#!/bin/bash
#
# SPDX-License-Identifier: LGPL-2.1+
#

set -eu

LXC_DHCP_SCRIPT="/usr/share/lxc/hooks/dhclient-script"
LXC_DHCP_CONFIG="/etc/lxc/dhclient.conf"

rootfs_path="${LXC_ROOTFS_PATH#*:}"
hookdir="${rootfs_path/%rootfs/hook}"

conffile_arg=""
if [ -e "${LXC_DHCP_CONFIG}" ]; then
    conffile_arg="-cf ${LXC_DHCP_CONFIG}"
fi

debugfile="/dev/null"
if [ "${LXC_LOG_LEVEL}" = "DEBUG" ] || [ "${LXC_LOG_LEVEL}" = "TRACE" ]; then
    debugfile="${hookdir}/dhclient.log"
    echo "INFO: Writing dhclient log at ${debugfile}." >&2
fi

pidfile="${hookdir}/dhclient.pid"
leasefile="${hookdir}/dhclient.leases"

usage() {
    echo "Usage: ${0##*/} <name> lxc {start-host|stop}"
}

# Wrap the dhclient command with "aa-exec -p unconfined" if AppArmor is enabled.
dhclient() {
    bin="/sbin/dhclient"
    if [ -d "/sys/kernel/security/apparmor" ] && command -v aa-exec >/dev/null; then
        bin="aa-exec -p unconfined ${bin}"
    fi
    echo $bin
}

dhclient_start() {
    ns_args=("--uts" "--net")
    if [ -z "$(readlink /proc/${LXC_PID}/ns/user /proc/self/ns/user | uniq -d)" ]; then
        ns_args+=("--user")
    fi

    mkdir -p "${hookdir}"

    if [ -e "${pidfile}" ]; then
        echo "WARN: DHCP client is already running, skipping start hook." >> "${debugfile}"
    else
        echo "INFO: Starting DHCP client and acquiring a lease..." >> "${debugfile}"
        nsenter ${ns_args[@]} --target "${LXC_PID}" -- \
          $(dhclient) -1 ${conffile_arg} -pf "${pidfile}" -lf "${leasefile}" -e "ROOTFS=${rootfs_path}" -sf "${LXC_DHCP_SCRIPT}" -v >> "${debugfile}" 2>&1
    fi
}

dhclient_stop() {
    # We can't use LXC_PID here since the container process has exited,
    # use the namespace file descriptors in the hook arguments instead.
    ns_args=("")
    if [ "${LXC_HOOK_VERSION:-0}" -eq 0 ]; then
        for arg in "$@"; do
            case "${arg}" in
                uts:* | user:* | net:*) ns_args+=("--${arg/:/=}") ;;
                *) ;;
            esac
        done
    else
        ns_args+=("--uts=${LXC_UTS_NS}")
        ns_args+=("--net=${LXC_NET_NS}")
        [ -n "${LXC_USER_NS:+x}" ] && ns_args+=("--user=${LXC_USER_NS}")
    fi

    if [ -e "${pidfile}" ]; then
        echo "INFO: Stopping DHCP client and releasing leases..." >> "${debugfile}"
        nsenter ${ns_args[@]} -- \
          $(dhclient) -r ${conffile_arg} -pf "${pidfile}" -lf "${leasefile}" -e "ROOTFS=${rootfs_path}" -sf "${LXC_DHCP_SCRIPT}" -v >> "${debugfile}" 2>&1
    else
        echo "WARN: DHCP client is not running, skipping stop hook." >> "${debugfile}"
    fi

    # dhclient could fail to release the lease and shutdown, try to cleanup after ourselves just in case.
    nsenter ${ns_args[@]} -- \
      /bin/sh -c 'pkill --ns $$ --nslist net -f "^/sbin/dhclient"' || true
    rm -f "${pidfile}"
}

HOOK_SECTION=
HOOK_TYPE=
case "${LXC_HOOK_VERSION:-0}" in
    0) HOOK_SECTION="${2:-}"; HOOK_TYPE="${3:-}"; shift 3;;
    1) HOOK_SECTION="${LXC_HOOK_SECTION:-}"; HOOK_TYPE="${LXC_HOOK_TYPE:-}";;
    *) echo "ERROR: Unsupported hook version: ${LXC_HOOK_VERSION}." >&2; exit 1;;
esac

if [ "${HOOK_SECTION}" != "lxc" ]; then
    echo "ERROR: Not running through LXC." >&2
    exit 1
fi

case "${HOOK_TYPE}" in
    start-host) dhclient_start $@;;
    stop) dhclient_stop $@;;
    *) usage; exit 1;;
esac

exit 0
