OpenWrt-LibreNMS

SNMPD OpenWrt configuration - integration for OpenWrt devices to be visible wtih more features in LibreNMS network management platform. Based on https://github.com/librenms/librenms-agent/tree/master/snmp/Openwrt

This package provides unified, auto-detecting SNMP monitoring for OpenWrt devices with support for:

• Wireless interface metrics (clients, frequency, rate, noise, SNR)
• Thermal sensor monitoring (broken)
• Auto-discovery of wireless interfaces
• Dynamic configuration generation

Key Features

1. Auto-Generation of wlInterfaces.txt

wlClients.sh auto-detects all wireless interfaces on first run and generates the file automatically.

# First run automatically creates wlInterfaces.txt
/etc/librenms/wlClients.sh

2. Dynamic Config Generator

Problem: Different devices need different snmpd configs based on their wireless interfaces (ap1: wl0-ap0, wl1-ap0; ap2: wlan0, wlan02, wlan12, wlan22).

Solution: snmpd-config-generator.sh reads wlInterfaces.txt and generates appropriate UCI config entries for all detected interfaces.

# Generate config for current device
/etc/librenms/snmpd-config-generator.sh

3. Unified Base Configuration

Problem: Repetitive config entries across devices.

Solution: snmpd-base-config provides a common base with placeholders for dynamic content.

4. Error Handling

All scripts have:

• Error messages
• Argument validation
• Fallback behavior
• Consistent exit codes

5. Thermal Sensor Support (LM-SENSORS-MIB)

Uses the pass directive to provide proper LM-SENSORS-MIB thermal sensors:

• .1.3.6.1.4.1.2021.13.16.2.1.1 - lmTempSensorsIndex (INTEGER)
• .1.3.6.1.4.1.2021.13.16.2.1.2 - lmTempSensorsDevice (STRING)
• .1.3.6.1.4.1.2021.13.16.2.1.3 - lmTempSensorsValue (Gauge32, millidegrees)

The pass script (lm-sensors-pass.sh) provides proper data types and table structure, enabling automatic discovery in LibreNMS.

File Structure

/etc/librenms/
├── wlInterfaces.txt              # Auto-generated interface list
├── wlClients.sh                  # Count Wi-Fi clients (auto-generates wlInterfaces.txt)
├── wlFrequency.sh                # Get operating frequency
├── wlNoiseFloor.sh               # Get noise floor
├── wlRate.sh                     # Get TX/RX rates (min/avg/max)
├── wlSNR.sh                      # Get SNR (min/avg/max)
├── lm-sensors-pass.sh            # LM-SENSORS-MIB pass script for thermal sensors
├── distro.sh                     # Extract OpenWrt version string
├── cleanup-and-fix.sh            # Remove old exec entries
└── snmpd-config-generator.sh     # Generate UCI config entries

Installation

Quick Setup

# Run setup script
chmod +x setup-snmpd.sh
./setup-snmpd.sh

### Manual Installation
```bash
# Create directory
mkdir -p /etc/librenms

# Copy all scripts
cp wl*.sh thermal-sensors-*.sh snmpd-config-generator.sh /etc/librenms/
chmod +x /etc/librenms/*.sh

# Generate interface list
/etc/librenms/wlClients.sh

# Generate config
/etc/librenms/snmpd-config-generator.sh

Usage

Generate wlInterfaces.txt

# Auto-detect all wireless interfaces
/etc/librenms/wlClients.sh

# Manually edit if needed
vi /etc/librenms/wlInterfaces.txt
# Format: interface,ssid
# Example:
# wl0-ap0,MySSID
# wlan0,GuestNetwork

Generate SNMPD Config

# Generate all extend entries for detected interfaces
/etc/librenms/snmpd-config-generator.sh

# Output can be appended to /etc/config/snmpd
/etc/librenms/snmpd-config-generator.sh >> /etc/config/snmpd

Test Scripts Individually

# Test client count
/etc/librenms/wlClients.sh wlan0

# Test frequency
/etc/librenms/wlFrequency.sh wlan0

# Test rate (interface, direction, stat)
/etc/librenms/wlRate.sh wlan0 tx avg

# Test SNR (interface, stat)
/etc/librenms/wlSNR.sh wlan0 avg

# Test thermal sensors (pass script)
/etc/librenms/lm-sensors-pass.sh -g .1.3.6.1.4.1.2021.13.16.2.1.3.0

Query SNMP

# From monitoring server
snmpwalk -v2c -c public localhost .1.3.6.1.4.1.8072.1.3.2

# Specific metrics
snmpget -v2c -c public localhost NET-SNMP-EXTEND-MIB::nsExtendOutput1Line.\"clients-wlan0\"
snmpget -v2c -c public localhost NET-SNMP-EXTEND-MIB::nsExtendOutput1Line.\"frequency-wlan0\"

# Thermal sensors (LM-SENSORS-MIB)
snmpwalk -v2c -c public localhost LM-SENSORS-MIB::lmTempSensorsValue

SNMP OID Reference

Wireless Metrics (via nsExtend)

Base OID: .1.3.6.1.4.1.8072.1.3.2

Per interface:

• clients-<iface> - Connected client count
• frequency-<iface> - Operating frequency (MHz)
• rate-tx-<iface>-min/avg/max - TX bitrate stats
• rate-rx-<iface>-min/avg/max - RX bitrate stats
• noise-floor-<iface> - Noise floor (dBm)
• snr-<iface>-min/avg/max - Signal-to-Noise Ratio (dB)

Thermal Sensors (LM-Sensors MIB)

• .1.3.6.1.4.1.2021.13.16.2.1.1 - lmSensorsIndex (INTEGER)
• .1.3.6.1.4.1.2021.13.16.2.1.2 - lmSensorsDevice (STRING)
• .1.3.6.1.4.1.2021.13.16.2.1.3 - lmSensorsValue (Gauge32, millidegrees)

Configuration Examples

Example: 4 Interface Device (like native OpenWrt)

wlInterfaces.txt:

wl0-ap0,IoT
wl0-ap1,guest
wl1-ap0,main
wl1-ap1,uplink

Generated extends:

• clients-wl0-ap0, clients-wl0-ap1, clients-wl1-ap0, clients-wl1-ap1
• frequency-wl0-ap0, frequency-wl0-ap1, frequency-wl1-ap0, frequency-wl1-ap1
• rate-tx-wl0-ap0-min/avg/max (and all other interfaces)
• rate-rx-wl0-ap0-min/avg/max (and all other interfaces)
• And so on...

Example: Multi-VLAN Device (like gl.Inet flint3)

wlInterfaces.txt:

wlan0,MainNetwork
wlan02,VLAN2
wlan12,VLAN12
wlan22,VLAN22

Troubleshooting

wlInterfaces.txt not generated

# Check for wireless interfaces
ls /sys/class/net/*/wireless
ls /sys/class/net/*/phy80211

# Manually create the file
cat > /etc/librenms/wlInterfaces.txt << EOF
wlan0,YourSSID
EOF

SNMP not returning data

# Check if snmpd is running
/etc/init.d/snmpd status

# Check if scripts are executable
ls -la /etc/librenms/*.sh

# Test script directly
/etc/librenms/wlClients.sh wlan0

# Check snmpd logs
logread | grep snmpd

Script errors

# Enable debug output
sh -x /etc/librenms/wlClients.sh wlan0

# Check for required commands
which iw iwinfo awk cut grep

Comparison: Before vs After

Before (Manual, Per-Device)

❌ Required manual creation of wlInterfaces.txt for each device ❌ Different config file for each device type ❌ Repetitive config entries (280+ lines) ❌ Hard to maintain across multiple devices ❌ Interface changes require manual config updates

After (Automated, Unified)

✅ Auto-detects wireless interfaces ✅ Single config generator works for all devices ✅ Generates only needed entries ✅ Easy to maintain and replicate ✅ Interface changes auto-detected on script run

Benefits

1. Zero Manual Configuration: Just run setup script
2. Device-Agnostic: Works on any OpenWrt device
3. Self-Documenting: Auto-generated configs show what's monitored
4. Easy Replication: Same process for all devices
5. Future-Proof: Adding interfaces doesn't require config changes
6. Reduced Errors: No manual typing of repetitive entries
7. Consistent: All devices use same monitoring approach

Security Notes

• Default SNMP community strings should be changed in production
• Restrict SNMP access to monitoring network (192.168.0.0/24 in examples)
• Use SNMPv3 for better security if supported by your NMS

License

These scripts are provided as-is for use with OpenWrt systems.