Throttle a single port to emulate a bandwidth-constrained network

netem.sm

#!/bin/sh -eux

iface=lo
host=127.0.0.1/32
port=80
netem_rule="delay 150ms 10ms loss 0.5%"
upstream_rule="rate 500kbit"
downstream_rule="rate 2mbit"

upstream=1:11
downstream=1:12

# Reset queuing discipline
tc qdisc del dev ${iface} root || true
tc qdisc add dev ${iface} root handle 1: htb
tc class add dev ${iface} parent 1: classid 1:1 htb rate 1Gbps
tc class add dev ${iface} parent 1:1 classid ${upstream} htb ${upstream_rule}
tc class add dev ${iface} parent 1:1 classid ${downstream} htb ${downstream_rule}

# Upstream network emulation
tc qdisc add dev ${iface} parent ${upstream} handle 11: netem ${netem_rule}
tc filter add dev ${iface} \
   protocol ip \
   u32 match ip dst ${host} match ip dport ${port} 0xffff \
   flowid ${upstream}

# Downstream network emulation
tc qdisc add dev ${iface} parent ${downstream} handle 12: netem ${netem_rule}
tc filter add dev ${iface} \
   protocol ip \
   u32 match ip src ${host} match ip sport ${port} 0xffff \
   flowid ${downstream}