rdns

Simple and pretty fast CLI tool to query PTR records of IP addresses and/or ranges.
Handy when performing network investigations ;)

Installation

$ go install github.com/da-rod/rdns@latest

Usage

Takes an IP address or range as argument:

$ rdns 140.82.118.0/28
140.82.118.0 []
140.82.118.1 [lb-140-82-118-1-ams.github.com.]
140.82.118.2 [lb-140-82-118-2-ams.github.com.]
140.82.118.3 [lb-140-82-118-3-ams.github.com.]
140.82.118.4 [lb-140-82-118-4-ams.github.com.]
140.82.118.5 [lb-140-82-118-5-ams.github.com.]
140.82.118.6 [lb-140-82-118-6-ams.github.com.]
140.82.118.7 [lb-140-82-118-7-ams.github.com.]
140.82.118.8 [lb-140-82-118-8-ams.github.com.]
140.82.118.9 [lb-140-82-118-9-ams.github.com.]
140.82.118.10 [lb-140-82-118-10-ams.github.com.]
140.82.118.11 [lb-140-82-118-11-ams.github.com.]
140.82.118.12 [lb-140-82-118-12-ams.github.com.]
140.82.118.13 [lb-140-82-118-13-ams.github.com.]
140.82.118.14 [lb-140-82-118-14-ams.github.com.]
140.82.118.15 []

Reads data from stdin:

$ cat /tmp/ips.txt | rdns -
216.58.204.0 [lhr35s07-in-f0.1e100.net.]
216.58.204.1 [lhr35s07-in-f1.1e100.net.]
216.58.204.2 [lhr35s07-in-f2.1e100.net.]
216.58.204.3 [lhr48s21-in-f3.1e100.net.]
[...]

Notes:

• Filters input which is not (valid, duh) strict IP or IP range
• When working from stdin, it filters out empty and commented lines (redundant, I know...)
• Accepts "short" IP ranges like x.y.z and treats it as x.y.z.0/24

(Known) Alternative

• http://www.spamshield.org/fast-rdns.pl