#!/bin/bash

# Init script for build2 buildos.
#
# Loosely based on the one that comes in Debian initrd.img (since we are
# using its kernel image as is).
#
trap "exit 1" ERR
set -o errtrace # Trap in functions.

# Note: diagnostics goes to stdout.
#
function info () { echo "$*"; }
function error () { info "$*"; exit 1; }

export PATH=/sbin:/usr/sbin:/bin:/usr/bin

# One would expect rootflags=size=1g to work but it doesn't (perhaps init
# is expected to interpret it)?
#
mount -o remount,size=1G /

mkdir -p /sys /proc
mount -t sysfs -o nodev,noexec,nosuid sysfs /sys
mount -t proc -o nodev,noexec,nosuid proc /proc

info "init starting up..."

mount -t devtmpfs -o nosuid,mode=0755 udev /dev
mkdir -p /dev/pts
mount -t devpts -o noexec,nosuid,gid=5,mode=0620 devpts /dev/pts || true

mkdir -p /run
mount -t tmpfs -o "noexec,nosuid,size=10%,mode=0755" tmpfs /run

mkdir -p /tmp
mount -t tmpfs -o "nodev,nosuid,size=10%,mode=1777" tmpfs /tmp

# Start udev.
#
# Based on Debian initrd's init-top/udev. Note that we don't stop it at
# at the end of init.
#
info "starting udev..."

if [ -w /sys/kernel/uevent_helper ]; then
  echo >/sys/kernel/uevent_helper
fi

SYSTEMD_LOG_LEVEL=info /lib/systemd/systemd-udevd --daemon --resolve-names=never

udevadm trigger --action=add
udevadm settle || true

# Parse command line.
#
cmdline="$(cat /proc/cmdline)"
info "boot cmdline: $cmdline"

# Figure out network configuration and generate the corresponding
# /etc/network/interfaces.
#
info "starting network..."

# We are using udev's predictable interface names. The two character prefixes
# based on the type of interface:
#
#  en -- ethernet
#  sl -- serial line IP (slip)
#  wl -- wlan
#  ww -- wwan
#
eth_all="$(cd /sys/class/net && ls -d en?*)"

if [ -z "$eth_all" ]; then
  info "no ethernet interfaces found among:"
  ip link show
fi

eth=
eth_up=
for s in 1 2 4 8; do

  # Try to bring them all up and find the one that has carrier.
  #
  for i in $eth_all; do
    ip link set "$i" up || true
  done

  sleep "$s"

  for i in $eth_all; do
    if [ "$(cat "/sys/class/net/$i/carrier")" -eq "1" ]; then
      info "detected carrier on $i"
      eth_up+=" $i"
    fi
  done

  # Bring them all down.
  #
  for i in $eth_all; do
    ip link set "$i" down || true
  done

  # If we didn't find anything, try to wait for carrier longer.
  #
  if [ -z "$eth_up" ]; then
    continue
  fi

  # If we end up with several interfaces we simply unleash dhcp on all of
  # them and use the first that gets configured.
  #
  # Note also that it's possible the interface that we want is not yet ready
  # in which case we will try to wait for carrier a bit longer.
  #
  for i in $eth_up; do
    if dhclient -v "$i"; then
      eth="$i"
      break
    fi
  done

  if [ -n "$eth" ]; then
    break
  fi
done

if [ -z "$eth_up" ]; then
  error "no ethernet interfaces with carrier among:"
  ip link show
fi

if [ -z "$eth" ]; then
  error "no ethernet interfaces with DHCP among:"
  ip link show
fi

mac="$(cat "/sys/class/net/$eth/address")"
mid="$(sed -e 's/://g' <<<"$mac")" # Machine id.

info "configured $eth ($mac)"

# Set the hostname.
#
hname="$(hostname)"
if [ "$hname" = "(none)" ]; then
  hname="build-$mid"
  hostname "$hname"
fi
echo "$hname" >/etc/hostname

info "hostname $hname"

# Stop DHCP client without releasing the lease and deconfigure the interface.
# The plan is to generate a bridge-based /etc/network/interfaces configuration
# based on what we have discovered and then let the systemd networking bringup
# to configure everything (at which point we will hopefully reuse the lease).
#
dhclient -q -x

# @@ Need to be make configurable.
#
priv_network="172.16.123.0"
priv_netmask="255.255.255.0"
priv_netbase="$(sed -e 's/^\(.*\)\.0$/\1/' <<<"$priv_network")"

cat <<EOF >/etc/network/interfaces
auto lo
iface lo inet loopback

# Public bridge.
#
auto br0
iface br0 inet dhcp
    bridge_ports   $eth
    bridge_stp     off
    bridge_maxwait 0
    bridge_fd      0
    bridge_mac     $mac

# Private bridge with NAT to br0.
#
auto br1
iface br1 inet static
    address ${priv_netbase}.1
    netmask $priv_netmask
    bridge_ports   none
    bridge_stp     off
    bridge_maxwait 0
    bridge_fd      0
    post-up iptables -t nat -A POSTROUTING -o br0 -j MASQUERADE
    post-up iptables -A FORWARD -i br0 -o br1 -m state --state RELATED,ESTABLISHED -j ACCEPT
    post-up iptables -A FORWARD -i br1 -o br0 -j ACCEPT
EOF

cat <<EOF >/etc/dnsmasq.d/br1-dhcp
interface=br1
bind-interfaces
dhcp-range=${priv_netbase}.10,${priv_netbase}.250,12h
EOF

/bin/bash

# Hand off to systemd. But first arrange to keep console output (which
# becomes tty1).
#
mkdir -p /etc/systemd/system/getty@tty1.service.d
cat <<EOF >/etc/systemd/system/getty@tty1.service.d/noclear.conf
[Service]
TTYVTDisallocate=no
EOF

exec /lib/systemd/systemd \
  --show-status=1 \
  --machine-id="00000000000000000000$mid" \
  </dev/console >/dev/console 2>&1