[squid-users] why-squid-reuse-headers-from-parent-but-not-the-html-body-when-not-200-ok

[Tom JABBER]

@alex

"because popular browsers pretty much ignore CONNECT response headers 
(except for proxy authentication) and body (always?)."

Well that's exactly how we discovered it: facing a parent proxy that 
needs some AUTH.

"* After sending (to the client) an HTTP response header promising a 
body, Squid has an obligation to send that promised (and available to 
Squid) response body. Squid does not send it. Squid is buggy."

We definitively agree on this.

"It is possible to modify Squid to stop promising to send the cache_peer 
response body (at an HTTP framing level), but it is probably better (and 
easier!) to modify Squid to just generate a short error response from 
scratch (instead of forwarding cache_peer response headers without a 
body). Doing so will probably break some use cases, so such a change may 
be officially rejected, but, even if it is, it may still work/help in 
some other specific use cases."

By saying this you're suggesting I try to code this ? Or is there a 
possible configuration I missed ?


@amos

"curl itself does this even without Squid."

What do you mean ?


On 2/3/23 10:52 PM, Alex Rousskov wrote:
> On 2/3/23 16:15, Amos Jeffries wrote:
>> On 4/02/2023 7:15 am, Alex Rousskov wrote:
>>> On 2/3/23 10:08, Tom JABBER wrote:
>>>
>>>> As said in subject, if parent proxy returns a non 200 OK code along 
>>>> with some HTML body, "child" proxy reuses parent headers, which is 
>>>> already a matter of discussion, and among other headers, a 
>>>> content-length > 0 while not forwarding the HTML received from parent.
>>>>
>>>> cf. 
>>>> https://superuser.com/questions/1765082/why-squid-reuse-headers-from-parent-but-not-the-html-body-when-not-200-ok
>>>>
>>>> Would there be anyone here willing to help ?
>>>
>>> It is a known Squid bug.
>
>
>> @Alex, see my response. curl itself does this even without Squid.
>
>
> I believe your earlier response does not contradict mine (and does not 
> quite match the primary question about the error response body):
>
> * Curl has a right to ignore the CONNECT error response body sent by 
> the proxy. Curl is not buggy in this respect[1]. This correct curl 
> behavior actually matches my assertion that browsers ignore CONNECT 
> error response bodies.
>
> * After sending (to the client) an HTTP response header promising a 
> body, Squid has an obligation to send that promised (and available to 
> Squid) response body. Squid does not send it. Squid is buggy.
>
>
> HTH,
>
> Alex.
>
> [1]: I would argue that curl is also buggy with respect to header 
> handling because curl stores CONNECT error response headers (e.g. when 
> -i option is given) as if they came from the origin server. The caller 
> might mistake those headers for a secure origin server response 
> header. However, the primary question was not about the headers.
>
>
>> On 2/3/23 13:15, Alex Rousskov wrote:
>>> On 2/3/23 10:08, Tom JABBER wrote:
>>>
>>>> As said in subject, if parent proxy returns a non 200 OK code along 
>>>> with some HTML body, "child" proxy reuses parent headers, which is 
>>>> already a matter of discussion, and among other headers, a 
>>>> content-length > 0 while not forwarding the HTML received from parent.
>>>>
>>>> cf. 
>>>> https://superuser.com/questions/1765082/why-squid-reuse-headers-from-parent-but-not-the-html-body-when-not-200-ok
>>>>
>>>> Would there be anyone here willing to help ?
>>>
>>> It is a known Squid bug. AFAIK, the bug does not have a simple 
>>> general-purpose fix, and there is probably relatively little demand 
>>> for fixing it because popular browsers pretty much ignore CONNECT 
>>> response headers (except for proxy authentication) and body (always?).
>>>
>>> It is possible to modify Squid to stop promising to send the 
>>> cache_peer response body (at an HTTP framing level), but it is 
>>> probably better (and easier!) to modify Squid to just generate a 
>>> short error response from scratch (instead of forwarding cache_peer 
>>> response headers without a body). Doing so will probably break some 
>>> use cases, so such a change may be officially rejected, but, even if 
>>> it is, it may still work/help in some other specific use cases.
>>>
>>> https://wiki.squid-cache.org/SquidFaq/AboutSquid#how-to-add-a-new-squid-feature-enhance-of-fix-something 
>>>
>
>
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-- 
@TJ