Function rack_process_data

freebsd/netinet/tcp_stacks/rack.c:8527–8802

* Return value of 1, the TCB is unlocked and most * likely gone, return value of 0, the TCP is still * locked. */

 * locked.
 */
static int
rack_process_data(struct mbuf *m, struct tcphdr *th, struct socket *so,
    struct tcpcb *tp, int32_t drop_hdrlen, int32_t tlen,
    uint32_t tiwin, int32_t thflags, int32_t nxt_pkt)
{
	/*
	 * Update window information. Don't look at window if no ACK: TAC's
	 * send garbage on first SYN.
	 */
	int32_t nsegs;
	int32_t tfo_syn;
	struct tcp_rack *rack;

	rack = (struct tcp_rack *)tp->t_fb_ptr;
	INP_WLOCK_ASSERT(tp->t_inpcb);
	nsegs = max(1, m->m_pkthdr.lro_nsegs);
	if ((thflags & TH_ACK) &&
	    (SEQ_LT(tp->snd_wl1, th->th_seq) ||
	    (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) ||
	    (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) {
		/* keep track of pure window updates */
		if (tlen == 0 &&
		    tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)
			KMOD_TCPSTAT_INC(tcps_rcvwinupd);
		tp->snd_wnd = tiwin;
		tp->snd_wl1 = th->th_seq;
		tp->snd_wl2 = th->th_ack;
		if (tp->snd_wnd > tp->max_sndwnd)
			tp->max_sndwnd = tp->snd_wnd;
		rack->r_wanted_output = 1;
	} else if (thflags & TH_ACK) {
		if ((tp->snd_wl2 == th->th_ack) && (tiwin < tp->snd_wnd)) {
			tp->snd_wnd = tiwin;
			tp->snd_wl1 = th->th_seq;
			tp->snd_wl2 = th->th_ack;
		}
	}
	if (tp->snd_wnd < ctf_outstanding(tp))
		/* The peer collapsed the window */
		rack_collapsed_window(rack);
	else if (rack->rc_has_collapsed)
		rack_un_collapse_window(rack);
	/* Was persist timer active and now we have window space? */
	if ((rack->rc_in_persist != 0) &&
	    (tp->snd_wnd >= min((rack->r_ctl.rc_high_rwnd/2),
				rack->r_ctl.rc_pace_min_segs))) {
		rack_exit_persist(tp, rack, rack->r_ctl.rc_rcvtime);
		tp->snd_nxt = tp->snd_max;
		/* Make sure we output to start the timer */
		rack->r_wanted_output = 1;
	}
	/* Do we enter persists? */
	if ((rack->rc_in_persist == 0) &&
	    (tp->snd_wnd < min((rack->r_ctl.rc_high_rwnd/2), rack->r_ctl.rc_pace_min_segs)) &&
	    TCPS_HAVEESTABLISHED(tp->t_state) &&
	    (tp->snd_max == tp->snd_una) &&
	    sbavail(&tp->t_inpcb->inp_socket->so_snd) &&
	    (sbavail(&tp->t_inpcb->inp_socket->so_snd) > tp->snd_wnd)) {