ETHER: Fix tap support on OS/X

As reported in #823

sim_ether.c

@@ -2070,13 +2070,14 @@ if (0 == strncmp("tap:", savname, 4)) {
         }
       else {
         *fd_handle = (SOCKET)tun;
-        strcpy(savname, devname);
+        memmove(savname, devname, strlen(devname) + 1);
         }
 #if defined (__APPLE__)
-      if (tun < 0) {    /* Not good yet? */
+      if (tun >= 0) {       /* Good so far? */
         struct ifreq ifr;
         int s;
 
+        /* Now make sure the interface is up */
         memset (&ifr, 0, sizeof(ifr));
         ifr.ifr_addr.sa_family = AF_INET;
         strlcpy(ifr.ifr_name, savname, sizeof(ifr.ifr_name));