Merge pull request #13 from SovereignCloudStack/feat/docker-mtu-warn

Detect MTU and issue warning.

Author: garloff

01-kind-cluster.sh

@@ -1,4 +1,19 @@
 #!/bin/bash
 set -e
+# Detect MTU of interface with default route
+DEV=$(ip route show default | head -n1 | sed 's/^.*dev \([^ ]*\).*$/\1/')
+CLOUDMTU=$(ip link show $DEV | head -n1 | sed 's/^.*mtu \([0-9]*\) .*$/\1/')
+DOCKERMTU=$(ip link show docker0 | head -n1 | sed 's/^.*mtu \([0-9]*\) .*$/\1/')
+if test $DOCKERMTU -gt $CLOUDMTU; then
+	echo "WARNING: Consider setting mtu to $((8*($CLOUDMTU/8))) in /etc/docker/daemon.json"
+	echo "  and restart docker and do docker network rm kind ..."
+	sudo ip link set dev docker0 mtu $((8*($CLOUDMTU/8)))
+	# Just in case ...
+	sudo sysctl net.ipv4.tcp_mtu_probing=1
+fi
 # Create kind cluster
-kind create cluster
+if test "$(kind get clusters)" != "kind"; then
+	kind create cluster
+else
+	echo "kind cluster already running"
+fi