body filter redirect

[Dk Jack]

Hello Maxim,
could you please respond to my previous message. Thanks.

Dk.

On Tue, Jul 13, 2021 at 9:28 PM Dk Jack <dnj0496 at gmail.com> wrote:

> Hello Maxim,
> Thanks for responding. Can I get some clarification on what you mean by
> the statement below:
>
> "More flexibility can be achieved by reading the request body
> earlier - for example, you can do this from your own module, or
> with embedded scripting such as perl or njs."
>
> Are you suggesting that I use ngx_http_read_client_request_body api in my
> module?
>
> http://nginx.org/en/docs/dev/development_guide.html#http_request_body
>
> I had similar trouble using that API with redirection. Are there some
> tricks to getting
> it to work when using that API? Are there any reference implementations
> doing
> redirection after inspecting the request body?
> Thanks for your help!
>
> Dk.
>
> > Hello!
> > It is generally too late to do any actions like "change the
> > upstream/location etc" based on the body content, as the request
> > body is usually read only when the location is already known and
> > the upstream name is already obtained. Also consider
> > "proxy_request_buffering off;" - reading the request body implies
> > that nginx is sending the request body to the backend as well.
> > That is, you can't really do more than modifying the request body
> > or rejecting the request completely.
> >
> > You may, however, provide some variables from your body request
> > body filter - and, if it's possible in your particular
> > configuration, use these variables to do some conditional
> > processing.
> >
> > Note thought that conditional processing needs to happen after the
> > request body is read. As such, it is usually quite limited,
> > especially when using standard modules, since the request body is
> > usually read last.
> >
> > For example, with proxy the request body is read after the
> > variables in the "proxy_pass" directive are evaluated, so even
> > with "proxy_request_buffering on;" (the default) you cannot use
> > the variables from your request body filter module to change the
> > upstream. You can, however, use it to control headers in the
> > upstream request by using "proxy_set_header" with appropriate
> > variables (again, assuming buffered request body reading - for
> > obvious reasons this won't work with "proxy_request_buffering
> > off;").
> >
> > More flexibility can be achieved by reading the request body
> > earlier - for example, you can do this from your own module, or
> > with embedded scripting such as perl or njs.
> >
> > --
> > Maxim Dounin
> > http://mdounin.ru/
> > _______________________________________________
> > nginx-devel mailing list
> > nginx-devel at nginx.org
> > http://mailman.nginx.org/mailman/listinfo/nginx-devel
> >
> On Mon, Jul 12, 2021 at 12:47 PM Dk Jack <dnj0496 at gmail.com> wrote:
>
>> Hi,
>> In my module, I am trying to take actions based on the content of the
>> body. To accomplish this, I am capturing the body using body file as shown
>> in the example below:
>>
>>
>> http://mdounin.ru/hg/ngx_http_catch_body_filter_module/file/tip/ngx_http_catch_body_filter_module.c
>>
>> This is working well. I can inspect the contents of the body and take
>> different actions like rejecting requests etc. However, one of the actions
>> I want to do is redirect the request based on the body content i.e if the
>> content contains some string etc, then redirect the request i.e change the
>> upstream/location etc. My question is, is it even possible to redirect a
>> request in the body filter stage? Is there another way to do body
>> capture/filter and still be able to redirect the request after inspecting
>> the body? Any help, suggestions or sample code is appreciated. Thanks.
>>
>> Dk.
>>
>>
>>
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