1) Changed the name of the option to 'extended next hop', for consistency with BGP (and in the future also with other protocols). As the option is enabled by default, the name likely does not matter that much.
I rather like v4-via-v6, which succintly and clearly states what it is about. "Extended next hop" means nothing unless you already know what it means.
3) In babel_handle_update(), move condition 'Reject IPv4 via IPv6 routes if disabled' above 'Retraction'. In your patch it was below, so retractions in AE 4 were accepted even on interfaces with this feature disabled.
That's reasonable enough, it shouldn't matter either way. Perhaps the former behaviour was more robust in the case where a node loses its IPv4 address and then immediately retracts the routes that it previously announced. Just a minor inconsistency, v4-via-v6 requests are accepted even if the option is disabled (line 1084). -- Juliusz