netdev - Re: Sending big Netlink messages to userspace

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Message-ID: <f4845fc0806251156m5c6405c9w65cd126c1e5551ce@mail.gmail.com>
Date:	Wed, 25 Jun 2008 20:56:35 +0200
From:	"Julius Volz" <juliusv@...gle.com>
To:	"Thomas Graf" <tgraf@...g.ch>
Cc:	"Patrick McHardy" <kaber@...sh.net>, netdev@...r.kernel.org,
	"Vince Busam" <vbusam@...gle.com>
Subject: Re: Sending big Netlink messages to userspace

On Wed, Jun 25, 2008, Thomas Graf wrote:
> libnl initializes the buffer size to the size of a page. The value
> can be overwritten by calling nl_set_buffer_size(socket, rx, tx)

Thanks, I missed that. Though now I won't need that anymore as I got
the dump working!

> Yes, that's how it's intended to work. You can fill until one of the
> nla_put variantes aborts and starting trimming off what you've added
> already using the nla_nest_cancel() methods until you reach a point
> where you can safely cut your stream of attributes. So far we typically
> made sure that this barrier is on netlink message level but is no
> requirement. You may split a list into several messages you just
> have to make sure that you call nla_nest_end() and nlmsg_end() properly
> before you send the message.

Ok, I did exactly that! Took me a while to figure out all of the
necessary quirks (including userland), but now it works! :)

So userspace now gets one callback invocation per part of a multipart
message. I guess it's not possible to aggregate the data into just one
callback invocation?

Thanks again!
Julius

-- 
Google Switzerland GmbH
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