netdev - Re: [RFC][PATCH] ipv6 multicast forwarding: Remove threshold checking and some trivial bugs

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Date:	Tue, 18 Dec 2012 13:19:53 +0800
From:	Ang Way Chuang <wcang@....wide.ad.jp>
To:	David Miller <davem@...emloft.net>
CC:	netdev@...r.kernel.org, yoshfuji@...ux-ipv6.org
Subject: Re: [RFC][PATCH] ipv6 multicast forwarding: Remove threshold checking
 and some trivial bugs

Oops, sorry. You're right. I am not very confident with this modification. It may break some multicast
routing daemon. Let's drop this for now.

On 18/12/2012 13:03, David Miller wrote:
> From: Ang Way Chuang <wcang@....wide.ad.jp>
> Date: Tue, 18 Dec 2012 12:57:11 +0800
> 
>> This patch fixes trivial bugs for IPv6 multicast forwarding code and remove
>> threshold checking for multicast forwarding cache.
>>
>> 1. Threshold checking in IPv6 multicast forwarding cache (MFC) was not properly implemented.
>> syscall to setsockopt(... MRT6_ADD_MIF,...) doesn't affect the TTL because it is never used.
>> In fact, all MFC will always have ttl of 1 as set by ip6mr_mfc_add. From my limited knowledge of
>> multicast routing, threshold setting on interface is only used by DVMRP which doesn't support
>> IPv6. FreeBSD's struct mif6ctl doesn't have vifc_threshold. This patch removes the ttl cruft
>> within kernel. Userspace ABI for backward compatibility. Can someone knowledgable in multicast
>> routing please verify whether my understanding is correct?
>> 2. Don't allow addition of MFC with non-existent multicast interface index.
>> 3. Don't allow addition of MFC where incoming interface is part of oif list. This does not make
>>    sense. Why would we want to send a multicast back to the interface where it originates from.
>> 4. setsockopt(....MRT6_ADD_MIF, ) allows a "physical" interface to be registered as multicast 
>>    interface multiple times. This doesn't make sense. Don't allow registration duplicate 
>>    registration of the same "physical" interface. 
>>
>> This patch has been tested, albeit minimally using a simple program. Is this patch okay for
>> inclusion? Will sign off if it is okay.
> 
> How about we don't mix together a set of bug fixes, with a semantic
> change (the removal of the threshold checking)?
> 
> I also don't see what the point is of not signing off on this change
> when you submit it.
> 
> If you delay the signoff until after review, you're just causing it to
> take longer to have your changes integrated.  It also makes it look
> like you didn't believe fully in your change, so you probably should
> have sent it as an RFC and listed your doubts in the email instead.
> 
> Overall I would rate this as an extremely poor patch submission,
> sorry.
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