OpenWrt agent: add temperature sensors and harden wireless SNMP setup

snmp/Openwrt/README.md

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+# OpenWrt wireless + sensors SNMP agent
+
+These scripts expose per-radio and aggregate wireless metrics (plus lm-sensors
+temperatures) to LibreNMS through net-snmp `pass_persist` handlers. Radios and
+VAPs are discovered live at request time, so there is no per-interface or
+per-metric snmpd configuration to maintain. See
+[Device-Notes/Openwrt.md](https://docs.librenms.org/Support/Device-Notes/#openwrt)
+for the LibreNMS-side install and discovery steps.
+
+## Scripts
+
+| Script | Purpose |
+| --- | --- |
+| `openwrt-snmp-pass.sh` | Wireless `pass_persist` handler. Serves the OpenWrt wireless subtree (OPENWRT-WIRELESS-MIB, `.1.3.6.1.4.1.60652.102.1.10`) from a single snmpd line. |
+| `lm-sensors-pass.sh` | Temperature `pass_persist` handler (LM-SENSORS-MIB emulation). |
+| `wlInterfaces.sh` | Interface/label inventory. Helper used by `openwrt-snmp-pass.sh`. |
+| `wlClients.sh [iface]` | Client counts (per interface, or aggregate). Helper. |
+| `wlFrequency.sh <iface>` | Channel frequency (MHz). Helper. |
+| `wlNoiseFloor.sh <iface>` | Noise floor (dBm). Helper. |
+| `wlRate.sh <iface> <tx\|rx> <min\|avg\|max>` | TX/RX rate (Mbit/s). Helper. |
+| `wlSNR.sh <iface> <min\|avg\|max>` | SNR (dB). Helper. |
+
+The `wl*.sh` scripts are collection helpers invoked by `openwrt-snmp-pass.sh`;
+they are not registered with snmpd directly. They can be run standalone for
+debugging.
+
+## snmpd configuration
+
+Copy the scripts to a directory on the device (the helpers must sit next to
+`openwrt-snmp-pass.sh`, which calls them by relative path):
+
+```sh
+mkdir -p /usr/libexec/openwrt-snmp
+for s in openwrt-snmp-pass lm-sensors-pass wlInterfaces wlClients \
+         wlFrequency wlNoiseFloor wlRate wlSNR; do
+  wget -O "/usr/libexec/openwrt-snmp/$s.sh" \
+    "https://raw.githubusercontent.com/librenms/librenms-agent/master/snmp/Openwrt/$s.sh"
+done
+chmod +x /usr/libexec/openwrt-snmp/*.sh
+```
+
+Register the two handlers in `/etc/config/snmpd`:
+
+```
+config pass
+	option miboid '.1.3.6.1.4.1.60652.102.1.10'
+	option prog '/usr/libexec/openwrt-snmp/openwrt-snmp-pass.sh'
+	option persist '1'
+
+config pass
+	option miboid '.1.3.6.1.4.1.2021.13.16.2.1'
+	option prog '/usr/libexec/openwrt-snmp/lm-sensors-pass.sh'
+	option persist '1'
+```
+
+OS detection additionally reads a `distro` and a `hardware` extend
+(`nsExtendOutput1Line."distro"` / `."hardware"`); these use small inline
+commands rather than shipped scripts:
+
+```
+config extend
+	option name 'distro'
+	option prog '/bin/sh'
+	option args '-c '\''. /etc/os-release; echo $PRETTY_NAME'\'''
+
+config extend
+	option name 'hardware'
+	option prog '/bin/cat'
+	option args '/tmp/sysinfo/model'
+```
+
+(`/tmp/sysinfo/model` is OpenWrt's board-detection model string; it works on all
+targets including x86, unlike `/sys/firmware/devicetree/base/model`.)
+
+Restart snmpd:
+
+```sh
+/etc/init.d/snmpd restart
+```
+
+## Validation
+
+From the LibreNMS host, walk the wireless subtree and the temperature table:
+
+```sh
+snmpwalk -v2c -c your_community_string <openwrt-host> .1.3.6.1.4.1.60652.102.1.10
+snmpwalk -v2c -c your_community_string <openwrt-host> .1.3.6.1.4.1.2021.13.16
+```
+
+On the device, the handler can be exercised directly:
+
+```sh
+/usr/libexec/openwrt-snmp/openwrt-snmp-pass.sh --snapshot        # full OID table
+/usr/libexec/openwrt-snmp/openwrt-snmp-pass.sh -g <oid>          # single GET
+/usr/libexec/openwrt-snmp/openwrt-snmp-pass.sh -n <oid>          # GETNEXT
+```

snmp/Openwrt/lm-sensors-pass.sh

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+#!/bin/sh
+
+# lm-sensors-pass.sh
+# SNMP pass script for LM-SENSORS-MIB thermal sensors
+# Provides proper MIB structure at .1.3.6.1.4.1.2021.13.16.2.1
+
+BASE_OID=".1.3.6.1.4.1.2021.13.16.2.1"
+
+# Function to get all thermal zone data
+# Output format: index:name:temp
+# Re-indexes zones sequentially starting from 1
+get_zones() {
+    idx=0
+    for zone in /sys/devices/virtual/thermal/thermal_zone*; do
+        [ -d "$zone" ] || continue
+        idx=$((idx + 1))
+        zone_type=$(cat "$zone/type" 2>/dev/null || echo "unknown")
+        zone_temp=$(cat "$zone/temp" 2>/dev/null || echo "0")
+        echo "$idx:$zone_type:$zone_temp"
+    done | sort -t':' -k1 -n
+}
+
+case "$1" in
+    -g)
+        # GET request - return exact OID match
+        REQ_OID="$2"
+        FOUND=0
+
+        while IFS=':' read -r idx name temp; do
+            case "$REQ_OID" in
+                "$BASE_OID.1.$idx")
+                    echo "$REQ_OID"
+                    echo "integer"
+                    echo "$idx"
+                    FOUND=1
+                    break
+                    ;;
+                "$BASE_OID.2.$idx")
+                    echo "$REQ_OID"
+                    echo "string"
+                    echo "$name"
+                    FOUND=1
+                    break
+                    ;;
+                "$BASE_OID.3.$idx")
+                    echo "$REQ_OID"
+                    echo "gauge"
+                    echo "$temp"
+                    FOUND=1
+                    break
+                    ;;
+            esac
+        done << EOF
+$(get_zones)
+EOF
+
+        [ "$FOUND" -eq 0 ] && echo "NONE"
+        ;;
+
+    -n)
+        # GETNEXT request - return next OID after requested
+        REQ_OID="$2"
+
+        # Create temporary file with all OIDs
+        TMP_FILE="$(mktemp /tmp/snmp_oids.XXXXXX 2>/dev/null || echo "/tmp/snmp_oids.$$")"
+        TMP_SORTED="${TMP_FILE}.sorted"
+        TMP_LIST="${TMP_FILE}.list"
+        : > "$TMP_FILE"
+        trap 'rm -f "$TMP_FILE" "$TMP_SORTED" "$TMP_LIST"' EXIT INT TERM
+
+        get_zones | while IFS=':' read -r idx name temp; do
+            # Pad index to ensure proper numeric sorting
+            # Format: column.index where index is zero-padded to 3 digits
+            {
+                printf '%d.%03d|%s.1.%s|integer|%s\n' 1 "$idx" "$BASE_OID" "$idx" "$idx"
+                printf '%d.%03d|%s.2.%s|string|%s\n' 2 "$idx" "$BASE_OID" "$idx" "$name"
+                printf '%d.%03d|%s.3.%s|gauge|%s\n' 3 "$idx" "$BASE_OID" "$idx" "$temp"
+            } >> "$TMP_FILE"
+        done
+
+        # Sort by our padded key, then extract and compare OIDs
+        sort -t'|' -k1 "$TMP_FILE" > "$TMP_SORTED"
+        cut -d'|' -f2- "$TMP_SORTED" > "$TMP_LIST"
+
+        FOUND=0
+        while IFS='|' read -r oid type value; do
+            # Use awk for proper numeric OID comparison
+            is_greater=$(awk -v req="$REQ_OID" -v curr="$oid" '
+                BEGIN {
+                    # Split OIDs into arrays
+                    req_len = split(req, req_parts, ".");
+                    curr_len = split(curr, curr_parts, ".");
+                    max_len = (curr_len > req_len) ? curr_len : req_len;
+
+                    # Compare each part numerically
+                    for (i = 1; i <= max_len; i++) {
+                        req_val = (i <= req_len) ? req_parts[i] : 0;
+                        curr_val = (i <= curr_len) ? curr_parts[i] : 0;
+
+                        if (curr_val > req_val) {
+                            print "1";
+                            exit;
+                        } else if (curr_val < req_val) {
+                            print "0";
+                            exit;
+                        }
+                    }
+                    print "0";
+                }
+            ')
+
+            if [ "$is_greater" = "1" ]; then
+                echo "$oid"
+                echo "$type"
+                echo "$value"
+                FOUND=1
+                break
+            fi
+        done < "$TMP_LIST"
+
+        if [ "$FOUND" -eq 0 ]; then
+            echo "NONE"
+        fi
+        ;;
+
+    *)
+        echo "Usage: $0 -g|-n OID" >&2
+        exit 1
+        ;;
+esac