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Bug 1978137

Summary: ovnkube-trace requires iproute to be installed in the pod
Product: OpenShift Container Platform Reporter: Pablo Alonso Rodriguez <palonsor>
Component: NetworkingAssignee: Christoph Stäbler <cstabler>
Networking sub component: ovn-kubernetes QA Contact: Dan Brahaney <dbrahane>
Status: CLOSED ERRATA Docs Contact:
Severity: medium    
Priority: medium CC: aconstan, akaris, cstabler, dbrahane, rbrattai
Version: 4.7   
Target Milestone: ---   
Target Release: 4.9.0   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Cause: ovnkube-trace requires iproute to be installed in the source and/or destination pod because it needs to detect the interfaces link index (execs `ip -o link show`). Consequence: ovnkube-trace fails on pods without having iproute installed. Fix: Get the link index from /sys/class/net/<interface>/iflink instead of iproute. Result: ovnkube-trace does not require iproute to be installed in source and destination pods.
 Story Points: ---
Clone Of:
: 1985957 (view as bug list) Environment:
Last Closed: 2021-10-18 17:37:23 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:
Bug Depends On:    
Bug Blocks: 1985957    

Description Pablo Alonso Rodriguez 2021-07-01 08:07:19 UTC 
Description of problem:

ovnkube-trace requires iproute to be installed in order to work because it execs `ip -o link show` in it.

This essentially breaks ovnkube-trace for most use cases, as it is easier to find application pods without iproute installed than with it. Reasons include (but are not limited to):
- ubi8 images don't install iproute by default and most people don't take care to install it explicitly
- s2i builders create ubi8-based images, so s2i builds have the problem in previous points
- It becomes more and more typical to use microcontainers of different kinds, which may only include the application binary or a very small root filesystem where, again, ip binary is not available.

Not to mention than doing an exec in the application pod is not a very good practice.

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

4.7 (but it seems that 4.8 contains also the same or similar code)

How reproducible:

Always if source or destination pod don't have iproute (ip binary) installed.

Steps to Reproduce:
1. Follow https://access.redhat.com/solutions/5887511 with a source or destination pod that don't have iproute package on it
2.
3.

Actual results:

ovnkube-trace doesn't work


Expected results:

ovnkube-trace works

Additional info:

The best way to go would be to not rely on any tools installed on application container but enter the network namespace of the container.

Taking into account that ovnkube-trace already performs execs on ovnkube-node-XXX pod of the node and that the ovnkub-node-XXX pod mounts the root filesystem in /host, it should be trivial to leverage that to get the pid of the sandbox and nsenter its network namespace.
Comment 1 Christoph Stäbler 2021-07-22 14:36:19 UTC 
Bug seems to be handled by https://github.com/ovn-org/ovn-kubernetes/pull/1975 and https://github.com/ovn-org/ovn-kubernetes/pull/2308 in ovn-kubernetes upstream. Waiting for https://github.com/openshift/ovn-kubernetes/pull/618 to be merged, so fix is available downstream.
Comment 2 Christoph Stäbler 2021-07-26 06:44:07 UTC 
Fix was merged via https://github.com/openshift/ovn-kubernetes/pull/619 into ovn-kubernetes downstream (https://github.com/openshift/ovn-kubernetes/commit/b97d1a3cace41a0dd92ce2e337b0b3c8ffb1b078).
Comment 11 Dan Brahaney 2021-08-11 19:08:11 UTC 
❯ oc version
Client Version: 4.7.0-202107292319.p0.git.8b4b094.assembly.stream-8b4b094
Server Version: 4.9.0-0.nightly-2021-08-07-175228
Kubernetes Version: v1.21.1+8268f88
❯ POD=$(oc get pods -n openshift-ovn-kubernetes -l app=ovnkube-master -o name | head -1 | awk -F '/' '{print $NF}')
❯ oc cp -n openshift-ovn-kubernetes $POD:/usr/bin/ovnkube-trace ovnkube-trace
Defaulting container name to northd.
tar: Removing leading `/' from member names
❯ chmod +x ovnkube-trace
❯ ./ovnkube-trace  -dst alertmanager-main-0 -dst-namespace openshift-monitoring -src alertmanager-main-0 -src-namespace openshift-monitoring -tcp
I0811 19:04:16.998694     507 ovs.go:96] Maximum command line arguments set to: 191102
I0811 19:04:16.998848     507 ovnkube-trace.go:463] Log level set to: 0
ovn-trace indicates success from alertmanager-main-0 to alertmanager-main-0 - matched on output to "openshift-monitoring_alertmanager-main-0"
I0811 19:04:23.227740     507 ovnkube-trace.go:750] ovn-trace indicates success from alertmanager-main-0 to alertmanager-main-0 - matched on output to "openshift-monitoring_alertmanager-main-0"
ovn-trace indicates success from alertmanager-main-0 to alertmanager-main-0 - matched on output to "openshift-monitoring_alertmanager-main-0"
I0811 19:04:24.038886     507 ovnkube-trace.go:792] ovn-trace indicates success from alertmanager-main-0 to alertmanager-main-0 - matched on output to "openshift-monitoring_alertmanager-main-0"
ovs-appctl ofproto/trace indicates success from alertmanager-main-0 to alertmanager-main-0 - matched on output:15

Final flow:
I0811 19:04:24.529076     507 ovnkube-trace.go:836] ovs-appctl ofproto/trace indicates success from alertmanager-main-0 to alertmanager-main-0 - matched on output:15

Final flow:
ovs-appctl ofproto/trace indicates success from alertmanager-main-0 to alertmanager-main-0 - matched on output:15

Final flow:
I0811 19:04:25.051374     507 ovnkube-trace.go:880] ovs-appctl ofproto/trace indicates success from alertmanager-main-0 to alertmanager-main-0 - matched on output:15

Final flow:
ovn-trace command Completed normally


Everything working as expected. Marking as verified.
Comment 14 errata-xmlrpc 2021-10-18 17:37:23 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (Moderate: OpenShift Container Platform 4.9.0 bug fix and security update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHSA-2021:3759