selftests: bpf: verify first of struct mptcp_sock

This patch verifies the 'first' struct member of struct mptcp_sock, which
points to the first subflow of msk. Save 'sk' in mptcp_storage, and verify
it with 'first' in verify_msk().

Acked-by: Matthieu Baerts <[email protected]>
Signed-off-by: Geliang Tang <[email protected]>
Signed-off-by: Mat Martineau <[email protected]>

Author: geliangtang

tools/testing/selftests/bpf/bpf_mptcp_helpers.h

@@ -10,6 +10,7 @@ struct mptcp_sock {
 	struct inet_connection_sock	sk;
 
 	__u32		token;
+	struct sock	*first;
 	char		ca_name[TCP_CA_NAME_MAX];
 } __attribute__((preserve_access_index));
 

tools/testing/selftests/bpf/prog_tests/mptcp.c

@@ -12,7 +12,9 @@
 struct mptcp_storage {
 	__u32 invoked;
 	__u32 is_mptcp;
+	struct sock *sk;
 	__u32 token;
+	struct sock *first;
 	char ca_name[TCP_CA_NAME_MAX];
 };
 
@@ -133,6 +135,12 @@ static int verify_msk(int map_fd, int client_fd)
 		err++;
 	}
 
+	if (val.first != val.sk) {
+		log_err("Unexpected mptcp_sock.first %p != %p",
+			val.first, val.sk);
+		err++;
+	}
+
 	if (strncmp(val.ca_name, ca_name, TCP_CA_NAME_MAX)) {
 		log_err("Unexpected mptcp_sock.ca_name %s != %s",
 			val.ca_name, ca_name);

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

@@ -12,7 +12,9 @@ __u32 _version SEC("version") = 1;
 struct mptcp_storage {
 	__u32 invoked;
 	__u32 is_mptcp;
+	struct sock *sk;
 	__u32 token;
+	struct sock *first;
 	char ca_name[TCP_CA_NAME_MAX];
 };
 
@@ -51,6 +53,7 @@ int _sockops(struct bpf_sock_ops *ctx)
 
 		storage->token = 0;
 		bzero(storage->ca_name, TCP_CA_NAME_MAX);
+		storage->first = NULL;
 	} else {
 		msk = bpf_skc_to_mptcp_sock(sk);
 		if (!msk)
@@ -63,9 +66,11 @@ int _sockops(struct bpf_sock_ops *ctx)
 
 		storage->token = msk->token;
 		memcpy(storage->ca_name, msk->ca_name, TCP_CA_NAME_MAX);
+		storage->first = msk->first;
 	}
 	storage->invoked++;
 	storage->is_mptcp = tcp_sk->is_mptcp;
+	storage->sk = (struct sock *)sk;
 
 	return 1;
 }