[RFC PATCH bpf-next v4 0/7] Implement bpf queue/stack maps

[Mauricio Vasquez B <mauricio.vasquez@polito.it>]

In some applications this is needed have a pool of free elements, for
example the list of free L4 ports in a SNAT.  None of the current maps allow
to do it as it is not possible to get any element without having they key
it is associated to.

This patchset implements two new kind of eBPF maps: queue and stack.
Those maps provide to eBPF programs the peek, push and pop operations, and for
userspace applications a new bpf_map_lookup_and_delete_elem() is added.

Signed-off-by: Mauricio Vasquez B <mauricio.vasquez@polito.it>

v3 -> v4:
 - Revert renaming of kernel/bpf/stackmap.c
 - Remove restriction on value size
 - Remove len arguments from peek/pop helpers
 - Add new ARG_PTR_TO_UNINIT_MAP_VALUE

v2 -> v3:
 - Return elements by value instead that by reference
 - Implement queue/stack base on array and head + tail indexes
 - Rename stack trace related files to avoid confusion and conflicts

v1 -> v2:
 - Create two separate maps instead of single one + flags
 - Implement bpf_map_lookup_and_delete syscall
 - Support peek operation
 - Define replacement policy through flags in the update() method
 - Add eBPF side tests

---

Mauricio Vasquez B (7):
      bpf: rename stack trace map operations
      bpf/syscall: allow key to be null in map functions
      bpf: add MAP_LOOKUP_AND_DELETE_ELEM syscall
      bpf: add bpf queue and stack maps
      bpf: restrict use of peek/push/pop
      Sync uapi/bpf.h to tools/include
      selftests/bpf: add test cases for queue and stack maps


 include/linux/bpf.h                                |    8 +
 include/linux/bpf_types.h                          |    4 
 include/uapi/linux/bpf.h                           |   36 ++
 kernel/bpf/Makefile                                |    2 
 kernel/bpf/core.c                                  |    3 
 kernel/bpf/helpers.c                               |   43 +++
 kernel/bpf/queue_stack_maps.c                      |  300 ++++++++++++++++++++
 kernel/bpf/stackmap.c                              |    2 
 kernel/bpf/syscall.c                               |  112 +++++++
 kernel/bpf/verifier.c                              |   28 ++
 net/core/filter.c                                  |    6 
 tools/include/uapi/linux/bpf.h                     |   36 ++
 tools/lib/bpf/bpf.c                                |   12 +
 tools/lib/bpf/bpf.h                                |    1 
 tools/testing/selftests/bpf/Makefile               |    6 
 tools/testing/selftests/bpf/bpf_helpers.h          |    7 
 tools/testing/selftests/bpf/test_maps.c            |  122 ++++++++
 tools/testing/selftests/bpf/test_progs.c           |   99 +++++++
 tools/testing/selftests/bpf/test_queue_map.c       |    4 
 tools/testing/selftests/bpf/test_queue_stack_map.h |   59 ++++
 tools/testing/selftests/bpf/test_stack_map.c       |    4 
 21 files changed, 874 insertions(+), 20 deletions(-)
 create mode 100644 kernel/bpf/queue_stack_maps.c
 create mode 100644 tools/testing/selftests/bpf/test_queue_map.c
 create mode 100644 tools/testing/selftests/bpf/test_queue_stack_map.h
 create mode 100644 tools/testing/selftests/bpf/test_stack_map.c