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Don't use coredns's resolver because it breaks when serving DNS-over-TLS

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This commit is contained in:
Eugene Bujak 2018-12-03 16:10:45 +03:00
parent 6bc70f49fc
commit bed242e786
1 changed files with 34 additions and 18 deletions
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52
coredns_plugin/coredns_plugin.go
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@ -17,7 +17,6 @@ import (
"github.com/coredns/coredns/plugin"
"github.com/coredns/coredns/plugin/metrics"
"github.com/coredns/coredns/plugin/pkg/dnstest"
"github.com/coredns/coredns/plugin/pkg/upstream"
"github.com/coredns/coredns/request"
"github.com/mholt/caddy"
"github.com/miekg/dns"
@ -57,7 +56,6 @@ type plugSettings struct {
type plug struct {
d *dnsfilter.Dnsfilter
Next plugin.Handler
upstream upstream.Upstream
settings plugSettings
sync.RWMutex
@ -205,11 +203,6 @@ func setupPlugin(c *caddy.Controller) (*plug, error) {
caddy.RegisterEventHook("dnsfilter-reload", hook)
})
p.upstream, err = upstream.New(nil)
if err != nil {
return nil, err
}
return p, nil
}
@ -318,6 +311,38 @@ 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) {
var records []dns.RR
var res *net.Resolver = nil // nil resolver is default resolver
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 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?
}
}
records = append(records, rr)
}
return records, nil
}
func (p *plug) replaceHostWithValAndReply(ctx context.Context, w dns.ResponseWriter, r *dns.Msg, host string, val string, question dns.Question) (int, error) {
// check if it's a domain name or IP address
addr := net.ParseIP(val)
@ -333,21 +358,12 @@ func (p *plug) replaceHostWithValAndReply(ctx context.Context, w dns.ResponseWri
records = append(records, result)
} else {
// this is a domain name, need to look it up
req := new(dns.Msg)
req.SetQuestion(dns.Fqdn(val), question.Qtype)
req.RecursionDesired = true
reqstate := request.Request{W: w, Req: req, Context: ctx}
result, err := p.upstream.Lookup(reqstate, dns.Fqdn(val), reqstate.QType())
var err error
records, err = lookupReplaced(dns.Fqdn(val), question.Name)
if err != nil {
log.Printf("Got error %s\n", err)
return dns.RcodeServerFailure, fmt.Errorf("plugin/dnsfilter: %s", err)
}
if result != nil {
for _, answer := range result.Answer {
answer.Header().Name = question.Name
}
records = result.Answer
}
}
m := new(dns.Msg)
m.SetReply(r)