Low-dependency bash script to upsert/delete current Droplet public and private IPs in DigitalOcean DNS

update_dns

#!/bin/bash

STATE=$1
TOKEN=$2
TOKEN=${TOKEN:-$DIGITALOCEAN_TOKEN}

HOSTNAME=$(hostname)

PRIVATE_IP_BASE=10.123.
PRIVATE_DOMAIN=internal.example.com
PUBLIC_DOMAIN=external.example.com

CURL=/usr/bin/curl

function exec_api ()
{
    $CURL -sS \
        -X $1 -H "Content-Type: application/json" -H "Authorization: Bearer $TOKEN" \
        "https://api.digitalocean.com/v2/domains/$2/records$3"
}

function delete_all_records ()
{
    echo "Deleting $1.$2"

    HOST=$1
    DOMAIN=$2
    TO_DELETE=$(exec_api GET $DOMAIN "?name=$HOST.$DOMAIN" | jq -r '.domain_records[]|.id')

    if [ ! -z $TO_DELETE ]; then
        for ID in $TO_DELETE; do
            $CURL -sS \
                -X DELETE -H "Content-Type: application/json" -H "Authorization: Bearer $TOKEN" \
                "https://api.digitalocean.com/v2/domains/$DOMAIN/records/$ID"
        done
    fi
}

function add_a_record ()
{
    HOST=$1
    DOMAIN=$2
    IP=$3
    TTL=$4

    echo "Adding $1.$2 - $3"

    TEMP=$(mktemp)

    cat > $TEMP <<-EOF
        {
            "type": "A",
            "name": "$HOST",
            "data": "$IP",
            "ttl": $TTL
        }
EOF

    $CURL -sS \
        -X POST -H "Content-Type: application/json" -H "Authorization: Bearer $TOKEN" \
        "https://api.digitalocean.com/v2/domains/$DOMAIN/records" \
        -d @$TEMP > /dev/null

    rm $TEMP
}

function check () {
    echo "Checking $1.$2 -> '$3'"

    RESULT=$(exec_api GET $2 "?name=$1.$2" | jq -r '.domain_records[]|.data')
    RC=$?
    if [ $RC != 0 ]; then
        return 1
    elif [ "$3" != "$RESULT" ]; then
        return 1
    else
        return 0
    fi
}

function check_wc () {
    check   "$1" $2 $3
    C0=$?
    check "*.$1" $2 $3
    C1=$?
    let C=$C0+$C1
    return $C
}

function verify_loop () {
    echo "Checking $1.$2 -> '$3'"

    for C in {1..5}; do
        RESULT=$(exec_api GET $2 "?name=$1.$2" | jq -r '.domain_records[]|.data')
        RC=$?
        if [ $RC != 0 ]; then
            >&2 echo "$C: Check failed  $1 $2: rc=$RC"
        elif [ "$3" != "$RESULT" ]; then
            >&2 echo "$C: Check failed  $1 $2: '$3' != '$RESULT'"
        else
            return
        fi
        sleep $C
    done
    
    >&2 echo "Check failed: $1 $2 '$3' != '$RESULT' (rc=$RC)"
    exit 1
}

function add_records ()
{
    add_a_record   "$1" $2 $3 300
    add_a_record "*.$1" $2 $3 300
    verify_loop  "$1" $2 $3
    verify_loop "*.$1" $2 $3
}

function delete_records ()
{
    delete_all_records $1 $2
    delete_all_records "*.$1" $2
    verify_loop   "$1" $2 ""
    verify_loop "*.$1" $2 ""
}

function get_private_ip () {
    PRIVATE_IP=$(jq -r '.private_ipv4' /etc/ansible/facts.d/droplet.fact)
    if [[ $? != 0 || "$PRIVATE_IP" == "" ]]; then
        PRIVATE_IP=$(
            ip -j -4 -o addr show dev eth1 |
                jq -r "[.[0].addr_info[] | select(.local | startswith(\"$PRIVATE_IP_BASE\")) | .local][0]"
        )
    fi
}

function get_public_ip () {
    PUBLIC_IP=$(jq -r '.public_ipv4' /etc/ansible/facts.d/droplet.fact)
    if [[ $? != 0 || "$PUBLIC_IP" == "" ]]; then
        PUBLIC_IP=$(
            ip -j -4 -o addr show dev eth0 | 
                jq -r '[.[0].addr_info[] | select(.local | startswith("10.") | not) | .local][0]'
        )
    fi
}

if [ "present" == "$STATE" ]; then

    get_public_ip
    if ! check_wc $HOSTNAME $PUBLIC_DOMAIN $PUBLIC_IP; then
        delete_records $HOSTNAME $PUBLIC_DOMAIN
        add_records $HOSTNAME $PUBLIC_DOMAIN $PUBLIC_IP
    fi

    get_private_ip
    if ! check_wc $HOSTNAME $PRIVATE_DOMAIN $PRIVATE_IP; then
        delete_records $HOSTNAME $PRIVATE_DOMAIN
        add_records $HOSTNAME $PRIVATE_DOMAIN $PRIVATE_IP
    fi

elif [ "absent" == "$STATE" ]; then
    delete_records $HOSTNAME $PUBLIC_DOMAIN
    delete_records $HOSTNAME $PRIVATE_DOMAIN
else
    >&2 cat <<-EOF

        Syntax: $0 <present|absent> <digitalocean_token>

EOF
    exit 1
fi

exit 0