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(-)
diff --git a/include/libnetlink.h b/include/libnetlink.h
index 49e248e..bd426e6 100644
--- a/include/libnetlink.h
+++ b/include/libnetlink.h
@@ -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)))
diff --git a/lib/libnetlink.c b/lib/libnetlink.c
index 555dd5c..2add7e9 100644
--- a/lib/libnetlink.c
+++ b/lib/libnetlink.c
@@ -527,6 +527,39 @@ int addraw_l(struct nlmsghdr *n, int max
return 0;
}
+struct rtattr *addattr_nest(struct nlmsghdr *n, int maxlen, int type)
+{
+ struct rtattr *nest = NLMSG_TAIL(n);
+
+ addattr_l(n, maxlen, type, NULL, 0);
+ return nest;
+}
+
+int addattr_nest_end(struct nlmsghdr *n, struct rtattr *nest)
+{
+ nest->rta_len = (void *)NLMSG_TAIL(n) - (void *)nest;
+ return n->nlmsg_len;
+}
+
+struct rtattr *addattr_nest_compat(struct nlmsghdr *n, int maxlen, int type,
+ const void *data, int len)
+{
+ struct rtattr *start = NLMSG_TAIL(n);
+
+ addattr_l(n, maxlen, type, data, len);
+ addattr_nest(n, maxlen, type);
+ return start;
+}
+
+int addattr_nest_compat_end(struct nlmsghdr *n, struct rtattr *start)
+{
+ struct rtattr *nest = (void *)start + NLMSG_ALIGN(start->rta_len);
+
+ start->rta_len = (void *)NLMSG_TAIL(n) - (void *)start;
+ addattr_nest_end(n, nest);
+ return n->nlmsg_len;
+}
+
int rta_addattr32(struct rtattr *rta, int maxlen, int type, __u32 data)
{
int len = RTA_LENGTH(4);
@@ -589,3 +622,18 @@ int parse_rtattr_byindex(struct rtattr *
fprintf(stderr, "!!!Deficit %d, rta_len=%d\n", len, rta->rta_len);
return i;
}
+
+int parse_rtattr_nested_compat(struct rtattr *tb[], int max, 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 parse_rtattr_nested(tb, max, rta);
+ }
+ memset(tb, 0, sizeof(struct rtattr *) * max);
+ return 0;
+}
