123 lines
3.3 KiB
Bash
123 lines
3.3 KiB
Bash
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#!/bin/bash
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# Deploys CoreDNS to a cluster currently running Kube-DNS.
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show_help () {
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cat << USAGE
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usage: $0 [ -r REVERSE-CIDR ] [ -i DNS-IP ] [ -d CLUSTER-DOMAIN ] [ -t YAML-TEMPLATE ]
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-r : Define a reverse zone for the given CIDR. You may specify this option more
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than once to add multiple reverse zones. If no reverse CIDRs are defined,
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then the default is to handle all reverse zones (i.e. in-addr.arpa and ip6.arpa)
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-i : Specify the cluster DNS IP address. If not specified, the IP address of
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the existing "kube-dns" service is used, if present.
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-s : Skips the translation of kube-dns configmap to the corresponding CoreDNS Corefile configuration.
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USAGE
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exit 0
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}
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# Simple Defaults
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DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null && pwd )"
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CLUSTER_DOMAIN=cluster.local
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YAML_TEMPLATE="$DIR/coredns.yaml.sed"
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STUBDOMAINS=""
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UPSTREAM=\\/etc\\/resolv\.conf
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# Translates the kube-dns ConfigMap to equivalent CoreDNS Configuration.
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function translate-kube-dns-configmap {
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kube-dns-upstreamnameserver-to-coredns
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kube-dns-stubdomains-to-coredns
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}
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function kube-dns-upstreamnameserver-to-coredns {
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up=$(kubectl -n kube-system get configmap kube-dns -ojsonpath='{.data.upstreamNameservers}' 2> /dev/null | tr -d '[",]')
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if [[ ! -z ${up} ]]; then
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UPSTREAM=${up}
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fi
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}
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function kube-dns-stubdomains-to-coredns {
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STUBDOMAIN_TEMPLATE='
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SD_DOMAIN:53 {
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errors
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cache 30
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loop
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forward . SD_DESTINATION {
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max_concurrent 1000
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}
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}'
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function dequote {
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str=${1#\"} # delete leading quote
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str=${str%\"} # delete trailing quote
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echo ${str}
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}
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function parse_stub_domains() {
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sd=$1
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# get keys - each key is a domain
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sd_keys=$(echo -n $sd | jq keys[])
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# For each domain ...
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for dom in $sd_keys; do
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dst=$(echo -n $sd | jq '.['$dom'][0]') # get the destination
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dom=$(dequote $dom)
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dst=$(dequote $dst)
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sd_stanza=${STUBDOMAIN_TEMPLATE/SD_DOMAIN/$dom} # replace SD_DOMAIN
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sd_stanza=${sd_stanza/SD_DESTINATION/$dst} # replace SD_DESTINATION
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echo "$sd_stanza"
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done
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}
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sd=$(kubectl -n kube-system get configmap kube-dns -ojsonpath='{.data.stubDomains}' 2> /dev/null)
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STUBDOMAINS=$(parse_stub_domains "$sd")
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}
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# Get Opts
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while getopts "hsr:i:d:t:k:" opt; do
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case "$opt" in
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h) show_help
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;;
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s) SKIP=1
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;;
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r) REVERSE_CIDRS="$REVERSE_CIDRS $OPTARG"
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;;
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i) CLUSTER_DNS_IP=$OPTARG
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;;
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d) CLUSTER_DOMAIN=$OPTARG
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;;
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t) YAML_TEMPLATE=$OPTARG
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;;
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esac
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done
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# Conditional Defaults
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if [[ -z $REVERSE_CIDRS ]]; then
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REVERSE_CIDRS="in-addr.arpa ip6.arpa"
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fi
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if [[ -z $CLUSTER_DNS_IP ]]; then
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# Default IP to kube-dns IP
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CLUSTER_DNS_IP=$(kubectl get service --namespace kube-system kube-dns -o jsonpath="{.spec.clusterIP}")
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if [ $? -ne 0 ]; then
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>&2 echo "Error! The IP address for DNS service couldn't be determined automatically. Please specify the DNS-IP with the '-i' option."
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exit 2
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fi
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fi
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if [[ "${SKIP}" -ne 1 ]] ; then
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translate-kube-dns-configmap
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fi
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orig=$'\n'
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replace=$'\\\n'
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sed -e "s/CLUSTER_DNS_IP/$CLUSTER_DNS_IP/g" \
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-e "s/CLUSTER_DOMAIN/$CLUSTER_DOMAIN/g" \
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-e "s?REVERSE_CIDRS?$REVERSE_CIDRS?g" \
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-e "s@STUBDOMAINS@${STUBDOMAINS//$orig/$replace}@g" \
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-e "s/UPSTREAMNAMESERVER/$UPSTREAM/g" \
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"${YAML_TEMPLATE}"
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