control/controlclient: flesh out mapSession to break up gigantic method

Now mapSession has a bunch more fields and methods, rather than being
just one massive func with a ton of local variables.

So far there are no major new optimizations, though. It should behave
the same as before.

This has been done with an eye towards testability (so tests can set
all the callback funcs as needed, or not, without a huge Direct client
or long-running HTTP requests), but this change doesn't add new tests
yet. That will follow in the changes which flesh out the NetmapUpdater
interface.

Updates #1909

Change-Id: Iad4e7442d5bbbe2614bd4b1dc4b02e27504898df
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

control/controlclient/map_test.go

@@ -4,10 +4,13 @@
 package controlclient
 
 import (
+	"context"
 	"encoding/json"
 	"fmt"
+	"net/netip"
 	"reflect"
 	"strings"
+	"sync/atomic"
 	"testing"
 	"time"
 
@@ -330,8 +333,9 @@ func formatNodes(nodes []*tailcfg.Node) string {
 	return sb.String()
 }
 
-func newTestMapSession(t *testing.T) *mapSession {
-	ms := newMapSession(key.NewNode())
+func newTestMapSession(t testing.TB, nu NetmapUpdater) *mapSession {
+	ms := newMapSession(key.NewNode(), nu)
+	t.Cleanup(ms.Close)
 	ms.logf = t.Logf
 	return ms
 }
@@ -346,7 +350,7 @@ func TestNetmapForResponse(t *testing.T) {
 				},
 			},
 		}
-		ms := newTestMapSession(t)
+		ms := newTestMapSession(t, nil)
 		nm1 := ms.netmapForResponse(&tailcfg.MapResponse{
 			Node:         new(tailcfg.Node),
 			PacketFilter: somePacketFilter,
@@ -367,7 +371,7 @@ func TestNetmapForResponse(t *testing.T) {
 	})
 	t.Run("implicit_dnsconfig", func(t *testing.T) {
 		someDNSConfig := &tailcfg.DNSConfig{Domains: []string{"foo", "bar"}}
-		ms := newTestMapSession(t)
+		ms := newTestMapSession(t, nil)
 		nm1 := ms.netmapForResponse(&tailcfg.MapResponse{
 			Node:      new(tailcfg.Node),
 			DNSConfig: someDNSConfig,
@@ -384,7 +388,7 @@ func TestNetmapForResponse(t *testing.T) {
 		}
 	})
 	t.Run("collect_services", func(t *testing.T) {
-		ms := newTestMapSession(t)
+		ms := newTestMapSession(t, nil)
 		var nm *netmap.NetworkMap
 		wantCollect := func(v bool) {
 			t.Helper()
@@ -417,7 +421,7 @@ func TestNetmapForResponse(t *testing.T) {
 		wantCollect(true)
 	})
 	t.Run("implicit_domain", func(t *testing.T) {
-		ms := newTestMapSession(t)
+		ms := newTestMapSession(t, nil)
 		var nm *netmap.NetworkMap
 		want := func(v string) {
 			t.Helper()
@@ -445,7 +449,7 @@ func TestNetmapForResponse(t *testing.T) {
 			ComputedName:         "foo",
 			ComputedNameWithHost: "foo",
 		}
-		ms := newTestMapSession(t)
+		ms := newTestMapSession(t, nil)
 		mapRes := &tailcfg.MapResponse{
 			Node: someNode,
 		}
@@ -564,7 +568,7 @@ func TestDeltaDERPMap(t *testing.T) {
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			ms := newTestMapSession(t)
+			ms := newTestMapSession(t, nil)
 			for stepi, s := range tt.steps {
 				nm := ms.netmapForResponse(&tailcfg.MapResponse{DERPMap: s.got})
 				if !reflect.DeepEqual(nm.DERPMap, s.want) {
@@ -574,3 +578,64 @@ func TestDeltaDERPMap(t *testing.T) {
 		})
 	}
 }
+
+type countingNetmapUpdater struct {
+	full atomic.Int64
+}
+
+func (nu *countingNetmapUpdater) UpdateFullNetmap(nm *netmap.NetworkMap) {
+	nu.full.Add(1)
+}
+
+func BenchmarkMapSessionDelta(b *testing.B) {
+	for _, size := range []int{10, 100, 1_000, 10_000} {
+		b.Run(fmt.Sprintf("size_%d", size), func(b *testing.B) {
+			ctx := context.Background()
+			nu := &countingNetmapUpdater{}
+			ms := newTestMapSession(b, nu)
+			res := &tailcfg.MapResponse{
+				Node: &tailcfg.Node{
+					ID:   1,
+					Name: "foo.bar.ts.net.",
+				},
+			}
+			for i := 0; i < size; i++ {
+				res.Peers = append(res.Peers, &tailcfg.Node{
+					ID:         tailcfg.NodeID(i + 2),
+					Name:       fmt.Sprintf("peer%d.bar.ts.net.", i),
+					DERP:       "127.3.3.40:10",
+					Addresses:  []netip.Prefix{netip.MustParsePrefix("100.100.2.3/32"), netip.MustParsePrefix("fd7a:115c:a1e0::123/128")},
+					AllowedIPs: []netip.Prefix{netip.MustParsePrefix("100.100.2.3/32"), netip.MustParsePrefix("fd7a:115c:a1e0::123/128")},
+					Endpoints:  []string{"192.168.1.2:345", "192.168.1.3:678"},
+					Hostinfo: (&tailcfg.Hostinfo{
+						OS:       "fooOS",
+						Hostname: "MyHostname",
+						Services: []tailcfg.Service{
+							{Proto: "peerapi4", Port: 1234},
+							{Proto: "peerapi6", Port: 1234},
+							{Proto: "peerapi-dns-proxy", Port: 1},
+						},
+					}).View(),
+					LastSeen: ptr.To(time.Unix(int64(i), 0)),
+				})
+			}
+			ms.HandleNonKeepAliveMapResponse(ctx, res)
+
+			b.ResetTimer()
+			b.ReportAllocs()
+
+			// Now for the core of the benchmark loop, just toggle
+			// a single node's online status.
+			for i := 0; i < b.N; i++ {
+				if err := ms.HandleNonKeepAliveMapResponse(ctx, &tailcfg.MapResponse{
+					OnlineChange: map[tailcfg.NodeID]bool{
+						2: i%2 == 0,
+					},
+				}); err != nil {
+					b.Fatal(err)
+				}
+			}
+		})
+	}
+
+}