Merge branch 'selftests/bpf: xsk improvements and new stats'

Ciara Loftus says:

====================

This series attempts to improve the xsk selftest framework by:
1. making the default output less verbose
2. adding an optional verbose flag to both the test_xsk.sh script and xdpxceiver app.
3. renaming the debug option in the app to to 'dump-pkts' and add a flag to the test_xsk.sh
script which enables the flag in the app.
4. changing how tests are launched - now they are launched from the xdpxceiver app
instead of the script.

Once the improvements are made, a new set of tests are added which test the xsk
statistics.

The output of the test script now looks like:

./test_xsk.sh
PREREQUISITES: [ PASS ]
1..10
ok 1 PASS: SKB NOPOLL
ok 2 PASS: SKB POLL
ok 3 PASS: SKB NOPOLL Socket Teardown
ok 4 PASS: SKB NOPOLL Bi-directional Sockets
ok 5 PASS: SKB NOPOLL Stats
ok 6 PASS: DRV NOPOLL
ok 7 PASS: DRV POLL
ok 8 PASS: DRV NOPOLL Socket Teardown
ok 9 PASS: DRV NOPOLL Bi-directional Sockets
ok 10 PASS: DRV NOPOLL Stats
# Totals: pass:10 fail:0 xfail:0 xpass:0 skip:0 error:0
XSK KSELFTESTS: [ PASS ]

v2->v3:
* Rename dump-pkts to dump_pkts in test_xsk.sh
* Add examples of flag usage to test_xsk.sh

v1->v2:
* Changed '-d' flag in the shell script to '-D' to be consistent with the xdpxceiver app.
* Renamed debug mode to 'dump-pkts' which better reflects the behaviour.
* Use libpf APIs instead of calls to ss for configuring xdp on the links
* Remove mutex init & destroy for each stats test
* Added a description for each of the new statistics tests
* Distinguish between exiting due to initialisation failure vs test failure

This series applies on commit d310ec03

Ciara Loftus (3):
  selftests/bpf: expose and rename debug argument
  selftests/bpf: restructure xsk selftests
  selftests/bpf: introduce xsk statistics tests
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>