What was the motivation for adding the IPV6_V6ONLY flag?

Question

In IPv6 networking, the IPV6_V6ONLY flag is used to ensure that a socket will only use IPv6, and in particular that IPv4-to-IPv6 mapping won\'t be used for that socket. On many

Answer 1

There are plausible ways in which the (poorly named) "IPv4-mapped" addresses can be used to circumvent poorly configured systems, or bad stacks, or even in a well configured system might just require onerous amounts of bugproofing. A developer might wish to use this flag to make their application more secure by not utilizing this part of the API.

See: http://ipv6samurais.com/ipv6samurais/openbsd-audit/draft-cmetz-v6ops-v4mapped-api-harmful-01.txt