Hardware fixes: rpi_volt under-voltage fallback, dnsmasq except-interface=lo, installer AP check after iw install

internal/netgen/netgen.go

@@ -92,6 +92,7 @@ func DnsmasqConf(n config.Network) string {
 	w("# Managed by PiLens. Changes are overwritten; use the PiLens UI.")
 	w("interface=%s", n.AP.Interface)
 	w("bind-dynamic") // only the AP interface; survives the address appearing late
+	w("except-interface=lo") // dnsmasq otherwise adds loopback implicitly
 	w("no-hosts")
 	w("domain-needed")
 	w("bogus-priv")

internal/sysinfo/sysinfo.go

@@ -231,6 +231,21 @@ func ReadHealth(paths map[string]string) Health {
 			}
 		}
 	}
+	if h.Throttled == "" {
+		// vcgencmd needs /dev/vcio (root only on recent Pi OS). The rpi_volt hwmon
+		// under-voltage alarm is world-readable, so report that instead.
+		h.Throttled = "vcgencmd unavailable to the service user"
+		if m, _ := filepath.Glob("/sys/class/hwmon/hwmon*"); len(m) > 0 {
+			for _, d := range m {
+				if readTrim(d+"/name") == "rpi_volt" {
+					h.Throttled = "under-voltage alarm (rpi_volt): " + readTrim(d+"/in0_lcrit_alarm")
+					if readTrim(d+"/in0_lcrit_alarm") == "1" {
+						h.ThrottleBits = append(h.ThrottleBits, "under-voltage detected now")
+					}
+				}
+			}
+		}
+	}
 	h.Load = readTrim("/proc/loadavg")
 	up := strings.Fields(readTrim("/proc/uptime"))
 	if len(up) > 0 {

scripts/install.sh

@@ -83,9 +83,7 @@ echo "    (a wired network is not trusted just because it is wired; narrow this
 
 # ---------------------------------------------------------------- 3-5. capabilities, resources, conflicts
 say "Checking Wi-Fi, resources and conflicts"
-if command -v iw >/dev/null && [ -n "$WIFI" ]; then
+[ -z "$WIFI" ] && warn "no Wi-Fi interface found; the access point cannot be configured"
-  iw list 2>/dev/null | awk '/Supported interface modes/{f=1;next} f&&/^\t\t\*/{print} f&&!/^\t\t\*/{f=0}' | grep -q '\* AP$' && echo "    AP mode supported" || warn "Wi-Fi radio does not report AP mode support"
-elif [ -z "$WIFI" ]; then warn "no Wi-Fi interface found; the access point cannot be configured"; fi
 FREE_MB=$(df -Pm / | awk 'NR==2{print $4}'); MEM_MB=$(awk '/MemTotal/{print int($2/1024)}' /proc/meminfo)
 echo "    free disk ${FREE_MB} MiB, memory ${MEM_MB} MiB"
 [ "$FREE_MB" -ge 1024 ] || die "at least 1 GiB free disk space is required"
@@ -154,7 +152,12 @@ export DEBIAN_FRONTEND=noninteractive
 apt-get update -qq >>"$LOG" 2>&1 || warn "apt-get update failed; trying with cached package lists"
 apt-get install -y -qq --no-install-recommends tshark wireshark-common nftables dnsmasq-base iw ca-certificates >>"$LOG" 2>&1 || die "apt-get install failed (see $LOG)"
 dpkg-reconfigure -f noninteractive wireshark-common >>"$LOG" 2>&1 || true
-getcap /usr/bin/dumpcap | grep -q cap_net_raw || die "dumpcap has no capture capabilities after install (getcap /usr/bin/dumpcap)"
+
+if [ -n "$WIFI" ]; then
+  /usr/sbin/iw list 2>/dev/null | awk '/Supported interface modes/{f=1;next} f&&/^\t\t\*/{print} f&&!/^\t\t\*/{f=0}' | grep -q '\* AP$' \
+    && echo "    Wi-Fi radio supports AP mode" || warn "Wi-Fi radio does not report AP mode support: the access point may not start"
+fi
+/usr/sbin/getcap /usr/bin/dumpcap | grep -q cap_net_raw || die "dumpcap has no capture capabilities after install (getcap /usr/bin/dumpcap)"
 # dnsmasq-base must not bring a competing system dnsmasq service.
 systemctl is-enabled --quiet dnsmasq 2>/dev/null && warn "dnsmasq.service (full package) is enabled. Disable it, or make sure it does not listen on the AP interface."