[RTNETLINK]: Add nested compat attribute
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.
The attribute looks like this:
struct {
[ compat contents ]
struct rtattr {
.rta_len = total size,
.rta_type = type,
} rta;
struct old_structure struct;
[ nested top-level attribute ]
struct rtattr {
.rta_len = nest size,
.rta_type = type,
} nest_attr;
[ optional 0 .. n nested attributes ]
struct rtattr {
.rta_len = private attribute len,
.rta_type = private attribute typ,
} nested_attr;
struct nested_data data;
};
Since both userspace and kernel deal correctly with attributes that are
larger than expected old versions will just parse the compat part and
ignore the rest.
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 06c0c5a..c25d23b 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -97,6 +97,21 @@
return 0;
}
+int rtattr_parse_nested_compat(struct rtattr *tb[], int maxattr,
+ struct rtattr *rta, void **data, int len)
+{
+ if (RTA_PAYLOAD(rta) < len)
+ return -1;
+ *data = RTA_DATA(rta);
+
+ if (RTA_PAYLOAD(rta) >= RTA_ALIGN(len) + sizeof(struct rtattr)) {
+ rta = RTA_DATA(rta) + RTA_ALIGN(len);
+ return rtattr_parse_nested(tb, maxattr, rta);
+ }
+ memset(tb, 0, sizeof(struct rtattr *) * maxattr);
+ return 0;
+}
+
static struct rtnl_link *rtnl_msg_handlers[NPROTO];
static inline int rtm_msgindex(int msgtype)
@@ -1297,6 +1312,7 @@
EXPORT_SYMBOL(__rta_fill);
EXPORT_SYMBOL(rtattr_strlcpy);
EXPORT_SYMBOL(rtattr_parse);
+EXPORT_SYMBOL(rtattr_parse_nested_compat);
EXPORT_SYMBOL(rtnetlink_put_metrics);
EXPORT_SYMBOL(rtnl_lock);
EXPORT_SYMBOL(rtnl_trylock);