From 0794bf65bcde0e42fc3e5178f640bc12aec12ea0 Mon Sep 17 00:00:00 2001
From: Hugo Fonseca <1098293+fonsecas72@users.noreply.github.com>
Date: Fri, 30 Oct 2020 00:32:49 +0000
Subject: [PATCH] HTTP Probe: Add 'Accept' header by default

When using a HTTP probe, the request will now have a "Accept" header by default with the "*/*" (accept all)
Most tools do add this header (see curl) so it's a reasonable expectation that http probe has it as well
---
 pkg/probe/http/http.go      |  8 ++++
 pkg/probe/http/http_test.go | 89 +++++++++++++++++++++++++++++++++++++
 2 files changed, 97 insertions(+)

diff --git a/pkg/probe/http/http.go b/pkg/probe/http/http.go
index 02cdcc045c8..c11e03f18ae 100644
--- a/pkg/probe/http/http.go
+++ b/pkg/probe/http/http.go
@@ -101,6 +101,14 @@ func DoHTTPProbe(url *url.URL, headers http.Header, client GetHTTPInterface) (pr
 		v := version.Get()
 		headers.Set("User-Agent", fmt.Sprintf("kube-probe/%s.%s", v.Major, v.Minor))
 	}
+	if _, ok := headers["Accept"]; !ok {
+		// Accept header was not defined. accept all
+		headers.Set("Accept", "*/*")
+	}
+	if headers.Get("Accept") == "" {
+		// Accept header was overridden but is empty. removing
+		headers.Del("Accept")
+	}
 	req.Header = headers
 	if headers.Get("Host") != "" {
 		req.Host = headers.Get("Host")
diff --git a/pkg/probe/http/http_test.go b/pkg/probe/http/http_test.go
index 16b5b1b0208..f02dee7c123 100644
--- a/pkg/probe/http/http_test.go
+++ b/pkg/probe/http/http_test.go
@@ -24,6 +24,7 @@ import (
 	"net/http/httptest"
 	"net/url"
 	"os"
+	"sort"
 	"strconv"
 	"strings"
 	"testing"
@@ -110,6 +111,24 @@ func TestHTTPProbeChecker(t *testing.T) {
 		w.Write([]byte(output))
 	}
 
+	// Handler that returns the number of request headers in the body
+	headerCounterHandler := func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(200)
+		w.Write([]byte(strconv.Itoa(len(r.Header))))
+	}
+
+	// Handler that returns the keys of request headers in the body
+	headerKeysNamesHandler := func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(200)
+		keys := make([]string, 0, len(r.Header))
+		for k := range r.Header {
+			keys = append(keys, k)
+		}
+		sort.Strings(keys)
+
+		w.Write([]byte(strings.Join(keys, "\n")))
+	}
+
 	redirectHandler := func(s int, bad bool) func(w http.ResponseWriter, r *http.Request) {
 		return func(w http.ResponseWriter, r *http.Request) {
 			if r.URL.Path == "/" {
@@ -135,6 +154,18 @@ func TestHTTPProbeChecker(t *testing.T) {
 			health:  probe.Success,
 			accBody: "ok body",
 		},
+		{
+			handler:    headerCounterHandler,
+			reqHeaders: http.Header{},
+			health:     probe.Success,
+			accBody:    "4",
+		},
+		{
+			handler:    headerKeysNamesHandler,
+			reqHeaders: http.Header{},
+			health:     probe.Success,
+			accBody:    "Accept\nAccept-Encoding\nConnection\nUser-Agent",
+		},
 		{
 			handler: headerEchoHandler,
 			reqHeaders: http.Header{
@@ -165,6 +196,64 @@ func TestHTTPProbeChecker(t *testing.T) {
 			health:     probe.Success,
 			accBody:    "User-Agent: kube-probe/",
 		},
+		{
+			handler: headerEchoHandler,
+			reqHeaders: http.Header{
+				"User-Agent": {"foo/1.0"},
+				"Accept":     {"text/html"},
+			},
+			health:  probe.Success,
+			accBody: "Accept: text/html",
+		},
+		{
+			handler: headerEchoHandler,
+			reqHeaders: http.Header{
+				"User-Agent": {"foo/1.0"},
+				"Accept":     {"foo/*"},
+			},
+			health:  probe.Success,
+			accBody: "User-Agent: foo/1.0",
+		},
+		{
+			handler: headerEchoHandler,
+			reqHeaders: http.Header{
+				"X-Muffins-Or-Cupcakes": {"muffins"},
+				"Accept":                {"foo/*"},
+			},
+			health:  probe.Success,
+			accBody: "X-Muffins-Or-Cupcakes: muffins",
+		},
+		{
+			handler: headerEchoHandler,
+			reqHeaders: http.Header{
+				"Accept": {"foo/*"},
+			},
+			health:  probe.Success,
+			accBody: "Accept: foo/*",
+		},
+		{
+			handler: headerEchoHandler,
+			reqHeaders: http.Header{
+				"Accept": {""},
+			},
+			health:  probe.Success,
+			notBody: "Accept:",
+		},
+		{
+			handler: headerEchoHandler,
+			reqHeaders: http.Header{
+				"User-Agent": {"foo/1.0"},
+				"Accept":     {""},
+			},
+			health:  probe.Success,
+			notBody: "Accept:",
+		},
+		{
+			handler:    headerEchoHandler,
+			reqHeaders: http.Header{},
+			health:     probe.Success,
+			accBody:    "Accept: */*",
+		},
 		{
 			// Echo handler that returns the contents of Host in the body
 			handler: func(w http.ResponseWriter, r *http.Request) {