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Groups > linux.debian.kernel > #67097

Bug#960702: ethtool -m values change when output is redirected

Cross-posted to 2 groups.

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"Yannis Aribaud" <bugs@d6bell.net> writes:

> Package: ethtool
> Version: 1:4.19-1
> Severity: important
> I'm facing a very strange behavior. The command ethtool -m  report the transceiver DOM values correctly, but when the command output is redirected to an other program, values change to somthing else.

AFAICS, your SFP+ is reporting strange values in either case.  I do not
think any of these are correct.  Looking at the non-redirected one:

>  Laser output power : 3.0768 mW / 4.88 dBm

This is insanely high.

>  Receiver signal average optical power : 1.2298 mW / 0.90 dBm
>  Module temperature : 48.47 degrees C / 119.24 degrees F
>  Module voltage : 1.2336 V

Should be 3.3 V

>  Laser bias current high alarm threshold : 4.744 mA
>  Laser bias current low alarm threshold : 49.896 mA

Right...

>  Laser output power high alarm threshold : 2.5701 mW / 4.10 dBm

I don't think this can be trusted either, but I do note that it is lower
than your current output.

>  Laser output power low alarm threshold : 0.8224 mW / -0.85 dBm
>  Laser output power high warning threshold : 0.8224 mW / -0.85 dBm
>  Laser output power low warning threshold : 0.8224 mW / -0.85 dBm

Strange limits.  There are too many -0.85 dBm values here.

>  Module temperature high alarm threshold : 0.00 degrees C / 32.00 degrees F
>  Module temperature low alarm threshold : 0.00 degrees C / 32.00 degrees F
>  Module temperature high warning threshold : 0.00 degrees C / 32.00 degrees F
>  Module temperature low warning threshold : 0.00 degrees C / 32.00 degrees F

Makes no sense at all.

>  Module voltage high alarm threshold : 0.4356 V
>  Module voltage low alarm threshold : 0.0000 V
>  Module voltage high warning threshold : 0.0000 V
>  Module voltage low warning threshold : 0.0000 V

Makes even less sense.  


>  Laser rx power high alarm threshold : 0.8224 mW / -0.85 dBm
>  Laser rx power low alarm threshold : 0.8224 mW / -0.85 dBm
>  Laser rx power high warning threshold : 0.8224 mW / -0.85 dBm
>  Laser rx power low warning threshold : 0.8224 mW / -0.85 dBm

...



To me it looks like you are just reading arbitrary numbers from the
SFP+.  Try replacing it and see if the results are more reliable.



Bjørn

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Thread

Bug#960702: ethtool -m values change when output is redirected "Yannis Aribaud" <bugs@d6bell.net> - 2020-05-15 17:30 +0200
  Bug#960702: ethtool -m values change when output is redirected Bjørn Mork <bjorn@mork.no> - 2020-05-15 19:00 +0200
    Bug#960702: ethtool -m values change when output is redirected "Yannis Aribaud" <bugs@d6bell.net> - 2020-05-15 19:40 +0200
  Bug#960702: ethtool -m values change when output is redirected Ben Hutchings <ben@decadent.org.uk> - 2020-05-16 01:40 +0200
    Bug#960702: ethtool -m values change when output is redirected "Yannis Aribaud" <bugs@d6bell.net> - 2020-05-17 17:00 +0200
      Bug#960702: ethtool -m values change when output is redirected Ben Hutchings <ben@decadent.org.uk> - 2020-05-17 18:10 +0200
        Bug#960702: ethtool -m values change when output is redirected "Yannis Aribaud" <bugs@d6bell.net> - 2020-05-18 12:10 +0200
  Processed: Re: Bug#960702: ethtool -m values change when output  is redirected "Debian Bug Tracking System" <owner@bugs.debian.org> - 2020-05-16 01:40 +0200
  Processed: Re: Bug#960702: ethtool -m values change when output  is redirected "Debian Bug Tracking System" <owner@bugs.debian.org> - 2020-05-17 18:10 +0200
  Bug#960702: [PATCH net] mlx4: Fix information leak on failure to read module EEPROM Ben Hutchings <ben@decadent.org.uk> - 2020-05-17 19:30 +0200
  Bug#960702: [PATCH net] mlx4: Fix information leak on failure to read module EEPROM Ben Hutchings <ben@decadent.org.uk> - 2020-05-18 20:30 +0200

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