[Nfd-dev] generatation of NDN-like packets with Scapy

Wed Jan 6 00:40:22 PST 2016

Hi Junxiao,

thanks for your prompt feedback, below follows a short description of my 
quick&dirty "set-up" and then few more comments in-line:

Scenario in mind (caveat: I don't know if it makes sense, but that's 
what I need; so if you think of an alternative, as I guess you already 
did according to your previous suggestion, please feel free of throwing 
away what follows and propose sth else)
-----------------------
On the same machine where nfd is running, I use the ndnpeedk to generate 
an Interest with prefixA. My nfd has a rule that forwards Interests with 
prefixA out to a specific veth1. On that veth1 I have some software 
running that processes the Interest and then forwards the same Interest 
back to the nfd through a different interface, veth2. In the meantime 
I've started a local producer (ndnpoke -w) for that content that 
correctly receives the Interest(the 2nd one received on veth and not the 
1st one issued by ndnpeek) and answers back with the Data. The nfd 
forwards the data back to veth2, the software processes it and then 
forwards it to nfd through veth1. Nfd forwards the data back to ndnpeek.

Why am I doing this? I need two applications, one consumer and one 
producer, like ndnpeek and ndnpoke that generate ndn packets.

The problems that I would like to avoid are the following:
- the pit record for the Interest issued by ndnpeek risks to  drop the 
Interest received on veth2 [SOLVED] I change the nonce when I process 
the Interest for the 2nd time.
- ndnpeek and ndnpoke cannot be started simultaneously, otherwise 
ndnpoke will provide the Data to ndnpeek in one step
- if the 1st Interest creates a PIT record, how to avoid that nfd will 
use it when receiving Data from ndnpoke? The daemon will have a PIT 
record like the following
         "prefixA/content ---- facex(local to ndnpeek), facey(to veth2)"
     and it should choose only facey

Quick and dirty workaround
-----------------------------------------
By now I simulate the scenario above in the following way:
1. Starting nfd and registering prefixA to veth1 with the nfdc cmd
2. Issuing an Interest for prefixA/content with ndnpeek
3. The Interest is correctly forwarded to my software through veth1 
where I hold it for a while
4. After ndnpeek timeout, I unregister prefixA from nfd
5. Starting ndnpoke for prefixA/content with a long waiting time
6. Unpausing my software that forwards the original Interest to nfd 
through veth2
7. nfd forwards it to ndnpoke and I get the data back from veth2
8. holding again the Data
9. register prefixA again like done in 2
10. issuing a new Interest with ndnpeek
11. unpausing the Data to forwarded it back first to nfd and then to ndnpeek

Crazy, isn't it?

On 01/05/2016 01:35 PM, Junxiao Shi wrote:
>
> Hi Salvatore
>
> I'll offer a different idea to solve your problem: pretend to be NDN 
> forwarder.
>
> NDN programs recognizes $HOME/.ndn/client.conf, and connects to the 
> NDN forwarder specified in "transport" option. 
> http://named-data.net/doc/ndn-cxx/current/manpages/ndn-client.conf.html
>

Cool, I didn't know about this config option. I guess this does mean 
that the local apps use TCP instead of Unix socket as transport 
connection towards the local forwarder. Have I got it right?
>
> You can point the transport to the TCP port or Unix socket listener of 
> your next stage, and use existing NDN programs.
>
My other stage is a veth. Does it make any difference with what you're 
thinking of? After reading this one, I'm not sure that I've got the 
previous sentence well. Could you please elaborate a little bit 
according to the scenario I've described.
>
> Consumer programs should with just fine.
> Producer programs need small modifications: bypass prefix registration 
> step.
>
> Yours, Junxiao
>
> On Jan 5, 2016 05:27, "Salvatore Signorello" 
> <salvatore.signorello at uni.lu <mailto:salvatore.signorello at uni.lu>> wrote:
>
>     Hi all,
>
>     I would like to generate some NDN packets that are not processed
>     in a first stage by the NFD daemon, so I guess that I cannot use
>     ready-made things like ndnpeek/pook/ping/etc.
>
>     Has anyone already implemented an NDN module for a packet
>     generator like Scapy? If so, or if there exists other ways to do
>     that, could you please point me to the right resources?
>
>     Do I really need to write a module for a packet generator? I mean:
>     does the ndn-repo have anything else that may fit the purpose?
>
>     Any help would be really appreciated,
>     Salvatore
>
>     -- 
>     Salvatore Signorello
>     PhD student @ SecanLab
>
>     Interdisciplinary Centre for Security, Reliability and Trust
>     SnT, University of Luxembourg
>     http://wwwen.uni.lu/snt/people/salvatore_signorello
>
>     _______________________________________________
>     Nfd-dev mailing list
>     Nfd-dev at lists.cs.ucla.edu <mailto:Nfd-dev at lists.cs.ucla.edu>
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>

-- 
Salvatore Signorello
PhD student @ SecanLab

Interdisciplinary Centre for Security, Reliability and Trust
SnT, University of Luxembourg
http://wwwen.uni.lu/snt/people/salvatore_signorello

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