Accessing tftpd in wsl2 docker container

Problem: Connect to tftpd in Docker from WSL2.


Client tftp is running inside wsl2 ubuntu

Server is tftpd-hpa running inside docker for windows started from wsl2 ubuntu

Windows firewall should be irrelevant, however it is also disabled completelty


Summary:

I can udp netcat from Alice to Bob port 69
I can tftp load a file inside Bob
When I tftp from Alite to netcat on Bob I see tftp traffic coming in
But I can not tftp load a file in Alice from Bob, connection timeout

**** ?????

Reproduction:

I installed WSL2 on Windows 10 V 2004 with Ubuntu V20.04
I installed Docker for Windows.
I installed Ubuntu V20.04 in Docker.


Two terminals, Alice is wsl2 bash, Bob is Docker bash; docker run.



Bob: nc -ul4 69

Alice: nc -u 127.0.0.1 69

-> Both can chat



Bob: start nc -ul4 69

Alice: tftp 127.0.0.1

get test.txt

-> Bob can see alice talking tftp



Bob: start tftpd-hpa with option -4

Bob: tftp 127.0.0.1

get test.txt

-> Bob can download a file from its own tftpd



Bob: start tftpd-hpa with option -4

Alice: tftp 127.0.0.1

get test.txt

-> Timeout this is unexpected



Netstat on Alice and Bob look exactly identical in both cases nc and tftpd.


Bob:


Active Internet connections servers and established

Proto Recv-Q Send-Q Local Address Foreign Address State

udp 0 0 0.0.0.0:tftp 0.0.0.0:*



Alice:



Active Internet connections servers and established

Proto Recv-Q Send-Q Local Address Foreign Address State

udp6 0 0 [::]:tftp [::]:*



Fyi: Using the internal wsl2 ip instead of 127.0.0.1 makes no difference.


Question:

Any explaination ?


Next steps:

logging I got no /var/log/messages yet and tethereal ?



Exclusions:

I will not install a linux docker inside WSL2 as this is a commercial project and not recommended


Thanks a lot, apreciated.

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