1483718 - Make sure tailing can be enabled without privacy.trackingprotection.lower_network_priority

Status: RESOLVED INVALID

(Core :: Networking: HTTP, defect, P1)

Description

[François Marier [:francois]]

It seems that tailing is gated by both network.http.tailing.enabled (implemented in bug 1395525): https://searchfox.org/mozilla-central/rev/5dbfd833bbb114afe758db4d4bdbc5b13bcc33ef/netwerk/base/nsChannelClassifier.cpp#244

and by privacy.trackingprotection.lower_network_priority: https://searchfox.org/mozilla-central/rev/5dbfd833bbb114afe758db4d4bdbc5b13bcc33ef/netwerk/base/nsChannelClassifier.cpp#1217

While the first pref is turned ON by default: https://searchfox.org/mozilla-central/rev/5dbfd833bbb114afe758db4d4bdbc5b13bcc33ef/modules/libpref/init/all.js#2221

the lowering of network priority is only enabled in Nightly: https://searchfox.org/mozilla-central/rev/5dbfd833bbb114afe758db4d4bdbc5b13bcc33ef/modules/libpref/init/all.js#1363-1369

The net effect of this is that tailing has only ever been turned ON in Nightly, which seems to contradict what Honza intended: https://bugzilla.mozilla.org/show_bug.cgi?id=1358060#c57

Comment 1

[François Marier [:francois]]

Attachment: Bug 1483718 - Avoid gating tailing on privacy.trackingprotection.lower_network_priority. r=mayhemer!

Comment 2

[François Marier [:francois]]

Comment on attachment 9001441 [details]
Bug 1483718 - Avoid gating tailing on privacy.trackingprotection.lower_network_priority. r=mayhemer!

Not sure why Phabricator didn't set the review flag automatically...

Comment 3

[Honza Bambas (:mayhemer)]

Francois, this is stunning and amazing catch!  This also explains why the study [1] didn't show any differences for the tailing pref as it was running only on the Beta channel.

Thanks!

[1] https://docs.google.com/document/d/1FzidX_oWru_ihiV4t5bWsfEiNcr9EONeY7rns576vjQ/

Comment 4

[Honza Bambas (:mayhemer)]

Comment on attachment 9001441 [details]
Bug 1483718 - Avoid gating tailing on privacy.trackingprotection.lower_network_priority. r=mayhemer!

(In reply to Honza Bambas (:mayhemer) from comment #3)
> Francois, this is stunning and amazing catch!  This also explains why the
> study [1] didn't show any differences for the tailing pref as it was running
> only on the Beta channel.
> 
> Thanks!
> 
> [1]
> https://docs.google.com/document/d/
> 1FzidX_oWru_ihiV4t5bWsfEiNcr9EONeY7rns576vjQ/

After looking at the patch, this is not true...  the patch deals with Throttling and not Tailing.

Also, tailing is definitely turned on by default in Beta and Release, just checked that out.

Comment 5

[François Marier [:francois]]

(In reply to Honza Bambas (:mayhemer) from comment #4)
> After looking at the patch, this is not true...  the patch deals with
> Throttling and not Tailing.

Ah, I see. I was not aware of the throttling flag (introduced in bug 1360580).

It's confusing that we have 4 different perf features (tailing, priority, throttling and FastBlock) tied to TP annotations now :) I've added it to https://wiki.mozilla.org/Security/Tracking_protection#Tracking_annotations.

Sorry for the false alarm then!