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client.go
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client.go
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package rest
import (
"context"
"encoding/json"
"fmt"
"github.com/coredns/coredns/request"
"github.com/miekg/dns"
"io/ioutil"
"log"
"net"
"net/http"
"regexp"
"strings"
)
var reDot = regexp.MustCompile("\\.$")
func ValidateIP(v string) bool {
return net.ParseIP(string(v)) != nil
}
type Client struct {
url string
ttl uint32
}
type DomainResponse struct {
A []string `json:"a"`
AAAA []string `json:"aaaa"`
}
func (z Client) Name() string {
return "rest"
}
func BuildClient(url string, ttl uint32) (Client, error) {
if !strings.HasSuffix(url, "/") {
url = url + "/"
}
return Client{url: url, ttl: ttl}, nil
}
func (z Client) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
state := request.Request{W: w, Req: r}
qname := state.Name()
var tt string
switch state.QType() {
case dns.TypeA:
tt = "A"
case dns.TypeAAAA:
tt = "AAAA"
default:
// NXDOMAIN
return dns.RcodeNameError, nil
}
domain := reDot.ReplaceAllString(qname, "")
tt = "ALL"
url := fmt.Sprintf("%v%v/%v", z.url, tt, domain)
resp, err := http.Get(url)
if err != nil {
LogVerbose("failed to build REST request: [%v]; URL: [%v]", err, url)
return dns.RcodeServerFailure, err
}
var response DomainResponse
if resp.StatusCode == http.StatusOK {
//
body, err := ioutil.ReadAll(resp.Body)
if err != nil {
LogVerbose("failed to read response body: [%v];", err)
return dns.RcodeServerFailure, err
}
err = json.Unmarshal(body, &response)
if err != nil {
LogVerbose("failed to deserialize response: [%v]; response: [%v];", err, body)
return dns.RcodeServerFailure, err
}
LogVerbose("Domain [%v] resolves to {A: %v, AAAA: %v};", domain, response.A, response.AAAA)
m := new(dns.Msg)
switch state.QType() {
case dns.TypeA:
if len(response.A) == 0 {
m.SetRcode(r, dns.RcodeSuccess)
//m.Ns = []dns.RR{soa(n)}
_ = w.WriteMsg(m)
return dns.RcodeSuccess, nil
}
m.SetReply(r)
m.Answer = z.buildAnswers(qname, state.QType(), response.A...)
case dns.TypeAAAA:
if len(response.AAAA) == 0 {
m.SetRcode(r, dns.RcodeSuccess)
//m.Ns = []dns.RR{soa(n)}
_ = w.WriteMsg(m)
return dns.RcodeSuccess, nil
}
m.SetReply(r)
m.Answer = z.buildAnswers(qname, state.QType(), response.AAAA...)
}
m.Authoritative = true
m.RecursionDesired = false
m.RecursionAvailable = false
_ = w.WriteMsg(m)
return dns.RcodeSuccess, nil
} else {
body, _ := ioutil.ReadAll(resp.Body)
LogVerbose("got non-200 response: [%v]; body: [%v];", resp.StatusCode, body)
m := new(dns.Msg)
m.Authoritative = true
m.RecursionAvailable = false
m.RecursionDesired = false
m.SetRcode(r, dns.RcodeNameError)
//m.Ns = []dns.RR{soa(n)}
_ = w.WriteMsg(m)
return dns.RcodeSuccess, nil
}
}
func (z Client) buildAnswers(qname string, qtype uint16, ips ...string) []dns.RR {
switch qtype {
case dns.TypeA:
return z.answersA(qname, ips...)
case dns.TypeAAAA:
return z.answersAAAA(qname, ips...)
default:
log.Fatalf("unexpected qtype: %v", qtype)
}
return []dns.RR{}
}
func (z Client) answersA(qname string, ips ...string) (answers []dns.RR) {
answers = make([]dns.RR, len(ips))
for i, v := range ips {
r := new(dns.A)
r.Hdr = dns.RR_Header{Name: qname, Rrtype: dns.TypeA, Class: dns.ClassINET, Ttl: z.ttl}
r.A = net.ParseIP(v)
answers[i] = r
}
return
}
func (z Client) answersAAAA(qname string, ips ...string) (answers []dns.RR) {
answers = make([]dns.RR, len(ips))
for i, v := range ips {
r := new(dns.AAAA)
r.Hdr = dns.RR_Header{Name: qname, Rrtype: dns.TypeAAAA, Class: dns.ClassINET, Ttl: z.ttl}
r.AAAA = net.ParseIP(v)
answers[i] = r
}
return
}