DNS Server

Mon fournisseur d’accès Internet FREE ne me donnant pas entière satisfaction quant au service DNS (lenteur,problèmes Youtube,…), j’ai décidé d’y remédier de façon simple et efficace, en déployant mon propre serveur cache DNS.

En effet, rien de plus simple pour monter un DNS sur mon réseau LAN. Je connais Bind depuis des années, mais il est complexe, lourd, alors j’ai opté pour UNBOUND, un serveur DNS écrit en Python. J’ai décidé de l’installer sur un de mes serveurs Dockstar, avec la configuration suivante adaptée à mes besoins, que j’ai trouvé sur le site web Calomel.

On va installer le démon UNBOUND sur ma distribution Debian, puis je récupére la liste des serveurs DNS ROOT, sur le site officiel, avec wget.

apt-get install unbound unbound-host
wget ftp://FTP.INTERNIC.NET/domain/named.cache -O /var/lib/unbound/root.hints

Dans la configuration, vous devez adapter les réseaux (le mien est en Vous pouvez également, renseigner la liste de vos machines internes. Dans les champs DNS du serveur DHCP du FreeBox Serveur, pensez à mettre l’adresse ip de votre nouveau serveur DNS.

## Authoritative, validating, recursive caching DNS
## unbound.conf -- https://calomel.org
  # log verbosity
    verbosity: 1

  # specify the interfaces to answer queries from by ip-address.  The default
  # is to listen to localhost ( and ::1).  specify and ::0 to
  # bind to all available interfaces.  specify every interface[@port] on a new
  # 'interface:' labeled line.  The listen interfaces are not changed on
  # reload, only on restart.

  # port to answer queries from
    port: 53

  # Enable IPv4, "yes" or "no".
    do-ip4: yes

  # Enable IPv6, "yes" or "no".
    do-ip6: no

  # Enable UDP, "yes" or "no".
    do-udp: yes

  # Enable TCP, "yes" or "no". If TCP is not needed, Unbound is actually
  # quicker to resolve as the functions related to TCP checks are not done.i
  # NOTE: you may need tcp enabled to get the DNSSEC results from *.edu domains
  # due to their size.
    do-tcp: yes

  # control which client ips are allowed to make (recursive) queries to this
  # server. Specify classless netblocks with /size and action.  By default
  # everything is refused, except for localhost.  Choose deny (drop message),
  # refuse (polite error reply), allow (recursive ok), allow_snoop (recursive
  # and nonrecursive ok)
    access-control: allow
    access-control: allow

  # Read  the  root  hints from this file. Default is nothing, using built in
  # hints for the IN class. The file has the format of  zone files,  with  root
  # nameserver  names  and  addresses  only. The default may become outdated,
  # when servers change,  therefore  it is good practice to use a root-hints
  # file.  get one from ftp://FTP.INTERNIC.NET/domain/named.cache
    root-hints: "/var/lib/unbound/root.hints"

  # enable to not answer id.server and hostname.bind queries.
    hide-identity: yes

  # enable to not answer version.server and version.bind queries.
    hide-version: yes

  # Will trust glue only if it is within the servers authority.
  # Harden against out of zone rrsets, to avoid spoofing attempts. 
  # Hardening queries multiple name servers for the same data to make
  # spoofing significantly harder and does not mandate dnssec.
    harden-glue: yes

  # Require DNSSEC data for trust-anchored zones, if such data is absent, the
  # zone becomes  bogus.  Harden against receiving dnssec-stripped data. If you
  # turn it off, failing to validate dnskey data for a trustanchor will trigger
  # insecure mode for that zone (like without a trustanchor).  Default on,
  # which insists on dnssec data for trust-anchored zones.
    harden-dnssec-stripped: yes

  # Use 0x20-encoded random bits in the query to foil spoof attempts.
  # http://tools.ietf.org/html/draft-vixie-dnsext-dns0x20-00
  # While upper and lower case letters are allowed in domain names, no significance
  # is attached to the case. That is, two names with the same spelling but
  # different case are to be treated as if identical. This means calomel.org is the
  # same as CaLoMeL.Org which is the same as CALOMEL.ORG.
    use-caps-for-id: yes

  # the time to live (TTL) value lower bound, in seconds. Default 0.
  # If more than an hour could easily give trouble due to stale data.
    cache-min-ttl: 3600

  # the time to live (TTL) value cap for RRsets and messages in the
  # cache. Items are not cached for longer. In seconds.
    cache-max-ttl: 86400

  # perform prefetching of close to expired message cache entries.  If a client
  # requests the dns lookup and the TTL of the cached hostname is going to
  # expire in less than 10% of its TTL, unbound will (1st) return the ip of the
  # host to the client and (2nd) pre-fetch the dns request from the remote dns
  # server. This method has been shown to increase the amount of cached hits by
  # local clients by 10% on average.
    prefetch: yes

  # number of threads to create. 1 disables threading. This should equal the number
  # of CPU cores in the machine. Our example machine has 4 CPU cores.
    num-threads: 2

  ## Unbound Optimization and Speed Tweaks ###

  # the number of slabs to use for cache and must be a power of 2 times the
  # number of num-threads set above. more slabs reduce lock contention, but
  # fragment memory usage.
    msg-cache-slabs: 8
    rrset-cache-slabs: 8
    infra-cache-slabs: 8
    key-cache-slabs: 8

  # Increase the memory size of the cache. Use roughly twice as much rrset cache
  # memory as you use msg cache memory. Due to malloc overhead, the total memory
  # usage is likely to rise to double (or 2.5x) the total cache memory. The test
  # box has 4gig of ram so 256meg for rrset allows a lot of room for cacheed objects.
    rrset-cache-size: 25m
    msg-cache-size: 12m

  # buffer size for UDP port 53 incoming (SO_RCVBUF socket option). This sets
  # the kernel buffer larger so that no messages are lost in spikes in the traffic.
    so-rcvbuf: 1m

  ## Unbound Optimization and Speed Tweaks ###

  # Enforce privacy of these addresses. Strips them away from answers.  It may
  # cause DNSSEC validation to additionally mark it as bogus.  Protects against
  # 'DNS Rebinding' (uses browser as network proxy).  Only 'private-domain' and
  # 'local-data' names are allowed to have these private addresses. No default.

  # Allow the domain (and its subdomains) to contain private addresses.
  # local-data statements are allowed to contain private addresses too.
    private-domain: "home.lan"

  # If nonzero, unwanted replies are not only reported in statistics, but also
  # a running total is kept per thread. If it reaches the threshold, a warning
  # is printed and a defensive action is taken, the cache is cleared to flush
  # potential poison out of it.  A suggested value is 10000000, the default is
  # 0 (turned off). We think 10K is a good value.
    unwanted-reply-threshold: 10000

  # IMPORTANT FOR TESTING: If you are testing and setup NSD or BIND  on
  # localhost you will want to allow the resolver to send queries to localhost.
  # Make sure to set do-not-query-localhost: yes . If yes, the above default
  # do-not-query-address entries are present.  if no, localhost can be queried
  # (for testing and debugging). 
    do-not-query-localhost: no

  # File with trusted keys, kept up to date using RFC5011 probes, initial file
  # like trust-anchor-file, then it stores metadata.  Use several entries, one
  # per domain name, to track multiple zones. If you use forward-zone below to
  # query the Google DNS servers you MUST comment out this option or all DNS
  # queries will fail.
    auto-trust-anchor-file: "/var/lib/unbound/root.key"

  # Should additional section of secure message also be kept clean of unsecure
  # data. Useful to shield the users of this validator from potential bogus
  # data in the additional section. All unsigned data in the additional section
  # is removed from secure messages.
    val-clean-additional: yes

  # Blocking Ad Server domains. Google's AdSense, DoubleClick and Yahoo
  # account for a 70 percent share of all advertising traffic. Block them.
    local-zone: "doubleclick.net" redirect
    local-data: "doubleclick.net A"
    local-zone: "googlesyndication.com" redirect
    local-data: "googlesyndication.com A"
    local-zone: "googleadservices.com" redirect
    local-data: "googleadservices.com A"
    local-zone: "google-analytics.com" redirect
    local-data: "google-analytics.com A"
    local-zone: "ads.youtube.com" redirect
    local-data: "ads.youtube.com A"
    local-zone: "adserver.yahoo.com" redirect
    local-data: "adserver.yahoo.com A"

  # Unbound will not load if you specify the same local-zone and local-data
  # servers in the main configuration as well as in this "include:" file. We
  # suggest commenting out any of the local-zone and local-data lines above if
  # you suspect they could be included in the unbound_ad_servers servers file.
  #include: "/usr/local/etc/unbound/unbound_ad_servers"

  # locally served zones can be configured for the machines on the LAN.

    local-zone: "lan." static

    local-data: "dockstar1.      IN A"
    local-data: "dockstar2.      IN A"
    local-data: "haproxy.        IN A"
    local-data: "beaglebone.     IN A"
    local-data: "raspberry.      IN A"

    local-data-ptr: "  dockstar1.lan"
    local-data-ptr: "  dockstar2.lan"
    local-data-ptr: "  haproxy.lan"
    local-data-ptr: "  beaglebone.lan"
    local-data-ptr: "  raspberry.lan"

  # Unbound can query your NSD or BIND server for private domain queries too.
  # On our NSD page we have NSD configured to serve the private domain,
  # "home.lan". Here we can tell Unbound to connect to the NSD server when it
  # needs to resolve a *.home.lan hostname or IP.
  # private-domain: "home.lan"
  # local-zone: "0.0.10.in-addr.arpa." nodefault
  # stub-zone:
  #      name: "home.lan"
  #      stub-addr:

  # If you do not want to use the root DNS servers you can use the following
  # forward-zone to forward all queries to Google DNS, OpenDNS.com or your
  # local ISP's dns servers for example. If use use forward-zone you must make
  # sure to comment out the auto-trust-anchor-file directive above or else all
  # DNS queries will fail. We highly suggest using Google DNS as it is
  # extremely fast.
  #  forward-zone:
  #     name: "."
  #     forward-addr:        # Google Public DNS
  #     forward-addr:    # Hurricane Electric
  #     forward-addr:        # Level3 Verizon
## Authoritative, validating, recursive caching DNS
## unbound.conf -- https://calomel.org

Après avoir changé la configuration DNS de machine qui va faire office de serveur DNS, taper la commande suivante, afin de vérifier que la résolution est bien réalisée :

unbound-host google.fr 

Et alors, à vous les vidéos Youtube en 1080p avec la FreeBox !!!