Kuniyuki Iwashima wrote:

The test creates client and server sockets and sets INT_MAX to the
server's SO_RCVBUFFORCE.

Then, the client floods packets to the server until the UDP memory
usage reaches (INT_MAX + 1) >> PAGE_SHIFT.

Finally, both sockets are close()d, and the last assert makes sure
that the memory usage drops to 0.

If needed, we can extend the test later for other protocols.

Without patch 1:

  # Starting 2 tests from 2 test cases.
  #  RUN           so_rcvbuf.udp_ipv4.rmem_max ...
  # so_rcvbuf.c:163:rmem_max:Expected pages (524800) <= *variant->max_pages (524288)
  # rmem_max: Test terminated by assertion
  #          FAIL  so_rcvbuf.udp_ipv4.rmem_max
  not ok 1 so_rcvbuf.udp_ipv4.rmem_max

Without patch 2:

  #  RUN           so_rcvbuf.udp_ipv4.rmem_max ...
  # so_rcvbuf.c:170:rmem_max:max_pages: 524288
  # so_rcvbuf.c:178:rmem_max:Expected get_prot_pages(_metadata, variant) (524288) == 0 (0)
  # rmem_max: Test terminated by assertion
  #          FAIL  so_rcvbuf.udp_ipv4.rmem_max
  not ok 1 so_rcvbuf.udp_ipv4.rmem_max

Signed-off-by: Kuniyuki Iwashima <redacted>

Reviewed-by: Willem de Bruijn <willemb@google.com>