service-dhcp-whitelist/scripts/autoconfig.sh

#!/bin/bash
set -e

CONFIG_DIR="./config"
INTERFACE_CONF="${CONFIG_DIR}/interface.conf"
WHITELIST_CONF="${CONFIG_DIR}/whitelist.conf"
NETWORK_CONF="${CONFIG_DIR}/network.conf"

echo "=== DHCP Whitelist Auto-Configuration ==="
echo

# Create config directory if it doesn't exist
mkdir -p "${CONFIG_DIR}"

# Find ethernet interfaces (excluding loopback and virtual interfaces)
echo "Detecting ethernet interfaces..."
INTERFACES=$(ip link show | grep -E "^[0-9]+: en" | awk -F': ' '{print $2}' | head -1)

if [ -z "$INTERFACES" ]; then
    echo "Error: No ethernet interface found"
    echo "Please configure manually by editing ${INTERFACE_CONF}"
    exit 1
fi

echo "Found ethernet interface: $INTERFACES"

# Get the interface with an IP in 192.168.x.x range (common for local networks)
SELECTED_INTERFACE=""
for IFACE in $INTERFACES; do
    IP_INFO=$(ip -4 addr show "$IFACE" 2>/dev/null | grep -oP '(?<=inet\s)\d+(\.\d+){3}' || true)
    if [ -n "$IP_INFO" ]; then
        echo "  Interface $IFACE has IP: $IP_INFO"
        if [[ "$IP_INFO" =~ ^192\.168\. ]] || [[ "$IP_INFO" =~ ^10\. ]] || [[ "$IP_INFO" =~ ^172\. ]]; then
            SELECTED_INTERFACE="$IFACE"
            break
        fi
    fi
done

if [ -z "$SELECTED_INTERFACE" ]; then
    # Fall back to first interface with any IP
    for IFACE in $INTERFACES; do
        if ip -4 addr show "$IFACE" 2>/dev/null | grep -q "inet "; then
            SELECTED_INTERFACE="$IFACE"
            break
        fi
    done
fi

if [ -z "$SELECTED_INTERFACE" ]; then
    echo "Error: No ethernet interface with IP address found"
    echo "Using first available interface: $INTERFACES"
    SELECTED_INTERFACE="$INTERFACES"
fi

echo
echo "Selected interface: $SELECTED_INTERFACE"
echo "$SELECTED_INTERFACE" > "${INTERFACE_CONF}"

# Find MAC addresses of devices on the network
echo
echo "Scanning for devices on the network..."

# Get the network range
NETWORK_INFO=$(ip -4 addr show "$SELECTED_INTERFACE" | grep -oP '(?<=inet\s)\d+(\.\d+){3}/\d+' | head -1)
if [ -z "$NETWORK_INFO" ]; then
    echo "Warning: Could not determine network range for $SELECTED_INTERFACE"
    echo "Creating empty whitelist file. Please add MAC addresses manually."
    touch "${WHITELIST_CONF}"
else
    NETWORK=$(echo "$NETWORK_INFO" | cut -d'/' -f1 | sed 's/\.[0-9]*$/\.0/')
    NETMASK=$(echo "$NETWORK_INFO" | cut -d'/' -f2)
    
    echo "Network: ${NETWORK}/${NETMASK}"
    
    # Try to ping the network to populate ARP table (just a few addresses)
    echo "Discovering devices (this may take a moment)..."
    BASE_NET=$(echo "$NETWORK" | sed 's/\.0$//')
    for i in {1..10}; do
        ping -c 1 -W 1 "${BASE_NET}.${i}" >/dev/null 2>&1 &
    done
    wait
    
    # Get MAC addresses from ARP table
    echo
    echo "Found devices:"
    MACS=$(ip neigh show dev "$SELECTED_INTERFACE" | grep -E "lladdr" | awk '{print $5}' | sort -u)
    
    if [ -z "$MACS" ]; then
        echo "  No devices found in ARP table"
        echo "  Creating empty whitelist. Please add MAC addresses manually."
        touch "${WHITELIST_CONF}"
    else
        echo "$MACS" | while read -r MAC; do
            IP=$(ip neigh show dev "$SELECTED_INTERFACE" | grep "$MAC" | awk '{print $1}')
            echo "  $MAC (IP: $IP)"
        done
        
        echo
        echo "Writing MAC addresses to whitelist..."
        echo "$MACS" > "${WHITELIST_CONF}"
        echo "Added $(echo "$MACS" | wc -l) MAC address(es) to whitelist"
    fi
fi

echo
echo "=== Configuration Summary ==="
echo "Interface: $(cat "${INTERFACE_CONF}")"
echo "Whitelist entries:"
if [ -f "${WHITELIST_CONF}" ] && [ -s "${WHITELIST_CONF}" ]; then
    cat "${WHITELIST_CONF}" | sed 's/^/  /'
else
    echo "  (empty - please add MAC addresses manually)"
fi

echo
# Create or update network.conf with defaults (can be customized)
if [ ! -f "${NETWORK_CONF}" ]; then
    echo
    echo "Creating default network configuration..."
    cat > "${NETWORK_CONF}" << EOF
# Network configuration for DHCP server
# These values override automatic detection

# Network subnet (leave empty for auto-detection from interface)
SUBNET=

# Netmask in dotted notation (leave empty for auto-detection)
NETMASK=

# DHCP range start offset from network base (default: 10)
RANGE_START_OFFSET=10

# DHCP range end offset from network base (default: 100)
RANGE_END_OFFSET=100

# Lease time in seconds (default: 43200 = 12 hours)
LEASE_TIME=43200

# Max lease time in seconds (default: 86400 = 24 hours)
MAX_LEASE_TIME=86400
EOF
    echo "Network configuration created with defaults"
else
    echo "Network configuration already exists, keeping current settings"
fi

echo
echo "Configuration files created:"
echo "  ${INTERFACE_CONF}"
echo "  ${WHITELIST_CONF}"
echo "  ${NETWORK_CONF}"
echo
echo "You can now start the DHCP server with: make up"
echo "Or install as a service with: sudo make install"