netdev - Re: question about nla_nest

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Message-ID: <87pqrikzd6.fsf@benpfaff.org>
Date:	Thu, 27 Jan 2011 09:52:53 -0800
From:	Ben Pfaff <blp@...stanford.edu>
To:	Julia Lawall <julia@...u.dk>
Cc:	hadi@...erus.ca, netdev@...r.kernel.org
Subject: Re: question about nla_nest_cancel

Julia Lawall <julia@...u.dk> writes:

> I find numerous occurrences of code like the following, in which nest ends 
> up with the value NULL and then nla_nest_cancel is called with nest as the 
> second argument.  But nla_nest_cancel just calls nlmsg_trim with the same 
> second argument, and nlmsg_trim does nothing if its second argument is 
> NULL.  Is there any reason to keep these calls?

I think that you are missing that NLA_PUT() contains an internal
"goto nla_put_failure;".  If that branch is taken, then
nla_nest_cancel() trims off the nested attribute.  So just
removing the call to nla_nest_cancel() would change behavior in
that case.
-- 
Ben Pfaff 
http://benpfaff.org
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