initial commit

dns.go

@@ -0,0 +1,157 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"math/rand"
+	"net"
+	"strings"
+	"sync"
+
+	"github.com/miekg/dns"
+)
+
+var (
+	dnsStringToType sync.Map
+	dnsExtraQtype   = make(map[uint16]bool)
+
+	dnsTtlRange uint32
+)
+
+func setupDns() {
+	for _, v := range []uint16{
+		dns.TypePTR, dns.TypeMX, dns.TypeTXT, dns.TypeSRV, dns.TypeLOC, dns.TypeHINFO, dns.TypeSPF,
+		dns.TypeSIG, dns.TypeKEY, dns.TypeKX, dns.TypeDS, dns.TypeRRSIG, dns.TypeNSEC, dns.TypeDNSKEY, dns.TypeNSEC3, dns.TypeNSEC3PARAM, dns.TypeTLSA, dns.TypeCDS, dns.TypeCDNSKEY, dns.TypeZONEMD, dns.TypeTKEY, dns.TypeTSIG, dns.TypeCAA,
+		dns.TypeSVCB, dns.TypeHTTPS, dns.TypeURI,
+	} {
+		dnsExtraQtype[v] = true
+	}
+
+	// warmup
+	for _, v := range []string{"SOA", "NS", "A", "AAAA", "ANY", "PTR", "CNAME"} {
+		dnsQtypeStringToValue(v)
+	}
+}
+
+func dnsIsAllowedExtraQtype(qtype uint16) bool {
+	_, found := dnsExtraQtype[qtype]
+	return found
+}
+
+func dnsQtypeStringToValue(qtype string) uint16 {
+	x, found := dnsStringToType.Load(qtype)
+	if found {
+		return x.(uint16)
+	}
+
+	for k, v := range dns.TypeToString {
+		if v == qtype {
+			dnsStringToType.Store(qtype, k)
+			return k
+		}
+	}
+
+	log.Printf("qtype %#v is not known or found", qtype)
+	return dns.TypeNone
+}
+
+func dnsCustomResolve(qname string, qtype uint16) (*dns.Msg, error) {
+	qtype_s, known := dns.TypeToString[qtype]
+	if !known {
+		log.Printf("qtype is not known (%v) for %v", qtype, qname)
+		return nil, fmt.Errorf("qtype is not known: %v", qtype)
+	}
+
+	c := new(dns.Client)
+	c.Net = cfgResolverProto
+	c.Dialer = &net.Dialer{
+		Timeout: cfgResolverTimeout,
+	}
+
+	req := new(dns.Msg)
+	req.Id = dns.Id()
+	req.RecursionDesired = true
+	req.Question = make([]dns.Question, 1)
+	req.Question[0] = dns.Question{Name: qname, Qtype: qtype, Qclass: dns.ClassINET}
+
+	resp, rtt, err := c.Exchange(req, cfgResolverEndpoint)
+	if err != nil {
+		log.Printf("resolving %v/%v (rtt %v) with error: %v", qname, qtype_s, rtt, err)
+		return nil, err
+	}
+	log.Printf("resolved %v/%v (rtt %v)", qname, qtype_s, rtt)
+
+	return resp, nil
+}
+
+func dnsClipTtl(ttl uint32) uint32 {
+	if ttl < cfgTtlMin {
+		return cfgTtlMin
+	}
+	if ttl > cfgTtlMax {
+		return cfgTtlMax
+	}
+	return ttl
+}
+
+func randUint32(v uint32) uint32 {
+	if v < 2 {
+		return rand.Uint32()
+	}
+	return rand.Uint32() % v
+}
+
+func dnsFuzzClipTtl() uint32 {
+	return dnsClipTtl(cfgTtlMin + 1 + randUint32(dnsTtlRange*2) - dnsTtlRange)
+}
+
+type PowerDnsAnswer struct {
+	Qname   string `json:"qname"`
+	Qtype   string `json:"qtype"`
+	Ttl     uint32 `json:"ttl"`
+	Content string `json:"content"`
+}
+
+func dnsRrToPowerDnsAnswer(rr dns.RR) (PowerDnsAnswer, error) {
+	qname := rr.Header().Name
+
+	rrtype := rr.Header().Rrtype
+	qtype_s, ok := dns.TypeToString[rrtype]
+	if !ok {
+		return PowerDnsAnswer{}, fmt.Errorf("record %v: unknown rrtype: %v", qname, rrtype)
+	}
+
+	cont, ok := strings.CutPrefix(rr.String(), rr.Header().String())
+	if !ok {
+		return PowerDnsAnswer{}, fmt.Errorf("record %v/%v: unable to produce content", qname, qtype_s)
+	}
+
+	return PowerDnsAnswer{
+		Qname:   qname,
+		Qtype:   qtype_s,
+		Ttl:     dnsClipTtl(rr.Header().Ttl),
+		Content: strings.TrimSpace(cont),
+	}, nil
+}
+
+func dnsToPowerDnsAnswer(resp *dns.Msg) ([]PowerDnsAnswer, error) {
+	result := make([]PowerDnsAnswer, 0, len(resp.Answer)+len(resp.Extra))
+	for i := range resp.Answer {
+		r, err := dnsRrToPowerDnsAnswer(resp.Answer[i])
+		if err != nil {
+			log.Printf("%v", err)
+			continue
+		}
+		result = append(result, r)
+	}
+	for i := range resp.Extra {
+		r, err := dnsRrToPowerDnsAnswer(resp.Extra[i])
+		if err != nil {
+			log.Printf("%v", err)
+			continue
+		}
+		result = append(result, r)
+	}
+
+	return result, nil
+}