From 59bc6867a4c7946974f03a8457530d643938f9cd Mon Sep 17 00:00:00 2001
From: Dean Sheather <dean@deansheather.com>
Date: Tue, 8 Aug 2023 17:31:26 +0000
Subject: [PATCH 1/2] chore: add debug endpoint on agent to enable magicsock
 debug logging

---
 agent/agent.go      | 48 +++++++++++++++++++----
 agent/agent_test.go | 92 ++++++++++++++++++++++++++++++++++++++++++++-
 tailnet/conn.go     | 20 ++++++++++
 3 files changed, 152 insertions(+), 8 deletions(-)

diff --git a/agent/agent.go b/agent/agent.go
index 52c423787fb44..e435b795d5fc9 100644
--- a/agent/agent.go
+++ b/agent/agent.go
@@ -22,6 +22,7 @@ import (
 	"time"
 
 	"github.com/armon/circbuf"
+	"github.com/go-chi/chi/v5"
 	"github.com/google/uuid"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/spf13/afero"
@@ -1408,24 +1409,57 @@ func (a *agent) isClosed() bool {
 }
 
 func (a *agent) HTTPDebug() http.Handler {
-	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+	r := chi.NewRouter()
+
+	requireNetwork := func(w http.ResponseWriter) (*tailnet.Conn, bool) {
 		a.closeMutex.Lock()
 		network := a.network
 		a.closeMutex.Unlock()
 
 		if network == nil {
-			w.WriteHeader(http.StatusOK)
+			w.WriteHeader(http.StatusNotFound)
 			_, _ = w.Write([]byte("network is not ready yet"))
+			return nil, false
+		}
+
+		return network, true
+	}
+
+	r.Get("/debug/magicsock", func(w http.ResponseWriter, r *http.Request) {
+		network, ok := requireNetwork(w)
+		if !ok {
 			return
 		}
+		network.MagicsockServeHTTPDebug(w, r)
+	})
 
-		if r.URL.Path == "/debug/magicsock" {
-			network.MagicsockServeHTTPDebug(w, r)
-		} else {
-			w.WriteHeader(http.StatusNotFound)
-			_, _ = w.Write([]byte("404 not found"))
+	r.Get("/debug/magicsock/debug-logging/{state}", func(w http.ResponseWriter, r *http.Request) {
+		state := chi.URLParam(r, "state")
+		stateBool, err := strconv.ParseBool(state)
+		if err != nil {
+			w.WriteHeader(http.StatusBadRequest)
+			_, _ = fmt.Fprintf(w, "invalid state %q, must be a boolean", state)
+			return
+		}
+
+		network, ok := requireNetwork(w)
+		if !ok {
+			return
 		}
+
+		network.MagicsockSetDebugLoggingEnabled(stateBool)
+		a.logger.Info(r.Context(), "updated magicsock debug logging due to debug request", slog.F("new_state", stateBool))
+
+		w.WriteHeader(http.StatusOK)
+		_, _ = fmt.Fprintf(w, "updated magicsock debug logging to %v", stateBool)
 	})
+
+	r.NotFound(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusNotFound)
+		_, _ = w.Write([]byte("404 not found"))
+	})
+
+	return r
 }
 
 func (a *agent) Close() error {
diff --git a/agent/agent_test.go b/agent/agent_test.go
index 34637992536b7..92be40764f209 100644
--- a/agent/agent_test.go
+++ b/agent/agent_test.go
@@ -1932,6 +1932,96 @@ func TestAgent_WriteVSCodeConfigs(t *testing.T) {
 	}, testutil.WaitShort, testutil.IntervalFast)
 }
 
+func TestAgent_DebugServer(t *testing.T) {
+	t.Parallel()
+
+	derpMap, _ := tailnettest.RunDERPAndSTUN(t)
+	//nolint:dogsled
+	conn, _, _, _, agnt := setupAgent(t, agentsdk.Manifest{
+		DERPMap: derpMap,
+	}, 0)
+
+	awaitReachableCtx := testutil.Context(t, testutil.WaitLong)
+	ok := conn.AwaitReachable(awaitReachableCtx)
+	require.True(t, ok)
+	_ = conn.Close()
+
+	srv := httptest.NewServer(agnt.HTTPDebug())
+	t.Cleanup(srv.Close)
+
+	t.Run("MagicsockDebug", func(t *testing.T) {
+		t.Parallel()
+
+		ctx := testutil.Context(t, testutil.WaitLong)
+		req, err := http.NewRequestWithContext(ctx, http.MethodGet, srv.URL+"/debug/magicsock", nil)
+		require.NoError(t, err)
+
+		res, err := srv.Client().Do(req)
+		require.NoError(t, err)
+		defer res.Body.Close()
+		require.Equal(t, http.StatusOK, res.StatusCode)
+
+		resBody, err := io.ReadAll(res.Body)
+		require.NoError(t, err)
+		require.Contains(t, string(resBody), "<h1>magicsock</h1>")
+	})
+
+	t.Run("MagicsockDebugLogging", func(t *testing.T) {
+		t.Parallel()
+
+		t.Run("Enable", func(t *testing.T) {
+			t.Parallel()
+
+			ctx := testutil.Context(t, testutil.WaitLong)
+			req, err := http.NewRequestWithContext(ctx, http.MethodGet, srv.URL+"/debug/magicsock/debug-logging/t", nil)
+			require.NoError(t, err)
+
+			res, err := srv.Client().Do(req)
+			require.NoError(t, err)
+			defer res.Body.Close()
+			require.Equal(t, http.StatusOK, res.StatusCode)
+
+			resBody, err := io.ReadAll(res.Body)
+			require.NoError(t, err)
+			require.Contains(t, string(resBody), "updated magicsock debug logging to true")
+		})
+
+		t.Run("Disable", func(t *testing.T) {
+			t.Parallel()
+
+			ctx := testutil.Context(t, testutil.WaitLong)
+			req, err := http.NewRequestWithContext(ctx, http.MethodGet, srv.URL+"/debug/magicsock/debug-logging/0", nil)
+			require.NoError(t, err)
+
+			res, err := srv.Client().Do(req)
+			require.NoError(t, err)
+			defer res.Body.Close()
+			require.Equal(t, http.StatusOK, res.StatusCode)
+
+			resBody, err := io.ReadAll(res.Body)
+			require.NoError(t, err)
+			require.Contains(t, string(resBody), "updated magicsock debug logging to false")
+		})
+
+		t.Run("Invalid", func(t *testing.T) {
+			t.Parallel()
+
+			ctx := testutil.Context(t, testutil.WaitLong)
+			req, err := http.NewRequestWithContext(ctx, http.MethodGet, srv.URL+"/debug/magicsock/debug-logging/blah", nil)
+			require.NoError(t, err)
+
+			res, err := srv.Client().Do(req)
+			require.NoError(t, err)
+			defer res.Body.Close()
+			require.Equal(t, http.StatusBadRequest, res.StatusCode)
+
+			resBody, err := io.ReadAll(res.Body)
+			require.NoError(t, err)
+			require.Contains(t, string(resBody), `invalid state "blah", must be a boolean`)
+		})
+	})
+}
+
 func setupSSHCommand(t *testing.T, beforeArgs []string, afterArgs []string) (*ptytest.PTYCmd, pty.Process) {
 	//nolint:dogsled
 	agentConn, _, _, _, _ := setupAgent(t, agentsdk.Manifest{}, 0)
@@ -2013,7 +2103,7 @@ func setupAgent(t *testing.T, metadata agentsdk.Manifest, ptyTimeout time.Durati
 	*agenttest.Client,
 	<-chan *agentsdk.Stats,
 	afero.Fs,
-	io.Closer,
+	agent.Agent,
 ) {
 	logger := slogtest.Make(t, nil).Leveled(slog.LevelDebug)
 	if metadata.DERPMap == nil {
diff --git a/tailnet/conn.go b/tailnet/conn.go
index 089a83ff79ff9..9315e3ba4abf7 100644
--- a/tailnet/conn.go
+++ b/tailnet/conn.go
@@ -8,6 +8,7 @@ import (
 	"net"
 	"net/http"
 	"net/netip"
+	"os"
 	"reflect"
 	"strconv"
 	"sync"
@@ -51,6 +52,14 @@ const (
 	WorkspaceAgentSpeedtestPort       = 3
 )
 
+// EnvMagicsockDebugLogging enables super-verbose logging for the magicsock
+// internals. A logger must be supplied to the connection with the debug level
+// enabled.
+//
+// With this disabled, you still get a lot of output if you have a valid logger
+// with the debug level enabled.
+const EnvMagicsockDebugLogging = "CODER_MAGICSOCK_DEBUG_LOGGING"
+
 func init() {
 	// Globally disable network namespacing. All networking happens in
 	// userspace.
@@ -175,6 +184,13 @@ func NewConn(options *Options) (conn *Conn, err error) {
 		magicConn.SetDERPHeader(options.DERPHeader.Clone())
 	}
 
+	if v, ok := os.LookupEnv(EnvMagicsockDebugLogging); ok {
+		vBool, err := strconv.ParseBool(v)
+		if err == nil {
+			magicConn.SetDebugLoggingEnabled(vBool)
+		}
+	}
+
 	// Update the keys for the magic connection!
 	err = magicConn.SetPrivateKey(nodePrivateKey)
 	if err != nil {
@@ -361,6 +377,10 @@ type Conn struct {
 	trafficStats *connstats.Statistics
 }
 
+func (c *Conn) MagicsockSetDebugLoggingEnabled(enabled bool) {
+	c.magicConn.SetDebugLoggingEnabled(enabled)
+}
+
 func (c *Conn) SetAddresses(ips []netip.Prefix) error {
 	c.mutex.Lock()
 	defer c.mutex.Unlock()

From c21e19db0e72a689fc6bd4af33141efe12c908ff Mon Sep 17 00:00:00 2001
From: Dean Sheather <dean@deansheather.com>
Date: Tue, 8 Aug 2023 17:35:35 +0000
Subject: [PATCH 2/2] fixup! chore: add debug endpoint on agent to enable
 magicsock debug logging

---
 tailnet/conn.go | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/tailnet/conn.go b/tailnet/conn.go
index 9315e3ba4abf7..ebe57d2606b1c 100644
--- a/tailnet/conn.go
+++ b/tailnet/conn.go
@@ -186,9 +186,14 @@ func NewConn(options *Options) (conn *Conn, err error) {
 
 	if v, ok := os.LookupEnv(EnvMagicsockDebugLogging); ok {
 		vBool, err := strconv.ParseBool(v)
-		if err == nil {
+		if err != nil {
+			options.Logger.Debug(context.Background(), fmt.Sprintf("magicsock debug logging disabled due to invalid value %s=%q, use true or false", EnvMagicsockDebugLogging, v))
+		} else {
 			magicConn.SetDebugLoggingEnabled(vBool)
+			options.Logger.Debug(context.Background(), fmt.Sprintf("magicsock debug logging set by %s=%t", EnvMagicsockDebugLogging, vBool))
 		}
+	} else {
+		options.Logger.Debug(context.Background(), fmt.Sprintf("magicsock debug logging disabled, use %s=true to enable", EnvMagicsockDebugLogging))
 	}
 
 	// Update the keys for the magic connection!