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

[Junxiao Shi]

Hi Salvatore

How about running two NFD instances?

ndnpeek    ndnpoke
   |          |
 NFD1       NFD2
   |          |
 veth1      veth2
   |          |
   your program

You can have two NFD instances running on the same host by specifying different nfd.conf files on “--config” parameter. Each nfd.conf should have distinct Unix socket path and port numbers. If you need to edit nfd.conf in a script, check out infoedit.

Then, have ndnpeek and ndnpoke connect to different NFD instances by specifying different client.conf, like:
mkdir -p /tmp/ndnpoke-home/.ndn
echo transport=unix:/var/run/nfd1.sock > /tmp/ndnpoke-home/.ndn/client.conf
HOME=/tmp/ndnpoke-home ndnpoke /A
mkdir -p /tmp/ndnpeek-home/.ndn
echo transport=unix:/var/run/nfd2.sock > /tmp/ndnpeek-home/.ndn/client.conf
HOME=/tmp/ndnpeek-home ndnpeek /A

Yours, Junxiao

From: Salvatore Signorello
Sent: Wednesday, January 6, 2016 05:52
To: Junxiao Shi
Cc: <nfd-dev at lists.cs.ucla.edu>
Subject: Re: [Nfd-dev] generatation of NDN-like packets with Scapy

Hi Junxiao,

thanks again, but I forgot to tell that changing that piece of software is not worth doing (long and complex process), I must use it as it is. This brings us back to my original dilemma of writing an application that sends ndn packets to specific network interfaces or simply writing a module for a packet generator? How difficult would be to do the former?


Best,
Salvatore
On Jan 6, 2016 01:40, "Salvatore Signorello" <salvatore.signorello at uni.lu> wrote:
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?
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