Commit afdc3238 authored by Patrick McHardy's avatar Patrick McHardy Committed by David S. Miller
Browse files

[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: default avatarPatrick McHardy <kaber@trash.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 1092cb21

include/linux/rtnetlink.h

+14 −0
Original line number Diff line number Diff line
@@ -570,6 +570,8 @@ static __inline__ int rtattr_strcmp(const struct rtattr *rta, const char *str) 
}



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 @@ extern void __rta_fill(struct sk_buff *skb, int attrtype, int attrlen, const voi 
({	(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); \

net/core/rtnetlink.c

+16 −0
Original line number Diff line number Diff line
@@ -97,6 +97,21 @@ int rtattr_parse(struct rtattr *tb[], int maxattr, struct rtattr *rta, int len) 
	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 @@ void __init rtnetlink_init(void) 
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);

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