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Message-ID: <47158A50.90905@redhat.com>
Date: Wed, 17 Oct 2007 00:06:40 -0400
From: Hideo AOKI <haoki@...hat.com>
To: Herbert Xu <herbert@...dor.apana.org.au>
CC: Satoshi OSHIMA <satoshi.oshima.fk@...achi.com>,
David Miller <davem@...emloft.net>,
netdev <netdev@...r.kernel.org>,
Hideo AOKI <hideo.aoki.tk@...achi.com>,
Yumiko SUGITA <yumiko.sugita.yf@...achi.com>,
Andi Kleen <andi@...stfloor.org>,
Evgeniy Polyakov <johnpol@....mipt.ru>,
Stephen Hemminger <shemminger@...ux-foundation.org>,
yoshfuji@...ux-ipv6.org
Subject: Re: [PATCH 4/4] UDP memory accounting and limitation(take 5): memory
limitation
Herbert Xu wrote:
> On Fri, Oct 12, 2007 at 09:11:27PM +0900, Satoshi OSHIMA wrote:
>> +static inline int __ip_check_max_skb_pages(struct sock *sk, int size)
>> +{
>> + switch(sk->sk_protocol) {
>> + case IPPROTO_UDP:
>> + if (sk->sk_prot->sysctl_mem[0] > UDP_MIN_SKB_PAGES)
>> + if (atomic_read(sk->sk_prot->memory_allocated)+size
>> + >= sk->sk_prot->sysctl_mem[0])
>> + return -ENOBUFS;
>> + /* Fall through */
>> + default:
>> + break;
>> + }
>> + return 0;
>> +}
>
> Since you're not doing a per-user limit, you must give each
> socket a minimum even when the total exceeds your threshold.
>
> Otherwise any local user can trivially DoS the whole system.
>
>> +UDP variables:
>> +
>> +udp_mem - INTERGER
>> + Number of pages allowed for queueing by all UDP sockets.
>> + Minimal value is 4096. If 4096 is set, UDP memory will not
>> + be limited.
>> + Default: 4096
>
> This seems to be a rather confusing setup. We don't set a
> minimum for TCP so is this really necessary?
Hello Herbert,
Thank you so much for your comments.
I'm going to fix them in next take patch set.
Regards,
Hideo
--
Hitachi Computer Products (America) Inc.
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