[PATCH net-next 02/14] mptcp: avoid additional __inet_stream_connect() call

Matthieu Baerts
2023-08-11T15:58:51Z

The mptcp protocol maintains an additional socket just to easily
invoke a few stream operations on the first subflow. One of them is
__inet_stream_connect().

We are going to remove the first subflow socket soon, so avoid
the additional indirection via at connect time, calling directly
into the sock-level connect() ops.

The sk-level connect never return -EINPROGRESS, cleanup the error
path accordingly. Additionally, the ssk status on error is always
TCP_CLOSE. Avoid unneeded access to the subflow sk state.

No functional change intended.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
---
net/mptcp/protocol.c | 49 +++++++++++++++++++++++++++++++++----------------
1 file changed, 33 insertions(+), 16 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index abb310548c37..b888d6339c80 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -3589,22 +3589,24 @@ static int mptcp_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
struct mptcp_sock *msk = mptcp_sk(sk);
struct socket *ssock;
int err = -EINVAL;
+ struct sock *ssk;

ssock = __mptcp_nmpc_socket(msk);
if (IS_ERR(ssock))
return PTR_ERR(ssock);

inet_sk_state_store(sk, TCP_SYN_SENT);
- subflow = mptcp_subflow_ctx(ssock->sk);
+ ssk = msk->first;
+ subflow = mptcp_subflow_ctx(ssk);
#ifdef CONFIG_TCP_MD5SIG
/* no MPTCP if MD5SIG is enabled on this socket or we may run out of
* TCP option space.
*/
- if (rcu_access_pointer(tcp_sk(ssock->sk)->md5sig_info))
+ if (rcu_access_pointer(tcp_sk(ssk)->md5sig_info))
mptcp_subflow_early_fallback(msk, subflow);
#endif
- if (subflow->request_mptcp && mptcp_token_new_connect(ssock->sk)) {
- MPTCP_INC_STATS(sock_net(ssock->sk), MPTCP_MIB_TOKENFALLBACKINIT);
+ if (subflow->request_mptcp && mptcp_token_new_connect(ssk)) {
+ MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_TOKENFALLBACKINIT);
mptcp_subflow_early_fallback(msk, subflow);
}
if (likely(!__mptcp_check_fallback(msk)))
@@ -3613,27 +3615,42 @@ static int mptcp_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
/* if reaching here via the fastopen/sendmsg path, the caller already
* acquired the subflow socket lock, too.
*/
- if (msk->fastopening)
- err = __inet_stream_connect(ssock, uaddr, addr_len, O_NONBLOCK, 1);
- else
- err = inet_stream_connect(ssock, uaddr, addr_len, O_NONBLOCK);
- inet_sk(sk)->defer_connect = inet_sk(ssock->sk)->defer_connect;
+ if (!msk->fastopening)
+ lock_sock(ssk);
+
+ /* the following mirrors closely a very small chunk of code from
+ * __inet_stream_connect()
+ */
+ if (ssk->sk_state != TCP_CLOSE)
+ goto out;
+
+ if (BPF_CGROUP_PRE_CONNECT_ENABLED(ssk)) {
+ err = ssk->sk_prot->pre_connect(ssk, uaddr, addr_len);
+ if (err)
+ goto out;
+ }
+
+ err = ssk->sk_prot->connect(ssk, uaddr, addr_len);
+ if (err < 0)
+ goto out;
+
+ inet_sk(sk)->defer_connect = inet_sk(ssk)->defer_connect;
+
+out:
+ if (!msk->fastopening)
+ release_sock(ssk);

/* on successful connect, the msk state will be moved to established by
* subflow_finish_connect()
*/
- if (unlikely(err && err != -EINPROGRESS)) {
+ if (unlikely(err)) {
/* avoid leaving a dangling token in an unconnected socket */
mptcp_token_destroy(msk);
- inet_sk_state_store(sk, inet_sk_state_load(ssock->sk));
+ inet_sk_state_store(sk, TCP_CLOSE);
return err;
}

- mptcp_copy_inaddrs(sk, ssock->sk);
-
- /* silence EINPROGRESS and let the caller inet_stream_connect
- * handle the connection in progress
- */
+ mptcp_copy_inaddrs(sk, ssk);
return 0;
}

--
2.40.1