TUN-5675: Remove github.com/dgrijalva/jwt-go dependency by upgrading coredns version

vendor/google.golang.org/grpc/internal/resolver/dns/dns_resolver.go

@@ -34,6 +34,7 @@ import (
 
 	grpclbstate "google.golang.org/grpc/balancer/grpclb/state"
 	"google.golang.org/grpc/grpclog"
+	"google.golang.org/grpc/internal/backoff"
 	"google.golang.org/grpc/internal/envconfig"
 	"google.golang.org/grpc/internal/grpcrand"
 	"google.golang.org/grpc/resolver"
@@ -46,6 +47,13 @@ var EnableSRVLookups = false
 
 var logger = grpclog.Component("dns")
 
+// Globals to stub out in tests. TODO: Perhaps these two can be combined into a
+// single variable for testing the resolver?
+var (
+	newTimer           = time.NewTimer
+	newTimerDNSResRate = time.NewTimer
+)
+
 func init() {
 	resolver.Register(NewBuilder())
 }
@@ -143,7 +151,6 @@ func (b *dnsBuilder) Build(target resolver.Target, cc resolver.ClientConn, opts
 
 	d.wg.Add(1)
 	go d.watcher()
-	d.ResolveNow(resolver.ResolveNowOptions{})
 	return d, nil
 }
 
@@ -201,28 +208,38 @@ func (d *dnsResolver) Close() {
 
 func (d *dnsResolver) watcher() {
 	defer d.wg.Done()
+	backoffIndex := 1
 	for {
-		select {
-		case <-d.ctx.Done():
-			return
-		case <-d.rn:
-		}
-
 		state, err := d.lookup()
 		if err != nil {
+			// Report error to the underlying grpc.ClientConn.
 			d.cc.ReportError(err)
 		} else {
-			d.cc.UpdateState(*state)
+			err = d.cc.UpdateState(*state)
 		}
 
-		// Sleep to prevent excessive re-resolutions. Incoming resolution requests
-		// will be queued in d.rn.
-		t := time.NewTimer(minDNSResRate)
+		var timer *time.Timer
+		if err == nil {
+			// Success resolving, wait for the next ResolveNow. However, also wait 30 seconds at the very least
+			// to prevent constantly re-resolving.
+			backoffIndex = 1
+			timer = newTimerDNSResRate(minDNSResRate)
+			select {
+			case <-d.ctx.Done():
+				timer.Stop()
+				return
+			case <-d.rn:
+			}
+		} else {
+			// Poll on an error found in DNS Resolver or an error received from ClientConn.
+			timer = newTimer(backoff.DefaultExponential.Backoff(backoffIndex))
+			backoffIndex++
+		}
 		select {
-		case <-t.C:
 		case <-d.ctx.Done():
-			t.Stop()
+			timer.Stop()
 			return
+		case <-timer.C:
 		}
 	}
 }
@@ -260,18 +277,13 @@ func (d *dnsResolver) lookupSRV() ([]resolver.Address, error) {
 	return newAddrs, nil
 }
 
-var filterError = func(err error) error {
+func handleDNSError(err error, lookupType string) error {
 	if dnsErr, ok := err.(*net.DNSError); ok && !dnsErr.IsTimeout && !dnsErr.IsTemporary {
 		// Timeouts and temporary errors should be communicated to gRPC to
 		// attempt another DNS query (with backoff).  Other errors should be
 		// suppressed (they may represent the absence of a TXT record).
 		return nil
 	}
-	return err
-}
-
-func handleDNSError(err error, lookupType string) error {
-	err = filterError(err)
 	if err != nil {
 		err = fmt.Errorf("dns: %v record lookup error: %v", lookupType, err)
 		logger.Info(err)
@@ -306,12 +318,12 @@ func (d *dnsResolver) lookupTXT() *serviceconfig.ParseResult {
 }
 
 func (d *dnsResolver) lookupHost() ([]resolver.Address, error) {
-	var newAddrs []resolver.Address
 	addrs, err := d.resolver.LookupHost(d.ctx, d.host)
 	if err != nil {
 		err = handleDNSError(err, "A")
 		return nil, err
 	}
+	newAddrs := make([]resolver.Address, 0, len(addrs))
 	for _, a := range addrs {
 		ip, ok := formatIP(a)
 		if !ok {

vendor/google.golang.org/grpc/internal/resolver/dns/go113.go

@@ -1,33 +0,0 @@
-// +build go1.13
-
-/*
- *
- * Copyright 2019 gRPC authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-package dns
-
-import "net"
-
-func init() {
-	filterError = func(err error) error {
-		if dnsErr, ok := err.(*net.DNSError); ok && dnsErr.IsNotFound {
-			// The name does not exist; not an error.
-			return nil
-		}
-		return err
-	}
-}