zebra: separate zebra ZAPI server open and accept

Separate zebra's ZAPI server socket handling into two phases:
an early phase that opens the socket, and a later phase that
starts listening for client connections.

Signed-off-by: Mark Stapp <[email protected]>
(cherry picked from commit 506097a)

zebra/main.c

@@ -445,6 +445,9 @@ int main(int argc, char **argv)
 	zebra_if_init();
 	zebra_debug_init();
 
+	/* Open Zebra API server socket */
+	zserv_open(zserv_path);
+
 	/*
 	 * Initialize NS( and implicitly the VRF module), and make kernel
 	 * routing socket. */

zebra/zserv.c

@@ -57,6 +57,7 @@ extern struct zebra_privs_t zserv_privs;
 
 /* The listener socket for clients connecting to us */
 static int zsock;
+static bool started_p;
 
 /* The lock that protects access to zapi client objects */
 static pthread_mutex_t client_mutex;
@@ -925,9 +926,16 @@ void zserv_close(void)
 
 	/* Free client list's mutex */
 	pthread_mutex_destroy(&client_mutex);
+
+	started_p = false;
 }
 
-void zserv_start(char *path)
+
+/*
+ * Open zebra's ZAPI listener socket. This is done early during startup,
+ * before zebra is ready to listen and accept client connections.
+ */
+void zserv_open(const char *path)
 {
 	int ret;
 	mode_t old_mask;
@@ -969,6 +977,26 @@ void zserv_start(char *path)
 			     path, safe_strerror(errno));
 		close(zsock);
 		zsock = -1;
+	}
+
+	umask(old_mask);
+}
+
+/*
+ * Start listening for ZAPI client connections.
+ */
+void zserv_start(const char *path)
+{
+	int ret;
+
+	/* This may be called more than once during startup - potentially once
+	 * per netns - but only do this work once.
+	 */
+	if (started_p)
+		return;
+
+	if (zsock <= 0) {
+		flog_err_sys(EC_LIB_SOCKET, "Zserv socket open failed");
 		return;
 	}
 
@@ -982,7 +1010,7 @@ void zserv_start(char *path)
 		return;
 	}
 
-	umask(old_mask);
+	started_p = true;
 
 	zserv_event(NULL, ZSERV_ACCEPT);
 }

zebra/zserv.h

@@ -253,16 +253,25 @@ extern void zserv_init(void);
  */
 extern void zserv_close(void);
 
+/*
+ * Open Zebra API server socket.
+ *
+ * Create and open the server socket.
+ *
+ * path
+ *    where to place the Unix domain socket
+ */
+extern void zserv_open(const char *path);
+
 /*
  * Start Zebra API server.
  *
- * Allocates resources, creates the server socket and begins listening on the
- * socket.
+ * Allocates resources and begins listening on the server socket.
  *
  * path
  *    where to place the Unix domain socket
  */
-extern void zserv_start(char *path);
+extern void zserv_start(const char *path);
 
 /*
  * Send a message to a connected Zebra API client.