Introduce a test that is supposed to verify the persistence of BPF
resources based on underlying bpf_link usage.

Test will:
1) create and bind two sockets on queue ids 0 and 1
2) run a traffic on queue ids 0
3) remove xsk sockets from queue 0 on both veth interfaces
4) run a traffic on queues ids 1

Running traffic successfully on qids 1 means that BPF resources were
not removed on step 3).

In order to make it work, change the command that creates veth pair to
have the 4 queue pairs by default.

Introduce the arrays of xsks and umems to ifobject struct but keep a
pointers to single entities, so rest of the logic around Rx/Tx can be
kept as-is.

For umem handling, double the size of mmapped space and split that
between the two sockets.

Rename also bidi_pass to a variable 'second_step' of a boolean type as
it's now used also for the test that is introduced here and it doesn't
have anything in common with bi-directional testing.

Drop opt_queue command line argument as it wasn't working before anyway.

Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
---
 tools/testing/selftests/bpf/test_xsk.sh  |   2 +-
 tools/testing/selftests/bpf/xdpxceiver.c | 179 +++++++++++++++++------
 tools/testing/selftests/bpf/xdpxceiver.h |   7 +-
 3 files changed, 138 insertions(+), 50 deletions(-)

diff --git a/tools/testing/selftests/bpf/test_xsk.sh b/tools/testing/selftests/bpf/test_xsk.sh
index 56d4474e2c83..2a00b8222475 100755
--- a/tools/testing/selftests/bpf/test_xsk.sh
+++ b/tools/testing/selftests/bpf/test_xsk.sh

@@ -107,7 +107,7 @@ setup_vethPairs() {
                echo "setting up ${VETH0}: namespace: ${NS0}"
        fi
        ip netns add ${NS1}
-       ip link add ${VETH0} type veth peer name ${VETH1}
+       ip link add ${VETH0} numtxqueues 4 numrxqueues 4 type veth peer name ${VETH1} numtxqueues 4 numrxqueues 4
        if [ -f /proc/net/if_inet6 ]; then
                echo 1 > /proc/sys/net/ipv6/conf/${VETH0}/disable_ipv6
        fi

diff --git a/tools/testing/selftests/bpf/xdpxceiver.c b/tools/testing/selftests/bpf/xdpxceiver.c
index aef5840e1c24..dc775ee139c5 100644
--- a/tools/testing/selftests/bpf/xdpxceiver.c
+++ b/tools/testing/selftests/bpf/xdpxceiver.c

@@ -41,8 +41,12 @@
  *            Reduce the size of the RX ring to a fraction of the fill ring size.
  *       iv.  fill queue empty
  *            Do not populate the fill queue and then try to receive pkts.
+ *    f. bpf_link resource persitence