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Nino-KNino-K
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lookup internal cnames for TypeA
Signed-off-by: Nino Kodabande <[email protected]>
1 parent 7e1268e commit 6998600

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1 file changed

+66
-53
lines changed

1 file changed

+66
-53
lines changed

‎pkg/hostagent/dns/dns.go

Lines changed: 66 additions & 53 deletions
Original file line numberDiff line numberDiff line change
@@ -19,6 +19,13 @@ const truncateSize = 512
1919

2020
var defaultFallbackIPs = []string{"8.8.8.8", "1.1.1.1"}
2121

22+
type Network string
23+
24+
const (
25+
TCP Network = "tcp"
26+
UDP Network = "udp"
27+
)
28+
2229
type HandlerOptions struct {
2330
IPv6 bool
2431
StaticHosts map[string]string
@@ -57,7 +64,7 @@ func (s *Server) Shutdown() {
5764
}
5865

5966
func newStaticClientConfig(ips []string) (*dns.ClientConfig, error) {
60-
logrus.Infof("newStaticClientConfig creating config for the the following IPs: %v", ips)
67+
logrus.Debugf("newStaticClientConfig creating config for the the following IPs: %v", ips)
6168
s := ``
6269
for _, ip := range ips {
6370
s += fmt.Sprintf("nameserver %s\n", ip)
@@ -66,6 +73,23 @@ func newStaticClientConfig(ips []string) (*dns.ClientConfig, error) {
6673
return dns.ClientConfigFromReader(r)
6774
}
6875

76+
func (h *Handler) lookupCnameToHost(cname string) string {
77+
seen := make(map[string]bool)
78+
for {
79+
// break cyclic definition
80+
if seen[cname] {
81+
break
82+
}
83+
if _, ok := h.cnameToHost[cname]; ok {
84+
seen[cname] = true
85+
cname = h.cnameToHost[cname]
86+
continue
87+
}
88+
break
89+
}
90+
return cname
91+
}
92+
6993
func NewHandler(opts HandlerOptions) (dns.Handler, error) {
7094
var cc *dns.ClientConfig
7195
var err error
@@ -89,6 +113,7 @@ func NewHandler(opts HandlerOptions) (dns.Handler, error) {
89113
}
90114
} else {
91115
if cc, err = newStaticClientConfig(opts.UpstreamServers); err != nil {
116+
logrus.WithError(err).Warnf("failed to create a client config from: %v, falling back to %v", opts.UpstreamServers, defaultFallbackIPs)
92117
if cc, err = newStaticClientConfig(defaultFallbackIPs); err != nil {
93118
return nil, err
94119
}
@@ -147,12 +172,13 @@ func (h *Handler) handleQuery(w dns.ResponseWriter, req *dns.Msg) {
147172
case dns.TypeA:
148173
var err error
149174
var addrs []net.IP
150-
if _, ok := h.hostToIP[q.Name]; ok {
151-
addrs = []net.IP{h.hostToIP[q.Name]}
175+
cname := h.lookupCnameToHost(q.Name)
176+
if _, ok := h.hostToIP[cname]; ok {
177+
addrs = []net.IP{h.hostToIP[cname]}
152178
} else {
153-
addrs, err = net.LookupIP(q.Name)
179+
addrs, err = net.LookupIP(cname)
154180
if err != nil {
155-
logrus.Debugf("handleQuery lookup IP failed: %v", err)
181+
logrus.WithError(err).Debug("handleQuery lookup IP failed")
156182
continue
157183
}
158184
}
@@ -178,25 +204,12 @@ func (h *Handler) handleQuery(w dns.ResponseWriter, req *dns.Msg) {
178204
handled = true
179205
}
180206
case dns.TypeCNAME:
181-
cname := q.Name
182-
seen := make(map[string]bool)
183-
for {
184-
// break cyclic definition
185-
if seen[cname] {
186-
break
187-
}
188-
if _, ok := h.cnameToHost[cname]; ok {
189-
seen[cname] = true
190-
cname = h.cnameToHost[cname]
191-
continue
192-
}
193-
break
194-
}
207+
cname := h.lookupCnameToHost(q.Name)
195208
var err error
196209
if _, ok := h.hostToIP[cname]; !ok {
197210
cname, err = net.LookupCNAME(cname)
198211
if err != nil {
199-
logrus.Debugf("handleQuery lookup CNAME failed: %v", err)
212+
logrus.WithError(err).Debug("handleQuery lookup CNAME failed")
200213
continue
201214
}
202215
}
@@ -212,7 +225,7 @@ func (h *Handler) handleQuery(w dns.ResponseWriter, req *dns.Msg) {
212225
case dns.TypeTXT:
213226
txt, err := net.LookupTXT(q.Name)
214227
if err != nil {
215-
logrus.Debugf("handleQuery lookup TXT failed: %v", err)
228+
logrus.WithError(err).Debug("handleQuery lookup TXT failed")
216229
continue
217230
}
218231
for _, s := range txt {
@@ -229,7 +242,7 @@ func (h *Handler) handleQuery(w dns.ResponseWriter, req *dns.Msg) {
229242
case dns.TypeNS:
230243
ns, err := net.LookupNS(q.Name)
231244
if err != nil {
232-
logrus.Debugf("handleQuery lookup NS failed: %v", err)
245+
logrus.WithError(err).Debug("handleQuery lookup NS failed")
233246
continue
234247
}
235248
for _, s := range ns {
@@ -245,7 +258,7 @@ func (h *Handler) handleQuery(w dns.ResponseWriter, req *dns.Msg) {
245258
case dns.TypeMX:
246259
mx, err := net.LookupMX(q.Name)
247260
if err != nil {
248-
logrus.Debugf("handleQuery lookup MX failed: %v", err)
261+
logrus.WithError(err).Debugf("handleQuery lookup MX failed")
249262
continue
250263
}
251264
for _, s := range mx {
@@ -262,7 +275,7 @@ func (h *Handler) handleQuery(w dns.ResponseWriter, req *dns.Msg) {
262275
case dns.TypeSRV:
263276
_, addrs, err := net.LookupSRV("", "", q.Name)
264277
if err != nil {
265-
logrus.Debugf("handleQuery lookup SRV failed: %v", err)
278+
logrus.WithError(err).Debug("handleQuery lookup SRV failed")
266279
continue
267280
}
268281
hdr.Rrtype = dns.TypeSRV
@@ -284,7 +297,7 @@ func (h *Handler) handleQuery(w dns.ResponseWriter, req *dns.Msg) {
284297
reply.Truncate(truncateSize)
285298
}
286299
if err := w.WriteMsg(&reply); err != nil {
287-
logrus.Debugf("handleQuery failed writing DNS reply: %v", err)
300+
logrus.WithError(err).Debugf("handleQuery failed writing DNS reply")
288301
}
289302

290303
return
@@ -299,15 +312,15 @@ func (h *Handler) handleDefault(w dns.ResponseWriter, req *dns.Msg) {
299312
addr := fmt.Sprintf("%s:%s", srv, h.clientConfig.Port)
300313
reply, _, err := client.Exchange(req, addr)
301314
if err != nil {
302-
logrus.Debugf("handleDefault failed to perform a synchronous query with upstream [%v]: %v", addr, err)
315+
logrus.WithError(err).Debugf("handleDefault failed to perform a synchronous query with upstream [%v]", addr)
303316
continue
304317
}
305318
if h.truncate {
306319
logrus.Debugf("handleDefault truncating reply: %v", reply)
307320
reply.Truncate(truncateSize)
308321
}
309322
if err = w.WriteMsg(reply); err != nil {
310-
logrus.Debugf("handleDefault failed writing DNS reply to [%v]: %v", addr, err)
323+
logrus.WithError(err).Debugf("handleDefault failed writing DNS reply to [%v]", addr)
311324
}
312325
return
313326
}
@@ -319,7 +332,7 @@ func (h *Handler) handleDefault(w dns.ResponseWriter, req *dns.Msg) {
319332
reply.Truncate(truncateSize)
320333
}
321334
if err := w.WriteMsg(&reply); err != nil {
322-
logrus.Debugf("handleDefault failed writing DNS reply: %v", err)
335+
logrus.WithError(err).Debugf("handleDefault failed writing DNS reply")
323336
}
324337
}
325338

@@ -335,43 +348,43 @@ func (h *Handler) ServeDNS(w dns.ResponseWriter, req *dns.Msg) {
335348
func Start(opts ServerOptions) (*Server, error) {
336349
server := &Server{}
337350
if opts.UDPPort > 0 {
338-
udpOpts := opts
339-
// always enable reply truncate for UDP
340-
udpOpts.TruncateReply = true
341-
h, err := NewHandler(udpOpts.HandlerOptions)
351+
udpSrv, err := listenAndServe(UDP, opts)
342352
if err != nil {
343353
return nil, err
344354
}
345-
addr := fmt.Sprintf("%s:%d", opts.Address, opts.UDPPort)
346-
s := &dns.Server{Net: "udp", Addr: addr, Handler: h}
347-
server.udp = s
348-
go func() {
349-
logrus.Debugf("Start UDP server listening on: %v", addr)
350-
if e := s.ListenAndServe(); e != nil {
351-
panic(e)
352-
}
353-
}()
355+
server.udp = udpSrv
354356
}
355357
if opts.TCPPort > 0 {
356-
tcpOpts := opts
357-
tcpOpts.TruncateReply = false
358-
h, err := NewHandler(tcpOpts.HandlerOptions)
358+
tcpSrv, err := listenAndServe(TCP, opts)
359359
if err != nil {
360360
return nil, err
361361
}
362-
addr := fmt.Sprintf("%s:%d", opts.Address, opts.TCPPort)
363-
s := &dns.Server{Net: "tcp", Addr: addr, Handler: h}
364-
server.tcp = s
365-
go func() {
366-
logrus.Debugf("Start TCP server listening on: %v", addr)
367-
if e := s.ListenAndServe(); e != nil {
368-
panic(e)
369-
}
370-
}()
362+
server.tcp = tcpSrv
371363
}
372364
return server, nil
373365
}
374366

367+
func listenAndServe(network Network, opts ServerOptions) (*dns.Server, error) {
368+
// always enable reply truncate for UDP
369+
if network == UDP {
370+
opts.TruncateReply = true
371+
}
372+
h, err := NewHandler(opts.HandlerOptions)
373+
if err != nil {
374+
return nil, err
375+
}
376+
addr := fmt.Sprintf("%s:%d", opts.Address, opts.UDPPort)
377+
s := &dns.Server{Net: string(network), Addr: addr, Handler: h}
378+
go func() {
379+
logrus.Debugf("Start UDP server listening on: %v", addr)
380+
if e := s.ListenAndServe(); e != nil {
381+
panic(e)
382+
}
383+
}()
384+
385+
return s, nil
386+
}
387+
375388
func chunkify(buffer string, limit int) []string {
376389
var result []string
377390
for len(buffer) > 0 {

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