netlink: Move netlink attribute parsing support to lib

Netlink attribute parsing may be used even if CONFIG_NET is not set.
Move it from net/netlink to lib and control its inclusion based on the new
config symbol CONFIG_NLATTR, which is selected by CONFIG_NET.

Signed-off-by: Geert Uytterhoeven <Geert.Uytterhoeven@sonycom.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

3 files changed, 481 insertions, 0 deletions

diff --git a/lib/Kconfig b/lib/Kconfig
index 03c2c24b9083..cea9e30a88ff 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -174,4 +174,10 @@ config DISABLE_OBSOLETE_CPUMASK_FUNCTIONS
        bool "Disable obsolete cpumask functions" if DEBUG_PER_CPU_MAPS
        depends on EXPERIMENTAL && BROKEN
 
+#
+# Netlink attribute parsing support is select'ed if needed
+#
+config NLATTR
+        bool
+
 endmenu
diff --git a/lib/Makefile b/lib/Makefile
index 32b0e64ded27..b2c09da02cae 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -84,6 +84,8 @@ obj-$(CONFIG_HAVE_ARCH_TRACEHOOK) += syscall.o
 
 obj-$(CONFIG_DYNAMIC_PRINTK_DEBUG) += dynamic_printk.o
 
+obj-$(CONFIG_NLATTR) += nlattr.o
+
 hostprogs-y     := gen_crc32table
 clean-files     := crc32table.h
 
diff --git a/lib/nlattr.c b/lib/nlattr.c
new file mode 100644
index 000000000000..56c3ce7fe29a
--- /dev/null
+++ b/lib/nlattr.c
@@ -0,0 +1,473 @@
+/*
+ * NETLINK      Netlink attributes
+ *
+ *              Authors:        Thomas Graf <tgraf@suug.ch>
+ *                              Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
+ */
+
+#include <linux/module.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 <net/netlink.h>
+
+static u16 nla_attr_minlen[NLA_TYPE_MAX+1] __read_mostly = {
+        [NLA_U8]        = sizeof(u8),
+        [NLA_U16]       = sizeof(u16),
+        [NLA_U32]       = sizeof(u32),
+        [NLA_U64]       = sizeof(u64),
+        [NLA_NESTED]    = NLA_HDRLEN,
+};
+
+static int validate_nla(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;
+                /* fall through */
+
+        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:
+                /* a nested attributes is allowed to be empty; if its not,
+                 * it must have a size of at least NLA_HDRLEN.
+                 */
+                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;
+}
+
+/**
+ * nla_validate - Validate a stream of attributes
+ * @head: head of attribute stream
+ * @len: length of attribute stream
+ * @maxtype: maximum attribute type to be expected
+ * @policy: validation policy
+ *
+ * Validates all attributes in the specified attribute stream against the
+ * specified policy. Attributes with a type exceeding maxtype will be
+ * ignored. See documenation of struct nla_policy for more details.
+ *
+ * Returns 0 on success or a negative error code.
+ */
+int nla_validate(struct nlattr *head, int len, int maxtype,
+                 const struct nla_policy *policy)
+{
+        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;
+}
+
+/**
+ * nla_parse - Parse a stream of attributes into a tb buffer
+ * @tb: destination array with maxtype+1 elements
+ * @maxtype: maximum attribute type to be expected
+ * @head: head of attribute stream
+ * @len: length of attribute stream
+ * @policy: validation policy
+ *
+ * Parses a stream of attributes and stores a pointer to each attribute in
+ * the tb array accessable via the attribute type. Attributes with a type
+ * exceeding maxtype will be silently ignored for backwards compatibility
+ * reasons. policy may be set to NULL if no validation is required.
+ *
+ * Returns 0 on success or a negative error code.
+ */
+int nla_parse(struct nlattr *tb[], int maxtype, struct nlattr *head, int len,
+              const struct nla_policy *policy)
+{
+        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] = nla;
+                }
+        }
+
+        if (unlikely(rem > 0))
+                printk(KERN_WARNING "netlink: %d bytes leftover after parsing "
+                       "attributes.\n", rem);
+
+        err = 0;
+errout:
+        return err;
+}
+
+/**
+ * nla_find - Find a specific attribute in a stream of attributes
+ * @head: head of attribute stream
+ * @len: length of attribute stream
+ * @attrtype: type of attribute to look for
+ *
+ * Returns the first attribute in the stream matching the specified type.
+ */
+struct nlattr *nla_find(struct nlattr *head, int len, int attrtype)
+{
+        struct nlattr *nla;
+        int rem;
+
+        nla_for_each_attr(nla, head, len, rem)
+                if (nla_type(nla) == attrtype)
+                        return nla;
+
+        return NULL;
+}
+
+/**
+ * nla_strlcpy - Copy string attribute payload into a sized buffer
+ * @dst: where to copy the string to
+ * @nla: attribute to copy the string from
+ * @dstsize: size of destination buffer
+ *
+ * Copies at most dstsize - 1 bytes into the destination buffer.
+ * The result is always a valid NUL-terminated string. Unlike
+ * strlcpy the destination buffer is always padded out.
+ *
+ * Returns the length of the source buffer.
+ */
+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;
+}
+
+/**
+ * nla_memcpy - Copy a netlink attribute into another memory area
+ * @dest: where to copy to memcpy
+ * @src: netlink attribute to copy from
+ * @count: size of the destination area
+ *
+ * Note: The number of bytes copied is limited by the length of
+ *       attribute's payload. memcpy
+ *
+ * Returns the number of bytes copied.
+ */
+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;
+}
+
+/**
+ * nla_memcmp - Compare an attribute with sized memory area
+ * @nla: netlink attribute
+ * @data: memory area
+ * @size: size of memory area
+ */
+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;
+}
+
+/**
+ * nla_strcmp - Compare a string attribute against a string
+ * @nla: netlink string attribute
+ * @str: another string
+ */
+int nla_strcmp(const struct nlattr *nla, const char *str)
+{
+        int len = strlen(str) + 1;
+        int d = nla_len(nla) - len;
+
+        if (d == 0)
+                d = memcmp(nla_data(nla), str, len);
+
+        return d;
+}
+
+/**
+ * __nla_reserve - reserve room for attribute on the skb
+ * @skb: socket buffer to reserve room on
+ * @attrtype: attribute type
+ * @attrlen: length of attribute payload
+ *
+ * Adds a netlink attribute header to a socket buffer and reserves
+ * room for the payload but does not copy it.
+ *
+ * The caller is responsible to ensure that the skb provides enough
+ * tailroom for the attribute header and payload.
+ */
+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;
+}
+
+/**
+ * __nla_reserve_nohdr - reserve room for attribute without header
+ * @skb: socket buffer to reserve room on
+ * @attrlen: length of attribute payload
+ *
+ * Reserves room for attribute payload without a header.
+ *
+ * The caller is responsible to ensure that the skb provides enough
+ * tailroom for the payload.
+ */
+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;
+}
+
+/**
+ * nla_reserve - reserve room for attribute on the skb
+ * @skb: socket buffer to reserve room on
+ * @attrtype: attribute type
+ * @attrlen: length of attribute payload
+ *
+ * Adds a netlink attribute header to a socket buffer and reserves
+ * room for the payload but does not copy it.
+ *
+ * Returns NULL if the tailroom of the skb is insufficient to store
+ * the attribute header and payload.
+ */
+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);
+}
+
+/**
+ * nla_reserve_nohdr - reserve room for attribute without header
+ * @skb: socket buffer to reserve room on
+ * @attrlen: length of attribute payload
+ *
+ * Reserves room for attribute payload without a header.
+ *
+ * Returns NULL if the tailroom of the skb is insufficient to store
+ * the attribute payload.
+ */
+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);
+}
+
+/**
+ * __nla_put - Add a netlink attribute to a socket buffer
+ * @skb: socket buffer to add attribute to
+ * @attrtype: attribute type
+ * @attrlen: length of attribute payload
+ * @data: head of attribute payload
+ *
+ * The caller is responsible to ensure that the skb provides enough
+ * tailroom for the attribute header and payload.
+ */
+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);
+}
+
+/**
+ * __nla_put_nohdr - Add a netlink attribute without header
+ * @skb: socket buffer to add attribute to
+ * @attrlen: length of attribute payload
+ * @data: head of attribute payload
+ *
+ * The caller is responsible to ensure that the skb provides enough
+ * tailroom for the attribute payload.
+ */
+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);
+}
+
+/**
+ * nla_put - Add a netlink attribute to a socket buffer
+ * @skb: socket buffer to add attribute to
+ * @attrtype: attribute type
+ * @attrlen: length of attribute payload
+ * @data: head of attribute payload
+ *
+ * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
+ * the attribute header and payload.
+ */
+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;
+}
+
+/**
+ * nla_put_nohdr - Add a netlink attribute without header
+ * @skb: socket buffer to add attribute to
+ * @attrlen: length of attribute payload
+ * @data: head of attribute payload
+ *
+ * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
+ * the attribute payload.
+ */
+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;
+}
+
+/**
+ * nla_append - Add a netlink attribute without header or padding
+ * @skb: socket buffer to add attribute to
+ * @attrlen: length of attribute payload
+ * @data: head of attribute payload
+ *
+ * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
+ * the attribute payload.
+ */
+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_validate);
+EXPORT_SYMBOL(nla_parse);
+EXPORT_SYMBOL(nla_find);
+EXPORT_SYMBOL(nla_strlcpy);
+EXPORT_SYMBOL(__nla_reserve);
+EXPORT_SYMBOL(__nla_reserve_nohdr);
+EXPORT_SYMBOL(nla_reserve);
+EXPORT_SYMBOL(nla_reserve_nohdr);
+EXPORT_SYMBOL(__nla_put);
+EXPORT_SYMBOL(__nla_put_nohdr);
+EXPORT_SYMBOL(nla_put);
+EXPORT_SYMBOL(nla_put_nohdr);
+EXPORT_SYMBOL(nla_memcpy);
+EXPORT_SYMBOL(nla_memcmp);
+EXPORT_SYMBOL(nla_strcmp);
+EXPORT_SYMBOL(nla_append);