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arp_tables.c

/*
 * Packet matching code for ARP packets.
 *
 * Based heavily, if not almost entirely, upon ip_tables.c framework.
 *
 * Some ARP specific bits are:
 *
 * Copyright (C) 2002 David S. Miller (davem@redhat.com)
 *
 */

#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/capability.h>
#include <linux/if_arp.h>
#include <linux/kmod.h>
#include <linux/vmalloc.h>
#include <linux/proc_fs.h>
#include <linux/module.h>
#include <linux/init.h>

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

#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_arp/arp_tables.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("David S. Miller <davem@redhat.com>");
MODULE_DESCRIPTION("arptables core");

/*#define DEBUG_ARP_TABLES*/
/*#define DEBUG_ARP_TABLES_USER*/

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

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

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

static inline int arp_devaddr_compare(const struct arpt_devaddr_info *ap,
                              char *hdr_addr, int len)
{
      int i, ret;

      if (len > ARPT_DEV_ADDR_LEN_MAX)
            len = ARPT_DEV_ADDR_LEN_MAX;

      ret = 0;
      for (i = 0; i < len; i++)
            ret |= (hdr_addr[i] ^ ap->addr[i]) & ap->mask[i];

      return (ret != 0);
}

/* Returns whether packet matches rule or not. */
static inline int arp_packet_match(const struct arphdr *arphdr,
                           struct net_device *dev,
                           const char *indev,
                           const char *outdev,
                           const struct arpt_arp *arpinfo)
{
      char *arpptr = (char *)(arphdr + 1);
      char *src_devaddr, *tgt_devaddr;
      __be32 src_ipaddr, tgt_ipaddr;
      int i, ret;

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

      if (FWINV((arphdr->ar_op & arpinfo->arpop_mask) != arpinfo->arpop,
              ARPT_INV_ARPOP)) {
            dprintf("ARP operation field mismatch.\n");
            dprintf("ar_op: %04x info->arpop: %04x info->arpop_mask: %04x\n",
                  arphdr->ar_op, arpinfo->arpop, arpinfo->arpop_mask);
            return 0;
      }

      if (FWINV((arphdr->ar_hrd & arpinfo->arhrd_mask) != arpinfo->arhrd,
              ARPT_INV_ARPHRD)) {
            dprintf("ARP hardware address format mismatch.\n");
            dprintf("ar_hrd: %04x info->arhrd: %04x info->arhrd_mask: %04x\n",
                  arphdr->ar_hrd, arpinfo->arhrd, arpinfo->arhrd_mask);
            return 0;
      }

      if (FWINV((arphdr->ar_pro & arpinfo->arpro_mask) != arpinfo->arpro,
              ARPT_INV_ARPPRO)) {
            dprintf("ARP protocol address format mismatch.\n");
            dprintf("ar_pro: %04x info->arpro: %04x info->arpro_mask: %04x\n",
                  arphdr->ar_pro, arpinfo->arpro, arpinfo->arpro_mask);
            return 0;
      }

      if (FWINV((arphdr->ar_hln & arpinfo->arhln_mask) != arpinfo->arhln,
              ARPT_INV_ARPHLN)) {
            dprintf("ARP hardware address length mismatch.\n");
            dprintf("ar_hln: %02x info->arhln: %02x info->arhln_mask: %02x\n",
                  arphdr->ar_hln, arpinfo->arhln, arpinfo->arhln_mask);
            return 0;
      }

      src_devaddr = arpptr;
      arpptr += dev->addr_len;
      memcpy(&src_ipaddr, arpptr, sizeof(u32));
      arpptr += sizeof(u32);
      tgt_devaddr = arpptr;
      arpptr += dev->addr_len;
      memcpy(&tgt_ipaddr, arpptr, sizeof(u32));

      if (FWINV(arp_devaddr_compare(&arpinfo->src_devaddr, src_devaddr, dev->addr_len),
              ARPT_INV_SRCDEVADDR) ||
          FWINV(arp_devaddr_compare(&arpinfo->tgt_devaddr, tgt_devaddr, dev->addr_len),
              ARPT_INV_TGTDEVADDR)) {
            dprintf("Source or target device address mismatch.\n");

            return 0;
      }

      if (FWINV((src_ipaddr & arpinfo->smsk.s_addr) != arpinfo->src.s_addr,
              ARPT_INV_SRCIP) ||
          FWINV(((tgt_ipaddr & arpinfo->tmsk.s_addr) != arpinfo->tgt.s_addr),
              ARPT_INV_TGTIP)) {
            dprintf("Source or target IP address mismatch.\n");

            dprintf("SRC: %u.%u.%u.%u. Mask: %u.%u.%u.%u. Target: %u.%u.%u.%u.%s\n",
                  NIPQUAD(src_ipaddr),
                  NIPQUAD(arpinfo->smsk.s_addr),
                  NIPQUAD(arpinfo->src.s_addr),
                  arpinfo->invflags & ARPT_INV_SRCIP ? " (INV)" : "");
            dprintf("TGT: %u.%u.%u.%u Mask: %u.%u.%u.%u Target: %u.%u.%u.%u.%s\n",
                  NIPQUAD(tgt_ipaddr),
                  NIPQUAD(arpinfo->tmsk.s_addr),
                  NIPQUAD(arpinfo->tgt.s_addr),
                  arpinfo->invflags & ARPT_INV_TGTIP ? " (INV)" : "");
            return 0;
      }

      /* Look for ifname matches.  */
      for (i = 0, ret = 0; i < IFNAMSIZ; i++) {
            ret |= (indev[i] ^ arpinfo->iniface[i])
                  & arpinfo->iniface_mask[i];
      }

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

      for (i = 0, ret = 0; i < IFNAMSIZ; i++) {
            ret |= (outdev[i] ^ arpinfo->outiface[i])
                  & arpinfo->outiface_mask[i];
      }

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

      return 1;
}

static inline int arp_checkentry(const struct arpt_arp *arp)
{
      if (arp->flags & ~ARPT_F_MASK) {
            duprintf("Unknown flag bits set: %08X\n",
                   arp->flags & ~ARPT_F_MASK);
            return 0;
      }
      if (arp->invflags & ~ARPT_INV_MASK) {
            duprintf("Unknown invflag bits set: %08X\n",
                   arp->invflags & ~ARPT_INV_MASK);
            return 0;
      }

      return 1;
}

static unsigned int arpt_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("arp_tables: error: '%s'\n", (char *)targinfo);

      return NF_DROP;
}

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

unsigned int arpt_do_table(struct sk_buff *skb,
                     unsigned int hook,
                     const struct net_device *in,
                     const struct net_device *out,
                     struct arpt_table *table)
{
      static const char nulldevname[IFNAMSIZ];
      unsigned int verdict = NF_DROP;
      struct arphdr *arp;
      bool hotdrop = false;
      struct arpt_entry *e, *back;
      const char *indev, *outdev;
      void *table_base;
      struct xt_table_info *private;

      /* ARP header, plus 2 device addresses, plus 2 IP addresses.  */
      if (!pskb_may_pull(skb, (sizeof(struct arphdr) +
                         (2 * skb->dev->addr_len) +
                         (2 * sizeof(u32)))))
            return NF_DROP;

      indev = in ? in->name : nulldevname;
      outdev = out ? out->name : nulldevname;

      read_lock_bh(&table->lock);
      private = table->private;
      table_base = (void *)private->entries[smp_processor_id()];
      e = get_entry(table_base, private->hook_entry[hook]);
      back = get_entry(table_base, private->underflow[hook]);

      arp = arp_hdr(skb);
      do {
            if (arp_packet_match(arp, skb->dev, indev, outdev, &e->arp)) {
                  struct arpt_entry_target *t;
                  int hdr_len;

                  hdr_len = sizeof(*arp) + (2 * sizeof(struct in_addr)) +
                        (2 * skb->dev->addr_len);
                  ADD_COUNTER(e->counters, hdr_len, 1);

                  t = arpt_get_target(e);

                  /* Standard target? */
                  if (!t->u.kernel.target->target) {
                        int v;

                        v = ((struct arpt_standard_target *)t)->verdict;
                        if (v < 0) {
                              /* Pop from stack? */
                              if (v != ARPT_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) {
                              /* Save old back ptr in next entry */
                              struct arpt_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
                         */
                        verdict = t->u.kernel.target->target(skb,
                                                     in, out,
                                                     hook,
                                                     t->u.kernel.target,
                                                     t->data);

                        /* Target might have changed stuff. */
                        arp = arp_hdr(skb);

                        if (verdict == ARPT_CONTINUE)
                              e = (void *)e + e->next_offset;
                        else
                              /* Verdict */
                              break;
                  }
            } else {
                  e = (void *)e + e->next_offset;
            }
      } while (!hotdrop);
      read_unlock_bh(&table->lock);

      if (hotdrop)
            return NF_DROP;
      else
            return verdict;
}

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

      for (i = 0; i < sizeof(*arp)/sizeof(__u32); i++)
            if (((__u32 *)arp)[i])
                  return 0;

      return 1;
}

/* 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_ARP_NUMHOOKS; hook++) {
            unsigned int pos = newinfo->hook_entry[hook];
            struct arpt_entry *e
                  = (struct arpt_entry *)(entry0 + pos);

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

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

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

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

                  /* Unconditional return/END. */
                  if ((e->target_offset == sizeof(struct arpt_entry)
                      && (strcmp(t->target.u.user.name,
                               ARPT_STANDARD_TARGET) == 0)
                      && t->verdict < 0
                      && unconditional(&e->arp)) || 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_ARP_NUMHOOKS);
                              oldpos = pos;
                              pos = e->counters.pcnt;
                              e->counters.pcnt = 0;

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

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

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

                        if (strcmp(t->target.u.user.name,
                                 ARPT_STANDARD_TARGET) == 0
                            && newpos >= 0) {
                              if (newpos > newinfo->size -
                                    sizeof(struct arpt_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 arpt_entry *)
                              (entry0 + newpos);
                        e->counters.pcnt = pos;
                        pos = newpos;
                  }
            }
            next:
            duprintf("Finished chain %u\n", hook);
      }
      return 1;
}

static inline int standard_check(const struct arpt_entry_target *t,
                         unsigned int max_offset)
{
      /* Check standard info. */
      if (t->u.target_size
          != ARPT_ALIGN(sizeof(struct arpt_standard_target))) {
            duprintf("arpt_standard_check: target size %u != %Zu\n",
                   t->u.target_size,
                   ARPT_ALIGN(sizeof(struct arpt_standard_target)));
            return 0;
      }

      return 1;
}

static struct arpt_target arpt_standard_target;

static inline int check_entry(struct arpt_entry *e, const char *name, unsigned int size,
                        unsigned int *i)
{
      struct arpt_entry_target *t;
      struct arpt_target *target;
      int ret;

      if (!arp_checkentry(&e->arp)) {
            duprintf("arp_tables: arp check failed %p %s.\n", e, name);
            return -EINVAL;
      }

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

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

      target = try_then_request_module(xt_find_target(NF_ARP, t->u.user.name,
                                          t->u.user.revision),
                               "arpt_%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 out;
      }
      t->u.kernel.target = target;

      ret = xt_check_target(target, NF_ARP, t->u.target_size - sizeof(*t),
                        name, e->comefrom, 0, 0);
      if (ret)
            goto err;

      if (t->u.kernel.target == &arpt_standard_target) {
            if (!standard_check(t, size)) {
                  ret = -EINVAL;
                  goto err;
            }
      } else if (t->u.kernel.target->checkentry
               && !t->u.kernel.target->checkentry(name, e, target, t->data,
                                          e->comefrom)) {
            duprintf("arp_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);
out:
      return ret;
}

static inline int check_entry_size_and_hooks(struct arpt_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 arpt_entry) != 0
          || (unsigned char *)e + sizeof(struct arpt_entry) >= limit) {
            duprintf("Bad offset %p\n", e);
            return -EINVAL;
      }

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

      /* Check hooks & underflows */
      for (h = 0; h < NF_ARP_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 ARPT_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 arpt_entry *e, unsigned int *i)
{
      struct arpt_entry_target *t;

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

      t = arpt_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_ARP_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 = ARPT_ENTRY_ITERATE(entry0, newinfo->size,
                         check_entry_size_and_hooks,
                         newinfo,
                         entry0,
                         entry0 + size,
                         hook_entries, underflows, &i);
      duprintf("translate_table: ARPT_ENTRY_ITERATE gives %d\n", ret);
      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_ARP_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)) {
            duprintf("Looping hook\n");
            return -ELOOP;
      }

      /* Finally, each sanity check must pass */
      i = 0;
      ret = ARPT_ENTRY_ITERATE(entry0, newinfo->size,
                         check_entry, name, size, &i);

      if (ret != 0) {
            ARPT_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 ret;
}

/* Gets counters. */
static inline int add_entry_to_counter(const struct arpt_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 arpt_entry *e,
                               struct xt_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;
      ARPT_ENTRY_ITERATE(t->entries[curcpu],
                     t->size,
                     set_entry_to_counter,
                     counters,
                     &i);

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

static int copy_entries_to_user(unsigned int total_size,
                        struct arpt_table *table,
                        void __user *userptr)
{
      unsigned int off, num, countersize;
      struct arpt_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_node(countersize, numa_node_id());

      if (counters == NULL)
            return -ENOMEM;

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

      loc_cpu_entry = private->entries[raw_smp_processor_id()];
      /* ... then copy entire thing ... */
      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++){
            struct arpt_entry_target *t;

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

            t = arpt_get_target(e);
            if (copy_to_user(userptr + off + e->target_offset
                         + offsetof(struct arpt_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 arpt_get_entries *entries,
                   struct arpt_get_entries __user *uptr)
{
      int ret;
      struct arpt_table *t;

      t = xt_find_table_lock(NF_ARP, 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 arpt_replace tmp;
      struct arpt_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;

      /* Hack: Causes ipchains to give correct error msg --RR */
      if (len != sizeof(tmp) + tmp.size)
            return -ENOPROTOOPT;

      /* 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("arp_tables: Translated table\n");

      t = try_then_request_module(xt_find_table_lock(NF_ARP, tmp.name),
                            "arptable_%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()];
      ARPT_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:
      ARPT_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 arpt_entry *e,
                               const struct xt_counters addme[],
                               unsigned int *i)
{

      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 arpt_table *t;
      struct xt_table_info *private;
      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(NF_ARP, 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()];
      ARPT_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_arpt_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 ARPT_SO_SET_REPLACE:
            ret = do_replace(user, len);
            break;

      case ARPT_SO_SET_ADD_COUNTERS:
            ret = do_add_counters(user, len);
            break;

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

      return ret;
}

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

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

      switch (cmd) {
      case ARPT_SO_GET_INFO: {
            char name[ARPT_TABLE_MAXNAMELEN];
            struct arpt_table *t;

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

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

            t = try_then_request_module(xt_find_table_lock(NF_ARP, name),
                                  "arptable_%s", name);
            if (t && !IS_ERR(t)) {
                  struct arpt_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;
                  strcpy(info.name, name);

                  if (copy_to_user(user, &info, *len) != 0)
                        ret = -EFAULT;
                  else
                        ret = 0;
                  xt_table_unlock(t);
                  module_put(t->me);
            } else
                  ret = t ? PTR_ERR(t) : -ENOENT;
      }
      break;

      case ARPT_SO_GET_ENTRIES: {
            struct arpt_get_entries get;

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

      case ARPT_SO_GET_REVISION_TARGET: {
            struct xt_get_revision rev;

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

            try_then_request_module(xt_find_revision(NF_ARP, rev.name,
                                           rev.revision, 1, &ret),
                              "arpt_%s", rev.name);
            break;
      }

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

      return ret;
}

int arpt_register_table(struct arpt_table *table,
                  const struct arpt_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) {
            ret = -ENOMEM;
            return ret;
      }

      /* 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);

      duprintf("arpt_register_table: translate table gives %d\n", ret);
      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 arpt_unregister_table(struct arpt_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()];
      ARPT_ENTRY_ITERATE(loc_cpu_entry, private->size,
                     cleanup_entry, NULL);
      xt_free_table_info(private);
}

/* The built-in targets: standard (NULL) and error. */
static struct arpt_target arpt_standard_target __read_mostly = {
      .name       = ARPT_STANDARD_TARGET,
      .targetsize = sizeof(int),
      .family           = NF_ARP,
};

static struct arpt_target arpt_error_target __read_mostly = {
      .name       = ARPT_ERROR_TARGET,
      .target           = arpt_error,
      .targetsize = ARPT_FUNCTION_MAXNAMELEN,
      .family           = NF_ARP,
};

static struct nf_sockopt_ops arpt_sockopts = {
      .pf         = PF_INET,
      .set_optmin = ARPT_BASE_CTL,
      .set_optmax = ARPT_SO_SET_MAX+1,
      .set        = do_arpt_set_ctl,
      .get_optmin = ARPT_BASE_CTL,
      .get_optmax = ARPT_SO_GET_MAX+1,
      .get        = do_arpt_get_ctl,
      .owner            = THIS_MODULE,
};

static int __init arp_tables_init(void)
{
      int ret;

      ret = xt_proto_init(NF_ARP);
      if (ret < 0)
            goto err1;

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

      /* Register setsockopt */
      ret = nf_register_sockopt(&arpt_sockopts);
      if (ret < 0)
            goto err4;

      printk(KERN_INFO "arp_tables: (C) 2002 David S. Miller\n");
      return 0;

err4:
      xt_unregister_target(&arpt_error_target);
err3:
      xt_unregister_target(&arpt_standard_target);
err2:
      xt_proto_fini(NF_ARP);
err1:
      return ret;
}

static void __exit arp_tables_fini(void)
{
      nf_unregister_sockopt(&arpt_sockopts);
      xt_unregister_target(&arpt_error_target);
      xt_unregister_target(&arpt_standard_target);
      xt_proto_fini(NF_ARP);
}

EXPORT_SYMBOL(arpt_register_table);
EXPORT_SYMBOL(arpt_unregister_table);
EXPORT_SYMBOL(arpt_do_table);

module_init(arp_tables_init);
module_exit(arp_tables_fini);

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