Bug 1434236

Summary:	ethtool returns incorrect exit code for error (stderr)
Product:	Red Hat Enterprise Linux 7	Reporter:	Vikram Hosakote <vhosakot>
Component:	ethtool	Assignee:	Ivan Vecera <ivecera>
Status:	CLOSED NOTABUG	QA Contact:	BaseOS QE - Apps <qe-baseos-apps>
Severity:	medium	Docs Contact:
Priority:	unspecified
Version:	7.2	CC:	bnater, linville
Target Milestone:	rc	Keywords:	Reopened
Target Release:	---
Hardware:	x86_64
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2017-11-03 18:48:14 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Vikram Hosakote 2017-03-21 03:28:15 UTC

Description of problem:
=======================

ethtool returns an incorrect exit code (0 which is success) when it fails with an error (stderr). When ethtool fails with an error (stderr), it must return a non-zero exit code instead of 0.

Since orchestration tools like Ansible takes action based on the value of the exit code return by a command, due to this bug, Ansible thinks that ethtool worked/passed when ethtool actually fails with an error (stderr). Fixing this bug will make orchestration tools like Ansible to take proper action based on the correct non-zero exit code returned for an error (stderr).

Version-Release number of selected component (if applicable):
=============================================================

# ethtool --version
ethtool version 3.15

How reproducible:
=================

Always.

Steps to Reproduce:
===================

# /usr/sbin/ethtool -K eth0 lro off > output
Cannot change large-receive-offload

# cat output
#

# /usr/sbin/ethtool -K eth0 lro off 2> output

# cat output 
Cannot change large-receive-offload

# /usr/sbin/ethtool -K eth0 lro off
Cannot change large-receive-offload

# echo $?
0

Actual results:
===============

# /usr/sbin/ethtool -K eth0 lro off
Cannot change large-receive-offload

# echo $?
0

Expected results:
=================

ethtool must return a non-zero exit code for an error (stderr) instead of 0.

# /usr/sbin/ethtool -K eth0 lro off
Cannot change large-receive-offload

# echo $?
127 (or any other non-zero exit code)

Additional info:
================

# cat /etc/redhat-release 
Red Hat Enterprise Linux Server release 7.2 (Maipo)

# uname -r
3.10.0-327.el7.x86_64

# uname -a
Linux testnode.in 3.10.0-327.el7.x86_64 #1 SMP Thu Oct 29 17:29:29 EDT 2015 x86_64 x86_64 x86_64 GNU/Linux

# cat /etc/system-release-cpe 
cpe:/o:redhat:enterprise_linux:7.2:ga:server

Comment 2 Ivan Vecera 2017-05-22 14:36:06 UTC

Could you please provide an output from 'ethtool -k eth0' ? You are probably trying to change fixed (non-changeable) offloaded feature.

Comment 3 Vikram Hosakote 2017-05-22 17:53:50 UTC

Below is the output of "ethtool -k eth0".

# ethtool -k eth0
Features for eth0:
rx-checksumming: on [fixed]
tx-checksumming: on
	tx-checksum-ipv4: off [fixed]
	tx-checksum-ip-generic: on
	tx-checksum-ipv6: off [fixed]
	tx-checksum-fcoe-crc: off [fixed]
	tx-checksum-sctp: off [fixed]
scatter-gather: on
	tx-scatter-gather: on
	tx-scatter-gather-fraglist: off [fixed]
tcp-segmentation-offload: on
	tx-tcp-segmentation: on
	tx-tcp-ecn-segmentation: on
	tx-tcp6-segmentation: on
udp-fragmentation-offload: on
generic-segmentation-offload: on
generic-receive-offload: off
large-receive-offload: off [fixed]
rx-vlan-offload: off [fixed]
tx-vlan-offload: off [fixed]
ntuple-filters: off [fixed]
receive-hashing: off [fixed]
highdma: on [fixed]
rx-vlan-filter: on [fixed]
vlan-challenged: off [fixed]
tx-lockless: off [fixed]
netns-local: off [fixed]
tx-gso-robust: off [fixed]
tx-fcoe-segmentation: off [fixed]
tx-gre-segmentation: off [fixed]
tx-ipip-segmentation: off [fixed]
tx-sit-segmentation: off [fixed]
tx-udp_tnl-segmentation: off [fixed]
tx-mpls-segmentation: off [fixed]
fcoe-mtu: off [fixed]
tx-nocache-copy: off
loopback: off [fixed]
rx-fcs: off [fixed]
rx-all: off [fixed]
tx-vlan-stag-hw-insert: off [fixed]
rx-vlan-stag-hw-parse: off [fixed]
rx-vlan-stag-filter: off [fixed]
busy-poll: off [fixed]

Comment 4 Ivan Vecera 2017-05-23 07:12:51 UTC

(In reply to Vikram Hosakote from comment #3)
> Below is the output of "ethtool -k eth0".
> 
> # ethtool -k eth0
> ...
> large-receive-offload: off [fixed]
> ...

So you are trying to enable fixed feature (LRO in your case)... It is not possible to change such features so ethtool just informs about it... This is not an error.

Comment 5 Vikram Hosakote 2017-05-23 18:51:42 UTC

Then, why does ethtool print the output in stderr and return 0 (which is success)?

Comment 7 Ivan Vecera 2017-11-03 18:48:14 UTC

(In reply to Vikram Hosakote from comment #5)
> Then, why does ethtool print the output in stderr and return 0 (which is
> success)?

It's upstream behavior... please see commit like 5954d26 ("ethtool: Do not return error code if no changes were attempted"). This commit changes the return code when channel parameters were not changed... it returned non-zero but now zero although prints the message to stderr.

If we change this behavior we could break existing scripts that assumes such messages on stderr output.

...and return zero is valid because an attempt to change fixed parameter is not an error state but a mistake of the user.