/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright 2001 Niels Provos <provos@citi.umich.edu>
 * Copyright 2011-2018 Alexander Bluhm <bluhm@openbsd.org>
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 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.
 *
 *      $OpenBSD: pf_norm.c,v 1.114 2009/01/29 14:11:45 henning Exp $
 */

#include <sys/cdefs.h>
#include "opt_inet.h"
#include "opt_inet6.h"
#include "opt_pf.h"

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/mbuf.h>
#include <sys/mutex.h>
#include <sys/refcount.h>
#include <sys/socket.h>

#include <net/if.h>
#include <net/if_var.h>
#include <net/if_private.h>
#include <net/vnet.h>
#include <net/pfvar.h>
#include <net/if_pflog.h>

#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/ip_var.h>
#include <netinet6/in6_var.h>
#include <netinet6/nd6.h>
#include <netinet6/ip6_var.h>
#include <netinet6/scope6_var.h>
#include <netinet/tcp.h>
#include <netinet/tcp_fsm.h>
#include <netinet/tcp_seq.h>
#include <netinet/sctp_constants.h>
#include <netinet/sctp_header.h>

#ifdef INET6
#include <netinet/ip6.h>
#endif /* INET6 */

struct pf_frent {
        TAILQ_ENTRY(pf_frent)   fr_next;
        struct mbuf     *fe_m;
        uint16_t        fe_hdrlen;      /* ipv4 header length with ip options
                                           ipv6, extension, fragment header */
        uint16_t        fe_extoff;      /* last extension header offset or 0 */
        uint16_t        fe_len;         /* fragment length */
        uint16_t        fe_off;         /* fragment offset */
        uint16_t        fe_mff;         /* more fragment flag */
};

RB_HEAD(pf_frag_tree, pf_fragment);
struct pf_frnode {
        struct pf_addr          fn_src;         /* ip source address */
        struct pf_addr          fn_dst;         /* ip destination address */
        sa_family_t             fn_af;          /* address family */
        u_int8_t                fn_proto;       /* protocol for fragments in fn_tree */
        u_int32_t               fn_fragments;   /* number of entries in fn_tree */

        RB_ENTRY(pf_frnode)     fn_entry;
        struct pf_frag_tree     fn_tree;        /* matching fragments, lookup by id */
};

struct pf_fragment {
        uint32_t        fr_id;  /* fragment id for reassemble */

        /* pointers to queue element */
        struct pf_frent *fr_firstoff[PF_FRAG_ENTRY_POINTS];
        /* count entries between pointers */
        uint8_t fr_entries[PF_FRAG_ENTRY_POINTS];
        RB_ENTRY(pf_fragment) fr_entry;
        TAILQ_ENTRY(pf_fragment) frag_next;
        uint32_t        fr_timeout;
        TAILQ_HEAD(pf_fragq, pf_frent) fr_queue;
        uint16_t        fr_maxlen;      /* maximum length of single fragment */
        u_int16_t       fr_holes;       /* number of holes in the queue */
        struct pf_frnode *fr_node;      /* ip src/dst/proto/af for fragments */
};

VNET_DEFINE_STATIC(struct mtx, pf_frag_mtx);
#define V_pf_frag_mtx           VNET(pf_frag_mtx)
#define PF_FRAG_LOCK()          mtx_lock(&V_pf_frag_mtx)
#define PF_FRAG_UNLOCK()        mtx_unlock(&V_pf_frag_mtx)
#define PF_FRAG_ASSERT()        mtx_assert(&V_pf_frag_mtx, MA_OWNED)

VNET_DEFINE(uma_zone_t, pf_state_scrub_z);      /* XXX: shared with pfsync */

VNET_DEFINE_STATIC(uma_zone_t, pf_frent_z);
#define V_pf_frent_z    VNET(pf_frent_z)
VNET_DEFINE_STATIC(uma_zone_t, pf_frnode_z);
#define V_pf_frnode_z   VNET(pf_frnode_z)
VNET_DEFINE_STATIC(uma_zone_t, pf_frag_z);
#define V_pf_frag_z     VNET(pf_frag_z)
VNET_DEFINE(uma_zone_t, pf_anchor_z);
VNET_DEFINE(uma_zone_t, pf_eth_anchor_z);

TAILQ_HEAD(pf_fragqueue, pf_fragment);
TAILQ_HEAD(pf_cachequeue, pf_fragment);
RB_HEAD(pf_frnode_tree, pf_frnode);
VNET_DEFINE_STATIC(struct pf_fragqueue, pf_fragqueue);
#define V_pf_fragqueue                  VNET(pf_fragqueue)
static __inline int     pf_frnode_compare(struct pf_frnode *,
                            struct pf_frnode *);
VNET_DEFINE_STATIC(struct pf_frnode_tree, pf_frnode_tree);
#define V_pf_frnode_tree                VNET(pf_frnode_tree)
RB_PROTOTYPE(pf_frnode_tree, pf_frnode, fn_entry, pf_frnode_compare);
RB_GENERATE(pf_frnode_tree, pf_frnode, fn_entry, pf_frnode_compare);

static int               pf_frag_compare(struct pf_fragment *,
                            struct pf_fragment *);
static RB_PROTOTYPE(pf_frag_tree, pf_fragment, fr_entry, pf_frag_compare);
static RB_GENERATE(pf_frag_tree, pf_fragment, fr_entry, pf_frag_compare);

static void     pf_flush_fragments(void);
static void     pf_free_fragment(struct pf_fragment *);

static struct pf_frent *pf_create_fragment(u_short *);
static int      pf_frent_holes(struct pf_frent *frent);
static struct pf_fragment       *pf_find_fragment(struct pf_frnode *, u_int32_t);
static inline int       pf_frent_index(struct pf_frent *);
static int      pf_frent_insert(struct pf_fragment *,
                            struct pf_frent *, struct pf_frent *);
void                    pf_frent_remove(struct pf_fragment *,
                            struct pf_frent *);
struct pf_frent         *pf_frent_previous(struct pf_fragment *,
                            struct pf_frent *);
static struct pf_fragment *pf_fillup_fragment(struct pf_frnode *, u_int32_t,
                    struct pf_frent *, u_short *);
static struct mbuf *pf_join_fragment(struct pf_fragment *);
#ifdef INET
static int      pf_reassemble(struct mbuf **, u_short *);
#endif  /* INET */
#ifdef INET6
static int      pf_reassemble6(struct mbuf **,
                    struct ip6_frag *, uint16_t, uint16_t, u_short *);
#endif  /* INET6 */

#ifdef INET
static void
pf_ip2key(struct ip *ip, struct pf_frnode *key)
{

        key->fn_src.v4 = ip->ip_src;
        key->fn_dst.v4 = ip->ip_dst;
        key->fn_af = AF_INET;
        key->fn_proto = ip->ip_p;
}
#endif  /* INET */

void
pf_normalize_init(void)
{

        V_pf_frag_z = uma_zcreate("pf frags", sizeof(struct pf_fragment),
            NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
        V_pf_frnode_z = uma_zcreate("pf fragment node",
            sizeof(struct pf_frnode), NULL, NULL, NULL, NULL,
            UMA_ALIGN_PTR, 0);
        V_pf_frent_z = uma_zcreate("pf frag entries", sizeof(struct pf_frent),
            NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
        V_pf_state_scrub_z = uma_zcreate("pf state scrubs",
            sizeof(struct pf_state_scrub),  NULL, NULL, NULL, NULL,
            UMA_ALIGN_PTR, 0);

        mtx_init(&V_pf_frag_mtx, "pf fragments", NULL, MTX_DEF);

        V_pf_limits[PF_LIMIT_FRAGS].zone = V_pf_frent_z;
        V_pf_limits[PF_LIMIT_FRAGS].limit = PFFRAG_FRENT_HIWAT;
        uma_zone_set_max(V_pf_frent_z, PFFRAG_FRENT_HIWAT);
        uma_zone_set_warning(V_pf_frent_z, "PF frag entries limit reached");

        TAILQ_INIT(&V_pf_fragqueue);
}

void
pf_normalize_cleanup(void)
{

        uma_zdestroy(V_pf_state_scrub_z);
        uma_zdestroy(V_pf_frent_z);
        uma_zdestroy(V_pf_frnode_z);
        uma_zdestroy(V_pf_frag_z);

        mtx_destroy(&V_pf_frag_mtx);
}

uint64_t
pf_normalize_get_frag_count(void)
{
        return (uma_zone_get_cur(V_pf_frent_z));
}

static int
pf_frnode_compare(struct pf_frnode *a, struct pf_frnode *b)
{
        int     diff;

        if ((diff = a->fn_proto - b->fn_proto) != 0)
                return (diff);
        if ((diff = a->fn_af - b->fn_af) != 0)
                return (diff);
        if ((diff = pf_addr_cmp(&a->fn_src, &b->fn_src, a->fn_af)) != 0)
                return (diff);
        if ((diff = pf_addr_cmp(&a->fn_dst, &b->fn_dst, a->fn_af)) != 0)
                return (diff);
        return (0);
}

static __inline int
pf_frag_compare(struct pf_fragment *a, struct pf_fragment *b)
{
        int     diff;

        if ((diff = a->fr_id - b->fr_id) != 0)
                return (diff);

        return (0);
}

void
pf_purge_expired_fragments(void)
{
        u_int32_t       expire = time_uptime -
                            V_pf_default_rule.timeout[PFTM_FRAG];

        pf_purge_fragments(expire);
}

void
pf_purge_fragments(uint32_t expire)
{
        struct pf_fragment      *frag;

        PF_FRAG_LOCK();
        while ((frag = TAILQ_LAST(&V_pf_fragqueue, pf_fragqueue)) != NULL) {
                if (frag->fr_timeout > expire)
                        break;

                DPFPRINTF(PF_DEBUG_MISC, "expiring %d(%p)",
                    frag->fr_id, frag);
                pf_free_fragment(frag);
        }

        PF_FRAG_UNLOCK();
}

/*
 * Try to flush old fragments to make space for new ones
 */
static void
pf_flush_fragments(void)
{
        struct pf_fragment      *frag;
        int                      goal;

        PF_FRAG_ASSERT();

        goal = uma_zone_get_cur(V_pf_frent_z) * 9 / 10;
        DPFPRINTF(PF_DEBUG_MISC, "trying to free %d frag entriess", goal);
        while (goal < uma_zone_get_cur(V_pf_frent_z)) {
                frag = TAILQ_LAST(&V_pf_fragqueue, pf_fragqueue);
                if (frag)
                        pf_free_fragment(frag);
                else
                        break;
        }
}

/*
 * Remove a fragment from the fragment queue, free its fragment entries,
 * and free the fragment itself.
 */
static void
pf_free_fragment(struct pf_fragment *frag)
{
        struct pf_frent         *frent;
        struct pf_frnode        *frnode;

        PF_FRAG_ASSERT();

        frnode = frag->fr_node;
        RB_REMOVE(pf_frag_tree, &frnode->fn_tree, frag);
        MPASS(frnode->fn_fragments >= 1);
        frnode->fn_fragments--;
        if (frnode->fn_fragments == 0) {
                MPASS(RB_EMPTY(&frnode->fn_tree));
                RB_REMOVE(pf_frnode_tree, &V_pf_frnode_tree, frnode);
                uma_zfree(V_pf_frnode_z, frnode);
        }

        TAILQ_REMOVE(&V_pf_fragqueue, frag, frag_next);

        /* Free all fragment entries */
        while ((frent = TAILQ_FIRST(&frag->fr_queue)) != NULL) {
                TAILQ_REMOVE(&frag->fr_queue, frent, fr_next);
                counter_u64_add(V_pf_status.ncounters[NCNT_FRAG_REMOVALS], 1);

                m_freem(frent->fe_m);
                uma_zfree(V_pf_frent_z, frent);
        }

        uma_zfree(V_pf_frag_z, frag);
}

static struct pf_fragment *
pf_find_fragment(struct pf_frnode *key, uint32_t id)
{
        struct pf_fragment      *frag, idkey;
        struct pf_frnode        *frnode;

        PF_FRAG_ASSERT();

        frnode = RB_FIND(pf_frnode_tree, &V_pf_frnode_tree, key);
        counter_u64_add(V_pf_status.ncounters[NCNT_FRAG_SEARCH], 1);
        if (frnode == NULL)
                return (NULL);
        MPASS(frnode->fn_fragments >= 1);
        idkey.fr_id = id;
        frag = RB_FIND(pf_frag_tree, &frnode->fn_tree, &idkey);
        if (frag == NULL)
                return (NULL);
        TAILQ_REMOVE(&V_pf_fragqueue, frag, frag_next);
        TAILQ_INSERT_HEAD(&V_pf_fragqueue, frag, frag_next);

        return (frag);
}

static struct pf_frent *
pf_create_fragment(u_short *reason)
{
        struct pf_frent *frent;

        PF_FRAG_ASSERT();

        frent = uma_zalloc(V_pf_frent_z, M_NOWAIT);
        if (frent == NULL) {
                pf_flush_fragments();
                frent = uma_zalloc(V_pf_frent_z, M_NOWAIT);
                if (frent == NULL) {
                        REASON_SET(reason, PFRES_MEMORY);
                        return (NULL);
                }
        }

        return (frent);
}

/*
 * Calculate the additional holes that were created in the fragment
 * queue by inserting this fragment.  A fragment in the middle
 * creates one more hole by splitting.  For each connected side,
 * it loses one hole.
 * Fragment entry must be in the queue when calling this function.
 */
static int
pf_frent_holes(struct pf_frent *frent)
{
        struct pf_frent *prev = TAILQ_PREV(frent, pf_fragq, fr_next);
        struct pf_frent *next = TAILQ_NEXT(frent, fr_next);
        int holes = 1;

        if (prev == NULL) {
                if (frent->fe_off == 0)
                        holes--;
        } else {
                KASSERT(frent->fe_off != 0, ("frent->fe_off != 0"));
                if (frent->fe_off == prev->fe_off + prev->fe_len)
                        holes--;
        }
        if (next == NULL) {
                if (!frent->fe_mff)
                        holes--;
        } else {
                KASSERT(frent->fe_mff, ("frent->fe_mff"));
                if (next->fe_off == frent->fe_off + frent->fe_len)
                        holes--;
        }
        return holes;
}

static inline int
pf_frent_index(struct pf_frent *frent)
{
        /*
         * We have an array of 16 entry points to the queue.  A full size
         * 65535 octet IP packet can have 8192 fragments.  So the queue
         * traversal length is at most 512 and at most 16 entry points are
         * checked.  We need 128 additional bytes on a 64 bit architecture.
         */
        CTASSERT(((u_int16_t)0xffff &~ 7) / (0x10000 / PF_FRAG_ENTRY_POINTS) ==
            16 - 1);
        CTASSERT(((u_int16_t)0xffff >> 3) / PF_FRAG_ENTRY_POINTS == 512 - 1);

        return frent->fe_off / (0x10000 / PF_FRAG_ENTRY_POINTS);
}

static int
pf_frent_insert(struct pf_fragment *frag, struct pf_frent *frent,
    struct pf_frent *prev)
{
        int index;

        CTASSERT(PF_FRAG_ENTRY_LIMIT <= 0xff);

        /*
         * A packet has at most 65536 octets.  With 16 entry points, each one
         * spawns 4096 octets.  We limit these to 64 fragments each, which
         * means on average every fragment must have at least 64 octets.
         */
        index = pf_frent_index(frent);
        if (frag->fr_entries[index] >= PF_FRAG_ENTRY_LIMIT)
                return ENOBUFS;
        frag->fr_entries[index]++;

        if (prev == NULL) {
                TAILQ_INSERT_HEAD(&frag->fr_queue, frent, fr_next);
        } else {
                KASSERT(prev->fe_off + prev->fe_len <= frent->fe_off,
                    ("overlapping fragment"));
                TAILQ_INSERT_AFTER(&frag->fr_queue, prev, frent, fr_next);
        }
        counter_u64_add(V_pf_status.ncounters[NCNT_FRAG_INSERT], 1);

        if (frag->fr_firstoff[index] == NULL) {
                KASSERT(prev == NULL || pf_frent_index(prev) < index,
                    ("prev == NULL || pf_frent_index(pref) < index"));
                frag->fr_firstoff[index] = frent;
        } else {
                if (frent->fe_off < frag->fr_firstoff[index]->fe_off) {
                        KASSERT(prev == NULL || pf_frent_index(prev) < index,
                            ("prev == NULL || pf_frent_index(pref) < index"));
                        frag->fr_firstoff[index] = frent;
                } else {
                        KASSERT(prev != NULL, ("prev != NULL"));
                        KASSERT(pf_frent_index(prev) == index,
                            ("pf_frent_index(prev) == index"));
                }
        }

        frag->fr_holes += pf_frent_holes(frent);

        return 0;
}

void
pf_frent_remove(struct pf_fragment *frag, struct pf_frent *frent)
{
#ifdef INVARIANTS
        struct pf_frent *prev = TAILQ_PREV(frent, pf_fragq, fr_next);
#endif /* INVARIANTS */
        struct pf_frent *next = TAILQ_NEXT(frent, fr_next);
        int index;

        frag->fr_holes -= pf_frent_holes(frent);

        index = pf_frent_index(frent);
        KASSERT(frag->fr_firstoff[index] != NULL, ("frent not found"));
        if (frag->fr_firstoff[index]->fe_off == frent->fe_off) {
                if (next == NULL) {
                        frag->fr_firstoff[index] = NULL;
                } else {
                        KASSERT(frent->fe_off + frent->fe_len <= next->fe_off,
                            ("overlapping fragment"));
                        if (pf_frent_index(next) == index) {
                                frag->fr_firstoff[index] = next;
                        } else {
                                frag->fr_firstoff[index] = NULL;
                        }
                }
        } else {
                KASSERT(frag->fr_firstoff[index]->fe_off < frent->fe_off,
                    ("frag->fr_firstoff[index]->fe_off < frent->fe_off"));
                KASSERT(prev != NULL, ("prev != NULL"));
                KASSERT(prev->fe_off + prev->fe_len <= frent->fe_off,
                    ("overlapping fragment"));
                KASSERT(pf_frent_index(prev) == index,
                    ("pf_frent_index(prev) == index"));
        }

        TAILQ_REMOVE(&frag->fr_queue, frent, fr_next);
        counter_u64_add(V_pf_status.ncounters[NCNT_FRAG_REMOVALS], 1);

        KASSERT(frag->fr_entries[index] > 0, ("No fragments remaining"));
        frag->fr_entries[index]--;
}

struct pf_frent *
pf_frent_previous(struct pf_fragment *frag, struct pf_frent *frent)
{
        struct pf_frent *prev, *next;
        int index;

        /*
         * If there are no fragments after frag, take the final one.  Assume
         * that the global queue is not empty.
         */
        prev = TAILQ_LAST(&frag->fr_queue, pf_fragq);
        KASSERT(prev != NULL, ("prev != NULL"));
        if (prev->fe_off <= frent->fe_off)
                return prev;
        /*
         * We want to find a fragment entry that is before frag, but still
         * close to it.  Find the first fragment entry that is in the same
         * entry point or in the first entry point after that.  As we have
         * already checked that there are entries behind frag, this will
         * succeed.
         */
        for (index = pf_frent_index(frent); index < PF_FRAG_ENTRY_POINTS;
            index++) {
                prev = frag->fr_firstoff[index];
                if (prev != NULL)
                        break;
        }
        KASSERT(prev != NULL, ("prev != NULL"));
        /*
         * In prev we may have a fragment from the same entry point that is
         * before frent, or one that is just one position behind frent.
         * In the latter case, we go back one step and have the predecessor.
         * There may be none if the new fragment will be the first one.
         */
        if (prev->fe_off > frent->fe_off) {
                prev = TAILQ_PREV(prev, pf_fragq, fr_next);
                if (prev == NULL)
                        return NULL;
                KASSERT(prev->fe_off <= frent->fe_off,
                    ("prev->fe_off <= frent->fe_off"));
                return prev;
        }
        /*
         * In prev is the first fragment of the entry point.  The offset
         * of frag is behind it.  Find the closest previous fragment.
         */
        for (next = TAILQ_NEXT(prev, fr_next); next != NULL;
            next = TAILQ_NEXT(next, fr_next)) {
                if (next->fe_off > frent->fe_off)
                        break;
                prev = next;
        }
        return prev;
}

static struct pf_fragment *
pf_fillup_fragment(struct pf_frnode *key, uint32_t id,
    struct pf_frent *frent, u_short *reason)
{
        struct pf_frent         *after, *next, *prev;
        struct pf_fragment      *frag;
        struct pf_frnode        *frnode;
        uint16_t                total;

        PF_FRAG_ASSERT();

        /* No empty fragments. */
        if (frent->fe_len == 0) {
                DPFPRINTF(PF_DEBUG_MISC, "bad fragment: len 0");
                goto bad_fragment;
        }

        /* All fragments are 8 byte aligned. */
        if (frent->fe_mff && (frent->fe_len & 0x7)) {
                DPFPRINTF(PF_DEBUG_MISC, "bad fragment: mff and len %d",
                    frent->fe_len);
                goto bad_fragment;
        }

        /* Respect maximum length, IP_MAXPACKET == IPV6_MAXPACKET. */
        if (frent->fe_off + frent->fe_len > IP_MAXPACKET) {
                DPFPRINTF(PF_DEBUG_MISC, "bad fragment: max packet %d",
                    frent->fe_off + frent->fe_len);
                goto bad_fragment;
        }

        if (key->fn_af == AF_INET)
                DPFPRINTF(PF_DEBUG_MISC, "reass frag %d @ %d-%d\n",
                    id, frent->fe_off, frent->fe_off + frent->fe_len);
        else 
                DPFPRINTF(PF_DEBUG_MISC, "reass frag %#08x @ %d-%d",
                    id, frent->fe_off, frent->fe_off + frent->fe_len);

        /* Fully buffer all of the fragments in this fragment queue. */
        frag = pf_find_fragment(key, id);

        /* Create a new reassembly queue for this packet. */
        if (frag == NULL) {
                frag = uma_zalloc(V_pf_frag_z, M_NOWAIT);
                if (frag == NULL) {
                        pf_flush_fragments();
                        frag = uma_zalloc(V_pf_frag_z, M_NOWAIT);
                        if (frag == NULL) {
                                REASON_SET(reason, PFRES_MEMORY);
                                goto drop_fragment;
                        }
                }

                frnode = RB_FIND(pf_frnode_tree, &V_pf_frnode_tree, key);
                if (frnode == NULL) {
                        frnode = uma_zalloc(V_pf_frnode_z, M_NOWAIT);
                        if (frnode == NULL) {
                                pf_flush_fragments();
                                frnode = uma_zalloc(V_pf_frnode_z, M_NOWAIT);
                                if (frnode == NULL) {
                                        REASON_SET(reason, PFRES_MEMORY);
                                        uma_zfree(V_pf_frag_z, frag);
                                        goto drop_fragment;
                                }
                        }
                        *frnode = *key;
                        RB_INIT(&frnode->fn_tree);
                        frnode->fn_fragments = 0;
                }
                memset(frag->fr_firstoff, 0, sizeof(frag->fr_firstoff));
                memset(frag->fr_entries, 0, sizeof(frag->fr_entries));
                frag->fr_timeout = time_uptime;
                TAILQ_INIT(&frag->fr_queue);
                frag->fr_maxlen = frent->fe_len;
                frag->fr_holes = 1;

                frag->fr_id = id;
                frag->fr_node = frnode;
                /* RB_INSERT cannot fail as pf_find_fragment() found nothing */
                RB_INSERT(pf_frag_tree, &frnode->fn_tree, frag);
                frnode->fn_fragments++;
                if (frnode->fn_fragments == 1)
                        RB_INSERT(pf_frnode_tree, &V_pf_frnode_tree, frnode);

                TAILQ_INSERT_HEAD(&V_pf_fragqueue, frag, frag_next);

                /* We do not have a previous fragment, cannot fail. */
                pf_frent_insert(frag, frent, NULL);

                return (frag);
        }

        KASSERT(!TAILQ_EMPTY(&frag->fr_queue), ("!TAILQ_EMPTY()->fr_queue"));
        MPASS(frag->fr_node);

        /* Remember maximum fragment len for refragmentation. */
        if (frent->fe_len > frag->fr_maxlen)
                frag->fr_maxlen = frent->fe_len;

        /* Maximum data we have seen already. */
        total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off +
                TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len;

        /* Non terminal fragments must have more fragments flag. */
        if (frent->fe_off + frent->fe_len < total && !frent->fe_mff)
                goto free_ipv6_fragment;

        /* Check if we saw the last fragment already. */
        if (!TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_mff) {
                if (frent->fe_off + frent->fe_len > total ||
                    (frent->fe_off + frent->fe_len == total && frent->fe_mff))
                        goto free_ipv6_fragment;
        } else {
                if (frent->fe_off + frent->fe_len == total && !frent->fe_mff)
                        goto free_ipv6_fragment;
        }

        /* Find neighbors for newly inserted fragment */
        prev = pf_frent_previous(frag, frent);
        if (prev == NULL) {
                after = TAILQ_FIRST(&frag->fr_queue);
                KASSERT(after != NULL, ("after != NULL"));
        } else {
                after = TAILQ_NEXT(prev, fr_next);
        }

        if (prev != NULL && prev->fe_off + prev->fe_len > frent->fe_off) {
                uint16_t precut;

                if (frag->fr_node->fn_af == AF_INET6)
                        goto free_fragment;

                precut = prev->fe_off + prev->fe_len - frent->fe_off;
                if (precut >= frent->fe_len) {
                        DPFPRINTF(PF_DEBUG_MISC, "new frag overlapped");
                        goto drop_fragment;
                }
                DPFPRINTF(PF_DEBUG_MISC, "frag head overlap %d", precut);
                m_adj(frent->fe_m, precut);
                frent->fe_off += precut;
                frent->fe_len -= precut;
        }

        for (; after != NULL && frent->fe_off + frent->fe_len > after->fe_off;
            after = next) {
                uint16_t aftercut;

                aftercut = frent->fe_off + frent->fe_len - after->fe_off;
                if (aftercut < after->fe_len) {
                        DPFPRINTF(PF_DEBUG_MISC, "frag tail overlap %d",
                            aftercut);
                        m_adj(after->fe_m, aftercut);
                        /* Fragment may switch queue as fe_off changes */
                        pf_frent_remove(frag, after);
                        after->fe_off += aftercut;
                        after->fe_len -= aftercut;
                        /* Insert into correct queue */
                        if (pf_frent_insert(frag, after, prev)) {
                                DPFPRINTF(PF_DEBUG_MISC,
                                    "fragment requeue limit exceeded");
                                m_freem(after->fe_m);
                                uma_zfree(V_pf_frent_z, after);
                                /* There is not way to recover */
                                goto free_fragment;
                        }
                        break;
                }

                /* This fragment is completely overlapped, lose it. */
                DPFPRINTF(PF_DEBUG_MISC, "old frag overlapped");
                next = TAILQ_NEXT(after, fr_next);
                pf_frent_remove(frag, after);
                m_freem(after->fe_m);
                uma_zfree(V_pf_frent_z, after);
        }

        /* If part of the queue gets too long, there is not way to recover. */
        if (pf_frent_insert(frag, frent, prev)) {
                DPFPRINTF(PF_DEBUG_MISC, "fragment queue limit exceeded");
                goto bad_fragment;
        }

        return (frag);

free_ipv6_fragment:
        if (frag->fr_node->fn_af == AF_INET)
                goto bad_fragment;
free_fragment:
        /*
         * RFC 5722, Errata 3089:  When reassembling an IPv6 datagram, if one
         * or more its constituent fragments is determined to be an overlapping
         * fragment, the entire datagram (and any constituent fragments) MUST
         * be silently discarded.
         */
        DPFPRINTF(PF_DEBUG_MISC, "flush overlapping fragments");
        pf_free_fragment(frag);

bad_fragment:
        REASON_SET(reason, PFRES_FRAG);
drop_fragment:
        uma_zfree(V_pf_frent_z, frent);
        return (NULL);
}

static struct mbuf *
pf_join_fragment(struct pf_fragment *frag)
{
        struct mbuf *m, *m2;
        struct pf_frent *frent;

        frent = TAILQ_FIRST(&frag->fr_queue);
        TAILQ_REMOVE(&frag->fr_queue, frent, fr_next);
        counter_u64_add(V_pf_status.ncounters[NCNT_FRAG_REMOVALS], 1);

        m = frent->fe_m;
        if ((frent->fe_hdrlen + frent->fe_len) < m->m_pkthdr.len)
                m_adj(m, (frent->fe_hdrlen + frent->fe_len) - m->m_pkthdr.len);
        uma_zfree(V_pf_frent_z, frent);
        while ((frent = TAILQ_FIRST(&frag->fr_queue)) != NULL) {
                TAILQ_REMOVE(&frag->fr_queue, frent, fr_next);
                counter_u64_add(V_pf_status.ncounters[NCNT_FRAG_REMOVALS], 1);

                m2 = frent->fe_m;
                /* Strip off ip header. */
                m_adj(m2, frent->fe_hdrlen);
                /* Strip off any trailing bytes. */
                if (frent->fe_len < m2->m_pkthdr.len)
                        m_adj(m2, frent->fe_len - m2->m_pkthdr.len);

                uma_zfree(V_pf_frent_z, frent);
                m_cat(m, m2);
        }

        /* Remove from fragment queue. */
        pf_free_fragment(frag);

        return (m);
}

#ifdef INET
static int
pf_reassemble(struct mbuf **m0, u_short *reason)
{
        struct mbuf             *m = *m0;
        struct ip               *ip = mtod(m, struct ip *);
        struct pf_frent         *frent;
        struct pf_fragment      *frag;
        struct m_tag            *mtag;
        struct pf_fragment_tag  *ftag;
        struct pf_frnode         key;
        uint16_t                 total, hdrlen;
        uint32_t                 frag_id;
        uint16_t                 maxlen;

        /* Get an entry for the fragment queue */
        if ((frent = pf_create_fragment(reason)) == NULL)
                return (PF_DROP);

        frent->fe_m = m;
        frent->fe_hdrlen = ip->ip_hl << 2;
        frent->fe_extoff = 0;
        frent->fe_len = ntohs(ip->ip_len) - (ip->ip_hl << 2);
        frent->fe_off = (ntohs(ip->ip_off) & IP_OFFMASK) << 3;
        frent->fe_mff = ntohs(ip->ip_off) & IP_MF;

        pf_ip2key(ip, &key);

        if ((frag = pf_fillup_fragment(&key, ip->ip_id, frent, reason)) == NULL)
                return (PF_DROP);

        /* The mbuf is part of the fragment entry, no direct free or access */
        m = *m0 = NULL;

        if (frag->fr_holes) {
                DPFPRINTF(PF_DEBUG_MISC, "frag %d, holes %d",
                    frag->fr_id, frag->fr_holes);
                return (PF_PASS);  /* drop because *m0 is NULL, no error */
        }

        /* We have all the data */
        frent = TAILQ_FIRST(&frag->fr_queue);
        KASSERT(frent != NULL, ("frent != NULL"));
        total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off +
                TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len;
        hdrlen = frent->fe_hdrlen;

        maxlen = frag->fr_maxlen;
        frag_id = frag->fr_id;
        m = *m0 = pf_join_fragment(frag);
        frag = NULL;

        if (m->m_flags & M_PKTHDR) {
                int plen = 0;
                for (m = *m0; m; m = m->m_next)
                        plen += m->m_len;
                m = *m0;
                m->m_pkthdr.len = plen;
        }

        if ((mtag = m_tag_get(PACKET_TAG_PF_REASSEMBLED,
            sizeof(struct pf_fragment_tag), M_NOWAIT)) == NULL) {
                REASON_SET(reason, PFRES_SHORT);
                /* PF_DROP requires a valid mbuf *m0 in pf_test() */
                return (PF_DROP);
        }
        ftag = (struct pf_fragment_tag *)(mtag + 1);
        ftag->ft_hdrlen = hdrlen;
        ftag->ft_extoff = 0;
        ftag->ft_maxlen = maxlen;
        ftag->ft_id = frag_id;
        m_tag_prepend(m, mtag);

        ip = mtod(m, struct ip *);
        ip->ip_sum = pf_cksum_fixup(ip->ip_sum, ip->ip_len,
            htons(hdrlen + total), 0);
        ip->ip_len = htons(hdrlen + total);
        ip->ip_sum = pf_cksum_fixup(ip->ip_sum, ip->ip_off,
            ip->ip_off & ~(IP_MF|IP_OFFMASK), 0);
        ip->ip_off &= ~(IP_MF|IP_OFFMASK);

        if (hdrlen + total > IP_MAXPACKET) {
                DPFPRINTF(PF_DEBUG_MISC, "drop: too big: %d", total);
                ip->ip_len = 0;
                REASON_SET(reason, PFRES_SHORT);
                /* PF_DROP requires a valid mbuf *m0 in pf_test() */
                return (PF_DROP);
        }

        DPFPRINTF(PF_DEBUG_MISC, "complete: %p(%d)", m, ntohs(ip->ip_len));
        return (PF_PASS);
}
#endif  /* INET */

#ifdef INET6
static int
pf_reassemble6(struct mbuf **m0, struct ip6_frag *fraghdr,
    uint16_t hdrlen, uint16_t extoff, u_short *reason)
{
        struct mbuf             *m = *m0;
        struct ip6_hdr          *ip6 = mtod(m, struct ip6_hdr *);
        struct pf_frent         *frent;
        struct pf_fragment      *frag;
        struct pf_frnode         key;
        struct m_tag            *mtag;
        struct pf_fragment_tag  *ftag;
        int                      off;
        uint32_t                 frag_id;
        uint16_t                 total, maxlen;
        uint8_t                  proto;

        PF_FRAG_LOCK();

        /* Get an entry for the fragment queue. */
        if ((frent = pf_create_fragment(reason)) == NULL) {
                PF_FRAG_UNLOCK();
                return (PF_DROP);
        }

        frent->fe_m = m;
        frent->fe_hdrlen = hdrlen;
        frent->fe_extoff = extoff;
        frent->fe_len = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen) - hdrlen;
        frent->fe_off = ntohs(fraghdr->ip6f_offlg & IP6F_OFF_MASK);
        frent->fe_mff = fraghdr->ip6f_offlg & IP6F_MORE_FRAG;

        key.fn_src.v6 = ip6->ip6_src;
        key.fn_dst.v6 = ip6->ip6_dst;
        key.fn_af = AF_INET6;
        /* Only the first fragment's protocol is relevant. */
        key.fn_proto = 0;

        if ((frag = pf_fillup_fragment(&key, fraghdr->ip6f_ident, frent, reason)) == NULL) {
                PF_FRAG_UNLOCK();
                return (PF_DROP);
        }

        /* The mbuf is part of the fragment entry, no direct free or access. */
        m = *m0 = NULL;

        if (frag->fr_holes) {
                DPFPRINTF(PF_DEBUG_MISC, "frag %d, holes %d", frag->fr_id,
                    frag->fr_holes);
                PF_FRAG_UNLOCK();
                return (PF_PASS);  /* Drop because *m0 is NULL, no error. */
        }

        /* We have all the data. */
        frent = TAILQ_FIRST(&frag->fr_queue);
        KASSERT(frent != NULL, ("frent != NULL"));
        extoff = frent->fe_extoff;
        maxlen = frag->fr_maxlen;
        frag_id = frag->fr_id;
        total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off +
                TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len;
        hdrlen = frent->fe_hdrlen - sizeof(struct ip6_frag);

        m = *m0 = pf_join_fragment(frag);
        frag = NULL;

        PF_FRAG_UNLOCK();

        /* Take protocol from first fragment header. */
        m = m_getptr(m, hdrlen + offsetof(struct ip6_frag, ip6f_nxt), &off);
        KASSERT(m, ("%s: short mbuf chain", __func__));
        proto = *(mtod(m, uint8_t *) + off);
        m = *m0;

        /* Delete frag6 header */
        if (ip6_deletefraghdr(m, hdrlen, M_NOWAIT) != 0)
                goto fail;

        if (m->m_flags & M_PKTHDR) {
                int plen = 0;
                for (m = *m0; m; m = m->m_next)
                        plen += m->m_len;
                m = *m0;
                m->m_pkthdr.len = plen;
        }

        if ((mtag = m_tag_get(PACKET_TAG_PF_REASSEMBLED,
            sizeof(struct pf_fragment_tag), M_NOWAIT)) == NULL)
                goto fail;
        ftag = (struct pf_fragment_tag *)(mtag + 1);
        ftag->ft_hdrlen = hdrlen;
        ftag->ft_extoff = extoff;
        ftag->ft_maxlen = maxlen;
        ftag->ft_id = frag_id;
        m_tag_prepend(m, mtag);

        ip6 = mtod(m, struct ip6_hdr *);
        ip6->ip6_plen = htons(hdrlen - sizeof(struct ip6_hdr) + total);
        if (extoff) {
                /* Write protocol into next field of last extension header. */
                m = m_getptr(m, extoff + offsetof(struct ip6_ext, ip6e_nxt),
                    &off);
                KASSERT(m, ("%s: short mbuf chain", __func__));
                *(mtod(m, char *) + off) = proto;
                m = *m0;
        } else
                ip6->ip6_nxt = proto;

        if (hdrlen - sizeof(struct ip6_hdr) + total > IPV6_MAXPACKET) {
                DPFPRINTF(PF_DEBUG_MISC, "drop: too big: %d", total);
                ip6->ip6_plen = 0;
                REASON_SET(reason, PFRES_SHORT);
                /* PF_DROP requires a valid mbuf *m0 in pf_test6(). */
                return (PF_DROP);
        }

        DPFPRINTF(PF_DEBUG_MISC, "complete: %p(%d)", m,
            ntohs(ip6->ip6_plen));
        return (PF_PASS);

fail:
        REASON_SET(reason, PFRES_MEMORY);
        /* PF_DROP requires a valid mbuf *m0 in pf_test6(), will free later. */
        return (PF_DROP);
}
#endif  /* INET6 */

#ifdef INET6
int
pf_max_frag_size(struct mbuf *m)
{
        struct m_tag *tag;
        struct pf_fragment_tag *ftag;

        tag = m_tag_find(m, PACKET_TAG_PF_REASSEMBLED, NULL);
        if (tag == NULL)
                return (m->m_pkthdr.len);

        ftag = (struct pf_fragment_tag *)(tag + 1);

        return (ftag->ft_maxlen);
}

int
pf_refragment6(struct ifnet *ifp, struct mbuf **m0, struct m_tag *mtag,
    struct ifnet *rt, bool forward)
{
        struct mbuf             *m = *m0, *t;
        struct ip6_hdr          *hdr;
        struct pf_fragment_tag  *ftag = (struct pf_fragment_tag *)(mtag + 1);
        struct pf_pdesc          pd;
        uint32_t                 frag_id;
        uint16_t                 hdrlen, extoff, maxlen;
        uint8_t                  proto;
        int                      error, action;

        hdrlen = ftag->ft_hdrlen;
        extoff = ftag->ft_extoff;
        maxlen = ftag->ft_maxlen;
        frag_id = ftag->ft_id;
        m_tag_delete(m, mtag);
        mtag = NULL;
        ftag = NULL;

        if (extoff) {
                int off;

                /* Use protocol from next field of last extension header */
                m = m_getptr(m, extoff + offsetof(struct ip6_ext, ip6e_nxt),
                    &off);
                KASSERT((m != NULL), ("pf_refragment6: short mbuf chain"));
                proto = *(mtod(m, uint8_t *) + off);
                *(mtod(m, char *) + off) = IPPROTO_FRAGMENT;
                m = *m0;
        } else {
                hdr = mtod(m, struct ip6_hdr *);
                proto = hdr->ip6_nxt;
                hdr->ip6_nxt = IPPROTO_FRAGMENT;
        }

        /* In case of link-local traffic we'll need a scope set. */
        hdr = mtod(m, struct ip6_hdr *);

        in6_setscope(&hdr->ip6_src, ifp, NULL);
        in6_setscope(&hdr->ip6_dst, ifp, NULL);

        /* The MTU must be a multiple of 8 bytes, or we risk doing the
         * fragmentation wrong. */
        maxlen = maxlen & ~7;

        /*
         * Maxlen may be less than 8 if there was only a single
         * fragment.  As it was fragmented before, add a fragment
         * header also for a single fragment.  If total or maxlen
         * is less than 8, ip6_fragment() will return EMSGSIZE and
         * we drop the packet.
         */
        error = ip6_fragment(ifp, m, hdrlen, proto, maxlen, frag_id);
        m = (*m0)->m_nextpkt;
        (*m0)->m_nextpkt = NULL;
        if (error == 0) {
                /* The first mbuf contains the unfragmented packet. */
                m_freem(*m0);
                *m0 = NULL;
                action = PF_PASS;
        } else {
                /* Drop expects an mbuf to free. */
                DPFPRINTF(PF_DEBUG_MISC, "refragment error %d", error);
                action = PF_DROP;
        }
        for (; m; m = t) {
                t = m->m_nextpkt;
                m->m_nextpkt = NULL;
                m->m_flags |= M_SKIP_FIREWALL;
                memset(&pd, 0, sizeof(pd));
                pd.pf_mtag = pf_find_mtag(m);
                if (error != 0) {
                        m_freem(m);
                        continue;
                }
                if (rt != NULL) {
                        struct sockaddr_in6     dst;
                        hdr = mtod(m, struct ip6_hdr *);

                        bzero(&dst, sizeof(dst));
                        dst.sin6_family = AF_INET6;
                        dst.sin6_len = sizeof(dst);
                        dst.sin6_addr = hdr->ip6_dst;

                        if (m->m_pkthdr.len <= if_getmtu(ifp)) {
                                nd6_output_ifp(rt, rt, m, &dst, NULL);
                        } else {
                                in6_ifstat_inc(ifp, ifs6_in_toobig);
                                icmp6_error(m, ICMP6_PACKET_TOO_BIG, 0,
                                    if_getmtu(ifp));
                        }
                } else if (forward) {
                        MPASS(m->m_pkthdr.rcvif != NULL);
                        ip6_forward(m, 0);
                } else {
                        (void)ip6_output(m, NULL, NULL, 0, NULL, NULL,
                            NULL);
                }
        }

        return (action);
}
#endif /* INET6 */

#ifdef INET
int
pf_normalize_ip(u_short *reason, struct pf_pdesc *pd)
{
        struct pf_krule         *r;
        struct ip               *h = mtod(pd->m, struct ip *);
        int                      mff = (ntohs(h->ip_off) & IP_MF);
        int                      hlen = h->ip_hl << 2;
        u_int16_t                fragoff = (ntohs(h->ip_off) & IP_OFFMASK) << 3;
        u_int16_t                max;
        int                      ip_len;
        int                      tag = -1;
        int                      verdict;
        bool                     scrub_compat;

        PF_RULES_RASSERT();

        r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr);
        /*
         * Check if there are any scrub rules, matching or not.
         * Lack of scrub rules means:
         *  - enforced packet normalization operation just like in OpenBSD
         *  - fragment reassembly depends on V_pf_status.reass
         * With scrub rules:
         *  - packet normalization is performed if there is a matching scrub rule
         *  - fragment reassembly is performed if the matching rule has no
         *    PFRULE_FRAGMENT_NOREASS flag
         */
        scrub_compat = (r != NULL);
        while (r != NULL) {
                pf_counter_u64_add(&r->evaluations, 1);
                if (pfi_kkif_match(r->kif, pd->kif) == r->ifnot)
                        r = r->skip[PF_SKIP_IFP];
                else if (r->direction && r->direction != pd->dir)
                        r = r->skip[PF_SKIP_DIR];
                else if (r->af && r->af != AF_INET)
                        r = r->skip[PF_SKIP_AF];
                else if (r->proto && r->proto != h->ip_p)
                        r = r->skip[PF_SKIP_PROTO];
                else if (PF_MISMATCHAW(&r->src.addr,
                    (struct pf_addr *)&h->ip_src.s_addr, AF_INET,
                    r->src.neg, pd->kif, M_GETFIB(pd->m)))
                        r = r->skip[PF_SKIP_SRC_ADDR];
                else if (PF_MISMATCHAW(&r->dst.addr,
                    (struct pf_addr *)&h->ip_dst.s_addr, AF_INET,
                    r->dst.neg, NULL, M_GETFIB(pd->m)))
                        r = r->skip[PF_SKIP_DST_ADDR];
                else if (r->match_tag && !pf_match_tag(pd->m, r, &tag,
                    pd->pf_mtag ? pd->pf_mtag->tag : 0))
                        r = TAILQ_NEXT(r, entries);
                else
                        break;
        }

        if (scrub_compat) {
                /* With scrub rules present IPv4 normalization happens only
                 * if one of rules has matched and it's not a "no scrub" rule */
                if (r == NULL || r->action == PF_NOSCRUB)
                        return (PF_PASS);

                pf_counter_u64_critical_enter();
                pf_counter_u64_add_protected(&r->packets[pd->dir == PF_OUT], 1);
                pf_counter_u64_add_protected(&r->bytes[pd->dir == PF_OUT], pd->tot_len);
                pf_counter_u64_critical_exit();
                pf_rule_to_actions(r, &pd->act);
        }

        /* Check for illegal packets */
        if (hlen < (int)sizeof(struct ip)) {
                REASON_SET(reason, PFRES_NORM);
                goto drop;
        }

        if (hlen > ntohs(h->ip_len)) {
                REASON_SET(reason, PFRES_NORM);
                goto drop;
        }

        /* Clear IP_DF if the rule uses the no-df option or we're in no-df mode */
        if (((!scrub_compat && V_pf_status.reass & PF_REASS_NODF) ||
            (r != NULL && r->rule_flag & PFRULE_NODF)) &&
            (h->ip_off & htons(IP_DF))
        ) {
                u_int16_t ip_off = h->ip_off;

                h->ip_off &= htons(~IP_DF);
                h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_off, h->ip_off, 0);
        }

        /* We will need other tests here */
        if (!fragoff && !mff)
                goto no_fragment;

        /* We're dealing with a fragment now. Don't allow fragments
         * with IP_DF to enter the cache. If the flag was cleared by
         * no-df above, fine. Otherwise drop it.
         */
        if (h->ip_off & htons(IP_DF)) {
                DPFPRINTF(PF_DEBUG_MISC, "IP_DF");
                goto bad;
        }

        ip_len = ntohs(h->ip_len) - hlen;

        /* All fragments are 8 byte aligned */
        if (mff && (ip_len & 0x7)) {
                DPFPRINTF(PF_DEBUG_MISC, "mff and %d", ip_len);
                goto bad;
        }

        /* Respect maximum length */
        if (fragoff + ip_len > IP_MAXPACKET) {
                DPFPRINTF(PF_DEBUG_MISC, "max packet %d", fragoff + ip_len);
                goto bad;
        }

        if ((!scrub_compat && V_pf_status.reass) ||
            (r != NULL && !(r->rule_flag & PFRULE_FRAGMENT_NOREASS))
        ) {
                max = fragoff + ip_len;

                /* Fully buffer all of the fragments
                 * Might return a completely reassembled mbuf, or NULL */
                PF_FRAG_LOCK();
                DPFPRINTF(PF_DEBUG_MISC, "reass frag %d @ %d-%d",
                    h->ip_id, fragoff, max);
                verdict = pf_reassemble(&pd->m, reason);
                PF_FRAG_UNLOCK();

                if (verdict != PF_PASS)
                        return (PF_DROP);

                if (pd->m == NULL)
                        return (PF_DROP);

                h = mtod(pd->m, struct ip *);
                pd->tot_len = htons(h->ip_len);

 no_fragment:
                /* At this point, only IP_DF is allowed in ip_off */
                if (h->ip_off & ~htons(IP_DF)) {
                        u_int16_t ip_off = h->ip_off;

                        h->ip_off &= htons(IP_DF);
                        h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_off, h->ip_off, 0);
                }
        }

        return (PF_PASS);

 bad:
        DPFPRINTF(PF_DEBUG_MISC, "dropping bad fragment");
        REASON_SET(reason, PFRES_FRAG);
 drop:
        if (r != NULL && r->log)
                PFLOG_PACKET(PF_DROP, *reason, r, NULL, NULL, pd, 1, NULL);

        return (PF_DROP);
}
#endif

#ifdef INET6
int
pf_normalize_ip6(int off, u_short *reason,
    struct pf_pdesc *pd)
{
        struct pf_krule         *r;
        struct ip6_hdr          *h;
        struct ip6_frag          frag;
        bool                     scrub_compat;

        PF_RULES_RASSERT();

        r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr);
        /*
         * Check if there are any scrub rules, matching or not.
         * Lack of scrub rules means:
         *  - enforced packet normalization operation just like in OpenBSD
         * With scrub rules:
         *  - packet normalization is performed if there is a matching scrub rule
         * XXX: Fragment reassembly always performed for IPv6!
         */
        scrub_compat = (r != NULL);
        while (r != NULL) {
                pf_counter_u64_add(&r->evaluations, 1);
                if (pfi_kkif_match(r->kif, pd->kif) == r->ifnot)
                        r = r->skip[PF_SKIP_IFP];
                else if (r->direction && r->direction != pd->dir)
                        r = r->skip[PF_SKIP_DIR];
                else if (r->af && r->af != AF_INET6)
                        r = r->skip[PF_SKIP_AF];
                else if (r->proto && r->proto != pd->proto)
                        r = r->skip[PF_SKIP_PROTO];
                else if (PF_MISMATCHAW(&r->src.addr,
                    (struct pf_addr *)&pd->src, AF_INET6,
                    r->src.neg, pd->kif, M_GETFIB(pd->m)))
                        r = r->skip[PF_SKIP_SRC_ADDR];
                else if (PF_MISMATCHAW(&r->dst.addr,
                    (struct pf_addr *)&pd->dst, AF_INET6,
                    r->dst.neg, NULL, M_GETFIB(pd->m)))
                        r = r->skip[PF_SKIP_DST_ADDR];
                else
                        break;
        }

        if (scrub_compat) {
                /* With scrub rules present IPv6 normalization happens only
                 * if one of rules has matched and it's not a "no scrub" rule */
                if (r == NULL || r->action == PF_NOSCRUB)
                        return (PF_PASS);

                pf_counter_u64_critical_enter();
                pf_counter_u64_add_protected(&r->packets[pd->dir == PF_OUT], 1);
                pf_counter_u64_add_protected(&r->bytes[pd->dir == PF_OUT], pd->tot_len);
                pf_counter_u64_critical_exit();
                pf_rule_to_actions(r, &pd->act);
        }

        if (!pf_pull_hdr(pd->m, off, &frag, sizeof(frag), reason, AF_INET6))
                return (PF_DROP);

        /* Offset now points to data portion. */
        off += sizeof(frag);

        if (pd->virtual_proto == PF_VPROTO_FRAGMENT) {
                /* Returns PF_DROP or *m0 is NULL or completely reassembled
                 * mbuf. */
                if (pf_reassemble6(&pd->m, &frag, off, pd->extoff, reason) != PF_PASS)
                        return (PF_DROP);
                if (pd->m == NULL)
                        return (PF_DROP);
                h = mtod(pd->m, struct ip6_hdr *);
                pd->tot_len = ntohs(h->ip6_plen) + sizeof(struct ip6_hdr);
        }

        return (PF_PASS);
}
#endif /* INET6 */

int
pf_normalize_tcp(struct pf_pdesc *pd)
{
        struct pf_krule *r, *rm = NULL;
        struct tcphdr   *th = &pd->hdr.tcp;
        int              rewrite = 0;
        u_short          reason;
        u_int16_t        flags;
        sa_family_t      af = pd->af;
        int              srs;

        PF_RULES_RASSERT();

        r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr);
        /* Check if there any scrub rules. Lack of scrub rules means enforced
         * packet normalization operation just like in OpenBSD. */
        srs = (r != NULL);
        while (r != NULL) {
                pf_counter_u64_add(&r->evaluations, 1);
                if (pfi_kkif_match(r->kif, pd->kif) == r->ifnot)
                        r = r->skip[PF_SKIP_IFP];
                else if (r->direction && r->direction != pd->dir)
                        r = r->skip[PF_SKIP_DIR];
                else if (r->af && r->af != af)
                        r = r->skip[PF_SKIP_AF];
                else if (r->proto && r->proto != pd->proto)
                        r = r->skip[PF_SKIP_PROTO];
                else if (PF_MISMATCHAW(&r->src.addr, pd->src, af,
                    r->src.neg, pd->kif, M_GETFIB(pd->m)))
                        r = r->skip[PF_SKIP_SRC_ADDR];
                else if (r->src.port_op && !pf_match_port(r->src.port_op,
                            r->src.port[0], r->src.port[1], th->th_sport))
                        r = r->skip[PF_SKIP_SRC_PORT];
                else if (PF_MISMATCHAW(&r->dst.addr, pd->dst, af,
                    r->dst.neg, NULL, M_GETFIB(pd->m)))
                        r = r->skip[PF_SKIP_DST_ADDR];
                else if (r->dst.port_op && !pf_match_port(r->dst.port_op,
                            r->dst.port[0], r->dst.port[1], th->th_dport))
                        r = r->skip[PF_SKIP_DST_PORT];
                else if (r->os_fingerprint != PF_OSFP_ANY && !pf_osfp_match(
                            pf_osfp_fingerprint(pd, th),
                            r->os_fingerprint))
                        r = TAILQ_NEXT(r, entries);
                else {
                        rm = r;
                        break;
                }
        }

        if (srs) {
                /* With scrub rules present TCP normalization happens only
                 * if one of rules has matched and it's not a "no scrub" rule */
                if (rm == NULL || rm->action == PF_NOSCRUB)
                        return (PF_PASS);

                pf_counter_u64_critical_enter();
                pf_counter_u64_add_protected(&r->packets[pd->dir == PF_OUT], 1);
                pf_counter_u64_add_protected(&r->bytes[pd->dir == PF_OUT], pd->tot_len);
                pf_counter_u64_critical_exit();
                pf_rule_to_actions(rm, &pd->act);
        }

        if (rm && rm->rule_flag & PFRULE_REASSEMBLE_TCP)
                pd->flags |= PFDESC_TCP_NORM;

        flags = tcp_get_flags(th);
        if (flags & TH_SYN) {
                /* Illegal packet */
                if (flags & TH_RST)
                        goto tcp_drop;

                if (flags & TH_FIN)
                        goto tcp_drop;
        } else {
                /* Illegal packet */
                if (!(flags & (TH_ACK|TH_RST)))
                        goto tcp_drop;
        }

        if (!(flags & TH_ACK)) {
                /* These flags are only valid if ACK is set */
                if ((flags & TH_FIN) || (flags & TH_PUSH) || (flags & TH_URG))
                        goto tcp_drop;
        }

        /* Check for illegal header length */
        if (th->th_off < (sizeof(struct tcphdr) >> 2))
                goto tcp_drop;

        /* If flags changed, or reserved data set, then adjust */
        if (flags != tcp_get_flags(th) ||
            (tcp_get_flags(th) & (TH_RES1|TH_RES2|TH_RES2)) != 0) {
                u_int16_t       ov, nv;

                ov = *(u_int16_t *)(&th->th_ack + 1);
                flags &= ~(TH_RES1 | TH_RES2 | TH_RES3);
                tcp_set_flags(th, flags);
                nv = *(u_int16_t *)(&th->th_ack + 1);

                th->th_sum = pf_proto_cksum_fixup(pd->m, th->th_sum, ov, nv, 0);
                rewrite = 1;
        }

        /* Remove urgent pointer, if TH_URG is not set */
        if (!(flags & TH_URG) && th->th_urp) {
                th->th_sum = pf_proto_cksum_fixup(pd->m, th->th_sum, th->th_urp,
                    0, 0);
                th->th_urp = 0;
                rewrite = 1;
        }

        /* copy back packet headers if we sanitized */
        if (rewrite)
                m_copyback(pd->m, pd->off, sizeof(*th), (caddr_t)th);

        return (PF_PASS);

 tcp_drop:
        REASON_SET(&reason, PFRES_NORM);
        if (rm != NULL && r->log)
                PFLOG_PACKET(PF_DROP, reason, r, NULL, NULL, pd, 1, NULL);
        return (PF_DROP);
}

int
pf_normalize_tcp_init(struct pf_pdesc *pd, struct tcphdr *th,
    struct pf_state_peer *src)
{
        u_int32_t tsval, tsecr;
        int              olen;
        uint8_t          opts[MAX_TCPOPTLEN], *opt;

        KASSERT((src->scrub == NULL),
            ("pf_normalize_tcp_init: src->scrub != NULL"));

        src->scrub = uma_zalloc(V_pf_state_scrub_z, M_ZERO | M_NOWAIT);
        if (src->scrub == NULL)
                return (1);

        switch (pd->af) {
#ifdef INET
        case AF_INET: {
                struct ip *h = mtod(pd->m, struct ip *);
                src->scrub->pfss_ttl = h->ip_ttl;
                break;
        }
#endif /* INET */
#ifdef INET6
        case AF_INET6: {
                struct ip6_hdr *h = mtod(pd->m, struct ip6_hdr *);
                src->scrub->pfss_ttl = h->ip6_hlim;
                break;
        }
#endif /* INET6 */
        default:
                unhandled_af(pd->af);
        }

        /*
         * All normalizations below are only begun if we see the start of
         * the connections.  They must all set an enabled bit in pfss_flags
         */
        if ((tcp_get_flags(th) & TH_SYN) == 0)
                return (0);

        olen = (th->th_off << 2) - sizeof(*th);
        if (olen < TCPOLEN_TIMESTAMP || !pf_pull_hdr(pd->m,
            pd->off + sizeof(*th), opts, olen, NULL, pd->af))
                return (0);

        opt = opts;
        while ((opt = pf_find_tcpopt(opt, opts, olen,
            TCPOPT_TIMESTAMP, TCPOLEN_TIMESTAMP)) != NULL) {
                src->scrub->pfss_flags |= PFSS_TIMESTAMP;
                src->scrub->pfss_ts_mod = arc4random();
                /* note PFSS_PAWS not set yet */
                memcpy(&tsval, &opt[2], sizeof(u_int32_t));
                memcpy(&tsecr, &opt[6], sizeof(u_int32_t));
                src->scrub->pfss_tsval0 = ntohl(tsval);
                src->scrub->pfss_tsval = ntohl(tsval);
                src->scrub->pfss_tsecr = ntohl(tsecr);
                getmicrouptime(&src->scrub->pfss_last);

                opt += opt[1];
        }

        return (0);
}

void
pf_normalize_tcp_cleanup(struct pf_kstate *state)
{
        /* XXX Note: this also cleans up SCTP. */
        uma_zfree(V_pf_state_scrub_z, state->src.scrub);
        uma_zfree(V_pf_state_scrub_z, state->dst.scrub);

        /* Someday... flush the TCP segment reassembly descriptors. */
}
int
pf_normalize_sctp_init(struct pf_pdesc *pd, struct pf_state_peer *src,
    struct pf_state_peer *dst)
{
        src->scrub = uma_zalloc(V_pf_state_scrub_z, M_ZERO | M_NOWAIT);
        if (src->scrub == NULL)
                return (1);

        dst->scrub = uma_zalloc(V_pf_state_scrub_z, M_ZERO | M_NOWAIT);
        if (dst->scrub == NULL) {
                uma_zfree(V_pf_state_scrub_z, src);
                return (1);
        }

        dst->scrub->pfss_v_tag = pd->sctp_initiate_tag;

        return (0);
}

int
pf_normalize_tcp_stateful(struct pf_pdesc *pd,
    u_short *reason, struct tcphdr *th, struct pf_kstate *state,
    struct pf_state_peer *src, struct pf_state_peer *dst, int *writeback)
{
        struct timeval uptime;
        u_int tsval_from_last;
        uint32_t tsval, tsecr;
        int copyback = 0;
        int got_ts = 0;
        int olen;
        uint8_t opts[MAX_TCPOPTLEN], *opt;

        KASSERT((src->scrub || dst->scrub),
            ("%s: src->scrub && dst->scrub!", __func__));

        /*
         * Enforce the minimum TTL seen for this connection.  Negate a common
         * technique to evade an intrusion detection system and confuse
         * firewall state code.
         */
        switch (pd->af) {
#ifdef INET
        case AF_INET: {
                if (src->scrub) {
                        struct ip *h = mtod(pd->m, struct ip *);
                        if (h->ip_ttl > src->scrub->pfss_ttl)
                                src->scrub->pfss_ttl = h->ip_ttl;
                        h->ip_ttl = src->scrub->pfss_ttl;
                }
                break;
        }
#endif /* INET */
#ifdef INET6
        case AF_INET6: {
                if (src->scrub) {
                        struct ip6_hdr *h = mtod(pd->m, struct ip6_hdr *);
                        if (h->ip6_hlim > src->scrub->pfss_ttl)
                                src->scrub->pfss_ttl = h->ip6_hlim;
                        h->ip6_hlim = src->scrub->pfss_ttl;
                }
                break;
        }
#endif /* INET6 */
        default:
                unhandled_af(pd->af);
        }

        olen = (th->th_off << 2) - sizeof(*th);

        if (olen >= TCPOLEN_TIMESTAMP &&
            ((src->scrub && (src->scrub->pfss_flags & PFSS_TIMESTAMP)) ||
            (dst->scrub && (dst->scrub->pfss_flags & PFSS_TIMESTAMP))) &&
            pf_pull_hdr(pd->m, pd->off + sizeof(*th), opts, olen, NULL, pd->af)) {
                /* Modulate the timestamps.  Can be used for NAT detection, OS
                 * uptime determination or reboot detection.
                 */
                opt = opts;
                while ((opt = pf_find_tcpopt(opt, opts, olen,
                    TCPOPT_TIMESTAMP, TCPOLEN_TIMESTAMP)) != NULL) {
                        uint8_t *ts = opt + 2;
                        uint8_t *tsr = opt + 6;

                        if (got_ts) {
                                /* Huh?  Multiple timestamps!? */
                                if (V_pf_status.debug >= PF_DEBUG_MISC) {
                                        printf("pf: %s: multiple TS??", __func__);
                                        pf_print_state(state);
                                        printf("\n");
                                }
                                REASON_SET(reason, PFRES_TS);
                                return (PF_DROP);
                        }

                        memcpy(&tsval, ts, sizeof(u_int32_t));
                        memcpy(&tsecr, tsr, sizeof(u_int32_t));

                        /* modulate TS */
                        if (tsval && src->scrub &&
                            (src->scrub->pfss_flags & PFSS_TIMESTAMP)) {
                                /* tsval used further on */
                                tsval = ntohl(tsval);
                                pf_patch_32(pd,
                                    ts, htonl(tsval + src->scrub->pfss_ts_mod),
                                    PF_ALGNMNT(ts - opts));
                                copyback = 1;
                        }

                        /* modulate TS reply if any (!0) */
                        if (tsecr && dst->scrub &&
                            (dst->scrub->pfss_flags & PFSS_TIMESTAMP)) {
                                /* tsecr used further on */
                                tsecr = ntohl(tsecr) - dst->scrub->pfss_ts_mod;
                                pf_patch_32(pd, tsr, htonl(tsecr),
                                    PF_ALGNMNT(tsr - opts));
                                copyback = 1;
                        }

                        got_ts = 1;
                        opt += opt[1];
                }

                if (copyback) {
                        /* Copyback the options, caller copys back header */
                        *writeback = 1;
                        m_copyback(pd->m, pd->off + sizeof(*th), olen, opts);
                }
        }

        /*
         * Must invalidate PAWS checks on connections idle for too long.
         * The fastest allowed timestamp clock is 1ms.  That turns out to
         * be about 24 days before it wraps.  XXX Right now our lowerbound
         * TS echo check only works for the first 12 days of a connection
         * when the TS has exhausted half its 32bit space
         */
#define TS_MAX_IDLE     (24*24*60*60)
#define TS_MAX_CONN     (12*24*60*60)   /* XXX remove when better tsecr check */

        getmicrouptime(&uptime);
        if (src->scrub && (src->scrub->pfss_flags & PFSS_PAWS) &&
            (uptime.tv_sec - src->scrub->pfss_last.tv_sec > TS_MAX_IDLE ||
            time_uptime - (state->creation / 1000) > TS_MAX_CONN))  {
                if (V_pf_status.debug >= PF_DEBUG_MISC) {
                        DPFPRINTF(PF_DEBUG_MISC, "src idled out of PAWS");
                        pf_print_state(state);
                        printf("\n");
                }
                src->scrub->pfss_flags = (src->scrub->pfss_flags & ~PFSS_PAWS)
                    | PFSS_PAWS_IDLED;
        }
        if (dst->scrub && (dst->scrub->pfss_flags & PFSS_PAWS) &&
            uptime.tv_sec - dst->scrub->pfss_last.tv_sec > TS_MAX_IDLE) {
                if (V_pf_status.debug >= PF_DEBUG_MISC) {
                        DPFPRINTF(PF_DEBUG_MISC, "dst idled out of PAWS");
                        pf_print_state(state);
                        printf("\n");
                }
                dst->scrub->pfss_flags = (dst->scrub->pfss_flags & ~PFSS_PAWS)
                    | PFSS_PAWS_IDLED;
        }

        if (got_ts && src->scrub && dst->scrub &&
            (src->scrub->pfss_flags & PFSS_PAWS) &&
            (dst->scrub->pfss_flags & PFSS_PAWS)) {
                /* Validate that the timestamps are "in-window".
                 * RFC1323 describes TCP Timestamp options that allow
                 * measurement of RTT (round trip time) and PAWS
                 * (protection against wrapped sequence numbers).  PAWS
                 * gives us a set of rules for rejecting packets on
                 * long fat pipes (packets that were somehow delayed
                 * in transit longer than the time it took to send the
                 * full TCP sequence space of 4Gb).  We can use these
                 * rules and infer a few others that will let us treat
                 * the 32bit timestamp and the 32bit echoed timestamp
                 * as sequence numbers to prevent a blind attacker from
                 * inserting packets into a connection.
                 *
                 * RFC1323 tells us:
                 *  - The timestamp on this packet must be greater than
                 *    or equal to the last value echoed by the other
                 *    endpoint.  The RFC says those will be discarded
                 *    since it is a dup that has already been acked.
                 *    This gives us a lowerbound on the timestamp.
                 *        timestamp >= other last echoed timestamp
                 *  - The timestamp will be less than or equal to
                 *    the last timestamp plus the time between the
                 *    last packet and now.  The RFC defines the max
                 *    clock rate as 1ms.  We will allow clocks to be
                 *    up to 10% fast and will allow a total difference
                 *    or 30 seconds due to a route change.  And this
                 *    gives us an upperbound on the timestamp.
                 *        timestamp <= last timestamp + max ticks
                 *    We have to be careful here.  Windows will send an
                 *    initial timestamp of zero and then initialize it
                 *    to a random value after the 3whs; presumably to
                 *    avoid a DoS by having to call an expensive RNG
                 *    during a SYN flood.  Proof MS has at least one
                 *    good security geek.
                 *
                 *  - The TCP timestamp option must also echo the other
                 *    endpoints timestamp.  The timestamp echoed is the
                 *    one carried on the earliest unacknowledged segment
                 *    on the left edge of the sequence window.  The RFC
                 *    states that the host will reject any echoed
                 *    timestamps that were larger than any ever sent.
                 *    This gives us an upperbound on the TS echo.
                 *        tescr <= largest_tsval
                 *  - The lowerbound on the TS echo is a little more
                 *    tricky to determine.  The other endpoint's echoed
                 *    values will not decrease.  But there may be
                 *    network conditions that re-order packets and
                 *    cause our view of them to decrease.  For now the
                 *    only lowerbound we can safely determine is that
                 *    the TS echo will never be less than the original
                 *    TS.  XXX There is probably a better lowerbound.
                 *    Remove TS_MAX_CONN with better lowerbound check.
                 *        tescr >= other original TS
                 *
                 * It is also important to note that the fastest
                 * timestamp clock of 1ms will wrap its 32bit space in
                 * 24 days.  So we just disable TS checking after 24
                 * days of idle time.  We actually must use a 12d
                 * connection limit until we can come up with a better
                 * lowerbound to the TS echo check.
                 */
                struct timeval delta_ts;
                int ts_fudge;

                /*
                 * PFTM_TS_DIFF is how many seconds of leeway to allow
                 * a host's timestamp.  This can happen if the previous
                 * packet got delayed in transit for much longer than
                 * this packet.
                 */
                if ((ts_fudge = state->rule->timeout[PFTM_TS_DIFF]) == 0)
                        ts_fudge = V_pf_default_rule.timeout[PFTM_TS_DIFF];

                /* Calculate max ticks since the last timestamp */
#define TS_MAXFREQ      1100            /* RFC max TS freq of 1Khz + 10% skew */
#define TS_MICROSECS    1000000         /* microseconds per second */
                delta_ts = uptime;
                timevalsub(&delta_ts, &src->scrub->pfss_last);
                tsval_from_last = (delta_ts.tv_sec + ts_fudge) * TS_MAXFREQ;
                tsval_from_last += delta_ts.tv_usec / (TS_MICROSECS/TS_MAXFREQ);

                if ((src->state >= TCPS_ESTABLISHED &&
                    dst->state >= TCPS_ESTABLISHED) &&
                    (SEQ_LT(tsval, dst->scrub->pfss_tsecr) ||
                    SEQ_GT(tsval, src->scrub->pfss_tsval + tsval_from_last) ||
                    (tsecr && (SEQ_GT(tsecr, dst->scrub->pfss_tsval) ||
                    SEQ_LT(tsecr, dst->scrub->pfss_tsval0))))) {
                        /* Bad RFC1323 implementation or an insertion attack.
                         *
                         * - Solaris 2.6 and 2.7 are known to send another ACK
                         *   after the FIN,FIN|ACK,ACK closing that carries
                         *   an old timestamp.
                         */

                        DPFPRINTF(PF_DEBUG_MISC, "Timestamp failed %c%c%c%c",
                            SEQ_LT(tsval, dst->scrub->pfss_tsecr) ? '0' : ' ',
                            SEQ_GT(tsval, src->scrub->pfss_tsval +
                            tsval_from_last) ? '1' : ' ',
                            SEQ_GT(tsecr, dst->scrub->pfss_tsval) ? '2' : ' ',
                            SEQ_LT(tsecr, dst->scrub->pfss_tsval0)? '3' : ' ');
                        DPFPRINTF(PF_DEBUG_MISC, " tsval: %u  tsecr: %u  +ticks: "
                            "%u  idle: %jus %lums",
                            tsval, tsecr, tsval_from_last,
                            (uintmax_t)delta_ts.tv_sec,
                            delta_ts.tv_usec / 1000);
                        DPFPRINTF(PF_DEBUG_MISC, " src->tsval: %u  tsecr: %u",
                            src->scrub->pfss_tsval, src->scrub->pfss_tsecr);
                        DPFPRINTF(PF_DEBUG_MISC, " dst->tsval: %u  tsecr: %u  "
                            "tsval0: %u", dst->scrub->pfss_tsval,
                            dst->scrub->pfss_tsecr, dst->scrub->pfss_tsval0);
                        if (V_pf_status.debug >= PF_DEBUG_MISC) {
                                pf_print_state(state);
                                pf_print_flags(tcp_get_flags(th));
                                printf("\n");
                        }
                        REASON_SET(reason, PFRES_TS);
                        return (PF_DROP);
                }

                /* XXX I'd really like to require tsecr but it's optional */

        } else if (!got_ts && (tcp_get_flags(th) & TH_RST) == 0 &&
            ((src->state == TCPS_ESTABLISHED && dst->state == TCPS_ESTABLISHED)
            || pd->p_len > 0 || (tcp_get_flags(th) & TH_SYN)) &&
            src->scrub && dst->scrub &&
            (src->scrub->pfss_flags & PFSS_PAWS) &&
            (dst->scrub->pfss_flags & PFSS_PAWS)) {
                /* Didn't send a timestamp.  Timestamps aren't really useful
                 * when:
                 *  - connection opening or closing (often not even sent).
                 *    but we must not let an attacker to put a FIN on a
                 *    data packet to sneak it through our ESTABLISHED check.
                 *  - on a TCP reset.  RFC suggests not even looking at TS.
                 *  - on an empty ACK.  The TS will not be echoed so it will
                 *    probably not help keep the RTT calculation in sync and
                 *    there isn't as much danger when the sequence numbers
                 *    got wrapped.  So some stacks don't include TS on empty
                 *    ACKs :-(
                 *
                 * To minimize the disruption to mostly RFC1323 conformant
                 * stacks, we will only require timestamps on data packets.
                 *
                 * And what do ya know, we cannot require timestamps on data
                 * packets.  There appear to be devices that do legitimate
                 * TCP connection hijacking.  There are HTTP devices that allow
                 * a 3whs (with timestamps) and then buffer the HTTP request.
                 * If the intermediate device has the HTTP response cache, it
                 * will spoof the response but not bother timestamping its
                 * packets.  So we can look for the presence of a timestamp in
                 * the first data packet and if there, require it in all future
                 * packets.
                 */

                if (pd->p_len > 0 && (src->scrub->pfss_flags & PFSS_DATA_TS)) {
                        /*
                         * Hey!  Someone tried to sneak a packet in.  Or the
                         * stack changed its RFC1323 behavior?!?!
                         */
                        if (V_pf_status.debug >= PF_DEBUG_MISC) {
                                DPFPRINTF(PF_DEBUG_MISC, "Did not receive expected "
                                    "RFC1323 timestamp");
                                pf_print_state(state);
                                pf_print_flags(tcp_get_flags(th));
                                printf("\n");
                        }
                        REASON_SET(reason, PFRES_TS);
                        return (PF_DROP);
                }
        }

        /*
         * We will note if a host sends his data packets with or without
         * timestamps.  And require all data packets to contain a timestamp
         * if the first does.  PAWS implicitly requires that all data packets be
         * timestamped.  But I think there are middle-man devices that hijack
         * TCP streams immediately after the 3whs and don't timestamp their
         * packets (seen in a WWW accelerator or cache).
         */
        if (pd->p_len > 0 && src->scrub && (src->scrub->pfss_flags &
            (PFSS_TIMESTAMP|PFSS_DATA_TS|PFSS_DATA_NOTS)) == PFSS_TIMESTAMP) {
                if (got_ts)
                        src->scrub->pfss_flags |= PFSS_DATA_TS;
                else {
                        src->scrub->pfss_flags |= PFSS_DATA_NOTS;
                        if (V_pf_status.debug >= PF_DEBUG_MISC && dst->scrub &&
                            (dst->scrub->pfss_flags & PFSS_TIMESTAMP)) {
                                /* Don't warn if other host rejected RFC1323 */
                                DPFPRINTF(PF_DEBUG_MISC, "Broken RFC1323 stack did "
                                    "not timestamp data packet. Disabled PAWS "
                                    "security.");
                                pf_print_state(state);
                                pf_print_flags(tcp_get_flags(th));
                                printf("\n");
                        }
                }
        }

        /*
         * Update PAWS values
         */
        if (got_ts && src->scrub && PFSS_TIMESTAMP == (src->scrub->pfss_flags &
            (PFSS_PAWS_IDLED|PFSS_TIMESTAMP))) {
                getmicrouptime(&src->scrub->pfss_last);
                if (SEQ_GEQ(tsval, src->scrub->pfss_tsval) ||
                    (src->scrub->pfss_flags & PFSS_PAWS) == 0)
                        src->scrub->pfss_tsval = tsval;

                if (tsecr) {
                        if (SEQ_GEQ(tsecr, src->scrub->pfss_tsecr) ||
                            (src->scrub->pfss_flags & PFSS_PAWS) == 0)
                                src->scrub->pfss_tsecr = tsecr;

                        if ((src->scrub->pfss_flags & PFSS_PAWS) == 0 &&
                            (SEQ_LT(tsval, src->scrub->pfss_tsval0) ||
                            src->scrub->pfss_tsval0 == 0)) {
                                /* tsval0 MUST be the lowest timestamp */
                                src->scrub->pfss_tsval0 = tsval;
                        }

                        /* Only fully initialized after a TS gets echoed */
                        if ((src->scrub->pfss_flags & PFSS_PAWS) == 0)
                                src->scrub->pfss_flags |= PFSS_PAWS;
                }
        }

        /* I have a dream....  TCP segment reassembly.... */
        return (0);
}

int
pf_normalize_mss(struct pf_pdesc *pd)
{
        int              olen, optsoff;
        uint8_t          opts[MAX_TCPOPTLEN], *opt;

        olen = (pd->hdr.tcp.th_off << 2) - sizeof(struct tcphdr);
        optsoff = pd->off + sizeof(struct tcphdr);
        if (olen < TCPOLEN_MAXSEG ||
            !pf_pull_hdr(pd->m, optsoff, opts, olen, NULL, pd->af))
                return (0);

        opt = opts;
        while ((opt = pf_find_tcpopt(opt, opts, olen,
            TCPOPT_MAXSEG, TCPOLEN_MAXSEG)) != NULL) {
                uint16_t         mss;
                uint8_t         *mssp = opt + 2;
                memcpy(&mss, mssp, sizeof(mss));
                if (ntohs(mss) > pd->act.max_mss) {
                        size_t mssoffopts = mssp - opts;
                        pf_patch_16(pd, &mss,
                            htons(pd->act.max_mss), PF_ALGNMNT(mssoffopts));
                        m_copyback(pd->m, optsoff + mssoffopts,
                            sizeof(mss), (caddr_t)&mss);
                        m_copyback(pd->m, pd->off,
                            sizeof(struct tcphdr), (caddr_t)&pd->hdr.tcp);
                }

                opt += opt[1];
        }

        return (0);
}

int
pf_scan_sctp(struct pf_pdesc *pd)
{
        struct sctp_chunkhdr ch = { };
        int chunk_off = sizeof(struct sctphdr);
        int chunk_start;
        int ret;

        while (pd->off + chunk_off < pd->tot_len) {
                if (!pf_pull_hdr(pd->m, pd->off + chunk_off, &ch, sizeof(ch),
                    NULL, pd->af))
                        return (PF_DROP);

                /* Length includes the header, this must be at least 4. */
                if (ntohs(ch.chunk_length) < 4)
                        return (PF_DROP);

                chunk_start = chunk_off;
                chunk_off += roundup(ntohs(ch.chunk_length), 4);

                switch (ch.chunk_type) {
                case SCTP_INITIATION:
                case SCTP_INITIATION_ACK: {
                        struct sctp_init_chunk init;

                        if (!pf_pull_hdr(pd->m, pd->off + chunk_start, &init,
                            sizeof(init), NULL, pd->af))
                                return (PF_DROP);

                        /*
                         * RFC 9620, Section 3.3.2, "The Initiate Tag is allowed to have
                         * any value except 0."
                         */
                        if (init.init.initiate_tag == 0)
                                return (PF_DROP);
                        if (init.init.num_inbound_streams == 0)
                                return (PF_DROP);
                        if (init.init.num_outbound_streams == 0)
                                return (PF_DROP);
                        if (ntohl(init.init.a_rwnd) < SCTP_MIN_RWND)
                                return (PF_DROP);

                        /*
                         * RFC 9260, Section 3.1, INIT chunks MUST have zero
                         * verification tag.
                         */
                        if (ch.chunk_type == SCTP_INITIATION &&
                            pd->hdr.sctp.v_tag != 0)
                                return (PF_DROP);

                        pd->sctp_initiate_tag = init.init.initiate_tag;

                        if (ch.chunk_type == SCTP_INITIATION)
                                pd->sctp_flags |= PFDESC_SCTP_INIT;
                        else
                                pd->sctp_flags |= PFDESC_SCTP_INIT_ACK;

                        ret = pf_multihome_scan_init(pd->off + chunk_start,
                            ntohs(init.ch.chunk_length), pd);
                        if (ret != PF_PASS)
                                return (ret);

                        break;
                }
                case SCTP_ABORT_ASSOCIATION:
                        pd->sctp_flags |= PFDESC_SCTP_ABORT;
                        break;
                case SCTP_SHUTDOWN:
                case SCTP_SHUTDOWN_ACK:
                        pd->sctp_flags |= PFDESC_SCTP_SHUTDOWN;
                        break;
                case SCTP_SHUTDOWN_COMPLETE:
                        pd->sctp_flags |= PFDESC_SCTP_SHUTDOWN_COMPLETE;
                        break;
                case SCTP_COOKIE_ECHO:
                        pd->sctp_flags |= PFDESC_SCTP_COOKIE;
                        break;
                case SCTP_COOKIE_ACK:
                        pd->sctp_flags |= PFDESC_SCTP_COOKIE_ACK;
                        break;
                case SCTP_DATA:
                        pd->sctp_flags |= PFDESC_SCTP_DATA;
                        break;
                case SCTP_HEARTBEAT_REQUEST:
                        pd->sctp_flags |= PFDESC_SCTP_HEARTBEAT;
                        break;
                case SCTP_HEARTBEAT_ACK:
                        pd->sctp_flags |= PFDESC_SCTP_HEARTBEAT_ACK;
                        break;
                case SCTP_ASCONF:
                        pd->sctp_flags |= PFDESC_SCTP_ASCONF;

                        ret = pf_multihome_scan_asconf(pd->off + chunk_start,
                            ntohs(ch.chunk_length), pd);
                        if (ret != PF_PASS)
                                return (ret);
                        break;
                default:
                        pd->sctp_flags |= PFDESC_SCTP_OTHER;
                        break;
                }
        }

        /* Validate chunk lengths vs. packet length. */
        if (pd->off + chunk_off != pd->tot_len)
                return (PF_DROP);

        /*
         * INIT, INIT_ACK or SHUTDOWN_COMPLETE chunks must always be the only
         * one in a packet.
         */
        if ((pd->sctp_flags & PFDESC_SCTP_INIT) &&
            (pd->sctp_flags & ~PFDESC_SCTP_INIT))
                return (PF_DROP);
        if ((pd->sctp_flags & PFDESC_SCTP_INIT_ACK) &&
            (pd->sctp_flags & ~PFDESC_SCTP_INIT_ACK))
                return (PF_DROP);
        if ((pd->sctp_flags & PFDESC_SCTP_SHUTDOWN_COMPLETE) &&
            (pd->sctp_flags & ~PFDESC_SCTP_SHUTDOWN_COMPLETE))
                return (PF_DROP);
        if ((pd->sctp_flags & PFDESC_SCTP_ABORT) &&
            (pd->sctp_flags & PFDESC_SCTP_DATA)) {
                /*
                 * RFC4960 3.3.7: DATA chunks MUST NOT be
                 * bundled with ABORT.
                 */
                return (PF_DROP);
        }

        return (PF_PASS);
}

int
pf_normalize_sctp(struct pf_pdesc *pd)
{
        struct pf_krule *r, *rm = NULL;
        struct sctphdr  *sh = &pd->hdr.sctp;
        u_short          reason;
        sa_family_t      af = pd->af;
        int              srs;

        PF_RULES_RASSERT();

        r = TAILQ_FIRST(pf_main_ruleset.rules[PF_RULESET_SCRUB].active.ptr);
        /* Check if there any scrub rules. Lack of scrub rules means enforced
         * packet normalization operation just like in OpenBSD. */
        srs = (r != NULL);
        while (r != NULL) {
                pf_counter_u64_add(&r->evaluations, 1);
                if (pfi_kkif_match(r->kif, pd->kif) == r->ifnot)
                        r = r->skip[PF_SKIP_IFP];
                else if (r->direction && r->direction != pd->dir)
                        r = r->skip[PF_SKIP_DIR];
                else if (r->af && r->af != af)
                        r = r->skip[PF_SKIP_AF];
                else if (r->proto && r->proto != pd->proto)
                        r = r->skip[PF_SKIP_PROTO];
                else if (PF_MISMATCHAW(&r->src.addr, pd->src, af,
                    r->src.neg, pd->kif, M_GETFIB(pd->m)))
                        r = r->skip[PF_SKIP_SRC_ADDR];
                else if (r->src.port_op && !pf_match_port(r->src.port_op,
                            r->src.port[0], r->src.port[1], sh->src_port))
                        r = r->skip[PF_SKIP_SRC_PORT];
                else if (PF_MISMATCHAW(&r->dst.addr, pd->dst, af,
                    r->dst.neg, NULL, M_GETFIB(pd->m)))
                        r = r->skip[PF_SKIP_DST_ADDR];
                else if (r->dst.port_op && !pf_match_port(r->dst.port_op,
                            r->dst.port[0], r->dst.port[1], sh->dest_port))
                        r = r->skip[PF_SKIP_DST_PORT];
                else {
                        rm = r;
                        break;
                }
        }

        if (srs) {
                /* With scrub rules present SCTP normalization happens only
                 * if one of rules has matched and it's not a "no scrub" rule */
                if (rm == NULL || rm->action == PF_NOSCRUB)
                        return (PF_PASS);

                pf_counter_u64_critical_enter();
                pf_counter_u64_add_protected(&r->packets[pd->dir == PF_OUT], 1);
                pf_counter_u64_add_protected(&r->bytes[pd->dir == PF_OUT], pd->tot_len);
                pf_counter_u64_critical_exit();
        }

        /* Verify we're a multiple of 4 bytes long */
        if ((pd->tot_len - pd->off - sizeof(struct sctphdr)) % 4)
                goto sctp_drop;

        /* INIT chunk needs to be the only chunk */
        if (pd->sctp_flags & PFDESC_SCTP_INIT)
                if (pd->sctp_flags & ~PFDESC_SCTP_INIT)
                        goto sctp_drop;

        return (PF_PASS);

sctp_drop:
        REASON_SET(&reason, PFRES_NORM);
        if (rm != NULL && r->log)
                PFLOG_PACKET(PF_DROP, reason, r, NULL, NULL, pd,
                    1, NULL);

        return (PF_DROP);
}

#if defined(INET) || defined(INET6)
void
pf_scrub(struct pf_pdesc *pd)
{

        struct ip               *h = mtod(pd->m, struct ip *);
#ifdef INET6
        struct ip6_hdr          *h6 = mtod(pd->m, struct ip6_hdr *);
#endif /* INET6 */

        /* Clear IP_DF if no-df was requested */
        if (pd->af == AF_INET && pd->act.flags & PFSTATE_NODF &&
            h->ip_off & htons(IP_DF))
        {
                u_int16_t ip_off = h->ip_off;

                h->ip_off &= htons(~IP_DF);
                h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_off, h->ip_off, 0);
        }

        /* Enforce a minimum ttl, may cause endless packet loops */
        if (pd->af == AF_INET && pd->act.min_ttl &&
            h->ip_ttl < pd->act.min_ttl) {
                u_int16_t ip_ttl = h->ip_ttl;

                pd->ttl = h->ip_ttl = pd->act.min_ttl;
                h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_ttl, h->ip_ttl, 0);
        }
#ifdef INET6
        /* Enforce a minimum ttl, may cause endless packet loops */
        if (pd->af == AF_INET6 && pd->act.min_ttl &&
            h6->ip6_hlim < pd->act.min_ttl)
                pd->ttl = h6->ip6_hlim = pd->act.min_ttl;
#endif /* INET6 */
        /* Enforce tos */
        if (pd->act.flags & PFSTATE_SETTOS) {
                switch (pd->af) {
                case AF_INET: {
                        u_int16_t       ov, nv;

                        ov = *(u_int16_t *)h;
                        h->ip_tos = pd->act.set_tos | (h->ip_tos & IPTOS_ECN_MASK);
                        pd->tos = h->ip_tos & ~IPTOS_ECN_MASK;
                        nv = *(u_int16_t *)h;

                        h->ip_sum = pf_cksum_fixup(h->ip_sum, ov, nv, 0);
                        break;
                }
#ifdef INET6
                case AF_INET6:
                        h6->ip6_flow &= IPV6_FLOWLABEL_MASK | IPV6_VERSION_MASK;
                        h6->ip6_flow |= htonl((pd->act.set_tos | IPV6_ECN(h6)) << 20);
                        pd->tos = IPV6_DSCP(h6);
                        break;
#endif /* INET6 */
                }
        }

        /* random-id, but not for fragments */
#ifdef INET
        if (pd->af == AF_INET &&
            pd->act.flags & PFSTATE_RANDOMID && !(h->ip_off & ~htons(IP_DF))) {
                uint16_t ip_id = h->ip_id;

                ip_fillid(h, V_ip_random_id);
                h->ip_sum = pf_cksum_fixup(h->ip_sum, ip_id, h->ip_id, 0);
        }
#endif /* INET */
}
#endif /* INET || INET6 */