mptcp: keep unaccepted MPC subflow into join list

This will simplify all operation dealing with subflows
before accept time (e.g. data fin processing, add_addr).

The join list is already flushed by mptcp_stream_accept()
before returning the newly created msk to the user space.

This also fixes an potential bug present into the old code:
conn_list was manipulated without helding the msk lock
in mptcp_stream_accept().

Tested-by: Geliang Tang <geliangtang@gmail.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 868c76c..212be3b 100644 (file)
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -2343,7 +2343,6 @@ static struct sock *mptcp_accept(struct sock *sk, int flags, int *err,
        if (sk_is_mptcp(newsk)) {
                struct mptcp_subflow_context *subflow;
                struct sock *new_mptcp_sock;
-               struct sock *ssk = newsk;
 
                subflow = mptcp_subflow_ctx(newsk);
                new_mptcp_sock = subflow->conn;
@@ -2358,22 +2357,8 @@ static struct sock *mptcp_accept(struct sock *sk, int flags, int *err,
 
                /* acquire the 2nd reference for the owning socket */
                sock_hold(new_mptcp_sock);
-
-               local_bh_disable();
-               bh_lock_sock(new_mptcp_sock);
-               msk = mptcp_sk(new_mptcp_sock);
-               msk->first = newsk;
-
                newsk = new_mptcp_sock;
-               mptcp_copy_inaddrs(newsk, ssk);
-               list_add(&subflow->node, &msk->conn_list);
-               sock_hold(ssk);
-
-               mptcp_rcv_space_init(msk, ssk);
-               bh_unlock_sock(new_mptcp_sock);
-
-               __MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPCAPABLEPASSIVEACK);
-               local_bh_enable();
+               MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPCAPABLEPASSIVEACK);
        } else {
                MPTCP_INC_STATS(sock_net(sk),
                                MPTCP_MIB_MPCAPABLEPASSIVEFALLBACK);
@@ -2824,6 +2809,12 @@ static int mptcp_stream_accept(struct socket *sock, struct socket *newsock,
        if (err == 0 && !mptcp_is_tcpsk(newsock->sk)) {
                struct mptcp_sock *msk = mptcp_sk(newsock->sk);
                struct mptcp_subflow_context *subflow;
+               struct sock *newsk = newsock->sk;
+               bool slowpath;
+
+               slowpath = lock_sock_fast(newsk);
+               mptcp_copy_inaddrs(newsk, msk->first);
+               mptcp_rcv_space_init(msk, msk->first);
 
                /* set ssk->sk_socket of accept()ed flows to mptcp socket.
                 * This is needed so NOSPACE flag can be set from tcp stack.
@@ -2835,6 +2826,7 @@ static int mptcp_stream_accept(struct socket *sock, struct socket *newsock,
                        if (!ssk->sk_socket)
                                mptcp_sock_graft(ssk, newsock);
                }
+               unlock_sock_fast(newsk, slowpath);
        }
 
        if (inet_csk_listen_poll(ssock->sk))

diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 10fffc5..7affaf0 100644 (file)
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -403,6 +403,15 @@ mptcp_subflow_get_mapped_dsn(const struct mptcp_subflow_context *subflow)
        return subflow->map_seq + mptcp_subflow_get_map_offset(subflow);
 }
 
+static inline void mptcp_add_pending_subflow(struct mptcp_sock *msk,
+                                            struct mptcp_subflow_context *subflow)
+{
+       sock_hold(mptcp_subflow_tcp_sock(subflow));
+       spin_lock_bh(&msk->join_list_lock);
+       list_add_tail(&subflow->node, &msk->join_list);
+       spin_unlock_bh(&msk->join_list_lock);
+}
+
 int mptcp_is_enabled(struct net *net);
 unsigned int mptcp_get_add_addr_timeout(struct net *net);
 void mptcp_subflow_fully_established(struct mptcp_subflow_context *subflow,

diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 7942597..d3c6b3a 100644 (file)
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -578,6 +578,10 @@ create_child:
                         */
                        inet_sk_state_store((void *)new_msk, TCP_ESTABLISHED);
 
+                       /* link the newly created socket to the msk */
+                       mptcp_add_pending_subflow(mptcp_sk(new_msk), ctx);
+                       WRITE_ONCE(mptcp_sk(new_msk)->first, child);
+
                        /* new mpc subflow takes ownership of the newly
                         * created mptcp socket
                         */
@@ -1124,11 +1128,7 @@ int __mptcp_subflow_connect(struct sock *sk, const struct mptcp_addr_info *loc,
        if (err && err != -EINPROGRESS)
                goto failed;
 
-       sock_hold(ssk);
-       spin_lock_bh(&msk->join_list_lock);
-       list_add_tail(&subflow->node, &msk->join_list);
-       spin_unlock_bh(&msk->join_list_lock);
-
+       mptcp_add_pending_subflow(msk, subflow);
        return err;
 
 failed: