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.
Here is a transcript: root@localhost:~# ethtool -m enp10s0; echo -e 'nnn'; ethtool -m enp10s0 | cat Identifier : 0x03 (SFP) Extended identifier : 0x04 (GBIC/SFP defined by 2-wire interface ID) Connector : 0x07 (LC) Transceiver codes : 0x10 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 Transceiver type : 10G Ethernet: 10G Base-SR Encoding : 0x06 (64B/66B) BR, Nominal : 10300MBd Rate identifier : 0x00 (unspecified) Length (SMF,km) : 0km Length (SMF) : 0m Length (50um) : 80m Length (62.5um) : 20m Length (Copper) : 0m Length (OM3) : 300m Laser wavelength : 850nm Vendor name : Pureoptics Vendor OUI : 00:00:00 Vendor PN : EX-SFP-10GE-SR Vendor rev : B4 Option values : 0x00 0x1a Option : RX_LOS implemented Option : TX_FAULT implemented Option : TX_DISABLE implemented BR margin, max : 0% BR margin, min : 0% Vendor SN : M4351243 Date code : 190515 Optical diagnostics support : Yes Laser bias current : 16.480 mA Laser output power : 3.0768 mW / 4.88 dBm 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 Alarm/warning flags implemented : Yes Laser bias current high alarm : Off Laser bias current low alarm : Off Laser bias current high warning : Off Laser bias current low warning : Off Laser output power high alarm : Off Laser output power low alarm : Off Laser output power high warning : Off Laser output power low warning : Off Module temperature high alarm : Off Module temperature low alarm : Off Module temperature high warning : Off Module temperature low warning : Off Module voltage high alarm : Off Module voltage low alarm : Off Module voltage high warning : Off Module voltage low warning : Off Laser rx power high alarm : Off Laser rx power low alarm : Off Laser rx power high warning : Off Laser rx power low warning : Off Laser bias current high alarm threshold : 4.744 mA Laser bias current low alarm threshold : 49.896 mA Laser bias current high warning threshold : 51.776 mA Laser bias current low warning threshold : 50.910 mA Laser output power high alarm threshold : 2.5701 mW / 4.10 dBm 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 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 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 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 Identifier : 0x03 (SFP) Extended identifier : 0x04 (GBIC/SFP defined by 2-wire interface ID) Connector : 0x07 (LC) Transceiver codes : 0x10 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 Transceiver type : 10G Ethernet: 10G Base-SR Encoding : 0x06 (64B/66B) BR, Nominal : 10300MBd Rate identifier : 0x00 (unspecified) Length (SMF,km) : 0km Length (SMF) : 0m Length (50um) : 80m Length (62.5um) : 20m Length (Copper) : 0m Length (OM3) : 300m Laser wavelength : 850nm Vendor name : Pureoptics Vendor OUI : 00:00:00 Vendor PN : EX-SFP-10GE-SR Vendor rev : B4 Option values : 0x00 0x1a Option : RX_LOS implemented Option : TX_FAULT implemented Option : TX_DISABLE implemented BR margin, max : 0% BR margin, min : 0% Vendor SN : M4351243 Date code : 190515 Optical diagnostics support : Yes Laser bias current : 16.448 mA Laser output power : 0.8224 mW / -0.85 dBm Receiver signal average optical power : 0.8224 mW / -0.85 dBm Module temperature : 32.12 degrees C / 89.83 degrees F Module voltage : 0.8224 V Alarm/warning flags implemented : Yes Laser bias current high alarm : Off Laser bias current low alarm : Off Laser bias current high warning : Off Laser bias current low warning : Off Laser output power high alarm : Off Laser output power low alarm : Off Laser output power high warning : Off Laser output power low warning : Off Module temperature high alarm : Off Module temperature low alarm : Off Module temperature high warning : Off Module temperature low warning : Off Module voltage high alarm : On Module voltage low alarm : Off Module voltage high warning : On Module voltage low warning : Off Laser rx power high alarm : Off Laser rx power low alarm : Off Laser rx power high warning : Off Laser rx power low warning : Off Laser bias current high alarm threshold : 4.754 mA Laser bias current low alarm threshold : 51.402 mA Laser bias current high warning threshold : 56.552 mA Laser bias current low warning threshold : 53.964 mA Laser output power high alarm threshold : 2.6981 mW / 4.31 dBm Laser output power low alarm threshold : 2.9216 mW / 4.66 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 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 Module voltage high alarm threshold : 0.4368 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 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 As you can see alsmost all mesuring values (C, V, mA and dBm) change. The values when output is redirected are unreliable which makes it impossible to use in a script. I am using Debian GNU/Linux 10 (buster), kernel 4.19.0-9-amd64 #1 SMP Debian 4.19.118-2 (2020-04-29) x86_64 GNU/Linux and libc6 2.28-10 FYI, I could not reproduce the bug on Debian Stretch (ethtool 1:4.7-1+b1, kernel 4.9.0-11-amd64 and libc6 2.24-11+deb9u4). -- Yannis Aribaud
