[NETLINK]: attr: add nested compat attribute type
Add a nested compat attribute type that can be used to convert
attributes that contain a structure to nested attributes in a
backwards compatible way.
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/netlink.h b/include/net/netlink.h
index 7b510a9..d7b824b 100644
--- a/include/net/netlink.h
+++ b/include/net/netlink.h
@@ -118,6 +118,9 @@
* Nested Attributes Construction:
* nla_nest_start(skb, type) start a nested attribute
* nla_nest_end(skb, nla) finalize a nested attribute
+ * nla_nest_compat_start(skb, type, start a nested compat attribute
+ * len, data)
+ * nla_nest_compat_end(skb, type) finalize a nested compat attribute
* nla_nest_cancel(skb, nla) cancel nested attribute construction
*
* Attribute Length Calculations:
@@ -152,6 +155,7 @@
* nla_find_nested() find attribute in nested attributes
* nla_parse() parse and validate stream of attrs
* nla_parse_nested() parse nested attribuets
+ * nla_parse_nested_compat() parse nested compat attributes
* nla_for_each_attr() loop over all attributes
* nla_for_each_nested() loop over the nested attributes
*=========================================================================
@@ -170,6 +174,7 @@
NLA_FLAG,
NLA_MSECS,
NLA_NESTED,
+ NLA_NESTED_COMPAT,
NLA_NUL_STRING,
NLA_BINARY,
__NLA_TYPE_MAX,
@@ -190,6 +195,7 @@
* NLA_NUL_STRING Maximum length of string (excluding NUL)
* NLA_FLAG Unused
* NLA_BINARY Maximum length of attribute payload
+ * NLA_NESTED_COMPAT Exact length of structure payload
* All other Exact length of attribute payload
*
* Example:
@@ -733,6 +739,39 @@
{
return nla_parse(tb, maxtype, nla_data(nla), nla_len(nla), policy);
}
+
+/**
+ * nla_parse_nested_compat - parse nested compat attributes
+ * @tb: destination array with maxtype+1 elements
+ * @maxtype: maximum attribute type to be expected
+ * @nla: attribute containing the nested attributes
+ * @data: pointer to point to contained structure
+ * @len: length of contained structure
+ * @policy: validation policy
+ *
+ * Parse a nested compat attribute. The compat attribute contains a structure
+ * and optionally a set of nested attributes. On success the data pointer
+ * points to the nested data and tb contains the parsed attributes
+ * (see nla_parse).
+ */
+static inline int __nla_parse_nested_compat(struct nlattr *tb[], int maxtype,
+ struct nlattr *nla,
+ const struct nla_policy *policy,
+ int len)
+{
+ if (nla_len(nla) < len)
+ return -1;
+ if (nla_len(nla) >= NLA_ALIGN(len) + sizeof(struct nlattr))
+ return nla_parse_nested(tb, maxtype,
+ nla_data(nla) + NLA_ALIGN(len),
+ policy);
+ memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
+ return 0;
+}
+
+#define nla_parse_nested_compat(tb, maxtype, nla, policy, data, len) \
+({ data = nla_len(nla) >= len ? nla_data(nla) : NULL; \
+ __nla_parse_nested_compat(tb, maxtype, nla, policy, len); })
/**
* nla_put_u8 - Add a u16 netlink attribute to a socket buffer
* @skb: socket buffer to add attribute to
@@ -965,6 +1004,51 @@
}
/**
+ * nla_nest_compat_start - Start a new level of nested compat attributes
+ * @skb: socket buffer to add attributes to
+ * @attrtype: attribute type of container
+ * @attrlen: length of structure
+ * @data: pointer to structure
+ *
+ * Start a nested compat attribute that contains both a structure and
+ * a set of nested attributes.
+ *
+ * Returns the container attribute
+ */
+static inline struct nlattr *nla_nest_compat_start(struct sk_buff *skb,
+ int attrtype, int attrlen,
+ const void *data)
+{
+ struct nlattr *start = (struct nlattr *)skb_tail_pointer(skb);
+
+ if (nla_put(skb, attrtype, attrlen, data) < 0)
+ return NULL;
+ if (nla_nest_start(skb, attrtype) == NULL) {
+ nlmsg_trim(skb, start);
+ return NULL;
+ }
+ return start;
+}
+
+/**
+ * nla_nest_compat_end - Finalize nesting of compat attributes
+ * @skb: socket buffer the attribtues are stored in
+ * @start: container attribute
+ *
+ * Corrects the container attribute header to include the all
+ * appeneded attributes.
+ *
+ * Returns the total data length of the skb.
+ */
+static inline int nla_nest_compat_end(struct sk_buff *skb, struct nlattr *start)
+{
+ struct nlattr *nest = (void *)start + NLMSG_ALIGN(start->nla_len);
+
+ start->nla_len = skb_tail_pointer(skb) - (unsigned char *)start;
+ return nla_nest_end(skb, nest);
+}
+
+/**
* nla_nest_cancel - Cancel nesting of attributes
* @skb: socket buffer the message is stored in
* @start: container attribute
diff --git a/net/netlink/attr.c b/net/netlink/attr.c
index c591212..e4d7bed 100644
--- a/net/netlink/attr.c
+++ b/net/netlink/attr.c
@@ -72,6 +72,17 @@
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;
default:
if (pt->len)
minlen = pt->len;