Re: Support HTTP2 Goaway Frame callback for curl multi

From: Ray Satiro via curl-library <curl-library_at_lists.haxx.se>
Date: Fri, 5 Jan 2024 02:24:52 -0500

On 1/4/2024 10:45 PM, Cao Duc Quan via curl-library wrote:
> I am working on a small project where I need a callback from CURM when
> it receives the GOAWAY frame. I prepared a patch as follows and could
> get the callback for GOAWAY
>
> diff --git a/include/curl/multi.h b/include/curl/multi.h
> index e79b48ff3..c1b5adede 100644
> --- a/include/curl/multi.h
> +++ b/include/curl/multi.h
> _at__at_ -348,6 +348,12 @@ curl_multi_socket_all(CURLM *multi_handle, int
> *running_handles);
>  CURL_EXTERN CURLMcode curl_multi_timeout(CURLM *multi_handle,
>                                           long *milliseconds);
>
> +/*
> + * This macro help client know if they could install GOAWAY callback
> to this curl version.
> + * This is a temporary solution before the patch is merged to cURL
> mainline.
> + */
> +#define CURL_HAS_GOAWAY_CALLBACK 1
> +
>  typedef enum {
>    /* This is the socket callback function pointer */
>    CURLOPT(CURLMOPT_SOCKETFUNCTION, CURLOPTTYPE_FUNCTIONPOINT, 1),
> _at__at_ -399,6 +405,12 @@ typedef enum {
>    /* maximum number of concurrent streams to support on a connection */
>    CURLOPT(CURLMOPT_MAX_CONCURRENT_STREAMS, CURLOPTTYPE_LONG, 16),
>
> +  /* This is the goaway callback function pointer */
> +  CURLOPT(CURLMOPT_GOAWAY_CALLBACK, CURLOPTTYPE_FUNCTIONPOINT, 17),
> +
> +  /* This is the argument passed to the goaway callback */
> +  CURLOPT(CURLMOPT_GOAWAY_DATA, CURLOPTTYPE_OBJECTPOINT, 18),
> +
>    CURLMOPT_LASTENTRY /* the last unused */
>  } CURLMoption;
>
> _at__at_ -464,6 +476,19 _at__at_ typedef int (*curl_push_callback)(CURL *parent,
>                                    struct curl_pushheaders *headers,
>                                    void *userp);
>
> +/*
> + * Name: curl_goaway_callback
> + *
> + * Desc: This callback gets called when HTTP2 connection received
> + *       GOAWAY frame from peer. The Application may interest on this
> + *       event to trigger clean up functions or prepare new fresh
> + *       connection.
> + *
> + * Returns: None
> + */
> +typedef void (*curl_goaway_callback)(unsigned int error_code,
> +                                  int last_stream_id,
> +                                  void *userp);
>  #ifdef __cplusplus
>  } /* end of extern "C" */
>  #endif
> diff --git a/lib/http2.c b/lib/http2.c
> index c8b059498..6e28561f0 100644
> --- a/lib/http2.c
> +++ b/lib/http2.c
> _at__at_ -1251,6 +1251,13 _at_@ static int on_frame_recv(nghttp2_session
> *session, const nghttp2_frame *frame,
>          infof(data, "received GOAWAY, error=%d, last_stream=%u",
>                      ctx->goaway_error, ctx->last_stream_id);
>          Curl_multi_connchanged(data->multi);
> +        if(data->multi->goaway_cb) {
> +          Curl_set_in_callback(data, true);
> +          data->multi->goaway_cb(ctx->goaway_error,
> +                                 ctx->last_stream_id,
> + data->multi->goaway_userp);
> +          Curl_set_in_callback(data, false);
> +        }
>        }
>        break;
>      default:
>
>
> I would like to ask if there is an obvious issue with the patch. If
> not, could anyone guide me through any procedure I need to follow to
> get it in the cURL in github?


I won't land this. It sounds a lot like curl/curl#4839 [1]. Do you
really need it in curl or is there some way your application is working
that could be improved?


[1]: https://github.com/curl/curl/issues/4839

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Received on 2024-01-05