Merge pull request #1990 from SoftEtherVPN/fix1972

Fix memory access error when IPv6 prefix reading, should resolve #1972

src/Cedar/IPC.c

@@ -1517,7 +1517,9 @@ void IPCProcessL3EventsEx(IPC *ipc, UINT64 now)
 									// We save the router advertisement data for later use
 									IPCIPv6AddRouterPrefixes(ipc, &p->ICMPv6HeaderPacketInfo.OptionList, src_mac, &ip_src);
 									IPCIPv6AssociateOnNDTEx(ipc, &ip_src, src_mac, true);
+									if (p->ICMPv6HeaderPacketInfo.OptionList.SourceLinkLayer != NULL) {
 										IPCIPv6AssociateOnNDTEx(ipc, &ip_src, p->ICMPv6HeaderPacketInfo.OptionList.SourceLinkLayer->Address, true);
+									}
 									ndtProcessed = true;
 									header_size = sizeof(ICMPV6_ROUTER_ADVERTISEMENT_HEADER);
 									break;
@@ -2354,7 +2356,14 @@ void IPCIPv6AddRouterPrefixes(IPC *ipc, ICMPV6_OPTION_LIST *recvPrefix, UCHAR *m
 				IntToSubnetMask6(&newRA->RoutedMask, recvPrefix->Prefix[i]->SubnetLength);
 				CopyIP(&newRA->RouterAddress, ip);
 				Copy(newRA->RouterMacAddress, macAddress, 6);
+				if (recvPrefix->SourceLinkLayer != NULL)
+				{
 					Copy(newRA->RouterLinkLayerAddress, recvPrefix->SourceLinkLayer->Address, 6);
+				}
+				else
+				{
+					Zero(newRA->RouterLinkLayerAddress, 6);
+				}
 				Add(ipc->IPv6RouterAdvs, newRA);
 			}
 		}
@@ -2657,7 +2666,7 @@ void IPCIPv6SendUnicast(IPC *ipc, void *data, UINT size, IP *next_ip)
 		}
 
 		destMac = ra.RouterMacAddress;
-		if (!IsMacUnicast(destMac) && !IsMacInvalid(ra.RouterMacAddress))
+		if (!IsMacUnicast(destMac) && !IsMacInvalid(ra.RouterLinkLayerAddress))
 		{
 			destMac = ra.RouterLinkLayerAddress;
 		}