Socket: Remove Unix domain listen sockets at shutdown.

If we don't remove the Unix domain listen socket file then when Unit
restarts it get an error like

  2023/02/25 23:10:11 [alert] 36388#36388 bind(\"unix:/tmp/unit.sock\") failed (98: Address already in use)

This patch makes use of the listen_sockets array, that is already
allocated in the main process but never populated, to place the Unix
domain listen sockets into.

At shutdown we can then loop through this array and unlink(2) any Unix
domain sockets found therein.

Closes: <https://github.com/nginx/unit/issues/792>
Reviewed-by: Alejandro Colomar <alx@nginx.com>
Signed-off-by: Andrew Clayton <a.clayton@nginx.com>

2 files changed, 23 insertions, 2 deletions

diff --git a/src/nxt_main_process.c b/src/nxt_main_process.c
index 4c89121e..7548be9a 100644
--- a/src/nxt_main_process.c
+++ b/src/nxt_main_process.c
@@ -1182,8 +1182,9 @@ nxt_main_listening_socket(nxt_sockaddr_t *sa, nxt_listening_socket_t *ls)
     if (sa->u.sockaddr.sa_family == AF_UNIX
         && sa->u.sockaddr_un.sun_path[0] != '\0')
     {
-        char     *filename;
-        mode_t   access;
+        char          *filename;
+        mode_t        access;
+        nxt_thread_t  *thr;
 
         filename = sa->u.sockaddr_un.sun_path;
         access = (S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH);
@@ -1194,6 +1195,9 @@ nxt_main_listening_socket(nxt_sockaddr_t *sa, nxt_listening_socket_t *ls)
                                   filename, nxt_errno);
             goto fail;
         }
+
+        thr = nxt_thread();
+        nxt_runtime_listen_socket_add(thr->runtime, sa);
     }
 
 #endif
diff --git a/src/nxt_runtime.c b/src/nxt_runtime.c
index cb5fe421..739238af 100644
--- a/src/nxt_runtime.c
+++ b/src/nxt_runtime.c
@@ -563,6 +563,7 @@ nxt_runtime_exit(nxt_task_t *task, void *obj, void *data)
 
 #if (NXT_HAVE_UNIX_DOMAIN)
         {
+            size_t           i;
             nxt_sockaddr_t   *sa;
             nxt_file_name_t  *name;
 
@@ -572,6 +573,22 @@ nxt_runtime_exit(nxt_task_t *task, void *obj, void *data)
                 name = (nxt_file_name_t *) sa->u.sockaddr_un.sun_path;
                 (void) nxt_file_delete(name);
             }
+
+            for (i = 0; i < rt->listen_sockets->nelts; i++) {
+                nxt_listen_socket_t  *ls;
+
+                ls = (nxt_listen_socket_t *) rt->listen_sockets->elts + i;
+                sa = ls->sockaddr;
+
+                if (sa->u.sockaddr.sa_family != AF_UNIX
+                    || sa->u.sockaddr_un.sun_path[0] == '\0')
+                {
+                    continue;
+                }
+
+                name = (nxt_file_name_t *) sa->u.sockaddr_un.sun_path;
+                (void) nxt_file_delete(name);
+            }
         }
 #endif
     }