[ipxe-devel] Fallback to IPv4 or disable IPv6

[John Haxby]

> On 19 Nov 2018, at 11:26, Geert Stappers <geert.stappers at hendrikx-itc.nl> wrote:
> 
> On Mon, Nov 19, 2018 at 12:13:55PM +0100, Andreas Fink wrote:
>>> On 19 Nov 2018, at 11:52, Michael Brown <mcb30 at ipxe.org> wrote:
>>> On 01/11/2018 17:40, Anatoli Babenia wrote:
>>>> My upstream provider doesn't support IPv6. No addresses are reachable.
>>>> But my router still gives me an IPv6 address and is even able to resolve
>>>> AAAA records. Being able to resolve IPv6 address iPXE thinks that it got
>>>> IPv6 and fails, but it should try IPv4 instead.
>>>> Here is the log - https://github.com/antonym/netboot.xyz/issues/283
>>>> Is it possible to make current 133f fallback to IPv4 if IPv6 fetch fails?
>>>> Also, is there an option to disable IPv6 from Failsafe Menu? Manual
>>>> network configuration doesn't help.
>>> 
>>> iPXE will query for AAAA records only if the DNS server address is itself an IPv6 address.  This is the heuristic we use to decide between IPv6 and IPv4 when a DNS name is used.
>> 
>> This is not really what the idea is.
>> 
>> I would recommend the following logic:
> 
> I would appreciate patches.
> 
>> 1. If there is a IPv4 address only provided by the DHCP server, do IPv4 only.  Consider the host "ipv4 only"
>> 1. If there is a IPv6 address only provided by the DHCP server or through router advertizement (and its not only link local)  do IPv6 only. Consider the host "ipv6 only"
>> 3. If there host has a IPv4 and a IPv6 address do both ( Consider the host ipv4/ivp6 capable)
> 
> Bullshit.  Reread

That made a lot of sense to me ...

>>> iPXE will query for AAAA records only if the DNS server address is itself an IPv6 address.  This is the heuristic we use to decide between IPv6 and IPv4 when a DNS name is used.
> 
> Pay attention to the "decide between IPv6 and IPv4" part.


I guess I'm missing something fundamental here because I don't see how using the DNS server address is going to work in many cases.

The DNS servers at $employer, at home and elsewhere have both IPv4 and IPv6 addresses and, as I recall, you'd have to be pure IPv6 to get an IPv6 DNS server.  Most machines are both IPv4 and IPv6 capable and tend to get IPv4 DNS servers and not IPv6 name servers.   With a scheme that uses the DNS server to decide whether or not to use IPv6 that would preclude using IPv6 completely.  On the other hand, it seems to make more sense to use the address families offered by DHCP/RA -- if you're given an IPv6 address, make AAAA queries etc.  And unless you're going to adopt Happy Eyes, then preferring IPv6 over IPv4 is better.

jch

>  
> 
> Cheers
> Geert Stappers
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