Bug 1457062 - Docker MTU is wrong when SDN is adjusted to smaller MTU
Summary: Docker MTU is wrong when SDN is adjusted to smaller MTU
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: OpenShift Container Platform
Classification: Red Hat
Component: Installer
Version: 3.6.0
Hardware: x86_64
OS: Linux
unspecified
high
Target Milestone: ---
: ---
Assignee: Scott Dodson
QA Contact: Johnny Liu
URL:
Whiteboard:
Depends On:
Blocks: 1460233 1460235
TreeView+ depends on / blocked
 
Reported: 2017-05-31 04:01 UTC by Øystein Bedin
Modified: 2017-08-16 19:51 UTC (History)
4 users (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Starting with OCP 3.4, OpenShift's SDN plugins no longer reconfigure the docker bridge MTU, rather pods are configured properly on creation. Because of this change, non-OpenShift containers may have an MTU configured that is too large to allow access to hosts on the SDN. The installer has been updated to align the MTU setting for the docker bridge with the MTU used inside the cluster, thus avoiding the problem.
Clone Of:
: 1460233 1460235 (view as bug list)
Environment:
Last Closed: 2017-08-10 05:26:47 UTC
Target Upstream Version:
Embargoed:


Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHEA-2017:1716 0 normal SHIPPED_LIVE Red Hat OpenShift Container Platform 3.6 RPM Release Advisory 2017-08-10 09:02:50 UTC

Description Øystein Bedin 2017-05-31 04:01:46 UTC
Description of problem:
When the OpenShift SDN is smaller than "default", the docker MTU also needs to be adjusted.

Version-Release number of selected component (if applicable):
Found doing a build with the latest OpenShift 3.5

How reproducible:
100%

Steps to Reproduce:
1. Install OpenShift in env where the MTU of the SDN will be adjusted down, e.g.: in an OpenStack environment
2. Observe how some builds are failing, e.g.: a DockerStrategy build with the following source: https://github.com/oybed/test-network
3. Change the docker mtu (add '--mtu=1400' to the /etc/sysconfig/docker-network file) and observe the builds are passing.

Actual results:
Failed builds due to incorrect MTU setting for docker

Expected results:
The installation should have set the docker MTU (just like it does for the SDN) 

Additional info:

Comment 1 Scott Dodson 2017-05-31 21:21:32 UTC
Proposed fix https://github.com/openshift/openshift-ansible/pull/4336

Comment 2 Scott Dodson 2017-06-05 15:37:44 UTC
Merged into 3.6, I'll backport to 3.3 - 3.5 once QE verifies this bug.

Comment 3 Scott Dodson 2017-06-05 15:38:38 UTC
Or 3.4 and 3.5. This change isn't necessary in 3.3 as we reconfigured docker back in the dark ages.

Comment 5 Johnny Liu 2017-06-09 09:35:02 UTC
Verified this bug with openshift-ansible-3.6.98-1.git.0.e651d65.el7.noarch, and PASS.
# cat /etc/sysconfig/docker-network 
# /etc/sysconfig/docker-network
DOCKER_NETWORK_OPTIONS=' --mtu=1350'

# grep -i mtu /etc/origin/node/node-config.yaml 
   mtu: 1350

# oc new-app https://github.com/oybed/test-network -n install-test

# oc get build -n install-test
NAME                       TYPE      FROM          STATUS     STARTED          DURATION
test-network-1             Docker    Git@71c648f   Complete   51 seconds ago   20s

Comment 7 errata-xmlrpc 2017-08-10 05:26:47 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, 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/RHEA-2017:1716


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