Squash to "selftests/bpf: Add mptcp_subflow bpf_iter subtest"

Use bpf_core_cast() instead of bpf_skc_to_mptcp_sock().
Change the 2nd parameter type of bpf_for_each() as 'struct sock'.
Drop use of bpf_mptcp_sock_acquire/release.
Drop declaration of bpf_mptcp_subflow_tcp_sock. It's no longer used.
Update the comment for mptcp_subflow_tcp_sock(), which is a BPF helper,
not a kfunc.

Please update the commit log as:

'''
This patch adds a "cgroup/getsockopt" program "iters_subflow" to test the
newly added mptcp_subflow bpf_iter.

Export mptcp_subflow helpers bpf_iter_mptcp_subflow_new/_next/_destroy
and other helpers into bpf_experimental.h.

Use bpf_for_each() to walk the subflow list of this msk. MPTCP-specific
packet scheduler kfunc can be called in the loop. In this test, just
add all subflow ids to local variable local_ids, then invoke the helper
mptcp_subflow_tcp_sock() in the loop to pick a subsocket.

Out of the loop, use bpf_mptcp_subflow_ctx() to get the subflow context
of the picked subsocket and do some verification. Finally, assign
local_ids to global variable ids so that the application can obtain this
value.

Add a subtest named test_iters_subflow to load and verify the newly added
mptcp_subflow type bpf_iter example in test_mptcp. Use the helper
endpoint_init() to add 3 new subflow endpoints. Send a byte of message
to start the mptcp connection, and wait for new subflows to be added.
getsockopt() is invoked to trigger the "cgroup/getsockopt" test program
"iters_subflow". Check if skel->bss->ids equals 10 to verify whether this
mptcp_subflow bpf_iter loops correctly as expected.
'''

Signed-off-by: Geliang Tang <[email protected]>

Author: Geliang Tang

tools/testing/selftests/bpf/bpf_experimental.h

@@ -577,7 +577,7 @@ extern void bpf_iter_css_destroy(struct bpf_iter_css *it) __weak __ksym;
 
 struct bpf_iter_mptcp_subflow;
 extern int bpf_iter_mptcp_subflow_new(struct bpf_iter_mptcp_subflow *it,
-				      struct mptcp_sock *msk) __weak __ksym;
+				      struct sock *sk) __weak __ksym;
 extern struct mptcp_subflow_context *
 bpf_iter_mptcp_subflow_next(struct bpf_iter_mptcp_subflow *it) __weak __ksym;
 extern void

tools/testing/selftests/bpf/progs/mptcp_bpf.h

@@ -43,13 +43,8 @@ mptcp_subflow_tcp_sock(const struct mptcp_subflow_context *subflow)
 }
 
 /* ksym */
-extern struct mptcp_sock *bpf_mptcp_sock_acquire(struct mptcp_sock *msk) __ksym;
-extern void bpf_mptcp_sock_release(struct mptcp_sock *msk) __ksym;
-
 extern struct mptcp_subflow_context *
 bpf_mptcp_subflow_ctx(const struct sock *sk) __ksym;
-extern struct sock *
-bpf_mptcp_subflow_tcp_sock(const struct mptcp_subflow_context *subflow) __ksym;
 
 extern void mptcp_subflow_set_scheduled(struct mptcp_subflow_context *subflow,
 					bool scheduled) __ksym;

tools/testing/selftests/bpf/progs/mptcp_bpf_iters.c

@@ -28,18 +28,15 @@ int iters_subflow(struct bpf_sockopt *ctx)
 	if (!msk || msk->pm.server_side || !msk->pm.subflows)
 		return 1;
 
-	msk = bpf_mptcp_sock_acquire(msk);
-	if (!msk)
-		return 1;
-	bpf_for_each(mptcp_subflow, subflow, msk) {
+	bpf_for_each(mptcp_subflow, subflow, (struct sock *)sk) {
 		/* Here MPTCP-specific packet scheduler kfunc can be called:
 		 * this test is not doing anything really useful, only to
 		 * verify the iteration works.
 		 */
 
 		local_ids += subflow->subflow_id;
 
-		/* only to check the following kfunc works */
+		/* only to check the following helper works */
 		ssk = mptcp_subflow_tcp_sock(subflow);
 	}
 
@@ -58,6 +55,5 @@ int iters_subflow(struct bpf_sockopt *ctx)
 	ids = local_ids;
 
 out:
-	bpf_mptcp_sock_release(msk);
 	return 1;
 }