feat: add debug endpoint for single tailnet (#10485)

coderd/apidoc/docs.go

@@ -422,6 +422,28 @@ const docTemplate = `{
                 }
             }
         },
+        "/debug/tailnet": {
+            "get": {
+                "security": [
+                    {
+                        "CoderSessionToken": []
+                    }
+                ],
+                "produces": [
+                    "text/html"
+                ],
+                "tags": [
+                    "Debug"
+                ],
+                "summary": "Debug Info Tailnet",
+                "operationId": "debug-info-tailnet",
+                "responses": {
+                    "200": {
+                        "description": "OK"
+                    }
+                }
+            }
+        },
         "/debug/ws": {
             "get": {
                 "security": [

coderd/apidoc/swagger.json

@@ -358,6 +358,24 @@
         }
       }
     },
+    "/debug/tailnet": {
+      "get": {
+        "security": [
+          {
+            "CoderSessionToken": []
+          }
+        ],
+        "produces": ["text/html"],
+        "tags": ["Debug"],
+        "summary": "Debug Info Tailnet",
+        "operationId": "debug-info-tailnet",
+        "responses": {
+          "200": {
+            "description": "OK"
+          }
+        }
+      }
+    },
     "/debug/ws": {
       "get": {
         "security": [

coderd/coderd.go

@@ -955,6 +955,7 @@ func New(options *Options) *API {
 			)
 
 			r.Get("/coordinator", api.debugCoordinator)
+			r.Get("/tailnet", api.debugTailnet)
 			r.Get("/health", api.debugDeploymentHealth)
 			r.Get("/ws", (&healthcheck.WebsocketEchoServer{}).ServeHTTP)
 		})

coderd/coderdtest/swaggerparser.go

@@ -352,7 +352,8 @@ func assertProduce(t *testing.T, comment SwaggerComment) {
 			(comment.router == "/workspaceagents/me/startup" && comment.method == "post") ||
 			(comment.router == "/workspaceagents/me/startup/logs" && comment.method == "patch") ||
 			(comment.router == "/licenses/{id}" && comment.method == "delete") ||
-			(comment.router == "/debug/coordinator" && comment.method == "get") {
+			(comment.router == "/debug/coordinator" && comment.method == "get") ||
+			(comment.router == "/debug/tailnet" && comment.method == "get") {
 			return // Exception: HTTP 200 is returned without response entity
 		}
 

coderd/debug.go

@@ -23,6 +23,17 @@ func (api *API) debugCoordinator(rw http.ResponseWriter, r *http.Request) {
 	(*api.TailnetCoordinator.Load()).ServeHTTPDebug(rw, r)
 }
 
+// @Summary Debug Info Tailnet
+// @ID debug-info-tailnet
+// @Security CoderSessionToken
+// @Produce text/html
+// @Tags Debug
+// @Success 200
+// @Router /debug/tailnet [get]
+func (api *API) debugTailnet(rw http.ResponseWriter, r *http.Request) {
+	api.agentProvider.ServeHTTPDebug(rw, r)
+}
+
 // @Summary Debug Info Deployment Health
 // @ID debug-info-deployment-health
 // @Security CoderSessionToken

coderd/tailnet.go

@@ -21,6 +21,7 @@ import (
 
 	"cdr.dev/slog"
 	"github.com/coder/coder/v2/coderd/tracing"
+	"github.com/coder/coder/v2/coderd/workspaceapps"
 	"github.com/coder/coder/v2/coderd/wsconncache"
 	"github.com/coder/coder/v2/codersdk"
 	"github.com/coder/coder/v2/site"
@@ -38,6 +39,8 @@ func init() {
 	}
 }
 
+var _ workspaceapps.AgentProvider = (*ServerTailnet)(nil)
+
 // NewServerTailnet creates a new tailnet intended for use by coderd. It
 // automatically falls back to wsconncache if a legacy agent is encountered.
 func NewServerTailnet(
@@ -419,6 +422,10 @@ func (s *ServerTailnet) DialAgentNetConn(ctx context.Context, agentID uuid.UUID,
 	}}, err
 }
 
+func (s *ServerTailnet) ServeHTTPDebug(w http.ResponseWriter, r *http.Request) {
+	s.conn.MagicsockServeHTTPDebug(w, r)
+}
+
 type netConnCloser struct {
 	net.Conn
 	close func()

coderd/workspaceapps/proxy.go

@@ -74,6 +74,8 @@ type AgentProvider interface {
 	// func.
 	AgentConn(ctx context.Context, agentID uuid.UUID) (_ *codersdk.WorkspaceAgentConn, release func(), _ error)
 
+	ServeHTTPDebug(w http.ResponseWriter, r *http.Request)
+
 	Close() error
 }
 

coderd/wsconncache/wsconncache.go

@@ -16,10 +16,13 @@ import (
 	"golang.org/x/sync/singleflight"
 	"golang.org/x/xerrors"
 
+	"github.com/coder/coder/v2/coderd/workspaceapps"
 	"github.com/coder/coder/v2/codersdk"
 	"github.com/coder/coder/v2/site"
 )
 
+var _ workspaceapps.AgentProvider = (*AgentProvider)(nil)
+
 type AgentProvider struct {
 	Cache *Cache
 }
@@ -56,6 +59,8 @@ func (a *AgentProvider) ReverseProxy(targetURL *url.URL, dashboardURL *url.URL,
 	return proxy, release, nil
 }
 
+func (*AgentProvider) ServeHTTPDebug(http.ResponseWriter, *http.Request) {}
+
 func (a *AgentProvider) Close() error {
 	return a.Cache.Close()
 }

docs/api/debug.md

@@ -241,3 +241,23 @@ curl -X GET http://coder-server:8080/api/v2/debug/health \
 | 200    | [OK](https://tools.ietf.org/html/rfc7231#section-6.3.1) | OK          | [healthcheck.Report](schemas.md#healthcheckreport) |
 
 To perform this operation, you must be authenticated. [Learn more](authentication.md).
+
+## Debug Info Tailnet
+
+### Code samples
+
+```shell
+# Example request using curl
+curl -X GET http://coder-server:8080/api/v2/debug/tailnet \
+  -H 'Coder-Session-Token: API_KEY'
+```
+
+`GET /debug/tailnet`
+
+### Responses
+
+| Status | Meaning                                                 | Description | Schema |
+| ------ | ------------------------------------------------------- | ----------- | ------ |
+| 200    | [OK](https://tools.ietf.org/html/rfc7231#section-6.3.1) | OK          |        |
+
+To perform this operation, you must be authenticated. [Learn more](authentication.md).