Your flag: enable-async-dns is expiring in M81

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sriniv...@google.com

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Jan 17, 2020, 4:21:37 PM1/17/20
to eric...@chromium.org, net...@chromium.org

Hi,

Your flag: enable-async-dns expired in M81

In M81 we will begin hiding from the Chrome UI (and eventually removing) flags that are marked as expired in flag-metadata.json

This is in accordance with the process documented in //docs/flag_expiry.md . You are receiving this email because you are listed as the owner of a flag that will begin expiring in M81, or because you are a PM who might need visibility into this process.In M81, we will hide flags that expired as of M81 or earlier from chrome://flags. From this point onward, every subsequent release will hide flags that expired as of that release.

What you need to do for M81 (before the branch date Jan 30 2020):

1. Look at the list of flags marked as expiring in M81 or earlier. The authoritative source for this list is the list_flags.py tool

tools/flags/list_flags.py --expired-by 81

The current list of expiring flags (as of @r714913) is captured in this document

2. If you see a flag listed as expiring that you want to keep, create a CL updating //chrome/browser/flag-metadata.json with an appropriate new expiration milestone. If you do this before the M81 branch you're all set; if you do it after the M81 branch you'll need to merge that CL to the M81 branch as well.

Flags expiring in M81 as of @r714913

Thanks,

Srinivas

Eric Orth

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Jan 17, 2020, 4:42:14 PM1/17/20
to net-dev
I'm inclined to let this expire.  Anybody want to argue otherwise?

Looks like this just allows disabling the built-in DNS resolver on Android.  Did some searching for the flag to see what people might rely on this for, and all I can find is a bunch of forums telling people to disable it to stop preconnect (which is unrelated to this flag).  Note that this flag only affects non-DoH use of the built-in resolver.

Brad Lassey

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Jan 17, 2020, 4:56:02 PM1/17/20
to Eric Orth, net-dev
Will it default to enabled if we let it expire?

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Eric Orth

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Jan 17, 2020, 5:00:23 PM1/17/20
to Brad Lassey, net-dev
My understanding is only the flag is expiring, not the feature itself that it manipulates.  So only the ability to change it on chrome://flags is going away.  The feature itself (features::kAsyncDns) is still there and still enabled by default (for CrOS, Mac, and Android).

Kaustubha Govind

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Jan 20, 2020, 11:09:42 AM1/20/20
to Eric Orth, Brad Lassey, net-dev
There are some public forums that refer to this flag: https://www.xda-developers.com/fix-dns-ad-blocker-chrome/

Would the workaround be to update their Chrome shortcut to use the command-line flag instead?

Eric Orth

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Jan 21, 2020, 1:30:05 PM1/21/20
to Kaustubha Govind, Brad Lassey, net-dev
"which aims to speed up page loading times by resolving the IP address of a website before you click the link. It works by scanning a web page as it loads, finding any domain names linked and using a Domain Name Server (DNS) to find the IP address associated with each of them"

I don't think that page has any clue what they're talking about since what they're trying to disable has nothing to do with async resolver.  Also, the only comment on that page more recent than 2 years old is complaining that the flag no longer works for whatever it is they're trying to fix.

We can't indefinitely support every Chrome flag that anybody on the internet has found might or might not be related to making an ill-defined problem go away.  I know of no specific bug that would be worked around by setting this flag on Android, so I'm not going to support it as a workaround for anything.   If there is an actual issue, they need to report it to us (here on net-dev@ or better through a bug report) so we can investigate and either fix or provide a workaround.

David Benjamin

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Jan 21, 2020, 2:45:41 PM1/21/20
to Eric Orth, Kaustubha Govind, Brad Lassey, net-dev
Right, Chrome command-line flags in general are not supported long-term UI surface like that. They can be temporary workarounds when features cause issues, but the key word here is temporary. The root problems should get fixed.

(If I recall correctly, the issue on that page was that the async resolver wasn't detecting some configurations correctly on some Android versions, which was fixed in https://crbug.com/805020.)

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