linux-kernel - Re: [RFC] vsock: notify server to shutdown when client has pending signal

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Date:   Mon, 17 May 2021 12:10:30 +0200
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     "Longpeng (Mike, Cloud Infrastructure Service Product Dept.)" 
        <longpeng2@...wei.com>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Gonglei (Arei)" <arei.gonglei@...wei.com>,
        "Subo (Subo, Cloud Infrastructure Service Product Dept.)" 
        <subo7@...wei.com>, "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jorgen Hansen <jhansen@...are.com>,
        Norbert Slusarek <nslusarek@....net>,
        Andra Paraschiv <andraprs@...zon.com>,
        Colin Ian King <colin.king@...onical.com>,
        David Brazdil <dbrazdil@...gle.com>,
        Alexander Popov <alex.popov@...ux.com>,
        "lixianming (E)" <lixianming5@...wei.com>
Subject: Re: [RFC] vsock: notify server to shutdown when client has pending
 signal

On Mon, May 17, 2021 at 02:18:51AM +0000, Longpeng (Mike, Cloud Infrastructure Service Product Dept.) wrote:
>Hi Stefano,
>
>> -----Original Message-----
>> From: Longpeng (Mike, Cloud Infrastructure Service Product Dept.)
>> [mailto:longpeng2@...wei.com]
>> Sent: Thursday, May 13, 2021 6:36 PM
>> To: Stefano Garzarella <sgarzare@...hat.com>
>> Cc: netdev@...r.kernel.org; linux-kernel@...r.kernel.org; Gonglei (Arei)
>> <arei.gonglei@...wei.com>; Subo (Subo, Cloud Infrastructure Service Product
>> Dept.) <subo7@...wei.com>; David S . Miller <davem@...emloft.net>; Jakub
>> Kicinski <kuba@...nel.org>; Jorgen Hansen <jhansen@...are.com>; Norbert
>> Slusarek <nslusarek@....net>; Andra Paraschiv <andraprs@...zon.com>;
>> Colin Ian King <colin.king@...onical.com>; David Brazdil
>> <dbrazdil@...gle.com>; Alexander Popov <alex.popov@...ux.com>;
>> lixianming (E) <lixianming5@...wei.com>
>> Subject: RE: [RFC] vsock: notify server to shutdown when client has pending
>> signal
>>
>> Hi Stefano,
>>
>> > -----Original Message-----
>> > From: Stefano Garzarella [mailto:sgarzare@...hat.com]
>> > Sent: Thursday, May 13, 2021 5:42 PM
>> > To: Longpeng (Mike, Cloud Infrastructure Service Product Dept.)
>> > <longpeng2@...wei.com>
>> > Cc: netdev@...r.kernel.org; linux-kernel@...r.kernel.org; Gonglei
>> > (Arei) <arei.gonglei@...wei.com>; Subo (Subo, Cloud Infrastructure
>> > Service Product
>> > Dept.) <subo7@...wei.com>; David S . Miller <davem@...emloft.net>;
>> > Jakub Kicinski <kuba@...nel.org>; Jorgen Hansen <jhansen@...are.com>;
>> > Norbert Slusarek <nslusarek@....net>; Andra Paraschiv
>> > <andraprs@...zon.com>; Colin Ian King <colin.king@...onical.com>;
>> > David Brazdil <dbrazdil@...gle.com>; Alexander Popov
>> > <alex.popov@...ux.com>; lixianming (E) <lixianming5@...wei.com>
>> > Subject: Re: [RFC] vsock: notify server to shutdown when client has
>> > pending signal
>> >
>> > Hi,
>> > thanks for this patch, comments below...
>> >
>> > On Tue, May 11, 2021 at 05:41:27PM +0800, Longpeng(Mike) wrote:
>> > >The client's sk_state will be set to TCP_ESTABLISHED if the server
>> > >replay the client's connect request.
>> > >However, if the client has pending signal, its sk_state will be set
>> > >to TCP_CLOSE without notify the server, so the server will hold the
>> > >corrupt connection.
>> > >
>> > >            client                        server
>> > >
>> > >1. sk_state=TCP_SYN_SENT         |
>> > >2. call ->connect()              |
>> > >3. wait reply                    |
>> > >                                 | 4. sk_state=TCP_ESTABLISHED
>> > >                                 | 5. insert to connected list
>> > >                                 | 6. reply to the client
>> > >7. sk_state=TCP_ESTABLISHED      |
>> > >8. insert to connected list      |
>> > >9. *signal pending* <--------------------- the user kill client
>> > >10. sk_state=TCP_CLOSE           |
>> > >client is exiting...             |
>> > >11. call ->release()             |
>> > >     virtio_transport_close
>> > >      if (!(sk->sk_state == TCP_ESTABLISHED ||
>> > >	      sk->sk_state == TCP_CLOSING))
>> > >		return true; <------------- return at here As a result, the server
>> > >cannot notice the connection is corrupt.
>> > >So the client should notify the peer in this case.
>> > >
>> > >Cc: David S. Miller <davem@...emloft.net>
>> > >Cc: Jakub Kicinski <kuba@...nel.org>
>> > >Cc: Stefano Garzarella <sgarzare@...hat.com>
>> > >Cc: Jorgen Hansen <jhansen@...are.com>
>> > >Cc: Norbert Slusarek <nslusarek@....net>
>> > >Cc: Andra Paraschiv <andraprs@...zon.com>
>> > >Cc: Colin Ian King <colin.king@...onical.com>
>> > >Cc: David Brazdil <dbrazdil@...gle.com>
>> > >Cc: Alexander Popov <alex.popov@...ux.com>
>> > >Signed-off-by: lixianming <lixianming5@...wei.com>
>> > >Signed-off-by: Longpeng(Mike) <longpeng2@...wei.com>
>> > >---
>> > > net/vmw_vsock/af_vsock.c | 1 +
>> > > 1 file changed, 1 insertion(+)
>> > >
>> > >diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>> > >index
>> > >92a72f0..d5df908 100644
>> > >--- a/net/vmw_vsock/af_vsock.c
>> > >+++ b/net/vmw_vsock/af_vsock.c
>> > >@@ -1368,6 +1368,7 @@ static int vsock_stream_connect(struct socket
>> > >*sock,
>> > struct sockaddr *addr,
>> > > 		lock_sock(sk);
>> > >
>> > > 		if (signal_pending(current)) {
>> > >+			vsock_send_shutdown(sk, SHUTDOWN_MASK);
>> >
>> > I see the issue, but I'm not sure is okay to send the shutdown in any
>> > case, think about the server didn't setup the connection.
>> >
>> > Maybe is better to set TCP_CLOSING if the socket state was
>> > TCP_ESTABLISHED, so the shutdown will be handled by the
>> > transport->release() as usual.
>> >
>> > What do you think?
>> >
>>
>> Your method looks more gracefully, we'll try it and get back to you, 
>> thanks.
>>
>
>As your suggestion, the following code can solve the problem:
>
>                if (signal_pending(current)) {
>                        err = sock_intr_errno(timeout);
>-                       sk->sk_state = TCP_CLOSE;
>+                       sk->sk_state = TCP_CLOSING;
>                        sock->state = SS_UNCONNECTED;
>                        vsock_transport_cancel_pkt(vsk);
>                        goto out_wait;
>
>This will send shutdown to the server even if the connection is not established, but
>I don't see any side effects yet, right ?

Should we set TCP_CLOSING only if sk_state was TCP_ESTABLISHED?

>
>The problem is also in the timeout case, we should fix it together ?
>

I'm not sure, if we reach the timeout, it should mean that the other 
peer never answered, so why take care to notify it?

Thanks,
Stefano