====== Ubuntu - Networking - DNS - Unbound - Install Unbound ======

===== Install Unbound =====

<code bash>
sudo apt install unbound
</code>

----

===== Obtain root server hints =====

Unbound uses DNS root servers by default.

When recursively querying a host that is not cached as an address, the resolver starts at the top of the server tree and queries the root servers, to know where to go for the top level domain for the address being queried.

<code bash>
wget -O root.hints https://www.internic.net/domain/named.root
sudo mv root.hints /var/lib/unbound/
</code>

<WRAP info>
**NOTE:**  This file should probably be refreshed every 6 months.
</WRAP>

----

===== Configure Unbound =====

Create a configuration file under **/etc/unbound/unbound.conf.d/**.

The file can be named anything; here **ubuntu.conf** is used.

<file bash /etc/unbound/unbound.conf.d/ubuntu.conf>
server:
    # The  verbosity  number.
    #   level 0 means no verbosity, only errors.
    #   Level 1 gives operational information.
    #   Level 2 gives detailed operational  information.
    #   Level 3 gives query level information output per query.
    #   Level 4 gives algorithm level information.
    #   Level 5 logs client identification for cache misses.
    # Default is level 1.
    verbosity: 0
    
    interface: 127.0.0.1
    port: 5335
    do-ip4: yes
    do-udp: yes
    do-tcp: yes
    
    # May be set to yes if you have IPv6 connectivity.
    do-ip6: no

    # You want to leave this to no unless you have *native* IPv6.
    # With 6to4 and Terredo tunnels your web browser should favour IPv4 for the same reasons.
    prefer-ip6: no
    
    # Use this only when you downloaded the list of primary root servers!
    # Read  the  root  hints from this file.
    # Make sure to update root.hints every 6 months.
    root-hints: "/var/lib/unbound/root.hints"
    
    # Trust glue only if it is within the servers authority.
    harden-glue: yes
    
    # Ignore very large queries.
    harden-large-queries: yes
    
    # Require DNSSEC data for trust-anchored zones, if such data is absent, the zone becomes BOGUS.
    # If you want to disable DNSSEC, set harden-dnssec stripped: no
    harden-dnssec-stripped: yes
    
    # Number of bytes size to advertise as the EDNS reassembly buffer size.
    # This is the value put into  datagrams over UDP towards peers.
    # The actual buffer size is determined by msg-buffer-size (both for TCP and UDP).
    edns-buffer-size: 1232
    
    # Rotates RRSet order in response (the pseudo-random number is 
    # taken from Ensure privacy of local IP ranges the query ID, for speed and thread safety).  
    # private-address: 192.168.0.0/16
    rrset-roundrobin: yes
    
    # Time to live minimum for RRsets and messages in the cache.
    # If the minimum kicks in, the data is cached for longer than the domain owner intended,
    # and thus less queries are made to look up the data.
    # Zero makes sure the data in the cache is as the domain owner intended, higher values,
    # especially more than an hour or so, can lead to trouble as the data in the cache 
    # does not match up with the actual data anymore
    cache-min-ttl: 300
    cache-max-ttl: 86400
    
    # Have unbound attempt to serve old responses from cache with a TTL of 0 in
    # the response without waiting for the actual resolution to finish.
    # The actual resolution answer ends up in the cache later on. 
    serve-expired: yes
    
    # Harden against algorithm downgrade when multiple algorithms are
    # advertised in the DNS record.
    harden-algo-downgrade: yes
    
    # Ignore very small EDNS buffer sizes from queries.
    harden-short-bufsize: yes
    
    # Refuse id.server and hostname.bind queries.
    hide-identity: yes
    
    # Report this identity rather than the hostname of the server.
    identity: "Server"
    
    # Refuse version.server and version.bind queries.
    hide-version: yes
    
    # Prevent the unbound server from forking into the background as a daemon.
    do-daemonize: no
    
    # Number  of  bytes size of the aggressive negative cache.
    neg-cache-size: 4M
    
    # Send minimum amount of information to upstream servers to enhance privacy.
    qname-minimisation: yes
    
    # Deny queries of type ANY with an empty response.
    # Works only on version 1.8 and above.
    deny-any: yes

    # Do no insert authority/additional sections into response messages when
    # those sections are not required.
    # This reduces response size significantly, and may avoid TCP fallback for 
    # some responses. This may cause a slight speedup.
    minimal-responses: yes
    
    # Perform prefetching of close to expired message cache entries.
    # This only applies to domains that have been frequently queried.
    # This flag updates the cached domains.
    prefetch: yes
    
    # Fetch the DNSKEYs earlier in the validation process, when a DS record is
    # encountered.
    # This lowers the latency of requests at the expense of little more CPU usage.
    prefetch-key: yes
    
    # One thread should be sufficient, can be increased on beefy machines.
    # In reality for most users running on small networks or on a single machine, it should be unnecessary
    # to seek performance enhancement by increasing num-threads above 1.
    num-threads: 1

    # More cache memory.
    # rrset-cache-size should twice what msg-cache-size is.
    msg-cache-size: 50m
    rrset-cache-size: 100m
   
    # Faster UDP with multithreading (only on Linux).
    so-reuseport: yes
    
    # Ensure kernel buffer is large enough to not lose messages in traffic spikes.
    so-rcvbuf: 4m
    so-sndbuf: 4m
    
    # Set the total number of unwanted replies to keep track of in every thread.
    # When it reaches the threshold, a defensive action of clearing the rrset
    # and message caches is taken, hopefully flushing away any poison.
    # Unbound suggests a value of 10 million.
    unwanted-reply-threshold: 100000
    
    # Minimize logs.
    # Do not print one line per query to the log.
    log-queries: no
    
    # Do not print one line per reply to the log.
    log-replies: no
    
    # Do not print log lines that say why queries return SERVFAIL to clients.
    log-servfail: no
    
    # Do not print log lines to inform about local zone actions.
    log-local-actions: no
    
    # Do not print log lines that say why queries return SERVFAIL to clients.
    logfile: /dev/null
    
    # Ensure privacy of local IP ranges.
    private-address: 192.168.0.0/16
    private-address: 169.254.0.0/16
    private-address: 172.16.0.0/12
    private-address: 10.0.0.0/8
    private-address: fd00::/8
    private-address: fe80::/10
</file>

<WRAP info>
**NOTE:**  The file under **/etc/unbound/unbound.conf.d/** can be named anything.
</WRAP>


----

===== Check unbound config file for errors =====

<code bash>
unbound-checkconf /etc/unbound/unbound.conf.d/ubuntu.conf
</code>

<WRAP info>
**NOTE:**  This should return no errors.
</WRAP>


----

===== Start unbound service =====

<code bash>
sudo service unbound start
</code>

----

===== Test =====

Check whether the domain is resolving.

<code bash>
dig sharewiz.net @127.0.0.1 -p 5335
</code>


<WRAP info>
**NOTE:**  The first query will be slow but the subsequent queries should resolve much quicker; probably within 1ms.
</WRAP>