[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/include/linux/rtnetlink.h b/include/linux/rtnetlink.h
index 6127858..6731e7f 100644
--- a/include/linux/rtnetlink.h
+++ b/include/linux/rtnetlink.h
@@ -570,6 +570,8 @@
}
extern int rtattr_parse(struct rtattr *tb[], int maxattr, struct rtattr *rta, int len);
+extern int rtattr_parse_nested_compat(struct rtattr *tb[], int maxattr,
+ struct rtattr *rta, void **data, int len);
#define rtattr_parse_nested(tb, max, rta) \
rtattr_parse((tb), (max), RTA_DATA((rta)), RTA_PAYLOAD((rta)))
@@ -638,6 +640,18 @@
({ (start)->rta_len = skb_tail_pointer(skb) - (unsigned char *)(start); \
(skb)->len; })
+#define RTA_NEST_COMPAT(skb, type, attrlen, data) \
+({ struct rtattr *__start = (struct rtattr *)skb_tail_pointer(skb); \
+ RTA_PUT(skb, type, attrlen, data); \
+ RTA_NEST(skb, type); \
+ __start; })
+
+#define RTA_NEST_COMPAT_END(skb, start) \
+({ struct rtattr *__nest = (void *)(start) + NLMSG_ALIGN((start)->rta_len); \
+ (start)->rta_len = skb_tail_pointer(skb) - (unsigned char *)(start); \
+ RTA_NEST_END(skb, __nest); \
+ (skb)->len; })
+
#define RTA_NEST_CANCEL(skb, start) \
({ if (start) \
skb_trim(skb, (unsigned char *) (start) - (skb)->data); \