Upon HTTP_1_1_REQUIRED, retry the request with HTTP/1.1

[dscho]

This is a companion patch to #3345 which switches to HTTP/1.1 preemptively when we are about to try NTLM authentication.

However, with other (Negotiate) authentication it is not clear to this developer whether there is a way to make it work with HTTP/2, so let's try HTTP/2 first and fall back in case we encounter the error HTTP_1_1_REQUIRED.

This patch was developed with a lot of help by Daniel Stenberg.

(And yes, I tested this, by reverting the NTLM patch and authenticating against the same test server which I used to test the NTLM patch.)

[bagder]

./multi.c:1957:7: warning: else after closing brace on same line (BRACEELSE)
       } else if(CURLE_HTTP2_STREAM == result && data->set.errorbuffer &&
       ^

[bagder]

What do you think of this little extra dance to avoid the strstr in the error message? 0001-multi-polish-the-HTTP_1_1_REQUIRED-check.patch

(also inlined here for easier browsing)

From 2ed48bdb07fe3c5bc27a343126e68754bfd2267e Mon Sep 17 00:00:00 2001
From: Daniel Stenberg <daniel@haxx.se>
Date: Fri, 7 Dec 2018 17:22:29 +0100
Subject: [PATCH] multi: polish the HTTP_1_1_REQUIRED check

to avoid strstr() and depending of contents in the error message buffer
---
 lib/http2.c | 8 ++++++++
 lib/http2.h | 4 ++++
 lib/multi.c | 5 +++--
 3 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/lib/http2.c b/lib/http2.c
index c33bee3eb..a61d8c240 100644
--- a/lib/http2.c
+++ b/lib/http2.c
@@ -2365,10 +2365,18 @@ void Curl_http2_cleanup_dependencies(struct Curl_easy *data)
 
   if(data->set.stream_depends_on)
     Curl_http2_remove_child(data->set.stream_depends_on, data);
 }
 
+/* Only call this function for a transfer that already got a HTTP/2
+   CURLE_HTTP2_STREAM error! */
+bool Curl_h2_http_1_1_error(struct connectdata *conn)
+{
+  struct http_conn *httpc = &conn->proto.httpc;
+  return (httpc->error_code == NGHTTP2_HTTP_1_1_REQUIRED);
+}
+
 #else /* !USE_NGHTTP2 */
 
 /* Satisfy external references even if http2 is not compiled in. */
 
 #define CURL_DISABLE_TYPECHECK
diff --git a/lib/http2.h b/lib/http2.h
index 4492ec211..e1d2a79c7 100644
--- a/lib/http2.h
+++ b/lib/http2.h
@@ -57,10 +57,13 @@ CURLcode Curl_http2_add_child(struct Curl_easy *parent,
                               struct Curl_easy *child,
                               bool exclusive);
 void Curl_http2_remove_child(struct Curl_easy *parent,
                              struct Curl_easy *child);
 void Curl_http2_cleanup_dependencies(struct Curl_easy *data);
+
+/* returns true of the HTTP/2 stream error was HTTP_1_1_REQUIRED */
+bool Curl_h2_http_1_1_error(struct connectdata *conn);
 #else /* USE_NGHTTP2 */
 #define Curl_http2_init(x) CURLE_UNSUPPORTED_PROTOCOL
 #define Curl_http2_send_request(x) CURLE_UNSUPPORTED_PROTOCOL
 #define Curl_http2_request_upgrade(x,y) CURLE_UNSUPPORTED_PROTOCOL
 #define Curl_http2_setup(x) CURLE_UNSUPPORTED_PROTOCOL
@@ -72,8 +75,9 @@ void Curl_http2_cleanup_dependencies(struct Curl_easy *data);
 #define Curl_http2_done(x,y)
 #define Curl_http2_done_sending(x)
 #define Curl_http2_add_child(x, y, z)
 #define Curl_http2_remove_child(x, y)
 #define Curl_http2_cleanup_dependencies(x)
+#define Curl_h2_http_1_1_error(x) 0
 #endif
 
 #endif /* HEADER_CURL_HTTP2_H */
diff --git a/lib/multi.c b/lib/multi.c
index d36edfbd9..15fdff069 100644
--- a/lib/multi.c
+++ b/lib/multi.c
@@ -44,10 +44,11 @@
 #include "pipeline.h"
 #include "sigpipe.h"
 #include "vtls/vtls.h"
 #include "connect.h"
 #include "http_proxy.h"
+#include "http2.h"
 /* The last 3 #include files should be in this order */
 #include "curl_printf.h"
 #include "curl_memory.h"
 #include "memdebug.h"
 
@@ -1952,12 +1953,12 @@ static CURLMcode multi_runsingle(struct Curl_multi *multi,
           /* if we are to retry, set the result to OK and consider the
              request as done */
           result = CURLE_OK;
           done = TRUE;
         }
-      } else if(CURLE_HTTP2_STREAM == result && data->set.errorbuffer &&
-                strstr(data->set.errorbuffer, "HTTP_1_1_REQUIRED")) {
+      } else if((CURLE_HTTP2_STREAM == result) &&
+                Curl_h2_http_1_1_error(data->easy_conn)) {
         CURLcode ret = Curl_retry_request(data->easy_conn, &newurl);
 
         infof(data, "Forcing HTTP/1.1 for NTLM");
         data->set.httpversion = CURL_HTTP_VERSION_1_1;
 
-- 
2.19.2

[dscho]

warning: else after closing brace on same line (BRACEELSE)

Oops... ;-)

What do you think of this little extra dance to avoid the strstr in the error message? 0001-multi-polish-the-HTTP_1_1_REQUIRED-check.patch

That looks very good, thank you!

Will you make the changes and complete this PR?

[dscho]

Will you make the changes and complete this PR?

Actually, let me give it a try.

[dscho]

Actually, let me give it a try.

Done. And tested (again, reverting that NTLM patch and doing the git ls-remote <server> dance as before).

[bagder]

Thanks!

[dscho]

Thank you for your help, and I am really happy that this bug has been addressed (and that those support requests have been averted...)!