If you have a IPv6 only network then there should be no default IPv4 route so the connect(), sendto() etc. should all fail immediately with network unreachable. If they don’t then complain to your OS developer. If the application does not detect these failures complain to the application developer.
Applications should fail over immediately if there is not a covering route. If you have a local default IPv4 route, the router should be returning network unreachable and the OS should be processing them. This should cause network errors to be delivered to the application. The application should also be implementing happy eyeballs where you fail over to other addresses with sub second delays when there are multiple addresses to try. There is nothing wrong with having multiple connection attempts happening in parallel. Mucking with DNS responses is only covering up application defects. Filtering A records also breaks DNS64 for applications that are using DNSSEC as they need to see the A records as well as the AAAA responses. Notify the application vendor they they have a denial-of-service bug. Mark > On 2 May 2018, at 9:00 am, Kim Ebert <[email protected]> wrote: > > Hi All, > > I recently came across an issue where the user program preferred IPv4 over > IPv6. This is a problem because I've created a network that is IPv6 only. I'm > currently using NAT64 to provide access to services that don't have any IPv6 > access. > > Now this particular program could work if the DNS records didn't provide A > records. I would rather do everything I can as an admin to make the network > just work instead of waiting for all of the end user programs to be fixed, so > I started working on filter-a functionality to filter out A responses. > Currently implementation status is that it sort of works, which is further > than I expected to get in 2 days. > > I wonder if anyone in the community is interested in me sharing the work, and > if I should go to the effort to publish the effort? > > If anyone is curious, the offending program is nodejs and npm. > > Thanks, > > Kim > _______________________________________________ > Please visit https://lists.isc.org/mailman/listinfo/bind-users to unsubscribe > from this list > > bind-users mailing list > [email protected] > https://lists.isc.org/mailman/listinfo/bind-users -- Mark Andrews, ISC 1 Seymour St., Dundas Valley, NSW 2117, Australia PHONE: +61 2 9871 4742 INTERNET: [email protected] _______________________________________________ Please visit https://lists.isc.org/mailman/listinfo/bind-users to unsubscribe from this list bind-users mailing list [email protected] https://lists.isc.org/mailman/listinfo/bind-users
