Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

troubleshooting.md: add ethtool -K flannel.1 tx-checksum-ip-generic off for NAT #1929

Merged
merged 1 commit into from
Apr 24, 2024
Merged

troubleshooting.md: add ethtool -K flannel.1 tx-checksum-ip-generic off for NAT #1929

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
3 changes: 2 additions & 1 deletion Documentation/kubernetes.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -32,7 +32,8 @@ Other options include [Kyverno](https://kyverno.io/policies/pod-security/) and [
# Annotations

* `flannel.alpha.coreos.com/public-ip`, `flannel.alpha.coreos.com/public-ipv6`: Define the used public IP of the node. If configured when Flannel starts it'll be used as the `public-ip` and `public-ipv6` flag.
* `flannel.alpha.coreos.com/public-ip-overwrite`, `flannel.alpha.coreos.com/public-ipv6-overwrite`: Allows to overwrite the public IP of a node. Useful if the public IP can not determined from the node, e.G. because it is behind a NAT. It can be automatically set to a nodes `ExternalIP` using the [flannel-node-annotator](https://github.com/alvaroaleman/flannel-node-annotator)
* `flannel.alpha.coreos.com/public-ip-overwrite`, `flannel.alpha.coreos.com/public-ipv6-overwrite`: Allows to overwrite the public IP of a node. Useful if the public IP can not determined from the node, e.G. because it is behind a NAT. It can be automatically set to a nodes `ExternalIP` using the [flannel-node-annotator](https://github.com/alvaroaleman/flannel-node-annotator).
See also the "NAT" section in [troubleshooting](./troubleshooting.md) if UDP checksums seem corrupted.

## Older versions of Kubernetes

Expand Down
21 changes: 21 additions & 0 deletions Documentation/troubleshooting.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -39,6 +39,27 @@ Vagrant typically assigns two interfaces to all VMs. The first, for which all ho

This may lead to problems with flannel. By default, flannel selects the first interface on a host. This leads to all hosts thinking they have the same public IP address. To prevent this issue, pass the `--iface=eth1` flag to flannel so that the second interface is chosen.

## NAT
When the public IP is behind NAT, the UDP checksum fields of the VXLAN packets can be corrupted.
In that case, try running the following commands to avoid corrupted checksums:

```bash
/usr/sbin/ethtool -K flannel.1 tx-checksum-ip-generic off
```

To automate the command above via udev, create `/etc/udev/rules.d/90-flannel.rules` as follows:

```
SUBSYSTEM=="net", ACTION=="add|change|move", ENV{INTERFACE}=="flannel.1", RUN+="/usr/sbin/ethtool -K flannel.1 tx-checksum-ip-generic off"
```

<!--
ref:
- https://github.com/flannel-io/flannel/issues/1279
- https://github.com/kubernetes/kops/pull/9074
- https://github.com/karmab/kcli/commit/b1a8eff658d17cf4e28162f0fa2c8b2b10e5ad00
-->

## Permissions
Depending on the backend being used, flannel may need to run with super user permissions. Examples include creating VXLAN devices or programming routes. If you see errors similar to the following, confirm that the user running flannel has the right permissions (or try running with `sudo)`.
* `Error adding route...`
Expand Down
Loading