Re: [PATCH net] selftests: net: add missing required classifier

[Paolo Abeni <pabeni@redhat.com>]

On Thu, 2024-01-25 at 09:48 +0100, Eric Dumazet wrote:
> On Thu, Jan 25, 2024 at 9:23 AM Paolo Abeni <pabeni@redhat.com> wrote:
> > 
> > the udpgro_fraglist self-test uses the BPF classifiers, but the
> > current net self-test configuration does not include it, causing
> > CI failures:
> > 
> >  # selftests: net: udpgro_frglist.sh
> >  # ipv6
> >  # tcp - over veth touching data
> >  # -l 4 -6 -D 2001:db8::1 -t rx -4 -t
> >  # 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
> > 
> > Add the missing knob.
> > 
> > Fixes: edae34a3ed92 ("selftests net: add UDP GRO fraglist + bpf self-tests")
> > Signed-off-by: Paolo Abeni <pabeni@redhat.com>
> 
> FYI, while looking at the gro test, I found that using strace was
> making it failing as well.

It looks like the gro.sh (large) tests send the to-be-aggregate
segments individually and relay on the gro flush timeout being large
enough to fit all the relevant write operations. I suspect/hope
something alike:

---
diff --git a/tools/testing/selftests/net/setup_veth.sh b/tools/testing/selftests/net/setup_veth.sh
index a9a1759e035c..1f78a87f6f37 100644
--- a/tools/testing/selftests/net/setup_veth.sh
+++ b/tools/testing/selftests/net/setup_veth.sh
@@ -11,7 +11,7 @@ setup_veth_ns() {
        local -r ns_mac="$4"
 
        [[ -e /var/run/netns/"${ns_name}" ]] || ip netns add "${ns_name}"
-       echo 100000 > "/sys/class/net/${ns_dev}/gro_flush_timeout"
+       echo 1000000 > "/sys/class/net/${ns_dev}/gro_flush_timeout"
        ip link set dev "${ns_dev}" netns "${ns_name}" mtu 65535
        ip -netns "${ns_name}" link set dev "${ns_dev}" up
--- 
should solve the sporadic issues.

> Not sure about this one...

All the udpgro* test should write a single UDP GSO packet and let the
veth segmenting it, hopefully slowing down either ends should not
impact them - but I did not check yet!

Perhaps even the gro.sh tests could be modified alike?

Cheers,

Paolo