feat: add endpoint to get listening ports in agent (#4260)

agent/agent.go

@@ -10,6 +10,7 @@ import (
 	"fmt"
 	"io"
 	"net"
+	"net/http"
 	"net/netip"
 	"os"
 	"os/exec"
@@ -206,6 +207,7 @@ func (a *agent) runTailnet(ctx context.Context, derpMap *tailcfg.DERPMap) {
 			go a.sshServer.HandleConn(a.stats.wrapConn(conn))
 		}
 	}()
+
 	reconnectingPTYListener, err := a.network.Listen("tcp", ":"+strconv.Itoa(codersdk.TailnetReconnectingPTYPort))
 	if err != nil {
 		a.logger.Critical(ctx, "listen for reconnecting pty", slog.Error(err))
@@ -240,6 +242,7 @@ func (a *agent) runTailnet(ctx context.Context, derpMap *tailcfg.DERPMap) {
 			go a.handleReconnectingPTY(ctx, msg, conn)
 		}
 	}()
+
 	speedtestListener, err := a.network.Listen("tcp", ":"+strconv.Itoa(codersdk.TailnetSpeedtestPort))
 	if err != nil {
 		a.logger.Critical(ctx, "listen for speedtest", slog.Error(err))
@@ -261,6 +264,31 @@ func (a *agent) runTailnet(ctx context.Context, derpMap *tailcfg.DERPMap) {
 			}()
 		}
 	}()
+
+	statisticsListener, err := a.network.Listen("tcp", ":"+strconv.Itoa(codersdk.TailnetStatisticsPort))
+	if err != nil {
+		a.logger.Critical(ctx, "listen for statistics", slog.Error(err))
+		return
+	}
+	go func() {
+		defer statisticsListener.Close()
+		server := &http.Server{
+			Handler:           a.statisticsHandler(),
+			ReadTimeout:       20 * time.Second,
+			ReadHeaderTimeout: 20 * time.Second,
+			WriteTimeout:      20 * time.Second,
+			ErrorLog:          slog.Stdlib(ctx, a.logger.Named("statistics_http_server"), slog.LevelInfo),
+		}
+		go func() {
+			<-ctx.Done()
+			_ = server.Close()
+		}()
+
+		err = server.Serve(statisticsListener)
+		if err != nil && !xerrors.Is(err, http.ErrServerClosed) && !strings.Contains(err.Error(), "use of closed network connection") {
+			a.logger.Critical(ctx, "serve statistics HTTP server", slog.Error(err))
+		}
+	}()
 }
 
 // runCoordinator listens for nodes and updates the self-node as it changes.

agent/ports_supported.go

@@ -0,0 +1,65 @@
+//go:build linux || windows
+// +build linux windows
+
+package agent
+
+import (
+	"time"
+
+	"github.com/cakturk/go-netstat/netstat"
+	"golang.org/x/xerrors"
+
+	"github.com/coder/coder/codersdk"
+)
+
+func (lp *listeningPortsHandler) getListeningPorts() ([]codersdk.ListeningPort, error) {
+	lp.mut.Lock()
+	defer lp.mut.Unlock()
+
+	if time.Since(lp.mtime) < time.Second {
+		// copy
+		ports := make([]codersdk.ListeningPort, len(lp.ports))
+		copy(ports, lp.ports)
+		return ports, nil
+	}
+
+	tabs, err := netstat.TCPSocks(func(s *netstat.SockTabEntry) bool {
+		return s.State == netstat.Listen
+	})
+	if err != nil {
+		return nil, xerrors.Errorf("scan listening ports: %w", err)
+	}
+
+	seen := make(map[uint16]struct{}, len(tabs))
+	ports := []codersdk.ListeningPort{}
+	for _, tab := range tabs {
+		if tab.LocalAddr == nil || tab.LocalAddr.Port < uint16(codersdk.MinimumListeningPort) {
+			continue
+		}
+
+		// Don't include ports that we've already seen. This can happen on
+		// Windows, and maybe on Linux if you're using a shared listener socket.
+		if _, ok := seen[tab.LocalAddr.Port]; ok {
+			continue
+		}
+		seen[tab.LocalAddr.Port] = struct{}{}
+
+		procName := ""
+		if tab.Process != nil {
+			procName = tab.Process.Name
+		}
+		ports = append(ports, codersdk.ListeningPort{
+			ProcessName: procName,
+			Network:     codersdk.ListeningPortNetworkTCP,
+			Port:        tab.LocalAddr.Port,
+		})
+	}
+
+	lp.ports = ports
+	lp.mtime = time.Now()
+
+	// copy
+	ports = make([]codersdk.ListeningPort, len(lp.ports))
+	copy(ports, lp.ports)
+	return ports, nil
+}

agent/ports_unsupported.go

@@ -0,0 +1,13 @@
+//go:build !linux && !windows
+// +build !linux,!windows
+
+package agent
+
+import "github.com/coder/coder/codersdk"
+
+func (lp *listeningPortsHandler) getListeningPorts() ([]codersdk.ListeningPort, error) {
+	// Can't scan for ports on non-linux or non-windows systems at the moment.
+	// The UI will not show any "no ports found" message to the user, so the
+	// user won't suspect a thing.
+	return []codersdk.ListeningPort{}, nil
+}

agent/statsendpoint.go

@@ -0,0 +1,49 @@
+package agent
+
+import (
+	"net/http"
+	"sync"
+	"time"
+
+	"github.com/go-chi/chi"
+
+	"github.com/coder/coder/coderd/httpapi"
+	"github.com/coder/coder/codersdk"
+)
+
+func (*agent) statisticsHandler() http.Handler {
+	r := chi.NewRouter()
+	r.Get("/", func(rw http.ResponseWriter, r *http.Request) {
+		httpapi.Write(r.Context(), rw, http.StatusOK, codersdk.Response{
+			Message: "Hello from the agent!",
+		})
+	})
+
+	lp := &listeningPortsHandler{}
+	r.Get("/api/v0/listening-ports", lp.handler)
+
+	return r
+}
+
+type listeningPortsHandler struct {
+	mut   sync.Mutex
+	ports []codersdk.ListeningPort
+	mtime time.Time
+}
+
+// handler returns a list of listening ports. This is tested by coderd's
+// TestWorkspaceAgentListeningPorts test.
+func (lp *listeningPortsHandler) handler(rw http.ResponseWriter, r *http.Request) {
+	ports, err := lp.getListeningPorts()
+	if err != nil {
+		httpapi.Write(r.Context(), rw, http.StatusInternalServerError, codersdk.Response{
+			Message: "Could not scan for listening ports.",
+			Detail:  err.Error(),
+		})
+		return
+	}
+
+	httpapi.Write(r.Context(), rw, http.StatusOK, codersdk.ListeningPortsResponse{
+		Ports: ports,
+	})
+}