Blocks ads on router level using DD-WRT

based on discussions found on this forum thread: https://www.dd-wrt.com/forum/viewtopic.php?t=313987

The simple answer: I have a cheap TP-Link TL-WR841ND router with no jffs, no USB port and limited (volatile) storage. This method:

• works even after rebooting
• keeps an up-to-date block list
• has limited overhead
• works on my cheap router

Other alternatives are the pixelserv method and using jffs to store the host list.

1. Copy the startup code below to your Administration -> Commands and Save Startup. This will create a custom script to download a blacklist and add the domains to the dnsmasq.

2. In Services -> Services -> Enable DNSMasq

3. In Setup -> Basic Setup -> Enable Forced DNS Redirection

4. To enable weekly updates, in Administration -> Management -> Cron -> Additional Cron Jobs add:

   0 11 * * 3 root /tmp/custom.sh

# wait for the rest of the services to startup
sleep 20 

# Create script to download blacklist
echo '#!/bin/sh

logger Starting blockads scripts

# clean up old list
rm /tmp/adhosts

# get new list
wget -qO- http:https://sbc.io/hosts/hosts | grep "^0.0.0.0" > /tmp/adhosts;
 
# restart service
killall dnsmasq
dnsmasq -u root -g root --conf-file=/tmp/dnsmasq.conf

logger Finished executing blockads script' >> /tmp/custom.sh;

# add executable right 
chmod +x /tmp/custom.sh

# add blacklist to dnsmasq
grep "addn-hosts=/tmp/adhosts" /tmp/dnsmasq.conf || echo "addn-hosts=/tmp/adhosts" >> /tmp/dnsmasq.conf;

# execute script
/tmp/custom.sh

• Tested with Firmware: DD-WRT v3.0-r45767 std (02/17/21) on a TP-Link TL-WR841ND v10
• The script print to Syslog. Enable it in Services -> Syslog to see if the scripts started. Alternatively Telnet into the router and check if /tmp/custom.sh exists.