test: add test for when remote peers switch between client and server…

… modes

dht_test.go

@@ -6,6 +6,7 @@ import (
 	"encoding/binary"
 	"errors"
 	"fmt"
+	"github.com/libp2p/go-libp2p-core/protocol"
 	"math/rand"
 	"sort"
 	"strings"
@@ -1581,6 +1582,44 @@ func TestProvideDisabled(t *testing.T) {
 	}
 }
 
+func TestHandleRemotePeerProtocolChanges(t *testing.T) {
+	proto := protocol.ID("/v1/dht")
+	ctx := context.Background()
+	os := []opts.Option{
+		opts.Protocols(proto),
+		opts.Client(false),
+		opts.NamespacedValidator("v", blankValidator{}),
+		opts.DisableAutoRefresh(),
+	}
+
+	// start host 1 that speaks dht v1
+	dhtA, err := New(ctx, bhost.New(swarmt.GenSwarm(t, ctx, swarmt.OptDisableReuseport)), os...)
+	require.NoError(t, err)
+	defer dhtA.Close()
+
+	// start host 2 that also speaks dht v1
+	dhtB, err := New(ctx, bhost.New(swarmt.GenSwarm(t, ctx, swarmt.OptDisableReuseport)), os...)
+	require.NoError(t, err)
+	defer dhtB.Close()
+
+	connect(t, ctx, dhtA, dhtB)
+
+	// now assert both have each other in their RT
+	require.True(t, waitForWellFormedTables(t, []*IpfsDHT{dhtA, dhtB}, 1, 1, 10*time.Second), "both RT should have one peer each")
+
+	// dhtB becomes a client
+	require.NoError(t, dhtB.SetMode(ModeClient))
+
+	// which means that dhtA should evict it from it's RT
+	require.True(t, waitForWellFormedTables(t, []*IpfsDHT{dhtA}, 0, 0, 10*time.Second), "dHTA routing table should have 0 peers")
+
+	// dhtB becomes a server
+	require.NoError(t, dhtB.SetMode(ModeServer))
+
+	// which means dhtA should have it in the RT again
+	require.True(t, waitForWellFormedTables(t, []*IpfsDHT{dhtA}, 1, 1, 10*time.Second), "dHTA routing table should have 1 peers")
+}
+
 func TestGetSetPluggedProtocol(t *testing.T) {
 	t.Run("PutValue/GetValue - same protocol", func(t *testing.T) {
 		ctx, cancel := context.WithCancel(context.Background())