jamal <hadi@cyberus.ca> writes:

> On Fri, 2006-27-10 at 11:10 +0200, Daniel Lezcano wrote:
>
>> No, it uses virtualization at layer 2 and I had already mention it 
>> before (see the first email of the thread), but thank you for the email 
>> thread pointer.
>
>
> What would be really useful is someone takes the time and creates a
> matrix of the differences between the implementations.
> It seems there are quiet a few differences but without such comparison
> (to which all agree to) it is hard to form an opinion without a document
> of some form.
>  
> For one, I am puzzled by the arguements about L2 vs L3 - Is this the
> host side or inside the VE?
>
> If it is a discussion of the host side:
> To me it seems it involves the classification of some packet header
> arriving on a physical netdevice on the host side (irrelevant whether
> they are L2 or L7) and reaching a decision to select some redirected to
> virtual netdevice.

There are two techniques in real use.
- Bind/Accept filtering 

  Which layer 3 addresses a socket can bind/accept are filtered, but otherwise
  the network stack remains unchanged.  When your container/VE only has
  a single IP address this works great.  When you get multiple IPs
  this technique starts to fall down because it is not obvious how to
  make this correctly handle wild card ip addresses.  This technique
  also falls down because it is very hard to support raw IP packets.

  The major advantage of this approach is that it is insanely simple
  and cheap.  

  When the discussion started this is what I called Layer 3, bind
  filtering is probably a more precise name.

- Network object tagging

  Every network device, each socket, each routing table, each net
  filter table, everything but the packets themselves is associated
  with a single VE/container.  In principle the network stack doesn't
  change except everything that currently access global variables gets
  an additional pointer indirection.

  To find where a packet is you must look at it's network device on
  ingress, and you must look at it's socket on egress.

  This allows capabilities like CAP_NET_ADMIN to be fairly safely
  given to people inside a container without problems.

  There are two basic concerns here. 
  1) This is a lot of code that needs to be touched.
  2) There are not enough physical network devices to go around so
     we need something that maps packets coming in a physical network
     device into multiple virtual network devices.

     The obvious way to do this mapping is with either ethernet
     bridging or with the linux routing code if the external network
     is not ethernet, and some tunnel devices between the VE and the
     host environment.  This allows firewalling and in general the
     full power of the linux network stack.

     The concern is that the extra trip through the network stack adds
     overhead.

  This is the technique we have been calling layer two because it
  works below the IP layer and as such should work for everything.

There have been some intermediate solutions considered but generally
the have the down sides of additional expense without the upsides of
more power.

> The admin (on the host) decides what packets any VE can see. 
> Once within the VE, standard Linux net stack applies. The same applies
> on the egress. The admin decides what packets emanating from the VE
> go where.
> I dont think this is a simple L2 vs L3. You need to be able to process
> IP as well as Decnet[1]

Except for some implementation details I don't think we have
disagreement about what we are talking about although there is
certainly a little confusion.  The true issue is can we implement
something that places the full power of the network stack (including
things like creating virtual tunnel devices) into the container/VE
without sacrificing performance.

I think we could all agree on the most general technique if we could
convince ourselves the overhead was unmeasurable.

Given that performance is the primary concern this is something a
network stack expert might be able to help with.  My gut feel is
the extra pointer indirection for the more general technique is
negligible and will not affect the network performance.  The network
stack can be very sensitive to additional cache misses so I could be
wrong.  Opinions?

Then the question is how do we reduce the overhead when we don't have
enough physical network interfaces to go around.  My feeling is that
we could push the work to the network adapters and allow single
physical network adapters to support multiple network interfaces, each
with a different link-layer address.  At which point the overhead is
nearly nothing and newer network adapters may start implementing
enough filtering in hardware to do all of the work for us.

> [1] Since Linux has the only SMP-capable, firewall-capable Decnet
> implementation - wouldnt it be fun to have it be virtualized as
> well? ;->

Yes.  The only problem I have seen with Decnet is the pain of teaching
it that it's variables aren't global anymore.  Not a show stopper but
something that keeps Decnet out of existing proof of concept
implications.

Eric

p.s. Sorry for the long delayed reply.  I have had my head down
stabilizing 2.6.19 and netdev is not a list I regularly watch.

p.p.s.  I have CC'd the containers list so we catch all of the
relevant people on the discussion.  I believe this is an open
list so shouldn't cause any problems.

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Daniel Lezcano <dlezcano@fr.ibm.com> writes:

>> Then a matrix of how each requires what modifications in the network
>> code. Of course all players need to agree that the description is
>> accurate.
>> Is there such a document?
>> cheers,
>> jamal
>
> Hi,
>
> the attached document describes the network isolation at the layer 2 and at the
> layer 3, it presents the pros and cons of the different approaches, their common
> points and the impacted network code.
> I hope it will be helpful :)

Roughly it is correctly but I the tradeoffs you describe are incorrect.


> Isolating and virtualizing the network
> --------------------------------------
>
> Some definitions:
> -----------------
>
> isolation : This is a restrictive technique which divides a set of the
> available system objects to smaller subsets assigned to a group of
> processes. This technique ensures an application will use only a
> subset of the system resources and will never access other
> resources.
>
> virtualization : This technique gives the illusion to an application
> that its owns all the system resources instead of a subset of them
> provided by the isolation.
>
> container: it is the name of the base element which brings the
> isolation and the virtualization where applications are running into.
>
> system container: operating system running inside a container.
>
> application container : application running inside a container.
>
> checkpoint/restart: take a snapshot of a container at a given time
> and recreate the container from this snapshot.
>
> mobility: checkpoint/restart used to move a container to one host to
> another host.
>
> ----------------------------
>
> Actually, containers are being developed in the kernel with the
> following functions :
>
> 	  * separate the system resources between containers in order
>             to avoid an application, running into a container, to
>             access the resources outside the container. That
>             facilitates the resources management, ensures the
>             application is jailed and increases the security.
>
> 	  * virtualize the resources, that avoids resources conflict
>             between containers, that allows to run several instance of
>             the same servers without modifying its network
>             configuration.
>
> 	  * the combination of the isolation and the virtualization is
>             the base for the checkpoint/restart. The checkpoint is
>             easier because the resources are identified by container
>             and the restart is possible because the applications can
>             be recreated with the same resources identifier without
>             conflicts. For example, the application has the pid 1000,
>             it is checkpointed and when it is restarted the same pid
>             is assigned to it and it will not conflict because pids are
>             isolated and virtualized.
>
> In all the system resources, the network is one of the biggest part
> to isolate and virtualize. Some solutions were proposed, with
> different approaches and different implementations.
>
> Layer 2 isolation and virtualization
> ------------------------------------

Guys this is probably where we need to focus and not look at the
other options until we find insurmountable challenges with this.
We can make it do everything everyone needs.

> The virtualization acts at the network device level. The routes and
> the sockets are isolated. Each container has its own network device
> and its own routes. The network must be configured in each container.
>
> This approach brings a very strong isolation and a perfect
> virtualization for the system containers.
>
>
>  - Ingress traffic
>
> The packets arrive to the real network device, outside of the
> container. Depending on the destination, the packets are forwarded to
> the network device assigned to the container. From this point, the
> path is the same and the packets go through the routes and the sockets
> layer because they are isolated into the container.


You don't need the extra hop.  The extra hop is only there because there
are not enough physical interfaces on a machine.  Plus I think with a little
work this one particular case can be optimized to the point where it
is not significant.

>  - Outgoing traffic
>
> The packets go through the sockets, the routes, the network device
> assigned to the container and finally to the real device.
>
>
> Implementation:
> ---------------
>
> Andrey Savochkin, from OpenVZ team, patchset of this approach uses the
> namespace concept.  All the network devices are no longer stored into
> the "dev_base_list" but into a list stored into the network namespace
> structure. Each container has its own network namespace. The network
> device access has been changed to access the network device list
> relative to the current namespace's context instead of the global
> network device list. The same has been made for the routing tables,
> they are all relatives to the namespace and are no longer global
> static. The creation of a new network namespace implies the creation
> of a new set of routing table.
>
> After the creation of a container, no network device exists. It is
> created from outside by the container's parent. The communication
> between the new container and the outside is done via a special pair
> device which have each extremities into each namespace. The MAC
> addresses must be specified and these addresses should be handled by
> the containers developers in order to ensure MAC unicity.
>
> After this network device creation step into each namespace, the
> network configuration is done as usual, in other words, with a new
> operating system initialization or with the 'ifconfig' or 'ip'
> command.
>
>   -----     ------     -------             ------     ----
>  | LAN |<->| eth0 |<->| veth0 |<-|ns(1)|->| eth0 |<->| IP |
>   -----     ------     -------             ------     ----

Note.  veth is only necessary because there are enough physical
network interfaces to go around.

> (1) : ns = namespace (aka. Virtual Environment).
>
> The advantages of this implementation is the algorithms used by the
> network stack are not touched, only the network data access is
> modified. That's facilitate the maintenance and the evolution of the
> network code. The drawback is in the case of application container,
> the number of containers can be much more important, (hundred of
> them), that implies a number of network devices more important, a
> longer path to go through the virtualization layer and a more
> resources consumption. 


>
> Layer 3 isolation and virtualization
> ------------------------------------
>
> The virtualization acts at the IP level. The routes can be isolated
> and the sockets are isolated.
>
> This approach does not bring isolation at the network device
> layer. The isolation and the virtualization is less stronger than the
> layer 2 but it presents a negligible overhead and resource
> consumption near from the non virtualized environment. Furthermore,
> the isolation at the IP level makes the administration very easy.

All administration issues I have seen can be fixed with good tools
and doing things the way the rest of linux does them.  Currently
you do things differently.

>  - Ingress traffic
>
> The packets arrive to the real device and go through the routes
> engine. From this point, the used route is enough to know to which
> container the traffic can go and the sockets subset assigned to the
> container.

Note this has potentially the highest overhead of them all because
this is the only approach in which it is mandatory to inspect the
network packets to see which container they are in.

My real problem with this approach besides seriously complicating
the administration by not delegating it is that you loose enormous
amounts of power.  

>  - Outgoing traffic:
>
> The packets go through the sockets, the assigned routes and finally to
> the real device.
>
> The socket are isolated for each container, the current container
> context is used to retrieve the IP address owned by the
> container. When the source address is not specified, the owned IP is
> used to fill the source address of the packet. This is done when doing
> raw, icmp, multicast, broadcast, tcp connection and udp send
> message. If the bind is done on the interface instead of a ip address,
> the source address should be checked to be owned by the container too.
>
>
> Implementation:
> ---------------
>
> Concerning the implementation, several solutions exist. All of them
> rely to the namespace concept but instead of having all the network
> resources relative to the namespace, the namespace pointer is used as
> an identifier.
>
> One of these solutions is the bind filtering. This implementation is
> the simplest to realize but it brings little isolation. If a mobility
> solution must be implemented on the top of that isolation, the bind
> filtering should be coupled with the socket isolation. The bind
> filtering consists in placing several hooks at some strategic points
> into function calls (bind, connect, send datagram, etc ...) in order
> to fill source address and avoid the bind to an IP address outside of
> the container. The container destination should be determined from the
> ingress traffic.
>
> The second solution consists in relying on the route engi

> -----Original Message-----
> From: netdev-owner@vger.kernel.org 
> [mailto:netdev-owner@vger.kernel.org] On Behalf Of Eric W. Biederman

> Then the question is how do we reduce the overhead when we 
> don't have enough physical network interfaces to go around.  
> My feeling is that we could push the work to the network 
> adapters and allow single physical network adapters to 
> support multiple network interfaces, each with a different 
> link-layer address.  At which point the overhead is nearly 
> nothing and newer network adapters may start implementing 
> enough filtering in hardware to do all of the work for us.

Correct, to a degree. 
There will be always a limit on the number of physical "channels" that a
NIC 
can support, while keeping these channels fully independent and
protected at the hw level.
So, you will probably still need to implement the sw path, 
with the assumption that some containers (that care about performance)
will get a separate 
NIC interface and avoid the overhead, and other containers will have to
use the sw path. 
There are some multi-channel NICs shipping today so it would be possible
to see the overhead between the two options (I suspect it will be quite
noticeable), but for a general idea about what work could be pushed down
to network adapters in the near future you can look at the pcisig.com
I/O Virtualization Workgroup. 
Once the single root I/O Virtualization spec is completed, it is likely
to be supported by several NIC vendors to provide multiple network
interfaces on a single NIC that you are looking for.


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"Leonid Grossman" <Leonid.Grossman@neterion.com> writes:

>  
>
>> -----Original Message-----
>> From: netdev-owner@vger.kernel.org 
>> [mailto:netdev-owner@vger.kernel.org] On Behalf Of Eric W. Biederman
>
>> Then the question is how do we reduce the overhead when we 
>> don't have enough physical network interfaces to go around.  
>> My feeling is that we could push the work to the network 
>> adapters and allow single physical network adapters to 
>> support multiple network interfaces, each with a different 
>> link-layer address.  At which point the overhead is nearly 
>> nothing and newer network adapters may start implementing 
>> enough filtering in hardware to do all of the work for us.
>
> Correct, to a degree. 
> There will be always a limit on the number of physical "channels" that a
> NIC 
> can support, while keeping these channels fully independent and
> protected at the hw level.
> So, you will probably still need to implement the sw path, 
> with the assumption that some containers (that care about performance)
> will get a separate 
> NIC interface and avoid the overhead, and other containers will have to
> use the sw path. 
> There are some multi-channel NICs shipping today so it would be possible
> to see the overhead between the two options (I suspect it will be quite
> noticeable), but for a general idea about what work could be pushed down
> to network adapters in the near future you can look at the pcisig.com
> I/O Virtualization Workgroup. 
> Once the single root I/O Virtualization spec is completed, it is likely
> to be supported by several NIC vendors to provide multiple network
> interfaces on a single NIC that you are looking for.

Pushing it all of the way into the hardware is an optimization, that while
great is likely not necessary.  Simply doing a table lookup by
link-level address and selecting between several network interfaces
is enough to ensure we only traverse the network stack once.

To keep overhead down in the container case I don't need the hardware
support to be so good you can do kernel bypass and still trust that
everything is safe.  I simply a fast link-level address to container
mapping.  We already look at the link-level address on every packet
received so that should not generate any extra cache misses.

In the worst case I might need someone to go as far as the Grand
Unified Lookup to remove all of the overheads.  Except for
distributing the work load more evenly across the machine with
separate interrupts and the like I see no need for separate hardware
channels to make things go fast for my needs.

Despite the title of this thread there is no virtualization or
emulation of the hardware involved.  Just enhancements to the existing
hardware abstractions.

Eric
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"Leonid Grossman" <Leonid.Grossman@neterion.com> writes:

> I did not mean kernel bypass, just L2 hw channels that for 
> all practical purposes act as separate NICs - 
> different MAC addresses, no blocking, independent reset, etc.

Yes. Nearly all of what you need for safe kernel bypass.

>> In the worst case I might need someone to go as far as the 
>> Grand Unified Lookup to remove all of the overheads.  Except 
>> for distributing the work load more evenly across the machine 
>> with separate interrupts and the like I see no need for 
>> separate hardware channels to make things go fast for my needs.
>> 
>> Despite the title of this thread there is no virtualization 
>> or emulation of the hardware involved.  Just enhancements to 
>> the existing hardware abstractions.
>
> Right, I was just trying to say that IOV support (likely, from multiple
> vendors since
> virtualization is expected to be widely used) would provide an option to
> export multiple
> independent L2 interfaces from a single NIC - even if only a subset of 
> IOV functionality would be used in this case.

Agreed, and I think I understood that.  My basic point was that it
doesn't look to me like I need the hardware support, just that I can
use it when it is there.

The core advantage I see of the multiple queues, is in being able to
split the processing of network traffic and interrupts among multiple
cores.

Eric
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> -----Original Message-----
> From: Eric W. Biederman [mailto:ebiederm@xmission.com] 
> Sent: Saturday, November 25, 2006 11:27 AM
> To: Leonid Grossman
> Cc: hadi@cyberus.ca; Daniel Lezcano; Dmitry Mishin; Stephen 
> Hemminger; netdev@vger.kernel.org; Linux Containers
> Subject: Re: Network virtualization/isolation
> 
> "Leonid Grossman" <Leonid.Grossman@neterion.com> writes:
> 
> >  
> >
> >> -----Original Message-----
> >> From: netdev-owner@vger.kernel.org
> >> [mailto:netdev-owner@vger.kernel.org] On Behalf Of Eric W. 
> Biederman
> >
> >> Then the question is how do we reduce the overhead when we 
> don't have 
> >> enough physical network interfaces to go around.
> >> My feeling is that we could push the work to the network 
> adapters and 
> >> allow single physical network adapters to support multiple network 
> >> interfaces, each with a different link-layer address.  At 
> which point 
> >> the overhead is nearly nothing and newer network adapters 
> may start 
> >> implementing enough filtering in hardware to do all of the 
> work for 
> >> us.
> >
> > Correct, to a degree. 
> > There will be always a limit on the number of physical 
> "channels" that 
> > a NIC can support, while keeping these channels fully 
> independent and 
> > protected at the hw level.
> > So, you will probably still need to implement the sw path, with the 
> > assumption that some containers (that care about 
> performance) will get 
> > a separate NIC interface and avoid the overhead, and other 
> containers 
> > will have to use the sw path.
> > There are some multi-channel NICs shipping today so it would be 
> > possible to see the overhead between the two options (I suspect it 
> > will be quite noticeable), but for a general idea about what work 
> > could be pushed down to network adapters in the near future you can 
> > look at the pcisig.com I/O Virtualization Workgroup.
> > Once the single root I/O Virtualization spec is completed, it is 
> > likely to be supported by several NIC vendors to provide multiple 
> > network interfaces on a single NIC that you are looking for.
> 
> Pushing it all of the way into the hardware is an 
> optimization, that while great is likely not necessary.  
> Simply doing a table lookup by link-level address and 
> selecting between several network interfaces is enough to 
> ensure we only traverse the network stack once.
> 
> To keep overhead down in the container case I don't need the 
> hardware support to be so good you can do kernel bypass and 
> still trust that everything is safe.  I simply a fast 
> link-level address to container mapping.  We already look at 
> the link-level address on every packet received so that 
> should not generate any extra cache misses.

I did not mean kernel bypass, just L2 hw channels that for 
all practical purposes act as separate NICs - 
different MAC addresses, no blocking, independent reset, etc.

> 
> In the worst case I might need someone to go as far as the 
> Grand Unified Lookup to remove all of the overheads.  Except 
> for distributing the work load more evenly across the machine 
> with separate interrupts and the like I see no need for 
> separate hardware channels to make things go fast for my needs.
> 
> Despite the title of this thread there is no virtualization 
> or emulation of the hardware involved.  Just enhancements to 
> the existing hardware abstractions.

Right, I was just trying to say that IOV support (likely, from multiple
vendors since
virtualization is expected to be widely used) would provide an option to
export multiple
independent L2 interfaces from a single NIC - even if only a subset of 
IOV functionality would be used in this case.

> 
> Eric
> 


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Herbert Poetzl wrote:
> On Sat, Nov 25, 2006 at 01:21:39AM -0700, Eric W. Biederman wrote:
>   
> Then the question is how do we reduce the overhead when we don't have
>> enough physical network interfaces to go around.  My feeling is that
>> we could push the work to the network adapters and allow single
>> physical network adapters to support multiple network interfaces, each
>> with a different link-layer address.  
>>     
>
> that would be something interesting, but again, the
> number of nics allowing for an arbitrary number of
> filters, which also can be identified/correlated to
> the network context without adding even more overhead
> is probably insignificant ... so IMHO that would:
>
>  - keep all interfaces in promisc mode
>  - check each packet for the set of MACs
>
> as the checks would require to identify the interface,
> that would immediately result in O(N) overhead for
> each packet received, plus the overhead added by
> disabling the hardware filters ... but maybe that
> changed over the years, I'm definitely no network
> stack/device expert ...
>   
This can be implemented similar to how MAC-VLANs are currently done (in 
my out-of-tree patch).
There is a performance hit with lots of virtual interfaces (maybe 10% in 
some cases), but this is still
greater than 500Mbps full-duplex on 2 ports on a modern dual-core machine.

I don't even have hashing implemented, but it could be easily added and 
that should
significantly decrease the search time from O(n) to something 
approaching O(1)
in the normal case.

This should also be an easy feature for NICs to add, and just as with 
802.1Q VLANs, when
hardware support is available, the features can migrate into the NIC, 
with the software
mac-vlan logic handling generic hardware.

In a switched environment, going into PROMISC mode should not add any
significant overhead..

Ben

-- 
Ben Greear <greearb@candelatech.com> 
Candela Technologies Inc  http://www.candelatech.com


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Herbert Poetzl <herbert@13thfloor.at> writes:

> On Sat, Nov 25, 2006 at 01:21:39AM -0700, Eric W. Biederman wrote:

>> There are two techniques in real use.
>> - Bind/Accept filtering 
>> 
>>   Which layer 3 addresses a socket can bind/accept are filtered,
>>   but otherwise the network stack remains unchanged. When your
>>   container/VE only has a single IP address this works great. 
>
>>   When you get multiple IPs this technique starts to fall down because
>>   it is not obvious how to make this correctly handle wild card ip
>>   addresses. 
>
> not really, you have to check for a (sub)set of IPs
> that's quite simple and not hard to get right, I agree
> that it increases the overhead on those checks, but 
> this only occurs at bind/connect/accept time ...

The general problem is you get into mental model problems.  You think
you are isolated but you don't realize you can route packets over the
loopback interface for example.  But with care yes you can solve it.

However while I think there is value in this technique it doesn't
solve any of my problems, nor do I think it can be easily stretched
to solve my problems.  My gut feel for implementation still says
this should be a new netfilter table that filters binds and accepts
if we implement this.

For most of us we need more power than we can get with the simple
bind/accept filtering so we I think the network namespace work should
concentrate on the general technique that gives us the entire power of
the current network stack.  At least until we have proved the
overheads are unacceptable.

>> Given that performance is the primary concern this is something a
>> network stack expert might be able to help with.  My gut feel is
>> the extra pointer indirection for the more general technique is
>> negligible and will not affect the network performance.  The network
>> stack can be very sensitive to additional cache misses so I could be
>> wrong.  Opinions?
>
> well, here we are talking about layer2 _isolation_
> if I got that right, i.e. you split the physical
> interfaces up into separate network namespaces, which
> then can make full use of the assigned interfaces

Yes.  Layer 2 isolation is a good description.

> this is something which I'm perfectly fine with, as
> I do not think it adds significant overhead (nevertheless
> it needs some testing) 
Yes lots of testing and careful implementation.

> but at the same time, this is
> something which isn't very useful in the generic case,
> where folks will have, let's say two network interfaces
> and want to share one of them between 100 guests ...

It is useful in the generic case.  It just requires being smart to
keep the overheads down.

> as the checks would require to identify the interface,
> that would immediately result in O(N) overhead for
> each packet received, plus the overhead added by
> disabling the hardware filters ... but maybe that
> changed over the years, I'm definitely no network
> stack/device expert ...

Getting this to O(log(N)) is easy, and you can probably
get the average case to O(1) without trying too hard.  This
is no worse than routing tables or multiple IP addresses on
a single interface.  Ben Greear has addressed this.  His experience
suggest that even O(N) is not likely to be a significant problem.


Now I'm going to go bury my head in the sand for a bit.  The hard
problems are not how do we reshape the network stack but how do we
get the appropriate context into all of our user space interfaces.

Eric
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On Sat, Nov 25, 2006 at 01:21:39AM -0700, Eric W. Biederman wrote:
> 
> jamal <hadi@cyberus.ca> writes:
> 
> > On Fri, 2006-27-10 at 11:10 +0200, Daniel Lezcano wrote:
> >
> >> No, it uses virtualization at layer 2 and I had already mention it 
> >> before (see the first email of the thread), but thank you for the email 
> >> thread pointer.
> >
> >
> > What would be really useful is someone takes the time and creates a
> > matrix of the differences between the implementations.
> > It seems there are quiet a few differences but without such comparison
> > (to which all agree to) it is hard to form an opinion without a document
> > of some form.
> >  
> > For one, I am puzzled by the arguements about L2 vs L3 - Is this the
> > host side or inside the VE?
> >
> > If it is a discussion of the host side:
> > To me it seems it involves the classification of some packet header
> > arriving on a physical netdevice on the host side (irrelevant whether
> > they are L2 or L7) and reaching a decision to select some redirected to
> > virtual netdevice.
> 
> There are two techniques in real use.
> - Bind/Accept filtering 
> 
>   Which layer 3 addresses a socket can bind/accept are filtered,
>   but otherwise the network stack remains unchanged. When your
>   container/VE only has a single IP address this works great. 

>   When you get multiple IPs this technique starts to fall down because
>   it is not obvious how to make this correctly handle wild card ip
>   addresses. 

not really, you have to check for a (sub)set of IPs
that's quite simple and not hard to get right, I agree
that it increases the overhead on those checks, but 
this only occurs at bind/connect/accept time ...

>   This technique also falls down because it is very hard to
>   support raw IP packets.

raw ip packets could be header checked in the same way
but in general, this type of isolation does not make
too much sense for raw ip purposes ...

>   The major advantage of this approach is that it is insanely simple
>   and cheap.  

and don't forget flexible, because it also alows a few
things not quite easily done with layer2 techniques
(see below)

>   When the discussion started this is what I called Layer 3, bind
>   filtering is probably a more precise name.
> 
> - Network object tagging
> 
>   Every network device, each socket, each routing table, each net
>   filter table, everything but the packets themselves is associated
>   with a single VE/container.  In principle the network stack doesn't
>   change except everything that currently access global variables gets
>   an additional pointer indirection.
> 
>   To find where a packet is you must look at it's network device on
>   ingress, and you must look at it's socket on egress.
> 
>   This allows capabilities like CAP_NET_ADMIN to be fairly safely
>   given to people inside a container without problems.
> 
>   There are two basic concerns here. 
>   1) This is a lot of code that needs to be touched.
>   2) There are not enough physical network devices to go around so
>      we need something that maps packets coming in a physical network
>      device into multiple virtual network devices.
> 
>      The obvious way to do this mapping is with either ethernet
>      bridging or with the linux routing code if the external network
>      is not ethernet, and some tunnel devices between the VE and the
>      host environment.  This allows firewalling and in general the
>      full power of the linux network stack.
> 
>      The concern is that the extra trip through the network stack adds
>      overhead.
> 
>   This is the technique we have been calling layer two because it
>   works below the IP layer and as such should work for everything.
> 
> There have been some intermediate solutions considered but generally
> the have the down sides of additional expense without the upsides of
> more power.
> 
> > The admin (on the host) decides what packets any VE can see. 
> > Once within the VE, standard Linux net stack applies. The same applies
> > on the egress. The admin decides what packets emanating from the VE
> > go where.
> > I dont think this is a simple L2 vs L3. You need to be able to process
> > IP as well as Decnet[1]
> 
> Except for some implementation details I don't think we have
> disagreement about what we are talking about although there is
> certainly a little confusion.  The true issue is can we implement
> something that places the full power of the network stack (including
> things like creating virtual tunnel devices) into the container/VE
> without sacrificing performance.
> 
> I think we could all agree on the most general technique if we could
> convince ourselves the overhead was unmeasurable.

and we do not give away features like:

 - sharing an IP between different guests, so that
   services can bind to the same IP as long as they
   do not collide

 - allow simple wrapping (ala chroot()) for processes
   without requiring a complete routing/network setup
   plus a virtual switch/router/whatever

> Given that performance is the primary concern this is something a
> network stack expert might be able to help with.  My gut feel is
> the extra pointer indirection for the more general technique is
> negligible and will not affect the network performance.  The network
> stack can be very sensitive to additional cache misses so I could be
> wrong.  Opinions?

well, here we are talking about layer2 _isolation_
if I got that right, i.e. you split the physical
interfaces up into separate network namespaces, which
then can make full use of the assigned interfaces

this is something which I'm perfectly fine with, as
I do not think it adds significant overhead (nevertheless
it needs some testing) but at the same time, this is
something which isn't very useful in the generic case,
where folks will have, let's say two network interfaces
and want to share one of them between 100 guests ...

> Then the question is how do we reduce the overhead when we don't have
> enough physical network interfaces to go around.  My feeling is that
> we could push the work to the network adapters and allow single
> physical network adapters to support multiple network interfaces, each
> with a different link-layer address.  

that would be something interesting, but again, the
number of nics allowing for an arbitrary number of
filters, which also can be identified/correlated to
the network context without adding even more overhead
is probably insignificant ... so IMHO that would:

 - keep all interfaces in promisc mode
 - check each packet for the set of MACs

as the checks would require to identify the interface,
that would immediately result in O(N) overhead for
each packet received, plus the overhead added by
disabling the hardware filters ... but maybe that
changed over the years, I'm definitely no network
stack/device expert ...

> At which point the overhead is nearly nothing and newer network
> adapters may start implementing enough filtering in hardware to do all
> of the work for us.

well, might be a solution in 4-5 years, when basically
any computer system uses such nics ...

> > [1] Since Linux has the only SMP-capable, firewall-capable Decnet
> > implementation - wouldnt it be fun to have it be virtualized as
> > well? ;->
> 
> Yes. The only problem I have seen with Decnet is the pain of teaching
> it that it's variables aren't global anymore. Not a show stopper
> but something that keeps Decnet out of existing proof of concept
> implications.
> 
> Eric
> 
> p.s. Sorry for the long delayed reply.  I have had my head down
> stabilizing 2.6.19 and netdev is not a list I regularly watch.
> 
> p.p.s.  I have CC'd the containers list so we catch all of the
> relevant people on the discussion.  I believe this is an open
> list so shouldn't cause any problems.

thanks a lot!

best,
Herbert

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I do not want to get into a big debate on the merits of various
techniques at this time.  We seem to be in basic agreement
about what we are talking about.

There is one thing I think we can all agree upon.
- Everything except isolation at the network device/L2 layer, does not
  allow guests to have the full power of the linux networking stack.

- There has been a demonstrated use for the full power of the linux
  networking stack in containers..

- There are a set of techniques which look as though they will give
  us full speed when we do isolation of the network stack at the
  network device/L2 layer.

Is there any reason why we don't want to implement network namespaces
without the full power of the linux network stack?

If there is a case where we clearly don't want the full power of the
linux network stack in a guest but we still need a namespace we can
start looking at the merits of the alternatives.

> What is this new paradigm you are talking about ?

The basic point is this.  The less like stock linux the inside of a
container looks, and the more of a special case it is the more
confusing it is.  The classic example is that for a system container
routing packets between containers over the loopback interface is
completely unexpected.


> There is not extra networking data structure instantiation in the
> Daniel's L3.
Nope just an extra field which serves the same purpose.

>> - Bind/Connect/Accept filtering.  There are so few places in
>>   the code this is easy to maintain without sharing code with
>>   everyone else.
>
> For isolation too ? Can we build network migration on top of that ?

As long as you can take your globally visible network address with you
when you migrate you can build network migration on top of it.  So yes
bind/accept filtering is sufficient to implement migration, if you are
only using IP based protocols.

Eric
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Daniel Lezcano <dlezcano@fr.ibm.com> writes:

> Eric W. Biederman wrote:
>> I do not want to get into a big debate on the merits of various
>> techniques at this time.  We seem to be in basic agreement
>> about what we are talking about.
>>
>> There is one thing I think we can all agree upon.
>> - Everything except isolation at the network device/L2 layer, does not
>>   allow guests to have the full power of the linux networking stack.
> Agree.
>>
>> - There has been a demonstrated use for the full power of the linux
>>   networking stack in containers..
> Agree.
>>
>> - There are a set of techniques which look as though they will give
>>   us full speed when we do isolation of the network stack at the
>>   network device/L2 layer.
> Agree.

Herbert Poetzl <herbert@13thfloor.at> writes:
> correct, don't get me wrong, I'm absolutely not against
> layer 2 virtualization, but not at the expense of light-
> weight layer 3 isolation, which _is_ the traditional way
> 'containers' are built (see BSD, solaris ...)


Ok.  So on this point we agree.  Full isolation at the network device/L2 level
is desirable and no one is opposed to that.

There is however a strong feeling especially for the case of application
containers that something more focused on what a non-privileged process can
use and deal with would be nice.  The ``L3'' case.

I agree that has potential but I worry about 2 things.
- Premature optimization.
- A poor choice of semantics.
- Feature creep leading to insane semantics.

I feel there is something in the L3 arguments as well and it sounds
like it would be a good idea to flush out the semantics.

For full network isolation we have the case that every process,
every socket, and every network device belongs to a network namespace.
This is enough to derive the network namespace for all other user
visible data structures, and to a large extent to define their semantics.

We still need a definition of the non-privileged case, that is compatible
with the former definition.

.....

What unprivileged user space gets to manipulate are sockets.  So perhaps
we can break our model into a network socket namespace and network device
namespace.  

I would define it so that for each socket there is exactly one network
socket namespace.  And for each network socket namespace there is exactly
one network device namespace.

The network socket namespace would be concerned with the rules for deciding
which local addresses a socket can connect/accept/bind to.

The network device namespace would be concerned with everything else.

The problem I see are the wild card binds.  In general unmodified
server applications want to bind to *:port by default.  Running
two such applications on different ip addresses is a problem.  Even
if you can configure them not to do that it becomes easy to do that
be default.

There are some interesting flexible cases where we want one
application container to have one port on IP, and a different
application container to have a different port on the same IP.

So we need something flexible and not just based on IP addresses.
I think the right answer here is a netfilter table that defines
what we can accept/bind/connect the socket to.

The tricky part is when do we return -EADDRINUSE.

I think we can specify the rules such that if we conflict with
another socket in the same socket namespace the rules remain
as they are today, and the kernel returns it unconditionally.

I think for cases across network socket namespaces it should
be a matter for the rules, to decide if the connection should
happen and what error code to return if the connection does not
happen.

There is a potential in this to have an ambiguous case where two
applications can be listening for connections on the same socket
on the same port and both will allow the connection.  If that
is the case I believe the proper definition is the first socket
that we find that will accept the connection gets the connection.

I believe this is a sufficiently general definition that we can
make it work with network types in the kernel including DECNET, IP,
and IPv6.

The only gain I see for having the socket namespace is socket
collision detection, and a convenient tag to distinguish containers.

I think this set of netfilter rules may be an interesting alternative
to ip connection tracking in the current firewall code.

... 

Assuming the above scheme works does that sound about what people
actually want to use?

I think with the appropriate set of rules it provides what is needed
for application migration.  I.e. 127.0.0.1 can be filtered so that
you can only connect to sockets in your current container.

It does get a little odd because it does allow for the possibility
that you can have multiple connected sockets with same source ip,
source port, destination ip, destination port.  If the rules are
setup appropriately.  I don't see that peculiarity being visible on
the outside network so it shouldn't be a problem.

Eric
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Eric W. Biederman wrote:

[ snip ]

>>
>> The packets arrive to the real device and go through the routes
>> engine. From this point, the used route is enough to know to which
>> container the traffic can go and the sockets subset assigned to the
>> container.
> 
> Note this has potentially the highest overhead of them all because
> this is the only approach in which it is mandatory to inspect the
> network packets to see which container they are in.

If the container is in the route information, when you use the route, 
you have the container destination with it. I don't see the overhead here.

> 
> My real problem with this approach besides seriously complicating
> the administration by not delegating it is that you loose enormous
> amounts of power.

I don't understand why you say administration is more complicated.
unshare -> ifconfig

1 container = 1 IP

[ snip ]

> So you have two columns that you rate these things that I disagree
> with, and you left out what the implications are for code maintenance.
> 
> 1) Network setup.
>    Past a certainly point both bind filtering and Daniel's L3 use a new
>    paradigm for managing the network code and become nearly impossible for
>    system administrators to understand.  The classic one is routing packets
>    between machines over the loopback interface by accident. Huh?

What is this new paradigm you are talking about ?

> 
> The L2. Network setup iss simply the cost of setting up a multiple
> machine network.  This is more complicated but it is well understood
> and well documented today.  Plus for the common cases it is easy to
> get a tool to automate this for you.  When you get a complicated
> network this wins hands down because the existing tools work and
> you don't have to retrain your sysadmins to understand what is
> happening.

unshare -> (guest) add mac address
            (host) add mac address
	   (guest) set ip address
            (host) set ip address
            (host) setup bridge

1 container = 2 net devices (root + guest), 2 IPs, 2 mac addresses, 1 
bridge.
100 containers = 200 net devices, 200 IPs, 200 mac addresses, 1 bridge.

> 
> 2) Runtime Overhead.
> 
> Your analysis is confused. Bind/Accept filter is much cheaper than
> doing a per packet evaluation in the route cache of which container
> it belongs to.  Among other things Bind/Accept filtering allows all
> of the global variables in the network stack to remain global and
> only touches a slow path.  So it is both very simple and very cheap.
> 
> Next in line comes L2 using real network devices, and Daniel's
> L3 thing.  Because there are multiple instances of the networking data
> structures we have an extra pointer indirection.

There is not extra networking data structure instantiation in the 
Daniel's L3.
> 
> Finally we get L2 with an extra network stack traversal, because
> we either need the full power of netfilter and traffic shaping
> gating access to what a node is doing or we simply don't have
> enough real network interfaces.  I assert that we can optimize
> the lack of network interfaces away by optimizing the drivers
> once this becomes an interesting case.
> 
> 3) Long Term Code Maintenance Overhead.
> 
> - A pure L2 implementation.  There is a big one time cost of
>   changing all of the variable accesses.  Once that transition
>   is complete things just work.  All code is shared so there
>   is no real overhead.
> 
> - Bind/Connect/Accept filtering.  There are so few places in
>   the code this is easy to maintain without sharing code with
>   everyone else.

For isolation too ? Can we build network migration on top of that ?

> 
> - Daniel's L3.  A big mass of special purpose code with peculiar
>   semantics that no one else in the network stack cares about
>   but is right in the middle of the code.

Thanks Eric for all your comments.

   -- Daniel
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On Tue, Nov 28, 2006 at 09:51:57AM -0700, Eric W. Biederman wrote:
> 
> I do not want to get into a big debate on the merits of various
> techniques at this time.  We seem to be in basic agreement
> about what we are talking about.
> 
> There is one thing I think we can all agree upon.
> - Everything except isolation at the network device/L2 layer, does not
>   allow guests to have the full power of the linux networking stack.
> 
> - There has been a demonstrated use for the full power of the linux
>   networking stack in containers..

  - There has been a demonstrated use for the full performance 
    IP layer isolation too, both in BSD and Linux for several
    years now ...

> - There are a set of techniques which look as though they will give
>   us full speed when we do isolation of the network stack at the
>   network device/L2 layer.
> 
> Is there any reason why we don't want to implement network namespaces
> without the full power of the linux network stack?

duplicate negation ->

  "Is there any reason why we _want_ to implement network namespaces
   _with_ the full power of the linux network stack?"

yes, I think you have some reasons for doing so, especially
the migration part seems to depend on it

OTOH, we _also_ want IP isolation, as it allows to separate
services (and even handle overlapping sets) in a very natural
(linux) way, without adding interfaces and virtual switches
and bridges at a potentially high overhead just to do simple
layer 3 isolation

> If there is a case where we clearly don't want the full power of the
> linux network stack in a guest but we still need a namespace we can
> start looking at the merits of the alternatives.

see above, of course, all cases can be 'simulated' by a
fully blown layer 2 virtualization, so that's not an argument
but OTOH, all this can also be achieved with Xen, so we
could as well bring the argument, why have network namespaces
at all, if you can get the same functionality (including the
migration) with a Xen domU ...

> > What is this new paradigm you are talking about ?
> 
> The basic point is this.  The less like stock linux the inside of a
> container looks, and the more of a special case it is the more
> confusing it is.  The classic example is that for a system container
> routing packets between containers over the loopback interface is
> completely unexpected.

I disagree here, from the point of isolation that would be
the same as saying:

  "having a chroot(), it is completely unexpected that
   the files reside on the same filesystem and even will
   be cached in the same inode cache"

the thing is, once you depart from the 'container' = 'box'
idea, and accept that certain resources are shared (btw,
one of the major benefits of 'containers' over things like
Xen or UML) you can easily accept that:

 - host local traffic uses loopback
 - non local traffic uses the appropriate interfaces
 - guests _are_ local on the host, so 
 - guest - guest and guest - host traffic _is_ local
   an therefore will be more performant than remote
   traffic (unless you add various virtual switches and
   bridges and stacks to the pathes)

> > There is not extra networking data structure instantiation in the
> > Daniel's L3.
> Nope just an extra field which serves the same purpose.
> 
> >> - Bind/Connect/Accept filtering.  There are so few places in
> >>   the code this is easy to maintain without sharing code with
> >>   everyone else.
> >
> > For isolation too ? Can we build network migration on top of that ?
> 
> As long as you can take your globally visible network address 
> with you when you migrate you can build network migration on 
> top of it.  So yes bind/accept filtering is sufficient to 
> implement migration, if you are only using IP based protocols.

correct, don't get me wrong, I'm absolutely not against
layer 2 virtualization, but not at the expense of light-
weight layer 3 isolation, which _is_ the traditional way
'containers' are built (see BSD, solaris ...)

HTC,
Herbert

> Eric
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Eric W. Biederman wrote:
 > I do not want to get into a big debate on the merits of various
 > techniques at this time.  We seem to be in basic agreement
 > about what we are talking about.
 >
 > There is one thing I think we can all agree upon.
 > - Everything except isolation at the network device/L2 layer, does not
 >   allow guests to have the full power of the linux networking stack.
Agree.
 >
 > - There has been a demonstrated use for the full power of the linux
 >   networking stack in containers..
Agree.
 >
 > - There are a set of techniques which look as though they will give
 >   us full speed when we do isolation of the network stack at the
 >   network device/L2 layer.
Agree.

 > Is there any reason why we don't want to implement network namespaces
 > without the full power of the linux network stack?
Don't make me wrong, I never said layer 2 should not be used. I am only
arguing a layer 3 should use the mechanism provided by the layer 2 and
use a subset of it like the sockets virtualization/isolation.

Just IP isolation for lightweight containers, applications containers in
order to have mobility.

 > If there is a case where we clearly don't want the full power of the
 > linux network stack in a guest but we still need a namespace we can
 > start looking at the merits of the alternatives.
Dmitry and I, we are looking for a l3 based on a subset of the l2 and
according with Herbert needs.
If we can provide a l3 isolation based on the l2 which:
  - does not collide with l2
  - fit the needs of Herbert
  - allows the migration
  - use common code between l2 and l3
Should it not be sufficient to justify to have a l3 with the l2 isolation ?

 >> What is this new paradigm you are talking about ?
 >
 > The basic point is this.  The less like stock linux the inside of a
 > container looks, and the more of a special case it is the more
 > confusing it is.  The classic example is that for a system container
 > routing packets between containers over the loopback interface is
 > completely unexpected.

Right for system container, but not necessary for application containers.

 >
 >> There is not extra networking data structure instantiation in the
 >> Daniel's L3.
 > Nope just an extra field which serves the same purpose.
 >
 >>> - Bind/Connect/Accept filtering.  There are so few places in
 >>>   the code this is easy to maintain without sharing code with
 >>>   everyone else.
 >> For isolation too ? Can we build network migration on top of that ?

 > As long as you can take your globally visible network address with you
 > when you migrate you can build network migration on top of it.  So yes
 > bind/accept filtering is sufficient to implement migration, if you are
 > only using IP based protocols.

When you migrate an application, you must cleanup related sockets on the
source machine. The cleanup can not rely on the IP addresses because you
will be not able to discriminate all the sockets related to the
container. Another stuff is the network objects life-cycle, the
container will die when the application will finish, the timewait
sockets will stay until all data are flushed to peer. You can not
restart a new container with the same IP address, so you need to monitor
the socket before relaunching a new container or unmounting the aliased
interface associated with the container. You need a ref counting for the
container and this refcount is exactly what has the network namespace.
Another example, you can not have several application binding to
INADDR_ANY:port without conflict. The multiport instantiation is exactly
what brings the sockets isolation/virtualization with the l2/l3.


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On Tue, Nov 28, 2006 at 02:50:03PM -0700, Eric W. Biederman wrote:
> Daniel Lezcano <dlezcano@fr.ibm.com> writes:
> 
> > Eric W. Biederman wrote:
> >> I do not want to get into a big debate on the merits of various
> >> techniques at this time.  We seem to be in basic agreement
> >> about what we are talking about.
> >>
> >> There is one thing I think we can all agree upon.
> >> - Everything except isolation at the network device/L2 layer, does not
> >>   allow guests to have the full power of the linux networking stack.
> > Agree.
> >>
> >> - There has been a demonstrated use for the full power of the linux
> >>   networking stack in containers..
> > Agree.
> >>
> >> - There are a set of techniques which look as though they will give
> >>   us full speed when we do isolation of the network stack at the
> >>   network device/L2 layer.
> > Agree.
> 
> Herbert Poetzl <herbert@13thfloor.at> writes:
> > correct, don't get me wrong, I'm absolutely not against
> > layer 2 virtualization, but not at the expense of light-
> > weight layer 3 isolation, which _is_ the traditional way
> > 'containers' are built (see BSD, solaris ...)

> Ok. So on this point we agree. Full isolation at the network device/L2
> level is desirable and no one is opposed to that.

> There is however a strong feeling especially for the case of
> application containers that something more focused on what a
> non-privileged process can use and deal with would be nice. 
> The ``L3'' case.

> I agree that has potential but I worry about 2 things.
> - Premature optimization.
> - A poor choice of semantics.
> - Feature creep leading to insane semantics.

> I feel there is something in the L3 arguments as well and it sounds
> like it would be a good idea to flush out the semantics.

> For full network isolation we have the case that every process, 
> every socket, and every network device belongs to a network namespace.

> This is enough to derive the network namespace for all other user
> visible data structures, and to a large extent to define their
> semantics.

> We still need a definition of the non-privileged case, that is 
> compatible with the former definition.

yep, sounds interesting ...

> .....
> 
> What unprivileged user space gets to manipulate are sockets. 
> So perhaps we can break our model into a network socket namespace
> and network device namespace.

> I would define it so that for each socket there is exactly one 
> network socket namespace. And for each network socket namespace 
> there is exactly one network device namespace.

> The network socket namespace would be concerned with the rules for
> deciding which local addresses a socket can connect/accept/bind to.

> The network device namespace would be concerned with everything else.

hmm, guess I've read the word 'semantics' so many times
now, and always in conjunction with insane and unexpected,
so I think it can't hurt to explain the semantics behind
what we currently use once again, maybe I'm missing something

first, what we currently do:

 - a network context consists of a bunch of flags, and
   a set of ip addresses 

 - a process is either part of exactly one such context
   or unrestricted

 - at bind() time, collisions are checked (in the * case)
   and addresses are verified against the assigned set
   
 - at lookup() time, addresses are checked against the
   assigned set (again in the * case)

 - for queries, addresses are checked against the set, and
   if the address is found, the corresponding device will
   be visible (basically per address)

 - for guest originating traffic, the src address will
   be picked from the set, where the first assigned IP
   is handled special as 'last resort' if no better one
   can be found

here now the semantics:

 - bind() can be done for all IP/port pairs which do not
   conflict with existing sockets 
   [identical to the current behaviour]

 - bind() to * is handled like a bind() for each address
   in the assigned set of IPs (if one fails, then the
   entire bind will fail)
   [identical behaviour, subset]

 - lookup() will only match sockets which match the address
   where * now means any IP from the IP set
   [identical behaviour, subset]

 - the source address has to reside within the IP set for
   outgoing traffic

 - netinfo/proc are filtered according to the rule
   address in set -> show address/interface

except for the last one, the behaviour is identical to the
current linux networking behaviour. the hiding of unavailable
interfaces/addresses is a virtualization mechanism we use to
make it look like a separate box, which is sometimes necessary
for certain applications and humans :)

> The problem I see are the wild card binds.  In general unmodified
> server applications want to bind to *:port by default.  Running
> two such applications on different ip addresses is a problem.  Even
> if you can configure them not to do that it becomes easy to do that
> be default.

those are working and running perfectly fine, the only
time you have to take care of such applications is when you
start them outside any isolation container

> There are some interesting flexible cases where we want one
> application container to have one port on IP, and a different
> application container to have a different port on the same IP.

> So we need something flexible and not just based on IP addresses.
> I think the right answer here is a netfilter table that defines
> what we can accept/bind/connect the socket to.

I'm fine with such an approach, given that this can be used
to get reasonably similar semantics as above wihtout jumping
thorugh hoops

> The tricky part is when do we return -EADDRINUSE.

IMHO not at all, see the 'simple' semantics above

> I think we can specify the rules such that if we conflict with
> another socket in the same socket namespace the rules remain
> as they are today, and the kernel returns it unconditionally.
> 
> I think for cases across network socket namespaces it should
> be a matter for the rules, to decide if the connection should
> happen and what error code to return if the connection does not
> happen.
> 
> There is a potential in this to have an ambiguous case where two
> applications can be listening for connections on the same socket
> on the same port and both will allow the connection.  If that
> is the case I believe the proper definition is the first socket
> that we find that will accept the connection gets the connection.

that is what I call 'unexpected behaviour' ....

> I believe this is a sufficiently general definition that we can
> make it work with network types in the kernel including DECNET, 
> IP, and IPv6.

no idea about decnet, but for IP and IPv6 the beforementioned
semantics work quite fine ...

> The only gain I see for having the socket namespace is socket
> collision detection, and a convenient tag to distinguish containers.

well, you would need the tag anyway IMHO, otherwise I don't
see a way to map the netfilter chains/rules to the 'guests'
or am I missing something here?

> I think this set of netfilter rules may be an interesting alternative
> to ip connection tracking in the current firewall code.
> 
> ... 
> 
> Assuming the above scheme works does that sound about what people
> actually want to use?

from my PoV, folks want to use chbind() to 'jail' a group
of processes (or a single process) to a subset of IP
addresses ...

> I think with the appropriate set of rules it provides what is needed
> for application migration.  I.e. 127.0.0.1 can be filtered so that
> you can only connect to sockets in your current container.
> 
> It does get a little odd because it does allow for the possibility
> that you can have multiple connected sockets with same source ip,
> source port, destination ip, destination port.  If the rules are
> setup appropriately. I don't see that peculiarity being visible on
> the outside network so it shouldn't be a problem.

to the outside it looks perfectly normal, as it does on
the inside ... just the host has the 'full picture'

best,
Herbert

> Eric
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On Tue, Nov 28, 2006 at 09:26:52PM +0100, Daniel Lezcano wrote:
> Eric W. Biederman wrote:
>  > I do not want to get into a big debate on the merits of various
>  > techniques at this time.  We seem to be in basic agreement
>  > about what we are talking about.
>  >
>  > There is one thing I think we can all agree upon.
>  > - Everything except isolation at the network device/L2 layer, does not
>  >   allow guests to have the full power of the linux networking stack.
> Agree.
>  >
>  > - There has been a demonstrated use for the full power of the linux
>  >   networking stack in containers..
> Agree.
>  >
>  > - There are a set of techniques which look as though they will give
>  >   us full speed when we do isolation of the network stack at the
>  >   network device/L2 layer.
> Agree.
> 
>  > Is there any reason why we don't want to implement network namespaces
>  > without the full power of the linux network stack?
> Don't make me wrong, I never said layer 2 should not be used. I am only
> arguing a layer 3 should use the mechanism provided by the layer 2 and
> use a subset of it like the sockets virtualization/isolation.
> 
> Just IP isolation for lightweight containers, applications containers in
> order to have mobility.
> 
>  > If there is a case where we clearly don't want the full power of the
>  > linux network stack in a guest but we still need a namespace we can
>  > start looking at the merits of the alternatives.
> Dmitry and I, we are looking for a l3 based on a subset of the l2 and
> according with Herbert needs.
> If we can provide a l3 isolation based on the l2 which:
>   - does not collide with l2
>   - fit the needs of Herbert
>   - allows the migration
>   - use common code between l2 and l3
> Should it not be sufficient to justify to have a l3 with the l2 
> isolation?

sounds good to me ...

>  >> What is this new paradigm you are talking about ?
>  >
>  > The basic point is this.  The less like stock linux the inside of a
>  > container looks, and the more of a special case it is the more
>  > confusing it is.  The classic example is that for a system container
>  > routing packets between containers over the loopback interface is
>  > completely unexpected.
> 
> Right for system container, but not necessary for application containers.

yep

best,
Herbert

>  >> There is not extra networking data structure instantiation in the
>  >> Daniel's L3.
>  > Nope just an extra field which serves the same purpose.
>  >
>  >>> - Bind/Connect/Accept filtering.  There are so few places in
>  >>>   the code this is easy to maintain without sharing code with
>  >>>   everyone else.
>  >> For isolation too ? Can we build network migration on top of that ?
> 
>  > As long as you can take your globally visible network address with you
>  > when you migrate you can build network migration on top of it.  So yes
>  > bind/accept filtering is sufficient to implement migration, if you are
>  > only using IP based protocols.
> 
> When you migrate an application, you must cleanup related sockets on the
> source machine. The cleanup can not rely on the IP addresses because you
> will be not able to discriminate all the sockets related to the
> container. Another stuff is the network objects life-cycle, the
> container will die when the application will finish, the timewait
> sockets will stay until all data are flushed to peer. You can not
> restart a new container with the same IP address, so you need to monitor
> the socket before relaunching a new container or unmounting the aliased
> interface associated with the container. You need a ref counting for the
> container and this refcount is exactly what has the network namespace.
> Another example, you can not have several application binding to
> INADDR_ANY:port without conflict. The multiport instantiation is exactly
> what brings the sockets isolation/virtualization with the l2/l3.
> 
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Eric W. Biederman wrote:
> I think for cases across network socket namespaces it should
> be a matter for the rules, to decide if the connection should
> happen and what error code to return if the connection does not
> happen.
> 
> There is a potential in this to have an ambiguous case where two
> applications can be listening for connections on the same socket
> on the same port and both will allow the connection.  If that
> is the case I believe the proper definition is the first socket
> that we find that will accept the connection gets the connection.

Wouldn't you want to catch this at bind() and/or configuration time and 
fail?  Having overlapping namespaces/rules seems undesirable, since as 
Herbert said, can get you "unexpected behaviour".

> I think with the appropriate set of rules it provides what is needed
> for application migration.  I.e. 127.0.0.1 can be filtered so that
> you can only connect to sockets in your current container.
> 
> It does get a little odd because it does allow for the possibility
> that you can have multiple connected sockets with same source ip,
> source port, destination ip, destination port.  If the rules are
> setup appropriately.  I don't see that peculiarity being visible on
> the outside network so it shouldn't be a problem.

So if they're using the same protocol (eg TCP), how is it decided which 
one gets an incoming packet?  Maybe I'm missing something as I don't 
understand your inside/outside network reference - is that to the 
loopback address comment in the previous paragraph?

Thanks,

-Brian
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On Sun, 2006-03-12 at 17:37 +0100, Herbert Poetzl wrote:
> On Sun, Dec 03, 2006 at 07:26:02AM -0500, jamal wrote:

> To use an extreme example: if i picked apache as a
> > binary compiled 10 years ago, it will run on the L2 approach but not on
> > the L3 approach. Is this understanding correct?  I find it hard to
> > believe that the L3 approach wouldnt work this way - it may be just my
> > reading into the doc.
> 
> the 10 year old apache will run with layer 3 isolation
> as well as with layer 2 virtualization (probably a little
> faster though, we do not know yet :), because what it 
> does is IP (layer 3) traffic ...
> 

Ok, thanks for clarifying this.

> > I think the litmus test for this approach is the answer to the question:
> > If i compiled in the containers in and do not use the namespaces, how
> > much more overhead is there for the host path? I would hope that it is
> > as close to 0 as possible. It should certainly be 0 if i dont compile in
> > containers.
> 
> IMHO there are three cases to consider, to get valid
> 'performance' numbers:
> 
>  - host system with and without containers enabled
>  - single guest (container) compared to host system _without_

Sound reasonable.

>  - bunch of guests (e.g. 10) compared to 10 apps/threads on host
> 

Your mileage may vary. For me trying to run virtual routers; this is
not an important test. I want to be able to have containers each running
quagga and OSPF. I cant achieve my goals with with 10 quaggas without
making some major changes to quagga.
 
> one proven feature of the L3 isolation is that those
> all end up with the same or even better performance

I think it is valuable to reduce the overhead. I think that it may be
reasonable to some threshold to trade a little performance for
genericity. What the threshold is, i dont know.

> > - Manageability from the host side. It seems to be more complex with the
> > L2 than with L3. But so what? These tools are written from scratch and
> > there is no "backward compatibility" baggage.
> 
> well, no, actually the 'tools' to manage layer 3 isolation
> are already there, 
> and except for the 'setup' there is
> nothing special to configure, as networking still lives
> on the host
> 

I dont see the two as being separate issues. You must create container;
you must configure networking on them; it is forgivable to have the
second part of that process to involve some non-standard tools for the
containers (from the host).
It is not forgivable to have speacilized tools within the container.

> I would be interested in a config layout for a typical
> L3 isolation setup when you 'only' have L2 virtualization
> 
>  - typical host system with apache, mysql, postfix, ssh
>    and ftp is broken down into security contexts to
>    allow for increased security
>  - as part of that process, the services are isolated,
>    while apache and ftp share the same ip [ip0], mysql
>    will be using a local one [ip1], and postfix/ssh a 
>    second public one [ip2]
> 
> the L3 isolation approach is straight forward:
> 
>  - assign the two public ips to eth0, the local one
>    to lo or dummy0
>  - create five isolation areas where 0 and 1 share ip0, 
>    2 uses ip1 and 3,4 uses ip2
> 
> that's it, all will work as expected ... let's see with
> what L2 isolation example you come up with, which is 
> able to 'mimic' this setup ...
> 
> note: no question it is possible to do that with L2

Unless i am misreading, isnt this merely a matter of configuring
on the container side eth0 (I think you are talking about VE side eth0
in your example above) two public ip addresses (or even two ethx
devices) and then attach IP addresses to them? mysql gets an lo address.
Would this not work?

Out of curiosity: assume we have a local LAN (perhaps something upstream
does NAT), is it possible to have the same IP address going to multiple
containers?

cheers,
jamal



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On Sun, Dec 03, 2006 at 07:26:02AM -0500, jamal wrote:
> On Wed, 2006-14-11 at 16:17 +0100, Daniel Lezcano wrote:
> > The attached document describes the network isolation at the layer 2
> > and at the layer 3 ..
> 
> Daniel,
> 
> I apologize for taking this long to get back to you. The document (I
> hope) made it clear to me at least the difference between the two
> approaches. So thanks for taking the time to put it together.
> 
> So here are my thoughts ...
> I havent read the rest of the thread so i may be repeating some of the
> discussion; i have time today, I will try to catchup with the
> discussion.
> 
> * i think the L2 approach is the more complete of the two approaches:
> 
> It caters to more applications: eg i can have network elements such as
> virtual bridges and routers. It doesnt seem like i can do that with the
> L3 approach. I think this in itself is a powerful enough reason to
> disqualify the L3 approach.
> 
> Leading from the above, I dont have to make _a single line of code
> change_ to any of the network element management tools inside the
> container. i.e i can just run quagga and OSPF and BGP will work as is or
> the bridge daemon and STP will work as is or tc to control "real"
> devices or ip to control "real" ip addresses. Virtual routers and
> bridges are real world applications (if you want more info ask me or ask
> google, she knows).
> 
> **** This wasnt clear to me from the doc on the L3 side of things, so
> please correct me: 
> because of the pid virtualization in the L2 approach(openvz?) I can run
> all applications as is. They just dont know they are running on a
> virtual environment. To use an extreme example: if i picked apache as a
> binary compiled 10 years ago, it will run on the L2 approach but not on
> the L3 approach. Is this understanding correct?  I find it hard to
> believe that the L3 approach wouldnt work this way - it may be just my
> reading into the doc.

the 10 year old apache will run with layer 3 isolation
as well as with layer 2 virtualization (probably a little
faster though, we do not know yet :), because what it 
does is IP (layer 3) traffic ...

> So lets say the approach taken is that of L2 (I am biased towards this
> because i want to be able to do virtual bridges and routers). 
> The disadvantage of the L2 approach (or is it just the openvz?)
> approach is:
> 
> - it is clear theres a lot more code needed to allow for the two level
> multiplexing every where. i.e first you mux to select the namespace then
> you do other things like find a pid, netdevice, ip address etc. I am
> also not sure how complete that code is; you clearly get everything
> attached to netdevices for free (eg networkc scheduler block) - which is
> nice in itself; but you may have to do the muxing code for other blocks.
> If my understanding is correct everything in the net subsystem has this
> mux levels already in place (at least with openvz)? I think each
> subsystem may have its own merit discussed (eg the L3 tables with the
> recent changes from Patrick allow up to 2^32 -1 tables, so a muxing
> layer at L3 maybe unnecessary)

> ---> To me this 2 level muxing looks like a clean design in that there
> is consistency (i.e no hack thats specific to just one sub-subsystem but
> not others). With this approach one could imagine hardware support that
> does the first level of muxing (selecting a namespace for you). This is
> clearly already happening with NICs supporting several unicast MAC
> addresses. 

> I think the litmus test for this approach is the answer to the question:
> If i compiled in the containers in and do not use the namespaces, how
> much more overhead is there for the host path? I would hope that it is
> as close to 0 as possible. It should certainly be 0 if i dont compile in
> containers.

IMHO there are three cases to consider, to get valid
'performance' numbers:

 - host system with and without containers enabled
 - single guest (container) compared to host system _without_
 - bunch of guests (e.g. 10) compared to 10 apps/threads on host

one proven feature of the L3 isolation is that those
all end up with the same or even better performance

> - The desire for many MAC addresses. I dont think this is a killer
> issue. NICs are begining to show up which capabilities for many unicast
> MACs; many current have multicast hardware tables that can be used for
> stashing unicast MAC addresses; it has also been shown you can use
> multicast MAC addresses and get away with it if there is no conflict
> (protocols such as VRRP, CARP etc do this).
> 
> - Manageability from the host side. It seems to be more complex with the
> L2 than with L3. But so what? These tools are written from scratch and
> there is no "backward compatibility" baggage.

well, no, actually the 'tools' to manage layer 3 isolation
are already there, and except for the 'setup' there is
nothing special to configure, as networking still lives
on the host

> Ok, I am out of coffee for the last 10 minutes;-> But above sit my views
> worth about $0.02 Canadian (which is about $0.02 US these days).
> 
> I will try later to catch up with the discussion that started from
> Daniels original posting.

I would be interested in a config layout for a typical
L3 isolation setup when you 'only' have L2 virtualization

 - typical host system with apache, mysql, postfix, ssh
   and ftp is broken down into security contexts to
   allow for increased security
 - as part of that process, the services are isolated,
   while apache and ftp share the same ip [ip0], mysql
   will be using a local one [ip1], and postfix/ssh a 
   second public one [ip2]

the L3 isolation approach is straight forward:

 - assign the two public ips to eth0, the local one
   to lo or dummy0
 - create five isolation areas where 0 and 1 share ip0, 
   2 uses ip1 and 3,4 uses ip2

that's it, all will work as expected ... let's see with
what L2 isolation example you come up with, which is 
able to 'mimic' this setup ...

note: no question it is possible to do that with L2

best,
Herbert

> cheers,
> jamal
> 
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Herbert Poetzl <herbert@13thfloor.at> writes:

> On Mon, Dec 04, 2006 at 06:19:00PM +0300, Dmitry Mishin wrote:
>> On Sunday 03 December 2006 19:00, Eric W. Biederman wrote:
>> > Ok.  Just a quick summary of where I see the discussion.
>> >
>> > We all agree that L2 isolation is needed at some point.
>
>> As we all agreed on this, may be it is time to send patches
>> one-by-one? For the beggining, I propose to resend Cedric's 
>> empty namespace patch as base for others - it is really empty, 
>> but necessary in order to move further.
>> 
>> After this patch and the following net namespace unshare 
>> patch will be accepted, 
>
> well, I have neither seen any performance tests showing
> that the following is true:
>
>  - no change on network performance without the 
>    space enabled
>  - no change on network performance on the host
>    with the network namespaces enabled
>  - no measureable overhead inside the network
>    namespace 
>  - good scaleability for a larger number of network
>    namespaces 

Yes all important criteria for selecting the implementation.

Eric
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On Mon, Dec 04, 2006 at 08:02:48PM +0300, Dmitry Mishin wrote:
> On Monday 04 December 2006 19:43, Herbert Poetzl wrote:
> > On Mon, Dec 04, 2006 at 06:19:00PM +0300, Dmitry Mishin wrote:
> > > On Sunday 03 December 2006 19:00, Eric W. Biederman wrote:
> > > > Ok.  Just a quick summary of where I see the discussion.
> > > >
> > > > We all agree that L2 isolation is needed at some point.
> > >
> > > As we all agreed on this, may be it is time to send patches
> > > one-by-one? For the beggining, I propose to resend Cedric's
> > > empty namespace patch as base for others - it is really empty,
> > > but necessary in order to move further.
> > >
> > > After this patch and the following net namespace unshare
> > > patch will be accepted,
> >
> > well, I have neither seen any performance tests showing
> > that the following is true:
> >
> >  - no change on network performance without the
> >    space enabled
> >  - no change on network performance on the host
> >    with the network namespaces enabled
> >  - no measureable overhead inside the network
> >    namespace
> >  - good scaleability for a larger number of network
> >    namespaces

> These questions are for complete L2 implementation, 
> not for these 2 empty patches. 

well, I fear that we will have lot of overhead
'sneaking' in via small patches (with almost
unnoticeable overhead) making the 2.6 branch slower
and slower (regarding networking) so IMHO a complete
solution should be drafted, and tested performance
wise, we can then adjust it and possibley improve
it, untill it shows no measureable overhead ...

but IMHO it should be developed 'outside' the kernel,
in small and reviewable pieces which are constantly
updated to match the recent kernels ... something
like stacked git or quilt ...

> If you need some data relating to Andrey's
> implementation, I'll get it. Which test do you accept?

hmm, I think a good mix of netperf, netpipe and
iperf would be a good start, probably network folks
know better tests to exercise the stack ... at least
I hope so ...

of course, a good explanation _why_ this or that
code path does not add overhead here or there is
nice to have too ...

best,
Herbert

> > > I could send network devices virtualization patches for
> > > review and discussion.
> >
> > that won't hurt ...
> >
> > best,
> > Herbert
> >
> > > What do you think?
> > >
> > > > The approaches discussed for L2 and L3 are sufficiently orthogonal
> > > > that we can implement then in either order.  You would need to
> > > > unshare L3 to unshare L2, but if we think of them as two separate
> > > > namespaces we are likely to be in better shape.
> > > >
> > > > The L3 discussion still has the problem that there has not been
> > > > agreement on all of the semantics yet.
> > > >
> > > > More comments after I get some sleep.
> > > >
> > > > Eric
> > > > -
> > > > To unsubscribe from this list: send the line "unsubscribe netdev" in
> > > > the body of a message to majordomo@vger.kernel.org
> > > > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > >
> > > --
> > > Thanks,
> > > Dmitry.
> > > _______________________________________________
> > > Containers mailing list
> > > Containers@lists.osdl.org
> > > https://lists.osdl.org/mailman/listinfo/containers
> 
> -- 
> Thanks,
> Dmitry.
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Dmitry Mishin wrote:
> On Monday 04 December 2006 19:43, Herbert Poetzl wrote:
>> On Mon, Dec 04, 2006 at 06:19:00PM +0300, Dmitry Mishin wrote:
>>> On Sunday 03 December 2006 19:00, Eric W. Biederman wrote:
>>>> Ok.  Just a quick summary of where I see the discussion.
>>>>
>>>> We all agree that L2 isolation is needed at some point.
>>> As we all agreed on this, may be it is time to send patches
>>> one-by-one? For the beggining, I propose to resend Cedric's
>>> empty namespace patch as base for others - it is really empty,
>>> but necessary in order to move further.
>>>
>>> After this patch and the following net namespace unshare
>>> patch will be accepted,
>> well, I have neither seen any performance tests showing
>> that the following is true:
>>
>>  - no change on network performance without the
>>    space enabled
>>  - no change on network performance on the host
>>    with the network namespaces enabled
>>  - no measureable overhead inside the network
>>    namespace
>>  - good scaleability for a larger number of network
>>    namespaces
> These questions are for complete L2 implementation, not for these 2 empty 
> patches. If you need some data relating to Andrey's implementation, I'll get 
> it. Which test do you accept?

tbench ?

With the following scenarii:

  * intra host communication (one time with IP on eth and one time with 
127.0.0.1)
  * inter host communication

Each time:
	- a single network namespace
	- with 100 network namespace. 1 server communicating and 99 listening 
but doing nothing.


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Herbert Poetzl <herbert@13thfloor.at> writes:

>> But, ok, it is not the real point to argue so much imho and waste our
>> time instead of doing things.
>
> well, IMHO better talk (and think) first, then implement
> something ... not the other way round, and then start
> fixing up the mess ...

Well we need a bit of both.

This is thankfully not exported to user space, so as long as our
implementation is correct it doesn't much matter.

I do agree with the point that context may make sense.  I have
yet to be convinced though.

Eric
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On Sat, 9 Dec 2006 04:50:02 +0100
Herbert Poetzl <herbert@13thfloor.at> wrote:

> On Fri, Dec 08, 2006 at 12:57:49PM -0700, Eric W. Biederman wrote:
> > Herbert Poetzl <herbert@13thfloor.at> writes:
> > 
> > >> But, ok, it is not the real point to argue so much imho 
> > >> and waste our time instead of doing things.
> 
> > > well, IMHO better talk (and think) first, then implement
> > > something ... not the other way round, and then start
> > > fixing up the mess ...
> > 
> > Well we need a bit of both.
> 
> hmm, are 'we' in a hurry here?
> 
> until recently, 'Linux' (mainline) didn't even want
> to hear about OS Level virtualization, now there
> is a rush to quickly get 'something' in, not knowing
> or caring if it is usable at all?

It's actually happening quite gradually and carefully.

> I think there are a lot of 'potential users' for
> this kind of virtualization, and so 'we' can test
> almost all aspects outside of mainline, and once
> we know the stuff works as expected, then we can
> integrate it ...
> 
> the UTS namespace was something 'we all' had already
> implemented in this (or a very similar) way, and in
> one or two interations, it should actually work as 
> expected. nevertheless, it was one of the simplest
> spaces ...
> 
> we do not yet know the details for the IPC namespace,
> as IPC is not that easy to check as UTS, and 'we'
> haven't gotten real world feedback on that yet ...

We are very dependent upon all stakeholders including yourself to review,
test and comment upon this infrastructure as it is proposed and merged.
If something is proposed which will not suit your requirements then it
is important that we hear about it, in detail, at the earliest possible time.

Thanks.
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Herbert Poetzl <herbert@13thfloor.at> writes:

> On Fri, Dec 08, 2006 at 12:57:49PM -0700, Eric W. Biederman wrote:
>> Herbert Poetzl <herbert@13thfloor.at> writes:
>> 
>> >> But, ok, it is not the real point to argue so much imho 
>> >> and waste our time instead of doing things.
>
>> > well, IMHO better talk (and think) first, then implement
>> > something ... not the other way round, and then start
>> > fixing up the mess ...
>> 
>> Well we need a bit of both.
>
> hmm, are 'we' in a hurry here?

We need to talk about code, and particular patches not just talk.

There are two sides to what we are building.
- The user interface, and semantics.
- The kernel implementation.

For the user interface getting it as close to perfect as we can
the first time is extremely important.  Because we won't be able
to change it.

For the kernel implementation we don't have to be perfect we have
to have something that is good enough.  We can change the
implementation every release if we find better ways of implementing
our user space semantics. 

> until recently, 'Linux' (mainline) didn't even want
> to hear about OS Level virtualization, now there
> is a rush to quickly get 'something' in, not knowing
> or caring if it is usable at all?
>
> I think there are a lot of 'potential users' for
> this kind of virtualization, and so 'we' can test
> almost all aspects outside of mainline, and once
> we know the stuff works as expected, then we can
> integrate it ...

We should do this as part of the linux kernel community.  There
is no outside of mainline development.  We need to get feedback from
other developers whose code we may effect.  This is particularly true
of the kernel networking stack.

> that's something I do not really agree with, stuff
> integrated into the kernel should be well designed
> and it should be tested ...

Yes but you can break a problem into reasonable chunks and
solve each of those pieces individually. 

Eric




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On Fri, Dec 08, 2006 at 12:57:49PM -0700, Eric W. Biederman wrote:
> Herbert Poetzl <herbert@13thfloor.at> writes:
> 
> >> But, ok, it is not the real point to argue so much imho 
> >> and waste our time instead of doing things.

> > well, IMHO better talk (and think) first, then implement
> > something ... not the other way round, and then start
> > fixing up the mess ...
> 
> Well we need a bit of both.

hmm, are 'we' in a hurry here?

until recently, 'Linux' (mainline) didn't even want
to hear about OS Level virtualization, now there
is a rush to quickly get 'something' in, not knowing
or caring if it is usable at all?

I think there are a lot of 'potential users' for
this kind of virtualization, and so 'we' can test
almost all aspects outside of mainline, and once
we know the stuff works as expected, then we can
integrate it ...

the UTS namespace was something 'we all' had already
implemented in this (or a very similar) way, and in
one or two interations, it should actually work as 
expected. nevertheless, it was one of the simplest
spaces ...

we do not yet know the details for the IPC namespace,
as IPC is not that easy to check as UTS, and 'we'
haven't gotten real world feedback on that yet ...

so personally I think we should start some serious
testing on the upcoming namespaces, and we should
continue discussing the various approaches, until
'we' can agree on the (almost) 'perfect' solution

> This is thankfully not exported to user space, so as long 
> as our implementation is correct it doesn't much matter.

that's something I do not really agree with, stuff
integrated into the kernel should be well designed
and it should be tested ...

best,
Herbert

> I do agree with the point that context may make sense. 
> I have yet to be convinced though.
> 
> Eric
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On Fri, Dec 08, 2006 at 10:13:48PM -0800, Andrew Morton wrote:
> On Sat, 9 Dec 2006 04:50:02 +0100
> Herbert Poetzl <herbert@13thfloor.at> wrote:
> 
> > On Fri, Dec 08, 2006 at 12:57:49PM -0700, Eric W. Biederman wrote:
> > > Herbert Poetzl <herbert@13thfloor.at> writes:
> > > 
> > > >> But, ok, it is not the real point to argue so much imho 
> > > >> and waste our time instead of doing things.
> > 
> > > > well, IMHO better talk (and think) first, then implement
> > > > something ... not the other way round, and then start
> > > > fixing up the mess ...
> > > 
> > > Well we need a bit of both.
> > 
> > hmm, are 'we' in a hurry here?
> > 
> > until recently, 'Linux' (mainline) didn't even want
> > to hear about OS Level virtualization, now there
> > is a rush to quickly get 'something' in, not knowing
> > or caring if it is usable at all?
> 
> It's actually happening quite gradually and carefully.

hmm, I must have missed a testing phase for the
IPC namespace then, not that I think it is broken
(well, maybe it is, we do not know yet)

> > I think there are a lot of 'potential users' for
> > this kind of virtualization, and so 'we' can test
> > almost all aspects outside of mainline, and once
> > we know the stuff works as expected, then we can
> > integrate it ...
> > 
> > the UTS namespace was something 'we all' had already
> > implemented in this (or a very similar) way, and in
> > one or two interations, it should actually work as 
> > expected. nevertheless, it was one of the simplest
> > spaces ...
> > 
> > we do not yet know the details for the IPC namespace,
> > as IPC is not that easy to check as UTS, and 'we'
> > haven't gotten real world feedback on that yet ...
> 
> We are very dependent upon all stakeholders including yourself 
> to review, test and comment upon this infrastructure as it is 
> proposed and merged. If something is proposed which will not 
> suit your requirements then it is important that we hear about 
> it, in detail, at the earliest possible time.

okay, good to hear that I'm still considered a stakeholder 

will try to focus the feedback and cc as many folks
as possible, as it seems that some feedback is lost
on the way upstream ...

best,
Herbert

> Thanks.
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