Description of problem: 

Running Uperf UDP workload from pod to pod across worker is dropping packets and seemed to be dropping because of packet fragmentation. 

UDP packets fragmenting when the payload size is greater than MTU size. If protocol is set to TCP we don't see any packet drop or fragmentation. 


Version-Release number of selected component (if applicable): 
OCP: 4.7.0-fc.5
Kernel version: 4.18.0-240.10.1.el8_3.x86_64
OVN version: 
Version: 0.3.0
Git commit: bc8321aa1afb6b532e73effc0d2bd3212c15a85e
Git branch: rhaos-4.7-rhel-8
Go version: go1.15.5
Build date: 2021-01-30
OS/Arch: linux amd64

OVS version:
$ ovs-vsctl --version
ovs-vsctl (Open vSwitch) 2.13.2
DB Schema 8.2.0

How reproducible:
Frequently on any environment

Steps to Reproduce:
1. Install OCP cluster 4.7.0-fc.5
2. Run UPerf workload (We are using benchmark-operator)
3. UDP protocol and Payload size more than MTU

Actual results:
Packets fragmenting and RX drops at the NIC level

Expected results:
No Fragmentation and no drops as in TCP 

Additional info:
$ ethtool -i ens2f1
driver: i40e
version: 2.8.20-k
firmware-version: 7.10 0x800051ac 19.0.12
expansion-rom-version: 
bus-info: 0000:62:00.1
supports-statistics: yes
supports-test: yes
supports-eeprom-access: yes
supports-register-dump: yes
supports-priv-flags: yes

Cluster network:
status:
  clusterNetwork:
  - cidr: 10.128.0.0/14
    hostPrefix: 23
  clusterNetworkMTU: 8900
  networkType: OVNKubernetes
  serviceNetwork:
  - 172.30.0.0/16

$ ifconfig ens2f1
ens2f1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 9000
        ether 40:a6:b7:00:47:81  txqueuelen 1000  (Ethernet)
        RX packets 752005677  bytes 5000469924153 (4.5 TiB)
        RX errors 0  dropped 83514476  overruns 0  frame 0
        TX packets 156543237  bytes 621736118212 (579.0 GiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

$ ethtool -k ens2f1
Features for ens2f1:
rx-checksumming: on
tx-checksumming: on
	tx-checksum-ipv4: on
	tx-checksum-ip-generic: off [fixed]
	tx-checksum-ipv6: on
	tx-checksum-fcoe-crc: off [fixed]
	tx-checksum-sctp: on
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-tcp-mangleid-segmentation: off
	tx-tcp6-segmentation: on
generic-segmentation-offload: on
generic-receive-offload: on
large-receive-offload: off [fixed]
rx-vlan-offload: on
tx-vlan-offload: on
ntuple-filters: on
receive-hashing: on
highdma: on
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: on
tx-gre-csum-segmentation: on
tx-ipxip4-segmentation: on
tx-ipxip6-segmentation: on
tx-udp_tnl-segmentation: on
tx-udp_tnl-csum-segmentation: on
tx-gso-partial: on
tx-sctp-segmentation: off [fixed]
tx-esp-segmentation: off [fixed]
tx-udp-segmentation: on
tls-hw-rx-offload: 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]
l2-fwd-offload: off
hw-tc-offload: on
esp-hw-offload: off [fixed]
esp-tx-csum-hw-offload: off [fixed]
rx-udp_tunnel-port-offload: on
tls-hw-tx-offload: off [fixed]
rx-gro-hw: off [fixed]
tls-hw-record: off [fixed]