Re: [MPTCP] [RFC PATCH v3 10/16] mptcp: Add shutdown() socket operation

[Krystad, Peter <peter.krystad at intel.com>]

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On Wed, 2018-10-10 at 14:43 +0200, Matthieu Baerts wrote:
> Hi Peter,
> 
> On 06/10/2018 00:59, Mat Martineau wrote:
> > From: Peter Krystad <peter.krystad(a)intel.com>
> > 
> > Signed-off-by: Peter Krystad <peter.krystad(a)intel.com>
> > ---
> >  net/mptcp/protocol.c | 21 ++++++++++++++++++++-
> >  1 file changed, 20 insertions(+), 1 deletion(-)
> > 
> > diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
> > index 2fa9031a77ca..3d10ab287bd6 100644
> > --- a/net/mptcp/protocol.c
> > +++ b/net/mptcp/protocol.c
> > @@ -255,6 +255,25 @@ int mptcp_stream_accept(struct socket *sock, struct socket *newsock, int flags,
> >  	return inet_accept(sock, newsock, flags, kern);
> >  }
> >  
> > +int mptcp_stream_shutdown(struct socket *sock, int how)
> > +{
> > +	struct mptcp_sock *msk = mptcp_sk(sock->sk);
> > +	int ret = 0;
> > +
> > +	pr_debug("sk=%p, how=%d", msk, how);
> > +
> > +	if (msk->subflow) {
> > +		pr_debug("subflow=%p", msk->subflow->sk);
> > +		ret = kernel_sock_shutdown(msk->subflow, how);
> > +	}
> > +	if (msk->connection_list) {
> > +		pr_debug("conn_list->subflow=%p", msk->connection_list->sk);
> > +		ret = kernel_sock_shutdown(msk->connection_list, how);
> 
> Just to be sure, can we have "subflow != NULL" and "connection_list !=
> NULL"?
> Because I saw the possible override of "ret" here but it is not possible
> to have both a "subflow" and a "connection_list" (we could use a "else
> if" here I guess).

Your point is good, it should not be possible for them both to be set.


But in a future commit the connection_list will become a real rcu
linked list of  subflows and a single lock will be used to protect the
list and the subflow field. When the in-progress subflow is done
connecting it will be moved to the connection list under lock
protection.

Peter.

> Cheers,
> Matthieu
> 
> > +	}
> > +
> > +	return ret;
> > +}
> > +
> >  static struct proto mptcp_prot = {
> >  	.name		= "MPTCP",
> >  	.owner		= THIS_MODULE,
> > @@ -284,7 +303,7 @@ const struct proto_ops mptcp_stream_ops = {
> >  	.poll		   = tcp_poll,
> >  	.ioctl		   = inet_ioctl,
> >  	.listen		   = mptcp_stream_listen,
> > -	.shutdown	   = inet_shutdown,
> > +	.shutdown	   = mptcp_stream_shutdown,
> >  	.setsockopt	   = sock_common_setsockopt,
> >  	.getsockopt	   = sock_common_getsockopt,
> >  	.sendmsg	   = inet_sendmsg,
> > 
> 
>