HTTP/2 protocol error

[ISSIO]

Problem Description

When visiting some websites, this error suddenly occurred today.
HTTP/2 protocol error
HTTP/2 protocol error: Invalid input ConnectionInputs.RECV_DATA in state ConnectionState.CLOSED
System Information
Mitmproxy: 12.1.1
Python: 3.12

url:
https://tools.scrapfly.io/api/fp/ja3
https://tls.browserleaks.com/json

System Information

Checklist

• This bug affects the latest mitmproxy release.

[lhb2]

I have the same issue; this causes Selenium's driver.get to time out.
Mitmproxy: 12.1.2
Python: 3.12.3
OpenSSL: OpenSSL 3.5.2 5 Aug 2025
Platform: Linux-5.15.0-151-generic-x86_64-with-glibc2.39

[sujaldev]

Refs python-hyper/h2#1181. Both of these servers seem to be sending the GOAWAY frame before sending the HEADER and DATA frame.

[AdityaPatadiya]

Hey there,
do you have any solution for this?

or else we could try
Force http/1.1
- mitmproxy --no-http2

[sujaldev]

do you have any solution for this?

Not yet (although it does work if I make some modifications to H2Connection._receive_goaway_frame, but that's more of a unreliable hack than a fix).

From what I can tell this will have to be fixed upstream first, and then we'll have to patch mitmproxy.

[AdityaPatadiya]

hey @sujaldev can you tell me which files will be helpful to fix this issue so that it will helpful to understand the project's files structure? because it's been 6 months since i left working with this project.

[sujaldev]

You could start by looking at ‎H2Connection._receive_goaway_frame to resolve python-hyper/h2#1181.

After that, on the mitmproxy side of things, it's probably going to be these two files: _http_h2.py and _http2.py.