Django channels handshake headers are ignored

[Albertas Gimbutas]

Hi,

  I want to add WebSocket extension support to my Django channels consumer class. As I know a list of accepted extensions should be included in the headers of the handshake response of the consumer. I tried adding the response headers, however browser does not get them. I am not sure whether its a bug, or I have done something wrong.

  As specified in the asgiref documentation: "websocket.accept" message can have "headers" section https://asgi.readthedocs.io/en/latest/specs/www.html#accept-send-event

  In my AsyncJsonWebsocketConsumer class I am accepting the connection with this code:

    await self.base_send({

      "type": "websocket.accept",

      "subprotocol": None,

      "headers": [(b'sec-websocket-extensions', b'permessage-deflate')]

    })

  since the original accept() method implementation does not have headers parameter https://github.com/django/channels/blob/507cb54fcb36df63282dd19653ea743036e7d63c/channels/generic/websocket.py#L184

  With this implementation latest Chrome/Firefox does not receive "Sec-WebSocket-Extensions: permessage-deflate" headeres in the handshake response. For example, I provide request and response headers:

  The request headers are:

GET ws://localhost:8080/ws/my_route/ HTTP/1.1

Host: localhost:8080

Connection: Upgrade

Pragma: no-cache

Cache-Control: no-cache

User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/83.0.4103.97 Safari/537.36

Upgrade: websocket

Origin: http://localhost:8200

Sec-WebSocket-Version: 13

Accept-Encoding: gzip, deflate, br

Accept-Language: en-US,en;q=0.9

Sec-WebSocket-Key: XXXXXXXXXXXXXXXXXXXXXX==

Sec-WebSocket-Extensions: permessage-deflate; client_max_window_bits

  The response headers are:

HTTP/1.1 101 Switching Protocols

Server: Daphne

Upgrade: WebSocket

Connection: Upgrade

Sec-WebSocket-Accept: XXXXXXXXXXXXXXXXXXXXXXXXXXX=

  I am using manage.py runserver command. Major packages of my pip freeze are:

aiohttp==3.6.2

aioredis==1.2.0

asgiref==3.2.9

async-timeout==3.0.1

asyncio==3.4.3

billiard==3.6.0.0

channels==2.4.0

channels-redis==2.4.0

daphne==2.3.0

Django==2.2

django-cors-headers==2.3.0

django-crequest==2018.5.11

gunicorn==19.9.0

pika==0.12.0

redis==3.2.1

tornado==5.1

Twisted==18.9.0

txaio==18.8.1

urllib3==1.24.1

    Maybe you could advice me how to find the reason why the response headers are ignored? Should I report this as a bug to channels/asgiref?

Best regards,
Albertas