From 6cc3f47d466b7c6dda57d4fb8abb784dd278c495 Mon Sep 17 00:00:00 2001
From: Miek Gieben <miek@miek.nl>
Date: Thu, 10 Aug 2017 19:26:31 +0100
Subject: [PATCH] middleware/authpath: Fix return from k8s mw (#871)

* middleware/authpath: Fix return from k8s mw

Return the correct search path from the kubernetes' AutoPath function.
Based on preliminary discussion in #870

* PodWithIP can be private

Fix and add docs to functions.

* CR: remove the error from AutoPathFunc
---
 middleware/autopath/autopath.go     | 12 ++++-----
 middleware/kubernetes/autopath.go   | 42 +++++++++++++++++++----------
 middleware/kubernetes/kubernetes.go |  1 +
 middleware/kubernetes/setup.go      | 11 ++++++++
 4 files changed, 46 insertions(+), 20 deletions(-)

diff --git a/middleware/autopath/autopath.go b/middleware/autopath/autopath.go
index 31e8afd6d..ecbdf0464 100644
--- a/middleware/autopath/autopath.go
+++ b/middleware/autopath/autopath.go
@@ -27,8 +27,8 @@ AutoPathFunc. Note the searchpath must be ending with the empty string.
 
 I.e:
 
-func (m Middleware ) AutoPath(state request.Request) ([]string, error) {
-	return []string{"first", "second", "last", ""}, nil
+func (m Middleware ) AutoPath(state request.Request) []string {
+	return []string{"first", "second", "last", ""}
 }
 */
 
@@ -45,8 +45,8 @@ import (
 
 // AutoPathFunc defines the function middleware should implement to return a search
 // path to the autopath middleware. The last element of the slice must be the empty string.
-// If AutoPathFunc returns a non-nil error no autopathing is performed.
-type AutoPathFunc func(request.Request) ([]string, error)
+// If AutoPathFunc returns a nil slice, no autopathing will be done.
+type AutoPathFunc func(request.Request) []string
 
 // Autopath perform autopath: service side search path completion.
 type AutoPath struct {
@@ -69,8 +69,8 @@ func (a *AutoPath) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Ms
 	var err error
 	searchpath := a.search
 	if a.searchFunc != nil {
-		searchpath, err = a.searchFunc(state)
-		if err != nil {
+		searchpath = a.searchFunc(state)
+		if len(searchpath) == 0 {
 			return middleware.NextOrFailure(a.Name(), a.Next, ctx, w, r)
 		}
 	}
diff --git a/middleware/kubernetes/autopath.go b/middleware/kubernetes/autopath.go
index 4c5870c6b..be71ce326 100644
--- a/middleware/kubernetes/autopath.go
+++ b/middleware/kubernetes/autopath.go
@@ -1,32 +1,46 @@
 package kubernetes
 
 import (
-	"fmt"
-
+	"github.com/coredns/coredns/middleware"
 	"github.com/coredns/coredns/request"
 
 	"k8s.io/client-go/1.5/pkg/api"
 )
 
-func (k *Kubernetes) AutoPath(state request.Request) ([]string, error) {
-	ip := state.IP()
-
-	pod := k.PodWithIP(ip)
-	if pod == nil {
-		return nil, fmt.Errorf("kubernets: no pod found for %s", ip)
+// AutoPath implements the AutoPathFunc call from the autopath middleware.
+// It returns a per-query search path or nil indicating no searchpathing should happen.
+func (k *Kubernetes) AutoPath(state request.Request) []string {
+	// Check if the query falls in a zone we are actually authoriative for and thus if we want autopath.
+	zone := middleware.Zones(k.Zones).Matches(state.Name())
+	if zone == "" {
+		return nil
 	}
 
-	// something something namespace
-	namespace := pod.Namespace
+	ip := state.IP()
 
-	search := []string{namespace} // TODO: way more
+	pod := k.podWithIP(ip)
+	if pod == nil {
+		return nil
+	}
 
+	search := make([]string, 3)
+	if zone == "." {
+		search[0] = pod.Namespace + ".svc."
+		search[1] = "svc."
+		search[2] = "."
+	} else {
+		search[0] = pod.Namespace + ".svc." + zone
+		search[1] = "svc." + zone
+		search[2] = zone
+	}
+
+	search = append(search, k.autoPathSearch...)
 	search = append(search, "") // sentinal
-	return search, nil
+	return search
 }
 
-// PodWithIP return the api.Pod for source IP ip. It return nil if nothing can be found.
-func (k *Kubernetes) PodWithIP(ip string) (p *api.Pod) {
+// podWithIP return the api.Pod for source IP ip. It returns nil if nothing can be found.
+func (k *Kubernetes) podWithIP(ip string) (p *api.Pod) {
 	objList := k.APIConn.PodIndex(ip)
 	for _, o := range objList {
 		p, ok := o.(*api.Pod)
diff --git a/middleware/kubernetes/kubernetes.go b/middleware/kubernetes/kubernetes.go
index 417436904..fce4625b6 100644
--- a/middleware/kubernetes/kubernetes.go
+++ b/middleware/kubernetes/kubernetes.go
@@ -47,6 +47,7 @@ type Kubernetes struct {
 	Fallthrough   bool
 
 	interfaceAddrsFunc func() net.IP
+	autoPathSearch     []string // Local search path from /etc/resolv.conf. Needed for autopath.
 }
 
 const (
diff --git a/middleware/kubernetes/setup.go b/middleware/kubernetes/setup.go
index b28e5df18..4c6ba1247 100644
--- a/middleware/kubernetes/setup.go
+++ b/middleware/kubernetes/setup.go
@@ -62,6 +62,8 @@ func kubernetesParse(c *caddy.Controller) (*Kubernetes, error) {
 		Proxy:              proxy.Proxy{},
 	}
 
+	k8s.autoPathSearch = searchFromResolvConf()
+
 	for c.Next() {
 		if c.Val() == "kubernetes" {
 			zones := c.RemainingArgs()
@@ -202,6 +204,15 @@ func kubernetesParse(c *caddy.Controller) (*Kubernetes, error) {
 	return nil, errors.New("kubernetes setup called without keyword 'kubernetes' in Corefile")
 }
 
+func searchFromResolvConf() []string {
+	rc, err := dns.ClientConfigFromFile("/etc/resolv.conf")
+	if err != nil {
+		return nil
+	}
+	middleware.Zones(rc.Search).Normalize()
+	return rc.Search
+}
+
 const (
 	defaultResyncPeriod = 5 * time.Minute
 	defautNdots         = 0