#!/bin/sh
#
# https://www.bufferbloat.net/projects/codel/wiki/Cake/

ETH=eth1

MTU=1492
# https://www.sonicwall.com/support/knowledge-base/how-can-i-optimize-pppoe-connections/170505851231244/
# https://blog.cloudflare.com/path-mtu-discovery-in-practice/
# https://www.baeldung.com/linux/maximum-transmission-unit-mtu-ip
# https://www.cisco.com/c/en/us/support/docs/ip/transmission-control-protocol-tcp/200932-Ethernet-MTU-and-TCP-MSS-Adjustment-Conc.html
ip link set mtu $MTU dev $ETH

# https://apenwarr.ca/log/20110110

DOWN=45mbit
UP=9mbit

{
modprobe sch_cake
modprobe act_mirred
tc qdisc del dev $ETH root
tc qdisc del dev $ETH ingress
ip link del name ifb4$ETH
} 2>/dev/null

test "$1" = "clear" && exit

tc qdisc add dev $ETH \
  root cake \
  bandwidth $UP \
  ack-filter

test "$1" = "up" && exit

# tc qdisc add dev eth0 root cake help
#
# Usage: ... cake [ bandwidth RATE | unlimited* | autorate-ingress ]
#                 [ rtt TIME | datacentre | lan | metro | regional |
#                   internet* | oceanic | satellite | interplanetary ]
#                 [ besteffort | diffserv8 | diffserv4 | diffserv3* ]
#                 [ flowblind | srchost | dsthost | hosts | flows |
#                   dual-srchost | dual-dsthost | triple-isolate* ]
#                 [ nat | nonat* ]
#                 [ wash | nowash* ]
#                 [ split-gso* | no-split-gso ]
#                 [ ack-filter | ack-filter-aggressive | no-ack-filter* ]
#                 [ memlimit LIMIT ]
#                 [ ptm | atm | noatm* ] [ overhead N | conservative | raw* ]
#                 [ mpu N ] [ ingress | egress* ]
#                 (* marks defaults)

# INGRESS

ip link add name ifb4$ETH type ifb
tc qdisc add dev $ETH handle ffff: ingress
tc qdisc add dev ifb4$ETH \
  root cake \
  bandwidth $DOWN \
  besteffort
ip link set ifb4$ETH up
tc filter add dev $ETH parent ffff: matchall \
  action mirred egress redirect dev ifb4$ETH