linux-kernel - [PATCH bpf-next] selftests/bpf: Fix compile error when MPTCP not support

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Message-Id: <20241030100108.2443371-1-chen.dylane@gmail.com>
Date: Wed, 30 Oct 2024 18:01:08 +0800
From: Tao Chen <chen.dylane@...il.com>
To: Matthieu Baerts <matttbe@...nel.org>,
	Mat Martineau <martineau@...nel.org>,
	Geliang Tang <geliang@...nel.org>,
	Andrii Nakryiko <andrii@...nel.org>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	Yonghong Song <yonghong.song@...ux.dev>,
	Jiri Olsa <jolsa@...nel.org>
Cc: bpf@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
	mptcp@...ts.linux.dev,
	Tao Chen <chen.dylane@...il.com>
Subject: [PATCH bpf-next] selftests/bpf: Fix compile error when MPTCP not support

Fix compile error when MPTCP feature not support, though eBPF core check
already done which seems invalid in this situation, the error info like:
progs/mptcp_sock.c:49:40: error: no member named 'is_mptcp' in 'struct
tcp_sock'
   49 |         is_mptcp = bpf_core_field_exists(tsk->is_mptcp) ?

The filed created in new definitions with eBPF core feature to solve
this build problem, and test case result still ok in MPTCP kernel.

176/1   mptcp/base:OK
176/2   mptcp/mptcpify:OK
176     mptcp:OK
Summary: 1/2 PASSED, 0 SKIPPED, 0 FAILED

Fixes: 8039d353217c ("selftests/bpf: Add MPTCP test base")
Signed-off-by: Tao Chen <chen.dylane@...il.com>
---
 .../testing/selftests/bpf/progs/mptcp_sock.c  | 42 ++++++++++++++-----
 1 file changed, 32 insertions(+), 10 deletions(-)

diff --git a/tools/testing/selftests/bpf/progs/mptcp_sock.c b/tools/testing/selftests/bpf/progs/mptcp_sock.c
index f3acb90588c7..2f80d042686a 100644
--- a/tools/testing/selftests/bpf/progs/mptcp_sock.c
+++ b/tools/testing/selftests/bpf/progs/mptcp_sock.c
@@ -25,13 +25,23 @@ struct {
 	__type(value, struct mptcp_storage);
 } socket_storage_map SEC(".maps");
 
+struct tcp_sock___new {
+	bool is_mptcp;
+} __attribute__((preserve_access_index));
+
+struct mptcp_sock___new {
+	__u32 token;
+	struct sock *first;
+	char ca_name[TCP_CA_NAME_MAX];
+} __attribute__((preserve_access_index));
+
 SEC("sockops")
 int _sockops(struct bpf_sock_ops *ctx)
 {
 	struct mptcp_storage *storage;
-	struct mptcp_sock *msk;
+	struct mptcp_sock___new *msk;
 	int op = (int)ctx->op;
-	struct tcp_sock *tsk;
+	struct tcp_sock___new *tsk;
 	struct bpf_sock *sk;
 	bool is_mptcp;
 
@@ -42,11 +52,16 @@ int _sockops(struct bpf_sock_ops *ctx)
 	if (!sk)
 		return 1;
 
-	tsk = bpf_skc_to_tcp_sock(sk);
+	/* recast pointer to capture new type for compiler */
+	tsk = (void *)bpf_skc_to_tcp_sock(sk);
 	if (!tsk)
 		return 1;
 
-	is_mptcp = bpf_core_field_exists(tsk->is_mptcp) ? tsk->is_mptcp : 0;
+	if (bpf_core_field_exists(tsk->is_mptcp))
+		is_mptcp = BPF_CORE_READ(tsk, is_mptcp);
+	else
+		is_mptcp = 0;
+
 	if (!is_mptcp) {
 		storage = bpf_sk_storage_get(&socket_storage_map, sk, 0,
 					     BPF_SK_STORAGE_GET_F_CREATE);
@@ -57,7 +72,7 @@ int _sockops(struct bpf_sock_ops *ctx)
 		__builtin_memset(storage->ca_name, 0, TCP_CA_NAME_MAX);
 		storage->first = NULL;
 	} else {
-		msk = bpf_skc_to_mptcp_sock(sk);
+		msk = (void *)bpf_skc_to_mptcp_sock(sk);
 		if (!msk)
 			return 1;
 
@@ -66,9 +81,9 @@ int _sockops(struct bpf_sock_ops *ctx)
 		if (!storage)
 			return 1;
 
-		storage->token = msk->token;
-		__builtin_memcpy(storage->ca_name, msk->ca_name, TCP_CA_NAME_MAX);
-		storage->first = msk->first;
+		storage->token = BPF_CORE_READ(msk, token);
+		BPF_CORE_READ_STR_INTO(&storage->ca_name, msk, ca_name);
+		storage->first = BPF_CORE_READ(msk, first);
 	}
 	storage->invoked++;
 	storage->is_mptcp = is_mptcp;
@@ -81,8 +96,15 @@ SEC("fentry/mptcp_pm_new_connection")
 int BPF_PROG(trace_mptcp_pm_new_connection, struct mptcp_sock *msk,
 	     const struct sock *ssk, int server_side)
 {
-	if (!server_side)
-		token = msk->token;
+	struct mptcp_sock___new *mskw;
+
+	if (!server_side) {
+		mskw = (void *)msk;
+		if (bpf_core_field_exists(mskw->token))
+			token = BPF_CORE_READ(mskw, token);
+		else
+			token = 0;
+	}
 
 	return 0;
 }
-- 
2.43.0