From: Patrick McHardy <kaber@trash.net>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: David Miller <davem@davemloft.net>,
nhorman@tuxdriver.com, zbr@ioremap.net, netdev@vger.kernel.org,
kuznet@ms2.inr.ac.ru, pekkas@netcore.fi, jmorris@namei.org,
yoshfuji@linux-ipv6.org
Subject: Re: [Patch 4/5] Network Drop Monitor: Adding drop monitor implementation & Netlink protocol
Date: Thu, 02 Apr 2009 16:42:18 +0200 [thread overview]
Message-ID: <49D4CECA.3010703@trash.net> (raw)
In-Reply-To: <20090402095957.GA30799@gondor.apana.org.au>
Herbert Xu wrote:
> On Thu, Apr 02, 2009 at 02:52:23AM -0700, David Miller wrote:
>> It has to do with how the netlink attributes get packed together
>> into the messages. It's this crap:
>>
>> #define NLMSG_ALIGNTO 4
>> #define NLMSG_ALIGN(len) ( ((len)+NLMSG_ALIGNTO-1) & ~(NLMSG_ALIGNTO-1) )
>> ...
>> #define NLMSG_NEXT(nlh,len) ((len) -= NLMSG_ALIGN((nlh)->nlmsg_len), \
>> (struct nlmsghdr*)(((char*)(nlh)) + NLMSG_ALIGN((nlh)->nlmsg_len)))
>>
>> Thus, nothing in an nlmsg can ever be more than 4 byte aligned.
>> And this is hard coded into the protocol.
>
> Ah yes, this is the killer.
>
> I suppose we can modify in-kernel helpers like nla_parse to deal
> with that by copying if it's unaligned. Though we'll have to
> figure out how to free the memory.
Actually we should be fine since the current netlink helpers only do
bytewise copying anyways. And I think we've pretty much gotten rid of
all the raw attribute accesses.
next prev parent reply other threads:[~2009-04-02 14:42 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-03 17:04 [Patch 4/5] Network Drop Monitor: Adding drop monitor implementation & Netlink protocol Neil Horman
2009-03-03 18:19 ` Evgeniy Polyakov
2009-03-03 19:21 ` Neil Horman
2009-03-03 22:14 ` David Miller
2009-03-03 22:16 ` David Miller
2009-03-04 10:06 ` Patrick McHardy
2009-03-04 11:00 ` David Miller
2009-04-02 9:39 ` Herbert Xu
2009-04-02 9:50 ` David Miller
2009-04-02 9:52 ` David Miller
2009-04-02 9:59 ` Herbert Xu
2009-04-02 14:42 ` Patrick McHardy [this message]
2009-04-02 14:45 ` Herbert Xu
2009-04-02 14:57 ` Patrick McHardy
2009-04-02 14:59 ` Herbert Xu
2009-04-02 15:06 ` Patrick McHardy
2009-04-02 15:09 ` Herbert Xu
2009-04-02 15:14 ` Patrick McHardy
2009-04-02 15:30 ` Herbert Xu
2009-04-05 9:59 ` David Miller
2009-04-06 13:21 ` Patrick McHardy
2009-06-10 8:08 ` David Miller
2009-06-10 10:35 ` Patrick McHardy
2009-04-05 9:57 ` David Miller
2009-04-05 9:56 ` David Miller
2009-04-05 9:54 ` David Miller
2009-03-04 11:44 ` Neil Horman
2009-03-05 19:27 ` Neil Horman
2009-03-11 16:17 ` David Miller
2009-03-11 19:51 ` Neil Horman
2009-03-13 19:10 ` David Miller
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