Don't hold AddressEndpoints for multicast addresses

Group addressable endpoints can simply check if it has joined the
multicast group without maintaining address endpoints. This also
helps remove the dependency on AddressableEndpoint from
GroupAddressableEndpoint.

Now that group addresses are not tracked with address endpoints, we can
avoid accidentally obtaining a route with a multicast local address.

PiperOrigin-RevId: 343336912

5 files changed, 48 insertions, 49 deletions

diff --git a/pkg/tcpip/network/ipv4/ipv4.go b/pkg/tcpip/network/ipv4/ipv4.go
index 1efe6297a..dd4251d78 100644
--- a/pkg/tcpip/network/ipv4/ipv4.go
+++ b/pkg/tcpip/network/ipv4/ipv4.go
@@ -566,21 +566,6 @@ func (e *endpoint) handlePacket(pkt *stack.PacketBuffer) {
 		stats.IP.MalformedPacketsReceived.Increment()
 		return
 	}
-	srcAddr := h.SourceAddress()
-	dstAddr := h.DestinationAddress()
-
-	addressEndpoint := e.AcquireAssignedAddress(dstAddr, e.nic.Promiscuous(), stack.CanBePrimaryEndpoint)
-	if addressEndpoint == nil {
-		if !e.protocol.Forwarding() {
-			stats.IP.InvalidDestinationAddressesReceived.Increment()
-			return
-		}
-
-		_ = e.forwardPacket(pkt)
-		return
-	}
-	subnet := addressEndpoint.AddressWithPrefix().Subnet()
-	addressEndpoint.DecRef()
 
 	// There has been some confusion regarding verifying checksums. We need
 	// just look for negative 0 (0xffff) as the checksum, as it's not possible to
@@ -608,16 +593,42 @@ func (e *endpoint) handlePacket(pkt *stack.PacketBuffer) {
 		return
 	}
 
+	srcAddr := h.SourceAddress()
+	dstAddr := h.DestinationAddress()
+
 	// As per RFC 1122 section 3.2.1.3:
 	//   When a host sends any datagram, the IP source address MUST
 	//   be one of its own IP addresses (but not a broadcast or
 	//   multicast address).
-	if directedBroadcast := subnet.IsBroadcast(srcAddr); directedBroadcast || srcAddr == header.IPv4Broadcast || header.IsV4MulticastAddress(srcAddr) {
+	if srcAddr == header.IPv4Broadcast || header.IsV4MulticastAddress(srcAddr) {
 		stats.IP.InvalidSourceAddressesReceived.Increment()
 		return
 	}
+	// Make sure the source address is not a subnet-local broadcast address.
+	if addressEndpoint := e.AcquireAssignedAddress(srcAddr, false /* createTemp */, stack.NeverPrimaryEndpoint); addressEndpoint != nil {
+		subnet := addressEndpoint.Subnet()
+		addressEndpoint.DecRef()
+		if subnet.IsBroadcast(srcAddr) {
+			stats.IP.InvalidSourceAddressesReceived.Increment()
+			return
+		}
+	}
 
-	pkt.NetworkPacketInfo.LocalAddressBroadcast = subnet.IsBroadcast(dstAddr) || dstAddr == header.IPv4Broadcast
+	// The destination address should be an address we own or a group we joined
+	// for us to receive the packet. Otherwise, attempt to forward the packet.
+	if addressEndpoint := e.AcquireAssignedAddress(dstAddr, e.nic.Promiscuous(), stack.CanBePrimaryEndpoint); addressEndpoint != nil {
+		subnet := addressEndpoint.AddressWithPrefix().Subnet()
+		addressEndpoint.DecRef()
+		pkt.NetworkPacketInfo.LocalAddressBroadcast = subnet.IsBroadcast(dstAddr) || dstAddr == header.IPv4Broadcast
+	} else if !e.IsInGroup(dstAddr) {
+		if !e.protocol.Forwarding() {
+			stats.IP.InvalidDestinationAddressesReceived.Increment()
+			return
+		}
+
+		_ = e.forwardPacket(pkt)
+		return
+	}
 
 	// iptables filtering. All packets that reach here are intended for
 	// this machine and will not be forwarded.
diff --git a/pkg/tcpip/network/ipv6/icmp.go b/pkg/tcpip/network/ipv6/icmp.go
index beb8f562e..386d98a29 100644
--- a/pkg/tcpip/network/ipv6/icmp.go
+++ b/pkg/tcpip/network/ipv6/icmp.go
@@ -796,7 +796,8 @@ func (p *protocol) returnError(reason icmpReason, pkt *stack.PacketBuffer) *tcpi
 		allowResponseToMulticast = reason.respondToMulticast
 	}
 
-	if (!allowResponseToMulticast && header.IsV6MulticastAddress(origIPHdrDst)) || origIPHdrSrc == header.IPv6Any {
+	isOrigDstMulticast := header.IsV6MulticastAddress(origIPHdrDst)
+	if (!allowResponseToMulticast && isOrigDstMulticast) || origIPHdrSrc == header.IPv6Any {
 		return nil
 	}
 
@@ -812,8 +813,13 @@ func (p *protocol) returnError(reason icmpReason, pkt *stack.PacketBuffer) *tcpi
 	// If we are operating as a router, do not use the packet's destination
 	// address as the response's source address as we should not own the
 	// destination address of a packet we are forwarding.
+	//
+	// If the packet was originally destined to a multicast address, then do not
+	// use the packet's destination address as the source for the response ICMP
+	// packet as "multicast addresses must not be used as source addresses in IPv6
+	// packets", as per RFC 4291 section 2.7.
 	localAddr := origIPHdrDst
-	if _, ok := reason.(*icmpReasonHopLimitExceeded); ok {
+	if _, ok := reason.(*icmpReasonHopLimitExceeded); ok || isOrigDstMulticast {
 		localAddr = ""
 	}
 	// Even if we were able to receive a packet from some remote, we may not have
diff --git a/pkg/tcpip/network/ipv6/ipv6.go b/pkg/tcpip/network/ipv6/ipv6.go
index 7a00f6314..fa2adb0b3 100644
--- a/pkg/tcpip/network/ipv6/ipv6.go
+++ b/pkg/tcpip/network/ipv6/ipv6.go
@@ -737,8 +737,11 @@ func (e *endpoint) handlePacket(pkt *stack.PacketBuffer) {
 		return
 	}
 
-	addressEndpoint := e.AcquireAssignedAddress(dstAddr, e.nic.Promiscuous(), stack.CanBePrimaryEndpoint)
-	if addressEndpoint == nil {
+	// The destination address should be an address we own or a group we joined
+	// for us to receive the packet. Otherwise, attempt to forward the packet.
+	if addressEndpoint := e.AcquireAssignedAddress(dstAddr, e.nic.Promiscuous(), stack.CanBePrimaryEndpoint); addressEndpoint != nil {
+		addressEndpoint.DecRef()
+	} else if !e.IsInGroup(dstAddr) {
 		if !e.protocol.Forwarding() {
 			stats.IP.InvalidDestinationAddressesReceived.Increment()
 			return
@@ -747,7 +750,6 @@ func (e *endpoint) handlePacket(pkt *stack.PacketBuffer) {
 		_ = e.forwardPacket(pkt)
 		return
 	}
-	addressEndpoint.DecRef()
 
 	// vv consists of:
 	// - Any IPv6 header bytes after the first 40 (i.e. extensions).
diff --git a/pkg/tcpip/network/ipv6/ipv6_test.go b/pkg/tcpip/network/ipv6/ipv6_test.go
index a671d4bac..cff98c541 100644
--- a/pkg/tcpip/network/ipv6/ipv6_test.go
+++ b/pkg/tcpip/network/ipv6/ipv6_test.go
@@ -873,7 +873,13 @@ func TestReceiveIPv6ExtHdrs(t *testing.T) {
 				Length:  uint16(udpLength),
 			})
 			copy(u.Payload(), udpPayload)
-			sum := header.PseudoHeaderChecksum(udp.ProtocolNumber, addr1, addr2, uint16(udpLength))
+
+			dstAddr := tcpip.Address(addr2)
+			if test.multicast {
+				dstAddr = header.IPv6AllNodesMulticastAddress
+			}
+
+			sum := header.PseudoHeaderChecksum(udp.ProtocolNumber, addr1, dstAddr, uint16(udpLength))
 			sum = header.Checksum(udpPayload, sum)
 			u.SetChecksum(^u.CalculateChecksum(sum))
 
@@ -884,10 +890,6 @@ func TestReceiveIPv6ExtHdrs(t *testing.T) {
 			// Serialize IPv6 fixed header.
 			payloadLength := hdr.UsedLength()
 			ip := header.IPv6(hdr.Prepend(header.IPv6MinimumSize))
-			dstAddr := tcpip.Address(addr2)
-			if test.multicast {
-				dstAddr = header.IPv6AllNodesMulticastAddress
-			}
 			ip.Encode(&header.IPv6Fields{
 				PayloadLength: uint16(payloadLength),
 				NextHeader:    ipv6NextHdr,
diff --git a/pkg/tcpip/stack/addressable_endpoint_state.go b/pkg/tcpip/stack/addressable_endpoint_state.go
index 9478f3fb7..adeebfe37 100644
--- a/pkg/tcpip/stack/addressable_endpoint_state.go
+++ b/pkg/tcpip/stack/addressable_endpoint_state.go
@@ -594,15 +594,6 @@ func (a *AddressableEndpointState) JoinGroup(group tcpip.Address) (bool, *tcpip.
 	defer a.mu.Unlock()
 
 	joins, ok := a.mu.groups[group]
-	if !ok {
-		ep, err := a.addAndAcquireAddressLocked(group.WithPrefix(), NeverPrimaryEndpoint, AddressConfigStatic, false /* deprecated */, true /* permanent */)
-		if err != nil {
-			return false, err
-		}
-		// We have no need for the address endpoint.
-		a.decAddressRefLocked(ep)
-	}
-
 	a.mu.groups[group] = joins + 1
 	return !ok, nil
 }
@@ -618,7 +609,6 @@ func (a *AddressableEndpointState) LeaveGroup(group tcpip.Address) (bool, *tcpip
 	}
 
 	if joins == 1 {
-		a.removeGroupAddressLocked(group)
 		delete(a.mu.groups, group)
 		return true, nil
 	}
@@ -635,23 +625,11 @@ func (a *AddressableEndpointState) IsInGroup(group tcpip.Address) bool {
 	return ok
 }
 
-func (a *AddressableEndpointState) removeGroupAddressLocked(group tcpip.Address) {
-	if err := a.removePermanentAddressLocked(group); err != nil {
-		// removePermanentEndpointLocked would only return an error if group is
-		// not bound to the addressable endpoint, but we know it MUST be assigned
-		// since we have group in our map of groups.
-		panic(fmt.Sprintf("error removing group address = %s: %s", group, err))
-	}
-}
-
 // Cleanup forcefully leaves all groups and removes all permanent addresses.
 func (a *AddressableEndpointState) Cleanup() {
 	a.mu.Lock()
 	defer a.mu.Unlock()
 
-	for group := range a.mu.groups {
-		a.removeGroupAddressLocked(group)
-	}
 	a.mu.groups = make(map[tcpip.Address]uint32)
 
 	for _, ep := range a.mu.endpoints {