netdev - Re: [PATCH net-next 0/7] Allow to monitor multicast cache event via rtnetlink

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Message-ID: <20121207105809.GC2996@casper.infradead.org>
Date:	Fri, 7 Dec 2012 10:58:09 +0000
From:	Thomas Graf <tgraf@...g.ch>
To:	David Laight <David.Laight@...LAB.COM>
Cc:	Nicolas Dichtel <nicolas.dichtel@...nd.com>,
	David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next 0/7] Allow to monitor multicast cache event via
 rtnetlink

On 12/07/12 at 10:38am, David Laight wrote:
> What are you going to align the data with respect to?
> I doubt you can assume that the start of the netlink
> message itself is 8 byte aligned - so any attempt
> to 8 byte align an item is probably doomed to failure.

Correct me if I'm wrong but skb->head will be aligned to
SKB_DATA_ALIGN() which as I understand is guaranted to
be 8 bytse aligned. So we can just add needed padding if
skb->data would not be aligned correctly after the next
netlink attribute header was added.

All user space needs to do is use a receive buffer that
is 8 byte aligned as well and we are good to go.
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