Re: [PATCH net v2] net/sched: sch_hfsc: fix divide-by-zero in rtsc_min()

[Jakub Kicinski <kuba@kernel.org>]

On Thu, 26 Mar 2026 11:54:52 -0700 Xiang Mei wrote:
> PoC:
> ```sh
> #!/bin/sh
> ip link set lo up
> 
> tc qdisc replace dev lo root handle 1: \
>     stab overhead 3000000 mtu 0 tsize 0 \
>     hfsc default 1
> tc class replace dev lo parent 1: classid 1:1 hfsc \
>     rt m1 32gbit d 1ms m2 0bit \
>     ls m1 32gbit d 1ms m2 0bit
> 
> # Send UDP to loopback (same method as C PoC)
> python3 -c "
> import socket,time
> s=socket.socket(socket.AF_INET,socket.SOCK_DGRAM)
> s.sendto(b'A'*64,('127.0.0.1',1337))  # activate class
> time.sleep(1)                           # drain → idle
> s.sendto(b'A'*64,('127.0.0.1',1337))  # reactivation → div-by-zero
> "
> ```

Please turn this into a TDC selftest.