RFC6126bis formally introduces sub-TLVs to the Babel protocol, including mandatory sub-TLVs. This adds support for parsing sub-TLVs to the Babel protocol and skips TLVs that contain mandatory sub-TLVs, as per the spec. For details, see section 4.4 of https://tools.ietf.org/html/draft-ietf-babel-rfc6126bis-02 Thanks to Toke Høiland-Jørgensen <toke@toke.dk> for the patch.