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Merge pull request Place1#10 from Place1/embedded-dns
Embedded dns
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,117 @@ | ||
| package services | ||
|
|
||
| import ( | ||
| "fmt" | ||
| "net" | ||
| "runtime/debug" | ||
| "time" | ||
|
|
||
| "github.com/miekg/dns" | ||
| "github.com/patrickmn/go-cache" | ||
| "github.com/pkg/errors" | ||
| "github.com/sirupsen/logrus" | ||
| ) | ||
|
|
||
| type DNSServer struct { | ||
| server *dns.Server | ||
| client *dns.Client | ||
| cache *cache.Cache | ||
| upstream []string | ||
| } | ||
|
|
||
| func NewDNSServer(upstream []string) (*DNSServer, error) { | ||
| logrus.Infof("starting dns server") | ||
|
|
||
| if len(upstream) == 0 { | ||
| upstream = []string{"1.1.1.1"} | ||
| } | ||
|
|
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| dnsServer := &DNSServer{ | ||
| server: &dns.Server{ | ||
| Addr: "0.0.0.0:53", | ||
| Net: "udp", | ||
| }, | ||
| client: &dns.Client{ | ||
| SingleInflight: true, | ||
| }, | ||
| cache: cache.New(10*time.Minute, 10*time.Minute), | ||
| upstream: upstream, | ||
| } | ||
| dnsServer.server.Handler = dnsServer | ||
|
|
||
| go func() { | ||
| if err := dnsServer.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 with error: %s\n%s", err.Error(), r) | ||
| dns.HandleFailed(w, r) | ||
| return | ||
| } | ||
| m.SetReply(r) | ||
| w.WriteMsg(m) | ||
| return | ||
| } | ||
| } | ||
|
|
||
| func (d *DNSServer) Lookup(m *dns.Msg) (*dns.Msg, error) { | ||
| key := makekey(m) | ||
|
|
||
| // check the cache first | ||
| if item, found := d.cache.Get(key); found { | ||
| if logrus.GetLevel() == logrus.DebugLevel { | ||
| logrus.Debugf("dns cache hit %s", prettyPrintMsg(m)) | ||
| } | ||
| return item.(*dns.Msg), nil | ||
| } | ||
|
|
||
| // fallback to upstream exchange | ||
| response, _, err := d.client.Exchange(m, net.JoinHostPort(d.upstream[0], "53")) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
|
||
| if len(response.Answer) > 0 { | ||
| ttl := time.Duration(response.Answer[0].Header().Ttl) * time.Second | ||
| logrus.Debugf("caching dns response for %v seconds", ttl) | ||
| d.cache.Set(key, response, ttl) | ||
| } | ||
|
|
||
| return response, nil | ||
| } | ||
|
|
||
| func makekey(m *dns.Msg) string { | ||
| q := m.Question[0] | ||
| return fmt.Sprintf("%s:%d:%d", q.Name, q.Qtype, q.Qclass) | ||
| } | ||
|
|
||
| func prettyPrintMsg(m *dns.Msg) string { | ||
| if len(m.Question) > 0 { | ||
| return fmt.Sprintf("dns query for: %s", makekey(m)) | ||
| } | ||
| return m.String() | ||
| } |
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