mptcp: factor out mptcp_connect()

The current MPTCP connect implementation duplicates a bit of inet
code and does not use nor provide a struct proto->connect callback,
which in turn will not fit the upcoming fastopen implementation.

Refactor such implementation to use the common helper, moving the
MPTCP-specific bits into mptcp_connect(). Additionally, avoid an
indirect call to the subflow connect callback.

Note that the fastopen call-path invokes mptcp_connect() while already
holding the subflow socket lock. Explicitly keep track of such path
via a new MPTCP-level flag and handle the locking accordingly.

Additionally, track the connect flags in a new msk field to allow
propagating them to the subflow inet_stream_connect call.

Fixes: d98a82a6afc7 ("mptcp: handle defer connect in mptcp_sendmsg")
Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index e33f9ca..f293069 100644 (file)
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1698,7 +1698,10 @@ static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 
                lock_sock(ssk);
 
+               msk->connect_flags = (msg->msg_flags & MSG_DONTWAIT) ? O_NONBLOCK : 0;
+               msk->is_sendmsg = 1;
                ret = tcp_sendmsg_fastopen(ssk, msg, &copied_syn, len, NULL);
+               msk->is_sendmsg = 0;
                copied += copied_syn;
                if (ret == -EINPROGRESS && copied_syn > 0) {
                        /* reflect the new state on the MPTCP socket */
@@ -3507,10 +3510,73 @@ static int mptcp_ioctl(struct sock *sk, int cmd, unsigned long arg)
        return put_user(answ, (int __user *)arg);
 }
 
+static void mptcp_subflow_early_fallback(struct mptcp_sock *msk,
+                                        struct mptcp_subflow_context *subflow)
+{
+       subflow->request_mptcp = 0;
+       __mptcp_do_fallback(msk);
+}
+
+static int mptcp_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
+{
+       struct mptcp_subflow_context *subflow;
+       struct mptcp_sock *msk = mptcp_sk(sk);
+       struct socket *ssock;
+       int err = -EINVAL;
+
+       ssock = __mptcp_nmpc_socket(msk);
+       if (!ssock)
+               return -EINVAL;
+
+       mptcp_token_destroy(msk);
+       inet_sk_state_store(sk, TCP_SYN_SENT);
+       subflow = mptcp_subflow_ctx(ssock->sk);
+#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))
+               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);
+               mptcp_subflow_early_fallback(msk, subflow);
+       }
+       if (likely(!__mptcp_check_fallback(msk)))
+               MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPCAPABLEACTIVE);
+
+       /* if reaching here via the fastopen/sendmsg path, the caller already
+        * acquired the subflow socket lock, too.
+        */
+       if (msk->is_sendmsg)
+               err = __inet_stream_connect(ssock, uaddr, addr_len, msk->connect_flags, 1);
+       else
+               err = inet_stream_connect(ssock, uaddr, addr_len, msk->connect_flags);
+       inet_sk(sk)->defer_connect = inet_sk(ssock->sk)->defer_connect;
+
+       /* on successful connect, the msk state will be moved to established by
+        * subflow_finish_connect()
+        */
+       if (unlikely(err && err != -EINPROGRESS)) {
+               inet_sk_state_store(sk, inet_sk_state_load(ssock->sk));
+               return err;
+       }
+
+       mptcp_copy_inaddrs(sk, ssock->sk);
+
+       /* unblocking connect, mptcp-level inet_stream_connect will error out
+        * without changing the socket state, update it here.
+        */
+       if (err == -EINPROGRESS)
+               sk->sk_socket->state = ssock->state;
+       return err;
+}
+
 static struct proto mptcp_prot = {
        .name           = "MPTCP",
        .owner          = THIS_MODULE,
        .init           = mptcp_init_sock,
+       .connect        = mptcp_connect,
        .disconnect     = mptcp_disconnect,
        .close          = mptcp_close,
        .accept         = mptcp_accept,
@@ -3562,78 +3628,16 @@ unlock:
        return err;
 }
 
-static void mptcp_subflow_early_fallback(struct mptcp_sock *msk,
-                                        struct mptcp_subflow_context *subflow)
-{
-       subflow->request_mptcp = 0;
-       __mptcp_do_fallback(msk);
-}
-
 static int mptcp_stream_connect(struct socket *sock, struct sockaddr *uaddr,
                                int addr_len, int flags)
 {
-       struct mptcp_sock *msk = mptcp_sk(sock->sk);
-       struct mptcp_subflow_context *subflow;
-       struct socket *ssock;
-       int err = -EINVAL;
+       int ret;
 
        lock_sock(sock->sk);
-       if (uaddr) {
-               if (addr_len < sizeof(uaddr->sa_family))
-                       goto unlock;
-
-               if (uaddr->sa_family == AF_UNSPEC) {
-                       err = mptcp_disconnect(sock->sk, flags);
-                       sock->state = err ? SS_DISCONNECTING : SS_UNCONNECTED;
-                       goto unlock;
-               }
-       }
-
-       if (sock->state != SS_UNCONNECTED && msk->subflow) {
-               /* pending connection or invalid state, let existing subflow
-                * cope with that
-                */
-               ssock = msk->subflow;
-               goto do_connect;
-       }
-
-       ssock = __mptcp_nmpc_socket(msk);
-       if (!ssock)
-               goto unlock;
-
-       mptcp_token_destroy(msk);
-       inet_sk_state_store(sock->sk, TCP_SYN_SENT);
-       subflow = mptcp_subflow_ctx(ssock->sk);
-#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))
-               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);
-               mptcp_subflow_early_fallback(msk, subflow);
-       }
-       if (likely(!__mptcp_check_fallback(msk)))
-               MPTCP_INC_STATS(sock_net(sock->sk), MPTCP_MIB_MPCAPABLEACTIVE);
-
-do_connect:
-       err = ssock->ops->connect(ssock, uaddr, addr_len, flags);
-       inet_sk(sock->sk)->defer_connect = inet_sk(ssock->sk)->defer_connect;
-       sock->state = ssock->state;
-
-       /* on successful connect, the msk state will be moved to established by
-        * subflow_finish_connect()
-        */
-       if (!err || err == -EINPROGRESS)
-               mptcp_copy_inaddrs(sock->sk, ssock->sk);
-       else
-               inet_sk_state_store(sock->sk, inet_sk_state_load(ssock->sk));
-
-unlock:
+       mptcp_sk(sock->sk)->connect_flags = flags;
+       ret = __inet_stream_connect(sock, uaddr, addr_len, flags, 0);
        release_sock(sock->sk);
-       return err;
+       return ret;
 }
 
 static int mptcp_listen(struct socket *sock, int backlog)

diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index be19592..6a09ab9 100644 (file)
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -285,7 +285,9 @@ struct mptcp_sock {
        u8              mpc_endpoint_id;
        u8              recvmsg_inq:1,
                        cork:1,
-                       nodelay:1;
+                       nodelay:1,
+                       is_sendmsg:1;
+       int             connect_flags;
        struct work_struct work;
        struct sk_buff  *ooo_last_skb;
        struct rb_root  out_of_order_queue;