Function tcp_sack_partialack

freebsd/netinet/tcp_sack.c:786–804

* Partial ack handling within a sack recovery episode. Keeping this very * simple for now. When a partial ack is received, force snd_cwnd to a value * that will allow the sender to transmit no more than 2 segments. If * necessary, a better scheme can be adopted at a later point, but for now, * the goal is to prevent the sender from bursting a large amount of data in * the midst of sack rec

 * the midst of sack recovery.
 */
void
tcp_sack_partialack(struct tcpcb *tp, struct tcphdr *th)
{
	int num_segs = 1;
	u_int maxseg = tcp_maxseg(tp);

	INP_WLOCK_ASSERT(tp->t_inpcb);
	tcp_timer_activate(tp, TT_REXMT, 0);
	tp->t_rtttime = 0;
	/* Send one or 2 segments based on how much new data was acked. */
	if ((BYTES_THIS_ACK(tp, th) / maxseg) >= 2)
		num_segs = 2;
	tp->snd_cwnd = (tp->sackhint.sack_bytes_rexmit +
	    (tp->snd_nxt - tp->snd_recover) + num_segs * maxseg);
	if (tp->snd_cwnd > tp->snd_ssthresh)
		tp->snd_cwnd = tp->snd_ssthresh;
	tp->t_flags |= TF_ACKNOW;
	(void) tp->t_fb->tfb_tcp_output(tp);
}

#if 0
/*