Parsing type dns.RR

I'm new to Go and trying to get a small DNS program working that parses returned A and CNAME records. This is using github.com/miekg/dns package.

I'm having trouble understanding how to properly parse the returned resource record for A or CNAME. For the A record, I want to get the IP address and store it in a variable. For the CNAME that has multiple RRs returned, I'd like to parse the Name and Address fields and store in variables.

I've tried converting the structure to a string or unpacking it to no avail. Anyone can lend any insight, greatly appreciate it.

Here is the code below. Text file contains a single line with 'www':

package main
import (
"bufio"
"fmt"
"log"
"os"
"github.com/miekg/dns"
)
func dns_request_fwd(s string) []dns.RR {
//fmt.Println(s, " : started processing DNS request")
m1 := new(dns.Msg)
m1.Id = dns.Id()
m1.RecursionDesired = true
m1.Question = make([]dns.Question, 1)
m1.Question[0] = dns.Question{s, dns.TypeA, dns.ClassINET}
in, err := dns.Exchange(m1, "8.8.8.8:53")
if err != nil {
log.Fatal(err)
}
if len(in.Answer) > 0 {
//fmt.Println("Response greater than 0 - got something!")
//fmt.Println(in.Answer)
} else {
//fmt.Println("Empty DNS Response")
return nil
}
if _, ok := in.Answer[0].(*dns.A); ok {
//fmt.Println("Detected an 'A' record Answer.  Returning RR!")
return in.Answer
} else if _, ok := in.Answer[0].(*dns.CNAME); ok {
//fmt.Println("Detected a 'CNAME' record Answer.  Returning RR!")
return in.Answer
} else {
fmt.Println("Returning nil")
return nil
}
}
func main() {
f, err := os.Open("list4.txt")
if err != nil {
log.Fatal(err)
}
defer f.Close()
domain := "acme.com"
domain_lookup := "." + domain + "." 
scanner := bufio.NewScanner(f)
for scanner.Scan() {
a_record := scanner.Text()
lookup := a_record+domain_lookup
fmt.Println("Looking up: ", lookup)
dreq := dns_request_fwd(lookup)
if len(dreq) > 0 {
fmt.Println("    [+] Forward Lookup answer")
if _, ok := dreq[0].(*dns.CNAME); ok {
fmt.Println("    [+] Type is CNAME")
//fmt.Println(dreq[0].(*dns.CNAME))
//fmt.Println(dreq[1].(*dns.A))
fmt.Println("    [+] Alias records: ", len(dreq) -1)
// Iterate through returned alias A records
for i, s := range dreq {
if i == 0{
//Do nothing because first record is repeat of request 
} else {
// Need to parse the below RR to get the Name + IP address returned
fmt.Println("    [+] Returned",i, s)
fmt.Println(s[0])
}
}
} else if _, ok := dreq[0].(*dns.A); ok {
fmt.Println("    [+] Type is A")
// Need to parse the below RR to get the IP address returned
fmt.Println("    [+] Answer: ", dreq[0])
}
} else {
fmt.Println("    [-] We Got Nothing")
}
}
if err := scanner.Err(); err != nil {
log.Fatal(err)
}
}

You don't need to "parse" a struct. The library parsed the response already in order to give you the struct. Just use the fields in the struct which have the data you want, like dns.A.A which is a net.IP or dns.CNAME.Target which is a string. See the package documentation for more details.

if arec, ok := dreq[0].(*dns.A); ok {
fmt.Println("    [+] Type is A")
fmt.Println("    [+] Answer: ", arec.A)
}