From mboxrd@z Thu Jan  1 00:00:00 1970
From: Florian Westphal <fw@strlen.de>
Subject: Re: [WTF?] random test in netlink_sendmsg()
Date: Fri, 12 Dec 2014 23:20:21 +0100
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Cc: Florian Westphal <fw@strlen.de>,
	David Miller <davem@davemloft.net>, kaber@trash.net,
	netdev@vger.kernel.org
To: Al Viro <viro@ZenIV.linux.org.uk>
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Al Viro <viro@ZenIV.linux.org.uk> wrote:
> On Fri, Dec 12, 2014 at 10:50:17PM +0100, Florian Westphal wrote:
> 
> > > 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?  Userland ABI question
> > 
> > IIRC userland, after filling txring with at least one new netlink
> > message, needs to call this to tell kernel to start processing the
> > messages in the tx ring.
> 
> AFAICS, the suggested way to initiate transmission is sendto(fd, NULL, 0, ...),
> not sendmsg(2).

Indeed, you're right.