apu: setup dynamic dns record based on DHCP leases

modules/services/dhcp-dns-sync/dhcp-leases-to-unbound.cr

@@ -0,0 +1,170 @@
+#!/usr/bin/env crystal
+
+require "json"
+require "file_utils"
+require "option_parser"
+
+struct Lease
+  include JSON::Serializable
+
+  @[JSON::Field(key: "Address")]
+  property address : String
+
+  @[JSON::Field(key: "MACAddress")]
+  property mac_address : String?
+
+  @[JSON::Field(key: "Hostname")]
+  property hostname : String?
+
+  @[JSON::Field(key: "Lifetime")]
+  property lifetime : Int64?
+end
+
+struct NetworkStatus
+  include JSON::Serializable
+
+  @[JSON::Field(key: "OfferedDHCPLeases")]
+  property offered_dhcp_leases : Array(Lease)?
+end
+
+def sanitize_hostname(hostname : String) : String?
+  # Lowercase and strip invalid characters
+  sanitized = hostname.downcase.gsub(/[^a-z0-9-]/, "-")
+
+  # Collapse multiple dashes into one
+  sanitized = sanitized.gsub(/-+/, "-")
+
+  # Strip leading/trailing dashes
+  sanitized = sanitized.strip('-')
+
+  # Ensure non-empty and not too long (max 63 chars for DNS label)
+  return nil if sanitized.empty?
+  return nil if sanitized.size > 63
+
+  # Ensure starts with letter or number (not dash)
+  return nil if sanitized.starts_with?('-')
+
+  sanitized
+end
+
+def reverse_ptr(ip : String) : String?
+  parts = ip.split('.')
+  return nil unless parts.size == 4
+
+  "#{parts[3]}.#{parts[2]}.#{parts[1]}.#{parts[0]}.in-addr.arpa."
+end
+
+def generate_unbound_config(leases : Array(Lease), domain : String) : String
+  lines = [] of String
+
+  lines << "# Auto-generated DHCP leases for #{domain}"
+  lines << "# Generated at #{Time.utc}"
+  lines << ""
+
+  leases.each do |lease|
+    next unless hostname = lease.hostname
+    sanitized = sanitize_hostname(hostname)
+    next unless sanitized
+
+    fqdn = "#{sanitized}.#{domain}."
+
+    # A record
+    lines << %{local-data: "#{fqdn} IN A #{lease.address}"}
+
+    # PTR record
+    if ptr = reverse_ptr(lease.address)
+      lines << %{local-data-ptr: "#{ptr} #{fqdn}"}
+    end
+  end
+
+  lines.join("\n") + "\n"
+end
+
+def get_leases(interface : String, networkctl_path : String? = nil) : Array(Lease)
+  cmd = networkctl_path ? "#{networkctl_path} status #{interface} --json=short" : "networkctl status #{interface} --json=short"
+  output = `#{cmd}`
+  raise "networkctl failed (exit code #{$?.exit_status}): #{output}" unless $?.success?
+
+  status = NetworkStatus.from_json(output)
+  status.offered_dhcp_leases || [] of Lease
+end
+
+def write_if_changed(content : String, path : String) : Bool
+  # Check if content is the same
+  if File.exists?(path)
+    current = File.read(path)
+    return false if current == content
+  end
+
+  # Write to temp file and atomically move
+  temp_path = "#{path}.tmp"
+  File.write(temp_path, content)
+  FileUtils.mv(temp_path, path)
+  true
+end
+
+# Configuration
+interface = "koti"
+domain = "home.arpa"
+output_path = "/var/lib/unbound/dhcp-hosts.conf"
+leases_json_path = "/var/lib/router/leases.json"
+networkctl_path : String? = nil
+
+OptionParser.parse do |parser|
+  parser.banner = "Usage: dhcp-leases-to-unbound [options]"
+
+  parser.on("-i INTERFACE", "Network interface to monitor (default: koti)") do |i|
+    interface = i
+  end
+
+  parser.on("-d DOMAIN", "Domain suffix (default: home.arpa)") do |d|
+    domain = d
+  end
+
+  parser.on("-o PATH", "Output path for unbound config (default: /var/lib/unbound/dhcp-hosts.conf)") do |o|
+    output_path = o
+  end
+
+  parser.on("--leases-json PATH", "Output path for leases JSON (default: /var/lib/router/leases.json)") do |path|
+    leases_json_path = path
+  end
+
+  parser.on("--networkctl PATH", "Path to networkctl binary (default: networkctl from PATH)") do |path|
+    networkctl_path = path
+  end
+
+  parser.on("-h", "--help", "Show this help") do
+    puts parser
+    exit
+  end
+end
+
+begin
+  # Get leases from networkd
+  leases = get_leases(interface, networkctl_path)
+
+  # Generate Unbound config
+  config = generate_unbound_config(leases, domain)
+
+  # Write Unbound config if changed
+  changed = write_if_changed(config, output_path)
+
+  # Also write leases JSON for dashboard
+  FileUtils.mkdir_p(File.dirname(leases_json_path))
+  File.write(leases_json_path, leases.to_json)
+
+  # Reload Unbound if config changed
+  if changed
+    puts "DHCP leases updated, reloading Unbound..."
+    result = system("unbound-control reload")
+    unless result
+      # Fallback to systemctl if unbound-control fails
+      system("systemctl reload unbound")
+    end
+  else
+    puts "No DHCP lease changes detected."
+  end
+rescue ex : Exception
+  STDERR.puts "Error: #{ex.message}"
+  exit 1
+end