#!/bin/sh
# SPDX-License-Identifier: MIT
#
# Remove qosify qdiscs and ifb devices left behind after qosify exits.
#
# A clean stop only does part of this: interface_clear_qdisc() removes the root
# qdisc, the bpf filters and the ifb device but not clsact, and main() never
# calls qosify_dns_stop(), so ifb-dns stays up. A crash, a SIGKILL or a respawn
# loop leaves the rest too. This script deliberately only touches the devices of
# enabled qosify sections, the ifb names qosify derives from them and qosify's
# own ifb-dns -- never a qdisc or ifb qosify did not create.
#
# `cleanup wait` is for a package removal: qosify is stopped by its own prerm,
# which may run after ours, so the device names are read now and the sweep waits
# up to 30 s for qosify to exit. If it is still running, nothing is touched.

. /lib/functions.sh
. /lib/functions/network.sh

# The lock is an flock on an open fd, not a directory plus an EXIT trap: rpcd
# SIGKILLs this script at its exec timeout (rpc_file_exec_timeout_cb() in
# file.c), the trap never runs, and the leftover directory would then make every
# later run exit 0 without doing anything. The kernel drops an flock on process
# exit however the process dies. The path differs from the old directory so a
# stale one left by an earlier version cannot break the redirect. Without
# busybox flock, run unlocked rather than not at all -- the worst a concurrent
# run can do is repeat a tc delete.
LOCK="/var/lock/qosify-luci-cleanup.lock"

mkdir -p /var/lock
exec 9>"$LOCK"
command -v flock >/dev/null && { flock -n 9 || exit 0; }

# Mirrors interface_ifb_name() in qosify: "ifb-<dev>" while strlen(dev) + 4 is
# below IFNAMSIZ. Longer names take a different branch upstream which we do not
# try to reproduce here.
ifb_name() {
	[ "${#1}" -lt 12 ] || return 1
	echo "ifb-$1"
}

qosify_filter() {
	tc filter show dev "$1" "$2" 2>/dev/null | grep -q ' qosify_'
}

# qosify's filters sit at QOSIFY_PRIO_BASE (0x110 = 272): its bpf classifier on
# egress, and on ingress the classifier plus the DNS and ifb redirects up to 277.
# A clean exit removes them and the root qdisc, so they only survive a crash, and
# then the root cake is qosify's too. Another shaper's root qdisc, and a clsact
# carrying anyone else's filters, are left alone.
clear_dev() {
	local dev="$1"
	local ifb p

	[ -n "$dev" ] || return 0

	if [ -e "/sys/class/net/$dev" ]; then
		if qosify_filter "$dev" egress; then
			tc qdisc del dev "$dev" root 2>/dev/null
			tc filter del dev "$dev" egress pref 272 2>/dev/null
		fi
		if qosify_filter "$dev" ingress; then
			for p in 272 273 274 275 276 277; do
				tc filter del dev "$dev" ingress pref "$p" 2>/dev/null
			done
		fi
		[ -n "$(tc filter show dev "$dev" ingress 2>/dev/null)$(tc filter show dev "$dev" egress 2>/dev/null)" ] ||
			tc qdisc del dev "$dev" clsact 2>/dev/null
	fi

	# An ifb outlives its parent, so this is not gated on $dev still existing.
	# That only helps a `config device`, whose name survives the netdev.
	ifb="$(ifb_name "$dev")" || return 0
	[ -e "/sys/class/net/$ifb" ] || return 0

	ip link set "$ifb" down 2>/dev/null
	ip link del "$ifb" 2>/dev/null
}

# add_interface() in qosify.init returns before reading anything else when
# disabled is set, so qosify never touched those devices.
section_enabled() {
	local disabled

	config_get_bool disabled "$1" disabled 0
	[ "$disabled" -eq 0 ]
}

# `config interface` names a netifd interface, not a device; qosify resolves it
# to .l3_device before touching tc, so resolve it the same way. netifd drops
# .l3_device when the interface goes down, so a vanished pppoe device leaves no
# name to derive the ifb from here. qosify clears that one itself: on the next
# up, interface_start() runs interface_clear_qdisc(), which deletes ifb-<dev>
# before cmd_add_ingress() creates it again.
collect_interface() {
	local cfg="$1"
	local name dev

	section_enabled "$cfg" || return 0
	config_get name "$cfg" name
	[ -n "$name" ] || return 0

	network_get_device dev "$name" && DEVS="$DEVS $dev"
}

# `config device` names a netdev directly.
collect_device() {
	local cfg="$1"
	local name

	section_enabled "$cfg" || return 0
	config_get name "$cfg" name
	[ -n "$name" ] && DEVS="$DEVS $name"
}

DEVS=""
config_load qosify
config_foreach collect_interface interface
config_foreach collect_device device

if [ "$1" = wait ]; then
	n=30
	while pidof qosify >/dev/null; do
		[ "$n" -gt 0 ] || exit 0
		n=$((n - 1))
		sleep 1
	done
fi

for dev in $DEVS; do clear_dev "$dev"; done

# ifb-dns is qosify's fixed DNS ifb, not derived from any section, and a stop
# leaves it up under the kernel's default fq_codel. Deleting its root qdisc only
# re-attaches the default, so drop the device -- only once qosify has exited.
pidof qosify >/dev/null || ip link del ifb-dns 2>/dev/null

exit 0