Cause:
The fix for Bug 1953097 enabled the CoreDNS Bufsize plugin with a size of 1232 bytes. Some primitive DNS resolvers are not capable of receiving DNS response messages over UDP that are greater than 512 bytes. Note that DNS resolvers that retry lookups using TCP (such as Dig) are not affected by this bug.
Consequence:
Some DNS resolvers (such as Go's internal DNS library) are unable to receive long-winded DNS responses from openshift-dns.
Fix:
Set the CoreDNS bufsize to 512 bytes for all servers.
Result:
DNS Clients that require UDP DNS messages to not exceed 512 bytes function as expected.
Verified with 4.7.0-0.ci.test-2021-06-07-011518-ci-ln-435xggk-latest on a cluster launched by cluster-bot and passed.
$ oc get clusterversion
NAME VERSION AVAILABLE PROGRESSING SINCE STATUS
version 4.7.0-0.ci.test-2021-06-07-011518-ci-ln-435xggk-latest True False 25m Cluster version is 4.7.0-0.ci.test-2021-06-07-011518-ci-ln-435xggk-latest
$ oc -n openshift-dns get cm/dns-default -oyaml
apiVersion: v1
data:
Corefile: |
# test
mytest.ocp:5353 {
forward . 192.168.1.1
errors
bufsize 512
}
.:5353 {
bufsize 512
errors
health {
lameduck 20s
}
ready
PR has been merged into 4.7.0-0.nightly-2021-06-09-233032, moving to verified
Comment 4Miciah Dashiel Butler Masters
2021-06-11 13:42:59 UTC
*** Bug 1970889 has been marked as a duplicate of this bug. ***
Comment 8OpenShift Automated Release Tooling
2021-06-17 12:29:08 UTC
OpenShift engineering has decided to not ship Red Hat OpenShift Container Platform 4.7.17 due a regression https://bugzilla.redhat.com/show_bug.cgi?id=1973006. All the fixes which were part of 4.7.17 will be now part of 4.7.18 and planned to be available in candidate channel on June 23 2021 and in fast channel on June 28th.
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 (OpenShift Container Platform 4.7.18 bug fix 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/RHBA-2021:2502
Verified with 4.7.0-0.ci.test-2021-06-07-011518-ci-ln-435xggk-latest on a cluster launched by cluster-bot and passed. $ oc get clusterversion NAME VERSION AVAILABLE PROGRESSING SINCE STATUS version 4.7.0-0.ci.test-2021-06-07-011518-ci-ln-435xggk-latest True False 25m Cluster version is 4.7.0-0.ci.test-2021-06-07-011518-ci-ln-435xggk-latest $ oc -n openshift-dns get cm/dns-default -oyaml apiVersion: v1 data: Corefile: | # test mytest.ocp:5353 { forward . 192.168.1.1 errors bufsize 512 } .:5353 { bufsize 512 errors health { lameduck 20s } ready