selftests/bpf: Fix compiler warnings reported in -O2 mode

Fix a bunch of potentially unitialized variable usage warnings that are
reported by GCC in -O2 mode. Also silence overzealous stringop-truncation
class of warnings.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/bpf/20231006175744.3136675-1-andrii@kernel.org

selftests/bpf: Fix a CI failure caused by vsock write

While commit 90f0074cd9f9 ("selftests/bpf: fix a CI failure caused by vsock sockmap test")
fixes a receive failure of vsock sockmap test, there is still a write failure:

Error: #211/79 sockmap_listen/sockmap VSOCK test_vsock_redir
Error: #211/79 sockmap_listen/sockmap VSOCK test_vsock_redir
./test_progs:vsock_unix_redir_connectible:1501: egress: write: Transport endpoint is not connected
vsock_unix_redir_connectible:FAIL:1501
./test_progs:vsock_unix_redir_connectible:1501: ingress: write: Transport endpoint is not connected
vsock_unix_redir_connectible:FAIL:1501
./test_progs:vsock_unix_redir_connectible:1501: egress: write: Transport endpoint is not connected
vsock_unix_redir_connectible:FAIL:1501

The reason is that the vsock connection in the test is set to ESTABLISHED state
by function virtio_transport_recv_pkt, which is executed in a workqueue thread,
so when the user space test thread runs before the workqueue thread, this
problem occurs.

To fix it, before writing the connection, wait for it to be connected.

Fixes: d61bd8c1fd02 ("selftests/bpf: add a test case for vsock sockmap")
Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20230901031037.3314007-1-xukuohai@huaweicloud.com

bpf, sockmap: Build helper to create connected socket pair

A common operation for testing is to spin up a pair of sockets that are
connected. Then we can use these to run specific tests that need to
send data, check BPF programs and so on.

The sockmap_listen programs already have this logic lets move it into
the new sockmap_helpers header file for general use.

Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Link: https://lore.kernel.org/bpf/20230523025618.113937-11-john.fastabend@gmail.com

bpf, sockmap: Pull socket helpers out of listen test for general use

No functional change here we merely pull the helpers in sockmap_listen.c
into a header file so we can use these in other programs. The tests we
are about to add aren't really _listen tests so doesn't make sense
to add them here.

Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Link: https://lore.kernel.org/bpf/20230523025618.113937-10-john.fastabend@gmail.com