netdev - Re: [net-next fragmentation icmp v4 3/4] bridge_netfilter: No ICMP packet on IPv4 defragmentation timeout

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Message-ID: <CACzMAJ+J3QGFZa976_M=_ZKjgEPiJszyYrqeqeGj=9rjCBZJ7A@mail.gmail.com>
Date:	Thu, 14 May 2015 12:54:23 -0700
From:	Andy Zhou <azhou@...ira.com>
To:	Florian Westphal <fw@...len.de>
Cc:	David Miller <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [net-next fragmentation icmp v4 3/4] bridge_netfilter: No ICMP
 packet on IPv4 defragmentation timeout

On Thu, May 14, 2015 at 1:59 AM, Florian Westphal <fw@...len.de> wrote:
> Andy Zhou <azhou@...ira.com> wrote:
>> Currently, on defragmentation timeout error, ICMP error message
>> will be generated. This is fine when they are used in a routing context,
>> but does not make sense in the context of bridging netfilter.
>>
>> This patch adds a bit (IPSKB_NO_FRAG_ICMP) in IPCB to control
>> whether ICMP error message should be generated. br_netfiler sets
>> this bit.
>
> Could you please explain why we need this patch?
> After the previous change (patch 2 in your series), we will already
> bail out before hitting
>
> /* Send an ICMP "Fragment Reassembly Timeout" message. */
> icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0);
>
> in ip_expire() based on qp->user value test?

Letting caller making the decision seems to be a better design choice
rather than implicit
logic embedded within the function.  It is also more flexible and
robust when we need to extend 'user'
range down the road.

>
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