still awaiting reply for previously asked question

Asked by nninan on 2010-11-30

Hi there,
            Its been almost a month since I asked my previous question and I still haven't received a reply. I have copied and pasted the contents of emails that i sent. Please give me some feedback a.s.a.p. All my wok is held up till I get the response. I have emailed you the requested files and can do so again if need be.
Regards
Nikhil

Hello again,
               I did not get the predicted outputs that you suggested, I
have attached the 8 files as two sets of tar.gz files. One for the 4 files
from system A and the other with the 4 files from system B.
Regards
Nikhil

On 07/10/2010 22:04, "Didier Barvaux" <email address hidden> wrote:

Hello,

               I have just got the test-bed for rohc setup and was
wondering whether anyone can answer a couple of questions for me as
it would be of great help.

My answers below.

1.) I set the tunnel up as specified in faq#639 with a slight
variation, ³sudo rohctunnel rohc0 remote <ip_address> local
<ip_address> port 5000
3>comp_stats 4>decomp_stats dir unidirectional²
I execute the same rohctunnel command just reversing the ip_addresses
on system A and system B. When I look on system A (from where packets
are being sent), I can see comp_stats file for info but on system B
(where packets are received) I cannot see any info in the
decomp_stats file. If anyone can shed some light on this it would be
great.

What version of the ROHC library do you use? I tested with the trunk
version and I get data written in the decomp_stats file.

Here is exactly what I did:
1/ On machine A as root on shell 1:
   # rohctunnel rohc0 remote 192.168.0.200 local 192.168.0.1 \
     port 5000 dir unidirectional \
     1>lib_output 2>tunnel_output \
     3>comp_stats 4>decomp_stats
2/ On machine A as root on shell 2:
   # ip link set rohc0 up
   # ip -4 addr add 10.1.0.1/24 dev rohc0
   # tail -f comp_stats
3/ On machine B as root on shell 1:
   # rohctunnel rohc0 remote 192.168.0.1 local 192.168.0.2 \
     port 5000 dir unidirectional \
     1>lib_output 2>tunnel_output \
     3>comp_stats 4>decomp_stats
4/ On machine B as root on shell 2:
   # ip link set rohc0 up
   # ip -4 addr add 10.1.0.2/24 dev rohc0
   # tail -f decomp_stats
5/ On machine A as root on shell 3:
   # ping -c 1 10.1.0.2

The ping is successful. On machine A shell 2, the following line was
printed:
 1 U-mode IR 84 20 85 21 0

On machine B shell 2, the following line was
printed:
 1 0 0 0

If you do not have the same result, send me the 8 files generated by
the 2 rohctunnel instances.

2.) What do the columns in the output files represent?

The columns of the comp_stats file are:
- the sequence number of the packet sent through the ROHC/UDP
  tunnel,
- the ROHC mode in which the compressor is,
- the ROHC state in which the compressor is,
- the size (in bytes) of the uncompressed IP packet,
- the size (in bytes) of the header of the uncompressed IP packet,
- the size (in bytes) of the compressed ROHC packet,
- the size (in bytes) of the header of the compressed ROHC packet.

The columns of the decomp_stats file are:
- the sequence number of the packet received through the ROHC/UDP
  tunnel,
- the total number of the packets that were not present at the output
  of the tunnel (= the sum of the 2 next columns, ie. lost packets
  plus the decompression failures),
- the number of packets lost in the tunnel (it may be real losses or
  losses due to error emulation),
- the number of packets the decompressor failed to decompress.

I have just updated the FAQ #639 to describe them.

Regards,
Didier
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Question information

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Last query:
2010-11-30
Last reply:
2011-11-21
Launchpad Janitor (janitor) said : #1

This question was expired because it remained in the 'Open' state without activity for the last 15 days.

Hello,

First sorry for the very long answer delay...

Second, I was finally able to reproduce the problem you encountered! Your problem is due to the "sudo" command. If you run the rohctunnel command I specified within sudo, it does not work as expected. The redirections are made for the sudo process, not the rohctunnel one.

With the command below, the "1>", "2>", "3>" and "4>" redirections apply to the rohctunnel process. So, the file descriptors 1, 2, 3 or 4 won't be affected to the rohc0 interface or the UDP socket. They are already reserved for one of the 4 files "lib_output", "tunnel_output", "comp_stats" or "decomp_stats".

 # rohctunnel rohc0 remote 192.168.0.200 local 192.168.0.1 \
     port 5000 dir unidirectional \
     1>lib_output 2>tunnel_output \
     3>comp_stats 4>decomp_stats

With the sudo command below, the "1>", "2>", "3>" and "4>" redirections apply to the sudo process. So, the file descriptors 1, 2, 3 or 4 may be affected to the rohc0 interface or the UDP socket. They are not reserved for one of the 4 files "lib_output", "tunnel_output", "comp_stats" or "decomp_stats".

 $ sudo rohctunnel rohc0 remote 192.168.0.200 local 192.168.0.1 \
     port 5000 dir unidirectional \
     1>lib_output 2>tunnel_output \
     3>comp_stats 4>decomp_stats

The easiest solution is to avoid sudo at all. Run a shell as root before starting the rohctunnel command:

 $ sudo /bin/bash
 # rohctunnel rohc0 remote 192.168.0.200 local 192.168.0.1 \
     port 5000 dir unidirectional \
     1>lib_output 2>tunnel_output \
     3>comp_stats 4>decomp_stats

I juste updated FAQ #639 to add a warning note about using sudo:
    IMPORTANT NOTE: please do not run the above command within sudo
    because sudo does not fit well with redirections of file descriptors.

Regards,
Didier

Changed status to Answered.

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