tests: agnhost image updates

test/images/agnhost/README.md

+# Agnhost
+
+## Overview
+
+There are significant differences between Linux and Windows, especially in the way
+something can be obtained or tested. For example, the DNS suffix list can be found in
+`/etc/resolv.conf` on Linux, but on Windows, such file does not exist, the same
+information could retrieved through other means. To combat those differences,
+`agnhost` was created.
+
+`agnhost` is an extendable CLI that behaves and outputs the same expected content,
+no matter the underlying OS. The name itself reflects this idea, being a portmanteau
+word of the words agnost and host.
+
+The image was created for testing purposes, reducing the need for having different test
+cases for the same tested behaviour.
+
+## Usage
+
+The `agnhost` binary is a CLI with the following subcommands:
+
+- `dns-suffix`: It will output the host's configured DNS suffix list, separated by commas.
+- `dns-server-list`: It will output the host's configured DNS servers, separated by commas.
+- `etc-hosts`: It will output the contents of host's `hosts` file. This file's location
+  is `/etc/hosts` on Linux, while on Windows it is `C:/Windows/System32/drivers/etc/hosts`.
+- `pause`: It will pause the execution of the binary. This can be used for containers
+  which have to be kept in a `Running` state for various purposes, including executing
+  other `agnhost` commands.
+- `help`: Prints the binary's help menu. Additionally, it can be followed by another
+  subcommand in order to get more information about that subcommand, including its
+  possible arguments.
+
+For example, let's consider the following `pod.yaml` file:
+
+```yaml
+    apiVersion: v1
+    kind: Pod
+    metadata:
+      name: test-agnhost
+    spec:
+      containers:
+      - args:
+        - dns-suffix
+        image: gcr.io/kubernetes-e2e-test-images/agnhost:1.0
+        name: agnhost
+      dnsConfig:
+        nameservers:
+        - 1.1.1.1
+        searches:
+        - resolv.conf.local
+      dnsPolicy: None
+```
+
+After we've used it to create a pod:
+
+```console
+    kubectl create -f pod.yaml
+```
+
+We can then check the container's output to see what is DNS suffix list the Pod was
+configured with:
+
+```console
+    kubectl logs pod/test-agnhost
+```
+
+The output will be `resolv.conf.local`, as expected. Alternatively, the Pod could be
+created with the `pause` argument instead, allowing us execute multiple commands:
+
+```console
+    kubectl exec test-agnhost -- /agnhost dns-suffix
+    kubectl exec test-agnhost -- /agnhost dns-server-list
+```
+
+## Image
+
+The image can be found at `gcr.io/kubernetes-e2e-test-images/agnhost:1.0` for Linux
+containers, and `e2eteam/agnhost:1.0` for Windows containers. In the future, the same
+repository can be used for both OSes.

test/images/agnhost/agnhost.go

@@ -23,13 +23,40 @@ import (
 func main() {
 	cmdDNSSuffix := &cobra.Command{
 		Use:   "dns-suffix",
-		Short: "Prints the host's DNS suffix list.",
-		Long:  `prints the DNS suffixes of this host.`,
+		Short: "Prints the host's DNS suffix list",
+		Long:  `Prints the DNS suffixes of this host.`,
 		Args:  cobra.MaximumNArgs(0),
 		Run:   printDNSSuffixList,
 	}
 
+	cmdDNSServerList := &cobra.Command{
+		Use:   "dns-server-list",
+		Short: "Prints the host's DNS Server list",
+		Long:  `Prints the DNS Server list of this host.`,
+		Args:  cobra.MaximumNArgs(0),
+		Run:   printDNSServerList,
+	}
+
+	cmdEtcHosts := &cobra.Command{
+		Use:   "etc-hosts",
+		Short: "Prints the host's /etc/hosts file",
+		Long:  `Prints the "hosts" file of this host."`,
+		Args:  cobra.MaximumNArgs(0),
+		Run:   printHostsFile,
+	}
+
+	cmdPause := &cobra.Command{
+		Use:   "pause",
+		Short: "Pauses",
+		Long:  `Pauses the execution. Useful for keeping the containers running, so other commands can be executed.`,
+		Args:  cobra.MaximumNArgs(0),
+		Run:   pause,
+	}
+
 	rootCmd := &cobra.Command{Use: "app"}
 	rootCmd.AddCommand(cmdDNSSuffix)
+	rootCmd.AddCommand(cmdDNSServerList)
+	rootCmd.AddCommand(cmdEtcHosts)
+	rootCmd.AddCommand(cmdPause)
 	rootCmd.Execute()
 }

test/images/agnhost/common.go

@@ -17,8 +17,14 @@ limitations under the License.
 package main
 
 import (
+	"bytes"
 	"fmt"
+	"io/ioutil"
+	"os"
+	"os/exec"
+	"os/signal"
 	"strings"
+	"syscall"
 
 	"github.com/spf13/cobra"
 )
@@ -27,3 +33,58 @@ func printDNSSuffixList(cmd *cobra.Command, args []string) {
 	dnsSuffixList := getDNSSuffixList()
 	fmt.Println(strings.Join(dnsSuffixList, ","))
 }
+
+func printDNSServerList(cmd *cobra.Command, args []string) {
+	dnsServerList := getDNSServerList()
+	fmt.Println(strings.Join(dnsServerList, ","))
+}
+
+func printHostsFile(cmd *cobra.Command, args []string) {
+	fmt.Println(readFile(etcHostsFile))
+}
+
+func pause(cmd *cobra.Command, args []string) {
+	sigCh := make(chan os.Signal)
+	done := make(chan int, 1)
+	signal.Notify(sigCh, syscall.SIGINT)
+	signal.Notify(sigCh, syscall.SIGTERM)
+	signal.Notify(sigCh, syscall.SIGKILL)
+	go func() {
+		sig := <-sigCh
+		switch sig {
+		case syscall.SIGINT:
+			done <- 1
+			os.Exit(1)
+		case syscall.SIGTERM:
+			done <- 2
+			os.Exit(2)
+		case syscall.SIGKILL:
+			done <- 0
+			os.Exit(0)
+		}
+	}()
+	result := <-done
+	fmt.Printf("exiting %d\n", result)
+}
+
+func readFile(fileName string) string {
+	fileData, err := ioutil.ReadFile(fileName)
+	if err != nil {
+		panic(err)
+	}
+
+	return string(fileData)
+}
+
+func runCommand(name string, arg ...string) string {
+	var out bytes.Buffer
+	cmd := exec.Command(name, arg...)
+	cmd.Stdout = &out
+
+	err := cmd.Run()
+	if err != nil {
+		panic(err)
+	}
+
+	return strings.TrimSpace(out.String())
+}

test/images/agnhost/utils.go

@@ -19,22 +19,18 @@ limitations under the License.
 package main
 
 import (
-	"io/ioutil"
 	"strings"
 )
 
-func getDNSSuffixList() []string {
-	// A /etc/resolv.conf file managed by kubelet looks like this:
-	// nameserver DNS_CLUSTER_IP
-	// search test-dns.svc.cluster.local svc.cluster.local cluster.local q53aahaikqaehcai3ylfqdtc5b.bx.internal.cloudapp.net
-	// options ndots:5
-
-	fileData, err := ioutil.ReadFile("/etc/resolv.conf")
-	if err != nil {
-		panic(err)
-	}
+const etcHostsFile = "/etc/hosts"
 
-	lines := strings.Split(string(fileData), "\n")
+// A /etc/resolv.conf file managed by kubelet looks like this:
+// nameserver DNS_CLUSTER_IP
+// search test-dns.svc.cluster.local svc.cluster.local cluster.local q53aahaikqaehcai3ylfqdtc5b.bx.internal.cloudapp.net
+// options ndots:5
+func getDNSSuffixList() []string {
+	fileData := readFile("/etc/resolv.conf")
+	lines := strings.Split(fileData, "\n")
 	for _, line := range lines {
 		if strings.HasPrefix(line, "search") {
 			// omit the starting "search".
@@ -44,3 +40,16 @@ func getDNSSuffixList() []string {
 
 	panic("Could not find DNS search list!")
 }
+
+func getDNSServerList() []string {
+	fileData := readFile("/etc/resolv.conf")
+	lines := strings.Split(fileData, "\n")
+	for _, line := range lines {
+		if strings.HasPrefix(line, "nameserver") {
+			// omit the starting "nameserver".
+			return strings.Split(line, " ")[1:]
+		}
+	}
+
+	panic("Could not find DNS search list!")
+}

test/images/agnhost/utils_windows.go

@@ -17,25 +17,25 @@ limitations under the License.
 package main
 
 import (
-	"bytes"
-	"os/exec"
 	"strings"
 )
 
-func getDNSSuffixList() []string {
-	var out bytes.Buffer
-	cmd := exec.Command("powershell", "-Command", "(Get-DnsClient)[0].SuffixSearchList")
-	cmd.Stdout = &out
+const etcHostsFile = "C:/Windows/System32/drivers/etc/hosts"
 
-	err := cmd.Run()
-	if err != nil {
-		panic(err)
+func getDNSSuffixList() []string {
+	output := runCommand("powershell", "-Command", "(Get-DnsClient)[0].SuffixSearchList")
+	if len(output) > 0 {
+		return strings.Split(output, "\r\n")
 	}
 
-	output := strings.TrimSpace(out.String())
+	panic("Could not find DNS search list!")
+}
+
+func getDNSServerList() []string {
+	output := runCommand("powershell", "-Command", "(Get-DnsClientServerAddress).ServerAddresses")
 	if len(output) > 0 {
 		return strings.Split(output, "\r\n")
 	}
 
-	panic("Could not find DNS search list!")
+	panic("Could not find DNS Server list!")
 }