Re: H2 vs HPACK header table size... again

On Thu, Dec 23, 2021 at 07:33:15AM +0100, Willy Tarreau wrote:
> Yes I know, that's delicate. But we're not changing the spec, just clarifying
> something that seems to match a consensus between a majority of implementers.
> In any case we're certainly not going to declare them non-compliant after
> so many years, whatever side they're currently on. And those who read it
> like me (apparently Cory and Hervé did) will likely not have a big
> difficulty seeing the other interpretation that most other implementation
> already adopted.

While running some tests on my side after adapting my code, I discovered
that the H2 client in the varnish-test suite doesn't seem to like very much
receiving a table size update of zero (that may be OK it's a regression
testing program). That led me to test varnish then a few other sites with
the following command:

  $ nghttp -v -H":method: HEAD" --header-table-size=0 https://$SITE

And the result is not as bright as initially thought:
  - causes a compression error
  - causes a compression error.
  - causes a compression error
  - causes a compression error
  - causes a compression error
  - doesn't speak H2
  - / .com surprisingly do not speak H2
  - is OK
  - is OK
  - causes a compression error

It even seems to me that it's 50/50 between the two interpretations :-(

Thus it seems to me that we have to be extremely careful about what we
state and that a discussion with the various implementers is needed.
Maybe at least the proposed added note for h2bis could be turned as
a warning about known existing deployments that act differently and
that need to be taken care of.


Received on Thursday, 23 December 2021 08:03:05 UTC