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package dnsutil
import (
"time"
"github.com/miekg/dns"
)
var (
// TypeToString contains a mapping of DNS request type to string.
TypeToString = dns.TypeToString
// RcodeToString contains a mapping of Mapping DNS response code to string.
RcodeToString = dns.RcodeToString
)
// Answers returns all values in the answer section of DNS message msg.
func Answers(msg *dns.Msg) []string {
var answers []string
for _, answer := range msg.Answer {
switch v := answer.(type) {
case *dns.A:
answers = append(answers, v.A.String())
case *dns.AAAA:
answers = append(answers, v.AAAA.String())
case *dns.MX:
answers = append(answers, v.Mx)
case *dns.PTR:
answers = append(answers, v.Ptr)
case *dns.NS:
answers = append(answers, v.Ns)
case *dns.CNAME:
answers = append(answers, v.Target)
}
}
return answers
}
// MinTTL returns the lowest TTL of of answer, authority and additional sections.
func MinTTL(msg *dns.Msg) time.Duration {
var ttl uint32 = (1 << 31) - 1 // Maximum TTL from RFC 2181
for _, answer := range msg.Answer {
ttl = min(answer.Header().Ttl, ttl)
}
for _, ns := range msg.Ns {
ttl = min(ns.Header().Ttl, ttl)
}
for _, extra := range msg.Extra {
// OPT (EDNS) is a pseudo record which uses TTL field for extended RCODE and flags
if extra.Header().Rrtype == dns.TypeOPT {
continue
}
ttl = min(extra.Header().Ttl, ttl)
}
return time.Duration(ttl) * time.Second
}
func min(x, y uint32) uint32 {
if x < y {
return x
}
return y
}
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