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fix: fall back to nftables kube-proxy on ip_tables-less kernels #5567

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fix: fall back to nftables kube-proxy on ip_tables-less kernels #5567

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10 changes: 10 additions & 0 deletions microk8s-resources/wrappers/run-kubelite-with-args
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Original file line number Diff line number Diff line change
Expand Up @@ -73,6 +73,16 @@ else
sanitise_args_kube_controller_manager
fi

# Fall back to kube-proxy nftables mode on kernels that do not ship the
# ip_tables module. This avoids a silent crash loop on nftables-only hosts
# (see canonical/microk8s#5525) while preserving any user-selected proxy-mode.
if ! grep -qE '^--proxy-mode[= ]' "$SNAP_DATA/args/kube-proxy" &&
! (/sbin/modprobe -n -q ip_tables &> /dev/null || modprobe -n -q ip_tables &> /dev/null)
then
echo "ip_tables kernel module is unavailable; configuring kube-proxy to use nftables mode."
refresh_opt_in_local_config "proxy-mode" "nftables" kube-proxy
fi

## Kubelet configuration
pod_cidr="$(cat $SNAP_DATA/args/kube-proxy | grep "cluster-cidr" | tr "=" " "| gawk '{print $2}')"
if [ -z "$pod_cidr" ]
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7 changes: 7 additions & 0 deletions scripts/inspect.sh
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Expand Up @@ -212,6 +212,13 @@ function suggest_fixes {
fi
fi

if journalctl -n 50 -u snap.microk8s.daemon-kubelite 2>/dev/null | grep -q 'Module ip_tables not found'
then
printf -- '\033[0;33m WARNING: \033[0m Your kernel does not provide the ip_tables module.\n'
printf -- 'MicroK8s will auto-switch kube-proxy to nftables mode on startup.\n'
printf -- 'If the cluster still fails to start, inspect the kube-proxy args under /var/snap/microk8s/current/args/kube-proxy.\n'
fi

if iptables -L 2>&1 | grep FORWARD | grep DROP &> /dev/null
then
printf -- '\033[0;33m WARNING: \033[0m IPtables FORWARD policy is DROP. '
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