CloudFlare Dynamic DNS Shell Script

cloudflare_dyn_dns.sh

#!/bin/sh
#
# CloudFlare Dynamic DNS
#
# Updates CloudFlare records with the current public IP address
#
# Takes the same basic arguments as A/CNAME updates in the CloudFlare v4 API
# https://www.cloudflare.com/docs/client-api.html#s5.2
#
# Use with cron jobs etc.
#
# e.g.
#
# manually run:
# cloudflare_dyn_dns.sh -key 404613183ab3971a2118ae5bf03d63e032f9e -email test@example.com -zone example.com -name extra
#
# cronjob entry to run every 5 minutes:
# */5 * * * * /path/to/cloudflare_dyn_dns.sh -key 404613183ab3971a2118ae5bf03d63e032f9e -email test@example.com -zone example.com -name extra >> /path/to/cloudflare_dyn_dns.log
# 
# will both set the type A DNS record for extra.example.com to the current public IP address for user test@example.com with the provided API key

key=
email=
zone=
zone_id=
type=A
rec_id=
name=
content=
ttl=1
proxied=false

while [ "$1" != "" ]; do
    case $1 in
        -key )     shift
                   key=$1
                   ;;
        -email )   shift
                   email=$1
                   ;;
        -zone )    shift
                   zone=$1
                   ;;
        -zone_id ) shift
                   zone_id=$1
                   ;;
        -type )    shift
                   type=$1
                   ;;
        -rec_id )  shift
                   rec_id=$1
                   ;;
        -name )    shift
                   name=$1
                   ;;
        -content ) shift
                   content=$1
                   ;;
        -ttl )     shift
                   ttl=$1
                   ;;
        -proxied ) shift
                   proxied=$1
                   ;;
        * )        echo "unknown parameter $1"
                   exit 1
    esac
    shift
done

if [ "$content" = "" ]
then
    content=`curl -s http://myexternalip.com/raw`
    if [ "$content" = "" ]
    then
        date
        echo "No IP address to set record value with."
        exit 1
    fi
fi

if [ "$name" = "" ]
then
    echo "You must provide the name of the record you wish to change."
    exit 1
fi

if [ "$zone" = "" ]
then
    echo "You must provide the domain you wish to change."
    exit 1
fi

command -v host > /dev/null 2>&1
if [ "$?" = "1" ]
then
    command -v nslookup > /dev/null 2>&1
    if [ "$?" = "1" ]
    then
        echo "Cannot find a way to check existing $type record for $name.$zone"
        exit 1
    fi
    existing_content=`nslookup -type=$type $name.$zone | awk -F 'Address: ' 'NR==6 { print $2 }'`
else
    existing_content=`host -t $type $name.$zone | sed -E 's/.+?\s+([^\s]+)$/\1/'`
fi

if [ "$content" = "$existing_content" ]
then
    echo "Existing record value $existing_content is the same as provided content $content. Exiting."
    exit
fi

if [ "$key" = "" ]
then
    echo "You must provide your user API token."
    exit 1
fi

if [ "$email" = "" ]
then
    echo "You must provide your user email."
    exit 1
fi

# Get the zone id for the entry we're trying to change if it's not provided
if [ "$zone_id" = "" ]
then
    zone_response_json=`curl -X GET "https://api.cloudflare.com/client/v4/zones?name=$zone" -H "X-Auth-Email: $email" -H "X-Auth-Key: $key" -H "Content-Type: application/json"`
    zone_id=`echo $zone_response_json | sed -E "s/.+\"result\":\[\{\"id\":\"([a-f0-9]+)\"[^\}]+$zone.+/\1/g"`
    if [ "$zone_id" = "" ]
    then
        echo "Cloudflare DNS Zone id could not be found, please make sure it exists"
        exit 1
    fi
fi

# Get the record id for the entry we're trying to change if it's not provided
if [ "$rec_id" = "" ]
then
    rec_response_json=`curl -X GET "https://api.cloudflare.com/client/v4/zones/$zone_id/dns_records?name=$name.$zone" -H "X-Auth-Email: $email" -H "X-Auth-Key: $key" -H "Content-Type: application/json"`
    rec_id=`echo $rec_response_json | sed -E "s/.+\"result\":\[\{\"id\":\"([a-f0-9]+)\"[^\}]+\"type\":\"$type\"[^\}]+$name.$zone.+/\1/g"`
    if [ "$rec_id" = "" ]
    then
        echo "Cloudflare DNS Record id could not be found, please make sure it exists"
        exit 1
    fi
fi

# Update the DNS record
update_response=`curl -X PUT "https://api.cloudflare.com/client/v4/zones/$zone_id/dns_records/$rec_id" -H "X-Auth-Email: $email" -H "X-Auth-Key: $key" -H "Content-Type: application/json" --data "{\"id\":\"$rec_id\",\"type\":\"$type\",\"name\":\"$name.$zone\",\"content\":\"$content\",\"ttl\":$ttl,\"proxied\":$proxied}"`

success_val=`echo $update_response | sed -E "s/.+\"success\":(true|false).+/\1/g"`
if [ "$success_val" = "true" ]
then
    echo "Record Updated."
else
    echo "Record update failed."
    exit 1
fi

Thank you!
script works:
[root @ router1 sbin] # /etc/rc.d/cf_eth0.sh
Attempting to get current public IP Address for content.
Record Updated.

But I there are several IP addresses. How can I update a specific (one of the four IP)?

add "content=" )))

Hi @anshgh

apologies for the delayed response.

You are quite correct, using an command line argument of -content 8.8.8.8 will ensure the script ignores the current public IP address and sets the content of the DNS record to 8.8.8.8
The script was originally only intended for boxes with one public IP address, hence defaulting to the public IP address of whichever is the default network adapter

got Stuck at line "++ curl -s http://myexternalip.com/raw"

replaces it with this line, to make it work:

curl -s checkip.dyndns.org | sed -e 's/.Current IP Address: //' -e 's/<.$//'

Not sure why this isn't working for you @farhantahirt , possibly some network issues? Could investigate with a traceroute?
If myexternalip.com doesn't work, can I suggest using a provider that doesn't require string a replace on the returned content? e.g. https://api.ipify.org/ or http://ipv4.icanhazip.com/