[ARM] 3335/1: Old-abi Thumb sys_syscall broken

[linux-2.6/linux-loongson.git] / net / ipv6 / netfilter / nf_conntrack_reasm.c

/*
 * IPv6 fragment reassembly for connection tracking
 *
 * Copyright (C)2004 USAGI/WIDE Project
 *
 * Author:
 *      Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
 *
 * Based on: net/ipv6/reassembly.c
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/config.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/string.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/jiffies.h>
#include <linux/net.h>
#include <linux/list.h>
#include <linux/netdevice.h>
#include <linux/in6.h>
#include <linux/ipv6.h>
#include <linux/icmpv6.h>
#include <linux/random.h>
#include <linux/jhash.h>

#include <net/sock.h>
#include <net/snmp.h>

#include <net/ipv6.h>
#include <net/protocol.h>
#include <net/transp_v6.h>
#include <net/rawv6.h>
#include <net/ndisc.h>
#include <net/addrconf.h>
#include <linux/sysctl.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv6.h>
#include <linux/kernel.h>
#include <linux/module.h>

#if 0
#define DEBUGP printk
#else
#define DEBUGP(format, args...)
#endif

#define NF_CT_FRAG6_HIGH_THRESH 262144 /* == 256*1024 */
#define NF_CT_FRAG6_LOW_THRESH 196608  /* == 192*1024 */
#define NF_CT_FRAG6_TIMEOUT IPV6_FRAG_TIMEOUT

unsigned int nf_ct_frag6_high_thresh = 256*1024;
unsigned int nf_ct_frag6_low_thresh = 192*1024;
unsigned long nf_ct_frag6_timeout = IPV6_FRAG_TIMEOUT;

struct nf_ct_frag6_skb_cb
{
        struct inet6_skb_parm   h;
        int                     offset;
        struct sk_buff          *orig;
};

#define NFCT_FRAG6_CB(skb)      ((struct nf_ct_frag6_skb_cb*)((skb)->cb))

struct nf_ct_frag6_queue
{
        struct hlist_node       list;
        struct list_head        lru_list;       /* lru list member      */

        __u32                   id;             /* fragment id          */
        struct in6_addr         saddr;
        struct in6_addr         daddr;

        spinlock_t              lock;
        atomic_t                refcnt;
        struct timer_list       timer;          /* expire timer         */
        struct sk_buff          *fragments;
        int                     len;
        int                     meat;
        struct timeval          stamp;
        unsigned int            csum;
        __u8                    last_in;        /* has first/last segment arrived? */
#define COMPLETE                4
#define FIRST_IN                2
#define LAST_IN                 1
        __u16                   nhoffset;
};

/* Hash table. */

#define FRAG6Q_HASHSZ   64

static struct hlist_head nf_ct_frag6_hash[FRAG6Q_HASHSZ];
static DEFINE_RWLOCK(nf_ct_frag6_lock);
static u32 nf_ct_frag6_hash_rnd;
static LIST_HEAD(nf_ct_frag6_lru_list);
int nf_ct_frag6_nqueues = 0;

static __inline__ void __fq_unlink(struct nf_ct_frag6_queue *fq)
{
        hlist_del(&fq->list);
        list_del(&fq->lru_list);
        nf_ct_frag6_nqueues--;
}

static __inline__ void fq_unlink(struct nf_ct_frag6_queue *fq)
{
        write_lock(&nf_ct_frag6_lock);
        __fq_unlink(fq);
        write_unlock(&nf_ct_frag6_lock);
}

static unsigned int ip6qhashfn(u32 id, struct in6_addr *saddr,
                               struct in6_addr *daddr)
{
        u32 a, b, c;

        a = saddr->s6_addr32[0];
        b = saddr->s6_addr32[1];
        c = saddr->s6_addr32[2];

        a += JHASH_GOLDEN_RATIO;
        b += JHASH_GOLDEN_RATIO;
        c += nf_ct_frag6_hash_rnd;
        __jhash_mix(a, b, c);

        a += saddr->s6_addr32[3];
        b += daddr->s6_addr32[0];
        c += daddr->s6_addr32[1];
        __jhash_mix(a, b, c);

        a += daddr->s6_addr32[2];
        b += daddr->s6_addr32[3];
        c += id;
        __jhash_mix(a, b, c);

        return c & (FRAG6Q_HASHSZ - 1);
}

static struct timer_list nf_ct_frag6_secret_timer;
int nf_ct_frag6_secret_interval = 10 * 60 * HZ;

static void nf_ct_frag6_secret_rebuild(unsigned long dummy)
{
        unsigned long now = jiffies;
        int i;

        write_lock(&nf_ct_frag6_lock);
        get_random_bytes(&nf_ct_frag6_hash_rnd, sizeof(u32));
        for (i = 0; i < FRAG6Q_HASHSZ; i++) {
                struct nf_ct_frag6_queue *q;
                struct hlist_node *p, *n;

                hlist_for_each_entry_safe(q, p, n, &nf_ct_frag6_hash[i], list) {
                        unsigned int hval = ip6qhashfn(q->id,
                                                       &q->saddr,
                                                       &q->daddr);
                        if (hval != i) {
                                hlist_del(&q->list);
                                /* Relink to new hash chain. */
                                hlist_add_head(&q->list,
                                               &nf_ct_frag6_hash[hval]);
                        }
                }
        }
        write_unlock(&nf_ct_frag6_lock);

        mod_timer(&nf_ct_frag6_secret_timer, now + nf_ct_frag6_secret_interval);
}

atomic_t nf_ct_frag6_mem = ATOMIC_INIT(0);

/* Memory Tracking Functions. */
static inline void frag_kfree_skb(struct sk_buff *skb, unsigned int *work)
{
        if (work)
                *work -= skb->truesize;
        atomic_sub(skb->truesize, &nf_ct_frag6_mem);
        if (NFCT_FRAG6_CB(skb)->orig)
                kfree_skb(NFCT_FRAG6_CB(skb)->orig);

        kfree_skb(skb);
}

static inline void frag_free_queue(struct nf_ct_frag6_queue *fq,
                                   unsigned int *work)
{
        if (work)
                *work -= sizeof(struct nf_ct_frag6_queue);
        atomic_sub(sizeof(struct nf_ct_frag6_queue), &nf_ct_frag6_mem);
        kfree(fq);
}

static inline struct nf_ct_frag6_queue *frag_alloc_queue(void)
{
        struct nf_ct_frag6_queue *fq = kmalloc(sizeof(struct nf_ct_frag6_queue), GFP_ATOMIC);

        if (!fq)
                return NULL;
        atomic_add(sizeof(struct nf_ct_frag6_queue), &nf_ct_frag6_mem);
        return fq;
}

/* Destruction primitives. */

/* Complete destruction of fq. */
static void nf_ct_frag6_destroy(struct nf_ct_frag6_queue *fq,
                                unsigned int *work)
{
        struct sk_buff *fp;

        BUG_TRAP(fq->last_in&COMPLETE);
        BUG_TRAP(del_timer(&fq->timer) == 0);

        /* Release all fragment data. */
        fp = fq->fragments;
        while (fp) {
                struct sk_buff *xp = fp->next;

                frag_kfree_skb(fp, work);
                fp = xp;
        }

        frag_free_queue(fq, work);
}

static __inline__ void fq_put(struct nf_ct_frag6_queue *fq, unsigned int *work)
{
        if (atomic_dec_and_test(&fq->refcnt))
                nf_ct_frag6_destroy(fq, work);
}

/* Kill fq entry. It is not destroyed immediately,
 * because caller (and someone more) holds reference count.
 */
static __inline__ void fq_kill(struct nf_ct_frag6_queue *fq)
{
        if (del_timer(&fq->timer))
                atomic_dec(&fq->refcnt);

        if (!(fq->last_in & COMPLETE)) {
                fq_unlink(fq);
                atomic_dec(&fq->refcnt);
                fq->last_in |= COMPLETE;
        }
}

static void nf_ct_frag6_evictor(void)
{
        struct nf_ct_frag6_queue *fq;
        struct list_head *tmp;
        unsigned int work;

        work = atomic_read(&nf_ct_frag6_mem);
        if (work <= nf_ct_frag6_low_thresh)
                return;

        work -= nf_ct_frag6_low_thresh;
        while (work > 0) {
                read_lock(&nf_ct_frag6_lock);
                if (list_empty(&nf_ct_frag6_lru_list)) {
                        read_unlock(&nf_ct_frag6_lock);
                        return;
                }
                tmp = nf_ct_frag6_lru_list.next;
                BUG_ON(tmp == NULL);
                fq = list_entry(tmp, struct nf_ct_frag6_queue, lru_list);
                atomic_inc(&fq->refcnt);
                read_unlock(&nf_ct_frag6_lock);

                spin_lock(&fq->lock);
                if (!(fq->last_in&COMPLETE))
                        fq_kill(fq);
                spin_unlock(&fq->lock);

                fq_put(fq, &work);
        }
}

static void nf_ct_frag6_expire(unsigned long data)
{
        struct nf_ct_frag6_queue *fq = (struct nf_ct_frag6_queue *) data;

        spin_lock(&fq->lock);

        if (fq->last_in & COMPLETE)
                goto out;

        fq_kill(fq);

out:
        spin_unlock(&fq->lock);
        fq_put(fq, NULL);
}

/* Creation primitives. */

static struct nf_ct_frag6_queue *nf_ct_frag6_intern(unsigned int hash,
                                          struct nf_ct_frag6_queue *fq_in)
{
        struct nf_ct_frag6_queue *fq;
#ifdef CONFIG_SMP
        struct hlist_node *n;
#endif

        write_lock(&nf_ct_frag6_lock);
#ifdef CONFIG_SMP
        hlist_for_each_entry(fq, n, &nf_ct_frag6_hash[hash], list) {
                if (fq->id == fq_in->id && 
                    ipv6_addr_equal(&fq_in->saddr, &fq->saddr) &&
                    ipv6_addr_equal(&fq_in->daddr, &fq->daddr)) {
                        atomic_inc(&fq->refcnt);
                        write_unlock(&nf_ct_frag6_lock);
                        fq_in->last_in |= COMPLETE;
                        fq_put(fq_in, NULL);
                        return fq;
                }
        }
#endif
        fq = fq_in;

        if (!mod_timer(&fq->timer, jiffies + nf_ct_frag6_timeout))
                atomic_inc(&fq->refcnt);

        atomic_inc(&fq->refcnt);
        hlist_add_head(&fq->list, &nf_ct_frag6_hash[hash]);
        INIT_LIST_HEAD(&fq->lru_list);
        list_add_tail(&fq->lru_list, &nf_ct_frag6_lru_list);
        nf_ct_frag6_nqueues++;
        write_unlock(&nf_ct_frag6_lock);
        return fq;
}


static struct nf_ct_frag6_queue *
nf_ct_frag6_create(unsigned int hash, u32 id, struct in6_addr *src,                                struct in6_addr *dst)
{
        struct nf_ct_frag6_queue *fq;

        if ((fq = frag_alloc_queue()) == NULL) {
                DEBUGP("Can't alloc new queue\n");
                goto oom;
        }

        memset(fq, 0, sizeof(struct nf_ct_frag6_queue));

        fq->id = id;
        ipv6_addr_copy(&fq->saddr, src);
        ipv6_addr_copy(&fq->daddr, dst);

        init_timer(&fq->timer);
        fq->timer.function = nf_ct_frag6_expire;
        fq->timer.data = (long) fq;
        spin_lock_init(&fq->lock);
        atomic_set(&fq->refcnt, 1);

        return nf_ct_frag6_intern(hash, fq);

oom:
        return NULL;
}

static __inline__ struct nf_ct_frag6_queue *
fq_find(u32 id, struct in6_addr *src, struct in6_addr *dst)
{
        struct nf_ct_frag6_queue *fq;
        struct hlist_node *n;
        unsigned int hash = ip6qhashfn(id, src, dst);

        read_lock(&nf_ct_frag6_lock);
        hlist_for_each_entry(fq, n, &nf_ct_frag6_hash[hash], list) {
                if (fq->id == id && 
                    ipv6_addr_equal(src, &fq->saddr) &&
                    ipv6_addr_equal(dst, &fq->daddr)) {
                        atomic_inc(&fq->refcnt);
                        read_unlock(&nf_ct_frag6_lock);
                        return fq;
                }
        }
        read_unlock(&nf_ct_frag6_lock);

        return nf_ct_frag6_create(hash, id, src, dst);
}


static int nf_ct_frag6_queue(struct nf_ct_frag6_queue *fq, struct sk_buff *skb, 
                             struct frag_hdr *fhdr, int nhoff)
{
        struct sk_buff *prev, *next;
        int offset, end;

        if (fq->last_in & COMPLETE) {
                DEBUGP("Allready completed\n");
                goto err;
        }

        offset = ntohs(fhdr->frag_off) & ~0x7;
        end = offset + (ntohs(skb->nh.ipv6h->payload_len) -
                        ((u8 *) (fhdr + 1) - (u8 *) (skb->nh.ipv6h + 1)));

        if ((unsigned int)end > IPV6_MAXPLEN) {
                DEBUGP("offset is too large.\n");
                return -1;
        }

        if (skb->ip_summed == CHECKSUM_HW)
                skb->csum = csum_sub(skb->csum,
                                     csum_partial(skb->nh.raw,
                                                  (u8*)(fhdr + 1) - skb->nh.raw,
                                                  0));

        /* Is this the final fragment? */
        if (!(fhdr->frag_off & htons(IP6_MF))) {
                /* If we already have some bits beyond end
                 * or have different end, the segment is corrupted.
                 */
                if (end < fq->len ||
                    ((fq->last_in & LAST_IN) && end != fq->len)) {
                        DEBUGP("already received last fragment\n");
                        goto err;
                }
                fq->last_in |= LAST_IN;
                fq->len = end;
        } else {
                /* Check if the fragment is rounded to 8 bytes.
                 * Required by the RFC.
                 */
                if (end & 0x7) {
                        /* RFC2460 says always send parameter problem in
                         * this case. -DaveM
                         */
                        DEBUGP("the end of this fragment is not rounded to 8 bytes.\n");
                        return -1;
                }
                if (end > fq->len) {
                        /* Some bits beyond end -> corruption. */
                        if (fq->last_in & LAST_IN) {
                                DEBUGP("last packet already reached.\n");
                                goto err;
                        }
                        fq->len = end;
                }
        }

        if (end == offset)
                goto err;

        /* Point into the IP datagram 'data' part. */
        if (!pskb_pull(skb, (u8 *) (fhdr + 1) - skb->data)) {
                DEBUGP("queue: message is too short.\n");
                goto err;
        }
        if (end-offset < skb->len) {
                if (pskb_trim(skb, end - offset)) {
                        DEBUGP("Can't trim\n");
                        goto err;
                }
                if (skb->ip_summed != CHECKSUM_UNNECESSARY)
                        skb->ip_summed = CHECKSUM_NONE;
        }

        /* Find out which fragments are in front and at the back of us
         * in the chain of fragments so far.  We must know where to put
         * this fragment, right?
         */
        prev = NULL;
        for (next = fq->fragments; next != NULL; next = next->next) {
                if (NFCT_FRAG6_CB(next)->offset >= offset)
                        break;  /* bingo! */
                prev = next;
        }

        /* We found where to put this one.  Check for overlap with
         * preceding fragment, and, if needed, align things so that
         * any overlaps are eliminated.
         */
        if (prev) {
                int i = (NFCT_FRAG6_CB(prev)->offset + prev->len) - offset;

                if (i > 0) {
                        offset += i;
                        if (end <= offset) {
                                DEBUGP("overlap\n");
                                goto err;
                        }
                        if (!pskb_pull(skb, i)) {
                                DEBUGP("Can't pull\n");
                                goto err;
                        }
                        if (skb->ip_summed != CHECKSUM_UNNECESSARY)
                                skb->ip_summed = CHECKSUM_NONE;
                }
        }

        /* Look for overlap with succeeding segments.
         * If we can merge fragments, do it.
         */
        while (next && NFCT_FRAG6_CB(next)->offset < end) {
                /* overlap is 'i' bytes */
                int i = end - NFCT_FRAG6_CB(next)->offset;

                if (i < next->len) {
                        /* Eat head of the next overlapped fragment
                         * and leave the loop. The next ones cannot overlap.
                         */
                        DEBUGP("Eat head of the overlapped parts.: %d", i);
                        if (!pskb_pull(next, i))
                                goto err;

                        /* next fragment */
                        NFCT_FRAG6_CB(next)->offset += i;
                        fq->meat -= i;
                        if (next->ip_summed != CHECKSUM_UNNECESSARY)
                                next->ip_summed = CHECKSUM_NONE;
                        break;
                } else {
                        struct sk_buff *free_it = next;

                        /* Old fragmnet is completely overridden with
                         * new one drop it.
                         */
                        next = next->next;

                        if (prev)
                                prev->next = next;
                        else
                                fq->fragments = next;

                        fq->meat -= free_it->len;
                        frag_kfree_skb(free_it, NULL);
                }
        }

        NFCT_FRAG6_CB(skb)->offset = offset;

        /* Insert this fragment in the chain of fragments. */
        skb->next = next;
        if (prev)
                prev->next = skb;
        else
                fq->fragments = skb;

        skb->dev = NULL;
        skb_get_timestamp(skb, &fq->stamp);
        fq->meat += skb->len;
        atomic_add(skb->truesize, &nf_ct_frag6_mem);

        /* The first fragment.
         * nhoffset is obtained from the first fragment, of course.
         */
        if (offset == 0) {
                fq->nhoffset = nhoff;
                fq->last_in |= FIRST_IN;
        }
        write_lock(&nf_ct_frag6_lock);
        list_move_tail(&fq->lru_list, &nf_ct_frag6_lru_list);
        write_unlock(&nf_ct_frag6_lock);
        return 0;

err:
        return -1;
}

/*
 *      Check if this packet is complete.
 *      Returns NULL on failure by any reason, and pointer
 *      to current nexthdr field in reassembled frame.
 *
 *      It is called with locked fq, and caller must check that
 *      queue is eligible for reassembly i.e. it is not COMPLETE,
 *      the last and the first frames arrived and all the bits are here.
 */
static struct sk_buff *
nf_ct_frag6_reasm(struct nf_ct_frag6_queue *fq, struct net_device *dev)
{
        struct sk_buff *fp, *op, *head = fq->fragments;
        int    payload_len;

        fq_kill(fq);

        BUG_TRAP(head != NULL);
        BUG_TRAP(NFCT_FRAG6_CB(head)->offset == 0);

        /* Unfragmented part is taken from the first segment. */
        payload_len = (head->data - head->nh.raw) - sizeof(struct ipv6hdr) + fq->len - sizeof(struct frag_hdr);
        if (payload_len > IPV6_MAXPLEN) {
                DEBUGP("payload len is too large.\n");
                goto out_oversize;
        }

        /* Head of list must not be cloned. */
        if (skb_cloned(head) && pskb_expand_head(head, 0, 0, GFP_ATOMIC)) {
                DEBUGP("skb is cloned but can't expand head");
                goto out_oom;
        }

        /* If the first fragment is fragmented itself, we split
         * it to two chunks: the first with data and paged part
         * and the second, holding only fragments. */
        if (skb_shinfo(head)->frag_list) {
                struct sk_buff *clone;
                int i, plen = 0;

                if ((clone = alloc_skb(0, GFP_ATOMIC)) == NULL) {
                        DEBUGP("Can't alloc skb\n");
                        goto out_oom;
                }
                clone->next = head->next;
                head->next = clone;
                skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
                skb_shinfo(head)->frag_list = NULL;
                for (i=0; i<skb_shinfo(head)->nr_frags; i++)
                        plen += skb_shinfo(head)->frags[i].size;
                clone->len = clone->data_len = head->data_len - plen;
                head->data_len -= clone->len;
                head->len -= clone->len;
                clone->csum = 0;
                clone->ip_summed = head->ip_summed;

                NFCT_FRAG6_CB(clone)->orig = NULL;
                atomic_add(clone->truesize, &nf_ct_frag6_mem);
        }

        /* We have to remove fragment header from datagram and to relocate
         * header in order to calculate ICV correctly. */
        head->nh.raw[fq->nhoffset] = head->h.raw[0];
        memmove(head->head + sizeof(struct frag_hdr), head->head, 
                (head->data - head->head) - sizeof(struct frag_hdr));
        head->mac.raw += sizeof(struct frag_hdr);
        head->nh.raw += sizeof(struct frag_hdr);

        skb_shinfo(head)->frag_list = head->next;
        head->h.raw = head->data;
        skb_push(head, head->data - head->nh.raw);
        atomic_sub(head->truesize, &nf_ct_frag6_mem);

        for (fp=head->next; fp; fp = fp->next) {
                head->data_len += fp->len;
                head->len += fp->len;
                if (head->ip_summed != fp->ip_summed)
                        head->ip_summed = CHECKSUM_NONE;
                else if (head->ip_summed == CHECKSUM_HW)
                        head->csum = csum_add(head->csum, fp->csum);
                head->truesize += fp->truesize;
                atomic_sub(fp->truesize, &nf_ct_frag6_mem);
        }

        head->next = NULL;
        head->dev = dev;
        skb_set_timestamp(head, &fq->stamp);
        head->nh.ipv6h->payload_len = htons(payload_len);

        /* Yes, and fold redundant checksum back. 8) */
        if (head->ip_summed == CHECKSUM_HW)
                head->csum = csum_partial(head->nh.raw, head->h.raw-head->nh.raw, head->csum);

        fq->fragments = NULL;

        /* all original skbs are linked into the NFCT_FRAG6_CB(head).orig */
        fp = skb_shinfo(head)->frag_list;
        if (NFCT_FRAG6_CB(fp)->orig == NULL)
                /* at above code, head skb is divided into two skbs. */
                fp = fp->next;

        op = NFCT_FRAG6_CB(head)->orig;
        for (; fp; fp = fp->next) {
                struct sk_buff *orig = NFCT_FRAG6_CB(fp)->orig;

                op->next = orig;
                op = orig;
                NFCT_FRAG6_CB(fp)->orig = NULL;
        }

        return head;

out_oversize:
        if (net_ratelimit())
                printk(KERN_DEBUG "nf_ct_frag6_reasm: payload len = %d\n", payload_len);
        goto out_fail;
out_oom:
        if (net_ratelimit())
                printk(KERN_DEBUG "nf_ct_frag6_reasm: no memory for reassembly\n");
out_fail:
        return NULL;
}

/*
 * find the header just before Fragment Header.
 *
 * if success return 0 and set ...
 * (*prevhdrp): the value of "Next Header Field" in the header
 *              just before Fragment Header.
 * (*prevhoff): the offset of "Next Header Field" in the header
 *              just before Fragment Header.
 * (*fhoff)   : the offset of Fragment Header.
 *
 * Based on ipv6_skip_hdr() in net/ipv6/exthdr.c
 *
 */
static int
find_prev_fhdr(struct sk_buff *skb, u8 *prevhdrp, int *prevhoff, int *fhoff)
{
        u8 nexthdr = skb->nh.ipv6h->nexthdr;
        u8 prev_nhoff = (u8 *)&skb->nh.ipv6h->nexthdr - skb->data;
        int start = (u8 *)(skb->nh.ipv6h+1) - skb->data;
        int len = skb->len - start;
        u8 prevhdr = NEXTHDR_IPV6;

        while (nexthdr != NEXTHDR_FRAGMENT) {
                struct ipv6_opt_hdr hdr;
                int hdrlen;

                if (!ipv6_ext_hdr(nexthdr)) {
                        return -1;
                }
                if (len < (int)sizeof(struct ipv6_opt_hdr)) {
                        DEBUGP("too short\n");
                        return -1;
                }
                if (nexthdr == NEXTHDR_NONE) {
                        DEBUGP("next header is none\n");
                        return -1;
                }
                if (skb_copy_bits(skb, start, &hdr, sizeof(hdr)))
                        BUG();
                if (nexthdr == NEXTHDR_AUTH)
                        hdrlen = (hdr.hdrlen+2)<<2;
                else
                        hdrlen = ipv6_optlen(&hdr);

                prevhdr = nexthdr;
                prev_nhoff = start;

                nexthdr = hdr.nexthdr;
                len -= hdrlen;
                start += hdrlen;
        }

        if (len < 0)
                return -1;

        *prevhdrp = prevhdr;
        *prevhoff = prev_nhoff;
        *fhoff = start;

        return 0;
}

struct sk_buff *nf_ct_frag6_gather(struct sk_buff *skb)
{
        struct sk_buff *clone; 
        struct net_device *dev = skb->dev;
        struct frag_hdr *fhdr;
        struct nf_ct_frag6_queue *fq;
        struct ipv6hdr *hdr;
        int fhoff, nhoff;
        u8 prevhdr;
        struct sk_buff *ret_skb = NULL;

        /* Jumbo payload inhibits frag. header */
        if (skb->nh.ipv6h->payload_len == 0) {
                DEBUGP("payload len = 0\n");
                return skb;
        }

        if (find_prev_fhdr(skb, &prevhdr, &nhoff, &fhoff) < 0)
                return skb;

        clone = skb_clone(skb, GFP_ATOMIC);
        if (clone == NULL) {
                DEBUGP("Can't clone skb\n");
                return skb;
        }

        NFCT_FRAG6_CB(clone)->orig = skb;

        if (!pskb_may_pull(clone, fhoff + sizeof(*fhdr))) {
                DEBUGP("message is too short.\n");
                goto ret_orig;
        }

        clone->h.raw = clone->data + fhoff;
        hdr = clone->nh.ipv6h;
        fhdr = (struct frag_hdr *)clone->h.raw;

        if (!(fhdr->frag_off & htons(0xFFF9))) {
                DEBUGP("Invalid fragment offset\n");
                /* It is not a fragmented frame */
                goto ret_orig;
        }

        if (atomic_read(&nf_ct_frag6_mem) > nf_ct_frag6_high_thresh)
                nf_ct_frag6_evictor();

        fq = fq_find(fhdr->identification, &hdr->saddr, &hdr->daddr);
        if (fq == NULL) {
                DEBUGP("Can't find and can't create new queue\n");
                goto ret_orig;
        }

        spin_lock(&fq->lock);

        if (nf_ct_frag6_queue(fq, clone, fhdr, nhoff) < 0) {
                spin_unlock(&fq->lock);
                DEBUGP("Can't insert skb to queue\n");
                fq_put(fq, NULL);
                goto ret_orig;
        }

        if (fq->last_in == (FIRST_IN|LAST_IN) && fq->meat == fq->len) {
                ret_skb = nf_ct_frag6_reasm(fq, dev);
                if (ret_skb == NULL)
                        DEBUGP("Can't reassemble fragmented packets\n");
        }
        spin_unlock(&fq->lock);

        fq_put(fq, NULL);
        return ret_skb;

ret_orig:
        kfree_skb(clone);
        return skb;
}

void nf_ct_frag6_output(unsigned int hooknum, struct sk_buff *skb,
                        struct net_device *in, struct net_device *out,
                        int (*okfn)(struct sk_buff *))
{
        struct sk_buff *s, *s2;

        for (s = NFCT_FRAG6_CB(skb)->orig; s;) {
                nf_conntrack_put_reasm(s->nfct_reasm);
                nf_conntrack_get_reasm(skb);
                s->nfct_reasm = skb;

                s2 = s->next;
                NF_HOOK_THRESH(PF_INET6, hooknum, s, in, out, okfn,
                               NF_IP6_PRI_CONNTRACK_DEFRAG + 1);
                s = s2;
        }
        nf_conntrack_put_reasm(skb);
}

int nf_ct_frag6_kfree_frags(struct sk_buff *skb)
{
        struct sk_buff *s, *s2;

        for (s = NFCT_FRAG6_CB(skb)->orig; s; s = s2) {

                s2 = s->next;
                kfree_skb(s);
        }

        kfree_skb(skb);

        return 0;
}

int nf_ct_frag6_init(void)
{
        nf_ct_frag6_hash_rnd = (u32) ((num_physpages ^ (num_physpages>>7)) ^
                                   (jiffies ^ (jiffies >> 6)));

        init_timer(&nf_ct_frag6_secret_timer);
        nf_ct_frag6_secret_timer.function = nf_ct_frag6_secret_rebuild;
        nf_ct_frag6_secret_timer.expires = jiffies
                                           + nf_ct_frag6_secret_interval;
        add_timer(&nf_ct_frag6_secret_timer);

        return 0;
}

void nf_ct_frag6_cleanup(void)
{
        del_timer(&nf_ct_frag6_secret_timer);
        nf_ct_frag6_low_thresh = 0;
        nf_ct_frag6_evictor();
}