CURLOPT_PREREQFUNCTION: add new callback

Triggered before a request is made but after a connection is set up

Changes:

- callback: Update docs and callback for pre-request callback
- Add documentation for CURLOPT_PREREQDATA and CURLOPT_PREREQFUNCTION,
- Add redirect test and callback failure test
- Note that the function may be called multiple times on a redirection
- Disable new 2086 test due to Windows weirdness

Closes #7477

1 files changed, 22 insertions, 0 deletions

diff --git a/lib/multi.c b/lib/multi.c
index 68c1a64d5..f31b25262 100644
--- a/lib/multi.c
+++ b/lib/multi.c
@@ -2028,6 +2028,28 @@ static CURLMcode multi_runsingle(struct Curl_multi *multi,
       break;
 
     case MSTATE_DO:
+      if(data->set.fprereq) {
+        int prereq_rc;
+
+        /* call the prerequest callback function */
+        Curl_set_in_callback(data, true);
+        prereq_rc = data->set.fprereq(data->set.prereq_userp,
+                                      data->info.conn_primary_ip,
+                                      data->info.conn_local_ip,
+                                      data->info.conn_primary_port,
+                                      data->info.conn_local_port);
+        Curl_set_in_callback(data, false);
+        if(prereq_rc != CURL_PREREQFUNC_OK) {
+          failf(data, "operation aborted by pre-request callback");
+          /* failure in pre-request callback - don't do any other processing */
+          result = CURLE_ABORTED_BY_CALLBACK;
+          Curl_posttransfer(data);
+          multi_done(data, result, FALSE);
+          stream_error = TRUE;
+          break;
+        }
+      }
+
       if(data->set.connect_only) {
         /* keep connection open for application to use the socket */
         connkeep(data->conn, "CONNECT_ONLY");