netdev - Re: Sending big Netlink messages to userspace

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Message-ID: <4862E5B0.9080007@trash.net>
Date:	Thu, 26 Jun 2008 02:41:20 +0200
From:	Patrick McHardy <kaber@...sh.net>
To:	David Miller <davem@...emloft.net>
CC:	tgraf@...g.ch, juliusv@...gle.com, netdev@...r.kernel.org,
	vbusam@...gle.com
Subject: Re: Sending big Netlink messages to userspace

David Miller wrote:
> From: Thomas Graf <tgraf@...g.ch>
> Date: Wed, 25 Jun 2008 12:44:01 +0200
> 
>> 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)
> 
> And it doesn't need to be any larger than a page.  Actually, the
> hard upper bound is 8K.
> 
> The kernel will always chop the response up into chunks of that
> size or smaller when generating replies to userspace.
> 
> Therefore userland need never have a buffer larger than 8K or
> sysconf(_SC_PAGESIZE), whichever is smaller.

For dumps the size is fine, for large unicast messages it
might need to be increased though (like nfnetlink_queue).

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