1997737 - Page loading hangs when UDP 443 is blocked

Status: UNCONFIRMED

(Core :: Networking: HTTP, defect, P2)

Description

[Sergey Fionov]

Steps to reproduce:

Some sites which support HTTP/3 have problems loading a part of requests in Windows version of Firefox, when UDP 443 is blocked (packets dropped).

The following steps are for Windows virtual machine and macOS host:

1. In Windows virtual machine, open Firefox and load https://discord.com/ , make sure it loads correctly.
2. On host macOS machine, add block drop out proto udp from any to any port = 443 to the end of /etc/pf.conf.
3. Reload firewall: pfctl -f /etc/pf.conf
4. Enable firewall: pfctl -e . It can be disabled later by calling pfctl -d.
5. In Windows virtual machine, open Firefox and load https://discord.com/ . Reopen firefox before every try.

Cleanup steps (after all tests): remove rule from /etc/pf.conf and reload firewall again.

Actual results:

1 of 5 times page loading will hang - some resource requests due to some reason are tried via unestablished HTTP/3, then, after 20-30s, they are completed via existing HTTP/2 connection.

Another strange thing that I see on Firefox for Windows - about:networking shows some HTTP/3 connections even when UDP 443 is blocked.

Reproducible on Windows version in stable, beta and nightly channels.
Not reproducible on Firefox for Mac, so I believe this is related to the Windows implementation.

Expected results:

Page loading does not hang, as in Firefox for Mac.

Comment 1

[BugBot [:suhaib / :marco/ :calixte]]

The Bugbug bot thinks this bug should belong to the 'Core::Networking: HTTP' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.