[lwip-users] [bug #62302] LWIP 2.0.2 / Xilinx Zynq: TCP hang data transmission after packets loss events

[Nir]

URL:
  <https://savannah.nongnu.org/bugs/?62302>

                 Summary: LWIP 2.0.2 / Xilinx Zynq: TCP hang data transmission
after packets loss events
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: nirshem
            Submitted on: Tue 12 Apr 2022 10:17:06 AM UTC
                Category: TCP
                Severity: 3 - Normal
              Item Group: Faulty Behaviour
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: None
            lwIP version: 2.0.2

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Details:

Hi,

An issue I’m working on for a while.

My setup as follow:

1)      Unit A: Embedded unit: Xilinx board (Zynq 7020) running FreeRTOS +LWIP
2.0.2
2)      Unit B: PC client running WIN10

Connectivity between the units is fiber – and I added sniffer in the middle
for debugging of the issue.

Unit A transmit in TCP (LWIP 2.0.2) data at around 1.7[Mbps] to unit B.

The problem: after hour of system running the throughput is dropped to zero
(except of TCP keep alive) and return back after around 6 seconds.

After reviewing the Wireshark in the middle (connected via sniffer) I found a
3 dup acks event that cause fast retransmission reply,

>From that moment the Application traffic stopped for 6 seconds and only TCP
keep alive was active.

After checking the location of the packet loss I can tell for sure it was in
the PC side (running Iperf UDP test client /server locally shows some packet
loss due to the load on the PC).

I attached two wiresharks files of two events.

Now my question are: 

1)      Why there is a drop in the traffic from Unit A ? 

2)      Why Fast recovery is not working as it should after fast retransmission
event ? 

3)      Is there a way to fix it by timers/windows size configuration ?

4)      Is there a known issue about it ? – I looked on the change log since
2.0.2 and haven't found something special.

Any help here will be much appreciated.




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File Attachments:


-------------------------------------------------------
Date: Tue 12 Apr 2022 10:17:06 AM UTC  Name: Event_1.pcapng  Size: 123KiB  
By: nirshem

<http://savannah.nongnu.org/bugs/download.php?file_id=53079>
-------------------------------------------------------
Date: Tue 12 Apr 2022 10:17:06 AM UTC  Name: Event_2.pcapng  Size: 286KiB  
By: nirshem

<http://savannah.nongnu.org/bugs/download.php?file_id=53080>

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