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What cases Native wifi module drops the RX packet which is greater than 1500 bytes? RRS feed

  • Question

  • Hi All,
    I am seeing an issue with our Miniport wireless driver running on windows-7, where the native wifi module is dropping Rx packet if it is bigger than 1500 bytes.
    If we are trying pinging to the AP using command "ping [ip address] -l 1470" - able to get reply successfully. But it is failing, if we are trying by specifying length greater than 1470 bytes.
    We have analysed network stack by using Network monitor and able to see the ping reply in NDIS layer but it is not reaching the application layer. We have verified it by 
    using netstat (netstat -s -p icmp) statistics and found that icmp reply didn't reach till icmp/ip layer. Looks like the NDIS/nwifi is dropping the packet.
    We have some doubts on issue with driver indicating packet to NDIS, missing any NDIS Rx Flags. We are not getting any prints(Debugview) from TCPIP stack, 
    I want to know in which criteria Native wifi module will drop the RX packet which is greater than 1500 bytes.

    Regard

    Aswin PP


    • Edited by Aswin PP Friday, June 17, 2016 3:11 PM
    Friday, June 17, 2016 3:10 PM

Answers

  • Hi All,

    The issue gets solved, Actually, we are indicating wrong RxData length to NDIS.
    While calculating the Data length from the Rx Buffer, we forget to reduce QOS specific 2Bytes from the length.
    That causes packets with more than 1500 bytes reaches in IP layer...So native wifi module will drop these packet (>1500) without reaching IP layer.
    Accidentally the IP layer packets exceed 1500 and Dropping.

    Regards
    Aswin PP



    • Marked as answer by Aswin PP Tuesday, June 21, 2016 6:45 AM
    • Edited by Aswin PP Tuesday, June 21, 2016 6:54 AM
    Tuesday, June 21, 2016 6:41 AM

All replies

  • Does the driver implement any TCP offloads?

    Saturday, June 18, 2016 1:15 AM
  • Hi Pavel,

    Actually TCP Stack is not offloaded to the Driver

    Saturday, June 18, 2016 6:58 PM
  • Hi All,

    The issue gets solved, Actually, we are indicating wrong RxData length to NDIS.
    While calculating the Data length from the Rx Buffer, we forget to reduce QOS specific 2Bytes from the length.
    That causes packets with more than 1500 bytes reaches in IP layer...So native wifi module will drop these packet (>1500) without reaching IP layer.
    Accidentally the IP layer packets exceed 1500 and Dropping.

    Regards
    Aswin PP



    • Marked as answer by Aswin PP Tuesday, June 21, 2016 6:45 AM
    • Edited by Aswin PP Tuesday, June 21, 2016 6:54 AM
    Tuesday, June 21, 2016 6:41 AM