[PATCH net 2/4] mptcp: remove MPTCP 'ifdef' in TCP SYN cookies

Mat Martineau
2022-12-10T00:28:24Z

To ease the maintenance, it is often recommended to avoid having #ifdef
preprocessor conditions.

Here the section related to CONFIG_MPTCP was quite short but the next
commit needs to add more code around. It is then cleaner to move
specific MPTCP code to functions located in net/mptcp directory.

Now that mptcp_subflow_request_sock_ops structure can be static, it can
also be marked as "read only after init".

Suggested-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
---
include/net/mptcp.h | 12 ++++++++++--
net/ipv4/syncookies.c | 7 +++----
net/mptcp/subflow.c | 12 +++++++++++-
3 files changed, 24 insertions(+), 7 deletions(-)

diff --git a/include/net/mptcp.h b/include/net/mptcp.h
index 412479ebf5ad..3c5c68618fcc 100644
--- a/include/net/mptcp.h
+++ b/include/net/mptcp.h
@@ -97,8 +97,6 @@ struct mptcp_out_options {
};

#ifdef CONFIG_MPTCP
-extern struct request_sock_ops mptcp_subflow_request_sock_ops;
-
void mptcp_init(void);

static inline bool sk_is_mptcp(const struct sock *sk)
@@ -188,6 +186,9 @@ void mptcp_seq_show(struct seq_file *seq);
int mptcp_subflow_init_cookie_req(struct request_sock *req,
const struct sock *sk_listener,
struct sk_buff *skb);
+struct request_sock *mptcp_subflow_reqsk_alloc(const struct request_sock_ops *ops,
+ struct sock *sk_listener,
+ bool attach_listener);

__be32 mptcp_get_reset_option(const struct sk_buff *skb);

@@ -274,6 +275,13 @@ static inline int mptcp_subflow_init_cookie_req(struct request_sock *req,
return 0; /* TCP fallback */
}

+static inline struct request_sock *mptcp_subflow_reqsk_alloc(const struct request_sock_ops *ops,
+ struct sock *sk_listener,
+ bool attach_listener)
+{
+ return NULL;
+}
+
static inline __be32 mptcp_reset_option(const struct sk_buff *skb) { return htonl(0u); }
#endif /* CONFIG_MPTCP */

diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index 942d2dfa1115..26fb97d1d4d9 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -288,12 +288,11 @@ struct request_sock *cookie_tcp_reqsk_alloc(const struct request_sock_ops *ops,
struct tcp_request_sock *treq;
struct request_sock *req;

-#ifdef CONFIG_MPTCP
if (sk_is_mptcp(sk))
- ops = &mptcp_subflow_request_sock_ops;
-#endif
+ req = mptcp_subflow_reqsk_alloc(ops, sk, false);
+ else
+ req = inet_reqsk_alloc(ops, sk, false);

- req = inet_reqsk_alloc(ops, sk, false);
if (!req)
return NULL;

diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 2159b5f9988f..3f670f2d5c5c 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -529,7 +529,7 @@ static int subflow_v6_rebuild_header(struct sock *sk)
}
#endif

-struct request_sock_ops mptcp_subflow_request_sock_ops;
+static struct request_sock_ops mptcp_subflow_request_sock_ops __ro_after_init;
static struct tcp_request_sock_ops subflow_request_sock_ipv4_ops __ro_after_init;

static int subflow_v4_conn_request(struct sock *sk, struct sk_buff *skb)
@@ -582,6 +582,16 @@ static int subflow_v6_conn_request(struct sock *sk, struct sk_buff *skb)
}
#endif

+struct request_sock *mptcp_subflow_reqsk_alloc(const struct request_sock_ops *ops,
+ struct sock *sk_listener,
+ bool attach_listener)
+{
+ ops = &mptcp_subflow_request_sock_ops;
+
+ return inet_reqsk_alloc(ops, sk_listener, attach_listener);
+}
+EXPORT_SYMBOL(mptcp_subflow_reqsk_alloc);
+
/* validate hmac received in third ACK */
static bool subflow_hmac_valid(const struct request_sock *req,
const struct mptcp_options_received *mp_opt)
--
2.38.1