feat(rest): drbd-proxy compatibility stubs (501 Not Implemented)

Cozystack-style clusters run flat L2 so DRBD-9's native protocol
covers everything; we don't actually run drbd-proxy. The endpoints
exist anyway so `linstor drbd-proxy *` returns a deterministic 501
instead of a confusing 404.

Co-Authored-By: Claude <noreply@anthropic.com>
Signed-off-by: Andrei Kvapil <kvapss@gmail.com>

Author: kvaps

PLAN.md

@@ -257,7 +257,7 @@ Full scope list lives in `docs/csi-api-surface.md` (to be created in Phase 1).
 
 - [ ] LUKS encryption layer (volume-level)
 - [ ] DRBD encryption passphrase
-- [ ] DRBD proxy enable/disable/configure
+- [x] DRBD proxy enable/disable/configure: 501 Not Implemented stubs (`/v1/resource-definitions/{rd}/drbd-proxy*`). Cozystack-style clusters run flat L2 so DRBD-9's native protocol suffices; proxy isn't needed. Endpoints exist so `linstor drbd-proxy *` returns a deterministic error.
 - [ ] DRBD options: full set from `drbdoptions.json`
 - [x] file storage provider (`pkg/storage/file`): FILE / FILE_THIN behind same Provider seam — fallocate (thick) / truncate (thin) for create, statfs(2) for pool capacity, snapshots intentionally unsupported (caller routes to LVM/ZFS instead). 9 contract tests.
 - [ ] External-file management

pkg/rest/drbd_proxy.go

@@ -0,0 +1,41 @@
+/*
+Copyright 2026 Cozystack contributors.
+
+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 rest
+
+import (
+	"net/http"
+)
+
+// registerDRBDProxy wires the DRBD-proxy compatibility endpoints. We
+// don't actually run drbd-proxy in cozystack-style clusters — the
+// network is flat L2 and DRBD-9's native protocol handles everything.
+// But the linstor CLI calls these (in `drbd-proxy enable` etc.) and we
+// want a deterministic 501 instead of a confusing 404.
+func (s *Server) registerDRBDProxy(mux *http.ServeMux) {
+	mux.HandleFunc("POST /v1/resource-definitions/{rd}/drbd-proxy/enable/{a}/{b}",
+		handleNotImplemented)
+	mux.HandleFunc("POST /v1/resource-definitions/{rd}/drbd-proxy/disable/{a}/{b}",
+		handleNotImplemented)
+	mux.HandleFunc("PUT /v1/resource-definitions/{rd}/drbd-proxy",
+		handleNotImplemented)
+}
+
+// handleNotImplemented is the shared 501 responder. The body matches
+// the LINSTOR ApiCallRc shape so the CLI renders a sensible error.
+func handleNotImplemented(w http.ResponseWriter, _ *http.Request) {
+	writeError(w, http.StatusNotImplemented, "drbd-proxy is not supported in this build")
+}

pkg/rest/drbd_proxy_test.go

@@ -0,0 +1,56 @@
+/*
+Copyright 2026 Cozystack contributors.
+
+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 rest
+
+import (
+	"net/http"
+	"testing"
+
+	"github.com/cozystack/blockstor/pkg/store"
+)
+
+// TestDRBDProxyEndpointsRespond: every DRBD-proxy endpoint we expose
+// returns 501 Not Implemented. Cozystack does not run DRBD proxy
+// (everything is on the same flat L2), but the linstor CLI calls
+// these and falling through to 404 is worse than an explicit 501.
+func TestDRBDProxyEndpointsRespond(t *testing.T) {
+	base, stop := startServerWithStore(t, store.NewInMemory())
+	defer stop()
+
+	cases := []struct {
+		method string
+		path   string
+	}{
+		{http.MethodPost, "/v1/resource-definitions/pvc-1/drbd-proxy/enable/n1/n2"},
+		{http.MethodPost, "/v1/resource-definitions/pvc-1/drbd-proxy/disable/n1/n2"},
+		{http.MethodPut, "/v1/resource-definitions/pvc-1/drbd-proxy"},
+	}
+
+	for _, tc := range cases {
+		req, _ := http.NewRequestWithContext(t.Context(), tc.method, base+tc.path, nil)
+
+		resp, err := http.DefaultClient.Do(req)
+		if err != nil {
+			t.Fatalf("%s %s: %v", tc.method, tc.path, err)
+		}
+		_ = resp.Body.Close()
+
+		if resp.StatusCode != http.StatusNotImplemented {
+			t.Errorf("%s %s: status %d, want 501", tc.method, tc.path, resp.StatusCode)
+		}
+	}
+}

pkg/rest/server.go

@@ -75,6 +75,7 @@ func (s *Server) Start(ctx context.Context) error {
 	s.registerSnapshotRestore(mux)
 	s.registerEncryption(mux)
 	s.registerNodeLifecycle(mux)
+	s.registerDRBDProxy(mux)
 
 	srv := &http.Server{
 		Addr:              s.Addr,