freebsd-skq/sys/netinet/tcp_lro.c

/*-
 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
 *
 * Copyright (c) 2007, Myricom Inc.
 * Copyright (c) 2008, Intel Corporation.
 * Copyright (c) 2012 The FreeBSD Foundation
 * Copyright (c) 2016-2021 Mellanox Technologies.
 * All rights reserved.
 *
 * Portions of this software were developed by Bjoern Zeeb
 * under sponsorship from the FreeBSD Foundation.
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include "opt_inet.h"
#include "opt_inet6.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/sockbuf.h>
#include <sys/sysctl.h>

#include <net/if.h>
#include <net/if_var.h>
#include <net/ethernet.h>
#include <net/bpf.h>
#include <net/vnet.h>

#include <netinet/in_systm.h>
#include <netinet/in.h>
#include <netinet/ip6.h>
#include <netinet/ip.h>
#include <netinet/ip_var.h>
#include <netinet/in_pcb.h>
#include <netinet6/in6_pcb.h>
#include <netinet/tcp.h>
#include <netinet/tcp_seq.h>
#include <netinet/tcp_lro.h>
#include <netinet/tcp_var.h>
#include <netinet/tcpip.h>
#include <netinet/tcp_hpts.h>
#include <netinet/tcp_log_buf.h>
#include <netinet/udp.h>
#include <netinet6/ip6_var.h>

#include <machine/in_cksum.h>

static MALLOC_DEFINE(M_LRO, "LRO", "LRO control structures");

#define	TCP_LRO_TS_OPTION \
    ntohl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) | \
	  (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)

static void	tcp_lro_rx_done(struct lro_ctrl *lc);
static int	tcp_lro_rx_common(struct lro_ctrl *lc, struct mbuf *m,
		    uint32_t csum, bool use_hash);

#ifdef TCPHPTS
static bool	do_bpf_strip_and_compress(struct inpcb *, struct lro_ctrl *,
		struct lro_entry *, struct mbuf **, struct mbuf **, struct mbuf **, bool *, bool);

#endif

SYSCTL_NODE(_net_inet_tcp, OID_AUTO, lro,  CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
    "TCP LRO");

static long tcplro_stacks_wanting_mbufq;
counter_u64_t tcp_inp_lro_direct_queue;
counter_u64_t tcp_inp_lro_wokeup_queue;
counter_u64_t tcp_inp_lro_compressed;
counter_u64_t tcp_inp_lro_locks_taken;
counter_u64_t tcp_extra_mbuf;
counter_u64_t tcp_would_have_but;
counter_u64_t tcp_comp_total;
counter_u64_t tcp_uncomp_total;

static unsigned	tcp_lro_entries = TCP_LRO_ENTRIES;
SYSCTL_UINT(_net_inet_tcp_lro, OID_AUTO, entries,
    CTLFLAG_RDTUN | CTLFLAG_MPSAFE, &tcp_lro_entries, 0,
    "default number of LRO entries");

SYSCTL_COUNTER_U64(_net_inet_tcp_lro, OID_AUTO, fullqueue, CTLFLAG_RD,
    &tcp_inp_lro_direct_queue, "Number of lro's fully queued to transport");
SYSCTL_COUNTER_U64(_net_inet_tcp_lro, OID_AUTO, wokeup, CTLFLAG_RD,
    &tcp_inp_lro_wokeup_queue, "Number of lro's where we woke up transport via hpts");
SYSCTL_COUNTER_U64(_net_inet_tcp_lro, OID_AUTO, compressed, CTLFLAG_RD,
    &tcp_inp_lro_compressed, "Number of lro's compressed and sent to transport");
SYSCTL_COUNTER_U64(_net_inet_tcp_lro, OID_AUTO, lockcnt, CTLFLAG_RD,
    &tcp_inp_lro_locks_taken, "Number of lro's inp_wlocks taken");
SYSCTL_COUNTER_U64(_net_inet_tcp_lro, OID_AUTO, extra_mbuf, CTLFLAG_RD,
    &tcp_extra_mbuf, "Number of times we had an extra compressed ack dropped into the tp");
SYSCTL_COUNTER_U64(_net_inet_tcp_lro, OID_AUTO, would_have_but, CTLFLAG_RD,
    &tcp_would_have_but, "Number of times we would have had an extra compressed, but mget failed");
SYSCTL_COUNTER_U64(_net_inet_tcp_lro, OID_AUTO, with_m_ackcmp, CTLFLAG_RD,
    &tcp_comp_total, "Number of mbufs queued with M_ACKCMP flags set");
SYSCTL_COUNTER_U64(_net_inet_tcp_lro, OID_AUTO, without_m_ackcmp, CTLFLAG_RD,
    &tcp_uncomp_total, "Number of mbufs queued without M_ACKCMP");

void
tcp_lro_reg_mbufq(void)
{
	atomic_fetchadd_long(&tcplro_stacks_wanting_mbufq, 1);
}

void
tcp_lro_dereg_mbufq(void)
{
	atomic_fetchadd_long(&tcplro_stacks_wanting_mbufq, -1);
}

static __inline void
tcp_lro_active_insert(struct lro_ctrl *lc, struct lro_head *bucket,
    struct lro_entry *le)
{

	LIST_INSERT_HEAD(&lc->lro_active, le, next);
	LIST_INSERT_HEAD(bucket, le, hash_next);
}

static __inline void
tcp_lro_active_remove(struct lro_entry *le)
{

	LIST_REMOVE(le, next);		/* active list */
	LIST_REMOVE(le, hash_next);	/* hash bucket */
}

int
tcp_lro_init(struct lro_ctrl *lc)
{
	return (tcp_lro_init_args(lc, NULL, tcp_lro_entries, 0));
}

int
tcp_lro_init_args(struct lro_ctrl *lc, struct ifnet *ifp,
    unsigned lro_entries, unsigned lro_mbufs)
{
	struct lro_entry *le;
	size_t size;
	unsigned i, elements;

	lc->lro_bad_csum = 0;
	lc->lro_queued = 0;
	lc->lro_flushed = 0;
	lc->lro_mbuf_count = 0;
	lc->lro_mbuf_max = lro_mbufs;
	lc->lro_cnt = lro_entries;
	lc->lro_ackcnt_lim = TCP_LRO_ACKCNT_MAX;
	lc->lro_length_lim = TCP_LRO_LENGTH_MAX;
	lc->ifp = ifp;
	LIST_INIT(&lc->lro_free);
	LIST_INIT(&lc->lro_active);

	/* create hash table to accelerate entry lookup */
	if (lro_entries > lro_mbufs)
		elements = lro_entries;
	else
		elements = lro_mbufs;
	lc->lro_hash = phashinit_flags(elements, M_LRO, &lc->lro_hashsz,
	    HASH_NOWAIT);
	if (lc->lro_hash == NULL) {
		memset(lc, 0, sizeof(*lc));
		return (ENOMEM);
	}

	/* compute size to allocate */
	size = (lro_mbufs * sizeof(struct lro_mbuf_sort)) +
	    (lro_entries * sizeof(*le));
	lc->lro_mbuf_data = (struct lro_mbuf_sort *)
	    malloc(size, M_LRO, M_NOWAIT | M_ZERO);

	/* check for out of memory */
	if (lc->lro_mbuf_data == NULL) {
		free(lc->lro_hash, M_LRO);
		memset(lc, 0, sizeof(*lc));
		return (ENOMEM);
	}
	/* compute offset for LRO entries */
	le = (struct lro_entry *)
	    (lc->lro_mbuf_data + lro_mbufs);

	/* setup linked list */
	for (i = 0; i != lro_entries; i++)
		LIST_INSERT_HEAD(&lc->lro_free, le + i, next);

	return (0);
}

struct vxlan_header {
	uint32_t	vxlh_flags;
	uint32_t	vxlh_vni;
};

static inline void *
tcp_lro_low_level_parser(void *ptr, struct lro_parser *parser, bool update_data, bool is_vxlan)
{
	const struct ether_vlan_header *eh;
	void *old;
	uint16_t eth_type;

	if (update_data)
		memset(parser, 0, sizeof(*parser));

	old = ptr;

	if (is_vxlan) {
		const struct vxlan_header *vxh;
		vxh = ptr;
		ptr = (uint8_t *)ptr + sizeof(*vxh);
		if (update_data) {
			parser->data.vxlan_vni =
			    vxh->vxlh_vni & htonl(0xffffff00);
		}
	}

	eh = ptr;
	if (__predict_false(eh->evl_encap_proto == htons(ETHERTYPE_VLAN))) {
		eth_type = eh->evl_proto;
		if (update_data) {
			/* strip priority and keep VLAN ID only */
			parser->data.vlan_id = eh->evl_tag & htons(EVL_VLID_MASK);
		}
		/* advance to next header */
		ptr = (uint8_t *)ptr + ETHER_HDR_LEN + ETHER_VLAN_ENCAP_LEN;
	} else {
		eth_type = eh->evl_encap_proto;
		/* advance to next header */
		ptr = (uint8_t *)ptr + ETHER_HDR_LEN;
	}

	switch (eth_type) {
#ifdef INET
	case htons(ETHERTYPE_IP):
		parser->ip4 = ptr;
		/* Ensure there are no IPv4 options. */
		if ((parser->ip4->ip_hl << 2) != sizeof (*parser->ip4))
			break;
		/* .. and the packet is not fragmented. */
		if (parser->ip4->ip_off & htons(IP_MF|IP_OFFMASK))
			break;
		ptr = (uint8_t *)ptr + (parser->ip4->ip_hl << 2);
		if (update_data) {
			parser->data.s_addr.v4 = parser->ip4->ip_src;
			parser->data.d_addr.v4 = parser->ip4->ip_dst;
		}
		switch (parser->ip4->ip_p) {
		case IPPROTO_UDP:
			parser->udp = ptr;
			if (update_data) {
				parser->data.lro_type = LRO_TYPE_IPV4_UDP;
				parser->data.s_port = parser->udp->uh_sport;
				parser->data.d_port = parser->udp->uh_dport;
			} else {
				MPASS(parser->data.lro_type == LRO_TYPE_IPV4_UDP);
			}
			ptr = ((uint8_t *)ptr + sizeof(*parser->udp));
			parser->total_hdr_len = (uint8_t *)ptr - (uint8_t *)old;
			return (ptr);
		case IPPROTO_TCP:
			parser->tcp = ptr;
			if (update_data) {
				parser->data.lro_type = LRO_TYPE_IPV4_TCP;
				parser->data.s_port = parser->tcp->th_sport;
				parser->data.d_port = parser->tcp->th_dport;
			} else {
				MPASS(parser->data.lro_type == LRO_TYPE_IPV4_TCP);
			}
			ptr = (uint8_t *)ptr + (parser->tcp->th_off << 2);
			parser->total_hdr_len = (uint8_t *)ptr - (uint8_t *)old;
			return (ptr);
		default:
			break;
		}
		break;
#endif
#ifdef INET6
	case htons(ETHERTYPE_IPV6):
		parser->ip6 = ptr;
		ptr = (uint8_t *)ptr + sizeof(*parser->ip6);
		if (update_data) {
			parser->data.s_addr.v6 = parser->ip6->ip6_src;
			parser->data.d_addr.v6 = parser->ip6->ip6_dst;
		}
		switch (parser->ip6->ip6_nxt) {
		case IPPROTO_UDP:
			parser->udp = ptr;
			if (update_data) {
				parser->data.lro_type = LRO_TYPE_IPV6_UDP;
				parser->data.s_port = parser->udp->uh_sport;
				parser->data.d_port = parser->udp->uh_dport;
			} else {
				MPASS(parser->data.lro_type == LRO_TYPE_IPV6_UDP);
			}
			ptr = (uint8_t *)ptr + sizeof(*parser->udp);
			parser->total_hdr_len = (uint8_t *)ptr - (uint8_t *)old;
			return (ptr);
		case IPPROTO_TCP:
			parser->tcp = ptr;
			if (update_data) {
				parser->data.lro_type = LRO_TYPE_IPV6_TCP;
				parser->data.s_port = parser->tcp->th_sport;
				parser->data.d_port = parser->tcp->th_dport;
			} else {
				MPASS(parser->data.lro_type == LRO_TYPE_IPV6_TCP);
			}
			ptr = (uint8_t *)ptr + (parser->tcp->th_off << 2);
			parser->total_hdr_len = (uint8_t *)ptr - (uint8_t *)old;
			return (ptr);
		default:
			break;
		}
		break;
#endif
	default:
		break;
	}
	/* Invalid packet - cannot parse */
	return (NULL);
}

static const int vxlan_csum = CSUM_INNER_L3_CALC | CSUM_INNER_L3_VALID |
    CSUM_INNER_L4_CALC | CSUM_INNER_L4_VALID;

static inline struct lro_parser *
tcp_lro_parser(struct mbuf *m, struct lro_parser *po, struct lro_parser *pi, bool update_data)
{
	void *data_ptr;

	/* Try to parse outer headers first. */
	data_ptr = tcp_lro_low_level_parser(m->m_data, po, update_data, false);
	if (data_ptr == NULL || po->total_hdr_len > m->m_len)
		return (NULL);

	if (update_data) {
		/* Store VLAN ID, if any. */
		if (__predict_false(m->m_flags & M_VLANTAG)) {
			po->data.vlan_id =
			    htons(m->m_pkthdr.ether_vtag) & htons(EVL_VLID_MASK);
		}
	}

	switch (po->data.lro_type) {
	case LRO_TYPE_IPV4_UDP:
	case LRO_TYPE_IPV6_UDP:
		/* Check for VXLAN headers. */
		if ((m->m_pkthdr.csum_flags & vxlan_csum) != vxlan_csum)
			break;

		/* Try to parse inner headers. */
		data_ptr = tcp_lro_low_level_parser(data_ptr, pi, update_data, true);
		if (data_ptr == NULL || pi->total_hdr_len > m->m_len)
			break;

		/* Verify supported header types. */
		switch (pi->data.lro_type) {
		case LRO_TYPE_IPV4_TCP:
		case LRO_TYPE_IPV6_TCP:
			return (pi);
		default:
			break;
		}
		break;
	case LRO_TYPE_IPV4_TCP:
	case LRO_TYPE_IPV6_TCP:
		if (update_data)
			memset(pi, 0, sizeof(*pi));
		return (po);
	default:
		break;
	}
	return (NULL);
}

static inline int
tcp_lro_trim_mbuf_chain(struct mbuf *m, const struct lro_parser *po)
{
	int len;

	switch (po->data.lro_type) {
#ifdef INET
	case LRO_TYPE_IPV4_TCP:
		len = ((uint8_t *)po->ip4 - (uint8_t *)m->m_data) +
		    ntohs(po->ip4->ip_len);
		break;
#endif
#ifdef INET6
	case LRO_TYPE_IPV6_TCP:
		len = ((uint8_t *)po->ip6 - (uint8_t *)m->m_data) +
		    ntohs(po->ip6->ip6_plen) + sizeof(*po->ip6);
		break;
#endif
	default:
		return (TCP_LRO_CANNOT);
	}

	/*
	 * If the frame is padded beyond the end of the IP packet,
	 * then trim the extra bytes off:
	 */
	if (__predict_true(m->m_pkthdr.len == len)) {
		return (0);
	} else if (m->m_pkthdr.len > len) {
		m_adj(m, len - m->m_pkthdr.len);
		return (0);
	}
	return (TCP_LRO_CANNOT);
}

static struct tcphdr *
tcp_lro_get_th(struct mbuf *m)
{
	return ((struct tcphdr *)((uint8_t *)m->m_data + m->m_pkthdr.lro_tcp_h_off));
}

static void
lro_free_mbuf_chain(struct mbuf *m)
{
	struct mbuf *save;

	while (m) {
		save = m->m_nextpkt;
		m->m_nextpkt = NULL;
		m_freem(m);
		m = save;
	}
}

void
tcp_lro_free(struct lro_ctrl *lc)
{
	struct lro_entry *le;
	unsigned x;

	/* reset LRO free list */
	LIST_INIT(&lc->lro_free);

	/* free active mbufs, if any */
	while ((le = LIST_FIRST(&lc->lro_active)) != NULL) {
		tcp_lro_active_remove(le);
		lro_free_mbuf_chain(le->m_head);
	}

	/* free hash table */
	free(lc->lro_hash, M_LRO);
	lc->lro_hash = NULL;
	lc->lro_hashsz = 0;

	/* free mbuf array, if any */
	for (x = 0; x != lc->lro_mbuf_count; x++)
		m_freem(lc->lro_mbuf_data[x].mb);
	lc->lro_mbuf_count = 0;

	/* free allocated memory, if any */
	free(lc->lro_mbuf_data, M_LRO);
	lc->lro_mbuf_data = NULL;
}

static uint16_t
tcp_lro_rx_csum_tcphdr(const struct tcphdr *th)
{
	const uint16_t *ptr;
	uint32_t csum;
	uint16_t len;

	csum = -th->th_sum;	/* exclude checksum field */
	len = th->th_off;
	ptr = (const uint16_t *)th;
	while (len--) {
		csum += *ptr;
		ptr++;
		csum += *ptr;
		ptr++;
	}
	while (csum > 0xffff)
		csum = (csum >> 16) + (csum & 0xffff);

	return (csum);
}

static uint16_t
tcp_lro_rx_csum_data(const struct lro_parser *pa, uint16_t tcp_csum)
{
	uint32_t c;
	uint16_t cs;

	c = tcp_csum;

	switch (pa->data.lro_type) {
#ifdef INET6
	case LRO_TYPE_IPV6_TCP:
		/* Compute full pseudo IPv6 header checksum. */
		cs = in6_cksum_pseudo(pa->ip6, ntohs(pa->ip6->ip6_plen), pa->ip6->ip6_nxt, 0);
		break;
#endif
#ifdef INET
	case LRO_TYPE_IPV4_TCP:
		/* Compute full pseudo IPv4 header checsum. */
		cs = in_addword(ntohs(pa->ip4->ip_len) - sizeof(*pa->ip4), IPPROTO_TCP);
		cs = in_pseudo(pa->ip4->ip_src.s_addr, pa->ip4->ip_dst.s_addr, htons(cs));
		break;
#endif
	default:
		cs = 0;		/* Keep compiler happy. */
		break;
	}

	/* Complement checksum. */
	cs = ~cs;
	c += cs;

	/* Remove TCP header checksum. */
	cs = ~tcp_lro_rx_csum_tcphdr(pa->tcp);
	c += cs;

	/* Compute checksum remainder. */
	while (c > 0xffff)
		c = (c >> 16) + (c & 0xffff);

	return (c);
}

static void
tcp_lro_rx_done(struct lro_ctrl *lc)
{
	struct lro_entry *le;

	while ((le = LIST_FIRST(&lc->lro_active)) != NULL) {
		tcp_lro_active_remove(le);
		tcp_lro_flush(lc, le);
	}
}

void
tcp_lro_flush_inactive(struct lro_ctrl *lc, const struct timeval *timeout)
{
	struct lro_entry *le, *le_tmp;
	sbintime_t sbt;

	if (LIST_EMPTY(&lc->lro_active))
		return;

	/* get timeout time */
	sbt = getsbinuptime() - tvtosbt(*timeout);

	LIST_FOREACH_SAFE(le, &lc->lro_active, next, le_tmp) {
		if (sbt >= le->alloc_time) {
			tcp_lro_active_remove(le);
			tcp_lro_flush(lc, le);
		}
	}
}

#ifdef INET
static int
tcp_lro_rx_ipv4(struct lro_ctrl *lc, struct mbuf *m, struct ip *ip4)
{
	uint16_t csum;

	/* Legacy IP has a header checksum that needs to be correct. */
	if (m->m_pkthdr.csum_flags & CSUM_IP_CHECKED) {
		if (__predict_false((m->m_pkthdr.csum_flags & CSUM_IP_VALID) == 0)) {
			lc->lro_bad_csum++;
			return (TCP_LRO_CANNOT);
		}
	} else {
		csum = in_cksum_hdr(ip4);
		if (__predict_false(csum != 0)) {
			lc->lro_bad_csum++;
			return (TCP_LRO_CANNOT);
		}
	}
	return (0);
}
#endif

#ifdef TCPHPTS
static void
tcp_lro_log(struct tcpcb *tp, const struct lro_ctrl *lc,
    const struct lro_entry *le, const struct mbuf *m,
    int frm, int32_t tcp_data_len, uint32_t th_seq,
    uint32_t th_ack, uint16_t th_win)
{
	if (tp->t_logstate != TCP_LOG_STATE_OFF) {
		union tcp_log_stackspecific log;
		struct timeval tv;
		uint32_t cts;

		cts = tcp_get_usecs(&tv);
		memset(&log, 0, sizeof(union tcp_log_stackspecific));
		log.u_bbr.flex8 = frm;
		log.u_bbr.flex1 = tcp_data_len;
		if (m)
			log.u_bbr.flex2 = m->m_pkthdr.len;
		else
			log.u_bbr.flex2 = 0;
		log.u_bbr.flex3 = le->m_head->m_pkthdr.lro_nsegs;
		log.u_bbr.flex4 = le->m_head->m_pkthdr.lro_tcp_d_len;
		if (le->m_head) {
			log.u_bbr.flex5 = le->m_head->m_pkthdr.len;
			log.u_bbr.delRate = le->m_head->m_flags;
			log.u_bbr.rttProp = le->m_head->m_pkthdr.rcv_tstmp;
		}
		log.u_bbr.inflight = th_seq;
		log.u_bbr.timeStamp = cts;
		log.u_bbr.epoch = le->next_seq;
		log.u_bbr.delivered = th_ack;
		log.u_bbr.lt_epoch = le->ack_seq;
		log.u_bbr.pacing_gain = th_win;
		log.u_bbr.cwnd_gain = le->window;
		log.u_bbr.cur_del_rate = (uintptr_t)m;
		log.u_bbr.bw_inuse = (uintptr_t)le->m_head;
		log.u_bbr.flex6 = sbttous(lc->lro_last_queue_time);
		log.u_bbr.flex7 = le->compressed;
		log.u_bbr.pacing_gain = le->uncompressed;
		if (in_epoch(net_epoch_preempt))
			log.u_bbr.inhpts = 1;
		else
			log.u_bbr.inhpts = 0;
		TCP_LOG_EVENTP(tp, NULL,
			       &tp->t_inpcb->inp_socket->so_rcv,
			       &tp->t_inpcb->inp_socket->so_snd,
			       TCP_LOG_LRO, 0,
			       0, &log, false, &tv);
	}
}
#endif

static inline void
tcp_lro_assign_and_checksum_16(uint16_t *ptr, uint16_t value, uint16_t *psum)
{
	uint32_t csum;

	csum = 0xffff - *ptr + value;
	while (csum > 0xffff)
		csum = (csum >> 16) + (csum & 0xffff);
	*ptr = value;
	*psum = csum;
}

static uint16_t
tcp_lro_update_checksum(const struct lro_parser *pa, const struct lro_entry *le,
    uint16_t payload_len, uint16_t delta_sum)
{
	uint32_t csum;
	uint16_t tlen;
	uint16_t temp[5] = {};

	switch (pa->data.lro_type) {
	case LRO_TYPE_IPV4_TCP:
		/* Compute new IPv4 length. */
		tlen = (pa->ip4->ip_hl << 2) + (pa->tcp->th_off << 2) + payload_len;
		tcp_lro_assign_and_checksum_16(&pa->ip4->ip_len, htons(tlen), &temp[0]);

		/* Subtract delta from current IPv4 checksum. */
		csum = pa->ip4->ip_sum + 0xffff - temp[0];
		while (csum > 0xffff)
			csum = (csum >> 16) + (csum & 0xffff);
		tcp_lro_assign_and_checksum_16(&pa->ip4->ip_sum, csum, &temp[1]);
		goto update_tcp_header;

	case LRO_TYPE_IPV6_TCP:
		/* Compute new IPv6 length. */
		tlen = (pa->tcp->th_off << 2) + payload_len;
		tcp_lro_assign_and_checksum_16(&pa->ip6->ip6_plen, htons(tlen), &temp[0]);
		goto update_tcp_header;

	case LRO_TYPE_IPV4_UDP:
		/* Compute new IPv4 length. */
		tlen = (pa->ip4->ip_hl << 2) + sizeof(*pa->udp) + payload_len;
		tcp_lro_assign_and_checksum_16(&pa->ip4->ip_len, htons(tlen), &temp[0]);

		/* Subtract delta from current IPv4 checksum. */
		csum = pa->ip4->ip_sum + 0xffff - temp[0];
		while (csum > 0xffff)
			csum = (csum >> 16) + (csum & 0xffff);
		tcp_lro_assign_and_checksum_16(&pa->ip4->ip_sum, csum, &temp[1]);
		goto update_udp_header;

	case LRO_TYPE_IPV6_UDP:
		/* Compute new IPv6 length. */
		tlen = sizeof(*pa->udp) + payload_len;
		tcp_lro_assign_and_checksum_16(&pa->ip6->ip6_plen, htons(tlen), &temp[0]);
		goto update_udp_header;

	default:
		return (0);
	}

update_tcp_header:
	/* Compute current TCP header checksum. */
	temp[2] = tcp_lro_rx_csum_tcphdr(pa->tcp);

	/* Incorporate the latest ACK into the TCP header. */
	pa->tcp->th_ack = le->ack_seq;
	pa->tcp->th_win = le->window;

	/* Incorporate latest timestamp into the TCP header. */
	if (le->timestamp != 0) {
		uint32_t *ts_ptr;

		ts_ptr = (uint32_t *)(pa->tcp + 1);
		ts_ptr[1] = htonl(le->tsval);
		ts_ptr[2] = le->tsecr;
	}

	/* Compute new TCP header checksum. */
	temp[3] = tcp_lro_rx_csum_tcphdr(pa->tcp);

	/* Compute new TCP checksum. */
	csum = pa->tcp->th_sum + 0xffff - delta_sum +
	    0xffff - temp[0] + 0xffff - temp[3] + temp[2];
	while (csum > 0xffff)
		csum = (csum >> 16) + (csum & 0xffff);

	/* Assign new TCP checksum. */
	tcp_lro_assign_and_checksum_16(&pa->tcp->th_sum, csum, &temp[4]);

	/* Compute all modififications affecting next checksum. */
	csum = temp[0] + temp[1] + 0xffff - temp[2] +
	    temp[3] + temp[4] + delta_sum;
	while (csum > 0xffff)
		csum = (csum >> 16) + (csum & 0xffff);

	/* Return delta checksum to next stage, if any. */
	return (csum);

update_udp_header:
	tlen = sizeof(*pa->udp) + payload_len;
	/* Assign new UDP length and compute checksum delta. */
	tcp_lro_assign_and_checksum_16(&pa->udp->uh_ulen, htons(tlen), &temp[2]);

	/* Check if there is a UDP checksum. */
	if (__predict_false(pa->udp->uh_sum != 0)) {
		/* Compute new UDP checksum. */
		csum = pa->udp->uh_sum + 0xffff - delta_sum +
		    0xffff - temp[0] + 0xffff - temp[2];
		while (csum > 0xffff)
			csum = (csum >> 16) + (csum & 0xffff);
		/* Assign new UDP checksum. */
		tcp_lro_assign_and_checksum_16(&pa->udp->uh_sum, csum, &temp[3]);
	}

	/* Compute all modififications affecting next checksum. */
	csum = temp[0] + temp[1] + temp[2] + temp[3] + delta_sum;
	while (csum > 0xffff)
		csum = (csum >> 16) + (csum & 0xffff);

	/* Return delta checksum to next stage, if any. */
	return (csum);
}

static void
tcp_flush_out_entry(struct lro_ctrl *lc, struct lro_entry *le)
{
	/* Check if we need to recompute any checksums. */
	if (le->m_head->m_pkthdr.lro_nsegs > 1) {
		uint16_t csum;

		switch (le->inner.data.lro_type) {
		case LRO_TYPE_IPV4_TCP:
			csum = tcp_lro_update_checksum(&le->inner, le,
			    le->m_head->m_pkthdr.lro_tcp_d_len,
			    le->m_head->m_pkthdr.lro_tcp_d_csum);
			csum = tcp_lro_update_checksum(&le->outer, NULL,
			    le->m_head->m_pkthdr.lro_tcp_d_len +
			    le->inner.total_hdr_len, csum);
			le->m_head->m_pkthdr.csum_flags = CSUM_DATA_VALID |
			    CSUM_PSEUDO_HDR | CSUM_IP_CHECKED | CSUM_IP_VALID;
			le->m_head->m_pkthdr.csum_data = 0xffff;
			break;
		case LRO_TYPE_IPV6_TCP:
			csum = tcp_lro_update_checksum(&le->inner, le,
			    le->m_head->m_pkthdr.lro_tcp_d_len,
			    le->m_head->m_pkthdr.lro_tcp_d_csum);
			csum = tcp_lro_update_checksum(&le->outer, NULL,
			    le->m_head->m_pkthdr.lro_tcp_d_len +
			    le->inner.total_hdr_len, csum);
			le->m_head->m_pkthdr.csum_flags = CSUM_DATA_VALID |
			    CSUM_PSEUDO_HDR;
			le->m_head->m_pkthdr.csum_data = 0xffff;
			break;
		case LRO_TYPE_NONE:
			switch (le->outer.data.lro_type) {
			case LRO_TYPE_IPV4_TCP:
				csum = tcp_lro_update_checksum(&le->outer, le,
				    le->m_head->m_pkthdr.lro_tcp_d_len,
				    le->m_head->m_pkthdr.lro_tcp_d_csum);
				le->m_head->m_pkthdr.csum_flags = CSUM_DATA_VALID |
				    CSUM_PSEUDO_HDR | CSUM_IP_CHECKED | CSUM_IP_VALID;
				le->m_head->m_pkthdr.csum_data = 0xffff;
				break;
			case LRO_TYPE_IPV6_TCP:
				csum = tcp_lro_update_checksum(&le->outer, le,
				    le->m_head->m_pkthdr.lro_tcp_d_len,
				    le->m_head->m_pkthdr.lro_tcp_d_csum);
				le->m_head->m_pkthdr.csum_flags = CSUM_DATA_VALID |
				    CSUM_PSEUDO_HDR;
				le->m_head->m_pkthdr.csum_data = 0xffff;
				break;
			default:
				break;
			}
			break;
		default:
			break;
		}
	}

	/*
	 * Break any chain, this is not set to NULL on the singleton
	 * case m_nextpkt points to m_head. Other case set them
	 * m_nextpkt to NULL in push_and_replace.
	 */
	le->m_head->m_nextpkt = NULL;
	lc->lro_queued += le->m_head->m_pkthdr.lro_nsegs;
	(*lc->ifp->if_input)(lc->ifp, le->m_head);
}

static void
tcp_set_entry_to_mbuf(struct lro_ctrl *lc, struct lro_entry *le,
    struct mbuf *m, struct tcphdr *th)
{
	uint32_t *ts_ptr;
	uint16_t tcp_data_len;
	uint16_t tcp_opt_len;

	ts_ptr = (uint32_t *)(th + 1);
	tcp_opt_len = (th->th_off << 2);
	tcp_opt_len -= sizeof(*th);

	/* Check if there is a timestamp option. */
	if (tcp_opt_len == 0 ||
	    __predict_false(tcp_opt_len != TCPOLEN_TSTAMP_APPA ||
	    *ts_ptr != TCP_LRO_TS_OPTION)) {
		/* We failed to find the timestamp option. */
		le->timestamp = 0;
	} else {
		le->timestamp = 1;
		le->tsval = ntohl(*(ts_ptr + 1));
		le->tsecr = *(ts_ptr + 2);
	}

	tcp_data_len = m->m_pkthdr.lro_tcp_d_len;

	/* Pull out TCP sequence numbers and window size. */
	le->next_seq = ntohl(th->th_seq) + tcp_data_len;
	le->ack_seq = th->th_ack;
	le->window = th->th_win;

	/* Setup new data pointers. */
	le->m_head = m;
	le->m_tail = m_last(m);
}

static void
tcp_push_and_replace(struct lro_ctrl *lc, struct lro_entry *le, struct mbuf *m)
{
	struct lro_parser *pa;

	/*
	 * Push up the stack of the current entry
	 * and replace it with "m".
	 */
	struct mbuf *msave;

	/* Grab off the next and save it */
	msave = le->m_head->m_nextpkt;
	le->m_head->m_nextpkt = NULL;

	/* Now push out the old entry */
	tcp_flush_out_entry(lc, le);

	/* Re-parse new header, should not fail. */
	pa = tcp_lro_parser(m, &le->outer, &le->inner, false);
	KASSERT(pa != NULL,
	    ("tcp_push_and_replace: LRO parser failed on m=%p\n", m));

	/*
	 * Now to replace the data properly in the entry
	 * we have to reset the TCP header and
	 * other fields.
	 */
	tcp_set_entry_to_mbuf(lc, le, m, pa->tcp);

	/* Restore the next list */
	m->m_nextpkt = msave;
}

static void
tcp_lro_mbuf_append_pkthdr(struct mbuf *m, const struct mbuf *p)
{
	uint32_t csum;

	if (m->m_pkthdr.lro_nsegs == 1) {
		/* Compute relative checksum. */
		csum = p->m_pkthdr.lro_tcp_d_csum;
	} else {
		/* Merge TCP data checksums. */
		csum = (uint32_t)m->m_pkthdr.lro_tcp_d_csum +
		    (uint32_t)p->m_pkthdr.lro_tcp_d_csum;
		while (csum > 0xffff)
			csum = (csum >> 16) + (csum & 0xffff);
	}

	/* Update various counters. */
	m->m_pkthdr.len += p->m_pkthdr.lro_tcp_d_len;
	m->m_pkthdr.lro_tcp_d_csum = csum;
	m->m_pkthdr.lro_tcp_d_len += p->m_pkthdr.lro_tcp_d_len;
	m->m_pkthdr.lro_nsegs += p->m_pkthdr.lro_nsegs;
}

static void
tcp_lro_condense(struct lro_ctrl *lc, struct lro_entry *le)
{
	/*
	 * Walk through the mbuf chain we
	 * have on tap and compress/condense
	 * as required.
	 */
	uint32_t *ts_ptr;
	struct mbuf *m;
	struct tcphdr *th;
	uint32_t tcp_data_len_total;
	uint32_t tcp_data_seg_total;
	uint16_t tcp_data_len;
	uint16_t tcp_opt_len;

	/*
	 * First we must check the lead (m_head)
	 * we must make sure that it is *not*
	 * something that should be sent up
	 * right away (sack etc).
	 */
again:
	m = le->m_head->m_nextpkt;
	if (m == NULL) {
		/* Just one left. */
		return;
	}

	th = tcp_lro_get_th(m);
	tcp_opt_len = (th->th_off << 2);
	tcp_opt_len -= sizeof(*th);
	ts_ptr = (uint32_t *)(th + 1);

	if (tcp_opt_len != 0 && __predict_false(tcp_opt_len != TCPOLEN_TSTAMP_APPA ||
	    *ts_ptr != TCP_LRO_TS_OPTION)) {
		/*
		 * Its not the timestamp. We can't
		 * use this guy as the head.
		 */
		le->m_head->m_nextpkt = m->m_nextpkt;
		tcp_push_and_replace(lc, le, m);
		goto again;
	}
	if ((th->th_flags & ~(TH_ACK | TH_PUSH)) != 0) {
		/*
		 * Make sure that previously seen segements/ACKs are delivered
		 * before this segment, e.g. FIN.
		 */
		le->m_head->m_nextpkt = m->m_nextpkt;
		tcp_push_and_replace(lc, le, m);
		goto again;
	}
	while((m = le->m_head->m_nextpkt) != NULL) {
		/*
		 * condense m into le, first
		 * pull m out of the list.
		 */
		le->m_head->m_nextpkt = m->m_nextpkt;
		m->m_nextpkt = NULL;
		/* Setup my data */
		tcp_data_len = m->m_pkthdr.lro_tcp_d_len;
		th = tcp_lro_get_th(m);
		ts_ptr = (uint32_t *)(th + 1);
		tcp_opt_len = (th->th_off << 2);
		tcp_opt_len -= sizeof(*th);
		tcp_data_len_total = le->m_head->m_pkthdr.lro_tcp_d_len + tcp_data_len;
		tcp_data_seg_total = le->m_head->m_pkthdr.lro_nsegs + m->m_pkthdr.lro_nsegs;

		if (tcp_data_seg_total >= lc->lro_ackcnt_lim ||
		    tcp_data_len_total >= lc->lro_length_lim) {
			/* Flush now if appending will result in overflow. */
			tcp_push_and_replace(lc, le, m);
			goto again;
		}
		if (tcp_opt_len != 0 &&
		    __predict_false(tcp_opt_len != TCPOLEN_TSTAMP_APPA ||
		    *ts_ptr != TCP_LRO_TS_OPTION)) {
			/*
			 * Maybe a sack in the new one? We need to
			 * start all over after flushing the
			 * current le. We will go up to the beginning
			 * and flush it (calling the replace again possibly
			 * or just returning).
			 */
			tcp_push_and_replace(lc, le, m);
			goto again;
		}
		if ((th->th_flags & ~(TH_ACK | TH_PUSH)) != 0) {
			tcp_push_and_replace(lc, le, m);
			goto again;
		}
		if (tcp_opt_len != 0) {
			uint32_t tsval = ntohl(*(ts_ptr + 1));
			/* Make sure timestamp values are increasing. */
			if (TSTMP_GT(le->tsval, tsval))  {
				tcp_push_and_replace(lc, le, m);
				goto again;
			}
			le->tsval = tsval;
			le->tsecr = *(ts_ptr + 2);
		}
		/* Try to append the new segment. */
		if (__predict_false(ntohl(th->th_seq) != le->next_seq ||
				    (tcp_data_len == 0 &&
				     le->ack_seq == th->th_ack &&
				     le->window == th->th_win))) {
			/* Out of order packet or duplicate ACK. */
			tcp_push_and_replace(lc, le, m);
			goto again;
		}
		if (tcp_data_len != 0 ||
		    SEQ_GT(ntohl(th->th_ack), ntohl(le->ack_seq))) {
			le->next_seq += tcp_data_len;
			le->ack_seq = th->th_ack;
			le->window = th->th_win;
		} else if (th->th_ack == le->ack_seq) {
			le->window = WIN_MAX(le->window, th->th_win);
		}

		if (tcp_data_len == 0) {
			m_freem(m);
			continue;
		}

		/* Merge TCP data checksum and length to head mbuf. */
		tcp_lro_mbuf_append_pkthdr(le->m_head, m);

		/*
		 * Adjust the mbuf so that m_data points to the first byte of
		 * the ULP payload.  Adjust the mbuf to avoid complications and
		 * append new segment to existing mbuf chain.
		 */
		m_adj(m, m->m_pkthdr.len - tcp_data_len);
		m_demote_pkthdr(m);
		le->m_tail->m_next = m;
		le->m_tail = m_last(m);
	}
}

#ifdef TCPHPTS
static void
tcp_queue_pkts(struct inpcb *inp, struct tcpcb *tp, struct lro_entry *le)
{
	INP_WLOCK_ASSERT(inp);
	if (tp->t_in_pkt == NULL) {
		/* Nothing yet there */
		tp->t_in_pkt = le->m_head;
		tp->t_tail_pkt = le->m_last_mbuf;
	} else {
		/* Already some there */
		tp->t_tail_pkt->m_nextpkt = le->m_head;
		tp->t_tail_pkt = le->m_last_mbuf;
	}
	le->m_head = NULL;
	le->m_last_mbuf = NULL;
}

static struct mbuf *
tcp_lro_get_last_if_ackcmp(struct lro_ctrl *lc, struct lro_entry *le,
    struct inpcb *inp, int32_t *new_m)
{
	struct tcpcb *tp;
	struct mbuf *m;

	tp = intotcpcb(inp);
	if (__predict_false(tp == NULL))
		return (NULL);

	/* Look at the last mbuf if any in queue */
	m = tp->t_tail_pkt;
	if (m != NULL && (m->m_flags & M_ACKCMP) != 0) {
		if (M_TRAILINGSPACE(m) >= sizeof(struct tcp_ackent)) {
			tcp_lro_log(tp, lc, le, NULL, 23, 0, 0, 0, 0);
			*new_m = 0;
			counter_u64_add(tcp_extra_mbuf, 1);
			return (m);
		} else {
			/* Mark we ran out of space */
			inp->inp_flags2 |= INP_MBUF_L_ACKS;
		}
	}
	/* Decide mbuf size. */
	if (inp->inp_flags2 & INP_MBUF_L_ACKS)
		m = m_getcl(M_NOWAIT, MT_DATA, M_ACKCMP | M_PKTHDR);
	else
		m = m_gethdr(M_NOWAIT, MT_DATA);

	if (__predict_false(m == NULL)) {
		counter_u64_add(tcp_would_have_but, 1);
		return (NULL);
	}
	counter_u64_add(tcp_comp_total, 1);
	m->m_flags |= M_ACKCMP;
	*new_m = 1;
	return (m);
}

static struct inpcb *
tcp_lro_lookup(struct ifnet *ifp, struct lro_parser *pa)
{
	struct inpcb *inp;

	NET_EPOCH_ASSERT();

	switch (pa->data.lro_type) {
#ifdef INET6
	case LRO_TYPE_IPV6_TCP:
		inp = in6_pcblookup(&V_tcbinfo,
		    &pa->data.s_addr.v6,
		    pa->data.s_port,
		    &pa->data.d_addr.v6,
		    pa->data.d_port,
		    INPLOOKUP_WLOCKPCB,
		    ifp);
		break;
#endif
#ifdef INET
	case LRO_TYPE_IPV4_TCP:
		inp = in_pcblookup(&V_tcbinfo,
		    pa->data.s_addr.v4,
		    pa->data.s_port,
		    pa->data.d_addr.v4,
		    pa->data.d_port,
		    INPLOOKUP_WLOCKPCB,
		    ifp);
		break;
#endif
	default:
		inp = NULL;
		break;
	}
	return (inp);
}

static inline bool
tcp_lro_ack_valid(struct mbuf *m, struct tcphdr *th, uint32_t **ppts, bool *other_opts)
{
	/*
	 * This function returns two bits of valuable information.
	 * a) Is what is present capable of being ack-compressed,
	 *    we can ack-compress if there is no options or just
	 *    a timestamp option, and of course the th_flags must
	 *    be correct as well.
	 * b) Our other options present such as SACK. This is
	 *    used to determine if we want to wakeup or not.
	 */
	bool ret = true;

	switch (th->th_off << 2) {
	case (sizeof(*th) + TCPOLEN_TSTAMP_APPA):
		*ppts = (uint32_t *)(th + 1);
		/* Check if we have only one timestamp option. */
		if (**ppts == TCP_LRO_TS_OPTION)
			*other_opts = false;
		else {
			*other_opts = true;
			ret = false;
		}
		break;
	case (sizeof(*th)):
		/* No options. */
		*ppts = NULL;
		*other_opts = false;
		break;
	default:
		*ppts = NULL;
		*other_opts = true;
		ret = false;
		break;
	}
	/* For ACKCMP we only accept ACK, PUSH, ECE and CWR. */
	if ((th->th_flags & ~(TH_ACK | TH_PUSH | TH_ECE | TH_CWR)) != 0)
		ret = false;
	/* If it has data on it we cannot compress it */
	if (m->m_pkthdr.lro_tcp_d_len)
		ret = false;

	/* ACK flag must be set. */
	if (!(th->th_flags & TH_ACK))
		ret = false;
	return (ret);
}

static int
tcp_lro_flush_tcphpts(struct lro_ctrl *lc, struct lro_entry *le)
{
	struct inpcb *inp;
	struct tcpcb *tp;
	struct mbuf **pp, *cmp, *mv_to;
	bool bpf_req, should_wake;

	/* Check if packet doesn't belongs to our network interface. */
	if ((tcplro_stacks_wanting_mbufq == 0) ||
	    (le->outer.data.vlan_id != 0) ||
	    (le->inner.data.lro_type != LRO_TYPE_NONE))
		return (TCP_LRO_CANNOT);

#ifdef INET6
	/*
	 * Be proactive about unspecified IPv6 address in source. As
	 * we use all-zero to indicate unbounded/unconnected pcb,
	 * unspecified IPv6 address can be used to confuse us.
	 *
	 * Note that packets with unspecified IPv6 destination is
	 * already dropped in ip6_input.
	 */
	if (__predict_false(le->outer.data.lro_type == LRO_TYPE_IPV6_TCP &&
	    IN6_IS_ADDR_UNSPECIFIED(&le->outer.data.s_addr.v6)))
		return (TCP_LRO_CANNOT);

	if (__predict_false(le->inner.data.lro_type == LRO_TYPE_IPV6_TCP &&
	    IN6_IS_ADDR_UNSPECIFIED(&le->inner.data.s_addr.v6)))
		return (TCP_LRO_CANNOT);
#endif
	/* Lookup inp, if any. */
	inp = tcp_lro_lookup(lc->ifp,
	    (le->inner.data.lro_type == LRO_TYPE_NONE) ? &le->outer : &le->inner);
	if (inp == NULL)
		return (TCP_LRO_CANNOT);

	counter_u64_add(tcp_inp_lro_locks_taken, 1);

	/* Get TCP control structure. */
	tp = intotcpcb(inp);

	/* Check if the inp is dead, Jim. */
	if (tp == NULL ||
	    (inp->inp_flags & (INP_DROPPED | INP_TIMEWAIT)) ||
	    (inp->inp_flags2 & INP_FREED)) {
		INP_WUNLOCK(inp);
		return (TCP_LRO_CANNOT);
	}

	/* Check if the transport doesn't support the needed optimizations. */
	if ((inp->inp_flags2 & (INP_SUPPORTS_MBUFQ | INP_MBUF_ACKCMP)) == 0) {
		INP_WUNLOCK(inp);
		return (TCP_LRO_CANNOT);
	}

	if (inp->inp_flags2 & INP_MBUF_QUEUE_READY)
		should_wake = false;
	else
		should_wake = true;
	/* Check if packets should be tapped to BPF. */
	bpf_req = bpf_peers_present(lc->ifp->if_bpf);

	/* Strip and compress all the incoming packets. */
	cmp = NULL;
	for (pp = &le->m_head; *pp != NULL; ) {
		mv_to = NULL;
		if (do_bpf_strip_and_compress(inp, lc, le, pp,
			 &cmp, &mv_to, &should_wake, bpf_req ) == false) {
			/* Advance to next mbuf. */
			pp = &(*pp)->m_nextpkt;
		} else if (mv_to != NULL) {
			/* We are asked to move pp up */
			pp = &mv_to->m_nextpkt;
		}
	}
	/* Update "m_last_mbuf", if any. */
	if (pp == &le->m_head)
		le->m_last_mbuf = *pp;
	else
		le->m_last_mbuf = __containerof(pp, struct mbuf, m_nextpkt);

	/* Check if any data mbufs left. */
	if (le->m_head != NULL) {
		counter_u64_add(tcp_inp_lro_direct_queue, 1);
		tcp_lro_log(tp, lc, le, NULL, 22, 1,
			    inp->inp_flags2, inp->inp_in_input, 1);
		tcp_queue_pkts(inp, tp, le);
	}
	if (should_wake) {
		/* Wakeup */
		counter_u64_add(tcp_inp_lro_wokeup_queue, 1);
		if ((*tp->t_fb->tfb_do_queued_segments)(inp->inp_socket, tp, 0))
			inp = NULL;
	}
	if (inp != NULL)
		INP_WUNLOCK(inp);
	return (0);	/* Success. */
}
#endif

void
tcp_lro_flush(struct lro_ctrl *lc, struct lro_entry *le)
{
	/* Only optimise if there are multiple packets waiting. */
#ifdef TCPHPTS
	int error;

	CURVNET_SET(lc->ifp->if_vnet);
	error = tcp_lro_flush_tcphpts(lc, le);
	CURVNET_RESTORE();
	if (error != 0) {
#endif
		tcp_lro_condense(lc, le);
		tcp_flush_out_entry(lc, le);
#ifdef TCPHPTS
	}
#endif
	lc->lro_flushed++;
	bzero(le, sizeof(*le));
	LIST_INSERT_HEAD(&lc->lro_free, le, next);
}

#ifdef HAVE_INLINE_FLSLL
#define	tcp_lro_msb_64(x) (1ULL << (flsll(x) - 1))
#else
static inline uint64_t
tcp_lro_msb_64(uint64_t x)
{
	x |= (x >> 1);
	x |= (x >> 2);
	x |= (x >> 4);
	x |= (x >> 8);
	x |= (x >> 16);
	x |= (x >> 32);
	return (x & ~(x >> 1));
}
#endif

/*
 * The tcp_lro_sort() routine is comparable to qsort(), except it has
 * a worst case complexity limit of O(MIN(N,64)*N), where N is the
 * number of elements to sort and 64 is the number of sequence bits
 * available. The algorithm is bit-slicing the 64-bit sequence number,
 * sorting one bit at a time from the most significant bit until the
 * least significant one, skipping the constant bits. This is
 * typically called a radix sort.
 */
static void
tcp_lro_sort(struct lro_mbuf_sort *parray, uint32_t size)
{
	struct lro_mbuf_sort temp;
	uint64_t ones;
	uint64_t zeros;
	uint32_t x;
	uint32_t y;

repeat:
	/* for small arrays insertion sort is faster */
	if (size <= 12) {
		for (x = 1; x < size; x++) {
			temp = parray[x];
			for (y = x; y > 0 && temp.seq < parray[y - 1].seq; y--)
				parray[y] = parray[y - 1];
			parray[y] = temp;
		}
		return;
	}

	/* compute sequence bits which are constant */
	ones = 0;
	zeros = 0;
	for (x = 0; x != size; x++) {
		ones |= parray[x].seq;
		zeros |= ~parray[x].seq;
	}

	/* compute bits which are not constant into "ones" */
	ones &= zeros;
	if (ones == 0)
		return;

	/* pick the most significant bit which is not constant */
	ones = tcp_lro_msb_64(ones);

	/*
	 * Move entries having cleared sequence bits to the beginning
	 * of the array:
	 */
	for (x = y = 0; y != size; y++) {
		/* skip set bits */
		if (parray[y].seq & ones)
			continue;
		/* swap entries */
		temp = parray[x];
		parray[x] = parray[y];
		parray[y] = temp;
		x++;
	}

	KASSERT(x != 0 && x != size, ("Memory is corrupted\n"));

	/* sort zeros */
	tcp_lro_sort(parray, x);

	/* sort ones */
	parray += x;
	size -= x;
	goto repeat;
}

void
tcp_lro_flush_all(struct lro_ctrl *lc)
{
	uint64_t seq;
	uint64_t nseq;
	unsigned x;

	/* check if no mbufs to flush */
	if (lc->lro_mbuf_count == 0)
		goto done;

	CURVNET_SET(lc->ifp->if_vnet);

	/* get current time */
	lc->lro_last_queue_time = getsbinuptime();

	/* sort all mbufs according to stream */
	tcp_lro_sort(lc->lro_mbuf_data, lc->lro_mbuf_count);

	/* input data into LRO engine, stream by stream */
	seq = 0;
	for (x = 0; x != lc->lro_mbuf_count; x++) {
		struct mbuf *mb;

		/* get mbuf */
		mb = lc->lro_mbuf_data[x].mb;

		/* get sequence number, masking away the packet index */
		nseq = lc->lro_mbuf_data[x].seq & (-1ULL << 24);

		/* check for new stream */
		if (seq != nseq) {
			seq = nseq;

			/* flush active streams */
			tcp_lro_rx_done(lc);
		}

		/* add packet to LRO engine */
		if (tcp_lro_rx_common(lc, mb, 0, false) != 0) {
			/* input packet to network layer */
			(*lc->ifp->if_input)(lc->ifp, mb);
			lc->lro_queued++;
			lc->lro_flushed++;
		}
	}
	CURVNET_RESTORE();
done:
	/* flush active streams */
	tcp_lro_rx_done(lc);

	lc->lro_mbuf_count = 0;
}

#ifdef TCPHPTS
static void
build_ack_entry(struct tcp_ackent *ae, struct tcphdr *th, struct mbuf *m,
    uint32_t *ts_ptr, uint16_t iptos)
{
	/*
	 * Given a TCP ACK, summarize it down into the small TCP ACK
	 * entry.
	 */
	ae->timestamp = m->m_pkthdr.rcv_tstmp;
	if (m->m_flags & M_TSTMP_LRO)
		ae->flags = TSTMP_LRO;
	else if (m->m_flags & M_TSTMP)
		ae->flags = TSTMP_HDWR;
	ae->seq = ntohl(th->th_seq);
	ae->ack = ntohl(th->th_ack);
	ae->flags |= th->th_flags;
	if (ts_ptr != NULL) {
		ae->ts_value = ntohl(ts_ptr[1]);
		ae->ts_echo = ntohl(ts_ptr[2]);
		ae->flags |= HAS_TSTMP;
	}
	ae->win = ntohs(th->th_win);
	ae->codepoint = iptos;
}

/*
 * Do BPF tap for either ACK_CMP packets or MBUF QUEUE type packets
 * and strip all, but the IPv4/IPv6 header.
 */
static bool
do_bpf_strip_and_compress(struct inpcb *inp, struct lro_ctrl *lc,
    struct lro_entry *le, struct mbuf **pp, struct mbuf **cmp, struct mbuf **mv_to,
    bool *should_wake, bool bpf_req)
{
	union {
		void *ptr;
		struct ip *ip4;
		struct ip6_hdr *ip6;
	} l3;
	struct mbuf *m;
	struct mbuf *nm;
	struct tcphdr *th;
	struct tcp_ackent *ack_ent;
	uint32_t *ts_ptr;
	int32_t n_mbuf;
	bool other_opts, can_compress;
	uint16_t lro_type;
	uint16_t iptos;
	int tcp_hdr_offset;
	int idx;

	/* Get current mbuf. */
	m = *pp;

	/* Let the BPF see the packet */
	if (__predict_false(bpf_req))
		ETHER_BPF_MTAP(lc->ifp, m);

	tcp_hdr_offset = m->m_pkthdr.lro_tcp_h_off;
	lro_type = le->inner.data.lro_type;
	switch (lro_type) {
	case LRO_TYPE_NONE:
		lro_type = le->outer.data.lro_type;
		switch (lro_type) {
		case LRO_TYPE_IPV4_TCP:
			tcp_hdr_offset -= sizeof(*le->outer.ip4);
			m->m_pkthdr.lro_etype = ETHERTYPE_IP;
			break;
		case LRO_TYPE_IPV6_TCP:
			tcp_hdr_offset -= sizeof(*le->outer.ip6);
			m->m_pkthdr.lro_etype = ETHERTYPE_IPV6;
			break;
		default:
			goto compressed;
		}
		break;
	case LRO_TYPE_IPV4_TCP:
		tcp_hdr_offset -= sizeof(*le->outer.ip4);
		m->m_pkthdr.lro_etype = ETHERTYPE_IP;
		break;
	case LRO_TYPE_IPV6_TCP:
		tcp_hdr_offset -= sizeof(*le->outer.ip6);
		m->m_pkthdr.lro_etype = ETHERTYPE_IPV6;
		break;
	default:
		goto compressed;
	}

	MPASS(tcp_hdr_offset >= 0);

	m_adj(m, tcp_hdr_offset);
	m->m_flags |= M_LRO_EHDRSTRP;
	m->m_flags &= ~M_ACKCMP;
	m->m_pkthdr.lro_tcp_h_off -= tcp_hdr_offset;

	th = tcp_lro_get_th(m);

	th->th_sum = 0;		/* TCP checksum is valid. */

	/* Check if ACK can be compressed */
	can_compress = tcp_lro_ack_valid(m, th, &ts_ptr, &other_opts);

	/* Now lets look at the should wake states */
	if ((other_opts == true) &&
	    ((inp->inp_flags2 & INP_DONT_SACK_QUEUE) == 0)) {
		/*
		 * If there are other options (SACK?) and the
		 * tcp endpoint has not expressly told us it does
		 * not care about SACKS, then we should wake up.
		 */
		*should_wake = true;
	}
	/* Is the ack compressable? */
	if (can_compress == false)
		goto done;
	/* Does the TCP endpoint support ACK compression? */
	if ((inp->inp_flags2 & INP_MBUF_ACKCMP) == 0)
		goto done;

	/* Lets get the TOS/traffic class field */
	l3.ptr = mtod(m, void *);
	switch (lro_type) {
	case LRO_TYPE_IPV4_TCP:
		iptos = l3.ip4->ip_tos;
		break;
	case LRO_TYPE_IPV6_TCP:
		iptos = IPV6_TRAFFIC_CLASS(l3.ip6);
		break;
	default:
		iptos = 0;	/* Keep compiler happy. */
		break;
	}
	/* Now lets get space if we don't have some already */
	if (*cmp == NULL) {
new_one:
		nm = tcp_lro_get_last_if_ackcmp(lc, le, inp, &n_mbuf);
		if (__predict_false(nm == NULL))
			goto done;
		*cmp = nm;
		if (n_mbuf) {
			/*
			 *  Link in the new cmp ack to our in-order place,
			 * first set our cmp ack's next to where we are.
			 */
			nm->m_nextpkt = m;
			(*pp) = nm;
			/*
			 * Set it up so mv_to is advanced to our
			 * compressed ack. This way the caller can
			 * advance pp to the right place.
			 */
			*mv_to = nm;
			/*
			 * Advance it here locally as well.
			 */
			pp = &nm->m_nextpkt;
		}
	} else {
		/* We have one already we are working on */
		nm = *cmp;
		if (M_TRAILINGSPACE(nm) < sizeof(struct tcp_ackent)) {
			/* We ran out of space */
			inp->inp_flags2 |= INP_MBUF_L_ACKS;
			goto new_one;
		}
	}
	MPASS(M_TRAILINGSPACE(nm) >= sizeof(struct tcp_ackent));
	counter_u64_add(tcp_inp_lro_compressed, 1);
	le->compressed++;
	/* We can add in to the one on the tail */
	ack_ent = mtod(nm, struct tcp_ackent *);
	idx = (nm->m_len / sizeof(struct tcp_ackent));
	build_ack_entry(&ack_ent[idx], th, m, ts_ptr, iptos);

	/* Bump the size of both pkt-hdr and len */
	nm->m_len += sizeof(struct tcp_ackent);
	nm->m_pkthdr.len += sizeof(struct tcp_ackent);
compressed:
	/* Advance to next mbuf before freeing. */
	*pp = m->m_nextpkt;
	m->m_nextpkt = NULL;
	m_freem(m);
	return (true);
done:
	counter_u64_add(tcp_uncomp_total, 1);
	le->uncompressed++;
	return (false);
}
#endif

static struct lro_head *
tcp_lro_rx_get_bucket(struct lro_ctrl *lc, struct mbuf *m, struct lro_parser *parser)
{
	u_long hash;

	if (M_HASHTYPE_ISHASH(m)) {
		hash = m->m_pkthdr.flowid;
	} else {
		for (unsigned i = hash = 0; i != LRO_RAW_ADDRESS_MAX; i++)
			hash += parser->data.raw[i];
	}
	return (&lc->lro_hash[hash % lc->lro_hashsz]);
}

static int
tcp_lro_rx_common(struct lro_ctrl *lc, struct mbuf *m, uint32_t csum, bool use_hash)
{
	struct lro_parser pi;	/* inner address data */
	struct lro_parser po;	/* outer address data */
	struct lro_parser *pa;	/* current parser for TCP stream */
	struct lro_entry *le;
	struct lro_head *bucket;
	struct tcphdr *th;
	int tcp_data_len;
	int tcp_opt_len;
	int error;
	uint16_t tcp_data_sum;

#ifdef INET
	/* Quickly decide if packet cannot be LRO'ed */
	if (__predict_false(V_ipforwarding != 0))
		return (TCP_LRO_CANNOT);
#endif
#ifdef INET6
	/* Quickly decide if packet cannot be LRO'ed */
	if (__predict_false(V_ip6_forwarding != 0))
		return (TCP_LRO_CANNOT);
#endif

	/* We expect a contiguous header [eh, ip, tcp]. */
	pa = tcp_lro_parser(m, &po, &pi, true);
	if (__predict_false(pa == NULL))
		return (TCP_LRO_NOT_SUPPORTED);

	/* We don't expect any padding. */
	error = tcp_lro_trim_mbuf_chain(m, pa);
	if (__predict_false(error != 0))
		return (error);

#ifdef INET
	switch (pa->data.lro_type) {
	case LRO_TYPE_IPV4_TCP:
		error = tcp_lro_rx_ipv4(lc, m, pa->ip4);
		if (__predict_false(error != 0))
			return (error);
		break;
	default:
		break;
	}
#endif
	/* If no hardware or arrival stamp on the packet add timestamp */
	if ((m->m_flags & (M_TSTMP_LRO | M_TSTMP)) == 0) {
		m->m_pkthdr.rcv_tstmp = sbttons(lc->lro_last_queue_time);
		m->m_flags |= M_TSTMP_LRO;
	}

	/* Get pointer to TCP header. */
	th = pa->tcp;

	/* Don't process SYN packets. */
	if (__predict_false(th->th_flags & TH_SYN))
		return (TCP_LRO_CANNOT);

	/* Get total TCP header length and compute payload length. */
	tcp_opt_len = (th->th_off << 2);
	tcp_data_len = m->m_pkthdr.len - ((uint8_t *)th -
	    (uint8_t *)m->m_data) - tcp_opt_len;
	tcp_opt_len -= sizeof(*th);

	/* Don't process invalid TCP headers. */
	if (__predict_false(tcp_opt_len < 0 || tcp_data_len < 0))
		return (TCP_LRO_CANNOT);

	/* Compute TCP data only checksum. */
	if (tcp_data_len == 0)
		tcp_data_sum = 0;	/* no data, no checksum */
	else if (__predict_false(csum != 0))
		tcp_data_sum = tcp_lro_rx_csum_data(pa, ~csum);
	else
		tcp_data_sum = tcp_lro_rx_csum_data(pa, ~th->th_sum);

	/* Save TCP info in mbuf. */
	m->m_nextpkt = NULL;
	m->m_pkthdr.rcvif = lc->ifp;
	m->m_pkthdr.lro_tcp_d_csum = tcp_data_sum;
	m->m_pkthdr.lro_tcp_d_len = tcp_data_len;
	m->m_pkthdr.lro_tcp_h_off = ((uint8_t *)th - (uint8_t *)m->m_data);
	m->m_pkthdr.lro_nsegs = 1;

	/* Get hash bucket. */
	if (!use_hash) {
		bucket = &lc->lro_hash[0];
	} else {
		bucket = tcp_lro_rx_get_bucket(lc, m, pa);
	}

	/* Try to find a matching previous segment. */
	LIST_FOREACH(le, bucket, hash_next) {
		/* Compare addresses and ports. */
		if (lro_address_compare(&po.data, &le->outer.data) == false ||
		    lro_address_compare(&pi.data, &le->inner.data) == false)
			continue;

		/* Check if no data and old ACK. */
		if (tcp_data_len == 0 &&
		    SEQ_LT(ntohl(th->th_ack), ntohl(le->ack_seq))) {
			m_freem(m);
			return (0);
		}

		/* Mark "m" in the last spot. */
		le->m_last_mbuf->m_nextpkt = m;
		/* Now set the tail to "m". */
		le->m_last_mbuf = m;
		return (0);
	}

	/* Try to find an empty slot. */
	if (LIST_EMPTY(&lc->lro_free))
		return (TCP_LRO_NO_ENTRIES);

	/* Start a new segment chain. */
	le = LIST_FIRST(&lc->lro_free);
	LIST_REMOVE(le, next);
	tcp_lro_active_insert(lc, bucket, le);

	/* Make sure the headers are set. */
	le->inner = pi;
	le->outer = po;

	/* Store time this entry was allocated. */
	le->alloc_time = lc->lro_last_queue_time;

	tcp_set_entry_to_mbuf(lc, le, m, th);

	/* Now set the tail to "m". */
	le->m_last_mbuf = m;

	return (0);
}

int
tcp_lro_rx(struct lro_ctrl *lc, struct mbuf *m, uint32_t csum)
{
	int error;

	/* get current time */
	lc->lro_last_queue_time = getsbinuptime();

	CURVNET_SET(lc->ifp->if_vnet);
	error = tcp_lro_rx_common(lc, m, csum, true);
	CURVNET_RESTORE();

	return (error);
}

void
tcp_lro_queue_mbuf(struct lro_ctrl *lc, struct mbuf *mb)
{
	/* sanity checks */
	if (__predict_false(lc->ifp == NULL || lc->lro_mbuf_data == NULL ||
	    lc->lro_mbuf_max == 0)) {
		/* packet drop */
		m_freem(mb);
		return;
	}

	/* check if packet is not LRO capable */
	if (__predict_false(mb->m_pkthdr.csum_flags == 0 ||
	    (lc->ifp->if_capenable & IFCAP_LRO) == 0)) {
		/* input packet to network layer */
		(*lc->ifp->if_input) (lc->ifp, mb);
		return;
	}

	/* create sequence number */
	lc->lro_mbuf_data[lc->lro_mbuf_count].seq =
	    (((uint64_t)M_HASHTYPE_GET(mb)) << 56) |
	    (((uint64_t)mb->m_pkthdr.flowid) << 24) |
	    ((uint64_t)lc->lro_mbuf_count);

	/* enter mbuf */
	lc->lro_mbuf_data[lc->lro_mbuf_count].mb = mb;

	/* flush if array is full */
	if (__predict_false(++lc->lro_mbuf_count == lc->lro_mbuf_max))
		tcp_lro_flush_all(lc);
}

/* end */