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Merge pull request #2171 from thaJeztah/dont_give_up

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Handle NXDOMAIN, REFUSED and log errors
This commit is contained in:
Flavio Crisciani 2018-10-12 08:38:25 -07:00 committed by GitHub
commit cbf4d5ce89
1 changed files with 52 additions and 29 deletions
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81
libnetwork/resolver.go
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@ -111,7 +111,7 @@ func NewResolver(address string, proxyDNS bool, resolverKey string, backend DNSB
}
func (r *resolver) SetupFunc(port int) func() {
return (func() {
return func() {
var err error
// DNS operates primarily on UDP
@ -138,7 +138,7 @@ func (r *resolver) SetupFunc(port int) func() {
return
}
r.err = nil
})
}
}
func (r *resolver) Start() error {
@ -490,35 +490,51 @@ func (r *resolver) ServeDNS(w dns.ResponseWriter, query *dns.Msg) {
continue
}
r.forwardQueryEnd()
if resp != nil {
if resp.Rcode == dns.RcodeServerFailure {
// for Server Failure response, continue to the next external DNS server
logrus.Debugf("[resolver] external DNS %s:%s responded with ServFail for %q", proto, extDNS.IPStr, name)
continue
}
answers := 0
for _, rr := range resp.Answer {
h := rr.Header()
switch h.Rrtype {
case dns.TypeA:
answers++
ip := rr.(*dns.A).A
logrus.Debugf("[resolver] received A record %q for %q from %s:%s", ip, h.Name, proto, extDNS.IPStr)
r.backend.HandleQueryResp(h.Name, ip)
case dns.TypeAAAA:
answers++
ip := rr.(*dns.AAAA).AAAA
logrus.Debugf("[resolver] received AAAA record %q for %q from %s:%s", ip, h.Name, proto, extDNS.IPStr)
r.backend.HandleQueryResp(h.Name, ip)
}
}
if resp.Answer == nil || answers == 0 {
logrus.Debugf("[resolver] external DNS %s:%s did not return any %s records for %q", proto, extDNS.IPStr, queryType, name)
}
resp.Compress = true
} else {
if resp == nil {
logrus.Debugf("[resolver] external DNS %s:%s returned empty response for %q", proto, extDNS.IPStr, name)
break
}
switch resp.Rcode {
case dns.RcodeServerFailure, dns.RcodeRefused:
// Server returned FAILURE: continue with the next external DNS server
// Server returned REFUSED: this can be a transitional status, so continue with the next external DNS server
logrus.Debugf("[resolver] external DNS %s:%s responded with %s for %q", proto, extDNS.IPStr, statusString(resp.Rcode), name)
continue
case dns.RcodeNameError:
// Server returned NXDOMAIN. Stop resolution if it's an authoritative answer (see RFC 8020: https://tools.ietf.org/html/rfc8020#section-2)
logrus.Debugf("[resolver] external DNS %s:%s responded with %s for %q", proto, extDNS.IPStr, statusString(resp.Rcode), name)
if resp.Authoritative {
break
}
continue
case dns.RcodeSuccess:
// All is well
default:
// Server gave some error. Log the error, and continue with the next external DNS server
logrus.Debugf("[resolver] external DNS %s:%s responded with %s (code %d) for %q", proto, extDNS.IPStr, statusString(resp.Rcode), resp.Rcode, name)
continue
}
answers := 0
for _, rr := range resp.Answer {
h := rr.Header()
switch h.Rrtype {
case dns.TypeA:
answers++
ip := rr.(*dns.A).A
logrus.Debugf("[resolver] received A record %q for %q from %s:%s", ip, h.Name, proto, extDNS.IPStr)
r.backend.HandleQueryResp(h.Name, ip)
case dns.TypeAAAA:
answers++
ip := rr.(*dns.AAAA).AAAA
logrus.Debugf("[resolver] received AAAA record %q for %q from %s:%s", ip, h.Name, proto, extDNS.IPStr)
r.backend.HandleQueryResp(h.Name, ip)
}
}
if resp.Answer == nil || answers == 0 {
logrus.Debugf("[resolver] external DNS %s:%s did not return any %s records for %q", proto, extDNS.IPStr, queryType, name)
}
resp.Compress = true
break
}
if resp == nil {
@ -531,6 +547,13 @@ func (r *resolver) ServeDNS(w dns.ResponseWriter, query *dns.Msg) {
}
}
func statusString(responseCode int) string {
if s, ok := dns.RcodeToString[responseCode]; ok {
return s
}
return "UNKNOWN"
}
func (r *resolver) forwardQueryStart() bool {
r.queryLock.Lock()
defer r.queryLock.Unlock()