From 5d0800e8a6b74a536992d10c57d9126f0048e98f Mon Sep 17 00:00:00 2001
From: Jesse Morgan <jesse@jesterpm.net>
Date: Mon, 23 Apr 2018 09:57:06 -0700
Subject: Add update-dyndns script.

---
 update-dyndns | 111 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 111 insertions(+)
 create mode 100755 update-dyndns

diff --git a/update-dyndns b/update-dyndns
new file mode 100755
index 0000000..5ac19e0
--- /dev/null
+++ b/update-dyndns
@@ -0,0 +1,111 @@
+#!/bin/bash
+
+##
+## Update a Route53 record with this host's IP addresses.
+##
+## $DIR/.dyndns/config should contain something like:
+##   ZONEID="AWS_ZONE_ID"
+##   TTL=60
+##   ENABLE_IP6=true
+##   ENABLE_IP4=false
+##
+## Adapted from https://willwarren.com/2014/07/03/roll-dynamic-dns-service-using-amazon-route53/
+##
+
+DIR=$HOME/.dyndns
+
+if [ ! -f $DIR/config ]; then
+    echo "Config is missing. Exiting."
+    exit 1
+fi
+
+source $DIR/config
+
+RECORDSET=$(hostname --fqdn)
+COMMENT="Auto updating @ `date`"
+
+IP4=$(dig +short myip.opendns.com @resolver1.opendns.com)
+IP6=$((ip -6 addr list|grep inet6|grep global|grep -v temporary|awk '{print $2}'; ip -6 addr list|grep inet6|grep global|grep temporary|awk -F '{print $2}')|head -n1|cut -d/ -f1)
+
+function valid_ip4()
+{
+    local ip=$1
+    local stat=1
+
+    if [[ $ip =~ ^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$ ]]; then
+        OIFS=$IFS
+        IFS='.'
+        ip=($ip)
+        IFS=$OIFS
+        [[ ${ip[0]} -le 255 && ${ip[1]} -le 255 \
+            && ${ip[2]} -le 255 && ${ip[3]} -le 255 ]]
+        stat=$?
+    fi
+    return $stat
+}
+
+function update_dns() {
+    local IP=$1
+    local TYPE=$2
+    local TMPFILE=$(mktemp /tmp/temporary-file.XXXXXXXX)
+    cat > ${TMPFILE} << EOF
+    {
+      "Comment":"$COMMENT",
+      "Changes":[
+        {
+          "Action":"UPSERT",
+          "ResourceRecordSet":{
+            "ResourceRecords":[
+              {
+                "Value":"$IP"
+              }
+            ],
+            "Name":"$RECORDSET",
+            "Type":"$TYPE",
+            "TTL":$TTL
+          }
+        }
+      ]
+    }
+EOF
+
+    # Update the Hosted Zone record
+    aws route53 change-resource-record-sets \
+        --hosted-zone-id $ZONEID \
+        --change-batch file://"$TMPFILE"
+    ret="$?"
+    echo
+
+    # Clean up
+    rm $TMPFILE
+
+    return $ret
+}
+
+IP4FILE="$DIR/ip4"
+IP6FILE="$DIR/ip6"
+
+# IPv4
+if $ENABLE_IP4 && valid_ip4 $IP4; then
+    touch "$IP4FILE"
+
+    if grep -Fxq "$IP4" "$IP4FILE"; then
+        echo "IP is still $IP4. Skipping."
+    else
+        echo "IP4 has changed to $IP4"
+        update_dns $IP4 A && echo "$IP4" > "$IP4FILE"
+    fi
+fi
+
+# IPv6
+if $ENABLE_IP6 && [ -n "$IP6" ]; then
+    touch "$IP6FILE"
+
+    if grep -Fxq "$IP6" "$IP6FILE"; then
+        echo "IP is still $IP6. Skipping."
+    else
+        echo "IP6 has changed to $IP6"
+        update_dns $IP6 AAAA && echo "$IP6" > "$IP6FILE"
+    fi
+fi
+
-- 
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