selftest: Clean-up and stabilize mirroring tests

The mirroring selftests work by sending ICMP traffic between two hosts. Along the way, this traffic is mirrored to a gretap netdevice, and counter taps are then installed strategically along the path of the mirrored traffic to verify the mirroring took place.

The problem with this is that besides mirroring the primary traffic, any other service traffic is mirrored as well. At the same time, because the tests need to work in HW-offloaded scenarios, the ability of the device to do arbitrary packet inspection should not be taken for granted. Most tests therefore simply use matchall, one uses flower to match on IP address. As a result, the selftests are noisy.

mirror_test() accommodated this noisiness by giving the counters an allowance of several packets. But that only works up to a point, and on busy systems won't be always enough.

In this patch set, clean up and stabilize the mirroring selftests. The original intention was to port the tests over to UDP, but the logic of ICMP ends up being so entangled in the mirroring selftests that the changes feel overly invasive. Instead, ICMP is kept, but where possible, we match on ICMP message type, thus filtering out hits by other ICMP messages.

Where this is not practical (where the counter tap is put on a device that carries encapsulated packets), switch the counter condition to _at least_ X observed packets. This is less robust, but barely so -- probably the only scenario that this would not catch is something like erroneous packet duplication, which would hopefully get caught by the numerous other tests in this extensive suite.

- Patches #1 to #3 clean up parameters at various helpers.

- Patches #4 to #6 stabilize the mirroring selftests as described above.

- Mirroring tests currently allow testing SW datapath even on HW netdevices by trapping traffic to the SW datapath. This complicates the tests a bit without a good reason: to test SW datapath, just run the selftests on the veth topology. Thus in patch #7, drop support for this dual SW/HW testing.

- At this point, some cleanups were either made possible by the previous patches, or were always possible. In patches #8 to #11, realize these cleanups.

- In patch #12, fix mlxsw mirror_gre selftest to respect setting TESTS.

Petr Machata (12):
selftests: libs: Expand "$@" where possible
selftests: mirror: Drop direction argument from several functions
selftests: lib: tc_rule_stats_get(): Move default to argument
definition
selftests: mirror_gre_lag_lacp: Check counters at tunnel
selftests: mirror: do_test_span_dir_ips(): Install accurate taps
selftests: mirror: mirror_test(): Allow exact count of packets
selftests: mirror: Drop dual SW/HW testing
selftests: mlxsw: mirror_gre: Simplify
selftests: mirror_gre_lag_lacp: Drop unnecessary code
selftests: libs: Drop slow_path_trap_install()/_uninstall()
selftests: libs: Drop unused functions
selftests: mlxsw: mirror_gre: Obey TESTS

 .../selftests/drivers/net/mlxsw/mirror_gre.sh | 71 ++++++---------
 .../drivers/net/mlxsw/mirror_gre_scale.sh     | 18 +---
 tools/testing/selftests/net/forwarding/lib.sh | 83 +++++++++++------
 .../selftests/net/forwarding/mirror_gre.sh    | 45 +++-------
 .../net/forwarding/mirror_gre_bound.sh        | 23 +----
 .../net/forwarding/mirror_gre_bridge_1d.sh    | 21 +----
 .../forwarding/mirror_gre_bridge_1d_vlan.sh   | 21 +----
 .../net/forwarding/mirror_gre_bridge_1q.sh    | 21 +----
 .../forwarding/mirror_gre_bridge_1q_lag.sh    | 29 ++----
 .../net/forwarding/mirror_gre_changes.sh      | 73 ++++++---------
 .../net/forwarding/mirror_gre_flower.sh       | 43 ++++-----
 .../net/forwarding/mirror_gre_lag_lacp.sh     | 65 ++++++--------
 .../net/forwarding/mirror_gre_lib.sh          | 90 ++++++++++++++-----
 .../net/forwarding/mirror_gre_neigh.sh        | 39 +++-----
 .../selftests/net/forwarding/mirror_gre_nh.sh | 35 ++------
 .../net/forwarding/mirror_gre_vlan.sh         | 21 +----
 .../forwarding/mirror_gre_vlan_bridge_1q.sh   | 69 ++++++--------
 .../selftests/net/forwarding/mirror_lib.sh    | 79 +++++++++++-----
 .../selftests/net/forwarding/mirror_vlan.sh   | 43 +++------
 tools/testing/selftests/net/lib.sh            |  4 +-
 20 files changed, 355 insertions(+), 538 deletions(-)

2.45.0