bootstrap

#!/bin/bash
# Bootstraps runit config
set -euo pipefail

TZ=${TZ:-Etc/UTC}
PUID=${PUID:-0}
PGID=${PGID:-0}


main() {
    apply_permissions
    configure_timezone
    setup_etc_hosts || true
    setup_iptables || true
    exec "$@"
}


# Apply user id and group id
apply_permissions() {
    if [ ! -e /dev/net/tun ]; then
        fatal "TUN device is not available. Aborting."
    fi

    local group_id=$(stat -c %g /dev/net/tun)
    info "Device /dev/net/tun has group ID '$group_id'"
    if getent group "$group_id" >/dev/null; then
        info "Adding user zerotier-one to group with ID '$group_id'"
        usermod -a -G "$group_id" zerotier-one
    else
        info "Creating group with ID '$group_id' and adding user zerotier-one to it"
        groupadd -g "$group_id" fixtunnel
        usermod -a -G fixtunnel zerotier-one
    fi
    info "Allowing group read/write on /dev/net/tun"
    chmod g+rw /dev/net/tun

    if [ ! -d /var/lib/zerotier-one ]; then
        info "Creating /var/lib/zerotier-one"
        mkdir -p /var/lib/zerotier-one
    fi
    chown zerotier-one:zerotier-one /var/lib/zerotier-one
    chmod 770 /var/lib/zerotier-one
}


# Configure timezone
configure_timezone() {
    export TZ
    if [ ! -f "/usr/share/zoneinfo/$TZ" ]; then
        warn "Unknown timezone $TZ - defaulting to Etc/UTC"
        TZ="Etc/UTC"
    fi
    ln -snf "/usr/share/zoneinfo/$TZ" /etc/localtime
    echo "$TZ" > /etc/timezone
    info "Setting timezone $TZ"
}


# Enable/disable IP protocols in /etc/hosts
setup_etc_hosts() {
    local temp_hosts
    temp_hosts="$(mktemp)"
    cat /etc/hosts > "$temp_hosts"

    if ipv4_enabled; then
        sed -i -E "s/^#(127\.0\.0\.1.*)/\1/" "$temp_hosts"
    else
        sed -i -E "s/^(127\.0\.0\.1.*)/#\1/" "$temp_hosts"
    fi

    if ipv6_enabled; then
        sed -i -E "s/^#(::1.*)/\1/" "$temp_hosts"
    else
        sed -i -E "s/^(::1.*)/#\1/" "$temp_hosts"
    fi

    # /etc/hosts is singularly mounted into the container.
    # sed -i is not really working in-place but instead
    # creates a temp file and then moves it. So would fail
    # on /etc/hosts. Instead of atomically moving
    # we cat the temp file into the destination.
    cat "$temp_hosts" > /etc/hosts
    rm -f "$temp_hosts"
}


# Enable NAT
setup_iptables() {
    if [ -f /proc/sys/net/ipv4/ip_forward -a $(< /proc/sys/net/ipv4/ip_forward) -eq 0 ]; then
        echo 1 > /proc/sys/net/ipv4/ip_forward
    fi
    iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
}


ipv_enabled() {
    local ip_version=$1
    # shellcheck disable=SC2086
    if [ "$(ip -$ip_version addr | wc -l)" -gt 0 ]; then
        return 0
    fi
    return 1
}


ipv4_enabled() {
    ipv_enabled 4
}


ipv6_enabled() {
    ipv_enabled 6
}


# log levels
debug=50
info=40
warn=30
error=20
critical=10
fatal=5
log_level=${log_level:-$debug}


debug()    { logstd $debug    "DEBUG - [$$] - $*"; }
info()     { logstd $info     "INFO - $*"; }
warn()     { logstd $warn     "WARN - $*"; }
error()    { logerr $error    "ERROR - $*"; }
critical() { logerr $critical "CRITIAL - $*"; }
fatal()    { logerr $fatal    "FATAL - $*"; exit 1; }


logstd() {
    local log_at_level
    log_at_level="$1"; shift
    printline "$log_at_level" "$*"
}


logstd() {
    local log_at_level
    log_at_level="$1"; shift
    printline "$log_at_level" "$*"
}


logerr() {
    local log_at_level
    log_at_level="$1"; shift
    printline "$log_at_level" "$*" >&2
}


printline() {
    local log_at_level
    local log_data
    log_at_level="$1"; shift
    log_data="$*"

    if [ "$log_at_level" -le "$log_level" ]; then
        echo "$log_data"
    fi
}


main "$@"