PR-DNSd is a Passive-Recursive DNS daemon.


go get
sudo setcap cap_net_bind_service,cap_sys_chroot=ep go/bin/PR-DNSd
go/bin/PR-DNSd -upstream -listen
echo nameserver | sudo tee /etc/resolv.conf
dig -x $(dig +short

Use cases

  • run as local host DNS service, to fix your netstat/tcpview/lsof etc. output
  • as enterprise-internal DNS server, to also be able to do meaningful EDR/IR and log analysis
  • as cloud service, to also collect Passive DNS data from non-enterprise (home, BYOD etc.) devices
    • hint: you probably want to configure DDoS protection options
  • in cloud as DNS-over-TLS server, to additionally provide private DNS for supporting devices (ex: Android 9’s private DNS setting)
    • ex: domain pattern based firewall/proxy configuration for mobile devices

Running as your own private server for Android9’s Private DNS settings

After appropriate setcap, run:

PR-DNSd -tlslisten :853 -cert YOUR_SERVER_CRT_KEY_PEM -upstream -store pr-dnsd


cert string
TCP-TLS listener certificate (required for tls listener)
-chroot string
chroot to directory after start (default “/var/tmp”)
-count int
Count of replies allowed before debounce delay is applied (default 100)
-ctmout string
Client timeout for upstream queries
-debounce string
Required time duration between UDP replies to single IP to prevent DoS (default “200ms”)
-key string
TCP-TLS certificate key (default same as -cert value)
-listen string
listen address (default “:53”)
Don’t report normal data
-store string
Store PTR data to specified file
-tlslisten string
TCP-TLS listener address (default “:853”)
-upstream string
upstream DNS server (tcp-tls:// prefix for DoT) (default “”)
(with tls and chroot, ensure ca-certificates and resolv.conf in chroot are properly set up)