mptcp: Add key generation and token tree

Generate the local keys, IDSN, and token when creating a new socket.
Introduce the token tree to track all tokens in use using a radix tree
with the MPTCP token itself as the index.

Override the rebuild_header callback in inet_connection_sock_af_ops for
creating the local key on a new outgoing connection.

Override the init_req callback of tcp_request_sock_ops for creating the
local key on a new incoming connection.

Will be used to obtain the MPTCP parent socket to handle incoming joins.

Co-developed-by: Davide Caratti <dcaratti@redhat.com>
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
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: Christoph Paasch <cpaasch@apple.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/mptcp/subflow.c

@@ -4,6 +4,8 @@
  * Copyright (c) 2017 - 2019, Intel Corporation.
  */
 
+#define pr_fmt(fmt) "MPTCP: " fmt
+
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/netdevice.h>
@@ -18,6 +20,33 @@
 #include <net/mptcp.h>
 #include "protocol.h"
 
+static int subflow_rebuild_header(struct sock *sk)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+	int err = 0;
+
+	if (subflow->request_mptcp && !subflow->token) {
+		pr_debug("subflow=%p", sk);
+		err = mptcp_token_new_connect(sk);
+	}
+
+	if (err)
+		return err;
+
+	return subflow->icsk_af_ops->rebuild_header(sk);
+}
+
+static void subflow_req_destructor(struct request_sock *req)
+{
+	struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
+
+	pr_debug("subflow_req=%p", subflow_req);
+
+	if (subflow_req->mp_capable)
+		mptcp_token_destroy_request(subflow_req->token);
+	tcp_request_sock_ops.destructor(req);
+}
+
 static void subflow_init_req(struct request_sock *req,
 			     const struct sock *sk_listener,
 			     struct sk_buff *skb)
@@ -42,7 +71,12 @@ static void subflow_init_req(struct request_sock *req,
 #endif
 
 	if (rx_opt.mptcp.mp_capable && listener->request_mptcp) {
-		subflow_req->mp_capable = 1;
+		int err;
+
+		err = mptcp_token_new_request(req);
+		if (err == 0)
+			subflow_req->mp_capable = 1;
+
 		subflow_req->remote_key = rx_opt.mptcp.sndr_key;
 	}
 }
@@ -150,16 +184,28 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk,
 						     req_unhash, own_req);
 
 	if (child && *own_req) {
-		if (!mptcp_subflow_ctx(child)) {
-			pr_debug("Closing child socket");
-			inet_sk_set_state(child, TCP_CLOSE);
-			sock_set_flag(child, SOCK_DEAD);
-			inet_csk_destroy_sock(child);
-			child = NULL;
+		struct mptcp_subflow_context *ctx = mptcp_subflow_ctx(child);
+
+		/* we have null ctx on TCP fallback, not fatal on MPC
+		 * handshake
+		 */
+		if (!ctx)
+			return child;
+
+		if (ctx->mp_capable) {
+			if (mptcp_token_new_accept(ctx->token))
+				goto close_child;
 		}
 	}
 
 	return child;
+
+close_child:
+	pr_debug("closing child socket");
+	tcp_send_active_reset(child, GFP_ATOMIC);
+	inet_csk_prepare_forced_close(child);
+	tcp_done(child);
+	return NULL;
 }
 
 static struct inet_connection_sock_af_ops subflow_specific;
@@ -224,6 +270,7 @@ int mptcp_subflow_create_socket(struct sock *sk, struct socket **new_sock)
 	pr_debug("subflow=%p", subflow);
 
 	*new_sock = sf;
+	sock_hold(sk);
 	subflow->conn = sk;
 
 	return 0;
@@ -286,6 +333,9 @@ static void subflow_ulp_release(struct sock *sk)
 	if (!ctx)
 		return;
 
+	if (ctx->conn)
+		sock_put(ctx->conn);
+
 	kfree_rcu(ctx, rcu);
 }
 
@@ -323,6 +373,7 @@ static void subflow_ulp_clone(const struct request_sock *req,
 	new_ctx->fourth_ack = 1;
 	new_ctx->remote_key = subflow_req->remote_key;
 	new_ctx->local_key = subflow_req->local_key;
+	new_ctx->token = subflow_req->token;
 }
 
 static struct tcp_ulp_ops subflow_ulp_ops __read_mostly = {
@@ -346,6 +397,8 @@ static int subflow_ops_init(struct request_sock_ops *subflow_ops)
 	if (!subflow_ops->slab)
 		return -ENOMEM;
 
+	subflow_ops->destructor = subflow_req_destructor;
+
 	return 0;
 }
 
@@ -362,6 +415,7 @@ void mptcp_subflow_init(void)
 	subflow_specific.conn_request = subflow_v4_conn_request;
 	subflow_specific.syn_recv_sock = subflow_syn_recv_sock;
 	subflow_specific.sk_rx_dst_set = subflow_finish_connect;
+	subflow_specific.rebuild_header = subflow_rebuild_header;
 
 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 	subflow_request_sock_ipv6_ops = tcp_request_sock_ipv6_ops;
@@ -371,6 +425,7 @@ void mptcp_subflow_init(void)
 	subflow_v6_specific.conn_request = subflow_v6_conn_request;
 	subflow_v6_specific.syn_recv_sock = subflow_syn_recv_sock;
 	subflow_v6_specific.sk_rx_dst_set = subflow_finish_connect;
+	subflow_v6_specific.rebuild_header = subflow_rebuild_header;
 
 	subflow_v6m_specific = subflow_v6_specific;
 	subflow_v6m_specific.queue_xmit = ipv4_specific.queue_xmit;