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require "socket"
require "./query"
require "./response"
require "./rr"
require "./settings"
# TODO: Cancel timer
# TODO: TCP
module AsyncDNS
class Resolver
@v6_sock : UDPSocket?
@v4_sock : UDPSocket?
getter settings : Settings
enum Error
NO_NAME_SERVER
INVALID_REPLY
TRUNCATED
SERVER_INVALID_FORMAT
SERVER_FAILURE
SERVER_NAME_ERROR
SERVER_NOT_IMPLEMENTED
SERVER_REFUSED
UNKNOWN
end
private class Context
getter query : Query
getter id : UInt16
getter settings : Settings
getter block : Response | Error ->
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# 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.write_bytes(component.bytesize.to_u8)
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
id = Random::Secure.rand(UInt16::MIN..UInt16::MAX)
id = Random::Secure.rand(UInt16::MIN..UInt16::MAX).to_u16
break unless @queries.has_key?(id)
end
if query.domain.bytesize > 253
raise ArgumentError.new("Queried domain is too long")
end
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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
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spawn do
buf = Bytes.new(0x10000)
until sock.closed?
begin
len, addr = sock.receive(buf)
rescue ex : IO::Error
p ex
def handle_packet(packet : Bytes, sender : Socket::IPAddress)
p packet
def handle_packet(packet : Bytes, sender : Socket::IPAddress) : Nil
io = IO::Memory.new(packet, writeable: false)
begin
id = packet[0].to_u16 << 8 | packet[1]
begin
context = @queries[id]
rescue KeyError
return
end
return if sender != context.used_ns
@queries.delete(id)
if packet[2] & 0x80 == 0 || # QR
packet[2] & 0x78 != context.raw_data[2] & 0x78 # Opcode
context.block.call(Error::INVALID_REPLY)
return
end
if packet[2] & 0x02 != 0 # TC
# TODO: Switch to TCP
context.block.call(Error::TRUNCATED)
return
end
case packet[3] & 0x0F # RCODE
when 0
error = nil
try_next_ns = false
when 1
error = Error::SERVER_INVALID_FORMAT
try_next_ns = false
when 2
error = Error::SERVER_FAILURE
try_next_ns = true
when 3
error = Error::SERVER_NAME_ERROR
try_next_ns = false
when 4
error = Error::SERVER_NOT_IMPLEMENTED
try_next_ns = true
when 5
error = Error::SERVER_REFUSED
try_next_ns = true
else
error = Error::UNKNOWN
try_next_ns = true
end
if try_next_ns
if context.ns_index + 1 < context.settings.nameservers.size
context.ns_index += 1
send(context)
return
end
end
if error
context.block.call(error)
return
end
io = IO::Memory.new(packet[4, packet.size - 4], writeable: false)
qdcount = io.read_bytes(UInt16, IO::ByteFormat::BigEndian)
adcount = io.read_bytes(UInt16, IO::ByteFormat::BigEndian)
nscount = io.read_bytes(UInt16, IO::ByteFormat::BigEndian)
arcount = io.read_bytes(UInt16, IO::ByteFormat::BigEndian)
rescue IndexError
end
end
def stop : Nil
@v6_sock.try { |s| s.close }
@v4_sock.try { |s| s.close }
end
end
end
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