Good day, According to this link: http://linux-tc-notes.sourceforge.net/tc/doc/sch_noqueue.txt it should not be possible to assign noqueue qdisc to physical devices or classes. Yet, I can clearly do it even on the latest 5.0-rc series kernels:
$ sudo tc qdisc add dev eth0 root noqueue $ sudo tc qdisc show dev eth0 qdisc noqueue 8005: root refcnt 385 If I understand the source correctly, noqueue qdisc was designed only for network interfaces, which have IFF_NO_QUEUE in priv_flags in net_device structure. However, I see no checks in the code, which enforce it when attaching this qdisc to an interface. I believe, it was not possible before, but commit d66d6c3152e8d5a6db42a56bf7ae1c6cae87ba48 changed that. Regardless, if it is intentional or not, the change is incomplete as it introduces a potential NULL ptr dereference bug, which can be triggered by doing something like: dev="eth0" sudo tc qdisc replace dev $dev root noqueue sudo tc qdisc delete dev $dev root sudo tc qdisc replace dev $dev root handle 1: htb default 1 sudo tc class add dev $dev parent 1: classid 1:1 htb rate 1000Gbps sudo tc qdisc add dev $dev parent 1:1 handle 10: noqueue I believe it should not be possible to have noqueue qdisc on physical nics, but, please, let me know if I'm wrong. Regards, Ignat
