selftests: xsk: Add test case for packets at end of UMEM

Add test case to testapp_invalid_desc for valid packets at the end of
the UMEM.
Signed-off-by: Kal Conley <kal.conley@dectris.com>
Acked-by: Magnus Karlsson <magnus.karlsson@intel.com>
Link: https://lore.kernel.org/r/20230403145047.33065-3-kal.conley@dectris.comSigned-off-by: Martin KaFai Lau <martin.lau@kernel.org>

tools/testing/selftests/bpf/xskxceiver.c

@@ -1662,6 +1662,8 @@ static void testapp_invalid_desc(struct test_spec *test)
 		{-2, PKT_SIZE, 0, false},
 		/* Packet too large */
 		{0x2000, XSK_UMEM__INVALID_FRAME_SIZE, 0, false},
+		/* Up to end of umem allowed */
+		{umem_size - PKT_SIZE, PKT_SIZE, 0, true},
 		/* After umem ends */
 		{umem_size, PKT_SIZE, 0, false},
 		/* Straddle the end of umem */
@@ -1675,16 +1677,17 @@ static void testapp_invalid_desc(struct test_spec *test)
 
 	if (test->ifobj_tx->umem->unaligned_mode) {
 		/* Crossing a page boundrary allowed */
-		pkts[6].valid = true;
+		pkts[7].valid = true;
 	}
 	if (test->ifobj_tx->umem->frame_size == XSK_UMEM__DEFAULT_FRAME_SIZE / 2) {
 		/* Crossing a 2K frame size boundrary not allowed */
-		pkts[7].valid = false;
+		pkts[8].valid = false;
 	}
 
 	if (test->ifobj_tx->shared_umem) {
 		pkts[4].addr += umem_size;
 		pkts[5].addr += umem_size;
+		pkts[6].addr += umem_size;
 	}
 
 	pkt_stream_generate_custom(test, pkts, ARRAY_SIZE(pkts));