netfilter: xtables: optimize call flow around xt_ematch_foreach

[safe/jmp/linux-2.6] / net / ipv6 / netfilter / ip6_tables.c

/*
 * Packet matching code.
 *
 * Copyright (C) 1999 Paul `Rusty' Russell & Michael J. Neuling
 * Copyright (C) 2000-2005 Netfilter Core Team <coreteam@netfilter.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/capability.h>
#include <linux/in.h>
#include <linux/skbuff.h>
#include <linux/kmod.h>
#include <linux/vmalloc.h>
#include <linux/netdevice.h>
#include <linux/module.h>
#include <linux/poison.h>
#include <linux/icmpv6.h>
#include <net/ipv6.h>
#include <net/compat.h>
#include <asm/uaccess.h>
#include <linux/mutex.h>
#include <linux/proc_fs.h>
#include <linux/err.h>
#include <linux/cpumask.h>

#include <linux/netfilter_ipv6/ip6_tables.h>
#include <linux/netfilter/x_tables.h>
#include <net/netfilter/nf_log.h>
#include "../../netfilter/xt_repldata.h"

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
MODULE_DESCRIPTION("IPv6 packet filter");

/*#define DEBUG_IP_FIREWALL*/
/*#define DEBUG_ALLOW_ALL*/ /* Useful for remote debugging */
/*#define DEBUG_IP_FIREWALL_USER*/

#ifdef DEBUG_IP_FIREWALL
#define dprintf(format, args...)  printk(format , ## args)
#else
#define dprintf(format, args...)
#endif

#ifdef DEBUG_IP_FIREWALL_USER
#define duprintf(format, args...) printk(format , ## args)
#else
#define duprintf(format, args...)
#endif

#ifdef CONFIG_NETFILTER_DEBUG
#define IP_NF_ASSERT(x)                                         \
do {                                                            \
        if (!(x))                                               \
                printk("IP_NF_ASSERT: %s:%s:%u\n",              \
                       __func__, __FILE__, __LINE__);   \
} while(0)
#else
#define IP_NF_ASSERT(x)
#endif

#if 0
/* All the better to debug you with... */
#define static
#define inline
#endif

void *ip6t_alloc_initial_table(const struct xt_table *info)
{
        return xt_alloc_initial_table(ip6t, IP6T);
}
EXPORT_SYMBOL_GPL(ip6t_alloc_initial_table);

/*
   We keep a set of rules for each CPU, so we can avoid write-locking
   them in the softirq when updating the counters and therefore
   only need to read-lock in the softirq; doing a write_lock_bh() in user
   context stops packets coming through and allows user context to read
   the counters or update the rules.

   Hence the start of any table is given by get_table() below.  */

/* Check for an extension */
int
ip6t_ext_hdr(u8 nexthdr)
{
        return ( (nexthdr == IPPROTO_HOPOPTS)   ||
                 (nexthdr == IPPROTO_ROUTING)   ||
                 (nexthdr == IPPROTO_FRAGMENT)  ||
                 (nexthdr == IPPROTO_ESP)       ||
                 (nexthdr == IPPROTO_AH)        ||
                 (nexthdr == IPPROTO_NONE)      ||
                 (nexthdr == IPPROTO_DSTOPTS) );
}

/* Returns whether matches rule or not. */
/* Performance critical - called for every packet */
static inline bool
ip6_packet_match(const struct sk_buff *skb,
                 const char *indev,
                 const char *outdev,
                 const struct ip6t_ip6 *ip6info,
                 unsigned int *protoff,
                 int *fragoff, bool *hotdrop)
{
        unsigned long ret;
        const struct ipv6hdr *ipv6 = ipv6_hdr(skb);

#define FWINV(bool, invflg) ((bool) ^ !!(ip6info->invflags & (invflg)))

        if (FWINV(ipv6_masked_addr_cmp(&ipv6->saddr, &ip6info->smsk,
                                       &ip6info->src), IP6T_INV_SRCIP) ||
            FWINV(ipv6_masked_addr_cmp(&ipv6->daddr, &ip6info->dmsk,
                                       &ip6info->dst), IP6T_INV_DSTIP)) {
                dprintf("Source or dest mismatch.\n");
/*
                dprintf("SRC: %u. Mask: %u. Target: %u.%s\n", ip->saddr,
                        ipinfo->smsk.s_addr, ipinfo->src.s_addr,
                        ipinfo->invflags & IP6T_INV_SRCIP ? " (INV)" : "");
                dprintf("DST: %u. Mask: %u. Target: %u.%s\n", ip->daddr,
                        ipinfo->dmsk.s_addr, ipinfo->dst.s_addr,
                        ipinfo->invflags & IP6T_INV_DSTIP ? " (INV)" : "");*/
                return false;
        }

        ret = ifname_compare_aligned(indev, ip6info->iniface, ip6info->iniface_mask);

        if (FWINV(ret != 0, IP6T_INV_VIA_IN)) {
                dprintf("VIA in mismatch (%s vs %s).%s\n",
                        indev, ip6info->iniface,
                        ip6info->invflags&IP6T_INV_VIA_IN ?" (INV)":"");
                return false;
        }

        ret = ifname_compare_aligned(outdev, ip6info->outiface, ip6info->outiface_mask);

        if (FWINV(ret != 0, IP6T_INV_VIA_OUT)) {
                dprintf("VIA out mismatch (%s vs %s).%s\n",
                        outdev, ip6info->outiface,
                        ip6info->invflags&IP6T_INV_VIA_OUT ?" (INV)":"");
                return false;
        }

/* ... might want to do something with class and flowlabel here ... */

        /* look for the desired protocol header */
        if((ip6info->flags & IP6T_F_PROTO)) {
                int protohdr;
                unsigned short _frag_off;

                protohdr = ipv6_find_hdr(skb, protoff, -1, &_frag_off);
                if (protohdr < 0) {
                        if (_frag_off == 0)
                                *hotdrop = true;
                        return false;
                }
                *fragoff = _frag_off;

                dprintf("Packet protocol %hi ?= %s%hi.\n",
                                protohdr,
                                ip6info->invflags & IP6T_INV_PROTO ? "!":"",
                                ip6info->proto);

                if (ip6info->proto == protohdr) {
                        if(ip6info->invflags & IP6T_INV_PROTO) {
                                return false;
                        }
                        return true;
                }

                /* We need match for the '-p all', too! */
                if ((ip6info->proto != 0) &&
                        !(ip6info->invflags & IP6T_INV_PROTO))
                        return false;
        }
        return true;
}

/* should be ip6 safe */
static bool
ip6_checkentry(const struct ip6t_ip6 *ipv6)
{
        if (ipv6->flags & ~IP6T_F_MASK) {
                duprintf("Unknown flag bits set: %08X\n",
                         ipv6->flags & ~IP6T_F_MASK);
                return false;
        }
        if (ipv6->invflags & ~IP6T_INV_MASK) {
                duprintf("Unknown invflag bits set: %08X\n",
                         ipv6->invflags & ~IP6T_INV_MASK);
                return false;
        }
        return true;
}

static unsigned int
ip6t_error(struct sk_buff *skb, const struct xt_target_param *par)
{
        if (net_ratelimit())
                printk("ip6_tables: error: `%s'\n",
                       (const char *)par->targinfo);

        return NF_DROP;
}

/* Performance critical - called for every packet */
static inline bool
do_match(const struct ip6t_entry_match *m, const struct sk_buff *skb,
         struct xt_match_param *par)
{
        par->match     = m->u.kernel.match;
        par->matchinfo = m->data;

        /* Stop iteration if it doesn't match */
        if (!m->u.kernel.match->match(skb, par))
                return true;
        else
                return false;
}

static inline struct ip6t_entry *
get_entry(const void *base, unsigned int offset)
{
        return (struct ip6t_entry *)(base + offset);
}

/* All zeroes == unconditional rule. */
/* Mildly perf critical (only if packet tracing is on) */
static inline bool unconditional(const struct ip6t_ip6 *ipv6)
{
        static const struct ip6t_ip6 uncond;

        return memcmp(ipv6, &uncond, sizeof(uncond)) == 0;
}

static inline const struct ip6t_entry_target *
ip6t_get_target_c(const struct ip6t_entry *e)
{
        return ip6t_get_target((struct ip6t_entry *)e);
}

#if defined(CONFIG_NETFILTER_XT_TARGET_TRACE) || \
    defined(CONFIG_NETFILTER_XT_TARGET_TRACE_MODULE)
/* This cries for unification! */
static const char *const hooknames[] = {
        [NF_INET_PRE_ROUTING]           = "PREROUTING",
        [NF_INET_LOCAL_IN]              = "INPUT",
        [NF_INET_FORWARD]               = "FORWARD",
        [NF_INET_LOCAL_OUT]             = "OUTPUT",
        [NF_INET_POST_ROUTING]          = "POSTROUTING",
};

enum nf_ip_trace_comments {
        NF_IP6_TRACE_COMMENT_RULE,
        NF_IP6_TRACE_COMMENT_RETURN,
        NF_IP6_TRACE_COMMENT_POLICY,
};

static const char *const comments[] = {
        [NF_IP6_TRACE_COMMENT_RULE]     = "rule",
        [NF_IP6_TRACE_COMMENT_RETURN]   = "return",
        [NF_IP6_TRACE_COMMENT_POLICY]   = "policy",
};

static struct nf_loginfo trace_loginfo = {
        .type = NF_LOG_TYPE_LOG,
        .u = {
                .log = {
                        .level = 4,
                        .logflags = NF_LOG_MASK,
                },
        },
};

/* Mildly perf critical (only if packet tracing is on) */
static inline int
get_chainname_rulenum(const struct ip6t_entry *s, const struct ip6t_entry *e,
                      const char *hookname, const char **chainname,
                      const char **comment, unsigned int *rulenum)
{
        const struct ip6t_standard_target *t = (void *)ip6t_get_target_c(s);

        if (strcmp(t->target.u.kernel.target->name, IP6T_ERROR_TARGET) == 0) {
                /* Head of user chain: ERROR target with chainname */
                *chainname = t->target.data;
                (*rulenum) = 0;
        } else if (s == e) {
                (*rulenum)++;

                if (s->target_offset == sizeof(struct ip6t_entry) &&
                    strcmp(t->target.u.kernel.target->name,
                           IP6T_STANDARD_TARGET) == 0 &&
                    t->verdict < 0 &&
                    unconditional(&s->ipv6)) {
                        /* Tail of chains: STANDARD target (return/policy) */
                        *comment = *chainname == hookname
                                ? comments[NF_IP6_TRACE_COMMENT_POLICY]
                                : comments[NF_IP6_TRACE_COMMENT_RETURN];
                }
                return 1;
        } else
                (*rulenum)++;

        return 0;
}

static void trace_packet(const struct sk_buff *skb,
                         unsigned int hook,
                         const struct net_device *in,
                         const struct net_device *out,
                         const char *tablename,
                         const struct xt_table_info *private,
                         const struct ip6t_entry *e)
{
        const void *table_base;
        const struct ip6t_entry *root;
        const char *hookname, *chainname, *comment;
        const struct ip6t_entry *iter;
        unsigned int rulenum = 0;

        table_base = private->entries[smp_processor_id()];
        root = get_entry(table_base, private->hook_entry[hook]);

        hookname = chainname = hooknames[hook];
        comment = comments[NF_IP6_TRACE_COMMENT_RULE];

        xt_entry_foreach(iter, root, private->size - private->hook_entry[hook])
                if (get_chainname_rulenum(iter, e, hookname,
                    &chainname, &comment, &rulenum) != 0)
                        break;

        nf_log_packet(AF_INET6, hook, skb, in, out, &trace_loginfo,
                      "TRACE: %s:%s:%s:%u ",
                      tablename, chainname, comment, rulenum);
}
#endif

static inline __pure struct ip6t_entry *
ip6t_next_entry(const struct ip6t_entry *entry)
{
        return (void *)entry + entry->next_offset;
}

/* Returns one of the generic firewall policies, like NF_ACCEPT. */
unsigned int
ip6t_do_table(struct sk_buff *skb,
              unsigned int hook,
              const struct net_device *in,
              const struct net_device *out,
              struct xt_table *table)
{
#define tb_comefrom ((struct ip6t_entry *)table_base)->comefrom

        static const char nulldevname[IFNAMSIZ] __attribute__((aligned(sizeof(long))));
        bool hotdrop = false;
        /* Initializing verdict to NF_DROP keeps gcc happy. */
        unsigned int verdict = NF_DROP;
        const char *indev, *outdev;
        const void *table_base;
        struct ip6t_entry *e, *back;
        const struct xt_table_info *private;
        struct xt_match_param mtpar;
        struct xt_target_param tgpar;

        /* Initialization */
        indev = in ? in->name : nulldevname;
        outdev = out ? out->name : nulldevname;
        /* We handle fragments by dealing with the first fragment as
         * if it was a normal packet.  All other fragments are treated
         * normally, except that they will NEVER match rules that ask
         * things we don't know, ie. tcp syn flag or ports).  If the
         * rule is also a fragment-specific rule, non-fragments won't
         * match it. */
        mtpar.hotdrop = &hotdrop;
        mtpar.in      = tgpar.in  = in;
        mtpar.out     = tgpar.out = out;
        mtpar.family  = tgpar.family = NFPROTO_IPV6;
        mtpar.hooknum = tgpar.hooknum = hook;

        IP_NF_ASSERT(table->valid_hooks & (1 << hook));

        xt_info_rdlock_bh();
        private = table->private;
        table_base = private->entries[smp_processor_id()];

        e = get_entry(table_base, private->hook_entry[hook]);

        /* For return from builtin chain */
        back = get_entry(table_base, private->underflow[hook]);

        do {
                const struct ip6t_entry_target *t;
                const struct xt_entry_match *ematch;

                IP_NF_ASSERT(e);
                IP_NF_ASSERT(back);
                if (!ip6_packet_match(skb, indev, outdev, &e->ipv6,
                    &mtpar.thoff, &mtpar.fragoff, &hotdrop)) {
 no_match:
                        e = ip6t_next_entry(e);
                        continue;
                }

                xt_ematch_foreach(ematch, e)
                        if (do_match(ematch, skb, &mtpar) != 0)
                                goto no_match;

                ADD_COUNTER(e->counters,
                            ntohs(ipv6_hdr(skb)->payload_len) +
                            sizeof(struct ipv6hdr), 1);

                t = ip6t_get_target_c(e);
                IP_NF_ASSERT(t->u.kernel.target);

#if defined(CONFIG_NETFILTER_XT_TARGET_TRACE) || \
    defined(CONFIG_NETFILTER_XT_TARGET_TRACE_MODULE)
                /* The packet is traced: log it */
                if (unlikely(skb->nf_trace))
                        trace_packet(skb, hook, in, out,
                                     table->name, private, e);
#endif
                /* Standard target? */
                if (!t->u.kernel.target->target) {
                        int v;

                        v = ((struct ip6t_standard_target *)t)->verdict;
                        if (v < 0) {
                                /* Pop from stack? */
                                if (v != IP6T_RETURN) {
                                        verdict = (unsigned)(-v) - 1;
                                        break;
                                }
                                e = back;
                                back = get_entry(table_base, back->comefrom);
                                continue;
                        }
                        if (table_base + v != ip6t_next_entry(e) &&
                            !(e->ipv6.flags & IP6T_F_GOTO)) {
                                /* Save old back ptr in next entry */
                                struct ip6t_entry *next = ip6t_next_entry(e);
                                next->comefrom = (void *)back - table_base;
                                /* set back pointer to next entry */
                                back = next;
                        }

                        e = get_entry(table_base, v);
                        continue;
                }

                /* Targets which reenter must return
                   abs. verdicts */
                tgpar.target   = t->u.kernel.target;
                tgpar.targinfo = t->data;

#ifdef CONFIG_NETFILTER_DEBUG
                tb_comefrom = 0xeeeeeeec;
#endif
                verdict = t->u.kernel.target->target(skb, &tgpar);

#ifdef CONFIG_NETFILTER_DEBUG
                if (tb_comefrom != 0xeeeeeeec && verdict == IP6T_CONTINUE) {
                        printk("Target %s reentered!\n",
                               t->u.kernel.target->name);
                        verdict = NF_DROP;
                }
                tb_comefrom = 0x57acc001;
#endif
                if (verdict == IP6T_CONTINUE)
                        e = ip6t_next_entry(e);
                else
                        /* Verdict */
                        break;
        } while (!hotdrop);

#ifdef CONFIG_NETFILTER_DEBUG
        tb_comefrom = NETFILTER_LINK_POISON;
#endif
        xt_info_rdunlock_bh();

#ifdef DEBUG_ALLOW_ALL
        return NF_ACCEPT;
#else
        if (hotdrop)
                return NF_DROP;
        else return verdict;
#endif

#undef tb_comefrom
}

/* Figures out from what hook each rule can be called: returns 0 if
   there are loops.  Puts hook bitmask in comefrom. */
static int
mark_source_chains(const struct xt_table_info *newinfo,
                   unsigned int valid_hooks, void *entry0)
{
        unsigned int hook;

        /* No recursion; use packet counter to save back ptrs (reset
           to 0 as we leave), and comefrom to save source hook bitmask */
        for (hook = 0; hook < NF_INET_NUMHOOKS; hook++) {
                unsigned int pos = newinfo->hook_entry[hook];
                struct ip6t_entry *e = (struct ip6t_entry *)(entry0 + pos);

                if (!(valid_hooks & (1 << hook)))
                        continue;

                /* Set initial back pointer. */
                e->counters.pcnt = pos;

                for (;;) {
                        const struct ip6t_standard_target *t
                                = (void *)ip6t_get_target_c(e);
                        int visited = e->comefrom & (1 << hook);

                        if (e->comefrom & (1 << NF_INET_NUMHOOKS)) {
                                printk("iptables: loop hook %u pos %u %08X.\n",
                                       hook, pos, e->comefrom);
                                return 0;
                        }
                        e->comefrom |= ((1 << hook) | (1 << NF_INET_NUMHOOKS));

                        /* Unconditional return/END. */
                        if ((e->target_offset == sizeof(struct ip6t_entry) &&
                             (strcmp(t->target.u.user.name,
                                     IP6T_STANDARD_TARGET) == 0) &&
                             t->verdict < 0 &&
                             unconditional(&e->ipv6)) || visited) {
                                unsigned int oldpos, size;

                                if ((strcmp(t->target.u.user.name,
                                            IP6T_STANDARD_TARGET) == 0) &&
                                    t->verdict < -NF_MAX_VERDICT - 1) {
                                        duprintf("mark_source_chains: bad "
                                                "negative verdict (%i)\n",
                                                                t->verdict);
                                        return 0;
                                }

                                /* Return: backtrack through the last
                                   big jump. */
                                do {
                                        e->comefrom ^= (1<<NF_INET_NUMHOOKS);
#ifdef DEBUG_IP_FIREWALL_USER
                                        if (e->comefrom
                                            & (1 << NF_INET_NUMHOOKS)) {
                                                duprintf("Back unset "
                                                         "on hook %u "
                                                         "rule %u\n",
                                                         hook, pos);
                                        }
#endif
                                        oldpos = pos;
                                        pos = e->counters.pcnt;
                                        e->counters.pcnt = 0;

                                        /* We're at the start. */
                                        if (pos == oldpos)
                                                goto next;

                                        e = (struct ip6t_entry *)
                                                (entry0 + pos);
                                } while (oldpos == pos + e->next_offset);

                                /* Move along one */
                                size = e->next_offset;
                                e = (struct ip6t_entry *)
                                        (entry0 + pos + size);
                                e->counters.pcnt = pos;
                                pos += size;
                        } else {
                                int newpos = t->verdict;

                                if (strcmp(t->target.u.user.name,
                                           IP6T_STANDARD_TARGET) == 0 &&
                                    newpos >= 0) {
                                        if (newpos > newinfo->size -
                                                sizeof(struct ip6t_entry)) {
                                                duprintf("mark_source_chains: "
                                                        "bad verdict (%i)\n",
                                                                newpos);
                                                return 0;
                                        }
                                        /* This a jump; chase it. */
                                        duprintf("Jump rule %u -> %u\n",
                                                 pos, newpos);
                                } else {
                                        /* ... this is a fallthru */
                                        newpos = pos + e->next_offset;
                                }
                                e = (struct ip6t_entry *)
                                        (entry0 + newpos);
                                e->counters.pcnt = pos;
                                pos = newpos;
                        }
                }
                next:
                duprintf("Finished chain %u\n", hook);
        }
        return 1;
}

static void cleanup_match(struct ip6t_entry_match *m, struct net *net)
{
        struct xt_mtdtor_param par;

        par.net       = net;
        par.match     = m->u.kernel.match;
        par.matchinfo = m->data;
        par.family    = NFPROTO_IPV6;
        if (par.match->destroy != NULL)
                par.match->destroy(&par);
        module_put(par.match->me);
}

static int
check_entry(const struct ip6t_entry *e, const char *name)
{
        const struct ip6t_entry_target *t;

        if (!ip6_checkentry(&e->ipv6)) {
                duprintf("ip_tables: ip check failed %p %s.\n", e, name);
                return -EINVAL;
        }

        if (e->target_offset + sizeof(struct ip6t_entry_target) >
            e->next_offset)
                return -EINVAL;

        t = ip6t_get_target_c(e);
        if (e->target_offset + t->u.target_size > e->next_offset)
                return -EINVAL;

        return 0;
}

static int check_match(struct ip6t_entry_match *m, struct xt_mtchk_param *par)
{
        const struct ip6t_ip6 *ipv6 = par->entryinfo;
        int ret;

        par->match     = m->u.kernel.match;
        par->matchinfo = m->data;

        ret = xt_check_match(par, m->u.match_size - sizeof(*m),
                             ipv6->proto, ipv6->invflags & IP6T_INV_PROTO);
        if (ret < 0) {
                duprintf("ip_tables: check failed for `%s'.\n",
                         par.match->name);
                return ret;
        }
        return 0;
}

static int
find_check_match(struct ip6t_entry_match *m, struct xt_mtchk_param *par)
{
        struct xt_match *match;
        int ret;

        match = try_then_request_module(xt_find_match(AF_INET6, m->u.user.name,
                                                      m->u.user.revision),
                                        "ip6t_%s", m->u.user.name);
        if (IS_ERR(match) || !match) {
                duprintf("find_check_match: `%s' not found\n", m->u.user.name);
                return match ? PTR_ERR(match) : -ENOENT;
        }
        m->u.kernel.match = match;

        ret = check_match(m, par);
        if (ret)
                goto err;

        return 0;
err:
        module_put(m->u.kernel.match->me);
        return ret;
}

static int check_target(struct ip6t_entry *e, struct net *net, const char *name)
{
        struct ip6t_entry_target *t = ip6t_get_target(e);
        struct xt_tgchk_param par = {
                .net       = net,
                .table     = name,
                .entryinfo = e,
                .target    = t->u.kernel.target,
                .targinfo  = t->data,
                .hook_mask = e->comefrom,
                .family    = NFPROTO_IPV6,
        };
        int ret;

        t = ip6t_get_target(e);
        ret = xt_check_target(&par, t->u.target_size - sizeof(*t),
              e->ipv6.proto, e->ipv6.invflags & IP6T_INV_PROTO);
        if (ret < 0) {
                duprintf("ip_tables: check failed for `%s'.\n",
                         t->u.kernel.target->name);
                return ret;
        }
        return 0;
}

static int
find_check_entry(struct ip6t_entry *e, struct net *net, const char *name,
                 unsigned int size)
{
        struct ip6t_entry_target *t;
        struct xt_target *target;
        int ret;
        unsigned int j;
        struct xt_mtchk_param mtpar;
        struct xt_entry_match *ematch;

        ret = check_entry(e, name);
        if (ret)
                return ret;

        j = 0;
        mtpar.net       = net;
        mtpar.table     = name;
        mtpar.entryinfo = &e->ipv6;
        mtpar.hook_mask = e->comefrom;
        mtpar.family    = NFPROTO_IPV6;
        xt_ematch_foreach(ematch, e) {
                ret = find_check_match(ematch, &mtpar);
                if (ret != 0)
                        goto cleanup_matches;
                ++j;
        }

        t = ip6t_get_target(e);
        target = try_then_request_module(xt_find_target(AF_INET6,
                                                        t->u.user.name,
                                                        t->u.user.revision),
                                         "ip6t_%s", t->u.user.name);
        if (IS_ERR(target) || !target) {
                duprintf("find_check_entry: `%s' not found\n", t->u.user.name);
                ret = target ? PTR_ERR(target) : -ENOENT;
                goto cleanup_matches;
        }
        t->u.kernel.target = target;

        ret = check_target(e, net, name);
        if (ret)
                goto err;
        return 0;
 err:
        module_put(t->u.kernel.target->me);
 cleanup_matches:
        xt_ematch_foreach(ematch, e) {
                if (j-- == 0)
                        break;
                cleanup_match(ematch, net);
        }
        return ret;
}

static bool check_underflow(const struct ip6t_entry *e)
{
        const struct ip6t_entry_target *t;
        unsigned int verdict;

        if (!unconditional(&e->ipv6))
                return false;
        t = ip6t_get_target_c(e);
        if (strcmp(t->u.user.name, XT_STANDARD_TARGET) != 0)
                return false;
        verdict = ((struct ip6t_standard_target *)t)->verdict;
        verdict = -verdict - 1;
        return verdict == NF_DROP || verdict == NF_ACCEPT;
}

static int
check_entry_size_and_hooks(struct ip6t_entry *e,
                           struct xt_table_info *newinfo,
                           const unsigned char *base,
                           const unsigned char *limit,
                           const unsigned int *hook_entries,
                           const unsigned int *underflows,
                           unsigned int valid_hooks)
{
        unsigned int h;

        if ((unsigned long)e % __alignof__(struct ip6t_entry) != 0 ||
            (unsigned char *)e + sizeof(struct ip6t_entry) >= limit) {
                duprintf("Bad offset %p\n", e);
                return -EINVAL;
        }

        if (e->next_offset
            < sizeof(struct ip6t_entry) + sizeof(struct ip6t_entry_target)) {
                duprintf("checking: element %p size %u\n",
                         e, e->next_offset);
                return -EINVAL;
        }

        /* Check hooks & underflows */
        for (h = 0; h < NF_INET_NUMHOOKS; h++) {
                if (!(valid_hooks & (1 << h)))
                        continue;
                if ((unsigned char *)e - base == hook_entries[h])
                        newinfo->hook_entry[h] = hook_entries[h];
                if ((unsigned char *)e - base == underflows[h]) {
                        if (!check_underflow(e)) {
                                pr_err("Underflows must be unconditional and "
                                       "use the STANDARD target with "
                                       "ACCEPT/DROP\n");
                                return -EINVAL;
                        }
                        newinfo->underflow[h] = underflows[h];
                }
        }

        /* Clear counters and comefrom */
        e->counters = ((struct xt_counters) { 0, 0 });
        e->comefrom = 0;
        return 0;
}

static void cleanup_entry(struct ip6t_entry *e, struct net *net)
{
        struct xt_tgdtor_param par;
        struct ip6t_entry_target *t;
        struct xt_entry_match *ematch;

        /* Cleanup all matches */
        xt_ematch_foreach(ematch, e)
                cleanup_match(ematch, net);
        t = ip6t_get_target(e);

        par.net      = net;
        par.target   = t->u.kernel.target;
        par.targinfo = t->data;
        par.family   = NFPROTO_IPV6;
        if (par.target->destroy != NULL)
                par.target->destroy(&par);
        module_put(par.target->me);
}

/* Checks and translates the user-supplied table segment (held in
   newinfo) */
static int
translate_table(struct net *net,
                const char *name,
                unsigned int valid_hooks,
                struct xt_table_info *newinfo,
                void *entry0,
                unsigned int size,
                unsigned int number,
                const unsigned int *hook_entries,
                const unsigned int *underflows)
{
        struct ip6t_entry *iter;
        unsigned int i;
        int ret = 0;

        newinfo->size = size;
        newinfo->number = number;

        /* Init all hooks to impossible value. */
        for (i = 0; i < NF_INET_NUMHOOKS; i++) {
                newinfo->hook_entry[i] = 0xFFFFFFFF;
                newinfo->underflow[i] = 0xFFFFFFFF;
        }

        duprintf("translate_table: size %u\n", newinfo->size);
        i = 0;
        /* Walk through entries, checking offsets. */
        xt_entry_foreach(iter, entry0, newinfo->size) {
                ret = check_entry_size_and_hooks(iter, newinfo, entry0,
                      entry0 + size, hook_entries, underflows, valid_hooks);
                if (ret != 0)
                        return ret;
                ++i;
        }

        if (i != number) {
                duprintf("translate_table: %u not %u entries\n",
                         i, number);
                return -EINVAL;
        }

        /* Check hooks all assigned */
        for (i = 0; i < NF_INET_NUMHOOKS; i++) {
                /* Only hooks which are valid */
                if (!(valid_hooks & (1 << i)))
                        continue;
                if (newinfo->hook_entry[i] == 0xFFFFFFFF) {
                        duprintf("Invalid hook entry %u %u\n",
                                 i, hook_entries[i]);
                        return -EINVAL;
                }
                if (newinfo->underflow[i] == 0xFFFFFFFF) {
                        duprintf("Invalid underflow %u %u\n",
                                 i, underflows[i]);
                        return -EINVAL;
                }
        }

        if (!mark_source_chains(newinfo, valid_hooks, entry0))
                return -ELOOP;

        /* Finally, each sanity check must pass */
        i = 0;
        xt_entry_foreach(iter, entry0, newinfo->size) {
                ret = find_check_entry(iter, net, name, size);
                if (ret != 0)
                        break;
                ++i;
        }

        if (ret != 0) {
                xt_entry_foreach(iter, entry0, newinfo->size) {
                        if (i-- == 0)
                                break;
                        cleanup_entry(iter, net);
                }
                return ret;
        }

        /* And one copy for every other CPU */
        for_each_possible_cpu(i) {
                if (newinfo->entries[i] && newinfo->entries[i] != entry0)
                        memcpy(newinfo->entries[i], entry0, newinfo->size);
        }

        return ret;
}

static void
get_counters(const struct xt_table_info *t,
             struct xt_counters counters[])
{
        struct ip6t_entry *iter;
        unsigned int cpu;
        unsigned int i;
        unsigned int curcpu;

        /* Instead of clearing (by a previous call to memset())
         * the counters and using adds, we set the counters
         * with data used by 'current' CPU
         *
         * Bottom half has to be disabled to prevent deadlock
         * if new softirq were to run and call ipt_do_table
         */
        local_bh_disable();
        curcpu = smp_processor_id();

        i = 0;
        xt_entry_foreach(iter, t->entries[curcpu], t->size) {
                SET_COUNTER(counters[i], iter->counters.bcnt,
                        iter->counters.pcnt);
                ++i;
        }

        for_each_possible_cpu(cpu) {
                if (cpu == curcpu)
                        continue;
                i = 0;
                xt_info_wrlock(cpu);
                xt_entry_foreach(iter, t->entries[cpu], t->size) {
                        ADD_COUNTER(counters[i], iter->counters.bcnt,
                                iter->counters.pcnt);
                        ++i;
                }
                xt_info_wrunlock(cpu);
        }
        local_bh_enable();
}

static struct xt_counters *alloc_counters(const struct xt_table *table)
{
        unsigned int countersize;
        struct xt_counters *counters;
        const struct xt_table_info *private = table->private;

        /* We need atomic snapshot of counters: rest doesn't change
           (other than comefrom, which userspace doesn't care
           about). */
        countersize = sizeof(struct xt_counters) * private->number;
        counters = vmalloc_node(countersize, numa_node_id());

        if (counters == NULL)
                return ERR_PTR(-ENOMEM);

        get_counters(private, counters);

        return counters;
}

static int
copy_entries_to_user(unsigned int total_size,
                     const struct xt_table *table,
                     void __user *userptr)
{
        unsigned int off, num;
        const struct ip6t_entry *e;
        struct xt_counters *counters;
        const struct xt_table_info *private = table->private;
        int ret = 0;
        const void *loc_cpu_entry;

        counters = alloc_counters(table);
        if (IS_ERR(counters))
                return PTR_ERR(counters);

        /* choose the copy that is on our node/cpu, ...
         * This choice is lazy (because current thread is
         * allowed to migrate to another cpu)
         */
        loc_cpu_entry = private->entries[raw_smp_processor_id()];
        if (copy_to_user(userptr, loc_cpu_entry, total_size) != 0) {
                ret = -EFAULT;
                goto free_counters;
        }

        /* FIXME: use iterator macros --RR */
        /* ... then go back and fix counters and names */
        for (off = 0, num = 0; off < total_size; off += e->next_offset, num++){
                unsigned int i;
                const struct ip6t_entry_match *m;
                const struct ip6t_entry_target *t;

                e = (struct ip6t_entry *)(loc_cpu_entry + off);
                if (copy_to_user(userptr + off
                                 + offsetof(struct ip6t_entry, counters),
                                 &counters[num],
                                 sizeof(counters[num])) != 0) {
                        ret = -EFAULT;
                        goto free_counters;
                }

                for (i = sizeof(struct ip6t_entry);
                     i < e->target_offset;
                     i += m->u.match_size) {
                        m = (void *)e + i;

                        if (copy_to_user(userptr + off + i
                                         + offsetof(struct ip6t_entry_match,
                                                    u.user.name),
                                         m->u.kernel.match->name,
                                         strlen(m->u.kernel.match->name)+1)
                            != 0) {
                                ret = -EFAULT;
                                goto free_counters;
                        }
                }

                t = ip6t_get_target_c(e);
                if (copy_to_user(userptr + off + e->target_offset
                                 + offsetof(struct ip6t_entry_target,
                                            u.user.name),
                                 t->u.kernel.target->name,
                                 strlen(t->u.kernel.target->name)+1) != 0) {
                        ret = -EFAULT;
                        goto free_counters;
                }
        }

 free_counters:
        vfree(counters);
        return ret;
}

#ifdef CONFIG_COMPAT
static void compat_standard_from_user(void *dst, const void *src)
{
        int v = *(compat_int_t *)src;

        if (v > 0)
                v += xt_compat_calc_jump(AF_INET6, v);
        memcpy(dst, &v, sizeof(v));
}

static int compat_standard_to_user(void __user *dst, const void *src)
{
        compat_int_t cv = *(int *)src;

        if (cv > 0)
                cv -= xt_compat_calc_jump(AF_INET6, cv);
        return copy_to_user(dst, &cv, sizeof(cv)) ? -EFAULT : 0;
}

static int compat_calc_entry(const struct ip6t_entry *e,
                             const struct xt_table_info *info,
                             const void *base, struct xt_table_info *newinfo)
{
        const struct xt_entry_match *ematch;
        const struct ip6t_entry_target *t;
        unsigned int entry_offset;
        int off, i, ret;

        off = sizeof(struct ip6t_entry) - sizeof(struct compat_ip6t_entry);
        entry_offset = (void *)e - base;
        xt_ematch_foreach(ematch, e)
                off += xt_compat_match_offset(ematch->u.kernel.match);
        t = ip6t_get_target_c(e);
        off += xt_compat_target_offset(t->u.kernel.target);
        newinfo->size -= off;
        ret = xt_compat_add_offset(AF_INET6, entry_offset, off);
        if (ret)
                return ret;

        for (i = 0; i < NF_INET_NUMHOOKS; i++) {
                if (info->hook_entry[i] &&
                    (e < (struct ip6t_entry *)(base + info->hook_entry[i])))
                        newinfo->hook_entry[i] -= off;
                if (info->underflow[i] &&
                    (e < (struct ip6t_entry *)(base + info->underflow[i])))
                        newinfo->underflow[i] -= off;
        }
        return 0;
}

static int compat_table_info(const struct xt_table_info *info,
                             struct xt_table_info *newinfo)
{
        struct ip6t_entry *iter;
        void *loc_cpu_entry;
        int ret;

        if (!newinfo || !info)
                return -EINVAL;

        /* we dont care about newinfo->entries[] */
        memcpy(newinfo, info, offsetof(struct xt_table_info, entries));
        newinfo->initial_entries = 0;
        loc_cpu_entry = info->entries[raw_smp_processor_id()];
        xt_entry_foreach(iter, loc_cpu_entry, info->size) {
                ret = compat_calc_entry(iter, info, loc_cpu_entry, newinfo);
                if (ret != 0)
                        return ret;
        }
        return 0;
}
#endif

static int get_info(struct net *net, void __user *user,
                    const int *len, int compat)
{
        char name[IP6T_TABLE_MAXNAMELEN];
        struct xt_table *t;
        int ret;

        if (*len != sizeof(struct ip6t_getinfo)) {
                duprintf("length %u != %zu\n", *len,
                         sizeof(struct ip6t_getinfo));
                return -EINVAL;
        }

        if (copy_from_user(name, user, sizeof(name)) != 0)
                return -EFAULT;

        name[IP6T_TABLE_MAXNAMELEN-1] = '\0';
#ifdef CONFIG_COMPAT
        if (compat)
                xt_compat_lock(AF_INET6);
#endif
        t = try_then_request_module(xt_find_table_lock(net, AF_INET6, name),
                                    "ip6table_%s", name);
        if (t && !IS_ERR(t)) {
                struct ip6t_getinfo info;
                const struct xt_table_info *private = t->private;
#ifdef CONFIG_COMPAT
                struct xt_table_info tmp;

                if (compat) {
                        ret = compat_table_info(private, &tmp);
                        xt_compat_flush_offsets(AF_INET6);
                        private = &tmp;
                }
#endif
                info.valid_hooks = t->valid_hooks;
                memcpy(info.hook_entry, private->hook_entry,
                       sizeof(info.hook_entry));
                memcpy(info.underflow, private->underflow,
                       sizeof(info.underflow));
                info.num_entries = private->number;
                info.size = private->size;
                strcpy(info.name, name);

                if (copy_to_user(user, &info, *len) != 0)
                        ret = -EFAULT;
                else
                        ret = 0;

                xt_table_unlock(t);
                module_put(t->me);
        } else
                ret = t ? PTR_ERR(t) : -ENOENT;
#ifdef CONFIG_COMPAT
        if (compat)
                xt_compat_unlock(AF_INET6);
#endif
        return ret;
}

static int
get_entries(struct net *net, struct ip6t_get_entries __user *uptr,
            const int *len)
{
        int ret;
        struct ip6t_get_entries get;
        struct xt_table *t;

        if (*len < sizeof(get)) {
                duprintf("get_entries: %u < %zu\n", *len, sizeof(get));
                return -EINVAL;
        }
        if (copy_from_user(&get, uptr, sizeof(get)) != 0)
                return -EFAULT;
        if (*len != sizeof(struct ip6t_get_entries) + get.size) {
                duprintf("get_entries: %u != %zu\n",
                         *len, sizeof(get) + get.size);
                return -EINVAL;
        }

        t = xt_find_table_lock(net, AF_INET6, get.name);
        if (t && !IS_ERR(t)) {
                struct xt_table_info *private = t->private;
                duprintf("t->private->number = %u\n", private->number);
                if (get.size == private->size)
                        ret = copy_entries_to_user(private->size,
                                                   t, uptr->entrytable);
                else {
                        duprintf("get_entries: I've got %u not %u!\n",
                                 private->size, get.size);
                        ret = -EAGAIN;
                }
                module_put(t->me);
                xt_table_unlock(t);
        } else
                ret = t ? PTR_ERR(t) : -ENOENT;

        return ret;
}

static int
__do_replace(struct net *net, const char *name, unsigned int valid_hooks,
             struct xt_table_info *newinfo, unsigned int num_counters,
             void __user *counters_ptr)
{
        int ret;
        struct xt_table *t;
        struct xt_table_info *oldinfo;
        struct xt_counters *counters;
        const void *loc_cpu_old_entry;
        struct ip6t_entry *iter;

        ret = 0;
        counters = vmalloc_node(num_counters * sizeof(struct xt_counters),
                                numa_node_id());
        if (!counters) {
                ret = -ENOMEM;
                goto out;
        }

        t = try_then_request_module(xt_find_table_lock(net, AF_INET6, name),
                                    "ip6table_%s", name);
        if (!t || IS_ERR(t)) {
                ret = t ? PTR_ERR(t) : -ENOENT;
                goto free_newinfo_counters_untrans;
        }

        /* You lied! */
        if (valid_hooks != t->valid_hooks) {
                duprintf("Valid hook crap: %08X vs %08X\n",
                         valid_hooks, t->valid_hooks);
                ret = -EINVAL;
                goto put_module;
        }

        oldinfo = xt_replace_table(t, num_counters, newinfo, &ret);
        if (!oldinfo)
                goto put_module;

        /* Update module usage count based on number of rules */
        duprintf("do_replace: oldnum=%u, initnum=%u, newnum=%u\n",
                oldinfo->number, oldinfo->initial_entries, newinfo->number);
        if ((oldinfo->number > oldinfo->initial_entries) ||
            (newinfo->number <= oldinfo->initial_entries))
                module_put(t->me);
        if ((oldinfo->number > oldinfo->initial_entries) &&
            (newinfo->number <= oldinfo->initial_entries))
                module_put(t->me);

        /* Get the old counters, and synchronize with replace */
        get_counters(oldinfo, counters);

        /* Decrease module usage counts and free resource */
        loc_cpu_old_entry = oldinfo->entries[raw_smp_processor_id()];
        xt_entry_foreach(iter, loc_cpu_old_entry, oldinfo->size)
                cleanup_entry(iter, net);

        xt_free_table_info(oldinfo);
        if (copy_to_user(counters_ptr, counters,
                         sizeof(struct xt_counters) * num_counters) != 0)
                ret = -EFAULT;
        vfree(counters);
        xt_table_unlock(t);
        return ret;

 put_module:
        module_put(t->me);
        xt_table_unlock(t);
 free_newinfo_counters_untrans:
        vfree(counters);
 out:
        return ret;
}

static int
do_replace(struct net *net, const void __user *user, unsigned int len)
{
        int ret;
        struct ip6t_replace tmp;
        struct xt_table_info *newinfo;
        void *loc_cpu_entry;
        struct ip6t_entry *iter;

        if (copy_from_user(&tmp, user, sizeof(tmp)) != 0)
                return -EFAULT;

        /* overflow check */
        if (tmp.num_counters >= INT_MAX / sizeof(struct xt_counters))
                return -ENOMEM;

        newinfo = xt_alloc_table_info(tmp.size);
        if (!newinfo)
                return -ENOMEM;

        /* choose the copy that is on our node/cpu */
        loc_cpu_entry = newinfo->entries[raw_smp_processor_id()];
        if (copy_from_user(loc_cpu_entry, user + sizeof(tmp),
                           tmp.size) != 0) {
                ret = -EFAULT;
                goto free_newinfo;
        }

        ret = translate_table(net, tmp.name, tmp.valid_hooks,
                              newinfo, loc_cpu_entry, tmp.size, tmp.num_entries,
                              tmp.hook_entry, tmp.underflow);
        if (ret != 0)
                goto free_newinfo;

        duprintf("ip_tables: Translated table\n");

        ret = __do_replace(net, tmp.name, tmp.valid_hooks, newinfo,
                           tmp.num_counters, tmp.counters);
        if (ret)
                goto free_newinfo_untrans;
        return 0;

 free_newinfo_untrans:
        xt_entry_foreach(iter, loc_cpu_entry, newinfo->size)
                cleanup_entry(iter, net);
 free_newinfo:
        xt_free_table_info(newinfo);
        return ret;
}

static int
do_add_counters(struct net *net, const void __user *user, unsigned int len,
                int compat)
{
        unsigned int i, curcpu;
        struct xt_counters_info tmp;
        struct xt_counters *paddc;
        unsigned int num_counters;
        char *name;
        int size;
        void *ptmp;
        struct xt_table *t;
        const struct xt_table_info *private;
        int ret = 0;
        const void *loc_cpu_entry;
        struct ip6t_entry *iter;
#ifdef CONFIG_COMPAT
        struct compat_xt_counters_info compat_tmp;

        if (compat) {
                ptmp = &compat_tmp;
                size = sizeof(struct compat_xt_counters_info);
        } else
#endif
        {
                ptmp = &tmp;
                size = sizeof(struct xt_counters_info);
        }

        if (copy_from_user(ptmp, user, size) != 0)
                return -EFAULT;

#ifdef CONFIG_COMPAT
        if (compat) {
                num_counters = compat_tmp.num_counters;
                name = compat_tmp.name;
        } else
#endif
        {
                num_counters = tmp.num_counters;
                name = tmp.name;
        }

        if (len != size + num_counters * sizeof(struct xt_counters))
                return -EINVAL;

        paddc = vmalloc_node(len - size, numa_node_id());
        if (!paddc)
                return -ENOMEM;

        if (copy_from_user(paddc, user + size, len - size) != 0) {
                ret = -EFAULT;
                goto free;
        }

        t = xt_find_table_lock(net, AF_INET6, name);
        if (!t || IS_ERR(t)) {
                ret = t ? PTR_ERR(t) : -ENOENT;
                goto free;
        }


        local_bh_disable();
        private = t->private;
        if (private->number != num_counters) {
                ret = -EINVAL;
                goto unlock_up_free;
        }

        i = 0;
        /* Choose the copy that is on our node */
        curcpu = smp_processor_id();
        xt_info_wrlock(curcpu);
        loc_cpu_entry = private->entries[curcpu];
        xt_entry_foreach(iter, loc_cpu_entry, private->size) {
                ADD_COUNTER(iter->counters, paddc[i].bcnt, paddc[i].pcnt);
                ++i;
        }
        xt_info_wrunlock(curcpu);

 unlock_up_free:
        local_bh_enable();
        xt_table_unlock(t);
        module_put(t->me);
 free:
        vfree(paddc);

        return ret;
}

#ifdef CONFIG_COMPAT
struct compat_ip6t_replace {
        char                    name[IP6T_TABLE_MAXNAMELEN];
        u32                     valid_hooks;
        u32                     num_entries;
        u32                     size;
        u32                     hook_entry[NF_INET_NUMHOOKS];
        u32                     underflow[NF_INET_NUMHOOKS];
        u32                     num_counters;
        compat_uptr_t           counters;       /* struct ip6t_counters * */
        struct compat_ip6t_entry entries[0];
};

static int
compat_copy_entry_to_user(struct ip6t_entry *e, void __user **dstptr,
                          unsigned int *size, struct xt_counters *counters,
                          unsigned int i)
{
        struct ip6t_entry_target *t;
        struct compat_ip6t_entry __user *ce;
        u_int16_t target_offset, next_offset;
        compat_uint_t origsize;
        const struct xt_entry_match *ematch;
        int ret = 0;

        origsize = *size;
        ce = (struct compat_ip6t_entry __user *)*dstptr;
        if (copy_to_user(ce, e, sizeof(struct ip6t_entry)) != 0 ||
            copy_to_user(&ce->counters, &counters[i],
            sizeof(counters[i])) != 0)
                return -EFAULT;

        *dstptr += sizeof(struct compat_ip6t_entry);
        *size -= sizeof(struct ip6t_entry) - sizeof(struct compat_ip6t_entry);

        xt_ematch_foreach(ematch, e) {
                ret = xt_compat_match_to_user(ematch, dstptr, size);
                if (ret != 0)
                        return ret;
        }
        target_offset = e->target_offset - (origsize - *size);
        t = ip6t_get_target(e);
        ret = xt_compat_target_to_user(t, dstptr, size);
        if (ret)
                return ret;
        next_offset = e->next_offset - (origsize - *size);
        if (put_user(target_offset, &ce->target_offset) != 0 ||
            put_user(next_offset, &ce->next_offset) != 0)
                return -EFAULT;
        return 0;
}

static int
compat_find_calc_match(struct ip6t_entry_match *m,
                       const char *name,
                       const struct ip6t_ip6 *ipv6,
                       unsigned int hookmask,
                       int *size)
{
        struct xt_match *match;

        match = try_then_request_module(xt_find_match(AF_INET6, m->u.user.name,
                                                      m->u.user.revision),
                                        "ip6t_%s", m->u.user.name);
        if (IS_ERR(match) || !match) {
                duprintf("compat_check_calc_match: `%s' not found\n",
                         m->u.user.name);
                return match ? PTR_ERR(match) : -ENOENT;
        }
        m->u.kernel.match = match;
        *size += xt_compat_match_offset(match);
        return 0;
}

static void compat_release_entry(struct compat_ip6t_entry *e)
{
        struct ip6t_entry_target *t;
        struct xt_entry_match *ematch;

        /* Cleanup all matches */
        xt_ematch_foreach(ematch, e)
                module_put(ematch->u.kernel.match->me);
        t = compat_ip6t_get_target(e);
        module_put(t->u.kernel.target->me);
}

static int
check_compat_entry_size_and_hooks(struct compat_ip6t_entry *e,
                                  struct xt_table_info *newinfo,
                                  unsigned int *size,
                                  const unsigned char *base,
                                  const unsigned char *limit,
                                  const unsigned int *hook_entries,
                                  const unsigned int *underflows,
                                  const char *name)
{
        struct xt_entry_match *ematch;
        struct ip6t_entry_target *t;
        struct xt_target *target;
        unsigned int entry_offset;
        unsigned int j;
        int ret, off, h;

        duprintf("check_compat_entry_size_and_hooks %p\n", e);
        if ((unsigned long)e % __alignof__(struct compat_ip6t_entry) != 0 ||
            (unsigned char *)e + sizeof(struct compat_ip6t_entry) >= limit) {
                duprintf("Bad offset %p, limit = %p\n", e, limit);
                return -EINVAL;
        }

        if (e->next_offset < sizeof(struct compat_ip6t_entry) +
                             sizeof(struct compat_xt_entry_target)) {
                duprintf("checking: element %p size %u\n",
                         e, e->next_offset);
                return -EINVAL;
        }

        /* For purposes of check_entry casting the compat entry is fine */
        ret = check_entry((struct ip6t_entry *)e, name);
        if (ret)
                return ret;

        off = sizeof(struct ip6t_entry) - sizeof(struct compat_ip6t_entry);
        entry_offset = (void *)e - (void *)base;
        j = 0;
        xt_ematch_foreach(ematch, e) {
                ret = compat_find_calc_match(ematch, name,
                      &e->ipv6, e->comefrom, &off);
                if (ret != 0)
                        goto release_matches;
                ++j;
        }

        t = compat_ip6t_get_target(e);
        target = try_then_request_module(xt_find_target(AF_INET6,
                                                        t->u.user.name,
                                                        t->u.user.revision),
                                         "ip6t_%s", t->u.user.name);
        if (IS_ERR(target) || !target) {
                duprintf("check_compat_entry_size_and_hooks: `%s' not found\n",
                         t->u.user.name);
                ret = target ? PTR_ERR(target) : -ENOENT;
                goto release_matches;
        }
        t->u.kernel.target = target;

        off += xt_compat_target_offset(target);
        *size += off;
        ret = xt_compat_add_offset(AF_INET6, entry_offset, off);
        if (ret)
                goto out;

        /* Check hooks & underflows */
        for (h = 0; h < NF_INET_NUMHOOKS; h++) {
                if ((unsigned char *)e - base == hook_entries[h])
                        newinfo->hook_entry[h] = hook_entries[h];
                if ((unsigned char *)e - base == underflows[h])
                        newinfo->underflow[h] = underflows[h];
        }

        /* Clear counters and comefrom */
        memset(&e->counters, 0, sizeof(e->counters));
        e->comefrom = 0;
        return 0;

out:
        module_put(t->u.kernel.target->me);
release_matches:
        xt_ematch_foreach(ematch, e) {
                if (j-- == 0)
                        break;
                module_put(ematch->u.kernel.match->me);
        }
        return ret;
}

static int
compat_copy_entry_from_user(struct compat_ip6t_entry *e, void **dstptr,
                            unsigned int *size, const char *name,
                            struct xt_table_info *newinfo, unsigned char *base)
{
        struct ip6t_entry_target *t;
        struct xt_target *target;
        struct ip6t_entry *de;
        unsigned int origsize;
        int ret, h;
        struct xt_entry_match *ematch;

        ret = 0;
        origsize = *size;
        de = (struct ip6t_entry *)*dstptr;
        memcpy(de, e, sizeof(struct ip6t_entry));
        memcpy(&de->counters, &e->counters, sizeof(e->counters));

        *dstptr += sizeof(struct ip6t_entry);
        *size += sizeof(struct ip6t_entry) - sizeof(struct compat_ip6t_entry);

        xt_ematch_foreach(ematch, e) {
                ret = xt_compat_match_from_user(ematch, dstptr, size);
                if (ret != 0)
                        return ret;
        }
        de->target_offset = e->target_offset - (origsize - *size);
        t = compat_ip6t_get_target(e);
        target = t->u.kernel.target;
        xt_compat_target_from_user(t, dstptr, size);

        de->next_offset = e->next_offset - (origsize - *size);
        for (h = 0; h < NF_INET_NUMHOOKS; h++) {
                if ((unsigned char *)de - base < newinfo->hook_entry[h])
                        newinfo->hook_entry[h] -= origsize - *size;
                if ((unsigned char *)de - base < newinfo->underflow[h])
                        newinfo->underflow[h] -= origsize - *size;
        }
        return ret;
}

static int compat_check_entry(struct ip6t_entry *e, struct net *net,
                              const char *name)
{
        unsigned int j;
        int ret = 0;
        struct xt_mtchk_param mtpar;
        struct xt_entry_match *ematch;

        j = 0;
        mtpar.net       = net;
        mtpar.table     = name;
        mtpar.entryinfo = &e->ipv6;
        mtpar.hook_mask = e->comefrom;
        mtpar.family    = NFPROTO_IPV6;
        xt_ematch_foreach(ematch, e) {
                ret = check_match(ematch, &mtpar);
                if (ret != 0)
                        goto cleanup_matches;
                ++j;
        }

        ret = check_target(e, net, name);
        if (ret)
                goto cleanup_matches;
        return 0;

 cleanup_matches:
        xt_ematch_foreach(ematch, e) {
                if (j-- == 0)
                        break;
                cleanup_match(ematch, net);
        }
        return ret;
}

static int
translate_compat_table(struct net *net,
                       const char *name,
                       unsigned int valid_hooks,
                       struct xt_table_info **pinfo,
                       void **pentry0,
                       unsigned int total_size,
                       unsigned int number,
                       unsigned int *hook_entries,
                       unsigned int *underflows)
{
        unsigned int i, j;
        struct xt_table_info *newinfo, *info;
        void *pos, *entry0, *entry1;
        struct compat_ip6t_entry *iter0;
        struct ip6t_entry *iter1;
        unsigned int size;
        int ret = 0;

        info = *pinfo;
        entry0 = *pentry0;
        size = total_size;
        info->number = number;

        /* Init all hooks to impossible value. */
        for (i = 0; i < NF_INET_NUMHOOKS; i++) {
                info->hook_entry[i] = 0xFFFFFFFF;
                info->underflow[i] = 0xFFFFFFFF;
        }

        duprintf("translate_compat_table: size %u\n", info->size);
        j = 0;
        xt_compat_lock(AF_INET6);
        /* Walk through entries, checking offsets. */
        xt_entry_foreach(iter0, entry0, total_size) {
                ret = check_compat_entry_size_and_hooks(iter0, info, &size,
                      entry0, entry0 + total_size, hook_entries, underflows,
                      name);
                if (ret != 0)
                        goto out_unlock;
                ++j;
        }

        ret = -EINVAL;
        if (j != number) {
                duprintf("translate_compat_table: %u not %u entries\n",
                         j, number);
                goto out_unlock;
        }

        /* Check hooks all assigned */
        for (i = 0; i < NF_INET_NUMHOOKS; i++) {
                /* Only hooks which are valid */
                if (!(valid_hooks & (1 << i)))
                        continue;
                if (info->hook_entry[i] == 0xFFFFFFFF) {
                        duprintf("Invalid hook entry %u %u\n",
                                 i, hook_entries[i]);
                        goto out_unlock;
                }
                if (info->underflow[i] == 0xFFFFFFFF) {
                        duprintf("Invalid underflow %u %u\n",
                                 i, underflows[i]);
                        goto out_unlock;
                }
        }

        ret = -ENOMEM;
        newinfo = xt_alloc_table_info(size);
        if (!newinfo)
                goto out_unlock;

        newinfo->number = number;
        for (i = 0; i < NF_INET_NUMHOOKS; i++) {
                newinfo->hook_entry[i] = info->hook_entry[i];
                newinfo->underflow[i] = info->underflow[i];
        }
        entry1 = newinfo->entries[raw_smp_processor_id()];
        pos = entry1;
        size = total_size;
        xt_entry_foreach(iter0, entry0, total_size) {
                ret = compat_copy_entry_from_user(iter0, &pos,
                      &size, name, newinfo, entry1);
                if (ret != 0)
                        break;
        }
        xt_compat_flush_offsets(AF_INET6);
        xt_compat_unlock(AF_INET6);
        if (ret)
                goto free_newinfo;

        ret = -ELOOP;
        if (!mark_source_chains(newinfo, valid_hooks, entry1))
                goto free_newinfo;

        i = 0;
        xt_entry_foreach(iter1, entry1, newinfo->size) {
                ret = compat_check_entry(iter1, net, name);
                if (ret != 0)
                        break;
                ++i;
        }
        if (ret) {
                /*
                 * The first i matches need cleanup_entry (calls ->destroy)
                 * because they had called ->check already. The other j-i
                 * entries need only release.
                 */
                int skip = i;
                j -= i;
                xt_entry_foreach(iter0, entry0, newinfo->size) {
                        if (skip-- > 0)
                                continue;
                        if (j-- == 0)
                                break;
                        compat_release_entry(iter0);
                }
                xt_entry_foreach(iter1, entry1, newinfo->size) {
                        if (i-- == 0)
                                break;
                        cleanup_entry(iter1, net);
                }
                xt_free_table_info(newinfo);
                return ret;
        }

        /* And one copy for every other CPU */
        for_each_possible_cpu(i)
                if (newinfo->entries[i] && newinfo->entries[i] != entry1)
                        memcpy(newinfo->entries[i], entry1, newinfo->size);

        *pinfo = newinfo;
        *pentry0 = entry1;
        xt_free_table_info(info);
        return 0;

free_newinfo:
        xt_free_table_info(newinfo);
out:
        xt_entry_foreach(iter0, entry0, total_size) {
                if (j-- == 0)
                        break;
                compat_release_entry(iter0);
        }
        return ret;
out_unlock:
        xt_compat_flush_offsets(AF_INET6);
        xt_compat_unlock(AF_INET6);
        goto out;
}

static int
compat_do_replace(struct net *net, void __user *user, unsigned int len)
{
        int ret;
        struct compat_ip6t_replace tmp;
        struct xt_table_info *newinfo;
        void *loc_cpu_entry;
        struct ip6t_entry *iter;

        if (copy_from_user(&tmp, user, sizeof(tmp)) != 0)
                return -EFAULT;

        /* overflow check */
        if (tmp.size >= INT_MAX / num_possible_cpus())
                return -ENOMEM;
        if (tmp.num_counters >= INT_MAX / sizeof(struct xt_counters))
                return -ENOMEM;

        newinfo = xt_alloc_table_info(tmp.size);
        if (!newinfo)
                return -ENOMEM;

        /* choose the copy that is on our node/cpu */
        loc_cpu_entry = newinfo->entries[raw_smp_processor_id()];
        if (copy_from_user(loc_cpu_entry, user + sizeof(tmp),
                           tmp.size) != 0) {
                ret = -EFAULT;
                goto free_newinfo;
        }

        ret = translate_compat_table(net, tmp.name, tmp.valid_hooks,
                                     &newinfo, &loc_cpu_entry, tmp.size,
                                     tmp.num_entries, tmp.hook_entry,
                                     tmp.underflow);
        if (ret != 0)
                goto free_newinfo;

        duprintf("compat_do_replace: Translated table\n");

        ret = __do_replace(net, tmp.name, tmp.valid_hooks, newinfo,
                           tmp.num_counters, compat_ptr(tmp.counters));
        if (ret)
                goto free_newinfo_untrans;
        return 0;

 free_newinfo_untrans:
        xt_entry_foreach(iter, loc_cpu_entry, newinfo->size)
                cleanup_entry(iter, net);
 free_newinfo:
        xt_free_table_info(newinfo);
        return ret;
}

static int
compat_do_ip6t_set_ctl(struct sock *sk, int cmd, void __user *user,
                       unsigned int len)
{
        int ret;

        if (!capable(CAP_NET_ADMIN))
                return -EPERM;

        switch (cmd) {
        case IP6T_SO_SET_REPLACE:
                ret = compat_do_replace(sock_net(sk), user, len);
                break;

        case IP6T_SO_SET_ADD_COUNTERS:
                ret = do_add_counters(sock_net(sk), user, len, 1);
                break;

        default:
                duprintf("do_ip6t_set_ctl:  unknown request %i\n", cmd);
                ret = -EINVAL;
        }

        return ret;
}

struct compat_ip6t_get_entries {
        char name[IP6T_TABLE_MAXNAMELEN];
        compat_uint_t size;
        struct compat_ip6t_entry entrytable[0];
};

static int
compat_copy_entries_to_user(unsigned int total_size, struct xt_table *table,
                            void __user *userptr)
{
        struct xt_counters *counters;
        const struct xt_table_info *private = table->private;
        void __user *pos;
        unsigned int size;
        int ret = 0;
        const void *loc_cpu_entry;
        unsigned int i = 0;
        struct ip6t_entry *iter;

        counters = alloc_counters(table);
        if (IS_ERR(counters))
                return PTR_ERR(counters);

        /* choose the copy that is on our node/cpu, ...
         * This choice is lazy (because current thread is
         * allowed to migrate to another cpu)
         */
        loc_cpu_entry = private->entries[raw_smp_processor_id()];
        pos = userptr;
        size = total_size;
        xt_entry_foreach(iter, loc_cpu_entry, total_size) {
                ret = compat_copy_entry_to_user(iter, &pos,
                      &size, counters, i++);
                if (ret != 0)
                        break;
        }

        vfree(counters);
        return ret;
}

static int
compat_get_entries(struct net *net, struct compat_ip6t_get_entries __user *uptr,
                   int *len)
{
        int ret;
        struct compat_ip6t_get_entries get;
        struct xt_table *t;

        if (*len < sizeof(get)) {
                duprintf("compat_get_entries: %u < %zu\n", *len, sizeof(get));
                return -EINVAL;
        }

        if (copy_from_user(&get, uptr, sizeof(get)) != 0)
                return -EFAULT;

        if (*len != sizeof(struct compat_ip6t_get_entries) + get.size) {
                duprintf("compat_get_entries: %u != %zu\n",
                         *len, sizeof(get) + get.size);
                return -EINVAL;
        }

        xt_compat_lock(AF_INET6);
        t = xt_find_table_lock(net, AF_INET6, get.name);
        if (t && !IS_ERR(t)) {
                const struct xt_table_info *private = t->private;
                struct xt_table_info info;
                duprintf("t->private->number = %u\n", private->number);
                ret = compat_table_info(private, &info);
                if (!ret && get.size == info.size) {
                        ret = compat_copy_entries_to_user(private->size,
                                                          t, uptr->entrytable);
                } else if (!ret) {
                        duprintf("compat_get_entries: I've got %u not %u!\n",
                                 private->size, get.size);
                        ret = -EAGAIN;
                }
                xt_compat_flush_offsets(AF_INET6);
                module_put(t->me);
                xt_table_unlock(t);
        } else
                ret = t ? PTR_ERR(t) : -ENOENT;

        xt_compat_unlock(AF_INET6);
        return ret;
}

static int do_ip6t_get_ctl(struct sock *, int, void __user *, int *);

static int
compat_do_ip6t_get_ctl(struct sock *sk, int cmd, void __user *user, int *len)
{
        int ret;

        if (!capable(CAP_NET_ADMIN))
                return -EPERM;

        switch (cmd) {
        case IP6T_SO_GET_INFO:
                ret = get_info(sock_net(sk), user, len, 1);
                break;
        case IP6T_SO_GET_ENTRIES:
                ret = compat_get_entries(sock_net(sk), user, len);
                break;
        default:
                ret = do_ip6t_get_ctl(sk, cmd, user, len);
        }
        return ret;
}
#endif

static int
do_ip6t_set_ctl(struct sock *sk, int cmd, void __user *user, unsigned int len)
{
        int ret;

        if (!capable(CAP_NET_ADMIN))
                return -EPERM;

        switch (cmd) {
        case IP6T_SO_SET_REPLACE:
                ret = do_replace(sock_net(sk), user, len);
                break;

        case IP6T_SO_SET_ADD_COUNTERS:
                ret = do_add_counters(sock_net(sk), user, len, 0);
                break;

        default:
                duprintf("do_ip6t_set_ctl:  unknown request %i\n", cmd);
                ret = -EINVAL;
        }

        return ret;
}

static int
do_ip6t_get_ctl(struct sock *sk, int cmd, void __user *user, int *len)
{
        int ret;

        if (!capable(CAP_NET_ADMIN))
                return -EPERM;

        switch (cmd) {
        case IP6T_SO_GET_INFO:
                ret = get_info(sock_net(sk), user, len, 0);
                break;

        case IP6T_SO_GET_ENTRIES:
                ret = get_entries(sock_net(sk), user, len);
                break;

        case IP6T_SO_GET_REVISION_MATCH:
        case IP6T_SO_GET_REVISION_TARGET: {
                struct ip6t_get_revision rev;
                int target;

                if (*len != sizeof(rev)) {
                        ret = -EINVAL;
                        break;
                }
                if (copy_from_user(&rev, user, sizeof(rev)) != 0) {
                        ret = -EFAULT;
                        break;
                }

                if (cmd == IP6T_SO_GET_REVISION_TARGET)
                        target = 1;
                else
                        target = 0;

                try_then_request_module(xt_find_revision(AF_INET6, rev.name,
                                                         rev.revision,
                                                         target, &ret),
                                        "ip6t_%s", rev.name);
                break;
        }

        default:
                duprintf("do_ip6t_get_ctl: unknown request %i\n", cmd);
                ret = -EINVAL;
        }

        return ret;
}

struct xt_table *ip6t_register_table(struct net *net,
                                     const struct xt_table *table,
                                     const struct ip6t_replace *repl)
{
        int ret;
        struct xt_table_info *newinfo;
        struct xt_table_info bootstrap
                = { 0, 0, 0, { 0 }, { 0 }, { } };
        void *loc_cpu_entry;
        struct xt_table *new_table;

        newinfo = xt_alloc_table_info(repl->size);
        if (!newinfo) {
                ret = -ENOMEM;
                goto out;
        }

        /* choose the copy on our node/cpu, but dont care about preemption */
        loc_cpu_entry = newinfo->entries[raw_smp_processor_id()];
        memcpy(loc_cpu_entry, repl->entries, repl->size);

        ret = translate_table(net, table->name, table->valid_hooks,
                              newinfo, loc_cpu_entry, repl->size,
                              repl->num_entries,
                              repl->hook_entry,
                              repl->underflow);
        if (ret != 0)
                goto out_free;

        new_table = xt_register_table(net, table, &bootstrap, newinfo);
        if (IS_ERR(new_table)) {
                ret = PTR_ERR(new_table);
                goto out_free;
        }
        return new_table;

out_free:
        xt_free_table_info(newinfo);
out:
        return ERR_PTR(ret);
}

void ip6t_unregister_table(struct net *net, struct xt_table *table)
{
        struct xt_table_info *private;
        void *loc_cpu_entry;
        struct module *table_owner = table->me;
        struct ip6t_entry *iter;

        private = xt_unregister_table(table);

        /* Decrease module usage counts and free resources */
        loc_cpu_entry = private->entries[raw_smp_processor_id()];
        xt_entry_foreach(iter, loc_cpu_entry, private->size)
                cleanup_entry(iter, net);
        if (private->number > private->initial_entries)
                module_put(table_owner);
        xt_free_table_info(private);
}

/* Returns 1 if the type and code is matched by the range, 0 otherwise */
static inline bool
icmp6_type_code_match(u_int8_t test_type, u_int8_t min_code, u_int8_t max_code,
                     u_int8_t type, u_int8_t code,
                     bool invert)
{
        return (type == test_type && code >= min_code && code <= max_code)
                ^ invert;
}

static bool
icmp6_match(const struct sk_buff *skb, const struct xt_match_param *par)
{
        const struct icmp6hdr *ic;
        struct icmp6hdr _icmph;
        const struct ip6t_icmp *icmpinfo = par->matchinfo;

        /* Must not be a fragment. */
        if (par->fragoff != 0)
                return false;

        ic = skb_header_pointer(skb, par->thoff, sizeof(_icmph), &_icmph);
        if (ic == NULL) {
                /* We've been asked to examine this packet, and we
                 * can't.  Hence, no choice but to drop.
                 */
                duprintf("Dropping evil ICMP tinygram.\n");
                *par->hotdrop = true;
                return false;
        }

        return icmp6_type_code_match(icmpinfo->type,
                                     icmpinfo->code[0],
                                     icmpinfo->code[1],
                                     ic->icmp6_type, ic->icmp6_code,
                                     !!(icmpinfo->invflags&IP6T_ICMP_INV));
}

/* Called when user tries to insert an entry of this type. */
static bool icmp6_checkentry(const struct xt_mtchk_param *par)
{
        const struct ip6t_icmp *icmpinfo = par->matchinfo;

        /* Must specify no unknown invflags */
        return !(icmpinfo->invflags & ~IP6T_ICMP_INV);
}

/* The built-in targets: standard (NULL) and error. */
static struct xt_target ip6t_standard_target __read_mostly = {
        .name           = IP6T_STANDARD_TARGET,
        .targetsize     = sizeof(int),
        .family         = NFPROTO_IPV6,
#ifdef CONFIG_COMPAT
        .compatsize     = sizeof(compat_int_t),
        .compat_from_user = compat_standard_from_user,
        .compat_to_user = compat_standard_to_user,
#endif
};

static struct xt_target ip6t_error_target __read_mostly = {
        .name           = IP6T_ERROR_TARGET,
        .target         = ip6t_error,
        .targetsize     = IP6T_FUNCTION_MAXNAMELEN,
        .family         = NFPROTO_IPV6,
};

static struct nf_sockopt_ops ip6t_sockopts = {
        .pf             = PF_INET6,
        .set_optmin     = IP6T_BASE_CTL,
        .set_optmax     = IP6T_SO_SET_MAX+1,
        .set            = do_ip6t_set_ctl,
#ifdef CONFIG_COMPAT
        .compat_set     = compat_do_ip6t_set_ctl,
#endif
        .get_optmin     = IP6T_BASE_CTL,
        .get_optmax     = IP6T_SO_GET_MAX+1,
        .get            = do_ip6t_get_ctl,
#ifdef CONFIG_COMPAT
        .compat_get     = compat_do_ip6t_get_ctl,
#endif
        .owner          = THIS_MODULE,
};

static struct xt_match icmp6_matchstruct __read_mostly = {
        .name           = "icmp6",
        .match          = icmp6_match,
        .matchsize      = sizeof(struct ip6t_icmp),
        .checkentry     = icmp6_checkentry,
        .proto          = IPPROTO_ICMPV6,
        .family         = NFPROTO_IPV6,
};

static int __net_init ip6_tables_net_init(struct net *net)
{
        return xt_proto_init(net, NFPROTO_IPV6);
}

static void __net_exit ip6_tables_net_exit(struct net *net)
{
        xt_proto_fini(net, NFPROTO_IPV6);
}

static struct pernet_operations ip6_tables_net_ops = {
        .init = ip6_tables_net_init,
        .exit = ip6_tables_net_exit,
};

static int __init ip6_tables_init(void)
{
        int ret;

        ret = register_pernet_subsys(&ip6_tables_net_ops);
        if (ret < 0)
                goto err1;

        /* Noone else will be downing sem now, so we won't sleep */
        ret = xt_register_target(&ip6t_standard_target);
        if (ret < 0)
                goto err2;
        ret = xt_register_target(&ip6t_error_target);
        if (ret < 0)
                goto err3;
        ret = xt_register_match(&icmp6_matchstruct);
        if (ret < 0)
                goto err4;

        /* Register setsockopt */
        ret = nf_register_sockopt(&ip6t_sockopts);
        if (ret < 0)
                goto err5;

        printk(KERN_INFO "ip6_tables: (C) 2000-2006 Netfilter Core Team\n");
        return 0;

err5:
        xt_unregister_match(&icmp6_matchstruct);
err4:
        xt_unregister_target(&ip6t_error_target);
err3:
        xt_unregister_target(&ip6t_standard_target);
err2:
        unregister_pernet_subsys(&ip6_tables_net_ops);
err1:
        return ret;
}

static void __exit ip6_tables_fini(void)
{
        nf_unregister_sockopt(&ip6t_sockopts);

        xt_unregister_match(&icmp6_matchstruct);
        xt_unregister_target(&ip6t_error_target);
        xt_unregister_target(&ip6t_standard_target);

        unregister_pernet_subsys(&ip6_tables_net_ops);
}

/*
 * find the offset to specified header or the protocol number of last header
 * if target < 0. "last header" is transport protocol header, ESP, or
 * "No next header".
 *
 * If target header is found, its offset is set in *offset and return protocol
 * number. Otherwise, return -1.
 *
 * If the first fragment doesn't contain the final protocol header or
 * NEXTHDR_NONE it is considered invalid.
 *
 * Note that non-1st fragment is special case that "the protocol number
 * of last header" is "next header" field in Fragment header. In this case,
 * *offset is meaningless and fragment offset is stored in *fragoff if fragoff
 * isn't NULL.
 *
 */
int ipv6_find_hdr(const struct sk_buff *skb, unsigned int *offset,
                  int target, unsigned short *fragoff)
{
        unsigned int start = skb_network_offset(skb) + sizeof(struct ipv6hdr);
        u8 nexthdr = ipv6_hdr(skb)->nexthdr;
        unsigned int len = skb->len - start;

        if (fragoff)
                *fragoff = 0;

        while (nexthdr != target) {
                struct ipv6_opt_hdr _hdr, *hp;
                unsigned int hdrlen;

                if ((!ipv6_ext_hdr(nexthdr)) || nexthdr == NEXTHDR_NONE) {
                        if (target < 0)
                                break;
                        return -ENOENT;
                }

                hp = skb_header_pointer(skb, start, sizeof(_hdr), &_hdr);
                if (hp == NULL)
                        return -EBADMSG;
                if (nexthdr == NEXTHDR_FRAGMENT) {
                        unsigned short _frag_off;
                        __be16 *fp;
                        fp = skb_header_pointer(skb,
                                                start+offsetof(struct frag_hdr,
                                                               frag_off),
                                                sizeof(_frag_off),
                                                &_frag_off);
                        if (fp == NULL)
                                return -EBADMSG;

                        _frag_off = ntohs(*fp) & ~0x7;
                        if (_frag_off) {
                                if (target < 0 &&
                                    ((!ipv6_ext_hdr(hp->nexthdr)) ||
                                     hp->nexthdr == NEXTHDR_NONE)) {
                                        if (fragoff)
                                                *fragoff = _frag_off;
                                        return hp->nexthdr;
                                }
                                return -ENOENT;
                        }
                        hdrlen = 8;
                } else if (nexthdr == NEXTHDR_AUTH)
                        hdrlen = (hp->hdrlen + 2) << 2;
                else
                        hdrlen = ipv6_optlen(hp);

                nexthdr = hp->nexthdr;
                len -= hdrlen;
                start += hdrlen;
        }

        *offset = start;
        return nexthdr;
}

EXPORT_SYMBOL(ip6t_register_table);
EXPORT_SYMBOL(ip6t_unregister_table);
EXPORT_SYMBOL(ip6t_do_table);
EXPORT_SYMBOL(ip6t_ext_hdr);
EXPORT_SYMBOL(ipv6_find_hdr);

module_init(ip6_tables_init);
module_exit(ip6_tables_fini);