This patch adds a test program for the newly added mptcp_address bpf_iter
in SEC "cgroup/getsockopt". This test iterates over all address entries on
the local address list of userspace PM and check whether each one is an
IPv4mapped address.

Export mptcp_address helpers bpf_iter_mptcp_address_new/_next/_destroy into
bpf_experimental.h. Use bpf_mptcp_sock_acquire() to acquire the msk, then
lock the msk pm lock and use bpf_for_each(mptcp_address) to walk the local
address list of this msk. Invoke bpf_ipv6_addr_v4mapped() in the loop to
check whether the address is an IPv4mapped one. Then Add the address ID of
each entry to local veriable local_ids.

Out of the loop, unlock the msk pm lock and use bpf_mptcp_sock_release() to
release the msk. Finally, assign local_ids to global variable ids so that
the application can obtain this value.

Add a subtest named test_iters_address to load and verify the newly added
mptcp_address type bpf_iter example in test_mptcp.

Since mptcp_address bpf_iter iterates over all address entries on the
local address list of userspace PM. A set of userspace PM helpers are
added.

Set pm_type and start "pm_nl_ctl events" command to save pm events into
the log file /tmp/bpf_userspace_pm_events in userspace_pm_init(). Kill
"pm_nl_ctl" command and remove the log file in userspace_pm_cleanup().
Parse the log file in userspace_pm_add_subflow() to get the token, sport
and dport values, then use "pm_nl_ctl csf" command to create a subflow.

Use the helper userspace_pm_add_subflow() to add 3 new subflow endpoints.
Send a byte of message to start the mptcp connection, and receive the
message.

getsockopt() is invoked to trigger the "cgroup/getsockopt" test program.
Check if skel->bss->ids equals 60 to verify whether the program loops
three times as expected.

Signed-off-by: Geliang Tang <[email protected]>
Message-Id: <7646544aba9fe416676a1ab913232d08ba26a585.1729582332.git.tanggeliang@kylinos.cn>