IPv6 Neighbor Discovery/Routing Failing for Kernel 3.10
Solution 1:
If you are experiencing weird routing issues with packets missing, follow these steps:
ip l and note the MAC Addresses
tcpdump -en -i eth0 ip6 (or the corresponding interface) and compare them, if they match all is good
ip -6 a compare the Link Local Addresses (scope local) to your mac address (here is a calculator: http://ben.akrin.com/?p=1347 , there are a few)
if it's still not working I guess the problem lies in the iptables, use logging as much as possible :)