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IPv6 Enable DNS Server

Rosenfeld Asaf & Timor Lior

Advisor: Uritzky Max

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Some Background

• The Project deals with several major protocols

• DNS Servers play a very important role in the Internet

• New IP Protocol is quicky spreading worldwide

• Internet servers must be stable and usable

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Domain Name Service

• Use names instead of numbers

• Servers are suffixes divided

• Servers arranged in tree like hierarchy

• Ever notice the dot ???

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DNS (cont.)

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DNS Server

ROOT Server

.il. Server

.ac.il. Server

DNS Server Database

CLIENT

1. www.te

chnion.ac.il ?2. www.technion.ac.il ?

3. .il. Server

4. www.te

chnion.ac.il ?5. .ac.il.

Server6. w

ww

.tech

nion

.ac.

il ?

7. 1

32.6

8.1.

1

8. 132.68.1.1

9. store 132.68.1.1

for www.te

chnion.ac.il

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Internet Protocol V6• IPv4 supports poorly distirbuted

and not enough addresses. (4G)

• Modular Packet structure

• New features

• Different handling

• No backward compatibility

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Project Goals

• Learn the DNS protocol

• Learn the IPv6 protocol

• Learn C# with MS .NET

• Implement a deployable DNS Server for IPv4 and IPv6 addresses, accoding to Industry standatds and RFCs

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Challanges• Server needs to have dual stack. Support

for both platform and service

• Usable – handle large amount of requsets in short time. Parse, Find, Build and Send while Avoiding timeouts.

• Stable – withstand bursts and DoS attacks

• Testing (DoS, multiple environments, test app.)

• Native and Joined IP environments

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Solution Concept

• Multiple Network-interface threads

• Single synchronized joined Database

• Database capable of learning

• Run-time protocol chooser

• Use .Net Socket, Threading and collections mechanisms

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Class Diagram

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+Record_type()+Record_class()+Record_ttl()+Record_rdata()

-RR_type : object = { A, AAAA, CNAME, HINFO, MX, NS, SOA }-RR_class : object = { IN, CH }-RR_ttl : int-RR_rdata : string

ResourceRecord

+node_get_rr_array()()+add_resource_record()()+Node_owner()

-node_owner : string-node_rr_array : object-MAX_RR_AMOUNT : int

Node

1 -Domain Name0..*

11..*

«uses»

«uses»

«uses»

+Query()()+produceResponse() : object

-SourceAddress-SourceAddressFamily-QueryID-OpCode-AA-TC-RD-RA-UserEndPoint-Node_name-Record_type-Record_class

Query

+startSocket()+endSocket()+startSocketV6()+endSocketV6()+listenerStartReceive()+listenerOnReceive()

-ipv4_socket_enabled-ipv6_socket_enabled-shared_ipv4_socket-shared_ipv6_socket-DNSDB

DNSListener

+add_node() : void+remove_node()+add_rr()+get_node() : object+get_ext_node() : object+load_db()-reader_start()-reader_finish()-writer_start()-writer_finish()

-readers_count : int-write_lock : object-db_nodes_array[] : object

NodesDB

DNSMain

*

-DNSDB

1

1

*

GUI

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DatabaseDemands:• Support multiple read and write

transactions• Fast !

#Domain NameDomain Address

1www.a.com132.68.1.1

2www.a.com132.69.1.2

3www.bb.com192.168.1.1

4www.a.com132.68.1.3

5www.bb.com192.168.1.2

6www.a.com132.68.1.4

7www.bb.com192.168.1.3

8www.bb.com192.168.1.4

9www.a.com132.68.1.5

10www.ccc.com2001::1

11www.bb.com192.168.1.5

12www.a.com132.69.34.6

13www.dddd.com3055:1234:5678::1

14www.a.com2003:A::ABC5

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#Domain NameDomain Address

1www.a.com132.68.1.1132.69.1.2132.68.1.3132.68.1.4132.68.1.5

132.69.34.62003:A::ABC5

2 www.bb.com192.168.1.1192.168.1.2192.168.1.3192.168.1.4192.168.1.5

3www.ccc.com2001::1

4www.dddd.com3055:1234:5678::1

Hash container

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Database (cont.)

• .Net Interlocked methods

• Each function is either Writer or Reader

• Wrapped in try finally

• Learns using .Net resolver

Reader

+ 1

FOO()

- 1

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Writer

BAR()

!= 0

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Network Interface• Setting .Net framework to use IPv6• Use .Net Socket class with address families

IPv4 and IPv6• Ability handle large amout of requests

simultaneously Threads

• Starting a new thread is costy• Starting all needed threads at the beginning,

is a waste, and has a management overhead

THREADPOOL

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.NET Threadpool

• Provides a pool of threads that can be used to post work items, process asynchronous I/O, wait on behalf of other threads, and process timers

• System managed

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Network Interface (cont.)• Use StartReceiveFrom which uses threadpool• Each task re-assigns itself• v4 tasks and v6 tasks

DATABASE

MAIN THREAD

THREADPOOL

Uses single time

uses

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Try get query in Non-Blocking manner

Re-assign the task in threadpool

Handle Query

Try get query in Non-Blocking manner

Re-assign the task in threadpool

Handle Query

Try get query in Non-Blocking manner

Re-assign the task in threadpool

Handle Query

Try get query in Non-Blocking manner

Re-assign the task in threadpool

Handle Query

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Use case

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DNSListener Datbase

www.host.com ?

don't konw

external www.host.com?

.NET DNS resolver

www.host.com is 2001::2

User

www.host.com ?

User

www.host.com is 2001::2

www.host.com is 2001::2

www.host.com ?

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User Interface

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On /Off button

Changes it’s text to indicate its functionality

Server Load Indicator

Visualizes the amount of thread pool threads

that are used, from the total amount

allowed (by the user)

Protocols Chooser

Enables the user to choose which of the IP protocols are used as medium to receive requests. If a

queried host has an IPv6 address, although the IPv6 button is not marked, the

IPv6 will return, as long as the query arrived piggy backed on IPv4 packet

Database source file

Here the user inserts the file containing the names to addresses data. Since the server is capable to learn new translations, it is possible to start it with an empty file and let it

learn alone

IPv6 ready logo

This is the IPv6 ready logo which is assigned by

the IPv6 forum. A commercial server would

have need to apply for such a logo, and was

granted one after it was proved as complied with

the IPv6 standard

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Unit Testing

• real-life scenario. Remote applications use the DNS server

• Linux tools (nslookup, dig, etc..)

• Proprietary test application

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Technology• C#• MS .NET Framwork

SocketThreadpoolContainerText.Encoding

• IPv6• DNS• Various Linux DNS test tools

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Conclusions

• Although database strucure is optimized and hash table was used, it is still the bottleneck

• Commercial DNS products do not fully implement standard

• IPv6 support is far from being friendly. MS .Net support not fully works

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Future Work

• IPSEC

• DNS-SEC

• Optimized Caching, threaded $ ?

• Mutual DNS Servers updates

• Server implemented as semi-cluster

• Threadpool fiddling - setMinThreads

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Acknowledgment

We would like to thank Max Uritzky for all the support. Always fast, regardless the day or the time !

And of course, the software lab, for answering our technical needs

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