mptcp: fix connect timeout handling

Ondrej reported a functional issue WRT timeout handling on connect
with a nice reproducer.

The problem is that the current mptcp connect waits for both the
MPTCP socket level timeout, and the first subflow socket timeout.
The latter is not influenced/touched by the exposed setsockopt().

Overall the above makes the SO_SNDTIMEO a no-op on connect.

Since mptcp_connect is invoked via inet_stream_connect and the
latter properly handle the MPTCP level timeout, we can address the
issue making the nested subflow level connect always unblocking.

This also allow simplifying a bit the code, dropping an ugly hack
to handle the fastopen and custom proto_ops connect.

The issues predates the blamed commit below, but the current resolution
requires the infrastructure introduced there.

Fixes: 54f1944ed6d2 ("mptcp: factor out mptcp_connect()")
Reported-by: Ondrej Mosnacek <omosnace@redhat.com>
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/399
Cc: stable@vger.kernel.org
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 08dc53f56bc23254e30e08fe82630c8e1cb4d15b..9cafd3b899088b4d2790035c893d4afb25240b28 100644 (file)
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1702,7 +1702,6 @@ static int mptcp_sendmsg_fastopen(struct sock *sk, struct msghdr *msg,
 
        lock_sock(ssk);
        msg->msg_flags |= MSG_DONTWAIT;
-       msk->connect_flags = O_NONBLOCK;
        msk->fastopening = 1;
        ret = tcp_sendmsg_fastopen(ssk, msg, copied_syn, len, NULL);
        msk->fastopening = 0;
@@ -3617,9 +3616,9 @@ static int mptcp_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
         * acquired the subflow socket lock, too.
         */
        if (msk->fastopening)
-               err = __inet_stream_connect(ssock, uaddr, addr_len, msk->connect_flags, 1);
+               err = __inet_stream_connect(ssock, uaddr, addr_len, O_NONBLOCK, 1);
        else
-               err = inet_stream_connect(ssock, uaddr, addr_len, msk->connect_flags);
+               err = inet_stream_connect(ssock, uaddr, addr_len, O_NONBLOCK);
        inet_sk(sk)->defer_connect = inet_sk(ssock->sk)->defer_connect;
 
        /* on successful connect, the msk state will be moved to established by
@@ -3632,12 +3631,10 @@ static int mptcp_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
 
        mptcp_copy_inaddrs(sk, ssock->sk);
 
-       /* unblocking connect, mptcp-level inet_stream_connect will error out
-        * without changing the socket state, update it here.
+       /* silence EINPROGRESS and let the caller inet_stream_connect
+        * handle the connection in progress
         */
-       if (err == -EINPROGRESS)
-               sk->sk_socket->state = ssock->state;
-       return err;
+       return 0;
 }
 
 static struct proto mptcp_prot = {
@@ -3696,18 +3693,6 @@ unlock:
        return err;
 }
 
-static int mptcp_stream_connect(struct socket *sock, struct sockaddr *uaddr,
-                               int addr_len, int flags)
-{
-       int ret;
-
-       lock_sock(sock->sk);
-       mptcp_sk(sock->sk)->connect_flags = flags;
-       ret = __inet_stream_connect(sock, uaddr, addr_len, flags, 0);
-       release_sock(sock->sk);
-       return ret;
-}
-
 static int mptcp_listen(struct socket *sock, int backlog)
 {
        struct mptcp_sock *msk = mptcp_sk(sock->sk);
@@ -3859,7 +3844,7 @@ static const struct proto_ops mptcp_stream_ops = {
        .owner             = THIS_MODULE,
        .release           = inet_release,
        .bind              = mptcp_bind,
-       .connect           = mptcp_stream_connect,
+       .connect           = inet_stream_connect,
        .socketpair        = sock_no_socketpair,
        .accept            = mptcp_stream_accept,
        .getname           = inet_getname,
@@ -3954,7 +3939,7 @@ static const struct proto_ops mptcp_v6_stream_ops = {
        .owner             = THIS_MODULE,
        .release           = inet6_release,
        .bind              = mptcp_bind,
-       .connect           = mptcp_stream_connect,
+       .connect           = inet_stream_connect,
        .socketpair        = sock_no_socketpair,
        .accept            = mptcp_stream_accept,
        .getname           = inet6_getname,

diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 2d7b2c80a1641233795eb33e986c19837a2e5bc6..de4667dafe59898c5d302db0087a6d1315e1e88a 100644 (file)
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -297,7 +297,6 @@ struct mptcp_sock {
                        nodelay:1,
                        fastopening:1,
                        in_accept_queue:1;
-       int             connect_flags;
        struct work_struct work;
        struct sk_buff  *ooo_last_skb;
        struct rb_root  out_of_order_queue;