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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,80 @@ | ||
| package services | ||
|
|
||
| import ( | ||
| "fmt" | ||
| "net" | ||
| "runtime/debug" | ||
|
|
||
| "github.com/miekg/dns" | ||
| "github.com/pkg/errors" | ||
| "github.com/sirupsen/logrus" | ||
| ) | ||
|
|
||
| type DNSServer struct { | ||
| server *dns.Server | ||
| client *dns.Client | ||
| upstream []string | ||
| } | ||
|
|
||
| func NewDNSServer(upstream []string) (*DNSServer, error) { | ||
| logrus.Infof("starting dns server") | ||
| server := &dns.Server{Addr: "0.0.0.0:53", Net: "udp"} | ||
| client := &dns.Client{ | ||
| SingleInflight: true, | ||
| } | ||
| dnsServer := &DNSServer{server, client, upstream} | ||
| server.Handler = dnsServer | ||
| go func() { | ||
| if err := server.ListenAndServe(); err != nil { | ||
| logrus.Error(errors.Wrap(err, "failed to start dns server")) | ||
| } | ||
| }() | ||
| return dnsServer, nil | ||
| } | ||
|
|
||
| func (d *DNSServer) Close() error { | ||
| return d.server.Shutdown() | ||
| } | ||
|
|
||
| func (d *DNSServer) ServeDNS(w dns.ResponseWriter, r *dns.Msg) { | ||
| defer func() { | ||
| if err := recover(); err != nil { | ||
| logrus.Errorf("dns server panic handled: %v\n%s", err, string(debug.Stack())) | ||
| dns.HandleFailed(w, r) | ||
| } | ||
| }() | ||
| switch r.Opcode { | ||
| case dns.OpcodeQuery: | ||
| if logrus.GetLevel() == logrus.DebugLevel { | ||
| // log behind a condition to ensure we don't call prettyPrintMsg | ||
| // when the log level would filter out the message anyway | ||
| logrus.Debugf("dns query: %s", prettyPrintMsg(r)) | ||
| } | ||
| m, err := d.Lookup(r) | ||
| if err != nil { | ||
| logrus.Errorf("failed lookup record %s with error: %s\n", r, err.Error()) | ||
| m.SetReply(r) | ||
| w.WriteMsg(m) | ||
| return | ||
| } | ||
| m.SetReply(r) | ||
| w.WriteMsg(m) | ||
| return | ||
| } | ||
| } | ||
|
|
||
| func (d *DNSServer) Lookup(m *dns.Msg) (*dns.Msg, error) { | ||
| // TODO: add support for caching | ||
| response, _, err := d.client.Exchange(m, net.JoinHostPort(d.upstream[0], "53")) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| return response, nil | ||
| } | ||
|
|
||
| func prettyPrintMsg(m *dns.Msg) string { | ||
| if len(m.Question) > 0 { | ||
| return fmt.Sprintf("dns query for: %s", m.Question[0].Name) | ||
| } | ||
| return m.String() | ||
| } |
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