TC classifier not found

[lvd79]

Using latest vrnetlab version v0.21 containerlab fails to create links between SROS VM containers.

2025-04-05 13:24:54,956: vrnetlab       DEBUG waiting for provisioned interfaces to appear...
2025-04-05 13:24:54,957: vrnetlab       DEBUG highest allocated interface id determined to be: 2...
2025-04-05 13:24:54,957: vrnetlab       DEBUG interfaces provisioned, continuing...
2025-04-05 13:24:54,958: vrnetlab       DEBUG qemu cmd: qemu-system-x86_64 -enable-kvm -display none -machine pc -monitor tcp:0.0.0.0:4001,server,nowait -serial telnet:0.0.0.0:5001,server,nowait -m 6144 -cpu host -smp 2 -drive if=virtio,file=/sros-overlay-lc1.qcow2 -uuid a2ca28fd-0d5a-4f0d-9855-dd831ed9e3f2 -smbios "type=1,product=TIMOS:slot=1 chassis=SR-14s sfm=sfm-s card=xcm-14s mda/1=s36-100gb-qsfp28" -device pci-bridge,chassis_nr=1,id=pci.1 -device pci-bridge,chassis_nr=2,id=pci.2 -device virtio-net-pci,netdev=mgmt,mac=0C:00:61:e1:5e:00 -netdev user,id=mgmt,restrict=y -device virtio-net-pci,netdev=vfpc-int,mac=0C:00:4d:ad:7e:00 -netdev tap,ifname=vfpc1-int,id=vfpc-int,script=no,downscript=no -device virtio-net-pci,netdev=p01,bus=pci.1,addr=0x2 -netdev socket,id=p01,listen=:10001 -device virtio-net-pci,netdev=p02,mac=0C:00:52:59:39:02,bus=pci.1,addr=0x3 -netdev tap,id=p02,ifname=tap2,script=/etc/tc-tap-ifup,downscript=no
2025-04-05 13:24:55,726: vrnetlab       INFO STDOUT: 
2025-04-05 13:24:55,726: vrnetlab       INFO STDERR: Error: TC classifier not found.
We have an error talking to the kernel
Error: TC classifier not found.
We have an error talking to the kernel
qemu-system-x86_64: -netdev tap,id=p02,ifname=tap2,script=/etc/tc-tap-ifup,downscript=no: network script /etc/tc-tap-ifup failed with status 512

Running the /etc/tc-tap-if-up.sh directly within the container produces the same result. The changes to common/vrnetlab.py included in release v0.21 seem to be incompatible with some Linux distributions.

This issue was encountered on Flatcar linux 4081.3.2 kernel 6.6.83-flatcar .

Reverting the tc mirror configuration resolved the issue.

tc qdisc add dev eth$INDEX ingress
tc filter add dev eth$INDEX parent ffff: protocol all u32 match u8 0 0 action mirred egress redirect dev tap$INDEX

tc qdisc add dev $TAP_IF ingress
tc filter add dev $TAP_IF parent ffff: protocol all u32 match u8 0 0 action mirred egress redirect dev eth$INDEX

[hellt]

Yes, support for tc in the kernel is mandatory, otherwise the datapath stitching won't work

[lvd79]

Hi, The kernel is compiled with TC support. It's just that the best practice does not work on the Flatcar OS version. This could affect deployments using older versions of iproute2.

The change was introduced less than a year ago.
iproute2/iproute2@dedcf62

tc utility, iproute2-6.9.0
core@localhost / $ grep NET_SCH /usr/boot/config-6.6.83-flatcar
CONFIG_NET_SCHED=y
CONFIG_NET_SCH_HTB=m
CONFIG_NET_SCH_HFSC=m
CONFIG_NET_SCH_PRIO=m
CONFIG_NET_SCH_MULTIQ=m
CONFIG_NET_SCH_RED=m
CONFIG_NET_SCH_SFB=m
CONFIG_NET_SCH_SFQ=m
CONFIG_NET_SCH_TEQL=m
CONFIG_NET_SCH_TBF=m
# CONFIG_NET_SCH_CBS is not set
# CONFIG_NET_SCH_ETF is not set
CONFIG_NET_SCH_MQPRIO_LIB=m
# CONFIG_NET_SCH_TAPRIO is not set
CONFIG_NET_SCH_GRED=m
CONFIG_NET_SCH_NETEM=m
CONFIG_NET_SCH_DRR=m
CONFIG_NET_SCH_MQPRIO=m
# CONFIG_NET_SCH_SKBPRIO is not set
CONFIG_NET_SCH_CHOKE=m
CONFIG_NET_SCH_QFQ=m
CONFIG_NET_SCH_CODEL=m
CONFIG_NET_SCH_FQ_CODEL=m
# CONFIG_NET_SCH_CAKE is not set
CONFIG_NET_SCH_FQ=m
CONFIG_NET_SCH_HHF=m
CONFIG_NET_SCH_PIE=m
# CONFIG_NET_SCH_FQ_PIE is not set
CONFIG_NET_SCH_INGRESS=m
CONFIG_NET_SCH_PLUG=m
# CONFIG_NET_SCH_ETS is not set
# CONFIG_NET_SCH_DEFAULT is not set
CONFIG_NET_SCH_FIFO=y

As said I have used the tc mirred configuration as it was packaged with previous vrnetlab versions <= 0.20.1.

I will apply this workouround until I fully understand why the clsact/flower configuration does not work.