go
+++ b/packet/bgp/bgp.go
@@ -5189,20 +5189,20 @@ func (p *PathAttributeMpReachNLRI) DecodeFromBytes(data []byte) error {
 	}
 	nexthopbin := value[4 : 4+nexthoplen]
 	if nexthoplen > 0 {
-		addrlen := 4
-		if afi == AFI_IP6 {
-			addrlen = 16
-		}
+		v4addrlen := 4
+		v6addrlen := 16
 		offset := 0
 		if safi == SAFI_MPLS_VPN {
 			offset = 8
 		}
 		switch nexthoplen {
-		case 2 * (offset + addrlen):
-			p.LinkLocalNexthop = nexthopbin[offset+addrlen+offset : 2*(offset+addrlen)]
+		case 2 * (offset + v6addrlen):
+			p.LinkLocalNexthop = nexthopbin[offset+v6addrlen+offset : 2*(offset+v6addrlen)]
 			fallthrough
-		case offset + addrlen:
-			p.Nexthop = nexthopbin[offset : offset+addrlen]
+		case offset + v6addrlen:
+			p.Nexthop = nexthopbin[offset : offset+v6addrlen]
+		case offset + v4addrlen:
+			p.Nexthop = nexthopbin[offset : offset+v4addrlen]
 		default:
 			return NewMessageError(eCode, eSubCode, value, "mpreach nexthop length is incorrect")
 		}
@@ -5235,7 +5235,7 @@ func (p *PathAttributeMpReachNLRI) Serialize() ([]byte, error) {
 	afi := p.AFI
 	safi := p.SAFI
 	nexthoplen := 4
-	if afi == AFI_IP6 {
+	if afi == AFI_IP6 || p.Nexthop.To4() == nil {
 		nexthoplen = 16
 	}
 	offset := 0
@@ -5254,7 +5254,7 @@ func (p *PathAttributeMpReachNLRI) Serialize() ([]byte, error) {
 	buf[2] = safi
 	buf[3] = uint8(nexthoplen)
 	if nexthoplen != 0 {
-		if afi == AFI_IP6 {
+		if p.Nexthop.To4() == nil {
 			copy(buf[4+offset:], p.Nexthop.To16())
 			if p.LinkLocalNexthop != nil {
 				copy(buf[4+offset+16:], p.LinkLocalNexthop.To16())
diff --git a/packet/bgp/bgp_test.go b/packet/bgp/bgp_test.go
index e0f1a5ca..e6d38873 100644
--- a/packet/bgp/bgp_test.go
+++ b/packet/bgp/bgp_test.go
@@ -739,3 +739,37 @@ func Test_MpReachNLRIWithVPNv6Prefix(t *testing.T) {
 	// Test serialised value
 	assert.Equal(bufin, bufout)
 }
+
+func Test_MpReachNLRIWithIPv4PrefixWithIPv6Nexthop(t *testing.T) {
+	assert := assert.New(t)
+	bufin := []byte{
+		0x80, 0x0e, 0x19, // flags(1), type(1), length(1)
+		0x00, 0x01, 0x01, 0x10, // afi(1), safi(1), nexthoplen(1)
+		0x20, 0x01, 0x0d, 0xb8, // nexthop(32)
+		0x00, 0x01, 0x00, 0x00, // = "2001:db8:1::1"
+		0x00, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x01,
+		0x00,                   // reserved(1)
+		0x18, 0xc0, 0xa8, 0x0a, // nlri(7)
+	}
+	// Test DecodeFromBytes()
+	p := &PathAttributeMpReachNLRI{}
+	err := p.DecodeFromBytes(bufin)
+	assert.Nil(err)
+	// Test decoded values
+	assert.Equal(BGPAttrFlag(0x80), p.Flags)
+	assert.Equal(BGPAttrType(0xe), p.Type)
+	assert.Equal(uint16(0x19), p.Length)
+	assert.Equal(uint16(AFI_IP), p.AFI)
+	assert.Equal(uint8(SAFI_UNICAST), p.SAFI)
+	assert.Equal(net.ParseIP("2001:db8:1::1"), p.Nexthop)
+	value := []AddrPrefixInterface{
+		NewIPAddrPrefix(24, "192.168.10.0"),
+	}
+	assert.Equal(value, p.Value)
+	// Test Serialize()
+	bufout, err := p.Serialize()
+	assert.Nil(err)
+	// Test serialised value
+	assert.Equal(bufin, bufout)
+}