mptcp: Add handling of incoming MP_JOIN requests

Process the MP_JOIN option in a SYN packet with the same flow
as MP_CAPABLE but when the third ACK is received add the
subflow to the MPTCP socket subflow list instead of adding it to
the TCP socket accept queue.

The subflow is added at the end of the subflow list so it will not
interfere with the existing subflows operation and no data is
expected to be transmitted on it.

Co-developed-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Florian Westphal <fw@strlen.de>
Co-developed-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Peter Krystad <peter.krystad@linux.intel.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 79 insertions, 17 deletions

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 5f93e8c94ef9..f2dac715a17e 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -104,19 +104,6 @@ set_state:
 	return ssock;
 }
 
-static struct sock *mptcp_subflow_get(const struct mptcp_sock *msk)
-{
-	struct mptcp_subflow_context *subflow;
-
-	sock_owned_by_me((const struct sock *)msk);
-
-	mptcp_for_each_subflow(msk, subflow) {
-		return mptcp_subflow_tcp_sock(subflow);
-	}
-
-	return NULL;
-}
-
 static void __mptcp_move_skb(struct mptcp_sock *msk, struct sock *ssk,
 			     struct sk_buff *skb,
 			     unsigned int offset, size_t copy_len)
@@ -391,6 +378,43 @@ out:
 	return ret;
 }
 
+static struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk)
+{
+	struct mptcp_subflow_context *subflow;
+	struct sock *backup = NULL;
+
+	sock_owned_by_me((const struct sock *)msk);
+
+	mptcp_for_each_subflow(msk, subflow) {
+		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+
+		if (!sk_stream_memory_free(ssk)) {
+			struct socket *sock = ssk->sk_socket;
+
+			if (sock) {
+				clear_bit(MPTCP_SEND_SPACE, &msk->flags);
+				smp_mb__after_atomic();
+
+				/* enables sk->write_space() callbacks */
+				set_bit(SOCK_NOSPACE, &sock->flags);
+			}
+
+			return NULL;
+		}
+
+		if (subflow->backup) {
+			if (!backup)
+				backup = ssk;
+
+			continue;
+		}
+
+		return ssk;
+	}
+
+	return backup;
+}
+
 static void ssk_check_wmem(struct mptcp_sock *msk, struct sock *ssk)
 {
 	struct socket *sock;
@@ -438,10 +462,17 @@ fallback:
 		return ret >= 0 ? ret + copied : (copied ? copied : ret);
 	}
 
-	ssk = mptcp_subflow_get(msk);
-	if (!ssk) {
-		release_sock(sk);
-		return -ENOTCONN;
+	ssk = mptcp_subflow_get_send(msk);
+	while (!sk_stream_memory_free(sk) || !ssk) {
+		ret = sk_stream_wait_memory(sk, &timeo);
+		if (ret)
+			goto out;
+
+		ssk = mptcp_subflow_get_send(msk);
+		if (list_empty(&msk->conn_list)) {
+			ret = -ENOTCONN;
+			goto out;
+		}
 	}
 
 	pr_debug("conn_list->subflow=%p", ssk);
@@ -1070,6 +1101,37 @@ static void mptcp_sock_graft(struct sock *sk, struct socket *parent)
 	write_unlock_bh(&sk->sk_callback_lock);
 }
 
+bool mptcp_finish_join(struct sock *sk)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
+	struct sock *parent = (void *)msk;
+	struct socket *parent_sock;
+
+	pr_debug("msk=%p, subflow=%p", msk, subflow);
+
+	/* mptcp socket already closing? */
+	if (inet_sk_state_load(parent) != TCP_ESTABLISHED)
+		return false;
+
+	if (!msk->pm.server_side)
+		return true;
+
+	/* passive connection, attach to msk socket */
+	parent_sock = READ_ONCE(parent->sk_socket);
+	if (parent_sock && !sk->sk_socket)
+		mptcp_sock_graft(sk, parent_sock);
+
+	return mptcp_pm_allow_new_subflow(msk);
+}
+
+bool mptcp_sk_is_subflow(const struct sock *sk)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+
+	return subflow->mp_join == 1;
+}
+
 static bool mptcp_memory_free(const struct sock *sk, int wake)
 {
 	struct mptcp_sock *msk = mptcp_sk(sk);