Lars Eggert COMMENT (3)

[vixie]

Section 3.1, paragraph 3

     At the time of writing, most DNS server software did not set the DF
     bit for IPv4, and many OS kernel constraints make it difficult to set
     the DF bit in all cases.  Best Current Practice documents should not
     specify what is currently impossible, so R2, which is setting the DF
     bit, is "MAY" rather than "SHOULD".

Maybe I'm familiar with different kernels, but all the ones I am
familiar with (except for some IoT platforms) readily offer socket
options to set DF (and prevent stack fragmentation in v6).

[paulwouters]

this was rewritten based on various ballot comments. My propsed PR contains:

  and many OS kernel constraints make it difficult to set the DF bit in all cases.
  Best Current Practice documents should not specify what is currently impossible,
  so R2, which is setting the DF bit, is "MAY" rather than "SHOULD".

[vixie]

this is not the conclusion i saw on the WG. not sure the IESG intends to override a WG on this point? if it's not an oversight, i'd like to argue. Paul Wouters wrote on 2024-02-12 09:35:

…

this was rewritten based on various ballot comments. My propsed PR contains: |and many OS kernel constraints make it difficult to set the DF bit in all cases. Best Current Practice documents should not specify what is currently impossible, so R2, which is setting the DF bit, is "MAY" rather than "SHOULD". |

-- P Vixie

[paulwouters]

You are correct. I thought this has been rewritten. I think it should say:

Best Current Practice documents should not specify what is currently impossible,
  so R2, which is setting the DF bit, is "SHOULD" rather than "MUST"

[vixie]

I think "if supported, must" was the wg consensus. p vixie

[moonshiner]

Agree that "if supported, must" was the WG consensus and we are feel to push back on the IESG on this point.