[nginx] Upstream: fixed cache send error handling.

[Maxim Dounin]

details:   http://hg.nginx.org/nginx/rev/50169ef2f3fe
branches:  stable-1.8
changeset: 6342:50169ef2f3fe
user:      Roman Arutyunyan <arut at nginx.com>
date:      Thu Sep 03 15:09:21 2015 +0300
description:
Upstream: fixed cache send error handling.

The value of NGX_ERROR, returned from filter handlers, was treated as a generic
upstream error and changed to NGX_HTTP_INTERNAL_SERVER_ERROR before calling
ngx_http_finalize_request().  This resulted in "header already sent" alert
if header was already sent in filter handlers.

The problem appeared in 54e9b83d00f0 (1.7.5).

diffstat:

 src/http/ngx_http_upstream.c |  25 ++++++++++++++-----------
 1 files changed, 14 insertions(+), 11 deletions(-)

diffs (47 lines):

diff --git a/src/http/ngx_http_upstream.c b/src/http/ngx_http_upstream.c
--- a/src/http/ngx_http_upstream.c
+++ b/src/http/ngx_http_upstream.c
@@ -530,15 +530,24 @@ ngx_http_upstream_init_request(ngx_http_
 
         r->write_event_handler = ngx_http_request_empty_handler;
 
-        if (rc == NGX_DONE) {
-            return;
-        }
-
         if (rc == NGX_ERROR) {
             ngx_http_finalize_request(r, NGX_HTTP_INTERNAL_SERVER_ERROR);
             return;
         }
 
+        if (rc == NGX_OK) {
+            rc = ngx_http_upstream_cache_send(r, u);
+
+            if (rc == NGX_DONE) {
+                return;
+            }
+
+            if (rc == NGX_HTTP_UPSTREAM_INVALID_HEADER) {
+                rc = NGX_DECLINED;
+                r->cached = 0;
+            }
+        }
+
         if (rc != NGX_DECLINED) {
             ngx_http_finalize_request(r, rc);
             return;
@@ -833,13 +842,7 @@ ngx_http_upstream_cache(ngx_http_request
 
     case NGX_OK:
 
-        rc = ngx_http_upstream_cache_send(r, u);
-
-        if (rc != NGX_HTTP_UPSTREAM_INVALID_HEADER) {
-            return rc;
-        }
-
-        break;
+        return NGX_OK;
 
     case NGX_HTTP_CACHE_STALE: