iflib: netmap: enter/exit netmap mode after device stops

Avoid possible race conditions by calling nm_set_native_flags()
and nm_clear_native_flags() only after the device has been
stopped.

MFC after:	1 week

1 files changed, 8 insertions, 2 deletions

diff --git a/sys/net/iflib.c b/sys/net/iflib.c
index 4f03ee6d4b87..94178ea14af3 100644
--- a/sys/net/iflib.c
+++ b/sys/net/iflib.c
@@ -788,13 +788,19 @@ iflib_netmap_register(struct netmap_adapter *na, int onoff)
 	if (!CTX_IS_VF(ctx))
 		IFDI_CRCSTRIP_SET(ctx, onoff, iflib_crcstrip);
 
-	/* enable or disable flags and callbacks in na and ifp */
+	iflib_stop(ctx);
+
+	/*
+	 * Enable (or disable) netmap flags, and intercept (or restore)
+	 * ifp->if_transmit. This is done once the device has been stopped
+	 * to prevent race conditions.
+	 */
 	if (onoff) {
 		nm_set_native_flags(na);
 	} else {
 		nm_clear_native_flags(na);
 	}
-	iflib_stop(ctx);
+
 	iflib_init_locked(ctx);
 	IFDI_CRCSTRIP_SET(ctx, onoff, iflib_crcstrip); // XXX why twice ?
 	status = ifp->if_drv_flags & IFF_DRV_RUNNING ? 0 : 1;