Summary

• This program gets the list of public nameservers from https://public-dns.info/.
• Picks one nameserver from every country.
• Do a CNAME query for the specified domain against these picked nameservers.

Things to note

• Default timeout is 3 seconds

Sample Output

• -number-ns=5: Will set the number of nameservers to query as 5
• -timeout=0.1s: Sets DNS timeout as 0.1s
• -filter-countries=IN,SG,JP: Sets the countries to query CNAME in
• -domain: Set the domain to query CNAME for

➜ $?=0 shadyabhi/cdnfinder [ 4:48PM] (master|…) % ./cdnfinder -domain=static.licdn.com -timeout=0.1s -number-ns=5 -filter-countries=IN,SG,JP
WARN[0000] Skipping a line while parsing csv at line: 46346, column: 0
|-----------|----------------------|-----------------------------------------|----------------|-------------|
|  COUNTRY  |         CITY         |              CDN/HOSTNAME               |       IP       |    TIME     |
|-----------|----------------------|-----------------------------------------|----------------|-------------|
| Singapore | SG - Singapore       | EdgeCast   - cs627.wac.epsiloncdn.net.  | 202.136.162.11 | 44.04332ms  |
| India     | IN - Mumbai          | EdgeCast   - cs627.wac.epsiloncdn.net.  | 203.115.71.66  | 20.700975ms |
| India     | IN - Bhubaneswar     | EdgeCast   - cs627.wac.epsiloncdn.net.  | 202.62.224.2   | 61.284302ms |
| India     | IN - Mumbai          | EdgeCast   - cs627.wac.epsiloncdn.net.  | 202.138.120.4  | 27.423725ms |
| Singapore | SG -                 | Akamai     - e9706.dscg.akamaiedge.net. | 121.52.206.130 | 44.463913ms |
|-----------|----------------------|-----------------------------------------|----------------|-------------|
INFO[0000] Took 669.099039ms to query DNS servers...

>>>  0s elasped...
➜ $?=0 shadyabhi/cdnfinder [ 4:49PM] (master|…) %

TODO

• Limit goroutines for DNS queries
• Option to force refresh nameserver.csv