[PATCH] Ensured SIGQUIT deletes listening UNIX socket files.

[Thibault Charbonnier]

On 2/27/20 7:24 AM, Maxim Dounin wrote:
> Have you checked what happens during binary upgrade with your 
> patch?

Good call, I gave it a thought but did not bother checking, thanks for
sharing the previous patch. This one is slightly simpler.

Below is a new version of the patch covering binary upgrade edge-cases
by relying on the existence of the nginx.oldpid file.

Also attached to this email is a file I used as a test suite covering
the behavior of this patch with SIGQUIT, SIGTERM, and binary upgrade
scenarios.

# HG changeset patch
# User Thibault Charbonnier <thibaultcha at me.com>
# Date 1582764433 28800
#      Wed Feb 26 16:47:13 2020 -0800
# Node ID ec619d02801b925b4dad51515fb9668c1d993418
# Parent  4f18393a1d51bce6103ea2f1b2587900f349ba3d
Ensured SIGQUIT deletes listening UNIX socket files.

Prior to this patch, the SIGQUIT signal handling (graceful shutdown) did not
remove UNIX socket files since ngx_master_process_cycle reimplemented
listening
socket closings in lieu of using ngx_close_listening_sockets.

Since ngx_master_process_exit will call the aforementioned
ngx_close_listening_sockets, we can remove the custom implementation and now
expect listening sockets to be closed properly by
ngx_close_listening_sockets
instead.

This fixes the trac issue #753 (https://trac.nginx.org/nginx/ticket/753).

diff -r 4f18393a1d51 -r ec619d02801b src/core/ngx_connection.c
--- a/src/core/ngx_connection.c Thu Feb 20 16:51:07 2020 +0300
+++ b/src/core/ngx_connection.c Wed Feb 26 16:47:13 2020 -0800
@@ -1023,6 +1023,10 @@
     ngx_uint_t         i;
     ngx_listening_t   *ls;
     ngx_connection_t  *c;
+#if (NGX_HAVE_UNIX_DOMAIN)
+    ngx_core_conf_t   *ccf;
+    ngx_fd_t           fd;
+#endif

     if (ngx_event_flags & NGX_USE_IOCP_EVENT) {
         return;
@@ -1067,10 +1071,22 @@
         }

 #if (NGX_HAVE_UNIX_DOMAIN)
+        ccf = (ngx_core_conf_t *) ngx_get_conf(cycle->conf_ctx,
ngx_core_module);
+
+        fd = ngx_open_file(ccf->oldpid.data, NGX_FILE_RDONLY,
NGX_FILE_OPEN, 0);
+
+        if (fd != NGX_INVALID_FILE) {
+            if (ngx_close_file(fd) == NGX_FILE_ERROR) {
+                ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
+                              ngx_close_file_n " \"%s\" failed",
+                              ccf->oldpid.data);
+            }
+        }

         if (ls[i].sockaddr->sa_family == AF_UNIX
             && ngx_process <= NGX_PROCESS_MASTER
-            && ngx_new_binary == 0)
+            && ngx_new_binary == 0
+            && fd == NGX_INVALID_FILE)
         {
             u_char *name = ls[i].addr_text.data + sizeof("unix:") - 1;

diff -r 4f18393a1d51 -r ec619d02801b src/os/unix/ngx_process_cycle.c
--- a/src/os/unix/ngx_process_cycle.c   Thu Feb 20 16:51:07 2020 +0300
+++ b/src/os/unix/ngx_process_cycle.c   Wed Feb 26 16:47:13 2020 -0800
@@ -77,12 +77,11 @@
     u_char            *p;
     size_t             size;
     ngx_int_t          i;
-    ngx_uint_t         n, sigio;
+    ngx_uint_t         sigio;
     sigset_t           set;
     struct itimerval   itv;
     ngx_uint_t         live;
     ngx_msec_t         delay;
-    ngx_listening_t   *ls;
     ngx_core_conf_t   *ccf;
 >
> Previous attempt to fix this was here:
>
> http://mailman.nginx.org/pipermail/nginx-devel/2016-December/009207.html
> http://mailman.nginx.org/pipermail/nginx-devel/2016-December/009208.html
>
> Yet it failed to address binary upgrade case properly, see here:
>
> http://mailman.nginx.org/pipermail/nginx-devel/2016-December/009239.html
>

     sigemptyset(&set);
@@ -205,16 +204,6 @@
             ngx_signal_worker_processes(cycle,

ngx_signal_value(NGX_SHUTDOWN_SIGNAL));

-            ls = cycle->listening.elts;
-            for (n = 0; n < cycle->listening.nelts; n++) {
-                if (ngx_close_socket(ls[n].fd) == -1) {
-                    ngx_log_error(NGX_LOG_EMERG, cycle->log,
ngx_socket_errno,
-                                  ngx_close_socket_n " %V failed",
-                                  &ls[n].addr_text);
-                }
-            }
-            cycle->listening.nelts = 0;
-
             continue;
         }
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