LinuxQuestions.org
Share your knowledge at the LQ Wiki.
Go Back   LinuxQuestions.org > Forums > Linux Forums > Linux - Networking
User Name
Password
Linux - Networking This forum is for any issue related to networks or networking.
Routing, network cards, OSI, etc. Anything is fair game.

Notices


Reply
  Search this Thread
Old 09-29-2009, 03:49 PM   #1
elstepherino
LQ Newbie
 
Registered: Sep 2009
Posts: 1

Rep: Reputation: 0
Using nemesis-udp to simulate local host


Looked around, couldn't find similar threads. If I missed anything, please forgive me.

Here is my setup.

1. I am using nemesis as a simulation tool for a distributed application.

2. For testing purposes, my distributed application basically listens to a UDP port (#50000) for incoming packets. When it receives the packets, it prints out the details to stdout. Packets can come from remote peers or from the localhost itself.

3. nemesis is used to simulate both the remote peers (10 of them) and the local host itself (which means the test host will receive a UDP packet on the network interface where the source and destination IP addresses are the same).


Here is my problem.

When both my test application and the nemesis program are run on the same platform (my Ubuntu laptop), everything works fine. All packets received are printed to stdout.

However, when the test application is run on a separate box (another Ubuntu platform), all except one packet are received by the test application.

I have verified the following:
- all packet contents are the same
- all destination IPs and ports are the same
- the receiving computer receives all packets, as per tcpdump
- the receiving application does not receive the UDP packet that pretends to be coming from the localhost itself.


Here is my question:
Why is the packet "pretending to be from the receiving host" not being handed over to the application?

Could it be that the network stack may be discarding packets that should have a source IP different than that of the local host itself?

Any help is appreciated.
 
Old 09-30-2009, 01:53 AM   #2
everest40
Member
 
Registered: Jul 2008
Distribution: Ubuntu $LATESTVERSION
Posts: 168

Rep: Reputation: 68
Accepting packets that claim to be coming from the local host but actually come from another device on the network is a security vulnerability. It makes it possible for potential attackers (other people on the network) to send commands or information and have them appear to come from a trusted sender (localhost), so many devices, operating systems, or firewalls will just discard such packets. I don't know if Linux is one of those operating systems, but if you're running a firewall you might try turning the firewall off or setting it to allow this kind of thing.
 
  


Reply

Tags
localhost, security, ubuntu, udp


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off



Similar Threads
Thread Thread Starter Forum Replies Last Post
Checking if a TCP/UDP connection is actually local blank87 Linux - Networking 8 07-17-2008 08:44 AM
Forward local mail to another local host using sendmail loopy69 Linux - Server 5 02-26-2008 05:38 PM
Unknown Local Host MizEllyRolls Linux - Security 3 09-14-2005 08:32 PM
Local Host? mac_casey Linux - General 7 03-02-2005 08:04 AM
local host login ? reecedeg Red Hat 5 08-10-2004 06:17 AM

LinuxQuestions.org > Forums > Linux Forums > Linux - Networking

All times are GMT -5. The time now is 03:09 AM.

Main Menu
Advertisement
My LQ
Write for LQ
LinuxQuestions.org is looking for people interested in writing Editorials, Articles, Reviews, and more. If you'd like to contribute content, let us know.
Main Menu
Syndicate
RSS1  Latest Threads
RSS1  LQ News
Twitter: @linuxquestions
Open Source Consulting | Domain Registration