http2: remove conn->data use

... but instead use a private alternative that points to the "driving
transfer" from the connection. We set the "user data" associated with
the connection to be the connectdata struct, but when we drive transfers
the code still needs to know the pointer to the transfer. We can change
the user data to become the Curl_easy handle, but with older nghttp2
version we cannot dynamically update that pointer properly when
different transfers are used over the same connection.

Closes #6520

1 files changed, 8 insertions, 1 deletions

diff --git a/lib/http.h b/lib/http.h
index 28f9341f6..587e032cd 100644
--- a/lib/http.h
+++ b/lib/http.h
@@ -251,9 +251,16 @@ struct h2settings {
 struct http_conn {
 #ifdef USE_NGHTTP2
 #define H2_BINSETTINGS_LEN 80
-  nghttp2_session *h2;
   uint8_t binsettings[H2_BINSETTINGS_LEN];
   size_t  binlen; /* length of the binsettings data */
+
+  /* We associate the connnectdata struct with the connection, but we need to
+     make sure we can identify the current "driving" transfer. This is a
+     work-around for the lack of nghttp2_session_set_user_data() in older
+     nghttp2 versions that we want to support. (Added in 1.31.0) */
+  struct Curl_easy *trnsfr;
+
+  nghttp2_session *h2;
   Curl_send *send_underlying; /* underlying send Curl_send callback */
   Curl_recv *recv_underlying; /* underlying recv Curl_recv callback */
   char *inbuf; /* buffer to receive data from underlying socket */