Include "svc" as a top-level domain in the DNS resolver.

It's not uncommon that use-cases involving Kafka or other middleware use
FQNs that end with "svc". The core-DNS resolver in Kubernetes can
resolve such names. With this bugfix, the Telepresence DNS resolver will
also be able to resolve them, and thereby remove the need to add ".svc"
to the include-suffix list

Closes #2814

Signed-off-by: Thomas Hallgren <[email protected]>

CHANGELOG.yml

@@ -33,6 +33,14 @@ items:
   - version: 2.19.0
     date: (TBD)
     notes:
+      - type: bugfix
+        title: Include svc as a top-level domain in the DNS resolver.
+        body: ->
+          It's not uncommon that use-cases involving Kafka or other middleware use FQNs that end with
+          "svc". The core-DNS resolver in Kubernetes can resolve such names. With this bugfix,
+          the Telepresence DNS resolver will also be able to resolve them, and thereby remove the need
+          to add ".svc" to the include-suffix list.
+        docs: https://github.com/telepresenceio/telepresence/issues/2814
       - type: feature
         title: Add ability to mount a webhook secret.
         body: >-

integration_test/svcdomain_test.go

@@ -0,0 +1,25 @@
+package integration_test
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"time"
+
+	"github.com/datawire/dlib/dlog"
+)
+
+func (s *connectedSuite) Test_SvcDomain() {
+	c := s.Context()
+	s.ApplyEchoService(c, "echo", 8080)
+	defer s.DeleteSvcAndWorkload(c, "deploy", "echo")
+
+	host := fmt.Sprintf("echo.%s.svc", s.AppNamespace())
+	s.Eventually(func() bool {
+		c, cancel := context.WithTimeout(c, 1800*time.Millisecond)
+		defer cancel()
+		dlog.Info(c, "LookupHost("+host+")")
+		_, err := net.DefaultResolver.LookupHost(c, host)
+		return s.NoErrorf(err, "%s did not resolve", host)
+	}, 10*time.Second, 2*time.Second)
+}

pkg/client/rootd/dns/server.go

@@ -308,6 +308,10 @@ func (s *Server) isExcluded(name string) bool {
 	return false
 }
 
+func (s *Server) isDomainExcluded(name string) bool {
+	return slices.Contains(s.excludeSuffixes, "."+name)
+}
+
 func (s *Server) resolveInCluster(c context.Context, q *dns.Question) (result dnsproxy.RRs, rCode int, err error) {
 	query := q.Name
 	if query == "localhost." {
@@ -515,10 +519,13 @@ func (s *Server) processSearchPaths(g *dgroup.Group, processor func(context.Cont
 
 				routes := make(map[string]struct{}, len(das.domains))
 				for _, domain := range das.domains {
-					if domain != "" {
+					if domain != "" && !s.isDomainExcluded(domain) {
 						routes[domain] = struct{}{}
 					}
 				}
+				if !s.isDomainExcluded("svc") {
+					routes["svc"] = struct{}{}
+				}
 				s.Lock()
 				s.routes = routes
 

pkg/client/userd/trafficmgr/session.go

@@ -10,6 +10,7 @@ import (
 	"net/url"
 	"os"
 	"os/user"
+	"slices"
 	"sort"
 	"strings"
 	"sync"
@@ -514,17 +515,20 @@ func connectError(t rpc.ConnectInfo_ErrType, err error) *rpc.ConnectInfo {
 // updateDaemonNamespacesLocked will create a new DNS search path from the given namespaces and
 // send it to the DNS-resolver in the daemon.
 func (s *session) updateDaemonNamespaces(c context.Context) {
+	const svcDomain = "svc"
+
 	s.wlWatcher.setNamespacesToWatch(c, s.GetCurrentNamespaces(true))
 
-	// Pass current mapped namespaces as plain names (no ending dot). The DNS-resolver will
-	// create special mapping for those, allowing names like myservice.mynamespace to be resolved
-	namespaces := s.GetCurrentNamespaces(false)
-	dlog.Debugf(c, "posting namespaces %v", namespaces)
+	domains := s.GetCurrentNamespaces(false)
+	if !slices.Contains(domains, svcDomain) {
+		domains = append(domains, svcDomain)
+	}
+	dlog.Debugf(c, "posting top-level domains %v to root daemon", domains)
 
-	if _, err := s.rootDaemon.SetDNSTopLevelDomains(c, &rootdRpc.Domains{Domains: namespaces}); err != nil {
-		dlog.Errorf(c, "error posting namespaces %v to root daemon: %v", namespaces, err)
+	if _, err := s.rootDaemon.SetDNSTopLevelDomains(c, &rootdRpc.Domains{Domains: domains}); err != nil {
+		dlog.Errorf(c, "error posting domains %v to root daemon: %v", domains, err)
 	}
-	dlog.Debug(c, "namespaces posted successfully")
+	dlog.Debug(c, "domains posted successfully")
 }
 
 func (s *session) Epilog(ctx context.Context) {