1874094 - Firefox would not prefer access websites via IPv6 in dual stack

Status: RESOLVED DUPLICATE of bug 1810362

(Core :: Networking, defect, P2)

Description

[0izayoimiku0]

Attachment: log.txt-main.6508.moz_log

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:121.0) Gecko/20100101 Firefox/121.0

Steps to reproduce:

Accessing any dual-stack website, such as https://test-ipv6.com

Actual results:

The Firefox will prefer to connect to IPv4 address instead of IPv6.
I tried setting network.http.fast-fallback-to-IPv4 to false, but there is no change.

Expected results:

The Firefox should prefer IPv6, not IPv4.
In the same PC, Edge works fine.

Comment 1

[0izayoimiku0]

Sorry for the missing.
The OS is Windows 11 Enterprise build 22621.3007

Comment 2

[0izayoimiku0]

Add: If enabling Firefox's built-in DoH service, it works properly.

Comment 3

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

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

Comment 4

[Valentin Gosu [:valentin] (he/him)]

(In reply to 0izayoimiku0 from comment #2)

Add: If enabling Firefox's built-in DoH service, it works properly.

I think this is caused by the order the OS resolver gives us the DNS results.
For DoH they are IPv6 first, but we don't sort the ones we get from the OS - maybe we should (with a pref).

Comment 5

[0izayoimiku0]

(In reply to Valentin Gosu [:valentin] (he/him) from comment #4)

(In reply to 0izayoimiku0 from comment #2)

Add: If enabling Firefox's built-in DoH service, it works properly.

I think this is caused by the order the OS resolver gives us the DNS results.
For DoH they are IPv6 first, but we don't sort the ones we get from the OS - maybe we should (with a pref).

It is a sharp observation. I've been thinking for a while, and it seems to be an issue caused by DNS, but I'm not clear about the specific reasons. I have also noticed this issue on Firefox Android.
Introducing a pref to control it is a wise approach. For users with specific needs, such as lighter QoS in an IPv6 environment, prioritizing IPv6 over the slight delay introduced by sorting DNS results can result in overall greater benefits.

Comment 6

[Valentin Gosu [:valentin] (he/him)]

Similarly to ⚙ D206843 Bug 1810362 - Sort the addresses in a DNS lookup result so the IPv6 ones come first. r=valentin, we should sort the IP addresses with IPv6 first, even if the OS doesn't return them sorted.
The sorting should go either here or even in the AddrInfo constructor

This should also be guarded by the network.dns.preferIPv6 pref.

Comment 7

[Sunil Mayya]

With the patch D206843 Bug 1810362 - Sort the addresses in a DNS lookup result so the IPv6 ones come first. r=valentin merged, I am no longer able to reproduce this.
I see that we pass all the tests when I use https://test-ipv6.com.

0izayoimiku0, do you still see this issue in latest firefox?
Thanks

Comment 8

[0izayoimiku0]

(In reply to Sunil Mayya from comment #7)

With the patch D206843 Bug 1810362 - Sort the addresses in a DNS lookup result so the IPv6 ones come first. r=valentin merged, I am no longer able to reproduce this.
I see that we pass all the tests when I use https://test-ipv6.com.

0izayoimiku0, do you still see this issue in latest firefox?
Thanks

Hello Mayya,
Thank you for updating. After I enabled network.dns.preferIPv6, Firefox is now working well on the IPv6 network. I believe this bug has been resolved.
Finally, please allow me to express my sincere gratitude to the development team.

Comment 9

[Sunil Mayya]

Thank you 0izayoimiku0 for your continued support in making Firefox better.
I will close this bug as resolved.