ipn,log: add logger for sockstat deltas

Signed-off-by: Will Norris <will@tailscale.com>
Co-authored-by: Melanie Warrick <warrick@tailscale.com>

log/sockstatlog/logger_test.go

@@ -0,0 +1,119 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package sockstatlog
+
+import (
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+	"tailscale.com/net/sockstats"
+)
+
+func TestDelta(t *testing.T) {
+	tests := []struct {
+		name      string
+		a, b      *sockstats.SockStats
+		wantStats map[sockstats.Label]deltaStat
+	}{
+		{
+			name:      "nil a stat",
+			a:         nil,
+			b:         &sockstats.SockStats{},
+			wantStats: nil,
+		},
+		{
+			name:      "nil b stat",
+			a:         &sockstats.SockStats{},
+			b:         nil,
+			wantStats: nil,
+		},
+		{
+			name: "no change",
+			a: &sockstats.SockStats{
+				Stats: map[sockstats.Label]sockstats.SockStat{
+					sockstats.LabelDERPHTTPClient: {
+						TxBytes: 10,
+						TxBytesByInterface: map[string]uint64{
+							"en0": 10,
+						},
+					},
+				},
+			},
+			b: &sockstats.SockStats{
+				Stats: map[sockstats.Label]sockstats.SockStat{
+					sockstats.LabelDERPHTTPClient: {
+						TxBytes: 10,
+						TxBytesByInterface: map[string]uint64{
+							"en0": 10,
+						},
+					},
+				},
+			},
+			wantStats: nil,
+		},
+		{
+			name: "tx after empty stat",
+			a:    &sockstats.SockStats{},
+			b: &sockstats.SockStats{
+				Stats: map[sockstats.Label]sockstats.SockStat{
+					sockstats.LabelDERPHTTPClient: {
+						TxBytes: 10,
+						TxBytesByInterface: map[string]uint64{
+							"en0": 10,
+						},
+					},
+				},
+				Interfaces: []string{"en0"},
+			},
+			wantStats: map[sockstats.Label]deltaStat{
+				sockstats.LabelDERPHTTPClient: {10, 0},
+			},
+		},
+		{
+			name: "rx after non-empty stat",
+			a: &sockstats.SockStats{
+				Stats: map[sockstats.Label]sockstats.SockStat{
+					sockstats.LabelDERPHTTPClient: {
+						TxBytes: 10,
+						RxBytes: 10,
+						TxBytesByInterface: map[string]uint64{
+							"en0": 10,
+						},
+						RxBytesByInterface: map[string]uint64{
+							"en0": 10,
+						},
+					},
+				},
+				Interfaces: []string{"en0"},
+			},
+			b: &sockstats.SockStats{
+				Stats: map[sockstats.Label]sockstats.SockStat{
+					sockstats.LabelDERPHTTPClient: {
+						TxBytes: 10,
+						RxBytes: 30,
+						TxBytesByInterface: map[string]uint64{
+							"en0": 10,
+						},
+						RxBytesByInterface: map[string]uint64{
+							"en0": 30,
+						},
+					},
+				},
+				Interfaces: []string{"en0"},
+			},
+			wantStats: map[sockstats.Label]deltaStat{
+				sockstats.LabelDERPHTTPClient: {0, 20},
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			gotStats := delta(tt.a, tt.b)
+			if !cmp.Equal(gotStats, tt.wantStats) {
+				t.Errorf("gotStats = %v, want %v", gotStats, tt.wantStats)
+			}
+		})
+	}
+}