Re: [libmicrohttpd] Problems using PATCH method

[Christian Grothoff]

Hi Conor,

I've tried to test this, and could not find an issue.  You can find a
new test case for MHD's PATCH handling in Git, as per change
b8a0f698..2d4289dc.  However, as the test worked instantly, I could not
find any bug with it.

The special handling of PUT/POST you mention likely refers to MHD's
handling for "100 CONTINUE". So sure, if you rely on "100 CONTINUE"
that likely only works with PUT/POST. 

My main idea as to what you might be doing wrong is queuing a response
before the upload is complete. With PUT/POST and "Expect: 100-
continue", this is supported by MHD. For other methods, you must wait
until you have received the full upload (if there is one) and only then
queue the response.

I suggest you look at the new 'test_patch.c', and if that doesn't help,
please send us some running minimal example to reproduce your issue.

Happy hacking!

Christian

On Wed, 2020-01-22 at 16:44 +0000, Conor Lennon via libmicrohttpd
wrote:
> Hi,
> 
> I'm using libmicrohttpd 0.9.63.
> 
> Looking at the libmicrohttpd code, I don't think the behaviour has
> changed since then.
> 
> I'm investigating a problem that I'm having with a PATCH request.
> 
> It's being handled differently from a PUT request.
> 
> I'm using the following to send a response to the request:
> 
> #define FORBIDDEN "{\"error_text\": \"Permission Denied\"}"
> struct MHD_Response *response=NULL;
> response = MHD_create_response_from_buffer(strlen (FORBIDDEN),
>                                            (void *) FORBIDDEN,
>                                            MHD_RESPMEM_PERSISTENT);
> MHD_add_response_header(response, "Content-Type",
> "application/json");
> ret = MHD_queue_response (connection, MHD_HTTP_FORBIDDEN, response);
> MHD_destroy_response (response);
> 
> For a PUT request, the client is getting the response.
> 
> However, with a PATCH request, the client is not getting a response.
> 
> I'm using curl as the HTTP client.
> 
> Looking at the MHD_connection_handle_idle function
> src/microhttpd/connection.c I can see that the POST and PUT methods
> are
> handled differently to everything else (e.g. when the state is
> MHD_CONNECTION_HEADERS_PROCESSED)
> 
> Is there a reason for that?
> 
> Should I be calling some other function to better handle the PATCH
> method?
> 
> I get similar behaviour with a random method when I send data.
> 
> Looking at the examples that libmicrohttpd comes with, I don't see
> any methods being used other than GET, HEAD and POST.
> 
> Thanks in advance,
> 
> Conor
>