Revert "Fix Router Advertisement/Solicitation option parsing"

This reverts commit f5877367522aad0b27d138e4a56d01be3bd33f2d.
Revert "Router Advertisement/Solicitation sanity check"

This reverts commit 3f417e55d5208df5b91aa9b101657bbc7a461614.
Readd fixed ICMPv6 validity check
Merge remote branch 'upstream/master'