netdev - Re: [RFD] L2 Network namespace infrastructure

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <467D5FCD.4080003@trash.net>
Date:	Sat, 23 Jun 2007 20:00:45 +0200
From:	Patrick McHardy <kaber@...sh.net>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	netdev@...r.kernel.org, David Miller <davem@...emloft.net>,
	jamal <hadi@...erus.ca>,
	Stephen Hemminger <shemminger@...ux-foundation.org>,
	Ben Greear <greearb@...delatech.com>,
	Jeff Garzik <jeff@...zik.org>,
	YOSHIFUJI Hideaki <yoshfuji@...ux-ipv6.org>,
	Linux Containers <containers@...ts.osdl.org>
Subject: Re: [RFD] L2 Network namespace infrastructure

Eric W. Biederman wrote:
> Patrick McHardy <kaber@...sh.net> writes:
> 
>>I believe OpenVZ stores the current namespace somewhere global,
>>which avoids passing the namespace around. Couldn't you do this
>>as well?
> 
> 
> It sucks.  Especially in the corner cases.   Think macvlan
> with the real network device in one namespace and the ``vlan''
> device in another device.
> 
> The implementation of a global is also pretty a little questionable.
> Last I looked it didn't work on the transmit path at all and
> interesting on the receive path.
> 
> Further and fundamentally all a global achieves is removing the need
> for the noise patches where you pass the pointer into the various
> functions.  For long term maintenance it doesn't help anything.
> 
> All of the other changes such as messing with the
> initialization/cleanup and changing access to access the per network
> namespace data structure, and modifying the code partly along the way
> to reject working in other non-default network namespaces that are
> truly intrusive we both still have to make.
> 
> So except as an implementation detail how we pass the per network
> namespace pointer is uninteresting.
> 
> Currently I am trying for the least clever most straight forward
> implementation I can find, that doesn't give us a regression 
> in network stack performance.
> 
> So yes if we want to do passing through a magic per cpu global on
> the packet receive path now is the time to decide to do that.
> Currently I don't see the advantage in doing that so I'm not
> suggesting it.


I think your approach is fine and is probably a lot easier
to review than using something global.

>>>Depending upon the data structure it will either be modified to hold
>>>a per entry network namespace pointer or it there will be a separate
>>>copy per network namespace.  For large global data structures like
>>>the ipv4 routing cache hash table adding an additional pointer to the
>>>entries appears the more reasonable solution.
>>
>>
>>So the routing cache is shared between all namespaces?
> 
> 
> Yes.  Each namespaces has it's own view so semantically it's not
> shared.  But the initial fan out of the hash table 2M or something
> isn't something we want to replicate on a per namespace basis even
> assuming the huge page allocations could happen.
> 
> So we just tag the entries and add the network namespace as one more
> part of the key when doing hash table look ups.


I can wait for the patches, but I would be interested in how
GC is performed and whether limits can be configured per
namespace.
-
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html