net/bridge/netfilter/ebtables.c

/*
 *  ebtables
 *
 *  Author:
 *  Bart De Schuymer		<bdschuym@pandora.be>
 *
 *  ebtables.c,v 2.0, July, 2002
 *
 *  This code is stongly inspired on the iptables code which is
 *  Copyright (C) 1999 Paul `Rusty' Russell & Michael J. Neuling
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version
 *  2 of the License, or (at your option) any later version.
 */


#include <linux/kmod.h>
#include <linux/module.h>
#include <linux/vmalloc.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_bridge/ebtables.h>
#include <linux/spinlock.h>
#include <linux/mutex.h>
#include <asm/uaccess.h>
#include <linux/smp.h>
#include <linux/cpumask.h>
#include <net/sock.h>
/* needed for logical [in,out]-dev filtering */
#include "../br_private.h"

#define BUGPRINT(format, args...) printk("kernel msg: ebtables bug: please "\
					 "report to author: "format, ## args)
/* #define BUGPRINT(format, args...) */
#define MEMPRINT(format, args...) printk("kernel msg: ebtables "\
					 ": out of memory: "format, ## args)
/* #define MEMPRINT(format, args...) */



/*
 * Each cpu has its own set of counters, so there is no need for write_lock in
 * the softirq
 * For reading or updating the counters, the user context needs to
 * get a write_lock
 */

/* The size of each set of counters is altered to get cache alignment */
#define SMP_ALIGN(x) (((x) + SMP_CACHE_BYTES-1) & ~(SMP_CACHE_BYTES-1))
#define COUNTER_OFFSET(n) (SMP_ALIGN(n * sizeof(struct ebt_counter)))
#define COUNTER_BASE(c, n, cpu) ((struct ebt_counter *)(((char *)c) + \
   COUNTER_OFFSET(n) * cpu))



static DEFINE_MUTEX(ebt_mutex);
static LIST_HEAD(ebt_tables);

static struct xt_target ebt_standard_target = {
	.name       = "standard",
	.revision   = 0,
	.family     = NFPROTO_BRIDGE,
	.targetsize = sizeof(int),
};

static inline int
ebt_do_watcher(const struct ebt_entry_watcher *w, struct sk_buff *skb,
	       struct xt_target_param *par)
{
	par->target   = w->u.watcher;
	par->targinfo = w->data;
	w->u.watcher->target(skb, par);
	/* watchers don't give a verdict */
	return 0;
}

static inline int ebt_do_match (struct ebt_entry_match *m,
   const struct sk_buff *skb, struct xt_match_param *par)
{
	par->match     = m->u.match;
	par->matchinfo = m->data;
	return m->u.match->match(skb, par);
}

static inline int ebt_dev_check(char *entry, const struct net_device *device)
{
	int i = 0;
	const char *devname = device->name;

	if (*entry == '\0')
		return 0;
	if (!device)
		return 1;
	/* 1 is the wildcard token */
	while (entry[i] != '\0' && entry[i] != 1 && entry[i] == devname[i])
		i++;
	return (devname[i] != entry[i] && entry[i] != 1);
}

#define FWINV2(bool,invflg) ((bool) ^ !!(e->invflags & invflg))
/* process standard matches */
static inline int ebt_basic_match(struct ebt_entry *e, struct ethhdr *h,
   const struct net_device *in, const struct net_device *out)
{
	int verdict, i;

	if (e->bitmask & EBT_802_3) {
		if (FWINV2(ntohs(h->h_proto) >= 1536, EBT_IPROTO))
			return 1;
	} else if (!(e->bitmask & EBT_NOPROTO) &&
	   FWINV2(e->ethproto != h->h_proto, EBT_IPROTO))
		return 1;

	if (FWINV2(ebt_dev_check(e->in, in), EBT_IIN))
		return 1;
	if (FWINV2(ebt_dev_check(e->out, out), EBT_IOUT))
		return 1;
	if ((!in || !in->br_port) ? 0 : FWINV2(ebt_dev_check(
	   e->logical_in, in->br_port->br->dev), EBT_ILOGICALIN))
		return 1;
	if ((!out || !out->br_port) ? 0 : FWINV2(ebt_dev_check(
	   e->logical_out, out->br_port->br->dev), EBT_ILOGICALOUT))
		return 1;

	if (e->bitmask & EBT_SOURCEMAC) {
		verdict = 0;
		for (i = 0; i < 6; i++)
			verdict |= (h->h_source[i] ^ e->sourcemac[i]) &
			   e->sourcemsk[i];
		if (FWINV2(verdict != 0, EBT_ISOURCE) )
			return 1;
	}
	if (e->bitmask & EBT_DESTMAC) {
		verdict = 0;
		for (i = 0; i < 6; i++)
			verdict |= (h->h_dest[i] ^ e->destmac[i]) &
			   e->destmsk[i];
		if (FWINV2(verdict != 0, EBT_IDEST) )
			return 1;
	}
	return 0;
}

/* Do some firewalling */
unsigned int ebt_do_table (unsigned int hook, struct sk_buff *skb,
   const struct net_device *in, const struct net_device *out,
   struct ebt_table *table)
{
	int i, nentries;
	struct ebt_entry *point;
	struct ebt_counter *counter_base, *cb_base;
	struct ebt_entry_target *t;
	int verdict, sp = 0;
	struct ebt_chainstack *cs;
	struct ebt_entries *chaininfo;
	char *base;
	struct ebt_table_info *private;
	bool hotdrop = false;
	struct xt_match_param mtpar;
	struct xt_target_param tgpar;

	mtpar.family  = tgpar.family = NFPROTO_BRIDGE;
	mtpar.in      = tgpar.in  = in;
	mtpar.out     = tgpar.out = out;
	mtpar.hotdrop = &hotdrop;
	tgpar.hooknum = hook;

	read_lock_bh(&table->lock);
	private = table->private;
	cb_base = COUNTER_BASE(private->counters, private->nentries,
	   smp_processor_id());
	if (private->chainstack)
		cs = private->chainstack[smp_processor_id()];
	else
		cs = NULL;
	chaininfo = private->hook_entry[hook];
	nentries = private->hook_entry[hook]->nentries;
	point = (struct ebt_entry *)(private->hook_entry[hook]->data);
	counter_base = cb_base + private->hook_entry[hook]->counter_offset;
	/* base for chain jumps */
	base = private->entries;
	i = 0;
	while (i < nentries) {
		if (ebt_basic_match(point, eth_hdr(skb), in, out))
			goto letscontinue;

		if (EBT_MATCH_ITERATE(point, ebt_do_match, skb, &mtpar) != 0)
			goto letscontinue;
		if (hotdrop) {
			read_unlock_bh(&table->lock);
			return NF_DROP;
		}

		/* increase counter */
		(*(counter_base + i)).pcnt++;
		(*(counter_base + i)).bcnt += skb->len;

		/* these should only watch: not modify, nor tell us
		   what to do with the packet */
		EBT_WATCHER_ITERATE(point, ebt_do_watcher, skb, &tgpar);

		t = (struct ebt_entry_target *)
		   (((char *)point) + point->target_offset);
		/* standard target */
		if (!t->u.target->target)
			verdict = ((struct ebt_standard_target *)t)->verdict;
		else {
			tgpar.target   = t->u.target;
			tgpar.targinfo = t->data;
			verdict = t->u.target->target(skb, &tgpar);
		}
		if (verdict == EBT_ACCEPT) {
			read_unlock_bh(&table->lock);
			return NF_ACCEPT;
		}
		if (verdict == EBT_DROP) {
			read_unlock_bh(&table->lock);
			return NF_DROP;
		}
		if (verdict == EBT_RETURN) {
letsreturn:
#ifdef CONFIG_NETFILTER_DEBUG
			if (sp == 0) {
				BUGPRINT("RETURN on base chain");
				/* act like this is EBT_CONTINUE */
				goto letscontinue;
			}
#endif
			sp--;
			/* put all the local variables right */
			i = cs[sp].n;
			chaininfo = cs[sp].chaininfo;
			nentries = chaininfo->nentries;
			point = cs[sp].e;
			counter_base = cb_base +
			   chaininfo->counter_offset;
			continue;
		}
		if (verdict == EBT_CONTINUE)
			goto letscontinue;
#ifdef CONFIG_NETFILTER_DEBUG
		if (verdict < 0) {
			BUGPRINT("bogus standard verdict\n");
			read_unlock_bh(&table->lock);
			return NF_DROP;
		}
#endif
		/* jump to a udc */
		cs[sp].n = i + 1;
		cs[sp].chaininfo = chaininfo;
		cs[sp].e = (struct ebt_entry *)
		   (((char *)point) + point->next_offset);
		i = 0;
		chaininfo = (struct ebt_entries *) (base + verdict);
#ifdef CONFIG_NETFILTER_DEBUG
		if (chaininfo->distinguisher) {
			BUGPRINT("jump to non-chain\n");
			read_unlock_bh(&table->lock);
			return NF_DROP;
		}
#endif
		nentries = chaininfo->nentries;
		point = (struct ebt_entry *)chaininfo->data;
		counter_base = cb_base + chaininfo->counter_offset;
		sp++;
		continue;
letscontinue:
		point = (struct ebt_entry *)
		   (((char *)point) + point->next_offset);
		i++;
	}

	/* I actually like this :) */
	if (chaininfo->policy == EBT_RETURN)
		goto letsreturn;
	if (chaininfo->policy == EBT_ACCEPT) {
		read_unlock_bh(&table->lock);
		return NF_ACCEPT;
	}
	read_unlock_bh(&table->lock);
	return NF_DROP;
}

/* If it succeeds, returns element and locks mutex */
static inline void *
find_inlist_lock_noload(struct list_head *head, const char *name, int *error,
   struct mutex *mutex)
{
	struct {
		struct list_head list;
		char name[EBT_FUNCTION_MAXNAMELEN];
	} *e;

	*error = mutex_lock_interruptible(mutex);
	if (*error != 0)
		return NULL;

	list_for_each_entry(e, head, list) {
		if (strcmp(e->name, name) == 0)
			return e;
	}
	*error = -ENOENT;
	mutex_unlock(mutex);
	return NULL;
}

#ifndef CONFIG_KMOD
#define find_inlist_lock(h,n,p,e,m) find_inlist_lock_noload((h),(n),(e),(m))
#else
static void *
find_inlist_lock(struct list_head *head, const char *name, const char *prefix,
   int *error, struct mutex *mutex)
{
	void *ret;

	ret = find_inlist_lock_noload(head, name, error, mutex);
	if (!ret) {
		request_module("%s%s", prefix, name);
		ret = find_inlist_lock_noload(head, name, error, mutex);
	}
	return ret;
}
#endif

static inline struct ebt_table *
find_table_lock(const char *name, int *error, struct mutex *mutex)
{
	return find_inlist_lock(&ebt_tables, name, "ebtable_", error, mutex);
}

static inline int
ebt_check_match(struct ebt_entry_match *m, struct xt_mtchk_param *par,
		unsigned int *cnt)
{
	const struct ebt_entry *e = par->entryinfo;
	struct xt_match *match;
	size_t left = ((char *)e + e->watchers_offset) - (char *)m;
	int ret;

	if (left < sizeof(struct ebt_entry_match) ||
	    left - sizeof(struct ebt_entry_match) < m->match_size)
		return -EINVAL;

	match = try_then_request_module(xt_find_match(NFPROTO_BRIDGE,
		m->u.name, 0), "ebt_%s", m->u.name);
	if (IS_ERR(match))
		return PTR_ERR(match);
	if (match == NULL)
		return -ENOENT;
	m->u.match = match;

	par->match     = match;
	par->matchinfo = m->data;
	ret = xt_check_match(par, m->match_size,
	      e->ethproto, e->invflags & EBT_IPROTO);
	if (ret < 0) {
		module_put(match->me);
		return ret;
	}

	(*cnt)++;
	return 0;
}

static inline int
ebt_check_watcher(struct ebt_entry_watcher *w, struct xt_tgchk_param *par,
		  unsigned int *cnt)
{
	const struct ebt_entry *e = par->entryinfo;
	struct xt_target *watcher;
	size_t left = ((char *)e + e->target_offset) - (char *)w;
	int ret;

	if (left < sizeof(struct ebt_entry_watcher) ||
	   left - sizeof(struct ebt_entry_watcher) < w->watcher_size)
		return -EINVAL;

	watcher = try_then_request_module(
		  xt_find_target(NFPROTO_BRIDGE, w->u.name, 0),
		  "ebt_%s", w->u.name);
	if (IS_ERR(watcher))
		return PTR_ERR(watcher);
	if (watcher == NULL)
		return -ENOENT;
	w->u.watcher = watcher;

	par->target   = watcher;
	par->targinfo = w->data;
	ret = xt_check_target(par, w->watcher_size,
	      e->ethproto, e->invflags & EBT_IPROTO);
	if (ret < 0) {
		module_put(watcher->me);
		return ret;
	}

	(*cnt)++;
	return 0;
}

static int ebt_verify_pointers(struct ebt_replace *repl,
			       struct ebt_table_info *newinfo)
{
	unsigned int limit = repl->entries_size;
	unsigned int valid_hooks = repl->valid_hooks;
	unsigned int offset = 0;
	int i;

	for (i = 0; i < NF_BR_NUMHOOKS; i++)
		newinfo->hook_entry[i] = NULL;

	newinfo->entries_size = repl->entries_size;
	newinfo->nentries = repl->nentries;

	while (offset < limit) {
		size_t left = limit - offset;
		struct ebt_entry *e = (void *)newinfo->entries + offset;

		if (left < sizeof(unsigned int))
			break;

		for (i = 0; i < NF_BR_NUMHOOKS; i++) {
			if ((valid_hooks & (1 << i)) == 0)
				continue;
			if ((char __user *)repl->hook_entry[i] ==
			     repl->entries + offset)
				break;
		}

		if (i != NF_BR_NUMHOOKS || !(e->bitmask & EBT_ENTRY_OR_ENTRIES)) {
			if (e->bitmask != 0) {
				/* we make userspace set this right,
				   so there is no misunderstanding */
				BUGPRINT("EBT_ENTRY_OR_ENTRIES shouldn't be set "
					 "in distinguisher\n");
				return -EINVAL;
			}
			if (i != NF_BR_NUMHOOKS)
				newinfo->hook_entry[i] = (struct ebt_entries *)e;
			if (left < sizeof(struct ebt_entries))
				break;
			offset += sizeof(struct ebt_entries);
		} else {
			if (left < sizeof(struct ebt_entry))
				break;
			if (left < e->next_offset)
				break;
			offset += e->next_offset;
		}
	}
	if (offset != limit) {
		BUGPRINT("entries_size too small\n");
		return -EINVAL;
	}

	/* check if all valid hooks have a chain */
	for (i = 0; i < NF_BR_NUMHOOKS; i++) {
		if (!newinfo->hook_entry[i] &&
		   (valid_hooks & (1 << i))) {
			BUGPRINT("Valid hook without chain\n");
			return -EINVAL;
		}
	}
	return 0;
}

/*
 * this one is very careful, as it is the first function
 * to parse the userspace data
 */
static inline int
ebt_check_entry_size_and_hooks(struct ebt_entry *e,
   struct ebt_table_info *newinfo,
   unsigned int *n, unsigned int *cnt,
   unsigned int *totalcnt, unsigned int *udc_cnt)
{
	int i;

	for (i = 0; i < NF_BR_NUMHOOKS; i++) {
		if ((void *)e == (void *)newinfo->hook_entry[i])
			break;
	}
	/* beginning of a new chain
	   if i == NF_BR_NUMHOOKS it must be a user defined chain */
	if (i != NF_BR_NUMHOOKS || !e->bitmask) {
		/* this checks if the previous chain has as many entries
		   as it said it has */
		if (*n != *cnt) {
			BUGPRINT("nentries does not equal the nr of entries "
				 "in the chain\n");
			return -EINVAL;
		}
		if (((struct ebt_entries *)e)->policy != EBT_DROP &&
		   ((struct ebt_entries *)e)->policy != EBT_ACCEPT) {
			/* only RETURN from udc */
			if (i != NF_BR_NUMHOOKS ||
			   ((struct ebt_entries *)e)->policy != EBT_RETURN) {
				BUGPRINT("bad policy\n");
				return -EINVAL;
			}
		}
		if (i == NF_BR_NUMHOOKS) /* it's a user defined chain */
			(*udc_cnt)++;
		if (((struct ebt_entries *)e)->counter_offset != *totalcnt) {
			BUGPRINT("counter_offset != totalcnt");
			return -EINVAL;
		}
		*n = ((struct ebt_entries *)e)->nentries;
		*cnt = 0;
		return 0;
	}
	/* a plain old entry, heh */
	if (sizeof(struct ebt_entry) > e->watchers_offset ||
	   e->watchers_offset > e->target_offset ||
	   e->target_offset >= e->next_offset) {
		BUGPRINT("entry offsets not in right order\n");
		return -EINVAL;
	}
	/* this is not checked anywhere else */
	if (e->next_offset - e->target_offset < sizeof(struct ebt_entry_target)) {
		BUGPRINT("target size too small\n");
		return -EINVAL;
	}
	(*cnt)++;
	(*totalcnt)++;
	return 0;
}

struct ebt_cl_stack
{
	struct ebt_chainstack cs;
	int from;
	unsigned int hookmask;
};

/*
 * we need these positions to check that the jumps to a different part of the
 * entries is a jump to the beginning of a new chain.
 */
static inline int
ebt_get_udc_positions(struct ebt_entry *e, struct ebt_table_info *newinfo,
   unsigned int *n, struct ebt_cl_stack *udc)
{
	int i;

	/* we're only interested in chain starts */
	if (e->bitmask)
		return 0;
	for (i = 0; i < NF_BR_NUMHOOKS; i++) {
		if (newinfo->hook_entry[i] == (struct ebt_entries *)e)
			break;
	}
	/* only care about udc */
	if (i != NF_BR_NUMHOOKS)
		return 0;

	udc[*n].cs.chaininfo = (struct ebt_entries *)e;
	/* these initialisations are depended on later in check_chainloops() */
	udc[*n].cs.n = 0;
	udc[*n].hookmask = 0;

	(*n)++;
	return 0;
}

static inline int
ebt_cleanup_match(struct ebt_entry_match *m, unsigned int *i)
{
	struct xt_mtdtor_param par;

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

	par.match     = m->u.match;
	par.matchinfo = m->data;
	par.family    = NFPROTO_BRIDGE;
	if (par.match->destroy != NULL)
		par.match->destroy(&par);
	module_put(par.match->me);
	return 0;
}

static inline int
ebt_cleanup_watcher(struct ebt_entry_watcher *w, unsigned int *i)
{
	struct xt_tgdtor_param par;

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

	par.target   = w->u.watcher;
	par.targinfo = w->data;
	par.family   = NFPROTO_BRIDGE;
	if (par.target->destroy != NULL)
		par.target->destroy(&par);
	module_put(par.target->me);
	return 0;
}

static inline int
ebt_cleanup_entry(struct ebt_entry *e, unsigned int *cnt)
{
	struct xt_tgdtor_param par;
	struct ebt_entry_target *t;

	if (e->bitmask == 0)
		return 0;
	/* we're done */
	if (cnt && (*cnt)-- == 0)
		return 1;
	EBT_WATCHER_ITERATE(e, ebt_cleanup_watcher, NULL);
	EBT_MATCH_ITERATE(e, ebt_cleanup_match, NULL);
	t = (struct ebt_entry_target *)(((char *)e) + e->target_offset);

	par.target   = t->u.target;
	par.targinfo = t->data;
	par.family   = NFPROTO_BRIDGE;
	if (par.target->destroy != NULL)
		par.target->destroy(&par);
	module_put(par.target->me);
	return 0;
}

static inline int
ebt_check_entry(struct ebt_entry *e, struct ebt_table_info *newinfo,
   const char *name, unsigned int *cnt,
   struct ebt_cl_stack *cl_s, unsigned int udc_cnt)
{
	struct ebt_entry_target *t;
	struct xt_target *target;
	unsigned int i, j, hook = 0, hookmask = 0;
	size_t gap;
	int ret;
	struct xt_mtchk_param mtpar;
	struct xt_tgchk_param tgpar;

	/* don't mess with the struct ebt_entries */
	if (e->bitmask == 0)
		return 0;

	if (e->bitmask & ~EBT_F_MASK) {
		BUGPRINT("Unknown flag for bitmask\n");
		return -EINVAL;
	}
	if (e->invflags & ~EBT_INV_MASK) {
		BUGPRINT("Unknown flag for inv bitmask\n");
		return -EINVAL;
	}
	if ( (e->bitmask & EBT_NOPROTO) && (e->bitmask & EBT_802_3) ) {
		BUGPRINT("NOPROTO & 802_3 not allowed\n");
		return -EINVAL;
	}
	/* what hook do we belong to? */
	for (i = 0; i < NF_BR_NUMHOOKS; i++) {
		if (!newinfo->hook_entry[i])
			continue;
		if ((char *)newinfo->hook_entry[i] < (char *)e)
			hook = i;
		else
			break;
	}
	/* (1 << NF_BR_NUMHOOKS) tells the check functions the rule is on
	   a base chain */
	if (i < NF_BR_NUMHOOKS)
		hookmask = (1 << hook) | (1 << NF_BR_NUMHOOKS);
	else {
		for (i = 0; i < udc_cnt; i++)
			if ((char *)(cl_s[i].cs.chaininfo) > (char *)e)
				break;
		if (i == 0)
			hookmask = (1 << hook) | (1 << NF_BR_NUMHOOKS);
		else
			hookmask = cl_s[i - 1].hookmask;
	}
	i = 0;

	mtpar.table     = tgpar.table     = name;
	mtpar.entryinfo = tgpar.entryinfo = e;
	mtpar.hook_mask = tgpar.hook_mask = hookmask;
	mtpar.family    = tgpar.family    = NFPROTO_BRIDGE;
	ret = EBT_MATCH_ITERATE(e, ebt_check_match, &mtpar, &i);
	if (ret != 0)
		goto cleanup_matches;
	j = 0;
	ret = EBT_WATCHER_ITERATE(e, ebt_check_watcher, &tgpar, &j);
	if (ret != 0)
		goto cleanup_watchers;
	t = (struct ebt_entry_target *)(((char *)e) + e->target_offset);
	gap = e->next_offset - e->target_offset;

	target = try_then_request_module(
		 xt_find_target(NFPROTO_BRIDGE, t->u.name, 0),
		 "ebt_%s", t->u.name);
	if (IS_ERR(target)) {
		ret = PTR_ERR(target);
		goto cleanup_watchers;
	} else if (target == NULL) {
		ret = -ENOENT;
		goto cleanup_watchers;
	}

	t->u.target = target;
	if (t->u.target == &ebt_standard_target) {
		if (gap < sizeof(struct ebt_standard_target)) {
			BUGPRINT("Standard target size too big\n");
			ret = -EFAULT;
			goto cleanup_watchers;
		}
		if (((struct ebt_standard_target *)t)->verdict <
		   -NUM_STANDARD_TARGETS) {
			BUGPRINT("Invalid standard target\n");
			ret = -EFAULT;
			goto cleanup_watchers;
		}
	} else if (t->target_size > gap - sizeof(struct ebt_entry_target)) {
		module_put(t->u.target->me);
		ret = -EFAULT;
		goto cleanup_watchers;
	}

	tgpar.target   = target;
	tgpar.targinfo = t->data;
	ret = xt_check_target(&tgpar, t->target_size,
	      e->ethproto, e->invflags & EBT_IPROTO);
	if (ret < 0) {
		module_put(target->me);
		goto cleanup_watchers;
	}
	(*cnt)++;
	return 0;
cleanup_watchers:
	EBT_WATCHER_ITERATE(e, ebt_cleanup_watcher, &j);
cleanup_matches:
	EBT_MATCH_ITERATE(e, ebt_cleanup_match, &i);
	return ret;
}

/*
 * checks for loops and sets the hook mask for udc
 * the hook mask for udc tells us from which base chains the udc can be
 * accessed. This mask is a parameter to the check() functions of the extensions
 */
static int check_chainloops(struct ebt_entries *chain, struct ebt_cl_stack *cl_s,
   unsigned int udc_cnt, unsigned int hooknr, char *base)
{
	int i, chain_nr = -1, pos = 0, nentries = chain->nentries, verdict;
	struct ebt_entry *e = (struct ebt_entry *)chain->data;
	struct ebt_entry_target *t;

	while (pos < nentries || chain_nr != -1) {
		/* end of udc, go back one 'recursion' step */
		if (pos == nentries) {
			/* put back values of the time when this chain was called */
			e = cl_s[chain_nr].cs.e;
			if (cl_s[chain_nr].from != -1)
				nentries =
				cl_s[cl_s[chain_nr].from].cs.chaininfo->nentries;
			else
				nentries = chain->nentries;
			pos = cl_s[chain_nr].cs.n;
			/* make sure we won't see a loop that isn't one */
			cl_s[chain_nr].cs.n = 0;
			chain_nr = cl_s[chain_nr].from;
			if (pos == nentries)
				continue;
		}
		t = (struct ebt_entry_target *)
		   (((char *)e) + e->target_offset);
		if (strcmp(t->u.name, EBT_STANDARD_TARGET))
			goto letscontinue;
		if (e->target_offset + sizeof(struct ebt_standard_target) >
		   e->next_offset) {
			BUGPRINT("Standard target size too big\n");
			return -1;
		}
		verdict = ((struct ebt_standard_target *)t)->verdict;
		if (verdict >= 0) { /* jump to another chain */
			struct ebt_entries *hlp2 =
			   (struct ebt_entries *)(base + verdict);
			for (i = 0; i < udc_cnt; i++)
				if (hlp2 == cl_s[i].cs.chaininfo)
					break;
			/* bad destination or loop */
			if (i == udc_cnt) {
				BUGPRINT("bad destination\n");
				return -1;
			}
			if (cl_s[i].cs.n) {
				BUGPRINT("loop\n");
				return -1;
			}
			if (cl_s[i].hookmask & (1 << hooknr))
				goto letscontinue;
			/* this can't be 0, so the loop test is correct */
			cl_s[i].cs.n = pos + 1;
			pos = 0;
			cl_s[i].cs.e = ((void *)e + e->next_offset);
			e = (struct ebt_entry *)(hlp2->data);
			nentries = hlp2->nentries;
			cl_s[i].from = chain_nr;
			chain_nr = i;
			/* this udc is accessible from the base chain for hooknr */
			cl_s[i].hookmask |= (1 << hooknr);
			continue;
		}
letscontinue:
		e = (void *)e + e->next_offset;
		pos++;
	}
	return 0;
}

/* do the parsing of the table/chains/entries/matches/watchers/targets, heh */
static int translate_table(char *name, struct ebt_table_info *newinfo)
{
	unsigned int i, j, k, udc_cnt;
	int ret;
	struct ebt_cl_stack *cl_s = NULL; /* used in the checking for chain loops */

	i = 0;
	while (i < NF_BR_NUMHOOKS && !newinfo->hook_entry[i])
		i++;
	if (i == NF_BR_NUMHOOKS) {
		BUGPRINT("No valid hooks specified\n");
		return -EINVAL;
	}
	if (newinfo->hook_entry[i] != (struct ebt_entries *)newinfo->entries) {
		BUGPRINT("Chains don't start at beginning\n");
		return -EINVAL;
	}
	/* make sure chains are ordered after each other in same order
	   as their corresponding hooks */
	for (j = i + 1; j < NF_BR_NUMHOOKS; j++) {
		if (!newinfo->hook_entry[j])
			continue;
		if (newinfo->hook_entry[j] <= newinfo->hook_entry[i]) {
			BUGPRINT("Hook order must be followed\n");
			return -EINVAL;
		}
		i = j;
	}

	/* do some early checkings and initialize some things */
	i = 0; /* holds the expected nr. of entries for the chain */
	j = 0; /* holds the up to now counted entries for the chain */
	k = 0; /* holds the total nr. of entries, should equal
		  newinfo->nentries afterwards */
	udc_cnt = 0; /* will hold the nr. of user defined chains (udc) */
	ret = EBT_ENTRY_ITERATE(newinfo->entries, newinfo->entries_size,
	   ebt_check_entry_size_and_hooks, newinfo,
	   &i, &j, &k, &udc_cnt);

	if (ret != 0)
		return ret;

	if (i != j) {
		BUGPRINT("nentries does not equal the nr of entries in the "
			 "(last) chain\n");
		return -EINVAL;
	}
	if (k != newinfo->nentries) {
		BUGPRINT("Total nentries is wrong\n");
		return -EINVAL;
	}

	/* get the location of the udc, put them in an array
	   while we're at it, allocate the chainstack */
	if (udc_cnt) {
		/* this will get free'd in do_replace()/ebt_register_table()
		   if an error occurs */
		newinfo->chainstack =
			vmalloc(nr_cpu_ids * sizeof(*(newinfo->chainstack)));
		if (!newinfo->chainstack)
			return -ENOMEM;
		for_each_possible_cpu(i) {
			newinfo->chainstack[i] =
			  vmalloc(udc_cnt * sizeof(*(newinfo->chainstack[0])));
			if (!newinfo->chainstack[i]) {
				while (i)
					vfree(newinfo->chainstack[--i]);
				vfree(newinfo->chainstack);
				newinfo->chainstack = NULL;
				return -ENOMEM;
			}
		}

		cl_s = vmalloc(udc_cnt * sizeof(*cl_s));
		if (!cl_s)
			return -ENOMEM;
		i = 0; /* the i'th udc */
		EBT_ENTRY_ITERATE(newinfo->entries, newinfo->entries_size,
		   ebt_get_udc_positions, newinfo, &i, cl_s);
		/* sanity check */
		if (i != udc_cnt) {
			BUGPRINT("i != udc_cnt\n");
			vfree(cl_s);
			return -EFAULT;
		}
	}

	/* Check for loops */
	for (i = 0; i < NF_BR_NUMHOOKS; i++)
		if (newinfo->hook_entry[i])
			if (check_chainloops(newinfo->hook_entry[i],
			   cl_s, udc_cnt, i, newinfo->entries)) {
				vfree(cl_s);
				return -EINVAL;
			}

	/* we now know the following (along with E=mc²):
	   - the nr of entries in each chain is right
	   - the size of the allocated space is right
	   - all valid hooks have a corresponding chain
	   - there are no loops
	   - wrong data can still be on the level of a single entry
	   - could be there are jumps to places that are not the
	     beginning of a chain. This can only occur in chains that
	     are not accessible from any base chains, so we don't care. */

	/* used to know what we need to clean up if something goes wrong */
	i = 0;
	ret = EBT_ENTRY_ITERATE(newinfo->entries, newinfo->entries_size,
	   ebt_check_entry, newinfo, name, &i, cl_s, udc_cnt);
	if (ret != 0) {
		EBT_ENTRY_ITERATE(newinfo->entries, newinfo->entries_size,
		   ebt_cleanup_entry, &i);
	}
	vfree(cl_s);
	return ret;
}

/* called under write_lock */
static void get_counters(struct ebt_counter *oldcounters,
   struct ebt_counter *counters, unsigned int nentries)
{
	int i, cpu;
	struct ebt_counter *counter_base;

	/* counters of cpu 0 */
	memcpy(counters, oldcounters,
	       sizeof(struct ebt_counter) * nentries);

	/* add other counters to those of cpu 0 */
	for_each_possible_cpu(cpu) {
		if (cpu == 0)
			continue;
		counter_base = COUNTER_BASE(oldcounters, nentries, cpu);
		for (i = 0; i < nentries; i++) {
			counters[i].pcnt += counter_base[i].pcnt;
			counters[i].bcnt += counter_base[i].bcnt;
		}
	}
}

/* replace the table */
static int do_replace(void __user *user, unsigned int len)
{
	int ret, i, countersize;
	struct ebt_table_info *newinfo;
	struct ebt_replace tmp;
	struct ebt_table *t;
	struct ebt_counter *counterstmp = NULL;
	/* used to be able to unlock earlier */
	struct ebt_table_info *table;

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

	if (len != sizeof(tmp) + tmp.entries_size) {
		BUGPRINT("Wrong len argument\n");
		return -EINVAL;
	}

	if (tmp.entries_size == 0) {
		BUGPRINT("Entries_size never zero\n");
		return -EINVAL;
	}
	/* overflow check */
	if (tmp.nentries >= ((INT_MAX - sizeof(struct ebt_table_info)) / NR_CPUS -
			SMP_CACHE_BYTES) / sizeof(struct ebt_counter))
		return -ENOMEM;
	if (tmp.num_counters >= INT_MAX / sizeof(struct ebt_counter))
		return -ENOMEM;

	countersize = COUNTER_OFFSET(tmp.nentries) * nr_cpu_ids;
	newinfo = vmalloc(sizeof(*newinfo) + countersize);
	if (!newinfo)
		return -ENOMEM;

	if (countersize)
		memset(newinfo->counters, 0, countersize);

	newinfo->entries = vmalloc(tmp.entries_size);
	if (!newinfo->entries) {
		ret = -ENOMEM;
		goto free_newinfo;
	}
	if (copy_from_user(
	   newinfo->entries, tmp.entries, tmp.entries_size) != 0) {
		BUGPRINT("Couldn't copy entries from userspace\n");
		ret = -EFAULT;
		goto free_entries;
	}

	/* the user wants counters back
	   the check on the size is done later, when we have the lock */
	if (tmp.num_counters) {
		counterstmp = vmalloc(tmp.num_counters * sizeof(*counterstmp));
		if (!counterstmp) {
			ret = -ENOMEM;
			goto free_entries;
		}
	}
	else
		counterstmp = NULL;

	/* this can get initialized by translate_table() */
	newinfo->chainstack = NULL;
	ret = ebt_verify_pointers(&tmp, newinfo);
	if (ret != 0)
		goto free_counterstmp;

	ret = translate_table(tmp.name, newinfo);

	if (ret != 0)
		goto free_counterstmp;

	t = find_table_lock(tmp.name, &ret, &ebt_mutex);
	if (!t) {
		ret = -ENOENT;
		goto free_iterate;
	}

	/* the table doesn't like it */
	if (t->check && (ret = t->check(newinfo, tmp.valid_hooks)))
		goto free_unlock;

	if (tmp.num_counters && tmp.num_counters != t->private->nentries) {
		BUGPRINT("Wrong nr. of counters requested\n");
		ret = -EINVAL;
		goto free_unlock;
	}

	/* we have the mutex lock, so no danger in reading this pointer */
	table = t->private;
	/* make sure the table can only be rmmod'ed if it contains no rules */
	if (!table->nentries && newinfo->nentries && !try_module_get(t->me)) {
		ret = -ENOENT;
		goto free_unlock;
	} else if (table->nentries && !newinfo->nentries)
		module_put(t->me);
	/* we need an atomic snapshot of the counters */
	write_lock_bh(&t->lock);
	if (tmp.num_counters)
		get_counters(t->private->counters, counterstmp,
		   t->private->nentries);

	t->private = newinfo;
	write_unlock_bh(&t->lock);
	mutex_unlock(&ebt_mutex);
	/* so, a user can change the chains while having messed up her counter
	   allocation. Only reason why this is done is because this way the lock
	   is held only once, while this doesn't bring the kernel into a
	   dangerous state. */
	if (tmp.num_counters &&
	   copy_to_user(tmp.counters, counterstmp,
	   tmp.num_counters * sizeof(struct ebt_counter))) {
		BUGPRINT("Couldn't copy counters to userspace\n");
		ret = -EFAULT;
	}
	else
		ret = 0;

	/* decrease module count and free resources */
	EBT_ENTRY_ITERATE(table->entries, table->entries_size,
	   ebt_cleanup_entry, NULL);

	vfree(table->entries);
	if (table->chainstack) {
		for_each_possible_cpu(i)
			vfree(table->chainstack[i]);
		vfree(table->chainstack);
	}
	vfree(table);

	vfree(counterstmp);
	return ret;

free_unlock:
	mutex_unlock(&ebt_mutex);
free_iterate:
	EBT_ENTRY_ITERATE(newinfo->entries, newinfo->entries_size,
	   ebt_cleanup_entry, NULL);
free_counterstmp:
	vfree(counterstmp);
	/* can be initialized in translate_table() */
	if (newinfo->chainstack) {
		for_each_possible_cpu(i)
			vfree(newinfo->chainstack[i]);
		vfree(newinfo->chainstack);
	}
free_entries:
	vfree(newinfo->entries);
free_newinfo:
	vfree(newinfo);
	return ret;
}

int ebt_register_table(struct ebt_table *table)
{
	struct ebt_table_info *newinfo;
	struct ebt_table *t;
	struct ebt_replace_kernel *repl;
	int ret, i, countersize;
	void *p;

	if (!table || !(repl = table->table) || !repl->entries ||
	    repl->entries_size == 0 ||
	    repl->counters || table->private) {
		BUGPRINT("Bad table data for ebt_register_table!!!\n");
		return -EINVAL;
	}

	countersize = COUNTER_OFFSET(repl->nentries) * nr_cpu_ids;
	newinfo = vmalloc(sizeof(*newinfo) + countersize);
	ret = -ENOMEM;
	if (!newinfo)
		return -ENOMEM;

	p = vmalloc(repl->entries_size);
	if (!p)
		goto free_newinfo;

	memcpy(p, repl->entries, repl->entries_size);
	newinfo->entries = p;

	newinfo->entries_size = repl->entries_size;
	newinfo->nentries = repl->nentries;

	if (countersize)
		memset(newinfo->counters, 0, countersize);

	/* fill in newinfo and parse the entries */
	newinfo->chainstack = NULL;
	for (i = 0; i < NF_BR_NUMHOOKS; i++) {
		if ((repl->valid_hooks & (1 << i)) == 0)
			newinfo->hook_entry[i] = NULL;
		else
			newinfo->hook_entry[i] = p +
				((char *)repl->hook_entry[i] - repl->entries);
	}
	ret = translate_table(repl->name, newinfo);
	if (ret != 0) {
		BUGPRINT("Translate_table failed\n");
		goto free_chainstack;
	}

	if (table->check && table->check(newinfo, table->valid_hooks)) {
		BUGPRINT("The table doesn't like its own initial data, lol\n");
		return -EINVAL;
	}

	table->private = newinfo;
	rwlock_init(&table->lock);
	ret = mutex_lock_interruptible(&ebt_mutex);
	if (ret != 0)
		goto free_chainstack;

	list_for_each_entry(t, &ebt_tables, list) {
		if (strcmp(t->name, table->name) == 0) {
			ret = -EEXIST;
			BUGPRINT("Table name already exists\n");
			goto free_unlock;
		}
	}

	/* Hold a reference count if the chains aren't empty */
	if (newinfo->nentries && !try_module_get(table->me)) {
		ret = -ENOENT;
		goto free_unlock;
	}
	list_add(&table->list, &ebt_tables);
	mutex_unlock(&ebt_mutex);
	return 0;
free_unlock:
	mutex_unlock(&ebt_mutex);
free_chainstack:
	if (newinfo->chainstack) {
		for_each_possible_cpu(i)
			vfree(newinfo->chainstack[i]);
		vfree(newinfo->chainstack);
	}
	vfree(newinfo->entries);
free_newinfo:
	vfree(newinfo);
	return ret;
}

void ebt_unregister_table(struct ebt_table *table)
{
	int i;

	if (!table) {
		BUGPRINT("Request to unregister NULL table!!!\n");
		return;
	}
	mutex_lock(&ebt_mutex);
	list_del(&table->list);
	mutex_unlock(&ebt_mutex);
	vfree(table->private->entries);
	if (table->private->chainstack) {
		for_each_possible_cpu(i)
			vfree(table->private->chainstack[i]);
		vfree(table->private->chainstack);
	}
	vfree(table->private);
}

/* userspace just supplied us with counters */
static int update_counters(void __user *user, unsigned int len)
{
	int i, ret;
	struct ebt_counter *tmp;
	struct ebt_replace hlp;
	struct ebt_table *t;

	if (copy_from_user(&hlp, user, sizeof(hlp)))
		return -EFAULT;

	if (len != sizeof(hlp) + hlp.num_counters * sizeof(struct ebt_counter))
		return -EINVAL;
	if (hlp.num_counters == 0)
		return -EINVAL;

	if (!(tmp = vmalloc(hlp.num_counters * sizeof(*tmp)))) {
		MEMPRINT("Update_counters && nomemory\n");
		return -ENOMEM;
	}

	t = find_table_lock(hlp.name, &ret, &ebt_mutex);
	if (!t)
		goto free_tmp;

	if (hlp.num_counters != t->private->nentries) {
		BUGPRINT("Wrong nr of counters\n");
		ret = -EINVAL;
		goto unlock_mutex;
	}

	if ( copy_from_user(tmp, hlp.counters,
	   hlp.num_counters * sizeof(struct ebt_counter)) ) {
		BUGPRINT("Updata_counters && !cfu\n");
		ret = -EFAULT;
		goto unlock_mutex;
	}

	/* we want an atomic add of the counters */
	write_lock_bh(&t->lock);

	/* we add to the counters of the first cpu */
	for (i = 0; i < hlp.num_counters; i++) {
		t->private->counters[i].pcnt += tmp[i].pcnt;
		t->private->counters[i].bcnt += tmp[i].bcnt;
	}

	write_unlock_bh(&t->lock);
	ret = 0;
unlock_mutex:
	mutex_unlock(&ebt_mutex);
free_tmp:
	vfree(tmp);
	return ret;
}

static inline int ebt_make_matchname(struct ebt_entry_match *m,
   char *base, char __user *ubase)
{
	char __user *hlp = ubase + ((char *)m - base);
	if (copy_to_user(hlp, m->u.match->name, EBT_FUNCTION_MAXNAMELEN))
		return -EFAULT;
	return 0;
}

static inline int ebt_make_watchername(struct ebt_entry_watcher *w,
   char *base, char __user *ubase)
{
	char __user *hlp = ubase + ((char *)w - base);
	if (copy_to_user(hlp , w->u.watcher->name, EBT_FUNCTION_MAXNAMELEN))
		return -EFAULT;
	return 0;
}

static inline int ebt_make_names(struct ebt_entry *e, char *base, char __user *ubase)
{
	int ret;
	char __user *hlp;
	struct ebt_entry_target *t;

	if (e->bitmask == 0)
		return 0;

	hlp = ubase + (((char *)e + e->target_offset) - base);
	t = (struct ebt_entry_target *)(((char *)e) + e->target_offset);

	ret = EBT_MATCH_ITERATE(e, ebt_make_matchname, base, ubase);
	if (ret != 0)
		return ret;
	ret = EBT_WATCHER_ITERATE(e, ebt_make_watchername, base, ubase);
	if (ret != 0)
		return ret;
	if (copy_to_user(hlp, t->u.target->name, EBT_FUNCTION_MAXNAMELEN))
		return -EFAULT;
	return 0;
}

/* called with ebt_mutex locked */
static int copy_everything_to_user(struct ebt_table *t, void __user *user,
   int *len, int cmd)
{
	struct ebt_replace tmp;
	struct ebt_counter *counterstmp, *oldcounters;
	unsigned int entries_size, nentries;
	char *entries;

	if (cmd == EBT_SO_GET_ENTRIES) {
		entries_size = t->private->entries_size;
		nentries = t->private->nentries;
		entries = t->private->entries;
		oldcounters = t->private->counters;
	} else {
		entries_size = t->table->entries_size;
		nentries = t->table->nentries;
		entries = t->table->entries;
		oldcounters = t->table->counters;
	}

	if (copy_from_user(&tmp, user, sizeof(tmp))) {
		BUGPRINT("Cfu didn't work\n");
		return -EFAULT;
	}

	if (*len != sizeof(struct ebt_replace) + entries_size +
	   (tmp.num_counters? nentries * sizeof(struct ebt_counter): 0)) {
		BUGPRINT("Wrong size\n");
		return -EINVAL;
	}

	if (tmp.nentries != nentries) {
		BUGPRINT("Nentries wrong\n");
		return -EINVAL;
	}

	if (tmp.entries_size != entries_size) {
		BUGPRINT("Wrong size\n");
		return -EINVAL;
	}

	/* userspace might not need the counters */
	if (tmp.num_counters) {
		if (tmp.num_counters != nentries) {
			BUGPRINT("Num_counters wrong\n");
			return -EINVAL;
		}
		counterstmp = vmalloc(nentries * sizeof(*counterstmp));
		if (!counterstmp) {
			MEMPRINT("Couldn't copy counters, out of memory\n");
			return -ENOMEM;
		}
		write_lock_bh(&t->lock);
		get_counters(oldcounters, counterstmp, nentries);
		write_unlock_bh(&t->lock);

		if (copy_to_user(tmp.counters, counterstmp,
		   nentries * sizeof(struct ebt_counter))) {
			BUGPRINT("Couldn't copy counters to userspace\n");
			vfree(counterstmp);
			return -EFAULT;
		}
		vfree(counterstmp);
	}

	if (copy_to_user(tmp.entries, entries, entries_size)) {
		BUGPRINT("Couldn't copy entries to userspace\n");
		return -EFAULT;
	}
	/* set the match/watcher/target names right */
	return EBT_ENTRY_ITERATE(entries, entries_size,
	   ebt_make_names, entries, tmp.entries);
}

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

	switch(cmd) {
	case EBT_SO_SET_ENTRIES:
		ret = do_replace(user, len);
		break;
	case EBT_SO_SET_COUNTERS:
		ret = update_counters(user, len);
		break;
	default:
		ret = -EINVAL;
  }
	return ret;
}

static int do_ebt_get_ctl(struct sock *sk, int cmd, void __user *user, int *len)
{
	int ret;
	struct ebt_replace tmp;
	struct ebt_table *t;

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

	t = find_table_lock(tmp.name, &ret, &ebt_mutex);
	if (!t)
		return ret;

	switch(cmd) {
	case EBT_SO_GET_INFO:
	case EBT_SO_GET_INIT_INFO:
		if (*len != sizeof(struct ebt_replace)){
			ret = -EINVAL;
			mutex_unlock(&ebt_mutex);
			break;
		}
		if (cmd == EBT_SO_GET_INFO) {
			tmp.nentries = t->private->nentries;
			tmp.entries_size = t->private->entries_size;
			tmp.valid_hooks = t->valid_hooks;
		} else {
			tmp.nentries = t->table->nentries;
			tmp.entries_size = t->table->entries_size;
			tmp.valid_hooks = t->table->valid_hooks;
		}
		mutex_unlock(&ebt_mutex);
		if (copy_to_user(user, &tmp, *len) != 0){
			BUGPRINT("c2u Didn't work\n");
			ret = -EFAULT;
			break;
		}
		ret = 0;
		break;

	case EBT_SO_GET_ENTRIES:
	case EBT_SO_GET_INIT_ENTRIES:
		ret = copy_everything_to_user(t, user, len, cmd);
		mutex_unlock(&ebt_mutex);
		break;

	default:
		mutex_unlock(&ebt_mutex);
		ret = -EINVAL;
	}

	return ret;
}

static struct nf_sockopt_ops ebt_sockopts =
{
	.pf		= PF_INET,
	.set_optmin	= EBT_BASE_CTL,
	.set_optmax	= EBT_SO_SET_MAX + 1,
	.set		= do_ebt_set_ctl,
	.get_optmin	= EBT_BASE_CTL,
	.get_optmax	= EBT_SO_GET_MAX + 1,
	.get		= do_ebt_get_ctl,
	.owner		= THIS_MODULE,
};

static int __init ebtables_init(void)
{
	int ret;

	ret = xt_register_target(&ebt_standard_target);
	if (ret < 0)
		return ret;
	ret = nf_register_sockopt(&ebt_sockopts);
	if (ret < 0) {
		xt_unregister_target(&ebt_standard_target);
		return ret;
	}

	printk(KERN_INFO "Ebtables v2.0 registered\n");
	return 0;
}

static void __exit ebtables_fini(void)
{
	nf_unregister_sockopt(&ebt_sockopts);
	xt_unregister_target(&ebt_standard_target);
	printk(KERN_INFO "Ebtables v2.0 unregistered\n");
}

EXPORT_SYMBOL(ebt_register_table);
EXPORT_SYMBOL(ebt_unregister_table);
EXPORT_SYMBOL(ebt_do_table);
module_init(ebtables_init);
module_exit(ebtables_fini);
MODULE_LICENSE("GPL");