#include <linux/export.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/jiffies.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/ratelimit.h>
#include <net/netlink.h>

static const u16 nla_attr_minlen[NLA_TYPE_MAX+1] = {
	[NLA_U8]	= sizeof(u8),
	[NLA_U16]	= sizeof(u16),
	[NLA_U32]	= sizeof(u32),
	[NLA_U64]	= sizeof(u64),
	[NLA_MSECS]	= sizeof(u64),
	[NLA_NESTED]	= NLA_HDRLEN,
};

static int validate_nla(const struct nlattr *nla, int maxtype,
			const struct nla_policy *policy)
{
	const struct nla_policy *pt;
	int minlen = 0, attrlen = nla_len(nla), type = nla_type(nla);

	if (type <= 0 || type > maxtype)
		return 0;

	pt = &policy[type];

	BUG_ON(pt->type > NLA_TYPE_MAX);

	switch (pt->type) {
	case NLA_FLAG:
		if (attrlen > 0)
			return -ERANGE;
		break;

	case NLA_NUL_STRING:
		if (pt->len)
			minlen = min_t(int, attrlen, pt->len + 1);
		else
			minlen = attrlen;

		if (!minlen || memchr(nla_data(nla), '\0', minlen) == NULL)
			return -EINVAL;
		

	case NLA_STRING:
		if (attrlen < 1)
			return -ERANGE;

		if (pt->len) {
			char *buf = nla_data(nla);

			if (buf[attrlen - 1] == '\0')
				attrlen--;

			if (attrlen > pt->len)
				return -ERANGE;
		}
		break;

	case NLA_BINARY:
		if (pt->len && attrlen > pt->len)
			return -ERANGE;
		break;

	case NLA_NESTED_COMPAT:
		if (attrlen < pt->len)
			return -ERANGE;
		if (attrlen < NLA_ALIGN(pt->len))
			break;
		if (attrlen < NLA_ALIGN(pt->len) + NLA_HDRLEN)
			return -ERANGE;
		nla = nla_data(nla) + NLA_ALIGN(pt->len);
		if (attrlen < NLA_ALIGN(pt->len) + NLA_HDRLEN + nla_len(nla))
			return -ERANGE;
		break;
	case NLA_NESTED:
		if (attrlen == 0)
			break;
	default:
		if (pt->len)
			minlen = pt->len;
		else if (pt->type != NLA_UNSPEC)
			minlen = nla_attr_minlen[pt->type];

		if (attrlen < minlen)
			return -ERANGE;
	}

	return 0;
}

int nla_validate(const struct nlattr *head, int len, int maxtype,
		 const struct nla_policy *policy)
{
	const struct nlattr *nla;
	int rem, err;

	nla_for_each_attr(nla, head, len, rem) {
		err = validate_nla(nla, maxtype, policy);
		if (err < 0)
			goto errout;
	}

	err = 0;
errout:
	return err;
}

int
nla_policy_len(const struct nla_policy *p, int n)
{
	int i, len = 0;

	for (i = 0; i < n; i++, p++) {
		if (p->len)
			len += nla_total_size(p->len);
		else if (nla_attr_minlen[p->type])
			len += nla_total_size(nla_attr_minlen[p->type]);
	}

	return len;
}

int nla_parse(struct nlattr **tb, int maxtype, const struct nlattr *head,
	      int len, const struct nla_policy *policy)
{
	const struct nlattr *nla;
	int rem, err;

	memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));

	nla_for_each_attr(nla, head, len, rem) {
		u16 type = nla_type(nla);

		if (type > 0 && type <= maxtype) {
			if (policy) {
				err = validate_nla(nla, maxtype, policy);
				if (err < 0)
					goto errout;
			}

			tb[type] = (struct nlattr *)nla;
		}
	}

	if (unlikely(rem > 0))
		pr_warn_ratelimited("netlink: %d bytes leftover after parsing attributes in process `%s'.\n",
				    rem, current->comm);

	err = 0;
errout:
	return err;
}

struct nlattr *nla_find(const struct nlattr *head, int len, int attrtype)
{
	const struct nlattr *nla;
	int rem;

	nla_for_each_attr(nla, head, len, rem)
		if (nla_type(nla) == attrtype)
			return (struct nlattr *)nla;

	return NULL;
}

size_t nla_strlcpy(char *dst, const struct nlattr *nla, size_t dstsize)
{
	size_t srclen = nla_len(nla);
	char *src = nla_data(nla);

	if (srclen > 0 && src[srclen - 1] == '\0')
		srclen--;

	if (dstsize > 0) {
		size_t len = (srclen >= dstsize) ? dstsize - 1 : srclen;

		memset(dst, 0, dstsize);
		memcpy(dst, src, len);
	}

	return srclen;
}

int nla_memcpy(void *dest, const struct nlattr *src, int count)
{
	int minlen = min_t(int, count, nla_len(src));

	memcpy(dest, nla_data(src), minlen);

	return minlen;
}

int nla_memcmp(const struct nlattr *nla, const void *data,
			     size_t size)
{
	int d = nla_len(nla) - size;

	if (d == 0)
		d = memcmp(nla_data(nla), data, size);

	return d;
}

int nla_strcmp(const struct nlattr *nla, const char *str)
{
	int len = strlen(str);
	char *buf = nla_data(nla);
	int attrlen = nla_len(nla);
	int d;

	if (attrlen > 0 && buf[attrlen - 1] == '\0')
		attrlen--;

	d = attrlen - len;
	if (d == 0)
		d = memcmp(nla_data(nla), str, len);

	return d;
}

#ifdef CONFIG_NET
struct nlattr *__nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
{
	struct nlattr *nla;

	nla = (struct nlattr *) skb_put(skb, nla_total_size(attrlen));
	nla->nla_type = attrtype;
	nla->nla_len = nla_attr_size(attrlen);

	memset((unsigned char *) nla + nla->nla_len, 0, nla_padlen(attrlen));

	return nla;
}
EXPORT_SYMBOL(__nla_reserve);

void *__nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
{
	void *start;

	start = skb_put(skb, NLA_ALIGN(attrlen));
	memset(start, 0, NLA_ALIGN(attrlen));

	return start;
}
EXPORT_SYMBOL(__nla_reserve_nohdr);

struct nlattr *nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
{
	if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
		return NULL;

	return __nla_reserve(skb, attrtype, attrlen);
}
EXPORT_SYMBOL(nla_reserve);

void *nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
{
	if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
		return NULL;

	return __nla_reserve_nohdr(skb, attrlen);
}
EXPORT_SYMBOL(nla_reserve_nohdr);

void __nla_put(struct sk_buff *skb, int attrtype, int attrlen,
			     const void *data)
{
	struct nlattr *nla;

	nla = __nla_reserve(skb, attrtype, attrlen);
	memcpy(nla_data(nla), data, attrlen);
}
EXPORT_SYMBOL(__nla_put);

void __nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
{
	void *start;

	start = __nla_reserve_nohdr(skb, attrlen);
	memcpy(start, data, attrlen);
}
EXPORT_SYMBOL(__nla_put_nohdr);

int nla_put(struct sk_buff *skb, int attrtype, int attrlen, const void *data)
{
	if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
		return -EMSGSIZE;

	__nla_put(skb, attrtype, attrlen, data);
	return 0;
}
EXPORT_SYMBOL(nla_put);

int nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
{
	if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
		return -EMSGSIZE;

	__nla_put_nohdr(skb, attrlen, data);
	return 0;
}
EXPORT_SYMBOL(nla_put_nohdr);

int nla_append(struct sk_buff *skb, int attrlen, const void *data)
{
	if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
		return -EMSGSIZE;

	memcpy(skb_put(skb, attrlen), data, attrlen);
	return 0;
}
EXPORT_SYMBOL(nla_append);
#endif

EXPORT_SYMBOL(nla_validate);
EXPORT_SYMBOL(nla_policy_len);
EXPORT_SYMBOL(nla_parse);
EXPORT_SYMBOL(nla_find);
EXPORT_SYMBOL(nla_strlcpy);
EXPORT_SYMBOL(nla_memcpy);
EXPORT_SYMBOL(nla_memcmp);
EXPORT_SYMBOL(nla_strcmp);