wifi: add SKIP_WIFI env var to disable signal monitoring

agent/wifi/README.md

@@ -3,7 +3,8 @@
 Reports connected station interfaces only (no scans). `info.wf` holds the current
 snapshot keyed by interface (`s` SSID, `r` RSSI in dBm when available);
 `stats.wf` stores available RSSI as integer dBm. Collected on the default
-interval only; real-time requests reuse the last snapshot.
+interval only; real-time requests reuse the last snapshot. Set `SKIP_WIFI=true`
+on the agent to disable collection.
 
 - Linux: nl80211 via `github.com/mdlayher/wifi`. Docker needs `network_mode: host`.
   Skipped when `/sys/class/ieee80211` lists no wireless devices.

agent/wifi/wifi.go

@@ -4,10 +4,13 @@ package wifi
 
 import (
 	"context"
+	"log/slog"
 	"math"
+	"sync"
 	"time"
 	"unicode/utf8"
 
+	"github.com/henrygd/beszel/agent/utils"
 	"github.com/henrygd/beszel/internal/entities/system"
 )
 
@@ -20,10 +23,29 @@ func validSSID(ssid string) string {
 	return ssid
 }
 
+// skipFromEnv reports whether SKIP_WIFI disables collection.
+func skipFromEnv() bool {
+	skip, _ := utils.GetEnv("SKIP_WIFI")
+	return skip == "true"
+}
+
+// skip caches skipFromEnv, as the environment is fixed for the life of the
+// process.
+var skip = sync.OnceValue(func() bool {
+	if !skipFromEnv() {
+		return false
+	}
+	slog.Info("SKIP_WIFI enabled, skipping Wi-Fi signal monitoring")
+	return true
+})
+
 // Collect uses a single deadline across interface queries where supported.
 // Unsupported platforms and denied association access produce no readings;
-// later polls retry.
+// later polls retry. SKIP_WIFI=true disables collection entirely.
 func Collect() map[string]system.WiFi {
+	if skip() {
+		return nil
+	}
 	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
 	defer cancel()
 	return collect(ctx)

agent/wifi/wifi_test.go

@@ -7,6 +7,34 @@ import (
 	"github.com/henrygd/beszel/internal/entities/system"
 )
 
+func TestSkipFromEnv(t *testing.T) {
+	for _, tc := range []struct {
+		key, value string
+		want       bool
+	}{
+		{"SKIP_WIFI", "true", true},
+		{"BESZEL_AGENT_SKIP_WIFI", "true", true},
+		{"SKIP_WIFI", "false", false},
+		{"SKIP_WIFI", "", false},
+	} {
+		t.Run(tc.key+"="+tc.value, func(t *testing.T) {
+			t.Setenv(tc.key, tc.value)
+			if got := skipFromEnv(); got != tc.want {
+				t.Fatalf("got %v, want %v", got, tc.want)
+			}
+		})
+	}
+}
+
+func TestCollectSkipped(t *testing.T) {
+	original := skip
+	t.Cleanup(func() { skip = original })
+	skip = func() bool { return true }
+	if got := Collect(); got != nil {
+		t.Fatalf("collected while skipped: %v", got)
+	}
+}
+
 func TestSSIDWireSafety(t *testing.T) {
 	for _, tc := range []struct{ input, want string }{
 		{"home", "home"}, {"网络 café", "网络 café"}, {"", ""},