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From: David Miller <davem@davemloft.net>
To: eric.dumazet@gmail.com
Cc: subramanian.vijay@gmail.com, dave.taht@gmail.com,
	hans.schillstrom@ericsson.com, netdev@vger.kernel.org,
	ncardwell@google.com, therbert@google.com, brouer@redhat.com
Subject: Re: [PATCH v2 net-next] tcp: avoid tx starvation by SYNACK packets
Date: Mon, 25 Jun 2012 21:55:37 -0700 (PDT)	[thread overview]
Message-ID: <20120625.215537.169465424900682764.davem@davemloft.net> (raw)
In-Reply-To: <1340686296.10893.115.camel@edumazet-glaptop>

From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Tue, 26 Jun 2012 06:51:36 +0200

> On Mon, 2012-06-25 at 15:43 -0700, David Miller wrote:
> 
>> I don't agree with this change.
>> 
>> What is the point in having real classification configuration if
>> arbitrary places in the network stack are going to override SKB
>> priority with a fixed priority setting?
>> 
>> I bet the person who set listening socket priority really meant it and
>> does not expect you to override it.
> 
> 
> If I add a test on listener_sk->sk_priority being 0, would you accept
> the patch ? If classification is done after tcp stack, it wont be hurt
> by initial skb priority ?

It's better than your original patch, but it suffers from the same
fundamental problem.

No user is going to expect that TCP on it's own has choosen a
non-default priority and only for some packet types.  It's completely
unexpected behavior.

A SYN flood consumes so much more RX work than the TX for the SYNACK's
ever can.

So whilst I understand your desire to handle all elements of this kind
of attack, this one is reaching too far.

  reply	other threads:[~2012-06-26  4:55 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-05-31 21:56 [PATCH net-next] tcp: avoid tx starvation by SYNACK packets Eric Dumazet
2012-05-31 23:03 ` David Miller
2012-06-01  4:48   ` Eric Dumazet
2012-06-01 17:46     ` David Miller
2012-06-01  7:00 ` [PATCH] tcp: do not create inetpeer on SYNACK message Eric Dumazet
2012-06-01 18:24   ` David Miller
2012-06-01 21:34   ` Hans Schillström
2012-06-02  6:56     ` Eric Dumazet
2012-06-01  7:36 ` [PATCH net-next] tcp: avoid tx starvation by SYNACK packets Hans Schillstrom
2012-06-01  9:34   ` Eric Dumazet
2012-06-02  1:28 ` Dave Taht
2012-06-02  5:46   ` Eric Dumazet
2012-06-23  7:34     ` Vijay Subramanian
2012-06-23  8:42       ` [PATCH v2 " Eric Dumazet
2012-06-25  6:24         ` Hans Schillstrom
2012-06-25 22:43         ` David Miller
2012-06-26  4:51           ` Eric Dumazet
2012-06-26  4:55             ` David Miller [this message]
2012-06-26  5:34               ` Hans Schillstrom
2012-06-26  7:11                 ` David Miller
2012-06-26  7:27                   ` Hans Schillstrom
2012-06-26 17:02                 ` Eric Dumazet
2012-06-27  5:23                   ` Hans Schillstrom
2012-06-27  8:22                     ` David Miller
2012-06-27  8:25                       ` Jesper Dangaard Brouer
2012-06-27  8:30                       ` Hans Schillstrom
2012-06-27  8:40                       ` Eric Dumazet
2012-06-27  8:48                         ` David Miller
2012-06-27  6:32                   ` Jesper Dangaard Brouer
2012-06-27  6:54                     ` David Miller
2012-06-27  7:24                       ` Jesper Dangaard Brouer
2012-06-27  7:30                         ` Eric Dumazet
2012-06-27  7:54                           ` Jesper Dangaard Brouer
2012-06-27  8:02                             ` Eric Dumazet
2012-06-27  8:21                               ` Jesper Dangaard Brouer
2012-06-27  8:45                                 ` Eric Dumazet
2012-06-27  9:23                                   ` Jesper Dangaard Brouer
2012-06-27  8:13                           ` David Miller
2012-06-27 19:50                       ` Florian Westphal
2012-06-27 21:39                         ` Eric Dumazet
2012-06-27 22:23                           ` David Miller
2012-06-27 22:23                         ` David Miller

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