require "socket"
require "./query"
require "./response"
require "./rr"
require "./settings"
module AsyncDNS
class Resolver
@v6_sock : UDPSocket?
@v4_sock : UDPSocket?
getter settings : Settings
enum Error
NO_NAME_SERVER
end
private class Context
getter query : Query
getter id : UInt16
getter settings : Settings
getter block : Response | Error ->
property ns_index : Int32
property attempt : Int32
property used_ns : Socket::IPAddress | Nil
getter raw_data : Bytes
def initialize(@query : Query, @id : UInt16, @settings : Settings,
@block : Response | Error ->)
@ns_index = 0
@attempt = 0
@used_ns = nil
# Header
io = IO::Memory.new(512)
io.write_bytes(@id, IO::ByteFormat::BigEndian)
# RD
io.write_bytes(0x100_u16, IO::ByteFormat::BigEndian)
# QDCOUNT
io.write_bytes(1_u16, IO::ByteFormat::BigEndian)
# ANCOUNT, NSCOUNT and ARCOUNT
3.times { io.write_bytes(0_u16) }
# Question
# QNAME
@query.domain.split('.').each do |component|
if component.bytesize > 63 || io.size + component.bytesize > 512
raise ArgumentError.new("Domain component too long")
end
io << component
end
# QTYPE
io.write_bytes(@query.rr_type.to_u16, IO::ByteFormat::BigEndian)
# QCLASS
io.write_bytes(@query.dns_class.to_u16, IO::ByteFormat::BigEndian)
@raw_data = io.to_slice
end
end
def initialize
@settings = Settings.new
@queries = Hash(UInt16, Context).new
@tcp_queries = Hash(Socket, Context).new
end
def resolve(query : Query, &block : Response | Error ->) : Nil
id : UInt16
while true
id = Random::Secure.rand(UInt16::MIN..UInt16::MAX)
break unless @queries.has_key?(id)
end
if query.domain.bytesize > 253
raise ArgumentError.new("Queried domain is too long")
end
if @settings.nameservers.empty?
block.call(Error::NO_NAME_SERVER)
return
end
send(Context.new(query.dup, id, settings.dup, block))
end
private def send(context : Context) : Nil
@queries[context.id] = context
ns = context.settings.nameservers[context.ns_index]
context.used_ns = used_ns = Socket::IPAddress.new(ns, 53)
sock : UDPSocket
case used_ns.family
when Socket::Family::INET6
if @v6_sock.nil?
@v6_sock = s = UDPSocket.new
s.bind "::", 0
start_recv_loop(s)
end
sock = @v6_sock.not_nil!
when Socket::Family::INET
if @v4_sock.nil?
@v4_sock = s = UDPSocket.new
s.bind "0.0.0.0", 0
start_recv_loop(s)
end
sock = @v4_sock.not_nil!
else
raise ArgumentError.new("Nameserver must be INET or INET6")
end
sock.send(context.raw_data, used_ns)
end
def start_recv_loop(sock : UDPSocket) : Nil
spawn do
buf = Bytes.new(0x10000)
until sock.closed?
begin
len, addr = sock.receive(buf)
rescue ex : IO::Error
p ex
break if sock.closed? && ex.os_error.nil?
raise ex
end
handle_packet(buf[0, len], addr)
end
end
end
def handle_packet(packet : Bytes, sender : Socket::IPAddress)
p packet
end
def stop : Nil
@v6_sock.try { |s| s.close }
@v4_sock.try { |s| s.close }
end
end
end