derp: make RunConnectionLoop funcs take Messages, support PeerPresentFlags

PeerPresentFlags was added in 5ffb2668ef but wasn't plumbed through to
the RunConnectionLoop. Rather than add yet another parameter (as
IP:port was added earlier), pass in the raw PeerPresentMessage and
PeerGoneMessage struct values, which are the same things, plus two
fields: PeerGoneReasonType for gone and the PeerPresentFlags from
5ffb2668ef.

Updates tailscale/corp#17816

Change-Id: Ib19d9f95353651ada90656071fc3656cf58b7987
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

cmd/derper/mesh.go

@@ -9,14 +9,12 @@ import (
 	"fmt"
 	"log"
 	"net"
-	"net/netip"
 	"strings"
 	"time"
 
 	"tailscale.com/derp"
 	"tailscale.com/derp/derphttp"
 	"tailscale.com/net/netmon"
-	"tailscale.com/types/key"
 	"tailscale.com/types/logger"
 )
 
@@ -71,8 +69,8 @@ func startMeshWithHost(s *derp.Server, host string) error {
 		return d.DialContext(ctx, network, addr)
 	})
 
-	add := func(k key.NodePublic, _ netip.AddrPort) { s.AddPacketForwarder(k, c) }
-	remove := func(k key.NodePublic) { s.RemovePacketForwarder(k, c) }
+	add := func(m derp.PeerPresentMessage) { s.AddPacketForwarder(m.Key, c) }
+	remove := func(m derp.PeerGoneMessage) { s.RemovePacketForwarder(m.Peer, c) }
 	go c.RunWatchConnectionLoop(context.Background(), s.PublicKey(), logf, add, remove)
 	return nil
 }

derp/derp.go

@@ -131,8 +131,9 @@ const (
 type PeerGoneReasonType byte
 
 const (
-	PeerGoneReasonDisconnected = PeerGoneReasonType(0x00) // peer disconnected from this server
-	PeerGoneReasonNotHere      = PeerGoneReasonType(0x01) // server doesn't know about this peer, unexpected
+	PeerGoneReasonDisconnected  = PeerGoneReasonType(0x00) // peer disconnected from this server
+	PeerGoneReasonNotHere       = PeerGoneReasonType(0x01) // server doesn't know about this peer, unexpected
+	PeerGoneReasonMeshConnBroke = PeerGoneReasonType(0xf0) // invented by Client.RunWatchConnectionLoop on disconnect; not sent on the wire
 )
 
 // PeerPresentFlags is an optional byte of bit flags sent after a framePeerPresent message.

derp/derphttp/derphttp_test.go

@@ -11,7 +11,6 @@ import (
 	"net"
 	"net/http"
 	"net/http/httptest"
-	"net/netip"
 	"sync"
 	"testing"
 	"time"
@@ -299,13 +298,13 @@ func TestBreakWatcherConnRecv(t *testing.T) {
 	go func() {
 		defer wg.Done()
 		var peers int
-		add := func(k key.NodePublic, _ netip.AddrPort) {
-			t.Logf("add: %v", k.ShortString())
+		add := func(m derp.PeerPresentMessage) {
+			t.Logf("add: %v", m.Key.ShortString())
 			peers++
 			// Signal that the watcher has run
 			watcherChan <- peers
 		}
-		remove := func(k key.NodePublic) { t.Logf("remove: %v", k.ShortString()); peers-- }
+		remove := func(m derp.PeerGoneMessage) { t.Logf("remove: %v", m.Peer.ShortString()); peers-- }
 
 		watcher1.RunWatchConnectionLoop(ctx, serverPrivateKey1.Public(), t.Logf, add, remove)
 	}()
@@ -370,15 +369,15 @@ func TestBreakWatcherConn(t *testing.T) {
 	go func() {
 		defer wg.Done()
 		var peers int
-		add := func(k key.NodePublic, _ netip.AddrPort) {
-			t.Logf("add: %v", k.ShortString())
+		add := func(m derp.PeerPresentMessage) {
+			t.Logf("add: %v", m.Key.ShortString())
 			peers++
 			// Signal that the watcher has run
 			watcherChan <- peers
 			// Wait for breaker to run
 			<-breakerChan
 		}
-		remove := func(k key.NodePublic) { t.Logf("remove: %v", k.ShortString()); peers-- }
+		remove := func(m derp.PeerGoneMessage) { t.Logf("remove: %v", m.Peer.ShortString()); peers-- }
 
 		watcher1.RunWatchConnectionLoop(ctx, serverPrivateKey1.Public(), t.Logf, add, remove)
 	}()
@@ -407,8 +406,8 @@ func TestBreakWatcherConn(t *testing.T) {
 	}
 }
 
-func noopAdd(key.NodePublic, netip.AddrPort) {}
-func noopRemove(key.NodePublic)              {}
+func noopAdd(derp.PeerPresentMessage) {}
+func noopRemove(derp.PeerGoneMessage) {}
 
 func TestRunWatchConnectionLoopServeConnect(t *testing.T) {
 	defer func() { testHookWatchLookConnectResult = nil }()

derp/derphttp/mesh_client.go

@@ -5,7 +5,6 @@ package derphttp
 
 import (
 	"context"
-	"net/netip"
 	"sync"
 	"time"
 
@@ -35,9 +34,14 @@ var testHookWatchLookConnectResult func(connectError error, wasSelfConnect bool)
 // To force RunWatchConnectionLoop to return quickly, its ctx needs to be
 // closed, and c itself needs to be closed.
 //
-// It is a fatal error to call this on an already-started Client withoutq having
+// It is a fatal error to call this on an already-started Client without having
 // initialized Client.WatchConnectionChanges to true.
-func (c *Client) RunWatchConnectionLoop(ctx context.Context, ignoreServerKey key.NodePublic, infoLogf logger.Logf, add func(key.NodePublic, netip.AddrPort), remove func(key.NodePublic)) {
+//
+// If the DERP connection breaks and reconnects, remove will be called for all
+// previously seen peers, with Reason type PeerGoneReasonSynthetic. Those
+// clients are likely still connected and their add message will appear after
+// reconnect.
+func (c *Client) RunWatchConnectionLoop(ctx context.Context, ignoreServerKey key.NodePublic, infoLogf logger.Logf, add func(derp.PeerPresentMessage), remove func(derp.PeerGoneMessage)) {
 	if !c.WatchConnectionChanges {
 		if c.isStarted() {
 			panic("invalid use of RunWatchConnectionLoop on already-started Client without setting Client.RunWatchConnectionLoop")
@@ -62,7 +66,7 @@ func (c *Client) RunWatchConnectionLoop(ctx context.Context, ignoreServerKey key
 		}
 		logf("reconnected; clearing %d forwarding mappings", len(present))
 		for k := range present {
-			remove(k)
+			remove(derp.PeerGoneMessage{Peer: k, Reason: derp.PeerGoneReasonMeshConnBroke})
 		}
 		present = map[key.NodePublic]bool{}
 	}
@@ -84,13 +88,7 @@ func (c *Client) RunWatchConnectionLoop(ctx context.Context, ignoreServerKey key
 	})
 	defer timer.Stop()
 
-	updatePeer := func(k key.NodePublic, ipPort netip.AddrPort, isPresent bool) {
-		if isPresent {
-			add(k, ipPort)
-		} else {
-			remove(k)
-		}
-
+	updatePeer := func(k key.NodePublic, isPresent bool) {
 		mu.Lock()
 		defer mu.Unlock()
 		if isPresent {
@@ -148,7 +146,8 @@ func (c *Client) RunWatchConnectionLoop(ctx context.Context, ignoreServerKey key
 			}
 			switch m := m.(type) {
 			case derp.PeerPresentMessage:
-				updatePeer(m.Key, m.IPPort, true)
+				add(m)
+				updatePeer(m.Key, true)
 			case derp.PeerGoneMessage:
 				switch m.Reason {
 				case derp.PeerGoneReasonDisconnected:
@@ -160,7 +159,8 @@ func (c *Client) RunWatchConnectionLoop(ctx context.Context, ignoreServerKey key
 					logf("Recv: peer %s not at server %s for unknown reason %v",
 						key.NodePublic(m.Peer).ShortString(), c.ServerPublicKey().ShortString(), m.Reason)
 				}
-				updatePeer(key.NodePublic(m.Peer), netip.AddrPort{}, false)
+				remove(m)
+				updatePeer(m.Peer, false)
 			default:
 				continue
 			}