A bit of banging away later — I haven’t touched Linux traffic shaping in some years — I’ve got a quick-and-dirty script to set a machine up to temporarily simulate a slow inbound interface for testing.

:::spoiler slow.sh test script

# !/bin/bash
# Linux traffic-shaping occurs on the outbound traffic.  This script
# sets up a virtual interface and places inbound traffic on that virtual
# interface so that it may be rate-limited to simulate a network with a slow inbound connection.
# Removes induced slow-down prior to exiting.

# Physical interface to slow; set as appropriate
oif="wlp2s0"

modprobe ifb numifbs=1
ip link set dev ifb0 up
tc qdisc add dev $oif handle ffff: ingress
tc filter add dev $oif parent ffff: protocol ip u32 match u32 0 0 action mirred egress redirect dev ifb0

tc qdisc add dev ifb0 root handle 1: htb default 10
tc class add dev ifb0 parent 1: classid 1:1 htb rate 1mbit
tc class add dev ifb0 parent 1:1 classid 1:10 htb rate 1mbit

echo "Rate-limiting active.  Hit Control-D to exit."
cat

# shut down rate-limiting
tc qdisc delete dev $oif ingress
tc qdisc delete dev ifb0 root
ip link  set dev ifb0 down
rmmod ifb

:::

I’m going to see whether I can still reproduce that git failure for Cataclysm on git 2.47.2, which is what’s in Debian trixie. As I recall, it got a fair bit of the way into the download before bailing out. Including here since I think that the article makes a good point that there probably should be more slow-network testing, and maybe someone else wants to test something themselves on a slow network.

Probably be better to have something a little fancier to only slow traffic for one particular application — maybe create a “slow Podman container and match on traffic going to that?” — but this is good enough for a quick-and-dirty test.