#!/bin/sh
# OpenWrt Leases2Hosts 0.01 -- BTA 03.13.2025 -- LostGeek.NET
# Transforms OpenWrt dhcp leases file into format suitable for external DNS server

LEASES_FILE="/tmp/dhcp.leases"
OUTPUT_FILE="/tmp/dhcp.hosts"

# Set domain suffix (leave blank to disable)
DOMAIN_SUFFIX=".lan"

# Ensure the leases file exists
[ -f "$LEASES_FILE" ] || { echo "Leases file not found!"; exit 1; }

# New hosts file header
echo "# Generated by Lease2Hosts" > "$OUTPUT_FILE"

# Process the leases file using BusyBox-compatible awk
awk -v suffix="$DOMAIN_SUFFIX" '
{
    ip = $3;
    hostname = $4;

    # Ignore entries where hostname is "*"
    if (hostname == "*") next;

    # Ensure hostname is not a MAC address (contains colons)
    if (index(hostname, ":") > 0) next;

    # Ensure hostname is only letters, numbers, dots, and dashes
    if (match(hostname, /^[a-zA-Z0-9.-]+$/)) {
        if (suffix != "") {
            print ip, hostname, hostname suffix;
        } else {
            print ip, hostname;
        }
    }
}' "$LEASES_FILE" >> "$OUTPUT_FILE"

echo "Hosts file:"
echo "-----"
cat $OUTPUT_FILE
echo "-----"
echo "Hosts file written: $OUTPUT_FILE"