From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: [WTF?] random test in netlink_sendmsg()
Date: Fri, 12 Dec 2014 20:07:58 -0500 (EST)
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From: Al Viro <viro@ZenIV.linux.org.uk>
Date: Fri, 12 Dec 2014 21:32:43 +0000

> What do we want sendmsg(fd, &msg, 0) to do when fd is AF_NETLINK socket
> that had setsockopt(fd, SOL_NETLINK, NETLINK_TX_RING, ...) successfully done
> to it and msg.msg_iovlen is 0?

We had a similar issue with msg_name/msg_namelen and we ended up saying
that if msg_namelen is zero then we force msg_name to NULL.