[Agent] Remove the hard version between Fleet and the Elastic Agent. (e…

…lastic#17764)

* Remove the hard version between Fleet and the Elastic Agent.

This remove the check that Kibana was doing to enforce that the remove
version match the current version of Kibana. Instead the Fleet API
should take the agent header version and ensure we can support it.

This allow the Kibana side to control the communication and the upgrade
more gracefully.

Fixes: elastic#17761

x-pack/elastic-agent/CHANGELOG.asciidoc

@@ -18,8 +18,10 @@
 - Fixed merge of config {pull}17399[17399]
 - Handle abs paths on windows correctly {pull}17461[17461]
 - Improved cancellation of agent {pull}17318[17318]
+- Remove the kbn-version on each request to the Kibana API. {pull}17764[17764]
 - Fixed process spawning on Windows {pull}17751[17751]
 
+
 ==== New features
 
 - Generate index name in a format type-dataset-namespace {pull}16903[16903]

x-pack/elastic-agent/pkg/fleetapi/client.go

@@ -34,7 +34,6 @@ type clienter interface {
 
 var baseRoundTrippers = func(rt http.RoundTripper) (http.RoundTripper, error) {
 	rt = NewFleetUserAgentRoundTripper(rt, release.Version())
-	rt = kibana.NewEnforceKibanaVersionRoundTripper(rt, release.Version())
 	return rt, nil
 }
 

x-pack/elastic-agent/pkg/fleetapi/client_test.go

@@ -17,43 +17,12 @@ import (
 	"github.com/stretchr/testify/require"
 
 	"github.com/elastic/beats/v7/x-pack/elastic-agent/pkg/config"
-	"github.com/elastic/beats/v7/x-pack/elastic-agent/pkg/core/logger"
 	"github.com/elastic/beats/v7/x-pack/elastic-agent/pkg/kibana"
-	"github.com/elastic/beats/v7/x-pack/elastic-agent/pkg/release"
 )
 
 func TestHTTPClient(t *testing.T) {
 	ctx := context.Background()
 
-	t.Run("Ensure we validate the remote Kibana version is higher or equal", withServer(
-		func(t *testing.T) *http.ServeMux {
-			msg := `{ message: "hello" }`
-			mux := http.NewServeMux()
-			mux.HandleFunc("/echo-hello", authHandler(func(w http.ResponseWriter, r *http.Request) {
-				v := r.Header.Get("kbn-version")
-				assert.Equal(t, release.Version(), v)
-				w.WriteHeader(http.StatusOK)
-				fmt.Fprintf(w, msg)
-			}, "abc123"))
-			return mux
-		}, func(t *testing.T, host string) {
-			cfg := &kibana.Config{
-				Host: host,
-			}
-
-			l, err := logger.New()
-			client, err := NewAuthWithConfig(l, "abc123", cfg)
-			require.NoError(t, err)
-			resp, err := client.Send(ctx, "GET", "/echo-hello", nil, nil, nil)
-			require.NoError(t, err)
-
-			body, err := ioutil.ReadAll(resp.Body)
-			require.NoError(t, err)
-			defer resp.Body.Close()
-			assert.Equal(t, `{ message: "hello" }`, string(body))
-		},
-	))
-
 	t.Run("API Key is valid", withServer(
 		func(t *testing.T) *http.ServeMux {
 			msg := `{ message: "hello" }`

x-pack/elastic-agent/pkg/kibana/round_trippers.go

@@ -138,7 +138,7 @@ func (r *EnforceKibanaVersionRoundTripper) RoundTrip(req *http.Request) (*http.R
 }
 
 // NewEnforceKibanaVersionRoundTripper enforce the remove endpoint to be a a certain version, if the
-// remove kibana is not equal or superior on the requested version the call will fail.
+// remote kibana is not equal the call will fail.
 func NewEnforceKibanaVersionRoundTripper(wrapped http.RoundTripper, version string) http.RoundTripper {
 	return &EnforceKibanaVersionRoundTripper{rt: wrapped, version: version}
 }