- STAT(tcpstat.tcps_keepprobe++);
-#ifdef TCP_COMPAT_42
- /*
- * The keepalive packet must have nonzero length
- * to get a 4.2 host to respond.
- */
- tcp_respond(tp, &tp->t_template, (struct mbuf *)NULL,
- tp->rcv_nxt - 1, tp->snd_una - 1, 0);
-#else