Azure APIM throws error for WebSocket API due to Connection: Keep-Alive,Upgrade

Question

I have REST and WebSocket APIs on the Azure API Management services portal. WebSocket is redirecting to different Web Pubsub service based on input parameters from clients/frontend for different development environments.

When hitting WebSocket api from Google Chrome, I am able to successfully establish connection end-to-end.
When hitting same WebSocket api from Firefox, I am getting InvalidWebsocketUpgrade error from APIM service.

This happens because Chrome is sending Connection: Upgrade in the socket connection request header, while Firefox is sending Connection: Keep-Alive, Upgrade in the header.

Chrome Request:

GET wss://apim-test.azure-api.net/qa/socket?access_token=eyJhbGc HTTP/1.1
Host: apim-ecv.azure-api.net
Connection: Upgrade
Pragma: no-cache
Cache-Control: no-cache
User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/94.0.4606.71 Safari/537.36
Upgrade: websocket
Origin: https://abc.xyz.com
Sec-WebSocket-Version: 13
Accept-Encoding: gzip, deflate, br
Accept-Language: en-GB,en-US;q=0.9,en;q=0.8
Sec-WebSocket-Key: GTWCGvTFJN82sAl8gVv+VA==
Sec-WebSocket-Extensions: permessage-deflate; client_max_window_bits
Sec-WebSocket-Protocol: json.webpubsub.azure.v1

Firefox request:

GET wss://apim-test.azure-api.net/qa/socket?access_token=eyJhbGciOi HTTP/1.1
Host: apim-ecv.azure-api.net
User-Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:96.0) Gecko/20100101 Firefox/96.0
Accept: */*
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate, br
Sec-WebSocket-Version: 13
Origin: https://az-qa2.ecarevault.com
Sec-WebSocket-Protocol: json.webpubsub.azure.v1
Sec-WebSocket-Extensions: permessage-deflate
Sec-WebSocket-Key: r764n2hSpKKr0Y63z1Ok3A==
Connection: keep-alive, Upgrade
Sec-Fetch-Dest: websocket
Sec-Fetch-Mode: websocket
Sec-Fetch-Site: cross-site
Pragma: no-cache
Cache-Control: no-cache
Upgrade: websocket

Do I need to configure anything to support this on APIM or anywhere else??

Answer 1

@pratik Thanks for reaching out. Using anything other than Upgrade in the Connection header would be a violation of the WebSocket protocol. You can refer to this document. So it looks like the problem is with the Firefox extension that's acting as a WebSocket client or the Firefox browser itself).

Feel free to get back to me if you have any queries or concerns.

Update:
As of now APIM web socket the allowed header Connection value as Upgrade. This would be the feature request and the ETA for this will be 4-5 months from now.