This patch exports the member last_snd of struct mptcp_sock in
bpf_mptcp_helpers.h, and adds BPF write access to it.

Signed-off-by: Geliang Tang <geliang.tang@suse.com>
---
 net/mptcp/bpf.c                                 | 16 ++++++++++++++++
 tools/testing/selftests/bpf/bpf_mptcp_helpers.h |  1 +
 2 files changed, 17 insertions(+)

diff --git a/net/mptcp/bpf.c b/net/mptcp/bpf.c
index e849fc3fb6c5..bd3c50b07ab2 100644
--- a/net/mptcp/bpf.c
+++ b/net/mptcp/bpf.c
@@ -40,6 +40,7 @@ static int bpf_mptcp_sched_btf_struct_access(struct bpf_verifier_log *log,
 {
 	const struct btf_type *state;
 	u32 type_id;
+	size_t end;
 
 	if (atype == BPF_READ)
 		return btf_struct_access(log, btf, t, off, size, atype,
@@ -55,6 +56,21 @@ static int bpf_mptcp_sched_btf_struct_access(struct bpf_verifier_log *log,
 		return -EACCES;
 	}
 
+	switch (off) {
+	case offsetof(struct mptcp_sock, last_snd):
+		end = offsetofend(struct mptcp_sock, last_snd);
+		break;
+	default:
+		bpf_log(log, "no write support to mptcp_sock at off %d\n", off);
+		return -EACCES;
+	}
+
+	if (off + size > end) {
+		bpf_log(log, "access beyond mptcp_sock at off %u size %u ended at %lu",
+			off, size, end);
+		return -EACCES;
+	}
+
 	return NOT_INIT;
 }
 
diff --git a/tools/testing/selftests/bpf/bpf_mptcp_helpers.h b/tools/testing/selftests/bpf/bpf_mptcp_helpers.h
index 5135eb6710e8..990ccd2b6e96 100644
--- a/tools/testing/selftests/bpf/bpf_mptcp_helpers.h
+++ b/tools/testing/selftests/bpf/bpf_mptcp_helpers.h
@@ -9,6 +9,7 @@
 struct mptcp_sock {
 	struct inet_connection_sock	sk;
 
+	struct sock	*last_snd;
 	__u32		token;
 	struct sock	*first;
 	char		ca_name[TCP_CA_NAME_MAX];
-- 
2.34.1