commit bdafe984565f146c376ee674b13fb42c77c8410a
Author: Michael Osipov <michaelo@apache.org>
Date:   2019-08-05 12:39:28 +0200

    BZ 63626: mod_proxy_http uses incorrect status codes for timed out upstream requests
    
    If a status is known to time out at some point, use HTTP_GATEWAY_TIME_OUT
    rather than HTTP_BAD_GATEWAY because we know that the connection has been
    established and the upstream server has received our request.

diff --git a/modules/proxy/mod_proxy.h b/modules/proxy/mod_proxy.h
index 895b937088..18c5e0515f 100644
--- a/modules/proxy/mod_proxy.h
+++ b/modules/proxy/mod_proxy.h
@@ -1087,6 +1087,18 @@ PROXY_DECLARE(int) ap_proxy_connection_reusable(proxy_conn_rec *conn);
 PROXY_DECLARE(void) ap_proxy_backend_broke(request_rec *r,
                                            apr_bucket_brigade *brigade);
 
+/**
+ * Signal the upstream chain that the connection to the backend broke in the
+ * middle of the response. This is done by sending an error bucket with
+ * status supplied from error and an EOS bucket up the filter chain.
+ * @param r       current request record of client request
+ * @param brigade The brigade that is sent through the output filter chain
+ * @param error   The HTTP error code to put in the bucket
+ */
+PROXY_DECLARE(void) ap_proxy_backend_broke_ex(request_rec *r,
+                                              apr_bucket_brigade *brigade,
+                                              int error);
+
 /**
  * Return a hash based on the passed string
  * @param str     string to produce hash from
diff --git a/modules/proxy/mod_proxy_http.c b/modules/proxy/mod_proxy_http.c
index e94bf26d41..7999c78686 100644
--- a/modules/proxy/mod_proxy_http.c
+++ b/modules/proxy/mod_proxy_http.c
@@ -1302,7 +1302,9 @@ int ap_proxy_http_process_response(proxy_http_req_t *req)
                                    " failed.",
                                    backend->hostname, backend->port);
             }
-            return ap_proxyerror(r, HTTP_BAD_GATEWAY,
+            return ap_proxyerror(r, APR_STATUS_IS_TIMEUP(rc)
+                                        ? HTTP_GATEWAY_TIME_OUT
+                                        : HTTP_BAD_GATEWAY,
                                  "Error reading from remote server");
         }
         /* XXX: Is this a real headers length send from remote? */
@@ -1759,12 +1761,12 @@ int ap_proxy_http_process_response(proxy_http_req_t *req)
                     }
                     else if (rv != APR_SUCCESS) {
                         /* In this case, we are in real trouble because
-                         * our backend bailed on us. Pass along a 502 error
+                         * our backend bailed on us. Pass along a 504 error
                          * error bucket
                          */
                         ap_log_rerror(APLOG_MARK, APLOG_ERR, rv, r, APLOGNO(01110)
                                       "error reading response");
-                        ap_proxy_backend_broke(r, bb);
+                        ap_proxy_backend_broke_ex(r, bb, HTTP_GATEWAY_TIME_OUT);
                         ap_pass_brigade(r->output_filters, bb);
                         backend_broke = 1;
                         backend->close = 1;
diff --git a/modules/proxy/proxy_util.c b/modules/proxy/proxy_util.c
index e7ffe33f21..12642ad297 100644
--- a/modules/proxy/proxy_util.c
+++ b/modules/proxy/proxy_util.c
@@ -3322,6 +3322,13 @@ int ap_proxy_lb_workers(void)
 
 PROXY_DECLARE(void) ap_proxy_backend_broke(request_rec *r,
                                            apr_bucket_brigade *brigade)
+{
+    ap_proxy_backend_broke_ex(r, brigade, HTTP_BAD_GATEWAY);
+}
+
+PROXY_DECLARE(void) ap_proxy_backend_broke_ex(request_rec *r,
+                                              apr_bucket_brigade *brigade,
+                                              int error)
 {
     apr_bucket *e;
     conn_rec *c = r->connection;
@@ -3333,8 +3340,7 @@ PROXY_DECLARE(void) ap_proxy_backend_broke(request_rec *r,
      */
     if (r->main)
         r->main->no_cache = 1;
-    e = ap_bucket_error_create(HTTP_BAD_GATEWAY, NULL, c->pool,
-                               c->bucket_alloc);
+    e = ap_bucket_error_create(error, NULL, c->pool, c->bucket_alloc);
     APR_BRIGADE_INSERT_TAIL(brigade, e);
     e = apr_bucket_eos_create(c->bucket_alloc);
     APR_BRIGADE_INSERT_TAIL(brigade, e);