patch for Richard W.M. Jones' "Curl segfault in curl_multi_perform"

h2upgrade.patch

diff --git a/lib/url.c b/lib/url.c
index 73f2da4ba..8eecfc421 100644
--- a/lib/url.c
+++ b/lib/url.c
@@ -1071,10 +1071,13 @@ ConnectionExists(struct Curl_easy *data,
                              (needle->handler->protocol & PROTO_FAMILY_HTTP)));
 #else
   bool wantProxyNTLMhttp = FALSE;
 #endif
 #endif
+  /* plain HTTP with upgrade */
+  bool h2upgrade = (data->state.httpwant == CURL_HTTP_VERSION_2_0) &&
+    (needle->handler->protocol & CURLPROTO_HTTP);
 
   *force_reuse = FALSE;
   *waitpipe = FALSE;
 
   /* Look up the bundle with all the connections to this particular host.
@@ -1133,11 +1136,11 @@ ConnectionExists(struct Curl_easy *data,
         Curl_disconnect(data, check, TRUE);
         continue;
       }
 
       if(data->set.ipver != CURL_IPRESOLVE_WHATEVER
-          && data->set.ipver != check->ip_version) {
+         && data->set.ipver != check->ip_version) {
         /* skip because the connection is not via the requested IP version */
         continue;
       }
 
       if(bundle->multiuse == BUNDLE_MULTIPLEX)
@@ -1231,10 +1234,21 @@ ConnectionExists(struct Curl_easy *data,
             continue;
         }
       }
 #endif
 
+      if(h2upgrade && !check->httpversion && canmultiplex) {
+        if(data->set.pipewait) {
+          infof(data, "Server upgrade doesn't support multiplex yet, wait");
+          *waitpipe = TRUE;
+          CONNCACHE_UNLOCK(data);
+          return FALSE; /* no re-use */
+        }
+        infof(data, "Server upgrade cannot be used");
+        continue; /* can't be used atm */
+      }
+
       if(!canmultiplex && CONN_INUSE(check))
         /* this request can't be multiplexed but the checked connection is
            already in use so we skip it */
         continue;