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: Add nested compat attribute

IPROUTE Patrick McHardy 1 participant 2 messages Jun 22, 2007

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Patrick McHardy

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#0 lore raw

This patch adds a new attribute type that can be used to replace non-nested attributes that contain structures by nested ones in a compatible way.

This can be used in cases like Peter's who is trying to extend sch_prio, which currently uses a fixed structure without any holes.

Switching to nested attributes makes sure that the next person won't run into the same problem.

[IPROUTE]: 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 protected]>

---
commit d283ea3c852f54941ec785ad39dbfa4586f518c7
tree d2300d75cf50897386e670591fa963acd2bbd21b
parent cd71a8e07f57a74d52e62cc1fed39c03ad64bc08
author Patrick McHardy <[email protected]> Fri, 22 Jun 2007 17:59:27 +0200 committer Patrick McHardy <[email protected]> Fri, 22 Jun 2007 17:59:27 +0200

 include/libnetlink.h |    5 +++++
 lib/libnetlink.c     |   48 ++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 53 insertions(+), 0 deletions(-)
include/libnetlink.h +5 -0
index 49e248e..bd426e6 100644
@@ -39,11 +39,16 @@ extern int rtnl_send(struct rtnl_handle 
 extern int addattr32(struct nlmsghdr *n, int maxlen, int type, __u32 data);
 extern int addattr_l(struct nlmsghdr *n, int maxlen, int type, const void *data, int alen);
 extern int addraw_l(struct nlmsghdr *n, int maxlen, const void *data, int len);
+extern struct rtattr *addattr_nest(struct nlmsghdr *n, int maxlen, int type);
+extern int addattr_nest_end(struct nlmsghdr *n, struct rtattr *nest);
+extern struct rtattr *addattr_nest_compat(struct nlmsghdr *n, int maxlen, int type, const void *data, int len);
+extern int addattr_nest_compat_end(struct nlmsghdr *n, struct rtattr *nest);
 extern int rta_addattr32(struct rtattr *rta, int maxlen, int type, __u32 data);
 extern int rta_addattr_l(struct rtattr *rta, int maxlen, int type, const void *data, int alen);
 
 extern int parse_rtattr(struct rtattr *tb[], int max, struct rtattr *rta, int len);
 extern int parse_rtattr_byindex(struct rtattr *tb[], int max, struct rtattr *rta, int len);
+extern int parse_rtattr_nested_compat(struct rtattr *tb[], int max, struct rtattr *rta, void **data, int len);
 
 #define parse_rtattr_nested(tb, max, rta) \
 	(parse_rtattr((tb), (max), RTA_DATA(rta), RTA_PAYLOAD(rta)))
lib/libnetlink.c +48 -0

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author
#1 lore raw
Quoted 3 lines · Patrick McHardy

extern int parse_rtattr(struct rtattr *tb[], int max, struct rtattr *rta, int len);
extern int parse_rtattr_byindex(struct rtattr *tb[], int max, struct rtattr *rta, int len);
+extern int parse_rtattr_nested_compat(struct rtattr *tb[], int max, struct rtattr *rta, void **data, int len);

Same change as in the kernel patch, avoid cast in caller and make the signature match existing ones better.

[IPROUTE]: 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 protected]>

---
commit 7d4cee8b6e0ddceda300ad1e4242cd068a722f0c
tree ea8b1245518d6ed352ef5d8e379588fa76981de9
parent cd71a8e07f57a74d52e62cc1fed39c03ad64bc08
author Patrick McHardy <[email protected]> Fri, 22 Jun 2007 19:13:08 +0200 committer Patrick McHardy <[email protected]> Fri, 22 Jun 2007 19:13:08 +0200

 include/libnetlink.h |    9 +++++++++
 lib/libnetlink.c     |   46 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 55 insertions(+), 0 deletions(-)
include/libnetlink.h +9 -0
index 49e248e..b67c5a5 100644
@@ -39,15 +39,24 @@ extern int rtnl_send(struct rtnl_handle 
 extern int addattr32(struct nlmsghdr *n, int maxlen, int type, __u32 data);
 extern int addattr_l(struct nlmsghdr *n, int maxlen, int type, const void *data, int alen);
 extern int addraw_l(struct nlmsghdr *n, int maxlen, const void *data, int len);
+extern struct rtattr *addattr_nest(struct nlmsghdr *n, int maxlen, int type);
+extern int addattr_nest_end(struct nlmsghdr *n, struct rtattr *nest);
+extern struct rtattr *addattr_nest_compat(struct nlmsghdr *n, int maxlen, int type, const void *data, int len);
+extern int addattr_nest_compat_end(struct nlmsghdr *n, struct rtattr *nest);
 extern int rta_addattr32(struct rtattr *rta, int maxlen, int type, __u32 data);
 extern int rta_addattr_l(struct rtattr *rta, int maxlen, int type, const void *data, int alen);
 
 extern int parse_rtattr(struct rtattr *tb[], int max, struct rtattr *rta, int len);
 extern int parse_rtattr_byindex(struct rtattr *tb[], int max, struct rtattr *rta, int len);
+extern int __parse_rtattr_nested_compat(struct rtattr *tb[], int max, struct rtattr *rta, int len);
 
 #define parse_rtattr_nested(tb, max, rta) \
 	(parse_rtattr((tb), (max), RTA_DATA(rta), RTA_PAYLOAD(rta)))
 
+#define parse_rtattr_nested_compat(tb, max, rta, data, len) \
+({	data = RTA_PAYLOAD(rta) >= len ? RTA_DATA(rta) : NULL; \
+	__parse_rtattr_nested_compat(tb, max, rta, len); })
+
 extern int rtnl_listen(struct rtnl_handle *, rtnl_filter_t handler,
 		       void *jarg);
 extern int rtnl_from_file(FILE *, rtnl_filter_t handler,
lib/libnetlink.c +46 -0

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