Merge pull request #79423 from danwinship/agnhost-connect

Add new agnhost subcommand for a networking test

test/images/agnhost/BUILD

@@ -17,6 +17,7 @@ go_library(
     importpath = "k8s.io/kubernetes/test/images/agnhost",
     deps = [
         "//test/images/agnhost/audit-proxy:go_default_library",
+        "//test/images/agnhost/connect:go_default_library",
         "//test/images/agnhost/crd-conversion-webhook:go_default_library",
         "//test/images/agnhost/dns:go_default_library",
         "//test/images/agnhost/entrypoint-tester:go_default_library",
@@ -51,6 +52,7 @@ filegroup(
     srcs = [
         ":package-srcs",
         "//test/images/agnhost/audit-proxy:all-srcs",
+        "//test/images/agnhost/connect:all-srcs",
         "//test/images/agnhost/crd-conversion-webhook:all-srcs",
         "//test/images/agnhost/dns:all-srcs",
         "//test/images/agnhost/entrypoint-tester:all-srcs",

test/images/agnhost/README.md

@@ -10,7 +10,7 @@ information could retrieved through other means. To combat those differences,
 
 `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.
+word of the words agnostic and host.
 
 The image was created for testing purposes, reducing the need for having different test
 cases for the same tested behaviour.
@@ -77,6 +77,29 @@ Usage:
 ```
 
 
+### connect
+
+Tries to open a TCP connection to the given host and port. On error it
+prints an error message prefixed with a specific fixed string that
+test cases can check for:
+
+* `UNKNOWN` - Generic/unknown (non-network) error (eg, bad arguments)
+* `TIMEOUT` - The connection attempt timed out
+* `DNS` - An error in DNS resolution
+* `REFUSED` - Connection refused
+* `OTHER` - Other networking error (eg, "no route to host")
+
+(Theoretically it would be nicer for it to distinguish these by exit
+code, but it's much easier for test programs to compare strings in the
+output than to check the exit code.)
+
+Usage:
+
+```console
+    kubectl exec test-agnost -- /agnost connect [--timeout=<duration>] <host>:<port>
+```
+
+
 ### crd-conversion-webhook
 
 The subcommand tests `CustomResourceConversionWebhook`. After deploying it to Kubernetes cluster,

test/images/agnhost/VERSION

@@ -1 +1 @@
-2.2
+2.4

test/images/agnhost/agnhost.go

@@ -23,6 +23,7 @@ import (
 
 	"k8s.io/klog"
 	"k8s.io/kubernetes/test/images/agnhost/audit-proxy"
+	"k8s.io/kubernetes/test/images/agnhost/connect"
 	"k8s.io/kubernetes/test/images/agnhost/crd-conversion-webhook"
 	"k8s.io/kubernetes/test/images/agnhost/dns"
 	"k8s.io/kubernetes/test/images/agnhost/entrypoint-tester"
@@ -45,6 +46,7 @@ import (
 func main() {
 	rootCmd := &cobra.Command{Use: "app"}
 	rootCmd.AddCommand(auditproxy.CmdAuditProxy)
+	rootCmd.AddCommand(connect.CmdConnect)
 	rootCmd.AddCommand(crdconvwebhook.CmdCrdConversionWebhook)
 	rootCmd.AddCommand(dns.CmdDNSSuffix)
 	rootCmd.AddCommand(dns.CmdDNSServerList)

test/images/agnhost/connect/BUILD

@@ -0,0 +1,26 @@
+package(default_visibility = ["//visibility:public"])
+
+load(
+    "@io_bazel_rules_go//go:def.bzl",
+    "go_library",
+)
+
+go_library(
+    name = "go_default_library",
+    srcs = ["connect.go"],
+    importpath = "k8s.io/kubernetes/test/images/agnhost/connect",
+    deps = ["//vendor/github.com/spf13/cobra:go_default_library"],
+)
+
+filegroup(
+    name = "package-srcs",
+    srcs = glob(["**"]),
+    tags = ["automanaged"],
+    visibility = ["//visibility:private"],
+)
+
+filegroup(
+    name = "all-srcs",
+    srcs = [":package-srcs"],
+    tags = ["automanaged"],
+)

test/images/agnhost/connect/connect.go

@@ -0,0 +1,83 @@
+/*
+Copyright 2019 The Kubernetes 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 connect
+
+import (
+	"fmt"
+	"net"
+	"os"
+	"syscall"
+	"time"
+
+	"github.com/spf13/cobra"
+)
+
+// CmdConnect is used by agnhost Cobra.
+var CmdConnect = &cobra.Command{
+	Use:   "connect [host:port]",
+	Short: "Attempts a TCP connection and returns useful errors",
+	Long: `Tries to open a TCP connection to the given host and port. On error it prints an error message prefixed with a specific fixed string that test cases can check for:
+
+* UNKNOWN - Generic/unknown (non-network) error (eg, bad arguments)
+* TIMEOUT - The connection attempt timed out
+* DNS - An error in DNS resolution
+* REFUSED - Connection refused
+* OTHER - Other networking error (eg, "no route to host")`,
+	Args: cobra.ExactArgs(1),
+	Run:  main,
+}
+
+var timeout time.Duration
+
+func init() {
+	CmdConnect.Flags().DurationVar(&timeout, "timeout", time.Duration(0), "Maximum time before returning an error")
+}
+
+func main(cmd *cobra.Command, args []string) {
+	dest := args[0]
+
+	// Redundantly parse and resolve the destination so we can return the correct
+	// errors if there's a problem.
+	if _, _, err := net.SplitHostPort(dest); err != nil {
+		fmt.Fprintf(os.Stderr, "UNKNOWN: %v\n", err)
+		os.Exit(1)
+	}
+	if _, err := net.ResolveTCPAddr("tcp", dest); err != nil {
+		fmt.Fprintf(os.Stderr, "DNS: %v\n", err)
+		os.Exit(1)
+	}
+
+	conn, err := net.DialTimeout("tcp", dest, timeout)
+	if err == nil {
+		conn.Close()
+		os.Exit(0)
+	}
+	if opErr, ok := err.(*net.OpError); ok {
+		if opErr.Timeout() {
+			fmt.Fprintf(os.Stderr, "TIMEOUT\n")
+			os.Exit(1)
+		} else if syscallErr, ok := opErr.Err.(*os.SyscallError); ok {
+			if syscallErr.Err == syscall.ECONNREFUSED {
+				fmt.Fprintf(os.Stderr, "REFUSED\n")
+				os.Exit(1)
+			}
+		}
+	}
+
+	fmt.Fprintf(os.Stderr, "OTHER: %v\n", err)
+	os.Exit(1)
+}