Wireshark-users: Re: [Wireshark-users] Filtering ICMP Packets Based onIP Addresses in the ICMP Pa
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From: Merton Campbell Crockett <m.c.crockett@xxxxxxxxxxxxxx>
Date: Sun, 31 May 2009 08:47:57 -0700

On 31 May 2009, at 02:43:30, Sake Blok wrote:


In an earlier mail you said:

"The problem that is being investigated only occurs with
clients that connect to the server over a WAN.  Clients connecting to
the server over a LAN do not experience the problem."
Combined with the fact that you see a TCP reset on the events that you are investigating leads me to believe the problem lies in devices that keep session state (firewalls, IDP, Loadbalancers, etc). Every device that keeps session states has a mechanism to flush old sessions, otherwise their table would grow forever. Usually they clear out sessions that have been idle for certain amount of time. Idle being that no network traffic has been seen for that session (in some protocols the user may be idle, but network traffic is still present for the session). Other devices use an absolute timer for sessions (a mamimum time that a session may live, even when it's active), however, I have not seen this much.
If a session is flushed from the device and a new packet of that session is sent by the client or the server, it will be discarded or rejected and the intermediate device might send a reset. If it is the server sending the reset, then somehow the session was dropped on the server, instead of an intermediate device.
If the intermediate device function as a security device, the packet would most likely be discarded rather than rejected. A rejected packet triggers a response back to the sender that potentially reveals something about the network behind the device.
Now back to your original question, if you use the filter "icmp and ip.addr==x.x.x.x", it will give you all packets originating from or destined to x.x.x.x, but also all icmp packets in which the ip header in the payload contains ip address x.x.x.x. There is however no way to restric the filter to show *only* packets where x.x.x.x is in the icmp payload.
I'm an old fart. I have a tendency to write filtering expressions based on how the BSD Packet Filter works. In that environment, an "or" would be required to capture the needed traffic.
The key point to remember is that the data was captured, essentially, at the server. I was using the client's IP address as the selector for the traffic of interest. The only ICMP traffic from the client that might have been captured would have been an ICMP Source Quench or ICMP Port Unreachable.
All other ICMP traffic would have been directed to the server. Obviously, I wouldn't want to use the server's IP address in my filter as it would include all of the traffic that was captured. Adding ICMP to the expression was required to determine whether they were the trigger for some of the TCP reset packets that closed the virtual circuit between the client and the server.
The packet that triggered the ICMP response is included in the ICMP packet to allow the recipient to identify the virtual circuit having a problem. Hence my original question about filtering ICMP traffic based on the IP packet in the payload.
I can use my knowledge of network topology to exclude some ICMP packets. The problem with doing that is that you might miss a weird condition where traffic was being misrouted.
I attached a small capture file in which this can be seen, use the filter "icmp and ip.addr==194.134.5.5". The trace contains a traceroute from 192.168.1.46 to 194.134.5.5. 

Hope this helps,
Cheers,
   Sake
----- Original Message ----- From: "Merton Campbell Crockett" <m.c.crockett@xxxxxxxxxxxxxx > To: "Community support list for Wireshark" <wireshark-users@xxxxxxxxxxxxx > 
Sent: Saturday, May 30, 2009 10:51 PM
Subject: Re: [Wireshark-users] Filtering ICMP Packets Based onIP Addresses in the ICMP Payload 




On 30 May 2009, at 12:17:54, j.snelders@xxxxxxxxxx wrote:


Does this display filter help you:
(icmp.type == 3) || (icmp.type == 4)

ICMP Destination Unreachable: type = 3
Source Quench: Type = 4
Not really. Perhaps, it might be better for me to explain the problem 
that is occurring and how I collected the network traffic.

First, the network traffic was collected using a Cisco Network
Analyzer Module (NAM) at the switch port connecting to the server.  I
collected 1 GB of "raw" traffic data.  By "raw", I mean that there
were absolutely no filters defined as I wanted to capture all packets
that traversed the network segment, i.e. I wanted to capture any
"broadcast storms" that might impact the operation of the server along with any network traffic that was erroneously being routed/switched to 
the segment.

Microsoft's Office Communicator 2005 and Live Communications Server
2005 are used to provide an instant messaging capability on our
corporate network.  User's have complained that while IM'ing another
user that they will receive an error message stating that the message
that they just sent could not be delivered to one or more recipients.
Also, they report that a user in their contact list will suddenly
change from online to offline.

Management has gotten Microsoft involved in the problem.  I have not
been impressed with the technicians that have been involved in the
problem.  It was like pulling teeth to get them to explain how
"presence" was determined.  They keep saying that it is a network
problem while not being able to explain how the network and the
Windows TCP/IP stack impacts the application.

At any rate, we have determined that the "online" to "offline" state
transition is being triggered by a TCP reset.  In some instances,
there is an automatic reconnection occurring almost immediately.  In
others, the user has to stop and start Office Communicator to restore
use.

I'm trying to determine what is triggering the TCP reset.  Also, I'm
trying to determine under what conditions will the connection be
automatically restored.

Basically, I use a "tcp.flags.reset eq 1" filter to find Office
Communicator clients of interest.  I then use the "icmp or ip.addr eq
wh.at.ev.er" filter to find all events associated with the client.
Unfortunately this includes all ICMP packets regardless of where they
originated hence my original question.






On Sat, 30 May 2009 10:47:39 -0700 Merton Campbell Crockett wrote:

On 30 May 2009, at 09:54:50, Stephen Fisher wrote:


On Sat, May 30, 2009 at 09:24:22AM -0700, Merton Campbell Crockett
wrote:


In addition to looking at traffic to or from specific clients, I
want
to look at any ICMP traffic that involves the specific client.
I've
used the following filter expression.

icmp or ip.addr eq 10.10.208.211

Unfortunately, this filter includes all ICMP traffic instead of
just
the ICMP traffic that is related to 10.10.208.211.
Try "icmp and ip.addr eq 10.10.208.211" to find packets to/from that 


IP
that are ICMP -and- packets that have ICMP packets containing
traffic
to/from that IP in the ICMP payload.
Wouldn't the "icmp and ip.addr eq 10.10.208.211" expression result in only ICMP packets originating from or destined to 10.10.208.211 being 
displayed?

All that I would expect to be displayed given the above expression
are



ICMP Source Quench and ICMP Port Unreachable packets sent by the
client or the server.

What I'm really interested in seeing is how the server or client
behaves when a network device in the path between them interjects an ICMP packet. The problem that is being investigated only occurs with clients that connect to the server over a WAN. Clients connecting to 
the server over a LAN do not experience the problem.

I can exclude network devices that wouldn't be in the path between
the



client and the server by appending an expression similar to the
following to my original expression.

and !(ip.addr eq 10.73.2.2 or ip.addr eq 10.10.1.3)
Doing this, however, hides problems that might have been triggered by 
a routing flap.

Thanks, I guess I didn't miss something in the Wireshark
documentation.  :-(


Merton Campbell Crockett
m.c.crockett@xxxxxxxxxxxxxx





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