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2026-05-25 03:31:08 +02:00
parent dbd6bf0324
commit a1a17e81a1
332 changed files with 174509 additions and 1106 deletions
@@ -0,0 +1,668 @@
+#!/bin/bash
+################################################################################
+# Script Name: dhcp-lease-exporter.sh
+# Version: 1.01
+# Description: Prometheus exporter for DHCP lease metrics — pool utilization,
+#              active leases per subnet, lease expirations, reservation status,
+#              DORA packet counts, and lease duration tracking for ISC DHCP
+#              (dhcpd) and ISC Kea.
+#
+# Author:  Phil Connor
+# Contact: contact@mylinux.work
+# Website: https://mylinux.work
+# License: MIT
+#
+# Usage:
+#   # Output to stdout
+#   sudo ./dhcp-lease-exporter.sh
+#
+#   # Textfile collector mode
+#   sudo ./dhcp-lease-exporter.sh --textfile
+#
+#   # HTTP server mode
+#   sudo ./dhcp-lease-exporter.sh --http
+#
+#   # Custom port
+#   sudo ./dhcp-lease-exporter.sh --http --port 9533
+#
+################################################################################
+
+set -euo pipefail
+
+# ============================================================================
+# CONFIGURATION
+# ============================================================================
+
+readonly VERSION="1.0"
+readonly SCRIPT_NAME="${0##*/}"
+
+# DHCP backend — auto, dhcpd, or kea
+DHCP_BACKEND="auto"
+
+# dhcpd paths
+DHCPD_LEASES="/var/lib/dhcp/dhcpd.leases"
+DHCPD_CONF="/etc/dhcp/dhcpd.conf"
+
+# Kea paths and API
+KEA_LEASES="/var/lib/kea/kea-leases4.csv"
+KEA_API="http://127.0.0.1:8000"
+KEA_USE_API="true"
+
+# Output settings
+TEXTFILE_DIR="/var/lib/node_exporter/textfile_collector"
+HTTP_PORT=9533
+LOCK_FILE="/tmp/dhcp-lease-exporter.lock"
+
+# Runtime
+MODE="stdout"
+ONCE=false
+DETECTED_BACKEND=""
+
+# ============================================================================
+# COLORS
+# ============================================================================
+
+RED='\033[0;31m'
+GREEN='\033[0;32m'
+YELLOW='\033[0;33m'
+NC='\033[0m'
+
+# ============================================================================
+# HELPER FUNCTIONS
+# ============================================================================
+
+log_info()  { echo -e "${GREEN}[INFO]${NC} $*" >&2; }
+log_warn()  { echo -e "${YELLOW}[WARN]${NC} $*" >&2; }
+log_error() { echo -e "${RED}[ERROR]${NC} $*" >&2; }
+
+show_usage() {
+    cat <<EOF
+Usage: sudo $SCRIPT_NAME [OPTIONS]
+
+Export DHCP lease metrics as Prometheus-compatible text format.
+
+MODES:
+    --textfile      Write to node_exporter textfile collector
+    --http          Run as standalone HTTP server
+    (default)       Print to stdout
+
+OPTIONS:
+    --port PORT         HTTP port (default: $HTTP_PORT)
+    --backend TYPE      Force backend: dhcpd or kea (default: auto)
+    --once              In HTTP mode, serve one request and exit
+    -h, --help          Show this help message
+
+CONFIGURATION:
+    Edit the variables at the top of this script to set paths, ports, etc.
+
+EOF
+    exit 0
+}
+
+parse_args() {
+    while [[ $# -gt 0 ]]; do
+        case "$1" in
+            --textfile)   MODE="textfile"; shift ;;
+            --http)       MODE="http"; shift ;;
+            --port)       HTTP_PORT="$2"; shift 2 ;;
+            --backend)    DHCP_BACKEND="$2"; shift 2 ;;
+            --once)       ONCE=true; shift ;;
+            -h|--help)    show_usage ;;
+            *)            log_error "Unknown option: $1"; show_usage ;;
+        esac
+    done
+}
+
+write_metric_header() {
+    local name="$1" type="$2" help="$3"
+    echo "# HELP ${name} ${help}"
+    echo "# TYPE ${name} ${type}"
+}
+
+acquire_lock() {
+    if [ -f "$LOCK_FILE" ]; then
+        local pid
+        pid=$(cat "$LOCK_FILE" 2>/dev/null || true)
+        if [ -n "$pid" ] && kill -0 "$pid" 2>/dev/null; then
+            log_error "Another instance is running (PID $pid)"
+            exit 1
+        fi
+        rm -f "$LOCK_FILE"
+    fi
+    echo $$ > "$LOCK_FILE"
+    trap 'rm -f "$LOCK_FILE"' EXIT
+}
+
+# ============================================================================
+# BACKEND DETECTION
+# ============================================================================
+
+detect_backend() {
+    if [ "$DHCP_BACKEND" != "auto" ]; then
+        DETECTED_BACKEND="$DHCP_BACKEND"
+        return
+    fi
+
+    if systemctl is-active --quiet isc-kea-dhcp4-server 2>/dev/null || \
+       systemctl is-active --quiet kea-dhcp4 2>/dev/null; then
+        DETECTED_BACKEND="kea"
+    elif systemctl is-active --quiet isc-dhcp-server 2>/dev/null || \
+         systemctl is-active --quiet dhcpd 2>/dev/null; then
+        DETECTED_BACKEND="dhcpd"
+    elif [ -f "$KEA_LEASES" ]; then
+        DETECTED_BACKEND="kea"
+    elif [ -f "$DHCPD_LEASES" ]; then
+        DETECTED_BACKEND="dhcpd"
+    else
+        DETECTED_BACKEND="unknown"
+    fi
+}
+
+# ============================================================================
+# DHCPD FUNCTIONS
+# ============================================================================
+
+# Parse dhcpd.conf for subnet definitions and pool ranges
+parse_dhcpd_subnets() {
+    local conf="$DHCPD_CONF"
+    [ -f "$conf" ] || return
+
+    local current_subnet="" current_name="" range_start="" range_end=""
+    local in_subnet=false
+
+    while IFS= read -r line; do
+        # Match subnet declaration
+        if [[ "$line" =~ ^[[:space:]]*subnet[[:space:]]+([0-9.]+)[[:space:]]+netmask[[:space:]]+([0-9.]+) ]]; then
+            current_subnet="${BASH_REMATCH[1]}"
+            local netmask="${BASH_REMATCH[2]}"
+            current_name="$current_subnet"
+            in_subnet=true
+            range_start=""
+            range_end=""
+            # Calculate CIDR from netmask
+            local cidr
+            cidr=$(netmask_to_cidr "$netmask")
+            current_subnet="${current_subnet}/${cidr}"
+        fi
+
+        # Check for comment-based name
+        if $in_subnet && [[ "$line" =~ ^[[:space:]]*#[[:space:]]*(.+) ]]; then
+            if [ "$current_name" = "${current_subnet%%/*}" ]; then
+                current_name="${BASH_REMATCH[1]}"
+            fi
+        fi
+
+        # Match range declaration
+        if $in_subnet && [[ "$line" =~ ^[[:space:]]*range[[:space:]]+([0-9.]+)[[:space:]]+([0-9.]+) ]]; then
+            range_start="${BASH_REMATCH[1]}"
+            range_end="${BASH_REMATCH[2]}"
+        fi
+
+        # End of subnet block
+        if $in_subnet && [[ "$line" =~ ^[[:space:]]*\} ]]; then
+            if [ -n "$range_start" ] && [ -n "$range_end" ]; then
+                local total
+                total=$(ip_range_count "$range_start" "$range_end")
+                echo "${current_subnet}|${current_name}|${total}|${range_start}|${range_end}"
+            fi
+            in_subnet=false
+        fi
+    done < "$conf"
+}
+
+netmask_to_cidr() {
+    local netmask="$1"
+    local cidr=0
+    for octet in $(echo "$netmask" | tr '.' ' '); do
+        case $octet in
+            255) cidr=$((cidr + 8)) ;;
+            254) cidr=$((cidr + 7)) ;;
+            252) cidr=$((cidr + 6)) ;;
+            248) cidr=$((cidr + 5)) ;;
+            240) cidr=$((cidr + 4)) ;;
+            224) cidr=$((cidr + 3)) ;;
+            192) cidr=$((cidr + 2)) ;;
+            128) cidr=$((cidr + 1)) ;;
+            0)   ;;
+        esac
+    done
+    echo "$cidr"
+}
+
+ip_to_int() {
+    local a b c d
+    IFS='.' read -r a b c d <<< "$1"
+    echo $(( (a << 24) + (b << 16) + (c << 8) + d ))
+}
+
+ip_range_count() {
+    local start_int end_int
+    start_int=$(ip_to_int "$1")
+    end_int=$(ip_to_int "$2")
+    echo $(( end_int - start_int + 1 ))
+}
+
+# Count active leases per subnet from dhcpd.leases
+count_dhcpd_leases() {
+    local lease_file="$DHCPD_LEASES"
+    [ -f "$lease_file" ] || return
+
+    local now
+    now=$(date +%s)
+
+    awk -v now="$now" '
+    /^lease / { ip = $2 }
+    /ends / {
+        gsub(/[;\/:]/, " ", $0)
+        if ($2 != "never") {
+            t = mktime($3 " " $4 " " $5 " " $6 " " $7 " " $8)
+            if (t > now) active[ip] = t - now
+        }
+    }
+    /binding state active/ { state[ip] = "active" }
+    END {
+        for (ip in active) {
+            if (state[ip] == "active") {
+                print ip, active[ip]
+            }
+        }
+    }' "$lease_file"
+}
+
+# Count reservations from dhcpd.conf
+count_dhcpd_reservations() {
+    local conf="$DHCPD_CONF"
+    [ -f "$conf" ] || return
+    grep -c "fixed-address" "$conf" 2>/dev/null || true
+}
+
+# Parse DORA stats from syslog
+parse_dhcpd_dora() {
+    local logfile="/var/log/syslog"
+    [ -f "$logfile" ] || logfile="/var/log/messages"
+    [ -f "$logfile" ] || return
+
+    local discovers offers requests acks naks declines releases
+    discovers=$(grep -c "DHCPDISCOVER" "$logfile" 2>/dev/null || true)
+    offers=$(grep -c "DHCPOFFER" "$logfile" 2>/dev/null || true)
+    requests=$(grep -c "DHCPREQUEST" "$logfile" 2>/dev/null || true)
+    acks=$(grep -c "DHCPACK" "$logfile" 2>/dev/null || true)
+    naks=$(grep -c "DHCPNAK" "$logfile" 2>/dev/null || true)
+    declines=$(grep -c "DHCPDECLINE" "$logfile" 2>/dev/null || true)
+    releases=$(grep -c "DHCPRELEASE" "$logfile" 2>/dev/null || true)
+
+    echo "${discovers}|${offers}|${requests}|${acks}|${naks}|${declines}|${releases}"
+}
+
+# ============================================================================
+# KEA FUNCTIONS
+# ============================================================================
+
+kea_api_call() {
+    local command="$1"
+    curl -s --max-time 5 -X POST "${KEA_API}" \
+        -H "Content-Type: application/json" \
+        -d "{\"command\": \"${command}\", \"service\": [\"dhcp4\"]}" 2>/dev/null
+}
+
+parse_kea_leases_file() {
+    local lease_file="$KEA_LEASES"
+    [ -f "$lease_file" ] || return
+
+    local now
+    now=$(date +%s)
+
+    awk -F',' -v now="$now" '
+    NR > 1 && NF >= 9 {
+        ip = $1
+        expire = $7
+        state = $9
+        if (state == 0 && expire > now) {
+            remaining = expire - now
+            print ip, remaining
+        }
+    }' "$lease_file"
+}
+
+parse_kea_api_subnets() {
+    local response
+    response=$(kea_api_call "subnet4-list")
+    if [ -z "$response" ]; then
+        return 1
+    fi
+
+    echo "$response" | python3 -c "
+import sys, json
+data = json.load(sys.stdin)
+if data[0]['result'] == 0:
+    for s in data[0].get('arguments', {}).get('subnets', []):
+        sid = s.get('id', 0)
+        subnet = s.get('subnet', '')
+        print(f'{sid}|{subnet}')
+" 2>/dev/null
+}
+
+parse_kea_api_stats() {
+    local response
+    response=$(kea_api_call "statistic-get-all")
+    if [ -z "$response" ]; then
+        return 1
+    fi
+    echo "$response"
+}
+
+# ============================================================================
+# METRIC COLLECTION
+# ============================================================================
+
+collect_metrics() {
+    local start_time
+    start_time=$(date +%s%N)
+    local metrics=""
+
+    # Exporter status
+    metrics+="$(write_metric_header "dhcp_up" "gauge" "Exporter status (1=up, 0=down)")"$'\n'
+    metrics+="$(write_metric_header "dhcp_exporter_info" "gauge" "Exporter version and backend")"$'\n'
+
+    if [ "$DETECTED_BACKEND" = "unknown" ]; then
+        metrics+="dhcp_up 0"$'\n'
+        echo "$metrics"
+        return
+    fi
+
+    metrics+="dhcp_up 1"$'\n'
+    metrics+="dhcp_exporter_info{version=\"${VERSION}\",backend=\"${DETECTED_BACKEND}\"} 1"$'\n'
+
+    local subnet_count=0
+    local total_active=0
+
+    if [ "$DETECTED_BACKEND" = "dhcpd" ]; then
+        collect_dhcpd_metrics
+    elif [ "$DETECTED_BACKEND" = "kea" ]; then
+        collect_kea_metrics
+    fi
+
+    # Subnet count
+    metrics+="$(write_metric_header "dhcp_subnets_total" "gauge" "Total number of configured subnets")"$'\n'
+    metrics+="dhcp_subnets_total ${subnet_count}"$'\n'
+
+    # Total active leases
+    metrics+="$(write_metric_header "dhcp_leases_active_total" "gauge" "Total active leases across all subnets")"$'\n'
+    metrics+="dhcp_leases_active_total ${total_active}"$'\n'
+
+    # Lease file info
+    if [ "$DETECTED_BACKEND" = "dhcpd" ] && [ -f "$DHCPD_LEASES" ]; then
+        local file_age file_size
+        file_age=$(( $(date +%s) - $(stat -c %Y "$DHCPD_LEASES") ))
+        file_size=$(stat -c %s "$DHCPD_LEASES")
+        metrics+="$(write_metric_header "dhcp_lease_file_age_seconds" "gauge" "Seconds since the lease file was last modified")"$'\n'
+        metrics+="dhcp_lease_file_age_seconds ${file_age}"$'\n'
+        metrics+="$(write_metric_header "dhcp_lease_file_size_bytes" "gauge" "Size of the lease file")"$'\n'
+        metrics+="dhcp_lease_file_size_bytes ${file_size}"$'\n'
+    elif [ "$DETECTED_BACKEND" = "kea" ] && [ -f "$KEA_LEASES" ]; then
+        local file_age file_size
+        file_age=$(( $(date +%s) - $(stat -c %Y "$KEA_LEASES") ))
+        file_size=$(stat -c %s "$KEA_LEASES")
+        metrics+="$(write_metric_header "dhcp_lease_file_age_seconds" "gauge" "Seconds since the lease file was last modified")"$'\n'
+        metrics+="dhcp_lease_file_age_seconds ${file_age}"$'\n'
+        metrics+="$(write_metric_header "dhcp_lease_file_size_bytes" "gauge" "Size of the lease file")"$'\n'
+        metrics+="dhcp_lease_file_size_bytes ${file_size}"$'\n'
+    fi
+
+    # Execution time
+    local end_time duration
+    end_time=$(date +%s%N)
+    duration=$(echo "scale=2; ($end_time - $start_time) / 1000000000" | bc 2>/dev/null || echo "0")
+    metrics+="$(write_metric_header "dhcp_exporter_duration_seconds" "gauge" "Script execution time")"$'\n'
+    metrics+="dhcp_exporter_duration_seconds ${duration}"$'\n'
+    metrics+="$(write_metric_header "dhcp_exporter_last_run_timestamp" "gauge" "Unix timestamp of last successful run")"$'\n'
+    metrics+="dhcp_exporter_last_run_timestamp $(date +%s)"$'\n'
+
+    echo "$metrics"
+}
+
+collect_dhcpd_metrics() {
+    # Parse subnets from config
+    local subnet_data
+    subnet_data=$(parse_dhcpd_subnets)
+
+    # Get active leases
+    local lease_data
+    lease_data=$(count_dhcpd_leases)
+
+    metrics+="$(write_metric_header "dhcp_subnet_pool_total" "gauge" "Total addresses in the pool")"$'\n'
+    metrics+="$(write_metric_header "dhcp_subnet_pool_active" "gauge" "Currently leased addresses")"$'\n'
+    metrics+="$(write_metric_header "dhcp_subnet_pool_free" "gauge" "Available addresses in the pool")"$'\n'
+    metrics+="$(write_metric_header "dhcp_subnet_pool_utilization" "gauge" "Pool utilization percentage (0-100)")"$'\n'
+    metrics+="$(write_metric_header "dhcp_subnet_pool_reserved" "gauge" "Number of static reservations")"$'\n'
+    metrics+="$(write_metric_header "dhcp_subnet_leases_expiring" "gauge" "Leases expiring within threshold")"$'\n'
+    metrics+="$(write_metric_header "dhcp_subnet_lease_longest_seconds" "gauge" "Remaining time on the longest lease")"$'\n'
+    metrics+="$(write_metric_header "dhcp_subnet_lease_shortest_seconds" "gauge" "Remaining time on the shortest lease")"$'\n'
+
+    while IFS='|' read -r subnet name pool_total range_start range_end; do
+        [ -z "$subnet" ] && continue
+        subnet_count=$((subnet_count + 1))
+
+        # Count active leases in this subnet range
+        local active=0 longest=0 shortest=999999999
+        local expiring_1h=0 expiring_4h=0 expiring_24h=0
+        local start_int end_int
+        start_int=$(ip_to_int "$range_start")
+        end_int=$(ip_to_int "$range_end")
+
+        while read -r lease_ip remaining; do
+            [ -z "$lease_ip" ] && continue
+            local lip
+            lip=$(ip_to_int "$lease_ip")
+            if [ "$lip" -ge "$start_int" ] && [ "$lip" -le "$end_int" ]; then
+                active=$((active + 1))
+                total_active=$((total_active + 1))
+                [ "$remaining" -gt "$longest" ] && longest=$remaining
+                [ "$remaining" -lt "$shortest" ] && shortest=$remaining
+                [ "$remaining" -le 3600 ] && expiring_1h=$((expiring_1h + 1))
+                [ "$remaining" -le 14400 ] && expiring_4h=$((expiring_4h + 1))
+                [ "$remaining" -le 86400 ] && expiring_24h=$((expiring_24h + 1))
+            fi
+        done <<< "$lease_data"
+
+        local free=$((pool_total - active))
+        [ $free -lt 0 ] && free=0
+        local util=0
+        if [ "$pool_total" -gt 0 ]; then
+            util=$(echo "scale=2; $active * 100 / $pool_total" | bc 2>/dev/null || echo "0")
+        fi
+        [ $active -eq 0 ] && shortest=0
+
+        local reserved
+        reserved=$(count_dhcpd_reservations)
+
+        metrics+="dhcp_subnet_pool_total{subnet=\"${subnet}\",name=\"${name}\"} ${pool_total}"$'\n'
+        metrics+="dhcp_subnet_pool_active{subnet=\"${subnet}\",name=\"${name}\"} ${active}"$'\n'
+        metrics+="dhcp_subnet_pool_free{subnet=\"${subnet}\",name=\"${name}\"} ${free}"$'\n'
+        metrics+="dhcp_subnet_pool_utilization{subnet=\"${subnet}\",name=\"${name}\"} ${util}"$'\n'
+        metrics+="dhcp_subnet_pool_reserved{subnet=\"${subnet}\",name=\"${name}\"} ${reserved}"$'\n'
+        metrics+="dhcp_subnet_leases_expiring{subnet=\"${subnet}\",name=\"${name}\",within=\"1h\"} ${expiring_1h}"$'\n'
+        metrics+="dhcp_subnet_leases_expiring{subnet=\"${subnet}\",name=\"${name}\",within=\"4h\"} ${expiring_4h}"$'\n'
+        metrics+="dhcp_subnet_leases_expiring{subnet=\"${subnet}\",name=\"${name}\",within=\"24h\"} ${expiring_24h}"$'\n'
+        metrics+="dhcp_subnet_lease_longest_seconds{subnet=\"${subnet}\",name=\"${name}\"} ${longest}"$'\n'
+        metrics+="dhcp_subnet_lease_shortest_seconds{subnet=\"${subnet}\",name=\"${name}\"} ${shortest}"$'\n'
+    done <<< "$subnet_data"
+
+    # DORA stats
+    local dora
+    dora=$(parse_dhcpd_dora)
+    if [ -n "$dora" ]; then
+        IFS='|' read -r discovers offers requests acks naks declines releases <<< "$dora"
+        metrics+="$(write_metric_header "dhcp_discovers_total" "counter" "Total DHCPDISCOVER packets received")"$'\n'
+        metrics+="dhcp_discovers_total ${discovers}"$'\n'
+        metrics+="$(write_metric_header "dhcp_offers_total" "counter" "Total DHCPOFFER packets sent")"$'\n'
+        metrics+="dhcp_offers_total ${offers}"$'\n'
+        metrics+="$(write_metric_header "dhcp_requests_total" "counter" "Total DHCPREQUEST packets received")"$'\n'
+        metrics+="dhcp_requests_total ${requests}"$'\n'
+        metrics+="$(write_metric_header "dhcp_acks_total" "counter" "Total DHCPACK packets sent")"$'\n'
+        metrics+="dhcp_acks_total ${acks}"$'\n'
+        metrics+="$(write_metric_header "dhcp_naks_total" "counter" "Total DHCPNAK packets sent")"$'\n'
+        metrics+="dhcp_naks_total ${naks}"$'\n'
+        metrics+="$(write_metric_header "dhcp_declines_total" "counter" "Total DHCPDECLINE packets received")"$'\n'
+        metrics+="dhcp_declines_total ${declines}"$'\n'
+        metrics+="$(write_metric_header "dhcp_releases_total" "counter" "Total DHCPRELEASE packets received")"$'\n'
+        metrics+="dhcp_releases_total ${releases}"$'\n'
+    fi
+}
+
+collect_kea_metrics() {
+    metrics+="$(write_metric_header "dhcp_subnet_pool_total" "gauge" "Total addresses in the pool")"$'\n'
+    metrics+="$(write_metric_header "dhcp_subnet_pool_active" "gauge" "Currently leased addresses")"$'\n'
+    metrics+="$(write_metric_header "dhcp_subnet_pool_free" "gauge" "Available addresses in the pool")"$'\n'
+    metrics+="$(write_metric_header "dhcp_subnet_pool_utilization" "gauge" "Pool utilization percentage (0-100)")"$'\n'
+    metrics+="$(write_metric_header "dhcp_subnet_pool_reserved" "gauge" "Number of static reservations")"$'\n'
+    metrics+="$(write_metric_header "dhcp_subnet_leases_expiring" "gauge" "Leases expiring within threshold")"$'\n'
+    metrics+="$(write_metric_header "dhcp_subnet_lease_longest_seconds" "gauge" "Remaining time on the longest lease")"$'\n'
+    metrics+="$(write_metric_header "dhcp_subnet_lease_shortest_seconds" "gauge" "Remaining time on the shortest lease")"$'\n'
+
+    if [ "$KEA_USE_API" = "true" ]; then
+        collect_kea_api_metrics
+    else
+        collect_kea_file_metrics
+    fi
+}
+
+collect_kea_api_metrics() {
+    local stats_json
+    stats_json=$(kea_api_call "statistic-get-all")
+
+    if [ -z "$stats_json" ]; then
+        log_warn "Kea API not responding, falling back to file mode"
+        collect_kea_file_metrics
+        return
+    fi
+
+    # Parse stats via python3
+    echo "$stats_json" | python3 -c "
+import sys, json
+data = json.load(sys.stdin)
+if data[0]['result'] == 0:
+    args = data[0].get('arguments', {})
+    for key, val in args.items():
+        if val and isinstance(val, list):
+            v = val[0][0] if isinstance(val[0], list) else val[0]
+            print(f'{key}={v}')
+" 2>/dev/null | while IFS='=' read -r key value; do
+        case "$key" in
+            subnet*total-addresses*)
+                local sid="${key#subnet[}"
+                sid="${sid%%]*}"
+                metrics+="dhcp_subnet_pool_total{subnet=\"${sid}\"} ${value}"$'\n'
+                ;;
+            subnet*assigned-addresses*)
+                local sid="${key#subnet[}"
+                sid="${sid%%]*}"
+                metrics+="dhcp_subnet_pool_active{subnet=\"${sid}\"} ${value}"$'\n'
+                ;;
+            pkt4-discover-received)
+                metrics+="$(write_metric_header "dhcp_discovers_total" "counter" "Total DHCPDISCOVER packets received")"$'\n'
+                metrics+="dhcp_discovers_total ${value}"$'\n'
+                ;;
+            pkt4-offer-sent)
+                metrics+="$(write_metric_header "dhcp_offers_total" "counter" "Total DHCPOFFER packets sent")"$'\n'
+                metrics+="dhcp_offers_total ${value}"$'\n'
+                ;;
+            pkt4-request-received)
+                metrics+="$(write_metric_header "dhcp_requests_total" "counter" "Total DHCPREQUEST packets received")"$'\n'
+                metrics+="dhcp_requests_total ${value}"$'\n'
+                ;;
+            pkt4-ack-sent)
+                metrics+="$(write_metric_header "dhcp_acks_total" "counter" "Total DHCPACK packets sent")"$'\n'
+                metrics+="dhcp_acks_total ${value}"$'\n'
+                ;;
+            pkt4-nak-sent)
+                metrics+="$(write_metric_header "dhcp_naks_total" "counter" "Total DHCPNAK packets sent")"$'\n'
+                metrics+="dhcp_naks_total ${value}"$'\n'
+                ;;
+            pkt4-decline-received)
+                metrics+="$(write_metric_header "dhcp_declines_total" "counter" "Total DHCPDECLINE packets received")"$'\n'
+                metrics+="dhcp_declines_total ${value}"$'\n'
+                ;;
+            pkt4-release-received)
+                metrics+="$(write_metric_header "dhcp_releases_total" "counter" "Total DHCPRELEASE packets received")"$'\n'
+                metrics+="dhcp_releases_total ${value}"$'\n'
+                ;;
+        esac
+    done
+}
+
+collect_kea_file_metrics() {
+    local lease_data
+    lease_data=$(parse_kea_leases_file)
+    local now
+    now=$(date +%s)
+
+    # Simple lease counting from CSV
+    while read -r lease_ip remaining; do
+        [ -z "$lease_ip" ] && continue
+        total_active=$((total_active + 1))
+    done <<< "$lease_data"
+}
+
+# ============================================================================
+# OUTPUT
+# ============================================================================
+
+output_metrics() {
+    local all_metrics
+    all_metrics=$(collect_metrics)
+
+    case "$MODE" in
+        stdout)
+            echo "$all_metrics"
+            ;;
+        textfile)
+            mkdir -p "$TEXTFILE_DIR"
+            local tmp_file
+            tmp_file=$(mktemp "${TEXTFILE_DIR}/.dhcp-metrics.XXXXXX")
+            echo "$all_metrics" > "$tmp_file"
+            mv "$tmp_file" "${TEXTFILE_DIR}/dhcp-metrics.prom"
+            log_info "Wrote metrics to ${TEXTFILE_DIR}/dhcp-metrics.prom"
+            ;;
+        http)
+            run_http_server "$all_metrics"
+            ;;
+    esac
+}
+
+run_http_server() {
+    log_info "Starting HTTP server on port ${HTTP_PORT}"
+    while true; do
+        local all_metrics
+        all_metrics=$(collect_metrics)
+
+        {
+            echo -e "HTTP/1.1 200 OK\r"
+            echo -e "Content-Type: text/plain; version=0.0.4; charset=utf-8\r"
+            echo -e "Content-Length: ${#all_metrics}\r"
+            echo -e "\r"
+            echo "$all_metrics"
+        } | nc -l -p "$HTTP_PORT" -q 1 2>/dev/null || \
+        {
+            echo -e "HTTP/1.1 200 OK\r\nContent-Type: text/plain\r\n\r\n${all_metrics}"
+        } | nc -l "$HTTP_PORT" 2>/dev/null
+
+        if $ONCE; then
+            break
+        fi
+    done
+}
+
+# ============================================================================
+# MAIN
+# ============================================================================
+
+main() {
+    parse_args "$@"
+    acquire_lock
+    detect_backend
+    log_info "Detected DHCP backend: ${DETECTED_BACKEND}"
+    output_metrics
+}
+
+main "$@"