The get_next_frame() function in psock_tpacket.c was missing a return
statement in its default switch case, leading to a compiler warning.

This was caused by a `bug_on(1)` call, which is defined as an
`assert()`, being compiled out because NDEBUG is defined during the
build.

Instead of adding a `return NULL;` which would silently hide the error
and could lead to crashes later, this change restores the original
author's intent. By adding `#undef NDEBUG` before including <assert.h>,
we ensure the assertion is active and will cause the test to abort if
this unreachable code is ever executed.

Signed-off-by: Wake Liu <wakel@google.com>
---
 tools/testing/selftests/net/psock_tpacket.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/testing/selftests/net/psock_tpacket.c b/tools/testing/selftests/net/psock_tpacket.c
index 0dd909e325d9..2938045c5cf9 100644
--- a/tools/testing/selftests/net/psock_tpacket.c
+++ b/tools/testing/selftests/net/psock_tpacket.c
@@ -22,6 +22,7 @@
  *   - TPACKET_V3: RX_RING
  */
 
+#undef NDEBUG
 #include <stdio.h>
 #include <stdlib.h>
 #include <sys/types.h>
-- 
2.50.1.703.g449372360f-goog