csi: fix volume registration error (#26642)

.changelog/26642.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+csi: fix EOF error when registering volumes
+```

api/csi.go

@@ -503,6 +503,7 @@ type CSIVolumeRegisterRequest struct {
 type CSIVolumeRegisterResponse struct {
 	Volumes  []*CSIVolume
 	Warnings string
+	QueryMeta
 }
 
 type CSIVolumeDeregisterRequest struct {

command/agent/csi_endpoint.go

@@ -146,7 +146,7 @@ func (s *HTTPServer) csiVolumeRegister(resp http.ResponseWriter, req *http.Reque
 
 	setMeta(resp, &out.QueryMeta)
 
-	return nil, nil
+	return out, nil
 }
 
 func (s *HTTPServer) csiVolumeCreate(resp http.ResponseWriter, req *http.Request) (interface{}, error) {

command/volume_register_csi.go

@@ -35,9 +35,11 @@ func (c *VolumeRegisterCommand) csiRegister(client *api.Client, ast *ast.File, o
 				fmt.Sprintf("[bold][yellow]Volume Warnings:\n%s[reset]\n", resp.Warnings)))
 	}
 
-	vol = resp.Volumes[0] // note: the command only ever returns 1 volume from the API
-
+	for _, vol := range resp.Volumes {
+		// note: the command only ever returns 1 volume from the API
 		c.Ui.Output(fmt.Sprintf("Volume %q registered", vol.ID))
+	}
+
 	return 0
 }
 

nomad/csi_endpoint.go

@@ -371,6 +371,7 @@ func (v *CSIVolume) Register(args *structs.CSIVolumeRegisterRequest, reply *stru
 		return err
 	}
 
+	reply.Volumes = args.Volumes
 	reply.Index = index
 	v.srv.setQueryMeta(&reply.QueryMeta)
 	return nil

nomad/structs/csi.go

@@ -879,9 +879,10 @@ type CSIVolumeRegisterRequest struct {
 }
 
 type CSIVolumeRegisterResponse struct {
+	Volumes []*CSIVolume
+
 	// Warnings are non-fatal messages from Enterprise policy enforcement
 	Warnings string
-
 	QueryMeta
 }