The recent issues with em(4) interface has shown that the old 4.4BSD

if_watchdog/if_timer interface doesn't fit modern SMP network
stack design.

Device drivers that need watchdog to monitor their hardware should
implement it theirselves.

Eventually the if_watchdog/if_timer API will be removed. For now,
warn that driver uses it.

Reviewed by:	scottl

sys/net/if.c

@@ -520,6 +520,9 @@ if_attach(struct ifnet *ifp)
 
 	/* Announce the interface. */
 	rt_ifannouncemsg(ifp, IFAN_ARRIVAL);
+
+	if (ifp->if_watchdog != NULL)
+		if_printf(ifp, "using obsoleted if_watchdog interface\n");
 }
 
 static void