Unbound

Unbound is a validating, recursive, and caching DNS server. It is quite useful for enforcing DNSSEC and caching DNS queries.

Best used in conjunction with DNSCrypt.

Installation

GNU/Linux

Install it from your distro's repository, or download it from here.

Windows

Windows children may download it from the official page.

What to expect

There are numerous advantages to having a DNS server like Unbound, most of which can be summed up in a few short sentences:

• Enforces DNSSEC;
• Reduces privacy exposure by caching DNS queries;
• Consequentially, decreases DNS look up latency if the DNS query has already been cached;
• Hardens DNS queries.

Configuration

This is how a proper unbound.conf file ought to look like: unbound.conf.

General

server:
        interface: 127.0.0.1
        interface: ::1
        verbosity: 1
        port: 53
        do-ip4: yes
        do-ip6: <yes, if your ISP/router supports it>
        do-udp: yes
        do-tcp: yes
        do-daemonize: yes
        logfile: "<where you want your log files to be>"

Performance

        # use all threads
        num-threads: <number of cores*threads>  
        
        # 2^{number_of_cores}  
        msg-cache-slabs: <same>
        rrset-cache-slabs: <same>
        infra-cache-slabs: <same>
        key-cache-slabs: <same>

        # more cache memory, rrset=msg*2
        rrset-cache-size: 100m
        msg-cache-size: 50m

        # more outgoing connections
        # depends on number of threads: 1024/threads - 50 
        outgoing-range: <1024/threads - 50>
        num-queries-per-thread: <(1024/threads)/2>

        # Larger socket buffer
        so-rcvbuf: 4m
        so-sndbuf: 4m

        # Faster UDP with multithreading (only on Linux).
        so-reuseport: yes

Note: If you have libevent, the outgoing-range can be increased to 4096 or 8192, for a slight performance gain. In which case, num-queries-threads should be <(outgoing-range/2)+50> to guarantee that every query can get a socket, and some to spare for queries-for-nameservers.

Security

        hide-identity: yes
        hide-version: yes
        harden-short-bufsize: yes
        harden-large-queries: yes
        harden-glue: yes
        harden-dnssec-stripped: yes
        harden-below-nxdomain: yes
        harden-referral-path: yes
        use-caps-for-id: yes
        # enables support for DNSSEC(!)
        auto-trust-anchor-file: "<path to your root.key file>"

w/ DNSCrypt

        # this is necessary for the local host, in this case DNSCrypt, to be used to send queries
        do-not-query-localhost: no
forward-zone:
        name: "."
        # 127.0.0.1 is DNSCrypt's --local-address; 40 is the port DNSCrypt is using
        forward-addr: 127.0.0.1@40