Esphole is a proof-of-concept of an ad blocking DNS server for the esp8266.

Note: The solution is far from being production ready. I just wanted to see if it was possible to develop a simple DNS ad blocker inside the ESP

It uses a modified version of the DNS Server library included with the Esp8266 core for Arduino

The first versions uploaded the full hosts file to the SPIFFS. The performance of finding the domain in the full hosts file was really poor, so for the current version the hosts file is preprocessed and stored in smaller files based on the lenght of the domain

$ cd utils
$ gen_block_lists.sh

This downloads the hosts file and saves it in different files in the data directory

Follow the guide of Arduino ESP8266 filesystem uploader to install the SPIFFS uploader and then select: Tools > ESP8266 Sketch Data Upload in order to upload data directory to the ESP

Open the sketch directory with Arduino editor and edit esphole.ino in order to change the WIFI settings

#define wifi_ssid "........"
#define wifi_password "........"

Then, upload it to the ESP

Open the serial monitor or minicom in order to find the IP of the ESP device (or scan your network in order to find it) and use nslookup in order to test some domains:

$ nslookup - 192.168.0.161
> github.com
Server:		192.168.0.161
Address:	192.168.0.161#53

Non-authoritative answer:
Name:	github.com
Address: 192.30.253.112

> analytics.google.com
Server:		192.168.0.161
Address:	192.168.0.161#53

Non-authoritative answer:
Name:	analytics.google.com
Address: 0.0.0.0

In the serial monitor the debug information is shown:

WiFi connected | IP address: 192.168.0.161
DNS Server ready

Domain: github.com | IP:192.30.253.112
Resolv took 70 ms | Find took 57 ms

Domain: analytics.google.com Blocked | Find took 30 ms

Note: Esphole was tested with a Wemos D1 min and an Amica NodeMCU.