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Lookup replacement -- do it only for A and AAAA, and keep only respective types in.

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This commit is contained in:
Eugene Bujak 2018-12-03 18:55:17 +03:00
parent d54fd77204
commit 6bf1e2f7b5
1 changed files with 31 additions and 25 deletions
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44
coredns_plugin/coredns_plugin.go
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@ -285,35 +285,41 @@ func (p *plug) Collect(ch chan<- prometheus.Metric) {
p.doStats(ch, doMetric)
}
// lookup host, but return answer as if it was a result of origname lookup
func lookupReplaced(host string, origname string) ([]dns.RR, error) {
// lookup host, but return answer as if it was a result of different lookup
// TODO: works only on A and AAAA, the go stdlib resolver can't do arbitrary types
func lookupReplaced(host string, question dns.Question) ([]dns.RR, error) {
var records []dns.RR
var res *net.Resolver // nil resolver is default resolver
switch question.Qtype {
case dns.TypeA:
addrs, err := res.LookupIPAddr(context.TODO(), host)
if err != nil {
return nil, err
}
for _, addr := range addrs {
ip := addr.IP
var rr dns.RR
var err error
if ip.To4() != nil {
// ipv4 -> A
rr, err = dns.NewRR(fmt.Sprintf("%s A %s", origname, ip.String()))
if addr.IP.To4() != nil {
rr, err := dns.NewRR(fmt.Sprintf("%s A %s", question.Name, addr.IP.String()))
if err != nil {
return nil, err // fail entire request
// TODO: return only successful answers?
}
} else {
// ipv6 -> AAAA
rr, err = dns.NewRR(fmt.Sprintf("%s AAAA %s", origname, ip.String()))
if err != nil {
return nil, err // fail entire request
// TODO: return only successful answers?
}
return nil, err // fail entire request, TODO: return partial request?
}
records = append(records, rr)
}
}
case dns.TypeAAAA:
addrs, err := res.LookupIPAddr(context.TODO(), host)
if err != nil {
return nil, err
}
for _, addr := range addrs {
if addr.IP.To4() == nil {
rr, err := dns.NewRR(fmt.Sprintf("%s AAAA %s", question.Name, addr.IP.String()))
if err != nil {
return nil, err // fail entire request, TODO: return partial request?
}
records = append(records, rr)
}
}
}
return records, nil
}
@ -333,7 +339,7 @@ func (p *plug) replaceHostWithValAndReply(ctx context.Context, w dns.ResponseWri
} else {
// this is a domain name, need to look it up
var err error
records, err = lookupReplaced(dns.Fqdn(val), question.Name)
records, err = lookupReplaced(dns.Fqdn(val), question)
if err != nil {
log.Printf("Got error %s\n", err)
return dns.RcodeServerFailure, fmt.Errorf("plugin/dnsfilter: %s", err)