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disable GSO and ECN on kernels older than version 5 #4456

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merged 1 commit into from
Apr 24, 2024
Merged

disable GSO and ECN on kernels older than version 5 #4456

merged 1 commit into from
Apr 24, 2024

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marten-seemann
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Fixes #4396. Fixes #4178. Fixes #4446. Closes #4447.

I'm tired of the constant stream of issues with ECN and GSO. These things should just work. These are always very hard to reproduce, and mostly due to some old buggy kernel implementation that has been fixed for years, but is still out there in the wild, with no hope of ever getting updated.

New approach: disable ECN and GSO on all old (before version 5) kernels. This has some false positives, but if somebody is running such an ancient kernel, they probably don't care that much about performance anyway.

cc @heixiaoma @tobyxdd @requilence @arashpayan @ainar-g

@marten-seemann marten-seemann force-pushed the screw-old-kernels branch 3 times, most recently from 689e9d3 to 30d7981 Compare April 23, 2024 15:38
ainar-g
ainar-g reviewed Apr 23, 2024
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Would you like us to try and release an edge build of AdGuard Home with quic-go from this branch? As far as I can see, there are minor API changes as well.

sys_conn_helper_linux.go Outdated Show resolved Hide resolved
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codecov bot commented Apr 23, 2024 •
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Codecov Report

Attention: Patch coverage is 82.75862% with 5 lines in your changes are missing coverage. Please review.

Project coverage is 84.67%. Comparing base (6a4512a) to head (7135257).
Report is 2 commits behind head on master.

Files Patch % Lines
sys_conn_helper_linux.go 84.00% 2 Missing and 2 partials ⚠️
sys_conn_oob.go 75.00% 1 Missing ⚠️
Additional details and impacted files 
@@            Coverage Diff             @@
##           master    #4456      +/-   ##
==========================================
+ Coverage   84.65%   84.67%   +0.02%     
==========================================
  Files         152      152              
  Lines       14419    14443      +24     
==========================================
+ Hits        12206    12229      +23     
+ Misses       1707     1706       -1     
- Partials      506      508       +2

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

@marten-seemann marten-seemann force-pushed the screw-old-kernels branch 2 times, most recently from 4dbc8ad to 6257f2b Compare April 23, 2024 15:46
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Would you like us to try and release an edge build of AdGuard Home with quic-go from this branch? As far as I can see, there are minor API changes as well.

@ainar-g Yes, would be great to see if this actually resolves the problem.

@ainar-g ainar-g mentioned this pull request Apr 23, 2024
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ainar-g commented Apr 23, 2024

@marten-seemann, I've discovered #4457 while testing, and it seems to be a blocker for us, unfortunately. Feel free to wait for feedback from others or merge as-is.

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@marten-seemann, I've discovered #4457 while testing, and it seems to be a blocker for us, unfortunately. Feel free to wait for feedback from others or merge as-is.

Fixed in #4458, and rebased this PR. Can you give it another try please?

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I think this is a great idea. I'd personally take it a step further and disable it on anything older than 5.4, 5.10 or even 5.15 which are all LTS releases. 5.0 was EOL in 2019.

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tobyxdd commented Apr 24, 2024

I have no problem with this, but don't we know the exact versions that added the support for these features? For example, for #4396 it's 4.9.

It's too shotgun to disable it on anything older than 5.0 imo

@marten-seemann
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I have no problem with this, but don't we know the exact versions that added the support for these features? For example, for #4396 it's 4.9.

@tobyxdd We could, but it seems like the initial implementations of both GSO and ECN contained bugs that were fixed in later (patch?) releases. Can't really fault the Linux maintainers for that, but the problem is that the update cycles are extremely long in the wild, and we still end up running on those systems years later from time to time.

I think this is a great idea. I'd personally take it a step further and disable it on anything older than 5.4, 5.10 or even 5.15 which are all LTS releases. 5.0 was EOL in 2019.

@arashpayan Are you aware of any problems in older 5.x releases? The intent here is not to punish people for using outdated software. I just don't want to cause people problems when they run quic-go there.

sukunrt
sukunrt approved these changes Apr 24, 2024
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sys_conn_oob.go Outdated Show resolved Hide resolved
sys_conn_helper_darwin.go
func isGSOSupported(syscall.RawConn) bool { return false }
func isGSOEnabled(syscall.RawConn) bool { return false }

func isECNEnabled() bool { return !isECNDisabledUsingEnv() }
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Do we need to disable it for older macos versions too?

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I haven’t heard any complaints about macOS. Let’s wait and see?

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requilence commented Apr 24, 2024 •
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The GSO control message was introduced in kernel version 4.18. According to my observations, many Android devices still use the 4.19 kernel. Additionally, Google still supports upgrading devices with the 4.19 kernel to the latest Android 14. However, I haven't found any public data on the distribution of Android kernels in the wild.

At the same time, I observed cases when using GSO on android kernels which actually doesn't support it caused total stream stuck. It's much more critical than enhancing a performance with this optimisation. So, at the end, I think disabling GSO on kernels older than 5.0 in the quic-go library totally makes sense, as the Linux kernel repo contains numerous fixes for GSO between 4.18 and 5.0.

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Thanks for all the input here everyone!

@marten-seemann marten-seemann merged commit 12aa638 into master Apr 24, 2024
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bt90 commented Apr 24, 2024

According to my observations, many Android devices still use the 4.19 kernel.

Depending on the manufacturer, the switch to the 5.x kernel only happened on devices that launched with Android 11 or 12. So if the device is older than ~2 years, chances are it's still running the 4.x kernel.

image

Source: https://source.android.com/docs/core/architecture/kernel/android-common#feature-and-launch-kernels

That said, blocking GSO/ECN on anything pre 5.x is still the right call. quic-go can't and shouldn't try to unfuck the Android ecosystem.

@marten-seemann marten-seemann deleted the screw-old-kernels branch April 25, 2024 08:12
@bt90 bt90 mentioned this pull request Apr 27, 2024
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@sukunrt sukunrt sukunrt approved these changes

@MarcoPolo MarcoPolo Awaiting requested review from MarcoPolo

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