net/traffic,ipn/ipnlocal: extract traffic steering utilities (#19682)

The traffic package contains helpers for evaluating traffic steering scores and picking appropriate nodes. These were extracted from ipnlocal.suggestExitNodeUsingTrafficSteering so they can be reused by the new routecheck package to probe exit nodes in priority order. Updates #17366 Updates tailscale/corp#33033 Signed-off-by: Simon Law <sfllaw@tailscale.com>
2026-05-21 08:28:27 -07:00
parent dbe92f98b5
commit 7ebca58042
9 changed files with 276 additions and 43 deletions
@@ -0,0 +1,139 @@
+// Copyright (c) Tailscale Inc & contributors
+// SPDX-License-Identifier: BSD-3-Clause
+
+package traffic_test
+
+import (
+	"maps"
+	"testing"
+
+	gocmp "github.com/google/go-cmp/cmp"
+	"tailscale.com/net/traffic"
+	"tailscale.com/tailcfg"
+)
+
+// WantScores is a convenience alias for the type of [traffic.Score.scores].
+type wantScores = map[tailcfg.NodeID]traffic.Score
+
+var scoresCases = []struct {
+	name  string
+	peers []*tailcfg.Node
+	want  wantScores
+}{
+	{
+		name:  "none",
+		peers: nil,
+		want:  wantScores{},
+	},
+	{
+		name: "no-scores",
+		peers: []*tailcfg.Node{
+			{ID: 37},
+			{ID: 42},
+		},
+		want: wantScores{
+			37: 0,
+			42: 0,
+		},
+	},
+	{
+		name: "mixed-scores",
+		peers: []*tailcfg.Node{
+			{ID: 37},
+			{
+				ID: 42,
+				Hostinfo: (&tailcfg.Hostinfo{
+					Location: &tailcfg.Location{Priority: 1},
+				}).View(),
+			},
+		},
+		want: wantScores{
+			37: 0,
+			42: 1,
+		},
+	},
+}
+
+func TestScoreOne(t *testing.T) {
+	for _, tc := range scoresCases {
+		if len(tc.peers) == 0 {
+			continue
+		}
+		t.Run(tc.name, func(t *testing.T) {
+			selfID := tailcfg.NodeID(1)
+			ss := traffic.ScoresFor(selfID, nil)
+			for _, n := range tc.peers {
+				want := tc.want[n.ID]
+				score := ss.Score(n.View())
+				if score != want {
+					t.Errorf("initial Score for nodeid:%d: score %d, want %d", n.ID, score, want)
+				}
+				score = ss.Score(n.View())
+				if score != want {
+					t.Errorf("subsequent Score for nodeid:%d: score %d, want %d", n.ID, score, want)
+				}
+			}
+			got := maps.Collect(ss.All())
+			if diff := gocmp.Diff(tc.want, got); diff != "" {
+				t.Errorf("-want +got:\n%s", diff)
+			}
+		})
+	}
+}
+
+func TestScoreMany(t *testing.T) {
+	for _, tc := range scoresCases {
+		t.Run(tc.name, func(t *testing.T) {
+			selfID := tailcfg.NodeID(1)
+			var peers []tailcfg.NodeView
+			for _, n := range tc.peers {
+				peers = append(peers, n.View())
+			}
+
+			t.Run("ScoresFor", func(t *testing.T) {
+				ss := traffic.ScoresFor(selfID, peers)
+				got := maps.Collect(ss.All())
+				if diff := gocmp.Diff(tc.want, got); diff != "" {
+					t.Errorf("-want +got:\n%s", diff)
+				}
+			})
+
+			t.Run("ScorePeers", func(t *testing.T) {
+				ss := traffic.ScoresFor(selfID, nil)
+				ss.ScorePeers(peers)
+				got := maps.Collect(ss.All())
+				if diff := gocmp.Diff(tc.want, got); diff != "" {
+					t.Errorf("-want +got:\n%s", diff)
+				}
+			})
+		})
+	}
+}
+
+func FuzzNodeHasherCompare(f *testing.F) {
+	for _, seed := range [][]uint64{
+		{0, 0, 0},
+		{1, 1, 1},
+		{1, 10, 11},
+		{1, 11, 10},
+		{2, 10, 11},
+	} {
+		selfID, aID, bID := seed[0], seed[1], seed[2]
+		f.Add(selfID, aID, bID)
+	}
+	f.Fuzz(func(t *testing.T, selfID, aID, bID uint64) {
+		t.Logf("selfID %d, aID %d, bID %d", selfID, aID, bID)
+		h := traffic.MakeRendezvousHasher(tailcfg.NodeID(selfID))
+		a, b := tailcfg.NodeID(aID), tailcfg.NodeID(bID)
+		c := h.Compare(a, b)
+		if c == 0 && a != b {
+			t.Fatalf("got %d: expected different hashes because a ≠ b, ", c)
+		}
+		if cc := h.Compare(a, b); c != cc {
+			t.Fatalf("c %d, cc %d: expected matching values", c, cc)
+		}
+		if d := h.Compare(b, a); c != -d {
+			t.Fatalf("c %d, d %d: expected inverse values", c, d)
+		}
+	})
+}