tcp_output.c

			return err;
		} else {
			if (tp->urg_mode &&
			    between(tp->snd_up, tp->snd_una+1, tp->snd_una+0xFFFF))
				tcp_xmit_probe_skb(sk, TCPCB_URG);
			return tcp_xmit_probe_skb(sk, 0);
		}
	}
	return -1;
}

/* A window probe timeout has occurred.  If window is not closed send
 * a partial packet else a zero probe.
 */
void tcp_send_probe0(struct sock *sk)
{
	struct tcp_sock *tp = tcp_sk(sk);
	int err;

	err = tcp_write_wakeup(sk);

	if (tp->packets_out || !sk->sk_send_head) {
		/* Cancel probe timer, if it is not required. */
		tp->probes_out = 0;
		tp->backoff = 0;
		return;
	}

	if (err <= 0) {
		if (tp->backoff < sysctl_tcp_retries2)
			tp->backoff++;
		tp->probes_out++;
		tcp_reset_xmit_timer (sk, TCP_TIME_PROBE0, 
				      min(tp->rto << tp->backoff, TCP_RTO_MAX));
	} else {
		/* If packet was not sent due to local congestion,
		 * do not backoff and do not remember probes_out.
		 * Let local senders to fight for local resources.
		 *
		 * Use accumulated backoff yet.
		 */
		if (!tp->probes_out)
			tp->probes_out=1;
		tcp_reset_xmit_timer (sk, TCP_TIME_PROBE0, 
				      min(tp->rto << tp->backoff, TCP_RESOURCE_PROBE_INTERVAL));
	}
}

EXPORT_SYMBOL(tcp_connect);
EXPORT_SYMBOL(tcp_make_synack);
EXPORT_SYMBOL(tcp_simple_retransmit);
EXPORT_SYMBOL(tcp_sync_mss);