LinuxQuestions.org
Visit Jeremy's Blog.
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
 
LinkBack Search this Thread
Old 12-06-2012, 12:44 AM   #1
pxgxue
LQ Newbie
 
Registered: Dec 2012
Posts: 1

Rep: Reputation: Disabled
icmp echo received by GTPU tunnel, but when system do icmp reply, wrong!


Machine A, with two ip address:
eth0: 192.168.0.37
tap0: 192.168.2.100 (created by tunctl -t tap0)
Machine B, with ip: 192.168.0.50
A and B communicate with GTPU tunnel.
On machine C with 192.168.2.2, I try to ping 192.168.2.100 , ICMP echo message route to Machine B,adding GTPU header, and it can be captured on Machine A. then Machine A remove GTPU header, send to local tcp/ip stack via lo , A should response ICMP reply message. ISSUS IS HERE, The icmp reply message responsed to Machine A, in other words, the dst and src ip address in IP header field are the same both is 192.16.2.100 . So it will not be send to Machine B.
Here is TCPDUMP log on Machine A:

12:50:23.837354 IP 192.168.2.2 > 192.168.2.100: ICMP echo request, id 1024, seq 4617, length 40
0x0000: 0000 0000 0000 0000 0000 0000 0800 4500
0x0010: 003c 45d8 0000 8001 6f32 c0a8 0202 c0a8
0x0020: 0264 0800 3753 0400 1209 6162 6364 6566
0x0030: 6768 696a 6b6c 6d6e 6f70 7172 7374 7576
0x0040: 7761 6263 6465 6667 6869
12:50:23.837379 IP 192.168.2.100 > 192.168.2.100: ICMP echo reply, id 1024, seq 4617, length 40
0x0000: 0000 0000 0000 0000 0000 0000 0800 4500
0x0010: 003c 75bb 0000 4001 7eed c0a8 0264 c0a8
0x0020: 0264 0000 3f53 0400 1209 6162 6364 6566
0x0030: 6768 696a 6b6c 6d6e 6f70 7172 7374 7576
0x0040: 7761 6263 6465 6667 6869
Please give me some explain why this happen?
eth0 Link encap:Ethernet HWaddr 00:1f:d0:cc:dd:ea
inet addr:192.168.0.37 Bcast:192.168.0.255 Mask:255.255.255.0
inet6 addr: fe80::21f:d0ff:fecc:ddea/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:395387 errors:0 dropped:0 overruns:0 frame:0
TX packets:319954 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:96717645 (96.7 MB) TX bytes:72525695 (72.5 MB)
Interrupt:43 Base address:0x6000

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:78113 errors:0 dropped:0 overruns:0 frame:0
TX packets:78113 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:11138744 (11.1 MB) TX bytes:11138744 (11.1 MB)

tap0 Link encap:Ethernet HWaddr 06:37:a7:a6:ab:c3
inet addr:192.168.2.100 Bcast:192.168.2.255 Mask:255.255.255.0
UP BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:500
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)

Last edited by pxgxue; 12-06-2012 at 01:12 AM. Reason: adding more information
 
  


Reply


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
Trackbacks are Off
Pingbacks are On
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Wrong ICMP echo routing andrei.wap Linux - Networking 1 12-21-2011 02:20 PM
[SOLVED] Iptables: icmp and fragmented icmp rule matching Cenobite Linux - Networking 2 02-03-2011 03:37 AM
decress icmp reply timing orko Linux - Networking 5 03-19-2008 12:44 AM
what is a ICMP echo request? tjyorkshire Linux - Networking 4 07-03-2007 11:12 AM
icmp echo reply wont work pali Linux - Networking 2 08-17-2005 12:34 PM


All times are GMT -5. The time now is 08:28 PM.

Main Menu
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
identi.ca: @linuxquestions
Facebook: linuxquestions Google+: linuxquestions
Open Source Consulting | Domain Registration