DF-Flag on UDP-based sockets?

[Tom]

On 11/30/22 09:27, Borja Marcos wrote:
> 
> 
>> On 30 Nov 2022, at 08:20, Tom <lists at verreckte-cheib.ch> wrote:
>>
>> Hi list
>>
>> Regarding ARM 9.18.9 (https://bind9.readthedocs.io/en/v9_18_9/reference.html#namedconf-statement-edns-udp-size):
>> "The named now sets the DON’T FRAGMENT flag on outgoing UDP packets."
>>
>> Tested with BIND-9.18.9, I didn't saw any UDP packets, where the "DF"-flag was set on the IP header (true for TCP, but never seen for UDP).
>>
>> Which circumstands or which queries enforces BIND9 to set the "DF"-flag on outgoing UDP-based packets?
> 
> I have checked on FreeBSD 13.1 and indeed I don’t see the flag. Neither for UDP queries or responses.
> 
> What OS are you trying? Might be OS dependant.
> 

I'm trying on linux.

It seems, that this behavior was introduced with
https://gitlab.isc.org/isc-projects/bind9/-/commit/371f829327b8f4cdfae4fa0cca512dcf483eff23

and reverted with
https://gitlab.isc.org/isc-projects/bind9/-/merge_requests/4668/diffs

but the ARM wasn't reverted/corrected.

Does someone of ISC agree? If so, I'll file a bug.

Thank you.
Tom




> 
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> Borja.
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