Warning: UDP GRO forwarding is suboptimally configured...

[brkdncr]

Warning: UDP GRO forwarding is suboptimally configured on eth0, UDP forwarding throughput capability will increase with a configuration change. See https://tailscale.com/s/ethtool-config-udp-gro

This might resolve the warning message:
https://www.reddit.com/r/Tailscale/comments/18qzf9f/comment/kf0sha4/

Note that many of these commands should be done with elevated privileges through the use of sudo. Either append sudo to each command or get an interactive shell with sudo -s.

Also, this might not work for every system. This comment here shows how to best do this for TrueNas Scale. As with many things for Linux, there are many ways to skin the cat. But don't do that, reddit loves cats.

First, create a service file named udpgroforwarding.service. I'm hard coding my interface just like you as it's the only one that's ever going to have a default route outbound.

[Unit] 
Description= UDPGroForwarding 
Wants=network-online.target 
After=network-online.target

[Service] 
Type=oneshot 
ExecStart=/sbin/ethtool -K wan0 rx-udp-gro-forwarding on rx-gro-list off

[Install] 
WantedBy=multi-user.target

Those looking at this from the future can get their interface by:

ip -o route get 8.8.8.8 | cut -f 5 -d " "
2. Copy the file over to /etc/systemd/system

cp udpgroforwarding.service /etc/systemd/system
3. Reload the systemd daemon

systemctl daemon-reload
4. Start the service to make sure it works

systemctl start udpgroforwarding
5. enable the service

`systemctl enable udpgroforwarding``
6. Reboot

7. Verify the changes took place (replacing wan0 with your appropriate interface):

ethtool -k wan0 | egrep "(gro-list|forwarding)"
rx-gro-list: off
rx-udp-gro-forwarding: on`