IP checksum calculation not done

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ninj4

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IP checksum calculation not done
« on: January 05, 2018, 06:01:22 AM »
Hello folks,

I am using zodiac fx switch to perform kind of NAT operation which requires to modify source and destination IP address.
However, i am facing an issue that after the rule is matched and the action of modifying the IP is done, the IP checksum isn't calculated by the switch.
 This is leading to a lot of problems as the packets are being discarded due to checksum failures.

Has anybody faced this issue earlier, and are there some suggestions as to how to work around this problem.

Thanks.

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Paul Zanna

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Re: IP checksum calculation not done
« Reply #1 on: January 05, 2018, 07:19:27 AM »
I'm not aware of a checksum calculation issue, can you please provide more information on when you are experiencing this issue.
Most packet monitoring tools (tcpdump, wireshark, etc.) report incorrect checksum values due to the calculation being offloaded to the network card. More information about this can be found here - Wireshark FAQ

Regards,
Paul

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ninj4

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Re: IP checksum calculation not done
« Reply #2 on: January 06, 2018, 04:27:33 AM »
The topology i have can be considered as follows :
10.0.1.2<------->switch<------>10.0.1.3
                                   ^
                                   |
                                   |
                                   V
                             10.0.1.4


So the IP address modification rules i have are provided below.

Flow 11
 Match:
  ETH Type: IPv4
  Source IP:  10.0.1.2
  Destination IP:  10.0.1.3
 Attributes:
  Table ID: 0                           Cookie:0x0
  Priority: 3000                                Duration: 3 secs
  Hard Timeout: 100 secs                        Idle Timeout: 0 secs
  Byte Count: 0                 Packet Count: 0
  Last Match: 00:00:03
 Instructions:
  Apply Actions:
   Set Source IP:  10.0.1.4
  Goto Table: 1



Flow 10
 Match:
  ETH Type: IPv4
  Source IP:  10.0.1.3
  Destination IP:  10.0.1.4
 Attributes:
  Table ID: 0                           Cookie:0x0
  Priority: 3000                                Duration: 3 secs
  Hard Timeout: 100 secs                        Idle Timeout: 0 secs
  Byte Count: 0                 Packet Count: 0
  Last Match: 00:00:03
 Instructions:
  Apply Actions:
   Set Destination IP:  10.0.1.2
  Goto Table: 1

Table 1 contains normal routing rules.

After these rules when any of the IPs receive a packet whose source or destination IP is modified by the switch, they show a IP header checksum error on wireshark.

On the other hand, for normal openflow rules to forward to a particular port, there is no error.
Flow 8
 Match:
  ETH Type: IPv4
  Destination IP:  10.0.1.4
 Attributes:
  Table ID: 1                           Cookie:0x1
  Priority: 35                          Duration: 958 secs
  Hard Timeout: 0 secs                  Idle Timeout: 1800 secs
  Byte Count: 5194                      Packet Count: 53
  Last Match: 00:15:33
 Instructions:
  Apply Actions:
   Set Source MAC: BE:64:00:2D:C7:03
   Set Destination MAC: 6C:3B:E5:35:C1:BC
   Output Port: 2

 How i see this problem is that, primarily for any flow which doesn't require IP address modification, everything works fine.
But, for flows requiring IP address modification, the IP header checksum is not calculated and hence packets are discarded at the end hosts.


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ninj4

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Re: IP checksum calculation not done
« Reply #3 on: January 08, 2018, 12:40:31 AM »
Hi,

Do let me know if the information provided above is enough, or something else is needed too.

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ninj4

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Re: IP checksum calculation not done
« Reply #4 on: January 22, 2018, 04:51:50 AM »
Hello, I hope this thread doesn't go on in sleep mode.

I am stuck with my project because of this issue and is eagerly awaiting response.

Thanks.

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Paul Zanna

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Re: IP checksum calculation not done
« Reply #5 on: January 22, 2018, 07:00:17 AM »
Hi,

I'm doing the v0.83 firmware update now and reviewing the checksum calc so I'll have something for you soon.

Regards,
Paul

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ninj4

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Re: IP checksum calculation not done
« Reply #6 on: January 23, 2018, 06:15:51 AM »
Thanks a lot Paul.

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ninj4

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Re: IP checksum calculation not done
« Reply #7 on: January 28, 2018, 06:19:56 AM »
Hello Paul,

Is there a deadline you are targeting for releasing the new firmware?
One of my research projects heavily depend on this to work, it would be great if this could be done as soon as possible.

Regards,

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Paul Zanna

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Re: IP checksum calculation not done
« Reply #8 on: February 03, 2018, 03:05:27 PM »
This issue has now fixed in v0.83 which can be downloaded from HERE

Regards,
Paul