what constitutes an "invalid" content-length

Hi all

just dealing with a site that sends more payload data than is indicated 
in the Content-Length header.

If the browser connects directly, the page loads fine, if via the proxy, 
the proxy is truncating the length to that advertised and the client 
isn't displaying a page (of course this is the .css file).

RFC7230 sections 3.3.2 (Content-Length), 3.3.3 (Message body length), 
and 3.3.4 (Handling incomplete messages) only contemplate issues around 
Content-Length specifying more bytes than are received, not fewer.

I guess one could argue that a wrong C-L value is "invalid", but it's 
not clear that invalid in this context simply means it doesn't parse, or 
is otherwise non-compliant with the ABNF.

So, it's not clear what the browser and/or proxy response should be.  If 
we deem a wrong value to be "invalid" (s3.3.3 para 4), a client is 
supposed to discard the response.  This isn't happening.

For the proxy, it only sees that the content length is wrong once it 
receives too many bytes.  By this stage, the horse has bolted so it 
cannot really comply either.

I would expect it's in everyone's best interest if sites that have 
broken framing are forced to be fixed.  This won't happen if browsers 
"just work" for the site.

Is there a special behaviour we should agree on for such cases?

Regards

Adrien de Croy