Merge branch 'selftests/bpf: Add sockaddr tests for kernel networking'

Jordan Rife says:

====================
This patch series adds test coverage for BPF sockaddr hooks and their
interactions with kernel socket functions (i.e. kernel_bind(),
kernel_connect(), kernel_sendmsg(), sock_sendmsg(),
kernel_getpeername(), and kernel_getsockname()) while also rounding out
IPv4 and IPv6 sockaddr hook coverage in prog_tests/sock_addr.c.

As with v1 of this patch series, we add regression coverage for the
issues addressed by these patches,

- commit 0bdf399342c5("net: Avoid address overwrite in kernel_connect")
- commit 86a7e0b69bd5("net: prevent rewrite of msg_name in sock_sendmsg()")
- commit c889a99a21bf("net: prevent address rewrite in kernel_bind()")
- commit 01b2885d9415("net: Save and restore msg_namelen in sock_sendmsg")

but broaden the focus a bit.

In order to extend prog_tests/sock_addr.c to test these kernel
functions, we add a set of new kfuncs that wrap individual socket
operations to bpf_testmod and invoke them through set of corresponding
SYSCALL programs (progs/sock_addr_kern.c). Each test case can be
configured to use a different set of "sock_ops" depending on whether it
is testing kernel calls (kernel_bind(), kernel_connect(), etc.) or
system calls (bind(), connect(), etc.).

=======
Patches
=======
* Patch 1 fixes the sock_addr bind test program to work for big endian
  architectures such as s390x.
* Patch 2 introduces the new kfuncs to bpf_testmod.
* Patch 3 introduces the BPF program which allows us to invoke these
  kfuncs invividually from the test program.
* Patch 4 lays the groundwork for IPv4 and IPv6 sockaddr hook coverage
  by migrating much of the environment setup logic from
  bpf/test_sock_addr.sh into prog_tests/sock_addr.c and moves test cases
  to cover bind4/6, connect4/6, sendmsg4/6 and recvmsg4/6 hooks.
* Patch 5 makes the set of socket operations for each test case
  configurable, laying the groundwork for Patch 6.
* Patch 6 introduces two sets of sock_ops that invoke the kernel
  equivalents of connect(), bind(), etc. and uses these to add coverage
  for the kernel socket functions.

=======
Changes
=======
v2->v3
------
* Renamed bind helpers. Dropped "_ntoh" suffix.
* Added guards to kfuncs to make sure addrlen and msglen do not exceed
  the buffer capacity.
* Added KF_SLEEPABLE flag to kfuncs.
* Added a mutex (sock_lock) to kfuncs to serialize access to sock.
* Added NULL check for sock to each kfunc.
* Use the "sock_addr" networking namespace for all network interface
  setup and testing.
* Use "nodad" when calling "ip -6 addr add" during interface setup to
  avoid delays and remove ping loop.
* Removed test cases from test_sock_addr.c to make it clear what remains
  to be migrated.
* Removed unused parameter (expect_change) from sock_addr_op().

Link: https://lore.kernel.org/bpf/20240412165230.2009746-1-jrife@google.com/T/#u
v1->v2
------
* Dropped test_progs/sock_addr_kern.c and the sock_addr_kern test module
  in favor of simply expanding bpf_testmod and test_progs/sock_addr.c.
* Migrated environment setup logic from bpf/test_sock_addr.sh into
  prog_tests/sock_addr.c rather than invoking the script from the test
  program.
* Added kfuncs to bpf_testmod as well as the sock_addr_kern BPF program
  to enable us to invoke kernel socket functions from
  test_progs/sock_addr.c.
* Added test coverage for kernel socket functions to
  test_progs/sock_addr.c.

Link: https://lore.kernel.org/bpf/20240329191907.1808635-1-jrife@google.com/T/#u
====================

Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>