[squid-users] Squid and ICAP using 206 response on reply

[Alex Rousskov]

On 2/4/19 11:25, johnr wrote:

> I've attempting to use a RESPMOD ICAP in squid to modify the response
> headers before they get to my user. I am attempting to use the ICAP 206 code
> to be able to do this.
> 
> Everything works fine if the response payload is more than the preview that
> my ICAP takes. But, if the max size of the preview is greater than the size
> of the response payload, the 206 response does not do anything (and it
> basically looks like a 204 where I get back the original response without
> any header modification).

> Is this a known fact that if the response is smaller than the max preview
> size then 206 is not a valid response?

IIRC, there is no such fact. In fact, 206 works in Preview by default 
(and can work outside of Preview after additional signaling from the 
ICAP client):

 > draft-icap-ext-partial-content-07.txt:
> Partial Content feature is limited to ICAP Preview by default.
>    Similar to ICAP 204 (No Content) responses, an ICAP client may enable
>    Partial Content responses outside of Preview by sending "Allow: 204,
>    206" REQMOD or RESPMOD header.



> I can't find evidence for that in the ICAP spec, so I am thinking
> there's a chance I'm doing something else wrong?

It could be a Squid bug or your ICAP service could be doing something 
wrong. Consider posting a [link to] compressed Squid cache.log with 
debug_options set to ALL,9 (or, at the very least, "ALL,3 93,9").


Cheers,

Alex.