Subject: Re: [RTNETLINK]: Add nested compat attribute

From: Patrick McHardy <[email-masked]>
Date: Mon, 25 Jun 2007 23:08:09 +0200

David Miller wrote:
>
>> I've been using this patch and the IPROUTE2 patches Patrick has proposed
>> with no issues.  Can someone else look at these patches when they have
>> time?  I'd be interested in seeing them make it into 2.6.23.
>>     
>
> I've just put Patrick's patch into the net-2.6.23 tree.
>   

You seem to have added the netlink patch for the generic
netlink attributes. Peter needs the rtnetlink attribute
patch since qdiscs still use the old stuff.

Attached again to this mail.

[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 <[email-masked]>

---
commit dece87e23c7cfa1159d3be0ea5b0db89a0fc5872
tree c14be602de94b258e0343816b6c1809233a2ff5f
parent c4edf5d552b1450d903a7e7e2d846f2169087e10
author Patrick McHardy <[email-masked]> Fri, 22 Jun 2007 17:52:21 +0200
committer Patrick McHardy <[email-masked]> Fri, 22 Jun 2007 17:52:21 +0200

 include/linux/rtnetlink.h |   14 ++++++++++++++
 net/core/rtnetlink.c      |   16 ++++++++++++++++
 2 files changed, 30 insertions(+), 0 deletions(-)

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 @@ static __inline__ int rtattr_strcmp(cons
 }
 
 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 @@ #define RTA_NEST_END(skb, start) \
 ({	(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); \
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 @@ int rtattr_parse(struct rtattr *tb[], in
 	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);