Add coredns entries for nodes

manifests/coredns.yaml

@@ -60,6 +60,10 @@ data:
           upstream
           fallthrough in-addr.arpa ip6.arpa
         }
+        hosts /etc/coredns/NodeHosts {
+          reload 1s
+          fallthrough
+        }
         prometheus :9153
         proxy . /etc/resolv.conf
         cache 30
@@ -146,6 +150,8 @@ spec:
             items:
             - key: Corefile
               path: Corefile
+            - key: NodeHosts
+              path: NodeHosts
 ---
 apiVersion: v1
 kind: Service

pkg/node/controller.go

@@ -0,0 +1,115 @@
+package node
+
+import (
+	"context"
+	"strings"
+
+	"github.com/pkg/errors"
+	coreclient "github.com/rancher/k3s/types/apis/core/v1"
+	"github.com/sirupsen/logrus"
+	core "k8s.io/api/core/v1"
+	"k8s.io/apimachinery/pkg/runtime"
+)
+
+func Register(ctx context.Context) error {
+	clients := coreclient.ClientsFrom(ctx)
+	h := &handler{
+		configCache:  clients.ConfigMap.Cache(),
+		configClient: clients.ConfigMap,
+	}
+	clients.Node.OnCreate(ctx, "node", h.onChange)
+	clients.Node.OnChange(ctx, "node", h.onChange)
+	clients.Node.OnRemove(ctx, "node", h.onRemove)
+
+	return nil
+}
+
+type handler struct {
+	configCache  coreclient.ConfigMapClientCache
+	configClient coreclient.ConfigMapClient
+}
+
+func (h *handler) onChange(node *core.Node) (runtime.Object, error) {
+	return h.updateHosts(node, false)
+}
+
+func (h *handler) onRemove(node *core.Node) (runtime.Object, error) {
+	return h.updateHosts(node, true)
+}
+
+func (h *handler) updateHosts(node *core.Node, removed bool) (runtime.Object, error) {
+	var (
+		newHosts    string
+		nodeUID     string
+		nodeAddress string
+		nodeEntry   string
+		uidHostsMap map[string]string
+	)
+	nodeUID = string(node.UID)
+	uidHostsMap = make(map[string]string)
+
+	for _, address := range node.Status.Addresses {
+		if address.Type == "InternalIP" {
+			nodeAddress = address.Address
+			break
+		}
+	}
+	if nodeAddress == "" {
+		logrus.Errorf("No InternalIP found for node %s", node.Name)
+		return nil, nil
+	}
+	nodeEntry = nodeAddress + " " + node.Name
+
+	configMap, err := h.configCache.Get("kube-system", "coredns")
+	if err != nil || configMap == nil {
+		logrus.Warn(errors.Wrap(err, "Unable to fetch coredns config map"))
+		return nil, nil
+	}
+
+	hosts := configMap.Data["NodeHosts"]
+	for _, line := range strings.Split(hosts, "\n") {
+		if line == "" {
+			continue
+		}
+		fields := strings.Fields(line)
+		if len(fields) != 4 || fields[2] != "#" {
+			logrus.Warnf("Unknown format for hosts line [%s]", line)
+			continue
+		}
+		ip := fields[0]
+		host := fields[1]
+		uid := fields[3]
+		hostEntry := ip + " " + host
+		if uid == nodeUID {
+			if removed {
+				continue
+			}
+			if hostEntry == nodeEntry {
+				return nil, nil
+			}
+		}
+		uidHostsMap[uid] = hostEntry
+	}
+
+	if !removed {
+		uidHostsMap[nodeUID] = nodeEntry
+	}
+	for uid, hostEntry := range uidHostsMap {
+		newHosts += hostEntry + " # " + uid + "\n"
+	}
+	configMap.Data["NodeHosts"] = newHosts
+
+	if _, err := h.configClient.Update(configMap); err != nil {
+		return nil, err
+	}
+
+	var actionType string
+	if removed {
+		actionType = "Removed"
+	} else {
+		actionType = "Updated"
+	}
+	logrus.Infof("%s coredns node hosts entry [%s]", actionType, nodeEntry)
+
+	return nil, nil
+}

pkg/server/server.go

@@ -18,6 +18,7 @@ import (
 	"github.com/rancher/k3s/pkg/datadir"
 	"github.com/rancher/k3s/pkg/deploy"
 	"github.com/rancher/k3s/pkg/helm"
+	"github.com/rancher/k3s/pkg/node"
 	"github.com/rancher/k3s/pkg/rootlessports"
 	"github.com/rancher/k3s/pkg/servicelb"
 	"github.com/rancher/k3s/pkg/static"
@@ -112,6 +113,7 @@ func startNorman(ctx context.Context, config *Config) (string, error) {
 		},
 		DisableLeaderElection: true,
 		MasterControllers: []norman.ControllerRegister{
+			node.Register,
 			helm.Register,
 			func(ctx context.Context) error {
 				return servicelb.Register(ctx, norman.GetServer(ctx).K8sClient, !config.DisableServiceLB,