Bug#1032561: iproute2: "tc filter show" always results in empty response

[Simon]

Package: iproute2
Version: 6.1.0-2
Severity: normal
X-Debbugs-Cc: si...@sarthur.dev

Dear Maintainer,

While testing CAKE traffic shaping, I could not see records or statistics for applied tc filters.
Filters do seem to be present and having an effect, but "tc filter show" always returns no output.

root@debian12:~# tc filter add dev eth2 parent ffff: matchall action mirred egress redirect dev ifb4eth2
root@debian12:~# tc filter
root@debian12:~# tc filter show
root@debian12:~#

Tested on fresh Bookworm install and several other machines running various 6.1 based kernels with same result.

-- System Information:
Debian Release: bookworm/sid
APT prefers testing
APT policy: (500, 'testing')
Architecture: amd64 (x86_64)

Kernel: Linux 6.1.0-5-amd64 (SMP w/1 CPU thread; PREEMPT)
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8), LANGUAGE=en_GB:en
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages iproute2 depends on:
ii debconf [debconf-2.0] 1.5.82
ii libbpf1 1:1.1.0-1
ii libbsd0 0.11.7-2
ii libc6 2.36-8
ii libcap2 1:2.66-3
ii libcap2-bin 1:2.66-3
ii libdb5.3 5.3.28+dfsg2-1
ii libelf1 0.188-2.1
ii libmnl0 1.0.4-3
ii libselinux1 3.4-1+b5
ii libtirpc3 1.3.3+ds-1
ii libxtables12 1.8.9-2

Versions of packages iproute2 recommends:
pn libatm1 <none>

Versions of packages iproute2 suggests:
pn iproute2-doc <none>
ii python3 3.11.2-1

-- debconf information:
iproute2/setcaps: false

[Simon Arthur]

I have found that more specific arguments does return output:

root@debian12:~# tc filter show

root@debian12:~# tc filter show dev eth2 root
filter parent ffff: protocol all pref 49152 matchall chain 0
filter parent ffff: protocol all pref 49152 matchall chain 0 handle 0x1
  not_in_hw
        action order 1: mirred (Egress Redirect to device ifb4eth2) stolen
        index 2 ref 1 bind 1

However like "tc qdisc show" you would expect "tc filter show" to also result in all filter rules across interfaces being returned.