A command-line based Recursive DNS resolver created using Golang. It is compliant with RFC 1035 and supports the following record types.
- A record
- AAAA record
- CNAME record
- TXT record
The resolver also supports caching thereby facilitating quick resolution of domain names. The transfer of DNS messages, to and from the DNS server is done over User Datagram Protocol (UDP).
To build the project, execute the following commands.
# Make the build.sh file an executable by running the below command.
chmod +x ./build.sh
# Below command builds the project and generates the executable file.
./build.shThe Commands and Outputs section of this file gives different ways of running the executable file with various command-line options.
The main.go file in the root directory contains a sample code that can be used to invoke the DNS resolution process for a set of domain names given as command line arguments.
recType := flag.String("type", "A", "the record type to query for each domain name")
traceLogs := flag.Bool("trace", false, "Enable/Disable Trace Logs")
flag.Parse()
names := flag.Args()The above code snippet in main(), parses the command line arguments entered by the user. There are two types of arguments expected - a flag value to denote the type of DNS record being queried and whether or not trace logs are to be printed on screen, and a series of domain names for which the record type must be queried.
config.SetupConfig()The call to the SetupConfig() sets up the necessary configuration parameters required for creating an instance of the DNS resolver like Root DNS Servers file path and resolver cache file path.
resolver, err := dns.NewResolver(config.RootServerFilePath, config.CacheFilePath, *traceLogs)These are then used to create a new instance of the resolver by invoking the dns.NewResolver() method.
resolver.Resolve(name, resolver.GetRecordType(*t))Once the resolver is inititalized, the domain name resolution can be carried out by invoking the resolver.Resolve() function with each of the domain name and its record type. The GetRecordType() method gets the DNS record type object associated with the record type string fetched from the command line.
resolver.Close()Finally call the Close() method once all the domain names have been resolved. This persists the changes made to resolver cache in the local filesystem.
This section contains various examples of how ask-athena can leveraged to query for DNS records.
This example accesses the help option to understand the options available under ask-athena command.
Command entered
./ask-athena -helpOutput printed on screen
Usage: ./ask-athena [options] domain name(s)
Options available:
-help
Show help message
-trace
Enable/Disable Trace Logs
-type string
the record type to query for each domain name (default "A")This example queries the A records (IPv4 address) for www.scu.edu
Command entered
./ask-athena -type=A www.scu.eduOutput printed on screen
Querying DNS for A type record of www.scu.edu.
->> HEADER <<- Opcode: QUERY, Status: NOERROR, ID: 0
Flags: QR RD RA, QUESTION: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
QUESTION SECTION:
www.scu.edu. IN A
ANSWER SECTION:
www.scu.edu. 30 IN A 34.107.151.86
This example queries the A records (IPv4 address) for www.mit.edu
Command entered
./ask-athena -type=A www.mit.eduOutput printed on screen
Querying DNS for A type record of www.mit.edu.
->> HEADER <<- Opcode: QUERY, Status: NOERROR, ID: 0
Flags: QR RD RA, QUESTION: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 0
QUESTION SECTION:
www.mit.edu. IN A
ANSWER SECTION:
www.mit.edu. 1800 IN CNAME www.mit.edu.edgekey.net.
www.mit.edu.edgekey.net. 60 IN CNAME e9566.dscb.akamaiedge.net.
e9566.dscb.akamaiedge.net. 20 IN A 23.203.236.99
This example queries the A records (IPv4 address) for www.facebook.com
Command entered
./ask-athena -type=A www.facebook.comOutput printed on screen
Querying DNS for A type record of www.facebook.com.
->> HEADER <<- Opcode: QUERY, Status: NOERROR, ID: 0
Flags: QR RD RA, QUESTION: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 0
QUESTION SECTION:
www.facebook.com. IN A
ANSWER SECTION:
www.facebook.com. 3600 IN CNAME star-mini.c10r.facebook.com.
star-mini.c10r.facebook.com. 60 IN A 157.240.22.35
This example queries the A records (IPv4 address) for google.com with the -trace flag enabled to print the trace logs on screen.
Command entered
./ask-athena -type=A -trace=true google.comOutput printed on screen
Querying DNS for A type record of google.com.
2024/06/08 19:08:39 **********************************************
2024/06/08 19:08:39 DNS Request being sent to server - 199.7.91.13.
2024/06/08 19:08:39 **********************************************
2024/06/08 19:08:39 Request Contents are:
->> HEADER <<- Opcode: QUERY, Status: NOERROR, ID: 48339
Flags: RD, QUESTION: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0
QUESTION SECTION:
google.com. IN A
2024/06/08 19:08:39 **********************************************
2024/06/08 19:08:39 Response received back:
->> HEADER <<- Opcode: QUERY, Status: NOERROR, ID: 48339
Flags: QR RD, QUESTION: 1, ANSWER: 0, AUTHORITY: 13, ADDITIONAL: 14
QUESTION SECTION:
google.com. IN A
AUTHORITY SECTION:
com. 172800 IN NS a.gtld-servers.net.
com. 172800 IN NS b.gtld-servers.net.
com. 172800 IN NS c.gtld-servers.net.
com. 172800 IN NS d.gtld-servers.net.
com. 172800 IN NS e.gtld-servers.net.
com. 172800 IN NS f.gtld-servers.net.
com. 172800 IN NS g.gtld-servers.net.
com. 172800 IN NS h.gtld-servers.net.
com. 172800 IN NS i.gtld-servers.net.
com. 172800 IN NS j.gtld-servers.net.
com. 172800 IN NS k.gtld-servers.net.
com. 172800 IN NS l.gtld-servers.net.
com. 172800 IN NS m.gtld-servers.net.
ADDITIONAL SECTION:
a.gtld-servers.net. 172800 IN A 192.5.6.30
b.gtld-servers.net. 172800 IN A 192.33.14.30
c.gtld-servers.net. 172800 IN A 192.26.92.30
d.gtld-servers.net. 172800 IN A 192.31.80.30
e.gtld-servers.net. 172800 IN A 192.12.94.30
f.gtld-servers.net. 172800 IN A 192.35.51.30
g.gtld-servers.net. 172800 IN A 192.42.93.30
h.gtld-servers.net. 172800 IN A 192.54.112.30
i.gtld-servers.net. 172800 IN A 192.43.172.30
j.gtld-servers.net. 172800 IN A 192.48.79.30
k.gtld-servers.net. 172800 IN A 192.52.178.30
l.gtld-servers.net. 172800 IN A 192.41.162.30
m.gtld-servers.net. 172800 IN A 192.55.83.30
a.gtld-servers.net. 172800 IN AAAA 2001:503:a83e::2:30
2024/06/08 19:08:39 **********************************************
2024/06/08 19:08:39 **********************************************
2024/06/08 19:08:39 DNS Request being sent to server - 192.5.6.30.
2024/06/08 19:08:39 **********************************************
2024/06/08 19:08:39 Request Contents are:
->> HEADER <<- Opcode: QUERY, Status: NOERROR, ID: 48339
Flags: RD, QUESTION: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0
QUESTION SECTION:
google.com. IN A
2024/06/08 19:08:39 **********************************************
2024/06/08 19:08:39 Response received back:
->> HEADER <<- Opcode: QUERY, Status: NOERROR, ID: 48339
Flags: QR RD, QUESTION: 1, ANSWER: 0, AUTHORITY: 4, ADDITIONAL: 8
QUESTION SECTION:
google.com. IN A
AUTHORITY SECTION:
google.com. 172800 IN NS ns2.google.com.
google.com. 172800 IN NS ns1.google.com.
google.com. 172800 IN NS ns3.google.com.
google.com. 172800 IN NS ns4.google.com.
ADDITIONAL SECTION:
ns2.google.com. 172800 IN AAAA 2001:4860:4802:34::a
ns2.google.com. 172800 IN A 216.239.34.10
ns1.google.com. 172800 IN AAAA 2001:4860:4802:32::a
ns1.google.com. 172800 IN A 216.239.32.10
ns3.google.com. 172800 IN AAAA 2001:4860:4802:36::a
ns3.google.com. 172800 IN A 216.239.36.10
ns4.google.com. 172800 IN AAAA 2001:4860:4802:38::a
ns4.google.com. 172800 IN A 216.239.38.10
2024/06/08 19:08:39 **********************************************
2024/06/08 19:08:39 **********************************************
2024/06/08 19:08:39 DNS Request being sent to server - 216.239.34.10.
2024/06/08 19:08:39 **********************************************
2024/06/08 19:08:39 Request Contents are:
->> HEADER <<- Opcode: QUERY, Status: NOERROR, ID: 48339
Flags: RD, QUESTION: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0
QUESTION SECTION:
google.com. IN A
2024/06/08 19:08:39 **********************************************
2024/06/08 19:08:39 Response received back:
->> HEADER <<- Opcode: QUERY, Status: NOERROR, ID: 48339
Flags: QR AA RD, QUESTION: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
QUESTION SECTION:
google.com. IN A
ANSWER SECTION:
google.com. 300 IN A 142.251.32.46
2024/06/08 19:08:39 **********************************************
->> HEADER <<- Opcode: QUERY, Status: NOERROR, ID: 48339
Flags: QR RD RA, QUESTION: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
QUESTION SECTION:
google.com. IN A
ANSWER SECTION:
google.com. 300 IN A 142.251.32.46