[NETFILTER]: Introduce NF_INET_ hook values

[mirror_ubuntu-bionic-kernel.git] / 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.
 */

#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 <asm/uaccess.h>
#include <linux/mutex.h>
#include <linux/proc_fs.h>
#include <linux/cpumask.h>

#include <linux/netfilter_ipv6/ip6_tables.h>
#include <linux/netfilter/x_tables.h>

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

#define IPV6_HDR_LEN    (sizeof(struct ipv6hdr))
#define IPV6_OPTHDR_LEN (sizeof(struct ipv6_opt_hdr))

/*#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",              \
                       __FUNCTION__, __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

/*
   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.  */

#if 0
#define down(x) do { printk("DOWN:%u:" #x "\n", __LINE__); down(x); } while(0)
#define down_interruptible(x) ({ int __r; printk("DOWNi:%u:" #x "\n", __LINE__); __r = down_interruptible(x); if (__r != 0) printk("ABORT-DOWNi:%u\n", __LINE__); __r; })
#define up(x) do { printk("UP:%u:" #x "\n", __LINE__); up(x); } while(0)
#endif

/* 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. */
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)
{
        size_t i;
        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;
        }

        /* Look for ifname matches; this should unroll nicely. */
        for (i = 0, ret = 0; i < IFNAMSIZ/sizeof(unsigned long); i++) {
                ret |= (((const unsigned long *)indev)[i]
                        ^ ((const unsigned long *)ip6info->iniface)[i])
                        & ((const unsigned long *)ip6info->iniface_mask)[i];
        }

        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;
        }

        for (i = 0, ret = 0; i < IFNAMSIZ/sizeof(unsigned long); i++) {
                ret |= (((const unsigned long *)outdev)[i]
                        ^ ((const unsigned long *)ip6info->outiface)[i])
                        & ((const unsigned long *)ip6info->outiface_mask)[i];
        }

        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 inline 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 net_device *in,
          const struct net_device *out,
          unsigned int hooknum,
          const struct xt_target *target,
          const void *targinfo)
{
        if (net_ratelimit())
                printk("ip6_tables: error: `%s'\n", (char *)targinfo);

        return NF_DROP;
}

static inline
bool do_match(struct ip6t_entry_match *m,
              const struct sk_buff *skb,
              const struct net_device *in,
              const struct net_device *out,
              int offset,
              unsigned int protoff,
              bool *hotdrop)
{
        /* Stop iteration if it doesn't match */
        if (!m->u.kernel.match->match(skb, in, out, m->u.kernel.match, m->data,
                                      offset, protoff, hotdrop))
                return true;
        else
                return false;
}

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

/* All zeroes == unconditional rule. */
static inline int
unconditional(const struct ip6t_ip6 *ipv6)
{
        unsigned int i;

        for (i = 0; i < sizeof(*ipv6); i++)
                if (((char *)ipv6)[i])
                        break;

        return (i == sizeof(*ipv6));
}

#if defined(CONFIG_NETFILTER_XT_TARGET_TRACE) || \
    defined(CONFIG_NETFILTER_XT_TARGET_TRACE_MODULE)
/* This cries for unification! */
static const char *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 *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,
                },
        },
};

static inline int
get_chainname_rulenum(struct ip6t_entry *s, struct ip6t_entry *e,
                      char *hookname, char **chainname,
                      char **comment, unsigned int *rulenum)
{
        struct ip6t_standard_target *t = (void *)ip6t_get_target(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
                                ? (char *)comments[NF_IP6_TRACE_COMMENT_POLICY]
                                : (char *)comments[NF_IP6_TRACE_COMMENT_RETURN];
                }
                return 1;
        } else
                (*rulenum)++;

        return 0;
}

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

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

        hookname = chainname = (char *)hooknames[hook];
        comment = (char *)comments[NF_IP6_TRACE_COMMENT_RULE];

        IP6T_ENTRY_ITERATE(root,
                           private->size - private->hook_entry[hook],
                           get_chainname_rulenum,
                           e, hookname, &chainname, &comment, &rulenum);

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

/* 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)
{
        static const char nulldevname[IFNAMSIZ] __attribute__((aligned(sizeof(long))));
        int offset = 0;
        unsigned int protoff = 0;
        bool hotdrop = false;
        /* Initializing verdict to NF_DROP keeps gcc happy. */
        unsigned int verdict = NF_DROP;
        const char *indev, *outdev;
        void *table_base;
        struct ip6t_entry *e, *back;
        struct xt_table_info *private;

        /* 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. */

        read_lock_bh(&table->lock);
        private = table->private;
        IP_NF_ASSERT(table->valid_hooks & (1 << hook));
        table_base = (void *)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 {
                IP_NF_ASSERT(e);
                IP_NF_ASSERT(back);
                if (ip6_packet_match(skb, indev, outdev, &e->ipv6,
                        &protoff, &offset, &hotdrop)) {
                        struct ip6t_entry_target *t;

                        if (IP6T_MATCH_ITERATE(e, do_match,
                                               skb, in, out,
                                               offset, protoff, &hotdrop) != 0)
                                goto no_match;

                        ADD_COUNTER(e->counters,
                                    ntohs(ipv6_hdr(skb)->payload_len)
                                    + IPV6_HDR_LEN,
                                    1);

                        t = ip6t_get_target(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 != (void *)e + e->next_offset
                                    && !(e->ipv6.flags & IP6T_F_GOTO)) {
                                        /* Save old back ptr in next entry */
                                        struct ip6t_entry *next
                                                = (void *)e + e->next_offset;
                                        next->comefrom
                                                = (void *)back - table_base;
                                        /* set back pointer to next entry */
                                        back = next;
                                }

                                e = get_entry(table_base, v);
                        } else {
                                /* Targets which reenter must return
                                   abs. verdicts */
#ifdef CONFIG_NETFILTER_DEBUG
                                ((struct ip6t_entry *)table_base)->comefrom
                                        = 0xeeeeeeec;
#endif
                                verdict = t->u.kernel.target->target(skb,
                                                                     in, out,
                                                                     hook,
                                                                     t->u.kernel.target,
                                                                     t->data);

#ifdef CONFIG_NETFILTER_DEBUG
                                if (((struct ip6t_entry *)table_base)->comefrom
                                    != 0xeeeeeeec
                                    && verdict == IP6T_CONTINUE) {
                                        printk("Target %s reentered!\n",
                                               t->u.kernel.target->name);
                                        verdict = NF_DROP;
                                }
                                ((struct ip6t_entry *)table_base)->comefrom
                                        = 0x57acc001;
#endif
                                if (verdict == IP6T_CONTINUE)
                                        e = (void *)e + e->next_offset;
                                else
                                        /* Verdict */
                                        break;
                        }
                } else {

                no_match:
                        e = (void *)e + e->next_offset;
                }
        } while (!hotdrop);

#ifdef CONFIG_NETFILTER_DEBUG
        ((struct ip6t_entry *)table_base)->comefrom = NETFILTER_LINK_POISON;
#endif
        read_unlock_bh(&table->lock);

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

/* 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(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);
                int visited = e->comefrom & (1 << hook);

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

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

                for (;;) {
                        struct ip6t_standard_target *t
                                = (void *)ip6t_get_target(e);

                        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 (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 inline int
cleanup_match(struct ip6t_entry_match *m, unsigned int *i)
{
        if (i && (*i)-- == 0)
                return 1;

        if (m->u.kernel.match->destroy)
                m->u.kernel.match->destroy(m->u.kernel.match, m->data);
        module_put(m->u.kernel.match->me);
        return 0;
}

static inline int
check_match(struct ip6t_entry_match *m,
            const char *name,
            const struct ip6t_ip6 *ipv6,
            unsigned int hookmask,
            unsigned int *i)
{
        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("check_match: `%s' not found\n", m->u.user.name);
                return match ? PTR_ERR(match) : -ENOENT;
        }
        m->u.kernel.match = match;

        ret = xt_check_match(match, AF_INET6, m->u.match_size - sizeof(*m),
                             name, hookmask, ipv6->proto,
                             ipv6->invflags & IP6T_INV_PROTO);
        if (ret)
                goto err;

        if (m->u.kernel.match->checkentry
            && !m->u.kernel.match->checkentry(name, ipv6, match,  m->data,
                                              hookmask)) {
                duprintf("ip_tables: check failed for `%s'.\n",
                         m->u.kernel.match->name);
                ret = -EINVAL;
                goto err;
        }

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

static struct xt_target ip6t_standard_target;

static inline int
check_entry(struct ip6t_entry *e, const char *name, unsigned int size,
            unsigned int *i)
{
        struct ip6t_entry_target *t;
        struct xt_target *target;
        int ret;
        unsigned int j;

        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;

        j = 0;
        ret = IP6T_MATCH_ITERATE(e, check_match, name, &e->ipv6, e->comefrom, &j);
        if (ret != 0)
                goto cleanup_matches;

        t = ip6t_get_target(e);
        ret = -EINVAL;
        if (e->target_offset + t->u.target_size > e->next_offset)
                        goto cleanup_matches;
        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_entry: `%s' not found\n", t->u.user.name);
                ret = target ? PTR_ERR(target) : -ENOENT;
                goto cleanup_matches;
        }
        t->u.kernel.target = target;

        ret = xt_check_target(target, AF_INET6, t->u.target_size - sizeof(*t),
                              name, e->comefrom, e->ipv6.proto,
                              e->ipv6.invflags & IP6T_INV_PROTO);
        if (ret)
                goto err;

        if (t->u.kernel.target->checkentry
                   && !t->u.kernel.target->checkentry(name, e, target, t->data,
                                                      e->comefrom)) {
                duprintf("ip_tables: check failed for `%s'.\n",
                         t->u.kernel.target->name);
                ret = -EINVAL;
                goto err;
        }

        (*i)++;
        return 0;
 err:
        module_put(t->u.kernel.target->me);
 cleanup_matches:
        IP6T_MATCH_ITERATE(e, cleanup_match, &j);
        return ret;
}

static inline int
check_entry_size_and_hooks(struct ip6t_entry *e,
                           struct xt_table_info *newinfo,
                           unsigned char *base,
                           unsigned char *limit,
                           const unsigned int *hook_entries,
                           const unsigned int *underflows,
                           unsigned int *i)
{
        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 ((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];
        }

        /* FIXME: underflows must be unconditional, standard verdicts
           < 0 (not IP6T_RETURN). --RR */

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

        (*i)++;
        return 0;
}

static inline int
cleanup_entry(struct ip6t_entry *e, unsigned int *i)
{
        struct ip6t_entry_target *t;

        if (i && (*i)-- == 0)
                return 1;

        /* Cleanup all matches */
        IP6T_MATCH_ITERATE(e, cleanup_match, NULL);
        t = ip6t_get_target(e);
        if (t->u.kernel.target->destroy)
                t->u.kernel.target->destroy(t->u.kernel.target, t->data);
        module_put(t->u.kernel.target->me);
        return 0;
}

/* Checks and translates the user-supplied table segment (held in
   newinfo) */
static int
translate_table(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)
{
        unsigned int i;
        int ret;

        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. */
        ret = IP6T_ENTRY_ITERATE(entry0, newinfo->size,
                                check_entry_size_and_hooks,
                                newinfo,
                                entry0,
                                entry0 + size,
                                hook_entries, underflows, &i);
        if (ret != 0)
                return ret;

        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;
        ret = IP6T_ENTRY_ITERATE(entry0, newinfo->size,
                                check_entry, name, size, &i);

        if (ret != 0) {
                IP6T_ENTRY_ITERATE(entry0, newinfo->size,
                                   cleanup_entry, &i);
                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 0;
}

/* Gets counters. */
static inline int
add_entry_to_counter(const struct ip6t_entry *e,
                     struct xt_counters total[],
                     unsigned int *i)
{
        ADD_COUNTER(total[*i], e->counters.bcnt, e->counters.pcnt);

        (*i)++;
        return 0;
}

static inline int
set_entry_to_counter(const struct ip6t_entry *e,
                     struct ip6t_counters total[],
                     unsigned int *i)
{
        SET_COUNTER(total[*i], e->counters.bcnt, e->counters.pcnt);

        (*i)++;
        return 0;
}

static void
get_counters(const struct xt_table_info *t,
             struct xt_counters counters[])
{
        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
         * We dont care about preemption here.
         */
        curcpu = raw_smp_processor_id();

        i = 0;
        IP6T_ENTRY_ITERATE(t->entries[curcpu],
                           t->size,
                           set_entry_to_counter,
                           counters,
                           &i);

        for_each_possible_cpu(cpu) {
                if (cpu == curcpu)
                        continue;
                i = 0;
                IP6T_ENTRY_ITERATE(t->entries[cpu],
                                  t->size,
                                  add_entry_to_counter,
                                  counters,
                                  &i);
        }
}

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

        /* 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(countersize);

        if (counters == NULL)
                return -ENOMEM;

        /* First, sum counters... */
        write_lock_bh(&table->lock);
        get_counters(private, counters);
        write_unlock_bh(&table->lock);

        /* choose the copy that is on ourc node/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;
                struct ip6t_entry_match *m;
                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(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;
}

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

        t = xt_find_table_lock(AF_INET6, entries->name);
        if (t && !IS_ERR(t)) {
                struct xt_table_info *private = t->private;
                duprintf("t->private->number = %u\n", private->number);
                if (entries->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, entries->size);
                        ret = -EINVAL;
                }
                module_put(t->me);
                xt_table_unlock(t);
        } else
                ret = t ? PTR_ERR(t) : -ENOENT;

        return ret;
}

static int
do_replace(void __user *user, unsigned int len)
{
        int ret;
        struct ip6t_replace tmp;
        struct xt_table *t;
        struct xt_table_info *newinfo, *oldinfo;
        struct xt_counters *counters;
        void *loc_cpu_entry, *loc_cpu_old_entry;

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

        /* overflow check */
        if (tmp.size >= (INT_MAX - sizeof(struct xt_table_info)) / NR_CPUS -
                        SMP_CACHE_BYTES)
                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;
        }

        counters = vmalloc(tmp.num_counters * sizeof(struct xt_counters));
        if (!counters) {
                ret = -ENOMEM;
                goto free_newinfo;
        }

        ret = translate_table(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_counters;

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

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

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

        oldinfo = xt_replace_table(t, tmp.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. */
        get_counters(oldinfo, counters);
        /* Decrease module usage counts and free resource */
        loc_cpu_old_entry = oldinfo->entries[raw_smp_processor_id()];
        IP6T_ENTRY_ITERATE(loc_cpu_old_entry, oldinfo->size, cleanup_entry,NULL);
        xt_free_table_info(oldinfo);
        if (copy_to_user(tmp.counters, counters,
                         sizeof(struct xt_counters) * tmp.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:
        IP6T_ENTRY_ITERATE(loc_cpu_entry, newinfo->size, cleanup_entry,NULL);
 free_newinfo_counters:
        vfree(counters);
 free_newinfo:
        xt_free_table_info(newinfo);
        return ret;
}

/* We're lazy, and add to the first CPU; overflow works its fey magic
 * and everything is OK. */
static inline int
add_counter_to_entry(struct ip6t_entry *e,
                     const struct xt_counters addme[],
                     unsigned int *i)
{
#if 0
        duprintf("add_counter: Entry %u %lu/%lu + %lu/%lu\n",
                 *i,
                 (long unsigned int)e->counters.pcnt,
                 (long unsigned int)e->counters.bcnt,
                 (long unsigned int)addme[*i].pcnt,
                 (long unsigned int)addme[*i].bcnt);
#endif

        ADD_COUNTER(e->counters, addme[*i].bcnt, addme[*i].pcnt);

        (*i)++;
        return 0;
}

static int
do_add_counters(void __user *user, unsigned int len)
{
        unsigned int i;
        struct xt_counters_info tmp, *paddc;
        struct xt_table_info *private;
        struct xt_table *t;
        int ret = 0;
        void *loc_cpu_entry;

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

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

        paddc = vmalloc(len);
        if (!paddc)
                return -ENOMEM;

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

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

        write_lock_bh(&t->lock);
        private = t->private;
        if (private->number != tmp.num_counters) {
                ret = -EINVAL;
                goto unlock_up_free;
        }

        i = 0;
        /* Choose the copy that is on our node */
        loc_cpu_entry = private->entries[smp_processor_id()];
        IP6T_ENTRY_ITERATE(loc_cpu_entry,
                          private->size,
                          add_counter_to_entry,
                          paddc->counters,
                          &i);
 unlock_up_free:
        write_unlock_bh(&t->lock);
        xt_table_unlock(t);
        module_put(t->me);
 free:
        vfree(paddc);

        return ret;
}

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(user, len);
                break;

        case IP6T_SO_SET_ADD_COUNTERS:
                ret = do_add_counters(user, len);
                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: {
                char name[IP6T_TABLE_MAXNAMELEN];
                struct xt_table *t;

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

                if (copy_from_user(name, user, sizeof(name)) != 0) {
                        ret = -EFAULT;
                        break;
                }
                name[IP6T_TABLE_MAXNAMELEN-1] = '\0';

                t = try_then_request_module(xt_find_table_lock(AF_INET6, name),
                                            "ip6table_%s", name);
                if (t && !IS_ERR(t)) {
                        struct ip6t_getinfo info;
                        struct xt_table_info *private = t->private;

                        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;
                        memcpy(info.name, name, sizeof(info.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;
        }
        break;

        case IP6T_SO_GET_ENTRIES: {
                struct ip6t_get_entries get;

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

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

        newinfo = xt_alloc_table_info(repl->size);
        if (!newinfo)
                return -ENOMEM;

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

        ret = translate_table(table->name, table->valid_hooks,
                              newinfo, loc_cpu_entry, repl->size,
                              repl->num_entries,
                              repl->hook_entry,
                              repl->underflow);
        if (ret != 0) {
                xt_free_table_info(newinfo);
                return ret;
        }

        ret = xt_register_table(table, &bootstrap, newinfo);
        if (ret != 0) {
                xt_free_table_info(newinfo);
                return ret;
        }

        return 0;
}

void ip6t_unregister_table(struct xt_table *table)
{
        struct xt_table_info *private;
        void *loc_cpu_entry;

        private = xt_unregister_table(table);

        /* Decrease module usage counts and free resources */
        loc_cpu_entry = private->entries[raw_smp_processor_id()];
        IP6T_ENTRY_ITERATE(loc_cpu_entry, private->size, cleanup_entry, NULL);
        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 net_device *in,
           const struct net_device *out,
           const struct xt_match *match,
           const void *matchinfo,
           int offset,
           unsigned int protoff,
           bool *hotdrop)
{
        struct icmp6hdr _icmp, *ic;
        const struct ip6t_icmp *icmpinfo = matchinfo;

        /* Must not be a fragment. */
        if (offset)
                return false;

        ic = skb_header_pointer(skb, protoff, sizeof(_icmp), &_icmp);
        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");
                *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 char *tablename,
           const void *entry,
           const struct xt_match *match,
           void *matchinfo,
           unsigned int hook_mask)
{
        const struct ip6t_icmp *icmpinfo = 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         = AF_INET6,
};

static struct xt_target ip6t_error_target __read_mostly = {
        .name           = IP6T_ERROR_TARGET,
        .target         = ip6t_error,
        .targetsize     = IP6T_FUNCTION_MAXNAMELEN,
        .family         = AF_INET6,
};

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,
        .get_optmin     = IP6T_BASE_CTL,
        .get_optmax     = IP6T_SO_GET_MAX+1,
        .get            = do_ip6t_get_ctl,
        .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         = AF_INET6,
};

static int __init ip6_tables_init(void)
{
        int ret;

        ret = xt_proto_init(AF_INET6);
        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:
        xt_proto_fini(AF_INET6);
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);
        xt_proto_fini(AF_INET6);
}

/*
 * 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);