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|
package main
import (
"fmt"
"github.com/miekg/dns"
"strings"
)
func (r *resolver) lookup(qname string) error {
c := new(dns.Client)
t := new(dns.Transfer)
c.Net = "udp"
if *four {
c.Net = "udp4"
}
if *six {
c.Net = "udp6"
}
if *tcp {
c.Net = "tcp"
if *four {
c.Net = "tcp4"
}
if *six {
c.Net = "tcp6"
}
}
m := &dns.Msg{
MsgHdr: dns.MsgHdr{
Authoritative: false,
AuthenticatedData: false,
CheckingDisabled: false,
RecursionDesired: true,
Opcode: "query",
},
Question: make([]dns.Question, 1),
}
if op, ok := dns.StringToOpcode[strings.ToUpper(*opcode)]; ok {
m.Opcode = op
}
m.Rcode = dns.RcodeSuccess
if rc, ok := dns.StringToRcode[strings.ToUpper(*rcode)]; ok {
m.Rcode = rc
}
Query:
for i, v := range qname {
if i < len(qtype) {
qt = qtype[i]
}
if i < len(qclass) {
qc = qclass[i]
}
m.Question[0] = dns.Question{Name: dns.Fqdn(v), Qtype: qt, Qclass: qc}
m.Id = dns.Id()
if *query {
fmt.Printf("%s", m.String())
fmt.Printf("\n;; size: %d bytes\n\n", m.Len())
}
r, rtt, err := c.Exchange(m, nameserver)
Redo:
switch err {
case nil:
//do nothing
case dns.ErrTruncated:
if *fallback {
if !*dnssec {
fmt.Printf(";; Truncated, trying %d bytes bufsize\n", dns.DefaultMsgSize)
o := new(dns.OPT)
o.Hdr.Name = "."
o.Hdr.Rrtype = dns.TypeOPT
o.SetUDPSize(dns.DefaultMsgSize)
m.Extra = append(m.Extra, o)
r, rtt, err = c.Exchange(m, nameserver)
*dnssec = true
goto Redo
} else {
// First EDNS, then TCP
fmt.Printf(";; Truncated, trying TCP\n")
c.Net = "tcp"
r, rtt, err = c.Exchange(m, nameserver)
*fallback = false
goto Redo
}
}
fmt.Printf(";; Truncated\n")
default:
fmt.Printf(";; %s\n", err.Error())
continue
}
if r.Id != m.Id {
fmt.Fprintf(os.Stderr, "Id mismatch\n")
return
}
if *short {
// shortenMsg(r)
}
fmt.Printf("%v", r)
fmt.Printf("\n;; query time: %.3d µs, server: %s(%s), size: %d bytes\n", rtt/1e3, nameserver, c.Net, r.Len())
}
}
|
