ip_tables.c

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

	i = 0;
	IPT_ENTRY_ITERATE(t->private->entries,
			  t->private->size,
			  add_counter_to_entry,
			  paddc->counters,
			  &i);
 unlock_up_free:
	write_unlock_bh(&t->lock);
	up(&ipt_mutex);
 free:
	vfree(paddc);

	return ret;
}

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

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

	switch (cmd) {
	case IPT_SO_SET_REPLACE:
		ret = do_replace(user, len);
		break;

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

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

	return ret;
}

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

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

	switch (cmd) {
	case IPT_SO_GET_INFO: {
		char name[IPT_TABLE_MAXNAMELEN];
		struct ipt_table *t;

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

		if (copy_from_user(name, user, sizeof(name)) != 0) {
			ret = -EFAULT;
			break;
		}
		t = find_table_lock(name, &ret, &ipt_mutex);
		if (t) {
			struct ipt_getinfo info;

			info.valid_hooks = t->valid_hooks;
			memcpy(info.hook_entry, t->private->hook_entry,
			       sizeof(info.hook_entry));
			memcpy(info.underflow, t->private->underflow,
			       sizeof(info.underflow));
			info.num_entries = t->private->number;
			info.size = t->private->size;
			strcpy(info.name, name);

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

			up(&ipt_mutex);
		}
	}
	break;

	case IPT_SO_GET_ENTRIES: {
		struct ipt_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 ipt_get_entries) + get.size) {
			duprintf("get_entries: %u != %u\n", *len,
				 sizeof(struct ipt_get_entries) + get.size);
			ret = -EINVAL;
		} else
			ret = get_entries(&get, user);
		break;
	}

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

	return ret;
}

/* Registration hooks for targets. */
int
ipt_register_target(struct ipt_target *target)
{
	int ret;

	MOD_INC_USE_COUNT;
	ret = down_interruptible(&ipt_mutex);
	if (ret != 0) {
		MOD_DEC_USE_COUNT;
		return ret;
	}
	if (!list_named_insert(&ipt_target, target)) {
		duprintf("ipt_register_target: `%s' already in list!\n",
			 target->name);
		ret = -EINVAL;
		MOD_DEC_USE_COUNT;
	}
	up(&ipt_mutex);
	return ret;
}

void
ipt_unregister_target(struct ipt_target *target)
{
	down(&ipt_mutex);
	LIST_DELETE(&ipt_target, target);
	up(&ipt_mutex);
	MOD_DEC_USE_COUNT;
}

int
ipt_register_match(struct ipt_match *match)
{
	int ret;

	MOD_INC_USE_COUNT;
	ret = down_interruptible(&ipt_mutex);
	if (ret != 0) {
		MOD_DEC_USE_COUNT;
		return ret;
	}
	if (!list_named_insert(&ipt_match, match)) {
		duprintf("ipt_register_match: `%s' already in list!\n",
			 match->name);
		MOD_DEC_USE_COUNT;
		ret = -EINVAL;
	}
	up(&ipt_mutex);

	return ret;
}

void
ipt_unregister_match(struct ipt_match *match)
{
	down(&ipt_mutex);
	LIST_DELETE(&ipt_match, match);
	up(&ipt_mutex);
	MOD_DEC_USE_COUNT;
}

int ipt_register_table(struct ipt_table *table)
{
	int ret;
	struct ipt_table_info *newinfo;
	static struct ipt_table_info bootstrap
		= { 0, 0, { 0 }, { 0 }, { } };

	MOD_INC_USE_COUNT;
	newinfo = vmalloc(sizeof(struct ipt_table_info)
			  + SMP_ALIGN(table->table->size) * smp_num_cpus);
	if (!newinfo) {
		ret = -ENOMEM;
		MOD_DEC_USE_COUNT;
		return ret;
	}
	memcpy(newinfo->entries, table->table->entries, table->table->size);

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

	ret = down_interruptible(&ipt_mutex);
	if (ret != 0) {
		vfree(newinfo);
		MOD_DEC_USE_COUNT;
		return ret;
	}

	/* Don't autoload: we'd eat our tail... */
	if (list_named_find(&ipt_tables, table->name)) {
		ret = -EEXIST;
		goto free_unlock;
	}

	/* Simplifies replace_table code. */
	table->private = &bootstrap;
	if (!replace_table(table, 0, newinfo, &ret))
		goto free_unlock;

	duprintf("table->private->number = %u\n",
		 table->private->number);

	table->lock = RW_LOCK_UNLOCKED;
	list_prepend(&ipt_tables, table);

 unlock:
	up(&ipt_mutex);
	return ret;

 free_unlock:
	vfree(newinfo);
	MOD_DEC_USE_COUNT;
	goto unlock;
}

void ipt_unregister_table(struct ipt_table *table)
{
	down(&ipt_mutex);
	LIST_DELETE(&ipt_tables, table);
	up(&ipt_mutex);

	/* Decrease module usage counts and free resources */
	IPT_ENTRY_ITERATE(table->private->entries, table->private->size,
			  cleanup_entry, NULL);
	vfree(table->private);
	MOD_DEC_USE_COUNT;
}

/* Returns 1 if the port is matched by the range, 0 otherwise */
static inline int
port_match(u_int16_t min, u_int16_t max, u_int16_t port, int invert)
{
	int ret;

	ret = (port >= min && port <= max) ^ invert;
	return ret;
}

static int
tcp_find_option(u_int8_t option,
		const struct tcphdr *tcp,
		u_int16_t datalen,
		int invert,
		int *hotdrop)
{
	unsigned int i = sizeof(struct tcphdr);
	const u_int8_t *opt = (u_int8_t *)tcp;

	duprintf("tcp_match: finding option\n");
	/* If we don't have the whole header, drop packet. */
	if (tcp->doff * 4 > datalen) {
		*hotdrop = 1;
		return 0;
	}

	while (i < tcp->doff * 4) {
		if (opt[i] == option) return !invert;
		if (opt[i] < 2) i++;
		else i += opt[i+1]?:1;
	}

	return invert;
}

static int
tcp_match(const struct sk_buff *skb,
	  const struct net_device *in,
	  const struct net_device *out,
	  const void *matchinfo,
	  int offset,
	  const void *hdr,
	  u_int16_t datalen,
	  int *hotdrop)
{
	const struct tcphdr *tcp = hdr;
	const struct ipt_tcp *tcpinfo = matchinfo;

	/* To quote Alan:

	   Don't allow a fragment of TCP 8 bytes in. Nobody normal
	   causes this. Its a cracker trying to break in by doing a
	   flag overwrite to pass the direction checks.
	*/

	if (offset == 1) {
		duprintf("Dropping evil TCP offset=1 frag.\n");
		*hotdrop = 1;
		return 0;
	} else if (offset == 0 && datalen < sizeof(struct tcphdr)) {
		/* We've been asked to examine this packet, and we
		   can't.  Hence, no choice but to drop. */
		duprintf("Dropping evil TCP offset=0 tinygram.\n");
		*hotdrop = 1;
		return 0;
	}

	/* FIXME: Try tcp doff >> packet len against various stacks --RR */

#define FWINVTCP(bool,invflg) ((bool) ^ !!(tcpinfo->invflags & invflg))

	/* Must not be a fragment. */
	return !offset
		&& port_match(tcpinfo->spts[0], tcpinfo->spts[1],
			      ntohs(tcp->source),
			      !!(tcpinfo->invflags & IPT_TCP_INV_SRCPT))
		&& port_match(tcpinfo->dpts[0], tcpinfo->dpts[1],
			      ntohs(tcp->dest),
			      !!(tcpinfo->invflags & IPT_TCP_INV_DSTPT))
		&& FWINVTCP((((unsigned char *)tcp)[13]
			     & tcpinfo->flg_mask)
			    == tcpinfo->flg_cmp,
			    IPT_TCP_INV_FLAGS)
		&& (!tcpinfo->option
		    || tcp_find_option(tcpinfo->option, tcp, datalen,
				       tcpinfo->invflags
				       & IPT_TCP_INV_OPTION,
				       hotdrop));
}

/* Called when user tries to insert an entry of this type. */
static int
tcp_checkentry(const char *tablename,
	       const struct ipt_ip *ip,
	       void *matchinfo,
	       unsigned int matchsize,
	       unsigned int hook_mask)
{
	const struct ipt_tcp *tcpinfo = matchinfo;

	/* Must specify proto == TCP, and no unknown invflags */
	return ip->proto == IPPROTO_TCP
		&& !(ip->invflags & IPT_INV_PROTO)
		&& matchsize == IPT_ALIGN(sizeof(struct ipt_tcp))
		&& !(tcpinfo->invflags & ~IPT_TCP_INV_MASK);
}

static int
udp_match(const struct sk_buff *skb,
	  const struct net_device *in,
	  const struct net_device *out,
	  const void *matchinfo,
	  int offset,
	  const void *hdr,
	  u_int16_t datalen,
	  int *hotdrop)
{
	const struct udphdr *udp = hdr;
	const struct ipt_udp *udpinfo = matchinfo;

	if (offset == 0 && datalen < sizeof(struct udphdr)) {
		/* We've been asked to examine this packet, and we
		   can't.  Hence, no choice but to drop. */
		duprintf("Dropping evil UDP tinygram.\n");
		*hotdrop = 1;
		return 0;
	}

	/* Must not be a fragment. */
	return !offset
		&& port_match(udpinfo->spts[0], udpinfo->spts[1],
			      ntohs(udp->source),
			      !!(udpinfo->invflags & IPT_UDP_INV_SRCPT))
		&& port_match(udpinfo->dpts[0], udpinfo->dpts[1],
			      ntohs(udp->dest),
			      !!(udpinfo->invflags & IPT_UDP_INV_DSTPT));
}

/* Called when user tries to insert an entry of this type. */
static int
udp_checkentry(const char *tablename,
	       const struct ipt_ip *ip,
	       void *matchinfo,
	       unsigned int matchinfosize,
	       unsigned int hook_mask)
{
	const struct ipt_udp *udpinfo = matchinfo;

	/* Must specify proto == UDP, and no unknown invflags */
	if (ip->proto != IPPROTO_UDP || (ip->invflags & IPT_INV_PROTO)) {
		duprintf("ipt_udp: Protocol %u != %u\n", ip->proto,
			 IPPROTO_UDP);
		return 0;
	}
	if (matchinfosize != IPT_ALIGN(sizeof(struct ipt_udp))) {
		duprintf("ipt_udp: matchsize %u != %u\n",
			 matchinfosize, IPT_ALIGN(sizeof(struct ipt_udp)));
		return 0;
	}
	if (udpinfo->invflags & ~IPT_UDP_INV_MASK) {
		duprintf("ipt_udp: unknown flags %X\n",
			 udpinfo->invflags);
		return 0;
	}

	return 1;
}

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

static int
icmp_match(const struct sk_buff *skb,
	   const struct net_device *in,
	   const struct net_device *out,
	   const void *matchinfo,
	   int offset,
	   const void *hdr,
	   u_int16_t datalen,
	   int *hotdrop)
{
	const struct icmphdr *icmp = hdr;
	const struct ipt_icmp *icmpinfo = matchinfo;

	if (offset == 0 && datalen < 2) {
		/* 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 = 1;
		return 0;
	}

	/* Must not be a fragment. */
	return !offset
		&& icmp_type_code_match(icmpinfo->type,
					icmpinfo->code[0],
					icmpinfo->code[1],
					icmp->type, icmp->code,
					!!(icmpinfo->invflags&IPT_ICMP_INV));
}

/* Called when user tries to insert an entry of this type. */
static int
icmp_checkentry(const char *tablename,
	   const struct ipt_ip *ip,
	   void *matchinfo,
	   unsigned int matchsize,
	   unsigned int hook_mask)
{
	const struct ipt_icmp *icmpinfo = matchinfo;

	/* Must specify proto == ICMP, and no unknown invflags */
	return ip->proto == IPPROTO_ICMP
		&& !(ip->invflags & IPT_INV_PROTO)
		&& matchsize == IPT_ALIGN(sizeof(struct ipt_icmp))
		&& !(icmpinfo->invflags & ~IPT_ICMP_INV);
}

/* The built-in targets: standard (NULL) and error. */
static struct ipt_target ipt_standard_target
= { { NULL, NULL }, IPT_STANDARD_TARGET, NULL, NULL, NULL };
static struct ipt_target ipt_error_target
= { { NULL, NULL }, IPT_ERROR_TARGET, ipt_error, NULL, NULL };

static struct nf_sockopt_ops ipt_sockopts
= { { NULL, NULL }, PF_INET, IPT_BASE_CTL, IPT_SO_SET_MAX+1, do_ipt_set_ctl,
    IPT_BASE_CTL, IPT_SO_GET_MAX+1, do_ipt_get_ctl, 0, NULL  };

static struct ipt_match tcp_matchstruct
= { { NULL, NULL }, "tcp", &tcp_match, &tcp_checkentry, NULL };
static struct ipt_match udp_matchstruct
= { { NULL, NULL }, "udp", &udp_match, &udp_checkentry, NULL };
static struct ipt_match icmp_matchstruct
= { { NULL, NULL }, "icmp", &icmp_match, &icmp_checkentry, NULL };

#ifdef CONFIG_PROC_FS
static inline int print_name(const struct ipt_table *t,
			     off_t start_offset, char *buffer, int length,
			     off_t *pos, unsigned int *count)
{
	if ((*count)++ >= start_offset) {
		unsigned int namelen;

		namelen = sprintf(buffer + *pos, "%s\n", t->name);
		if (*pos + namelen > length) {
			/* Stop iterating */
			return 1;
		}
		*pos += namelen;
	}
	return 0;
}

static int ipt_get_tables(char *buffer, char **start, off_t offset, int length)
{
	off_t pos = 0;
	unsigned int count = 0;

	if (down_interruptible(&ipt_mutex) != 0)
		return 0;

	LIST_FIND(&ipt_tables, print_name, struct ipt_table *,
		  offset, buffer, length, &pos, &count);

	up(&ipt_mutex);

	/* `start' hack - see fs/proc/generic.c line ~105 */
	*start=(char *)((unsigned long)count-offset);
	return pos;
}
#endif /*CONFIG_PROC_FS*/

static int __init init(void)
{
	int ret;

	/* Noone else will be downing sem now, so we won't sleep */
	down(&ipt_mutex);
	list_append(&ipt_target, &ipt_standard_target);
	list_append(&ipt_target, &ipt_error_target);
	list_append(&ipt_match, &tcp_matchstruct);
	list_append(&ipt_match, &udp_matchstruct);
	list_append(&ipt_match, &icmp_matchstruct);
	up(&ipt_mutex);

	/* Register setsockopt */
	ret = nf_register_sockopt(&ipt_sockopts);
	if (ret < 0) {
		duprintf("Unable to register sockopts.\n");
		return ret;
	}

#ifdef CONFIG_PROC_FS
	if (!proc_net_create("ip_tables_names", 0, ipt_get_tables)) {
		nf_unregister_sockopt(&ipt_sockopts);
		return -ENOMEM;
	}
#endif

	printk("ip_tables: (c)2000 Netfilter core team\n");
	return 0;
}

static void __exit fini(void)
{
	nf_unregister_sockopt(&ipt_sockopts);
#ifdef CONFIG_PROC_FS
	proc_net_remove("ip_tables_names");
#endif
}

EXPORT_SYMBOL(ipt_register_table);
EXPORT_SYMBOL(ipt_unregister_table);
EXPORT_SYMBOL(ipt_register_match);
EXPORT_SYMBOL(ipt_unregister_match);
EXPORT_SYMBOL(ipt_do_table);
EXPORT_SYMBOL(ipt_register_target);
EXPORT_SYMBOL(ipt_unregister_target);

module_init(init);
module_exit(fini);