Pulling the relevant comment for the DNS bug out:


--- Additional comment from Jiri Benc on 2020-05-28 10:59:24 CDT ---

Finally was able to install perf and get some meaningful info out of the box. (For the sake of anyone else debugging this, the key command to run after sshing to a node is 'toolbox'.)

The tx_error messages are mostly caused by 'coredns' and 'mdns-publisher' processes. They send the UDP packets directly to the genev_sys_6081 interface (likely, they send to all interfaces). Understandingly, those packets are dropped as they don't (and can't) contain the lwt metadata. This is misconfiguration of those two applications.

I'm seeing also some dropped packets sent by mld_ifc_timer_expire in the kernel. I'll look more into those.

Moved back to 4.5 to take another look.

*** Bug 1834918 has been marked as a duplicate of this bug. ***

Until this gets vendored into coredns it isn't complete.

The fix is in the coredns-mdns plugin, so I'm setting the component to "Networking" with subcomponent "mDNS".

[kni@provisionhost-0-0 ~]$ oc version
Client Version: 4.6.0-0.nightly-2020-10-02-160623
Server Version: 4.6.0-0.ci-2020-10-02-054056
Kubernetes Version: v1.19.0-rc.2.1064+1fc699e9f6becb-dirty

IPv6:
[core@master-0-0 ~]$ cat /etc/coredns/Corefile
. {
    errors
    health :18080
    mdns ocp-edge-cluster-0.qe.lab.redhat.com 0 ocp-edge-cluster-0 fd2e:6f44:5dd8::109
    forward . fe80::5054:ff:fe1e:3b18%br-ex fd2e:6f44:5dd8::1
... Output ommitted

[core@master-0-0 ~]$ ifconfig genev_sys_6081
genev_sys_6081: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 65000
        inet6 fe80::b837:95ff:fe2c:b28  prefixlen 64  scopeid 0x20<link>
        ether ba:37:95:2c:0b:28  txqueuelen 1000  (Ethernet)
        RX packets 2460982  bytes 552286598 (526.7 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 2239232  bytes 983737284 (938.1 MiB)
        TX errors 7  dropped 0 overruns 0  carrier 0  collisions 0

IPv4:
[core@master-0-0 ~]$ cat /etc/coredns/Corefile
. {
    errors
    health :18080
    mdns ocp-edge-cluster-0.qe.lab.redhat.com 0 ocp-edge-cluster-0 192.168.123.113
    forward . 192.168.123.1
...Output ommitted

[core@master-0-0 ~]$ ifconfig genev_sys_6081
genev_sys_6081: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 65000
        inet6 fe80::580e:22ff:fe27:7c0f  prefixlen 64  scopeid 0x20<link>
        ether 5a:0e:22:27:7c:0f  txqueuelen 1000  (Ethernet)
        RX packets 270685  bytes 78656649 (75.0 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 264560  bytes 109358304 (104.2 MiB)
        TX errors 7  dropped 0 overruns 0  carrier 0  collisions 0

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 4.6 GA Images), 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-2020:4196

The needinfo request[s] on this closed bug have been removed as they have been unresolved for 500 days