From: Al Viro <viro@ZenIV.linux.org.uk>
To: Florian Westphal <fw@strlen.de>
Cc: David Miller <davem@davemloft.net>,
kaber@trash.net, netdev@vger.kernel.org
Subject: Re: [WTF?] random test in netlink_sendmsg()
Date: Fri, 12 Dec 2014 22:14:10 +0000 [thread overview]
Message-ID: <20141212221410.GF22149@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20141212215017.GB3624@breakpoint.cc>
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). _That_ is equivalent to msg.msg_iovlen = 1, msg.msg_iov =
&(struct iovec){NULL, 0} (and that explains the origin of the odd check,
I suppose). The case where it goes random is different - msg.msg_iovlen = 0,
msg.msg_iov - anything, will be ignored by sys_sendmsg().
next prev parent reply other threads:[~2014-12-12 22:14 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-28 6:23 [WTF?] random test in netlink_sendmsg() Al Viro
2014-12-12 20:34 ` David Miller
2014-12-12 21:32 ` Al Viro
2014-12-12 21:50 ` Florian Westphal
2014-12-12 22:14 ` Al Viro [this message]
2014-12-12 22:20 ` Florian Westphal
2014-12-13 1:07 ` David Miller
2014-12-13 1:54 ` Al Viro
2014-12-13 2:33 ` David Miller
2014-12-13 3:25 ` Al Viro
2014-12-13 4:51 ` Al Viro
2014-12-14 4:38 ` David Miller
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20141212221410.GF22149@ZenIV.linux.org.uk \
--to=viro@zeniv.linux.org.uk \
--cc=davem@davemloft.net \
--cc=fw@strlen.de \
--cc=kaber@trash.net \
--cc=netdev@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).