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attr: Add nla_nest_cancel() to remove partially added nested attributes

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Signed-off-by: Thomas Graf <tgraf@suug.ch>
This commit is contained in:
Thomas Graf 2013-03-13 16:53:07 +01:00
parent 4d7680c19c
commit 9e6cdbf6fc
3 changed files with 25 additions and 2 deletions
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1
doc/core.txt
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@ -2316,6 +2316,7 @@ int put_opts(struct nl_msg *msg)
return 0;
nla_put_failure:
nla_nest_cancel(msg, opts);
return -EMSGSIZE;
}
--------

1
include/netlink/attr.h
View file

@ -124,6 +124,7 @@ extern int nla_put_msecs(struct nl_msg *, int, unsigned long);
extern int nla_put_nested(struct nl_msg *, int, struct nl_msg *);
extern struct nlattr * nla_nest_start(struct nl_msg *, int);
extern int nla_nest_end(struct nl_msg *, struct nlattr *);
extern void nla_nest_cancel(struct nl_msg *, struct nlattr *);
extern int nla_parse_nested(struct nlattr **, int, struct nlattr *,
struct nla_policy *);
extern int nla_is_nested(struct nlattr *);

25
lib/attr.c
View file

@ -820,8 +820,7 @@ int nla_nest_end(struct nl_msg *msg, struct nlattr *start)
* Kernel can't handle empty nested attributes, trim the
* attribute header again
*/
msg->nm_nlh->nlmsg_len -= NLA_HDRLEN;
memset(nlmsg_tail(msg->nm_nlh), 0, NLA_HDRLEN);
nla_nest_cancel(msg, start);
return 0;
}
@ -849,6 +848,28 @@ int nla_nest_end(struct nl_msg *msg, struct nlattr *start)
return 0;
}
/**
* Cancel the addition of a nested attribute
* @arg msg Netlink message
* @arg attr Nested netlink attribute
*
* Removes any partially added nested Netlink attribute from the message
* by resetting the message to the size before the call to nla_nest_start()
* and by overwriting any potentially touched message segments with 0.
*/
void nla_nest_cancel(struct nl_msg *msg, struct nlattr *attr)
{
ssize_t len;
len = (void *) nlmsg_tail(msg->nm_nlh) - (void *) attr;
if (len < 0)
BUG();
else if (len > 0) {
msg->nm_nlh->nlmsg_len -= len;
memset(nlmsg_tail(msg->nm_nlh), 0, len);
}
}
/**
* Create attribute index based on nested attribute
* @arg tb Index array to be filled (maxtype+1 elements).