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paolodaniele's avatar
paolodaniele
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Sep 19, 2022

WSS LTM not passing data correctly

Hi, i'm having some trouble about running an Virtual Server in front of a K3s ingress. I've setted up 4 virtual server, all point to the same destination address, but different port (different pool...
error
security
virtual server
websocket
ws
wss
  • mdevlin's avatar
    mdevlin
    Oct 06, 2022

    Hi Paolo, 

    Thank you for your time today, im glad we could determine what was wrong.

    A few steps we took that helped us confirm first off, that no truncating was happening in the headers, was to capture the connection in a tcpdump with the f5 high detail peer options (:nnnp), that showed us the payload on the backend as being perfect.  No truncating happening.

    tcpdump -vvv -s0 -ni 0.0:nnnp host <f5 VIP> and port <f5 virtual server port>

     

    One of the key factors to identifying what was the issue here was something you sent me in a private message.  Removing the http profile, which subsequently resultied in the websocket, waf and clientssl profile to be removed, allowed the connection to work.  The wss:// call, not ws://.  

    Because this was a WSS or WebSocket Secure call, the server was expecting a TLS session, and our configuration was doing TLS offloading at the f5, and sending the traffic plain text to the server.  Why the application generated an "ERR_TRUNCATE_HEADERS" message is purely speculation at this point, but i suspect it was because the headers were all encrypted and thus exceeded the maximum for the application.

    I would normally expect to see 400 errors with HTTP, so the backend encryption wasnt jumping out at me sooner.

    Im glad that we could resolve this matter, and please let myself and f5 know if there is anything else we can do to assist you in the future.

    Cheers

    Mike

paolodaniele's avatar
paolodaniele
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Hi Buulam,

thank you for your answer. All i can say is that i'm quite noob with F5(i've always used other solutions) but i was able to learn quickly how it works and how to configure all things (the LTM HTTPS works fine without any problem)

All i can tell is that if i configure to pass not only TCP but instead all protocols (so no configuration of websocket or anything else) when i'm try to wscat to wss://myaddress:myport i get the Connected message and its open the wss shell. Using this configuration when i run the wss://myaddress:myport i get the answer that it expects the request ad HTTP.

This is why i'm thinking that it's me who's miss something in the config. Let me know if you want to see part of the configuration.

Thanks for your help.

Regards,

P.

buulam's avatar
buulam
Icon for Admin rankAdmin
Sep 22, 2022

Right, so the test I'm suggesting where you remove the http profile will still actually let you pass the websocket traffic. It will do so without passing through the http proxy and can isolate things further for you.