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Handle DNS Rcodes

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This commit is contained in:
Daniel 2020-09-25 10:13:10 +02:00
parent 00de73d65e
commit 4e14439112
8 changed files with 53 additions and 22 deletions
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39
resolver/rrcache.go
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@ -22,6 +22,7 @@ type RRCache struct {
Domain string // constant
Question dns.Type // constant
RCode int // constant
Answer []dns.RR // constant
Ns []dns.RR // constant
@ -84,8 +85,8 @@ func (rrCache *RRCache) Clean(minExpires uint32) {
// shorten caching
switch {
case rrCache.IsNXDomain():
// NXDomain
case rrCache.RCode != dns.RcodeSuccess:
// Any sort of error.
lowestTTL = 10
case netenv.IsConnectivityDomain(rrCache.Domain):
// Responses from these domains might change very quickly depending on the environment.
@ -127,6 +128,7 @@ func (rrCache *RRCache) ToNameRecord() *NameRecord {
new := &NameRecord{
Domain: rrCache.Domain,
Question: rrCache.Question.String(),
RCode: rrCache.RCode,
TTL: rrCache.TTL,
Server: rrCache.Server,
ServerScope: rrCache.ServerScope,
@ -147,8 +149,27 @@ func (rrCache *RRCache) ToNameRecord() *NameRecord {
return new
}
// rcodeIsCacheable returns whether a record with the given RCode should be cached.
func rcodeIsCacheable(rCode int) bool {
switch rCode {
case dns.RcodeSuccess, dns.RcodeNameError, dns.RcodeRefused:
return true
default:
return false
}
}
// Cacheable returns whether the record should be cached.
func (rrCache *RRCache) Cacheable() bool {
return rcodeIsCacheable(rrCache.RCode)
}
// Save saves the RRCache to the database as a NameRecord.
func (rrCache *RRCache) Save() error {
if !rrCache.Cacheable() {
return nil
}
return rrCache.ToNameRecord().Save()
}
@ -164,6 +185,7 @@ func GetRRCache(domain string, question dns.Type) (*RRCache, error) {
return nil, err
}
rrCache.RCode = nameRecord.RCode
rrCache.TTL = nameRecord.TTL
for _, entry := range nameRecord.Answer {
rrCache.Answer = parseRR(rrCache.Answer, entry)
@ -227,16 +249,12 @@ func (rrCache *RRCache) Flags() string {
return ""
}
// IsNXDomain returnes whether the result is nxdomain.
func (rrCache *RRCache) IsNXDomain() bool {
return len(rrCache.Answer) == 0
}
// ShallowCopy returns a shallow copy of the cache. slices are not copied, but referenced.
func (rrCache *RRCache) ShallowCopy() *RRCache {
return &RRCache{
Domain: rrCache.Domain,
Question: rrCache.Question,
RCode: rrCache.RCode,
Answer: rrCache.Answer,
Ns: rrCache.Ns,
Extra: rrCache.Extra,
@ -259,14 +277,11 @@ func (rrCache *RRCache) ShallowCopy() *RRCache {
func (rrCache *RRCache) ReplyWithDNS(ctx context.Context, request *dns.Msg) *dns.Msg {
// reply to query
reply := new(dns.Msg)
reply.SetRcode(request, dns.RcodeSuccess)
reply.SetRcode(request, rrCache.RCode)
reply.Ns = rrCache.Ns
reply.Extra = rrCache.Extra
if rrCache.IsNXDomain() {
// Set NXDomain return code if not the reply has no answers.
reply.Rcode = dns.RcodeNameError
} else {
if len(rrCache.Answer) > 0 {
// Copy answers, as we randomize their order a little.
reply.Answer = make([]dns.RR, len(rrCache.Answer))
copy(reply.Answer, rrCache.Answer)