feat(agent): add http debug routes for magicsock (#7287)

agent/agent.go

@@ -60,7 +60,7 @@ type Options struct {
 	ReconnectingPTYTimeout time.Duration
 	EnvironmentVariables   map[string]string
 	Logger                 slog.Logger
-	AgentPorts             map[int]string
+	IgnorePorts            map[int]string
 	SSHMaxTimeout          time.Duration
 	TailnetListenPort      uint16
 }
@@ -76,7 +76,12 @@ type Client interface {
 	PatchStartupLogs(ctx context.Context, req agentsdk.PatchStartupLogs) error
 }
 
-func New(options Options) io.Closer {
+type Agent interface {
+	HTTPDebug() http.Handler
+	io.Closer
+}
+
+func New(options Options) Agent {
 	if options.ReconnectingPTYTimeout == 0 {
 		options.ReconnectingPTYTimeout = 5 * time.Minute
 	}
@@ -112,7 +117,7 @@ func New(options Options) io.Closer {
 		tempDir:                options.TempDir,
 		lifecycleUpdate:        make(chan struct{}, 1),
 		lifecycleReported:      make(chan codersdk.WorkspaceAgentLifecycle, 1),
-		ignorePorts:            options.AgentPorts,
+		ignorePorts:            options.IgnorePorts,
 		connStatsChan:          make(chan *agentsdk.Stats, 1),
 		sshMaxTimeout:          options.SSHMaxTimeout,
 	}
@@ -1264,6 +1269,27 @@ func (a *agent) isClosed() bool {
 	}
 }
 
+func (a *agent) HTTPDebug() http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		a.closeMutex.Lock()
+		network := a.network
+		a.closeMutex.Unlock()
+
+		if network == nil {
+			w.WriteHeader(http.StatusOK)
+			_, _ = w.Write([]byte("network is not ready yet"))
+			return
+		}
+
+		if r.URL.Path == "/debug/magicsock" {
+			network.MagicsockServeHTTPDebug(w, r)
+		} else {
+			w.WriteHeader(http.StatusNotFound)
+			_, _ = w.Write([]byte("404 not found"))
+		}
+	})
+}
+
 func (a *agent) Close() error {
 	a.closeMutex.Lock()
 	defer a.closeMutex.Unlock()

cli/agent.go

@@ -38,6 +38,7 @@ func (r *RootCmd) workspaceAgent() *clibase.Cmd {
 		sshMaxTimeout     time.Duration
 		tailnetListenPort int64
 		prometheusAddress string
+		debugAddress      string
 	)
 	cmd := &clibase.Cmd{
 		Use:   "agent",
@@ -48,7 +49,7 @@ func (r *RootCmd) workspaceAgent() *clibase.Cmd {
 			ctx, cancel := context.WithCancel(inv.Context())
 			defer cancel()
 
-			agentPorts := map[int]string{}
+			ignorePorts := map[int]string{}
 
 			isLinux := runtime.GOOS == "linux"
 
@@ -125,14 +126,14 @@ func (r *RootCmd) workspaceAgent() *clibase.Cmd {
 			defer pprofSrvClose()
 			// Do a best effort here. If this fails, it's not a big deal.
 			if port, err := urlPort(pprofAddress); err == nil {
-				agentPorts[port] = "pprof"
+				ignorePorts[port] = "pprof"
 			}
 
 			prometheusSrvClose := ServeHandler(ctx, logger, prometheusMetricsHandler(), prometheusAddress, "prometheus")
 			defer prometheusSrvClose()
 			// Do a best effort here. If this fails, it's not a big deal.
 			if port, err := urlPort(prometheusAddress); err == nil {
-				agentPorts[port] = "prometheus"
+				ignorePorts[port] = "prometheus"
 			}
 
 			// exchangeToken returns a session token.
@@ -196,7 +197,7 @@ func (r *RootCmd) workspaceAgent() *clibase.Cmd {
 				return xerrors.Errorf("add executable to $PATH: %w", err)
 			}
 
-			closer := agent.New(agent.Options{
+			agnt := agent.New(agent.Options{
 				Client:            client,
 				Logger:            logger,
 				LogDir:            logDir,
@@ -215,11 +216,19 @@ func (r *RootCmd) workspaceAgent() *clibase.Cmd {
 				EnvironmentVariables: map[string]string{
 					"GIT_ASKPASS": executablePath,
 				},
-				AgentPorts:    agentPorts,
+				IgnorePorts:   ignorePorts,
 				SSHMaxTimeout: sshMaxTimeout,
 			})
+
+			debugSrvClose := ServeHandler(ctx, logger, agnt.HTTPDebug(), debugAddress, "debug")
+			defer debugSrvClose()
+			// Do a best effort here. If this fails, it's not a big deal.
+			if port, err := urlPort(debugAddress); err == nil {
+				ignorePorts[port] = "debug"
+			}
+
 			<-ctx.Done()
-			return closer.Close()
+			return agnt.Close()
 		},
 	}
 
@@ -273,6 +282,13 @@ func (r *RootCmd) workspaceAgent() *clibase.Cmd {
 			Value:       clibase.StringOf(&prometheusAddress),
 			Description: "The bind address to serve Prometheus metrics.",
 		},
+		{
+			Flag:        "debug-address",
+			Default:     "127.0.0.1:2113",
+			Env:         "CODER_AGENT_DEBUG_ADDRESS",
+			Value:       clibase.StringOf(&debugAddress),
+			Description: "The bind address to serve a debug HTTP server.",
+		},
 	}
 
 	return cmd

cli/testdata/coder_agent_--help.golden

@@ -6,6 +6,9 @@ Starts the Coder workspace agent.
       --auth string, $CODER_AGENT_AUTH (default: token)
           Specify the authentication type to use for the agent.
 
+      --debug-address string, $CODER_AGENT_DEBUG_ADDRESS (default: 127.0.0.1:2113)
+          The bind address to serve a debug HTTP server.
+
       --log-dir string, $CODER_AGENT_LOG_DIR (default: /tmp)
           Specify the location for the agent log files.
 

tailnet/conn.go

@@ -828,6 +828,10 @@ func (c *Conn) SetConnStatsCallback(maxPeriod time.Duration, maxConns int, dump
 	c.tunDevice.SetStatistics(connStats)
 }
 
+func (c *Conn) MagicsockServeHTTPDebug(w http.ResponseWriter, r *http.Request) {
+	c.magicConn.ServeHTTPDebug(w, r)
+}
+
 type listenKey struct {
 	network string
 	host    string