third_party/tcplp/bsdtcp/tcp_reass.c - third_party/openthread - Git at Google

 /*-
  * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995
  *	The Regents of the University of California.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  * 4. Neither the name of the University nor the names of its contributors
  *    may be used to endorse or promote products derived from this software
  *    without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
  *	@(#)tcp_input.c	8.12 (Berkeley) 5/24/95
  */

 #include "../tcplp.h"
 #include "../lib/bitmap.h"
 #include "../lib/cbuf.h"
 #include "tcp.h"
 #include "tcp_fsm.h"
 #include "tcp_seq.h"
 #include "tcp_var.h"

 /*
  * samkumar: Segments are only reassembled within the window; data outside the
  * window is thrown away. So, the total amount of reassembly data cannot exceed
  * the size of the receive window.
  *
  * I have essentially rewritten it to use TCPlp's data structure for the
  * reassembly buffer. I have kept the original code as a comment below this
  * function, for reference.
  *
  * Looking at the usage of this function in tcp_input, this just has to set
  * *tlenp to 0 if the received segment is already completely buffered; it does
  * not need to update it if only part of the segment is trimmed off.
  */
 int
 tcp_reass(struct tcpcb* tp, struct tcphdr* th, int* tlenp, otMessage* data, off_t data_offset, struct tcplp_signals* sig)
 {
 	size_t mergeable, written;
 	size_t offset;
 	size_t start_index;
 	size_t usedbefore;
 	int tlen;
 	size_t merged = 0;
 	int flags = 0;

 	/*
 	 * Call with th==NULL after become established to
 	 * force pre-ESTABLISHED data up to user socket.
 	 */
 	if (th == NULL)
 		goto present;

 	tlen = *tlenp;

 	/* Insert the new segment queue entry into place. */
 	KASSERT(SEQ_GEQ(th->th_seq, tp->rcv_nxt), ("Adding past segment to the reassembly queue"));
 	offset = (size_t) (th->th_seq - tp->rcv_nxt);

 	if (cbuf_reass_count_set(&tp->recvbuf, (size_t) offset, tp->reassbmp, tlen) >= (size_t) tlen) {
 		*tlenp = 0;
 		goto present;
 	}
 	written = cbuf_reass_write(&tp->recvbuf, (size_t) offset, data, data_offset, tlen, tp->reassbmp, &start_index, cbuf_copy_from_message);

 	if ((th->th_flags & TH_FIN) && (tp->reass_fin_index == -1)) {
 		tp->reass_fin_index = (int16_t) (start_index + tlen);
 	}
 	KASSERT(written == tlen, ("Reassembly write out of bounds: tried to write %d, but wrote %d", tlen, (int) written));

 present:
 	/*
 	 * Present data to user, advancing rcv_nxt through
 	 * completed sequence space.
 	 */
 	mergeable = cbuf_reass_count_set(&tp->recvbuf, 0, tp->reassbmp, (size_t) 0xFFFFFFFF);
 	usedbefore = cbuf_used_space(&tp->recvbuf);
 	if (!tpiscantrcv(tp) || usedbefore == 0) {
 		/* If usedbefore == 0, but we can't receive more, then we still need to move the buffer
 		   along by merging and then popping, in case we receive a FIN later on. */
 		if (tp->reass_fin_index >= 0 && cbuf_reass_within_offset(&tp->recvbuf, mergeable, (size_t) tp->reass_fin_index)) {
 			tp->reass_fin_index = -2; // So we won't consider any more FINs
 			flags = TH_FIN;
 		}
 		merged = cbuf_reass_merge(&tp->recvbuf, mergeable, tp->reassbmp);
 		KASSERT(merged == mergeable, ("Reassembly merge out of bounds: tried to merge %d, but merged %d", (int) mergeable, (int) merged));
 		if (tpiscantrcv(tp)) {
 			cbuf_pop(&tp->recvbuf, merged); // So no data really enters the buffer
 		} else if (merged > 0) {
 			sig->recvbuf_added = true;
 		}
 	} else {
 		/* If there is data in the buffer AND we can't receive more, then that must be because we received a FIN,
 		   but the user hasn't yet emptied the buffer of its contents. */
 		KASSERT (tp->reass_fin_index == -2, ("Can't receive more, and data in buffer, but haven't received a FIN"));
 	}

 	tp->rcv_nxt += mergeable;

 	return flags;
 }
 #if 0
 int
 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m)
 {
 	struct tseg_qent *q;
 	struct tseg_qent *p = NULL;
 	struct tseg_qent *nq;
 	struct tseg_qent *te = NULL;
 	struct socket *so = tp->t_inpcb->inp_socket;
 	char *s = NULL;
 	int flags;
 	struct tseg_qent tqs;

 	INP_WLOCK_ASSERT(tp->t_inpcb);

 	/*
 	 * XXX: tcp_reass() is rather inefficient with its data structures
 	 * and should be rewritten (see NetBSD for optimizations).
 	 */

 	/*
 	 * Call with th==NULL after become established to
 	 * force pre-ESTABLISHED data up to user socket.
 	 */
 	if (th == NULL)
 		goto present;

 	/*
 	 * Limit the number of segments that can be queued to reduce the
 	 * potential for mbuf exhaustion. For best performance, we want to be
 	 * able to queue a full window's worth of segments. The size of the
 	 * socket receive buffer determines our advertised window and grows
 	 * automatically when socket buffer autotuning is enabled. Use it as the
 	 * basis for our queue limit.
 	 * Always let the missing segment through which caused this queue.
 	 * NB: Access to the socket buffer is left intentionally unlocked as we
 	 * can tolerate stale information here.
 	 *
 	 * XXXLAS: Using sbspace(so->so_rcv) instead of so->so_rcv.sb_hiwat
 	 * should work but causes packets to be dropped when they shouldn't.
 	 * Investigate why and re-evaluate the below limit after the behaviour
 	 * is understood.
 	 */
 	if ((th->th_seq != tp->rcv_nxt || !TCPS_HAVEESTABLISHED(tp->t_state)) &&
 	    tp->t_segqlen >= (so->so_rcv.sb_hiwat / tp->t_maxseg) + 1) {
 		TCPSTAT_INC(tcps_rcvreassfull);
 		*tlenp = 0;
 		if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL, NULL))) {
 			log(LOG_DEBUG, "%s; %s: queue limit reached, "
 			    "segment dropped\n", s, __func__);
 			free(s, M_TCPLOG);
 		}
 		m_freem(m);
 		return (0);
 	}

 	/*
 	 * Allocate a new queue entry. If we can't, or hit the zone limit
 	 * just drop the pkt.
 	 *
 	 * Use a temporary structure on the stack for the missing segment
 	 * when the zone is exhausted. Otherwise we may get stuck.
 	 */
 	te = uma_zalloc(tcp_reass_zone, M_NOWAIT);
 	if (te == NULL) {
 		if (th->th_seq != tp->rcv_nxt || !TCPS_HAVEESTABLISHED(tp->t_state)) {
 			TCPSTAT_INC(tcps_rcvmemdrop);
 			m_freem(m);
 			*tlenp = 0;
 			if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL,
 			    NULL))) {
 				log(LOG_DEBUG, "%s; %s: global zone limit "
 				    "reached, segment dropped\n", s, __func__);
 				free(s, M_TCPLOG);
 			}
 			return (0);
 		} else {
 			bzero(&tqs, sizeof(struct tseg_qent));
 			te = &tqs;
 			if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL,
 			    NULL))) {
 				log(LOG_DEBUG,
 				    "%s; %s: global zone limit reached, using "
 				    "stack for missing segment\n", s, __func__);
 				free(s, M_TCPLOG);
 			}
 		}
 	}
 	tp->t_segqlen++;

 	/*
 	 * Find a segment which begins after this one does.
 	 */
 	LIST_FOREACH(q, &tp->t_segq, tqe_q) {
 		if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
 			break;
 		p = q;
 	}

 	/*
 	 * If there is a preceding segment, it may provide some of
 	 * our data already.  If so, drop the data from the incoming
 	 * segment.  If it provides all of our data, drop us.
 	 */
 	if (p != NULL) {
 		int i;
 		/* conversion to int (in i) handles seq wraparound */
 		i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
 		if (i > 0) {
 			if (i >= *tlenp) {
 				TCPSTAT_INC(tcps_rcvduppack);
 				TCPSTAT_ADD(tcps_rcvdupbyte, *tlenp);
 				m_freem(m);
 				if (te != &tqs)
 					uma_zfree(tcp_reass_zone, te);
 				tp->t_segqlen--;
 				/*
 				 * Try to present any queued data
 				 * at the left window edge to the user.
 				 * This is needed after the 3-WHS
 				 * completes.
 				 */
 				goto present;	/* ??? */
 			}
 			m_adj(m, i);
 			*tlenp -= i;
 			th->th_seq += i;
 		}
 	}
 	tp->t_rcvoopack++;
 	TCPSTAT_INC(tcps_rcvoopack);
 	TCPSTAT_ADD(tcps_rcvoobyte, *tlenp);

 	/*
 	 * While we overlap succeeding segments trim them or,
 	 * if they are completely covered, dequeue them.
 	 */
 	while (q) {
 		int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
 		if (i <= 0)
 			break;
 		if (i < q->tqe_len) {
 			q->tqe_th->th_seq += i;
 			q->tqe_len -= i;
 			m_adj(q->tqe_m, i);
 			break;
 		}

 		nq = LIST_NEXT(q, tqe_q);
 		LIST_REMOVE(q, tqe_q);
 		m_freem(q->tqe_m);
 		uma_zfree(tcp_reass_zone, q);
 		tp->t_segqlen--;
 		q = nq;
 	}

 	/* Insert the new segment queue entry into place. */
 	te->tqe_m = m;
 	te->tqe_th = th;
 	te->tqe_len = *tlenp;

 	if (p == NULL) {
 		LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q);
 	} else {
 		KASSERT(te != &tqs, ("%s: temporary stack based entry not "
 		    "first element in queue", __func__));
 		LIST_INSERT_AFTER(p, te, tqe_q);
 	}

 present:
 	/*
 	 * Present data to user, advancing rcv_nxt through
 	 * completed sequence space.
 	 */
 	if (!TCPS_HAVEESTABLISHED(tp->t_state))
 		return (0);
 	q = LIST_FIRST(&tp->t_segq);
 	if (!q || q->tqe_th->th_seq != tp->rcv_nxt)
 		return (0);
 	SOCKBUF_LOCK(&so->so_rcv);
 	do {
 		tp->rcv_nxt += q->tqe_len;
 		flags = q->tqe_th->th_flags & TH_FIN;
 		nq = LIST_NEXT(q, tqe_q);
 		LIST_REMOVE(q, tqe_q);
 		if (so->so_rcv.sb_state & SBS_CANTRCVMORE)
 			m_freem(q->tqe_m);
 		else
 			sbappendstream_locked(&so->so_rcv, q->tqe_m, 0);
 		if (q != &tqs)
 			uma_zfree(tcp_reass_zone, q);
 		tp->t_segqlen--;
 		q = nq;
 	} while (q && q->tqe_th->th_seq == tp->rcv_nxt);
 	sorwakeup_locked(so);
 	return (flags);
 }
 #endif
	/*-
	* Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995
	* The Regents of the University of California. All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	* 4. Neither the name of the University nor the names of its contributors
	* may be used to endorse or promote products derived from this software
	* without specific prior written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	* SUCH DAMAGE.
	*
	* @(#)tcp_input.c 8.12 (Berkeley) 5/24/95
	*/

	#include "../tcplp.h"
	#include "../lib/bitmap.h"
	#include "../lib/cbuf.h"
	#include "tcp.h"
	#include "tcp_fsm.h"
	#include "tcp_seq.h"
	#include "tcp_var.h"

	/*
	* samkumar: Segments are only reassembled within the window; data outside the
	* window is thrown away. So, the total amount of reassembly data cannot exceed
	* the size of the receive window.
	*
	* I have essentially rewritten it to use TCPlp's data structure for the
	* reassembly buffer. I have kept the original code as a comment below this
	* function, for reference.
	*
	* Looking at the usage of this function in tcp_input, this just has to set
	* *tlenp to 0 if the received segment is already completely buffered; it does
	* not need to update it if only part of the segment is trimmed off.
	*/
	int
	tcp_reass(struct tcpcb* tp, struct tcphdr* th, int* tlenp, otMessage* data, off_t data_offset, struct tcplp_signals* sig)
	{
	size_t mergeable, written;
	size_t offset;
	size_t start_index;
	size_t usedbefore;
	int tlen;
	size_t merged = 0;
	int flags = 0;

	/*
	* Call with th==NULL after become established to
	* force pre-ESTABLISHED data up to user socket.
	*/
	if (th == NULL)
	goto present;

	tlen = *tlenp;

	/* Insert the new segment queue entry into place. */
	KASSERT(SEQ_GEQ(th->th_seq, tp->rcv_nxt), ("Adding past segment to the reassembly queue"));
	offset = (size_t) (th->th_seq - tp->rcv_nxt);

	if (cbuf_reass_count_set(&tp->recvbuf, (size_t) offset, tp->reassbmp, tlen) >= (size_t) tlen) {
	*tlenp = 0;
	goto present;
	}
	written = cbuf_reass_write(&tp->recvbuf, (size_t) offset, data, data_offset, tlen, tp->reassbmp, &start_index, cbuf_copy_from_message);

	if ((th->th_flags & TH_FIN) && (tp->reass_fin_index == -1)) {
	tp->reass_fin_index = (int16_t) (start_index + tlen);
	}
	KASSERT(written == tlen, ("Reassembly write out of bounds: tried to write %d, but wrote %d", tlen, (int) written));

	present:
	/*
	* Present data to user, advancing rcv_nxt through
	* completed sequence space.
	*/
	mergeable = cbuf_reass_count_set(&tp->recvbuf, 0, tp->reassbmp, (size_t) 0xFFFFFFFF);
	usedbefore = cbuf_used_space(&tp->recvbuf);
	if (!tpiscantrcv(tp) \|\| usedbefore == 0) {
	/* If usedbefore == 0, but we can't receive more, then we still need to move the buffer
	along by merging and then popping, in case we receive a FIN later on. */
	if (tp->reass_fin_index >= 0 && cbuf_reass_within_offset(&tp->recvbuf, mergeable, (size_t) tp->reass_fin_index)) {
	tp->reass_fin_index = -2; // So we won't consider any more FINs
	flags = TH_FIN;
	}
	merged = cbuf_reass_merge(&tp->recvbuf, mergeable, tp->reassbmp);
	KASSERT(merged == mergeable, ("Reassembly merge out of bounds: tried to merge %d, but merged %d", (int) mergeable, (int) merged));
	if (tpiscantrcv(tp)) {
	cbuf_pop(&tp->recvbuf, merged); // So no data really enters the buffer
	} else if (merged > 0) {
	sig->recvbuf_added = true;
	}
	} else {
	/* If there is data in the buffer AND we can't receive more, then that must be because we received a FIN,
	but the user hasn't yet emptied the buffer of its contents. */
	KASSERT (tp->reass_fin_index == -2, ("Can't receive more, and data in buffer, but haven't received a FIN"));
	}

	tp->rcv_nxt += mergeable;

	return flags;
	}
	#if 0
	int
	tcp_reass(struct tcpcb tp, struct tcphdr th, int tlenp, struct mbuf m)
	{
	struct tseg_qent *q;
	struct tseg_qent *p = NULL;
	struct tseg_qent *nq;
	struct tseg_qent *te = NULL;
	struct socket *so = tp->t_inpcb->inp_socket;
	char *s = NULL;
	int flags;
	struct tseg_qent tqs;

	INP_WLOCK_ASSERT(tp->t_inpcb);

	/*
	* XXX: tcp_reass() is rather inefficient with its data structures
	* and should be rewritten (see NetBSD for optimizations).
	*/

	/*
	* Call with th==NULL after become established to
	* force pre-ESTABLISHED data up to user socket.
	*/
	if (th == NULL)
	goto present;

	/*
	* Limit the number of segments that can be queued to reduce the
	* potential for mbuf exhaustion. For best performance, we want to be
	* able to queue a full window's worth of segments. The size of the
	* socket receive buffer determines our advertised window and grows
	* automatically when socket buffer autotuning is enabled. Use it as the
	* basis for our queue limit.
	* Always let the missing segment through which caused this queue.
	* NB: Access to the socket buffer is left intentionally unlocked as we
	* can tolerate stale information here.
	*
	* XXXLAS: Using sbspace(so->so_rcv) instead of so->so_rcv.sb_hiwat
	* should work but causes packets to be dropped when they shouldn't.
	* Investigate why and re-evaluate the below limit after the behaviour
	* is understood.
	*/
	if ((th->th_seq != tp->rcv_nxt \|\| !TCPS_HAVEESTABLISHED(tp->t_state)) &&
	tp->t_segqlen >= (so->so_rcv.sb_hiwat / tp->t_maxseg) + 1) {
	TCPSTAT_INC(tcps_rcvreassfull);
	*tlenp = 0;
	if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL, NULL))) {
	log(LOG_DEBUG, "%s; %s: queue limit reached, "
	"segment dropped\n", s, __func__);
	free(s, M_TCPLOG);
	}
	m_freem(m);
	return (0);
	}

	/*
	* Allocate a new queue entry. If we can't, or hit the zone limit
	* just drop the pkt.
	*
	* Use a temporary structure on the stack for the missing segment
	* when the zone is exhausted. Otherwise we may get stuck.
	*/
	te = uma_zalloc(tcp_reass_zone, M_NOWAIT);
	if (te == NULL) {
	if (th->th_seq != tp->rcv_nxt \|\| !TCPS_HAVEESTABLISHED(tp->t_state)) {
	TCPSTAT_INC(tcps_rcvmemdrop);
	m_freem(m);
	*tlenp = 0;
	if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL,
	NULL))) {
	log(LOG_DEBUG, "%s; %s: global zone limit "
	"reached, segment dropped\n", s, __func__);
	free(s, M_TCPLOG);
	}
	return (0);
	} else {
	bzero(&tqs, sizeof(struct tseg_qent));
	te = &tqs;
	if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL,
	NULL))) {
	log(LOG_DEBUG,
	"%s; %s: global zone limit reached, using "
	"stack for missing segment\n", s, __func__);
	free(s, M_TCPLOG);
	}
	}
	}
	tp->t_segqlen++;

	/*
	* Find a segment which begins after this one does.
	*/
	LIST_FOREACH(q, &tp->t_segq, tqe_q) {
	if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
	break;
	p = q;
	}

	/*
	* If there is a preceding segment, it may provide some of
	* our data already. If so, drop the data from the incoming
	* segment. If it provides all of our data, drop us.
	*/
	if (p != NULL) {
	int i;
	/* conversion to int (in i) handles seq wraparound */
	i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
	if (i > 0) {
	if (i >= *tlenp) {
	TCPSTAT_INC(tcps_rcvduppack);
	TCPSTAT_ADD(tcps_rcvdupbyte, *tlenp);
	m_freem(m);
	if (te != &tqs)
	uma_zfree(tcp_reass_zone, te);
	tp->t_segqlen--;
	/*
	* Try to present any queued data
	* at the left window edge to the user.
	* This is needed after the 3-WHS
	* completes.
	*/
	goto present; /* ??? */
	}
	m_adj(m, i);
	*tlenp -= i;
	th->th_seq += i;
	}
	}
	tp->t_rcvoopack++;
	TCPSTAT_INC(tcps_rcvoopack);
	TCPSTAT_ADD(tcps_rcvoobyte, *tlenp);

	/*
	* While we overlap succeeding segments trim them or,
	* if they are completely covered, dequeue them.
	*/
	while (q) {
	int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
	if (i <= 0)
	break;
	if (i < q->tqe_len) {
	q->tqe_th->th_seq += i;
	q->tqe_len -= i;
	m_adj(q->tqe_m, i);
	break;
	}

	nq = LIST_NEXT(q, tqe_q);
	LIST_REMOVE(q, tqe_q);
	m_freem(q->tqe_m);
	uma_zfree(tcp_reass_zone, q);
	tp->t_segqlen--;
	q = nq;
	}

	/* Insert the new segment queue entry into place. */
	te->tqe_m = m;
	te->tqe_th = th;
	te->tqe_len = *tlenp;

	if (p == NULL) {
	LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q);
	} else {
	KASSERT(te != &tqs, ("%s: temporary stack based entry not "
	"first element in queue", __func__));
	LIST_INSERT_AFTER(p, te, tqe_q);
	}

	present:
	/*
	* Present data to user, advancing rcv_nxt through
	* completed sequence space.
	*/
	if (!TCPS_HAVEESTABLISHED(tp->t_state))
	return (0);
	q = LIST_FIRST(&tp->t_segq);
	if (!q \|\| q->tqe_th->th_seq != tp->rcv_nxt)
	return (0);
	SOCKBUF_LOCK(&so->so_rcv);
	do {
	tp->rcv_nxt += q->tqe_len;
	flags = q->tqe_th->th_flags & TH_FIN;
	nq = LIST_NEXT(q, tqe_q);
	LIST_REMOVE(q, tqe_q);
	if (so->so_rcv.sb_state & SBS_CANTRCVMORE)
	m_freem(q->tqe_m);
	else
	sbappendstream_locked(&so->so_rcv, q->tqe_m, 0);
	if (q != &tqs)
	uma_zfree(tcp_reass_zone, q);
	tp->t_segqlen--;
	q = nq;
	} while (q && q->tqe_th->th_seq == tp->rcv_nxt);
	sorwakeup_locked(so);
	return (flags);
	}
	#endif