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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_IP6_PRE_ROUTING]          = "PREROUTING",
      [NF_IP6_LOCAL_IN]       = "INPUT",
      [NF_IP6_FORWARD]        = "FORWARD",
      [NF_IP6_LOCAL_OUT]            = "OUTPUT",
      [NF_IP6_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_IP6_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_IP6_NUMHOOKS)) {
                        printk("iptables: loop hook %u pos %u %08X.\n",
                               hook, pos, e->comefrom);
                        return 0;
                  }
                  e->comefrom
                        |= ((1 << hook) | (1 << NF_IP6_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_IP6_NUMHOOKS);
#ifdef DEBUG_IP_FIREWALL_USER
                              if (e->comefrom
                                  & (1 << NF_IP6_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_IP6_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_IP6_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_IP6_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);

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