On Feb 18, 2009, at Feb 18, 2009, 8:55 AM, Theodore Tso wrote:
quoted text
> On Tue, Feb 17, 2009 at 09:29:19PM -0800, David Miller wrote:
>> Next, if it's just an issue of IPV6 traffic, install a packet
>> scheduler rule that rejects all packets with ethernet proto
>> ETH_P_IPV6
>>
>> If openning up ipv6 sockets is problematic, that can be blocked
>> using the security layer, which your super-duper distro kernel
>> is guarenteed to have enabled. :-)
>>
>> I'm sure there is someone who has legacy problems with ipv4
>> and that can't be disabled, and somehow people cope.  Amazing.

Here's another "me too".

Kernel RPC support also has this problem.  We hit it just a couple of  
weeks ago now that we have IPv6 enabled NFS in prototype.  If PF_INET6  
listener creation fails (eg. because ipv6.ko is blacklisted), our  
workaround right now is to retry the listener socket creation with  
PF_INET.  There are plenty of somewhat rare corner cases that make  
this less than ideal.

quoted text
> The reality is that there are far more people who have legacy problems
> with ipv6 than ipv4 (which has been around and in active use for about
> 3 decades, after all), whereas ipv6 has been around and largely
> ignored for about a decade.  :-/
>
> I'll admit that I ran into some wierd sh*t problems with some open
> source software or another failing mysteriously when IPv6 was enabled,
> and I dealt with it by simply disabling IPv6 (yeah, I blocked the
> module).  I was in a hurry, and it just didn't work, and I had better
> thing to do than to spend time trying to debug why the presense of an
> IPv6 enabled interface caused programs to misbehave in random ways.
>
> I think I can pretty much guarantee that distro users will be
> clamoring for a quick and easy way to block ipv6, and it's in our
> interest to document the recomended way to block it that doesn't cause
> weird problems with bonding, etc.

A better solution would be to design kernel and user space networking  
to handle this use case, instead of providing a workaround.  From the  
variety of comments I've heard, this use case is pretty common.

Considering the government mandates requiring IPv6 support (and the  
advertisements by Linux vendors claiming IPv6 support), IPv6 needs to  
become a first-class citizen in Linux in fairly short order.  It still  
feels a little piecemeal to me to be called "production ready."

--
Chuck Lever
chuck[dot]lever[at]oracle[dot]com
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