2031925 - Firefox not loading pages fully if AVG Web Shield Setting Enable QUIC/HTTP3 scanning is Enabled

Status: UNCONFIRMED

(Core :: Networking, defect, P2)

Description

[Flavio Bagnato]

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:149.0) Gecko/20100101 Firefox/149.0

Steps to reproduce:

1. Left default AVG Web Shield Setting Enable QUIC/HTTP3 scanning Enabled
2. Disabled AVG Web Shield Setting Enable QUIC/HTTP3 scanning

Actual results:

1. With default AVG Web Shield Setting Enable QUIC/HTTP3 scanning Enabled some pages would not load or would not load completely, or images would not display.
2. With default AVG Web Shield Setting Enable QUIC/HTTP3 scanning Disabled Firefox runs normally loading pages, images, etc.

Expected results:

Firefox should load pages, images, etc. with AVG Web Shield Setting Enable QUIC/HTTP3 scanning Enabled

Comment 1

[Valentin Gosu [:valentin]]

Thank you for this report.
Assuming this is a recent regression in Firefox (more specifically something changed in Firefox that makes AVG block HTTP3 connections), could you help us figure out which change caused this issue by using mozregression?
https://mozilla.github.io/mozregression/quickstart.html

Comment 2

[Valentin Gosu [:valentin]]

I'm also curious if it's also happening with Firefox 150 and Firefox Nightly (152). Thanks!

Comment 3

[Flavio Bagnato]

I don't have the time to install older and nightly versions of Firefox to work out when the bug was introduced.

I can confirm that it is still happening in Firefox 150.0.1.

Comment 4

[Lars Eggert [:lars]]

mozgression (see link above) will do this (= installing versions and bisecting the failure) for you.

Comment 5

[Flavio Bagnato]

I've run mozgression from 2022-04-05 to 2026-03-23.

Bad builds:

2024-03-29
2023-09-30
2023-07-02
2023-05-18
2023-04-25
2023-04-14
2023-04-09

Good Build:
2023-04-02

I gave up after 2023-04-09

I don't see why an end user should do all this to report a bug. It is very technical and over my head a bit.

Comment 6

[Valentin Gosu [:valentin]]

Thank you for the range.
https://hg-edge.mozilla.org/mozilla-central/pushloghtml?startdate=2023-04-02&enddate=2023-04-09
I think the most likely cause is bug 1824578.

Could you give us some examples of websites that don't fully load? If they all have ECH records, that would confirm this theory.
But the fix would need to be done by AVG, as this is probably not a Firefox bug.

Comment 7

[Dennis Jackson]

For context, we had a long running rollout which enabled a fallback behavior for ECH which we recently ended because we believed CF had resolved a server-side bug.
To test if this is responsible, you can set network.dns.echconfig.fallback_to_origin_when_all_failed to true.

Alternatively, setting network.dns.http3_echconfig.enabled to false will disable ECH for HTTP3 entirely.

If this is the root cause, then AVG must be doing something quite strange to filter handshakes incorrectly.

Comment 8

[Flavio Bagnato]

@Valentin Gosu [:valentin]
https://www.reddit.com/
https://www.ebay.com.au/

Re: But the fix would need to be done by AVG, as this is probably not a Firefox bug.
Thing is the problem is not happening with Google Chrome browser so could the problem be a Firefox problem?

@Dennis Jackson
I have set network.dns.echconfig.fallback_to_origin_when_all_failed to true and will test that then if the problem still occurs I will set network.dns.http3_echconfig.enabled to false and will test that.

I will report my findings.

Comment 9

[Flavio Bagnato]

The problem still exists if network.dns.echconfig.fallback_to_origin_when_all_failed is set to true and if network.dns.http3_echconfig.enabled is set to false

Comment 10

[Dennis Jackson]

Thank you Flavio, that's really useful information, I think we can rule ECH out as a possible cause.

Comment 11

[BugBot [:suhaib / :marco]]

The severity field is not set for this bug.
:jesup, could you have a look please?

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