[uml-devel] uml_switch

[uml-devel] uml_switch

[Nelio Pereira]

Hi list..

I'm using UML to benchmark a distributed protocol
(cluster membership service) on a virtual network. As
a way of injecting faults, I thought about changing
uml_switch so it would not forward every message it
receives. Roughly speaking, it could deliver only a
percentage of the messages. 

I would like to know where in the uml_switch code is
the best place to do that. Actually, I'd like to
intercept those messages in a place where I could know
the sender and recipient IP of each message.

Thanks,

Nelio

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Re: [uml-devel] uml_switch

[Nuno Silva]

Nelio Pereira wrote:
> Hi list..

Hi!


> 
> I'm using UML to benchmark a distributed protocol
> (cluster membership service) on a virtual network. As
> a way of injecting faults, I thought about changing
> uml_switch so it would not forward every message it
> receives. Roughly speaking, it could deliver only a
> percentage of the messages. 
> 
> I would like to know where in the uml_switch code is
> the best place to do that. Actually, I'd like to
> intercept those messages in a place where I could know
> the sender and recipient IP of each message.
> 


I remember seeing, here, that someone ported uml_switch to python... 
Maybe that's easier to hack?

Hope this helps,
Nuno Silva


> Thanks,
> 
> Nelio
> 
> =====
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> 
> Yahoo! Mail - o melhor webmail do Brasil
> http://mail.yahoo.com.br
> 
> 
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Re: [uml-devel] uml_switch

[Nelio Pereira]

The code itself doesn't seem very complicated. I just
would like to know how a message is transmited to its
recipient, then I could intercept this message in the
right place.

Nelio

 --- Nuno Silva <nuno.silva@vgertech.com> escreveu: > 
> 
> Nelio Pereira wrote:
> > Hi list..
> 
> Hi!
> 
> 
> > 
> > I'm using UML to benchmark a distributed protocol
> > (cluster membership service) on a virtual network.
> As
> > a way of injecting faults, I thought about
> changing
> > uml_switch so it would not forward every message
> it
> > receives. Roughly speaking, it could deliver only
> a
> > percentage of the messages. 
> > 
> > I would like to know where in the uml_switch code
> is
> > the best place to do that. Actually, I'd like to
> > intercept those messages in a place where I could
> know
> > the sender and recipient IP of each message.
> > 
> 
> 
> I remember seeing, here, that someone ported
> uml_switch to python... 
> Maybe that's easier to hack?
> 
> Hope this helps,
> Nuno Silva
> 
> 
> > Thanks,
> > 
> > Nelio
> > 
> > =====
> >
>
+------------------------------------------------------------------------+
> >                       
> http://www.ime.usp.br/~nelio
> > 
> > Yahoo! Mail - o melhor webmail do Brasil
> > http://mail.yahoo.com.br
> > 
> > 
> >
>
-------------------------------------------------------
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> relations
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>
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> > User-mode-linux-devel@lists.sourceforge.net
> >
>
https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
> > 
>  

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Re: [uml-devel] uml_switch

[Jeff Dike]

nelio_pereira@yahoo.com.br said:
> The code itself doesn't seem very complicated. I just would like to
> know how a message is transmited to its recipient, then I could
> intercept this message in the right place. 

As Matt said, this is an Ethernet switch, and as such, knows nothing about
IP.  The stuff inside the frames may not even be IP.

				Jeff



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Re: [uml-devel] uml_switch

[Matt Zimmerman]

On Thu, Oct 23, 2003 at 07:55:24AM -0300, Nelio Pereira wrote:

> I would like to know where in the uml_switch code is the best place to do
> that. Actually, I'd like to intercept those messages in a place where I
> could know the sender and recipient IP of each message.

I haven't checked the code, but I don't think that uml_switch decodes the IP
header at all; it only deals with Ethernet frames.

-- 
 - mdz


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Re: [uml-devel] uml_switch

[steven james]

Greetings,

Of course, UML itself 'just happens' to use the configured IP address
(mildly mangled) as the MAC address for IP traffic.

However, it would be best to add functionality to parse the packet
headers. Definatly NOT wanted for normal use due to efficiency
issues. Perhaps a config option? compile time?

G'day,
sjames



On Thu, 23 Oct 2003, Matt Zimmerman wrote:

> On Thu, Oct 23, 2003 at 07:55:24AM -0300, Nelio Pereira wrote:
> 
> > I would like to know where in the uml_switch code is the best place to do
> > that. Actually, I'd like to intercept those messages in a place where I
> > could know the sender and recipient IP of each message.
> 
> I haven't checked the code, but I don't think that uml_switch decodes the IP
> header at all; it only deals with Ethernet frames.
> 
> 

-- 
-------------------------steven james, director of research, linux labs
... ........ ..... ....                    230 peachtree st nw ste 2701
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Re: [uml-devel] uml_switch

[Adam Heath]

On Sat, 25 Oct 2003, steven james wrote:

> Greetings,
>
> Of course, UML itself 'just happens' to use the configured IP address
> (mildly mangled) as the MAC address for IP traffic.

Not for my setup.  I set the mac address of my umls on the cmdline, they talk
to a uml switch, which also happens to be configured to forward to the host.
My umls then use dhcp to get their address.



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Re: [uml-devel] uml_switch

[Matt Zimmerman]

On Sat, Oct 25, 2003 at 10:42:23AM -0400, steven james wrote:

> Of course, UML itself 'just happens' to use the configured IP address
> (mildly mangled) as the MAC address for IP traffic.

...as a default if it isn't specified.

> However, it would be best to add functionality to parse the packet
> headers. Definatly NOT wanted for normal use due to efficiency issues.
> Perhaps a config option? compile time?

I think it's probably not necessary for the purpose he mentioned; matching
the MAC address is just as good (if not better).  Of course, it would be
even easier to use a tap device instead of uml_switch, and use iptables to
do the matching, which will be much more flexible.

-- 
 - mdz


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Re: [uml-devel] uml_switch

[BlaisorBlade]

Alle 12:55, giovedì 23 ottobre 2003, Nelio Pereira ha scritto:
> Hi list..
>
> I'm using UML to benchmark a distributed protocol
> (cluster membership service) on a virtual network. As
> a way of injecting faults, I thought about changing
> uml_switch so it would not forward every message it
> receives. Roughly speaking, it could deliver only a
> percentage of the messages.

Just use iptables. It's simpler. Download patch-o-matic: then use either 
base/nth.patch or base/random.patch(the second is maybe better) for the 
kernel that will have to support this new option. Then, to filter it, you 
must find a point where to apply the rule. I think the simpler one is to set 
up a bridge as specified for TUN/TAP in the networking page and then add the 
rule on the host FORWARD chain adding -i(or -o) br0. Or maybe, you should add 
it somewhere else(for instance, just use tap devices without a bridge, then 
add that rule with -i tap+ and -o tap+ on FORWARD: it will match packets 
being forwarded on the host between UML's).
>
> I would like to know where in the uml_switch code is
> the best place to do that. Actually, I'd like to
> intercept those messages in a place where I could know
> the sender and recipient IP of each message.

-- 
cat <<EOSIGN
Paolo Giarrusso, aka Blaisorblade
Linux Kernel 2.4.21/2.6.0-test on an i686; Linux registered user n. 292729
EOSIGN



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