[PATCH] Workaround for "configuration file test failed" under OpenVZ

[Maxim Dounin]

Hello!

On Thu, Jul 30, 2015 at 01:44:15AM +0300, Gena Makhomed wrote:

> # HG changeset patch
> # User Gena Makhomed <gmm at csdoc.com>
> # Date 1437674403 14400
> #      Thu Jul 23 14:00:03 2015 -0400
> # Node ID 57ac65580b5bba0cb4bb61dca9d63daec0ceb14c
> # Parent  341e4303d25be159d4773b819d0ec055ba711afb
> Workaround for "configuration file test failed" under OpenVZ.
> 
> nginx configuration test failed:

[...]

Here is the patch with slightly updated commit log and a comment 
added to the code.  Please take a look if it looks fine to you.

# HG changeset patch
# User Gena Makhomed <gmm at csdoc.com>
# Date 1437674403 14400
#      Thu Jul 23 14:00:03 2015 -0400
# Node ID 3096ae76ba4726a5138e9e7161428c7afea67c0f
# Parent  b544f8e0d9214560a6acddbb0f40db5146e9463d
Workaround for "configuration file test failed" under OpenVZ.

If nginx was used under OpenVZ and a container with nginx was suspended
and resumed, configuration tests started to fail because of EADDRINUSE
returned from listen() instead of bind():

# nginx -t
nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
nginx: [emerg] listen() to 0.0.0.0:80, backlog 511 failed (98: Address already in use)
nginx: configuration file /etc/nginx/nginx.conf test failed

With this change EADDRINUSE errors returned by listen() are handled
similarly to errors returned by bind(), and configuration tests work
fine in the same environment:

# nginx -t
nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
nginx: configuration file /etc/nginx/nginx.conf test is successful

More details about OpenVZ suspend/resume bug:
https://bugzilla.openvz.org/show_bug.cgi?id=2470

diff --git a/src/core/ngx_connection.c b/src/core/ngx_connection.c
--- a/src/core/ngx_connection.c
+++ b/src/core/ngx_connection.c
@@ -567,9 +567,19 @@ ngx_open_listening_sockets(ngx_cycle_t *
 #endif
 
             if (listen(s, ls[i].backlog) == -1) {
-                ngx_log_error(NGX_LOG_EMERG, log, ngx_socket_errno,
-                              "listen() to %V, backlog %d failed",
-                              &ls[i].addr_text, ls[i].backlog);
+                err = ngx_socket_errno;
+
+                /*
+                 * on OpenVZ after suspend/resume EADDRINUSE
+                 * may be returned by listen() instead of bind(), see
+                 * https://bugzilla.openvz.org/show_bug.cgi?id=2470
+                 */
+
+                if (err != NGX_EADDRINUSE || !ngx_test_config) {
+                    ngx_log_error(NGX_LOG_EMERG, log, err,
+                                  "listen() to %V, backlog %d failed",
+                                  &ls[i].addr_text, ls[i].backlog);
+                }
 
                 if (ngx_close_socket(s) == -1) {
                     ngx_log_error(NGX_LOG_EMERG, log, ngx_socket_errno,
@@ -577,7 +587,15 @@ ngx_open_listening_sockets(ngx_cycle_t *
                                   &ls[i].addr_text);
                 }
 
-                return NGX_ERROR;
+                if (err != NGX_EADDRINUSE) {
+                    return NGX_ERROR;
+                }
+
+                if (!ngx_test_config) {
+                    failed = 1;
+                }
+
+                continue;
             }
 
             ls[i].listen = 1;

-- 
Maxim Dounin
http://nginx.org/