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libnetwork: some minor refactoring / cleanup
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- don't pass the query's quetion.name separately, as we're already
  passing the query itself.
- remove a "fallthrough" in favor of combining the cases in the switch

Signed-off-by: Sebastiaan van Stijn <[email protected]>
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@thaJeztah
thaJeztah committed Oct 15, 2021
1 parent d86a331 commit 79d6e93
Showing 1 changed file with 36 additions and 31 deletions.
67 changes: 36 additions & 31 deletions libnetwork/resolver.go
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Original file line number Diff line number Diff line change
Expand Up @@ -228,7 +228,8 @@ func createRespMsg(query *dns.Msg) *dns.Msg {
return resp
}

func (r *resolver) handleMXQuery(name string, query *dns.Msg) (*dns.Msg, error) {
func (r *resolver) handleMXQuery(query *dns.Msg) (*dns.Msg, error) {
name := query.Question[0].Name
addrv4, _ := r.backend.ResolveName(name, types.IPv4)
addrv6, _ := r.backend.ResolveName(name, types.IPv6)

Expand All @@ -244,9 +245,12 @@ func (r *resolver) handleMXQuery(name string, query *dns.Msg) (*dns.Msg, error)
return resp, nil
}

func (r *resolver) handleIPQuery(name string, query *dns.Msg, ipType int) (*dns.Msg, error) {
var addr []net.IP
var ipv6Miss bool
func (r *resolver) handleIPQuery(query *dns.Msg, ipType int) (*dns.Msg, error) {
var (
addr []net.IP
ipv6Miss bool
name = query.Question[0].Name
)
addr, ipv6Miss = r.backend.ResolveName(name, ipType)

if addr == nil && ipv6Miss {
Expand Down Expand Up @@ -283,8 +287,11 @@ func (r *resolver) handleIPQuery(name string, query *dns.Msg, ipType int) (*dns.
return resp, nil
}

func (r *resolver) handlePTRQuery(ptr string, query *dns.Msg) (*dns.Msg, error) {
var parts []string
func (r *resolver) handlePTRQuery(query *dns.Msg) (*dns.Msg, error) {
var (
parts []string
ptr = query.Question[0].Name
)

if strings.HasSuffix(ptr, ptrIPv4domain) {
parts = strings.Split(ptr, ptrIPv4domain)
Expand Down Expand Up @@ -314,8 +321,8 @@ func (r *resolver) handlePTRQuery(ptr string, query *dns.Msg) (*dns.Msg, error)
return resp, nil
}

func (r *resolver) handleSRVQuery(svc string, query *dns.Msg) (*dns.Msg, error) {

func (r *resolver) handleSRVQuery(query *dns.Msg) (*dns.Msg, error) {
svc := query.Question[0].Name
srv, ip := r.backend.ResolveService(svc)

if len(srv) == 0 {
Expand Down Expand Up @@ -371,25 +378,26 @@ func (r *resolver) ServeDNS(w dns.ResponseWriter, query *dns.Msg) {
return
}

name := query.Question[0].Name
switch query.Question[0].Qtype {
queryName := query.Question[0].Name
queryType := query.Question[0].Qtype

switch queryType {
case dns.TypeA:
resp, err = r.handleIPQuery(name, query, types.IPv4)
resp, err = r.handleIPQuery(query, types.IPv4)
case dns.TypeAAAA:
resp, err = r.handleIPQuery(name, query, types.IPv6)
resp, err = r.handleIPQuery(query, types.IPv6)
case dns.TypeMX:
resp, err = r.handleMXQuery(name, query)
resp, err = r.handleMXQuery(query)
case dns.TypePTR:
resp, err = r.handlePTRQuery(name, query)
resp, err = r.handlePTRQuery(query)
case dns.TypeSRV:
resp, err = r.handleSRVQuery(name, query)
resp, err = r.handleSRVQuery(query)
default:
queryType := dns.TypeToString[query.Question[0].Qtype]
logrus.Debugf("[resolver] query type %s is not supported by the embedded DNS and will be forwarded to external DNS", queryType)
logrus.Debugf("[resolver] query type %s is not supported by the embedded DNS and will be forwarded to external DNS", dns.TypeToString[queryType])
}

if err != nil {
logrus.WithError(err).Errorf("[resolver] failed to handle query: %s (%s) from %s", name, dns.TypeToString[query.Question[0].Qtype], extConn.LocalAddr().String())
logrus.WithError(err).Errorf("[resolver] failed to handle query: %s (%s) from %s", queryName, dns.TypeToString[queryType], extConn.LocalAddr().String())
return
}

Expand All @@ -409,11 +417,9 @@ func (r *resolver) ServeDNS(w dns.ResponseWriter, query *dns.Msg) {
// in the root domain don't forward it out. We will return
// failure and let the client retry with the search domain
// attached
switch query.Question[0].Qtype {
case dns.TypeA:
fallthrough
case dns.TypeAAAA:
if r.backend.NdotsSet() && !strings.Contains(strings.TrimSuffix(name, "."), ".") {
switch queryType {
case dns.TypeA, dns.TypeAAAA:
if r.backend.NdotsSet() && !strings.Contains(strings.TrimSuffix(queryName, "."), ".") {
resp = createRespMsg(query)
}
}
Expand Down Expand Up @@ -461,8 +467,7 @@ func (r *resolver) ServeDNS(w dns.ResponseWriter, query *dns.Msg) {
logrus.WithField("retries", i).Warnf("[resolver] connect failed: %s", err)
continue
}
queryType := dns.TypeToString[query.Question[0].Qtype]
logrus.Debugf("[resolver] query %s (%s) from %s, forwarding to %s:%s", name, queryType,
logrus.Debugf("[resolver] query %s (%s) from %s, forwarding to %s:%s", queryName, dns.TypeToString[queryType],
extConn.LocalAddr().String(), proto, extDNS.IPStr)

// Timeout has to be set for every IO operation.
Expand Down Expand Up @@ -503,18 +508,18 @@ func (r *resolver) ServeDNS(w dns.ResponseWriter, query *dns.Msg) {
r.forwardQueryEnd()

if resp == nil {
logrus.Debugf("[resolver] external DNS %s:%s returned empty response for %q", proto, extDNS.IPStr, name)
logrus.Debugf("[resolver] external DNS %s:%s returned empty response for %q", proto, extDNS.IPStr, queryName)
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)
logrus.Debugf("[resolver] external DNS %s:%s responded with %s for %q", proto, extDNS.IPStr, statusString(resp.Rcode), queryName)
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)
logrus.Debugf("[resolver] external DNS %s:%s responded with %s for %q", proto, extDNS.IPStr, statusString(resp.Rcode), queryName)
if resp.Authoritative {
break
}
Expand All @@ -523,7 +528,7 @@ func (r *resolver) ServeDNS(w dns.ResponseWriter, query *dns.Msg) {
// 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)
logrus.Debugf("[resolver] external DNS %s:%s responded with %s (code %d) for %q", proto, extDNS.IPStr, statusString(resp.Rcode), resp.Rcode, queryName)
continue
}
answers := 0
Expand All @@ -543,7 +548,7 @@ func (r *resolver) ServeDNS(w dns.ResponseWriter, query *dns.Msg) {
}
}
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)
logrus.Debugf("[resolver] external DNS %s:%s did not return any %s records for %q", proto, extDNS.IPStr, dns.TypeToString[queryType], queryName)
}
resp.Compress = true
break
Expand All @@ -554,7 +559,7 @@ func (r *resolver) ServeDNS(w dns.ResponseWriter, query *dns.Msg) {
}

if err = w.WriteMsg(resp); err != nil {
logrus.WithError(err).Errorf("[resolver] failed to write resolver response")
logrus.WithError(err).Errorf("[resolver] failed to write response")
}
}

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