RE: [PATCH bpf-next 3/3] selftests/bpf: Test unhashing kTLS socket after removing from map

Jakub Sitnicki wrote:

When a TCP socket gets inserted into a sockmap, its sk_prot callbacks get
replaced with tcp_bpf callbacks built from regular tcp callbacks. If TLS
gets enabled on the same socket, sk_prot callbacks get replaced once again,
this time with kTLS callbacks built from tcp_bpf callbacks.

Now, we allow removing a socket from a sockmap that has kTLS enabled. After
removal, socket remains with kTLS configured. This is where things things
get tricky.

Since the socket has a set of sk_prot callbacks that are a mix of kTLS and
tcp_bpf callbacks, we need to restore just the tcp_bpf callbacks to the
original ones. At the moment, it comes down to the the unhash operation.

We had a regression recently because tcp_bpf callbacks were not cleared in
this particular scenario of removing a kTLS socket from a sockmap. It got
fixed in commit 4da6a196f93b ("bpf: Sockmap/tls, during free we may call
tcp_bpf_unhash() in loop").

Add a test that triggers the regression so that we don't reintroduce it in
the future.

Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
---
 .../selftests/bpf/prog_tests/sockmap_ktls.c   | 123 ++++++++++++++++++
 1 file changed, 123 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/sockmap_ktls.c

I'll push the patches I have on my stack to run some more of the
sockmap tests with ktls this week as well to get our coverage up.

Acked-by: John Fastabend <john.fastabend@gmail.com>