mptcp: Associate MPTCP context with TCP socket

Use ULP to associate a subflow_context structure with each TCP subflow
socket. Creating these sockets requires new bind and connect functions
to make sure ULP is set up immediately when the subflow sockets are
created.

Co-developed-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Florian Westphal <fw@strlen.de>
Co-developed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Co-developed-by: Davide Caratti <dcaratti@redhat.com>
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
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: Christoph Paasch <cpaasch@apple.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 119 insertions, 0 deletions

diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
new file mode 100644
index 000000000000..bf8139353653
--- /dev/null
+++ b/net/mptcp/subflow.c
@@ -0,0 +1,119 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Multipath TCP
+ *
+ * Copyright (c) 2017 - 2019, Intel Corporation.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/netdevice.h>
+#include <net/sock.h>
+#include <net/inet_common.h>
+#include <net/inet_hashtables.h>
+#include <net/protocol.h>
+#include <net/tcp.h>
+#include <net/mptcp.h>
+#include "protocol.h"
+
+int mptcp_subflow_create_socket(struct sock *sk, struct socket **new_sock)
+{
+	struct mptcp_subflow_context *subflow;
+	struct net *net = sock_net(sk);
+	struct socket *sf;
+	int err;
+
+	err = sock_create_kern(net, PF_INET, SOCK_STREAM, IPPROTO_TCP, &sf);
+	if (err)
+		return err;
+
+	lock_sock(sf->sk);
+
+	/* kernel sockets do not by default acquire net ref, but TCP timer
+	 * needs it.
+	 */
+	sf->sk->sk_net_refcnt = 1;
+	get_net(net);
+	this_cpu_add(*net->core.sock_inuse, 1);
+	err = tcp_set_ulp(sf->sk, "mptcp");
+	release_sock(sf->sk);
+
+	if (err)
+		return err;
+
+	subflow = mptcp_subflow_ctx(sf->sk);
+	pr_debug("subflow=%p", subflow);
+
+	*new_sock = sf;
+	subflow->conn = sk;
+
+	return 0;
+}
+
+static struct mptcp_subflow_context *subflow_create_ctx(struct sock *sk,
+							gfp_t priority)
+{
+	struct inet_connection_sock *icsk = inet_csk(sk);
+	struct mptcp_subflow_context *ctx;
+
+	ctx = kzalloc(sizeof(*ctx), priority);
+	if (!ctx)
+		return NULL;
+
+	rcu_assign_pointer(icsk->icsk_ulp_data, ctx);
+
+	pr_debug("subflow=%p", ctx);
+
+	ctx->tcp_sock = sk;
+
+	return ctx;
+}
+
+static int subflow_ulp_init(struct sock *sk)
+{
+	struct mptcp_subflow_context *ctx;
+	struct tcp_sock *tp = tcp_sk(sk);
+	int err = 0;
+
+	/* disallow attaching ULP to a socket unless it has been
+	 * created with sock_create_kern()
+	 */
+	if (!sk->sk_kern_sock) {
+		err = -EOPNOTSUPP;
+		goto out;
+	}
+
+	ctx = subflow_create_ctx(sk, GFP_KERNEL);
+	if (!ctx) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	pr_debug("subflow=%p, family=%d", ctx, sk->sk_family);
+
+	tp->is_mptcp = 1;
+out:
+	return err;
+}
+
+static void subflow_ulp_release(struct sock *sk)
+{
+	struct mptcp_subflow_context *ctx = mptcp_subflow_ctx(sk);
+
+	if (!ctx)
+		return;
+
+	kfree_rcu(ctx, rcu);
+}
+
+static struct tcp_ulp_ops subflow_ulp_ops __read_mostly = {
+	.name		= "mptcp",
+	.owner		= THIS_MODULE,
+	.init		= subflow_ulp_init,
+	.release	= subflow_ulp_release,
+};
+
+void mptcp_subflow_init(void)
+{
+	if (tcp_register_ulp(&subflow_ulp_ops) != 0)
+		panic("MPTCP: failed to register subflows to ULP\n");
+}