RUN build_deps="curl gcc libc-dev libevent-dev libexpat1-dev libnghttp2-dev make flex bison" && \
    set -x && \
    DEBIAN_FRONTEND=noninteractive apt-get update && apt-get install -y --no-install-recommends \
      $build_deps \
      bsdmainutils \
      ca-certificates \
      ldnsutils \
      libevent-2.1-7 \
      libexpat1 \
      libprotobuf-c-dev \
      protobuf-c-compiler && \
    git clone https://github.com/NLnetLabs/unbound.git && \
    cd unbound && \
    groupadd _unbound && \
    useradd -g _unbound -s /dev/null -d /etc _unbound && \
    ./configure \
        --disable-dependency-tracking \
        --prefix=/opt/unbound \
        --with-pthreads \
        --with-username=_unbound \
        --with-ssl=/opt/openssl \
        --with-libevent \
        --with-libnghttp2 \
        --enable-dnstap \
        --enable-tfo-server \
        --enable-tfo-client \
        --enable-event-api \
        --enable-subnet && \
    make install