Class: Net::DNS::Nameserver

Inherits:
Object
  • Object
show all
Defined in:
lib/Net/DNS/Nameserver.rb

Constant Summary collapse

STATE_ACCEPTED = 
1
STATE_GOT_LENGTH = 
2
STATE_SENDING = 
3
DEFAULT_PORT = 
53
DEFAULT_ADDR = 
Socket::INADDR_ANY

Instance Method Summary collapse

Constructor Details

#initialize(opts = {}) ⇒ Nameserver

def initialize(localaddr=DEFAULT_ADDR, localport=DEFAULT_PORT, verbose=false, &replyhandler)



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# File 'lib/Net/DNS/Nameserver.rb', line 33

def initialize(opts={})
  #  LocalAddr		IP address on which to listen.	Defaults to INADDR_ANY.
  #  LocalPort		Port on which to listen.  	Defaults to 53.
  #  ReplyHandler		Reference to reply-handling 
  #			subroutine			Required.
  #  Verbose		Print info about received 
  #			queries.			Defaults to 0 (off).
  opts = {:localaddr => DEFAULT_ADDR, :localport => DEFAULT_PORT, :verbose => false}.merge(opts)
  if (!opts[:replyhandler] || opts[:replyhandler]==nil)
    raise RuntimeError,  "No reply handler!"
  end
  @replyhandler = opts[:replyhandler]
  @verbose = opts[:verbose]
  @sockets = []
  @_tcp = Hash.new
  
  port=opts[:localport]
  
  # make sure we have an array.
  #        localaddr= [DEFAULT_ADDR] unless opts[:localaddr]!=nil
  localaddr= [ opts[:localaddr] ] unless (opts[:localaddr].is_a?(Array))
  
  localaddresses = localaddr
  
  print "Nameserver on #{localaddresses.inspect}:#{port}\n" if @verbose
  
  # while we are here, print incomplete lines as they come along.
  #        local $| = 1 if @verbose
  
  localaddresses.each do |localaddress|
    
    addr = localaddress
    
    # If not, it will do DNS lookups trying to resolve it as a hostname
    # We could also just set it to undef?
    
    #          addr = IPAddr.ntop(addr) unless IPAddr.ipv4?(addr) || IPAddr.ipv6?(addr)
    
    # Pretty IP-addresses, if they are otherwise binary.
    #          addrname = addr
    #          addrname = IPAddr.ntop(addrname) unless addrname =~ /^[\w\.:\-]+$/
    addrname = IPAddr.new(addr, Socket::AF_INET)         
    print "Setting up listening sockets for #{addrname}...\n" if @verbose
    
    print "Creating TCP socket for #{addrname} - " if @verbose
    
    #--------------------------------------------------------------------------
    # Create the TCP socket.
    #--------------------------------------------------------------------------
    
    #            sock_tcp = inet_new(
    #                                    LocalAddr => $addr,
    #                                    LocalPort => $port,
    #                                    Listen	  => 64,
    #                                    Proto	  => "tcp",
    #            Reuse	  => 1,
    #            );
    #          sock_tcp = TCPSocket.new(addr, port)                        
    @tcpserver = TCPServer.new(addr, port)
    if (!@tcpserver)
      raise RuntimError, "Couldn't create TCP socket: #{$!}"
      return
    end
    @tcpserver.listen(64) 
    @sockets.push(@tcpserver)
    print "done.\n" if @verbose
    
    #--------------------------------------------------------------------------
    # Create the UDP Socket.
    #--------------------------------------------------------------------------
    
    print "Creating UDP socket for #{addrname} - " if @verbose
    
    sock_udp = UDPSocket.new()
    sock_udp.bind(addr, port)
    
    if (!sock_udp)
      raise RuntimeError, "Couldn't create UDP socket: #{$!}"
      return
    end
    @sockets.push(sock_udp)
    print "done.\n" if @verbose
  end
  
end

Instance Method Details

#get_open_tcp ⇒ Object 



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# File 'lib/Net/DNS/Nameserver.rb', line 311

def get_open_tcp
  return @_tcp.keys
end

#loop_once(timeout = 0) ⇒ Object

NB this method may be subject to change and is therefore left ‘undocumented’



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# File 'lib/Net/DNS/Nameserver.rb', line 328

def loop_once(timeout=0)
  #        print ";loop_once called with #{timeout} \n" if @verbose
  @_tcp.keys.each do |sock|
    timeout = 0.1 if @_tcp[sock]["outbuffer"]!=""
  end
  #        ready = @select.can_read(timeout)
  ret = IO::select(@sockets, nil, nil, timeout)
  if (ret!=nil) 
    ready = ret[0]
    print "ready : " + ready.inspect + "\n"
    
    ready.each do |sock|
      if (!(sock.is_a?UDPSocket))
        
        self.readfromtcp(sock) &&
        self.tcp_connection(sock)
      else
        self.udp_connection(sock)
        #          else
        #            print "ERROR: connection with unsupported protocol #{proto}\n" if @verbose
      end
    end
  end
  
  now = Time.now()
  # Lets check if any of our TCP clients has pending actions.
  # (outbuffer, timeout)
  #        @_tcp.keys.each do |s|
  @_tcp.keys.each do |s|
    sock = @_tcp[s]["socket"]
    if (@_tcp[s]["outbuffer"].length>0)
      # If we have buffered output, then send as much as the OS will accept
      # and wait with the rest
      len = @_tcp[s]["outbuffer"].length
      #            charssent = sock.syswrite(@_tcp[s]["outbuffer"]
      charssent = sock.write_nonblock(@_tcp[s]["outbuffer"])
      print "Sent #{charssent} of #{len} octets to " + @_tcp[s]["peer"] + ".\n" if @verbose
      #            substr($self->{"_tcp"}{$s}{"outbuffer"}, 0, charssent) = ""
      @_tcp[s]["outbuffer"] [0, charssent] = ""
      if (@_tcp[s]["outbuffer"].length == 0)
        @_tcp[s]["outbuffer"] = ""
        @_tcp[s]["state"] = STATE_ACCEPTED
        if (@_tcp[s]["inbuffer"].length >= 2)
          # See if the client has send us enough data to process the
          # next query.
          # We do this here, because we only want to process (and buffer!!)
          # a single query at a time, per client. If we allowed a STATE_SENDING
          # client to have new requests processed. We could be easilier
          # victims of DoS (client sending lots of queries and never reading
          # from it's socket).
          # Note that this does not disable serialisation on part of the
          # client. The split second it should take for us to lookip the
          # next query, is likely faster than the time it takes to
          # send the response... well, unless it's a lot of tiny queries,
          # in which case we will be generating an entire TCP packet per
          # reply. --robert
          tcp_connection(@_tcp["socket"])
        end
      end
      @_tcp[s]["timeout"] = Time.now()+120
    else
      # Get rid of idle clients.
      timeout = @_tcp[s]["timeout"]
      if (timeout - now < 0)
        print @_tcp[s]["peer"]," has been idle for too long and will be disconnected.\n" if @verbose
        #              @select.remove(sock)
        @sockets.delete(sock)
        sock.close()
        @_tcp.delete(s)
      end
    end
  end
end

#main_loop ⇒ Object

main_loop - Main nameserver loop.



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# File 'lib/Net/DNS/Nameserver.rb', line 406

def main_loop
  while (true) do
    print "Waiting for connections...\n" if @verbose
    # You really need an argument otherwise you'll be burning
    # CPU.
    loop_once(10)
  end
end

#make_reply(query, peerhost) ⇒ Object

make_reply - Make a reply packet.



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# File 'lib/Net/DNS/Nameserver.rb', line 123

def make_reply(query, peerhost)
  reply=""
  headermask=""
  
  if (not query)
    print "ERROR: invalid packet\n" if @verbose
    reply = Net::DNS::Packet.new_from_values("", "ANY", "ANY")
    reply.header.rcode=("FORMERR")
    
    return reply
  end
  
  if (query.header.qr==1)
    print "ERROR: invalid packet (qr was set, dropping)\n" if @verbose
    return
  end
  
  
  qr = (query.question)[0]
  
  qname  = qr ? qr.qname  : ""
  qclass = qr ? qr.qclass : "ANY"
  qtype  = qr ? qr.qtype  : "ANY"
  
  reply = Net::DNS::Packet.new_from_values(qname, qtype, qclass)
  
  if (query.header.opcode == "QUERY")
    if (query.header.qdcount == 1)
      print "query ", query.header.id,
			": (#{qname}, #{qclass}, #{qtype}) - " if @verbose
      
      rcode, ans, auth, add, headermask = @replyhandler.call(qname, qclass, qtype, peerhost, query)
      
      print "#{rcode}\n" if @verbose
      
      reply.header.rcode=(rcode)
      
      reply.push("answer",	   ans)  if ans
      reply.push("authority",  auth) if auth
      reply.push("additional", add)  if add
    else
      print "ERROR: qdcount ", query.header.qdcount, "unsupported\n" if @verbose
      reply.header.rcode=("FORMERR")
    end
  else
    print "ERROR: opcode ", query.header.opcode, " unsupported\n" if @verbose
    reply.header.rcode=("FORMERR")
  end
  
  
  
  if (!headermask)
    reply.header.ra=(1)
    reply.header.ad=(0)
  else
    reply.header.aa=(1) if headermask['aa']
    reply.header.ra=(1) if headermask['ra']
    reply.header.ad=(1) if headermask['ad']
  end
  
  
  reply.header.qr=(1)
  reply.header.cd=(query.header.cd)
  reply.header.rd=(query.header.rd)	
  reply.header.id=(query.header.id)
  
  
  print reply.header.inspect if @verbose && headermask
  
  return reply
end

#readfromtcp(sock) ⇒ Object

readfromtcp - read from a TCP client



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# File 'lib/Net/DNS/Nameserver.rb', line 199

def readfromtcp(sock)
  return -1 unless @_tcp[sock]
  peer = @_tcp[sock]["peer"]
  #        charsread = sock.sysread(@_tcp[sock]["inbuffer"], 16384)
  @_tcp[sock]["inbuffer"] = sock.recv_nonblock(16384)
  charsread = @_tcp[sock]["inbuffer"].length
  @_tcp[sock]["timeout"] = Time.now()+120; # Reset idle timer
  print "Received #{charsread} octets from #{peer}\n" if @verbose
  if (charsread == 0) # 0 octets means socket has closed
    print "Connection to #{peer} closed or lost.\n" if @verbose
    @sockets.delete(sock)
    sock.close()
    @_tcp.delete(sock)
    return charsread
  end
  return charsread
end

#tcp_connection(sock) ⇒ Object

tcp_connection - Handle a TCP connection.



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# File 'lib/Net/DNS/Nameserver.rb', line 221

def tcp_connection(sock)
  #        if (not @_tcp[sock])
  if ((sock == @tcpserver)) # || (not @_tcp[sock]))
    # We go here if we are called with a listener socket.
    client = sock.accept_nonblock
    if (!client)
      print "TCP connection closed by peer before we could accept it.\n" if @verbose
      return 0
    end
    peerport= client.addr[1]
    peerhost = client.addr[3]
    
    print "TCP connection from #{peerhost}:#{peerport}\n" if @verbose
    #          client.blocking=(0)
    @_tcp[client]=Hash.new
    @_tcp[client]["peer"] = "tcp:"+peerhost.inspect+":"+peerport.inspect
    @_tcp[client]["state"] = STATE_ACCEPTED
    @_tcp[client]["socket"] = client
    @_tcp[client]["timeout"] = Time.now()+120
    @_tcp[client]["outbuffer"] = ""
    @sockets.push(client)
    # After we accepted we will look at the socket again 
    # to see if there is any data there. ---Olaf
    loop_once(0)
  elsif @_tcp[sock]
    # We go here if we are called with a client socket
    peer = @_tcp[sock]["peer"]
    
    if (@_tcp[sock]["state"] == STATE_ACCEPTED)
      if (not @_tcp[sock]["inbuffer"].sub!(/^(..)/, ""))
        return; # Still not 2 octets ready
      end
      msglen = $1.unpack("n")[0]
      print "Removed 2 octets from the input buffer from #{peer}.\n" +
		  	"#{peer} said his query contains #{msglen} octets.\n" if @verbose
      @_tcp[sock]["state"] = STATE_GOT_LENGTH
      @_tcp[sock]["querylength"] = msglen
    end
    # Not elsif, because we might already have all the data
    if (@_tcp[sock]["state"] == STATE_GOT_LENGTH)
      # return if not all data has been received yet.
      return if @_tcp[sock]["querylength"] > @_tcp[sock]["inbuffer"].length
      
      qbuf = @_tcp[sock]["inbuffer"][0, @_tcp[sock]["querylength"]]
      #            substr($self->{"_tcp"}{$sock}{"inbuffer"}, 0, $self->{"_tcp"}{$sock}{"querylength"}) = "";
      @_tcp[sock]["inbuffer"][0, @_tcp[sock]["querylength"]]=""
      query = Net::DNS::Packet.new_from_binary(qbuf)
      reply = make_reply(query, sock.addr[3])
      if (!reply) 
        print "I couldn't create a reply for #{peer}. Closing socket.\n" if @verbose
        #              @select.remove(sock)
        @sockets.delete(sock)
        sock.close()
        @_tcp.delete(sock)
        return
      end
      reply_data = reply.data
      len = reply_data.length
      @_tcp[sock]["outbuffer"] = [len].pack("n") + reply_data
      print "Queued #{@_tcp[sock]['outbuffer'].length} octets to #{peer}.\n" if @verbose
      # We are done.
      @_tcp[sock]["state"] = STATE_SENDING
    end
  end
end

#udp_connection(sock) ⇒ Object

udp_connection - Handle a UDP connection.



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# File 'lib/Net/DNS/Nameserver.rb', line 291

def udp_connection(sock)
  buf, sender = sock.recvfrom(Net::DNS::PACKETSZ)
  peerhost = sender[2]
  peerport= sender[1]
  
  print "UDP connection from #{peerhost}:#{peerport}\n" if @verbose
  
  query = Net::DNS::Packet.new_from_binary(buf)
  
  reply = make_reply(query, peerhost) || return
  reply_data = reply.data
  
  #        local $| = 1 if @verbose
  print "Writing response - " if @verbose
  # die() ?!??  I think we need something better. --robert
  sock.send(reply_data, 0, peerhost, peerport) or raise RuntimError, "send: #{$!}"
  print "done\n" if @verbose
end