Re: [MPTCP] [RFC PATCH v3 07/16] mptcp: Create SUBFLOW socket for outgoing connections

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

[-- Attachment #1: Type: text/plain, Size: 22278 bytes --]

On Tue, 2018-10-09 at 17:55 +0200, Matthieu Baerts wrote:
> Hi Peter,
> 
> Nice again!
> I only have some details and questions on my side.
> 
> I guess we can look at the details later.
> 
> On 06/10/2018 00:59, Mat Martineau wrote:
> > From: Peter Krystad <peter.krystad(a)intel.com>
> > 
> > Add subflow_sock type that extends tcp_sock and add an
> > is_mptcp flag to tcp_sock to distinguish them.
> > 
> > Override the bind() and connect() methods of the MPTCP
> > socket proto_ops so they may act on the subflow socket
> > instead, and use the .sk_rx_dst_set() handler in the subflow
> > proto to capture when the responding SYN-ACK is received.
> > 
> > Add handling in tcp_output.c to add MP_CAPABLE to an outgoing
> > SYN request for a subflow_sock and to the final ACK of the
> > three-way handshake.
> > 
> > Signed-off-by: Peter Krystad <peter.krystad(a)intel.com>
> > ---
> >  include/linux/tcp.h   |   2 +
> >  include/net/mptcp.h   |  35 +++++++-
> >  net/ipv4/tcp_input.c  |   9 ++
> >  net/ipv4/tcp_output.c |  32 +++++++
> >  net/mptcp/Makefile    |   2 +-
> >  net/mptcp/options.c   |  11 +++
> >  net/mptcp/protocol.c  | 161 +++++++++++++++++++++++++++++------
> >  net/mptcp/subflow.c   | 192 ++++++++++++++++++++++++++++++++++++++++++
> >  8 files changed, 415 insertions(+), 29 deletions(-)
> >  create mode 100644 net/mptcp/subflow.c
> > 
> > diff --git a/include/linux/tcp.h b/include/linux/tcp.h
> > index cb40dcb43f95..7f0dd688376c 100644
> > --- a/include/linux/tcp.h
> > +++ b/include/linux/tcp.h
> > @@ -408,6 +408,8 @@ struct tcp_sock {
> >  	 */
> >  	struct request_sock *fastopen_rsk;
> >  	u32	*saved_syn;
> > +
> > +	bool	is_mptcp;
> 
> detail: can we use bool? Or one bit in a byte shared with other fields?

I will look for a place.

> 
> >  };
> >  
> >  enum tsq_enum {
> > diff --git a/include/net/mptcp.h b/include/net/mptcp.h
> > index 79daad717275..4b08eb4ccc6f 100644
> > --- a/include/net/mptcp.h
> > +++ b/include/net/mptcp.h
> > @@ -39,7 +39,10 @@
> >  struct mptcp_sock {
> >  	/* inet_connection_sock must be the first member */
> >  	struct	inet_connection_sock sk;
> > -	struct	socket *subflow;
> > +	u64	local_key;
> > +	u64	remote_key;
> > +	struct	socket *connection_list; /* @@ needs to be a list */
> > +	struct	socket *subflow; /* outgoing connect, listener or !mp_capable */
> >  };
> >  
> >  static inline struct mptcp_sock *mptcp_sk(const struct sock *sk)
> > @@ -47,10 +50,35 @@ static inline struct mptcp_sock *mptcp_sk(const struct sock *sk)
> >  	return (struct mptcp_sock *)sk;
> >  }
> >  
> > +/* MPTCP subflow sock structure */
> > +struct subflow_sock {
> 
> detail: should we not start prefixing all MPTCP specific functions and
> structures with "mptcp_"?

My thinking is that we will try to only use this structure within MPTCP
code (passed as 'struct sock' everywhere else) so the meaning of
subflow within mptcp is clear. Also might be confusing with mptcp_sock
and mptcp_subflow_sock.
 
> 
> > +	/* tcp_sock must be the first member */
> > +	struct	tcp_sock sk;
> > +	u64	local_key;
> > +	u64	remote_key;
> > +	bool	request_mptcp;	// send MP_CAPABLE
> > +	bool	checksum;
> > +	bool	version;
> > +	bool	mp_capable;	// remote is MPTCP capable
> > +	bool	fourth_ack;	// send initial DSS
> 
> detail: we should maybe continue in the same idea as with is_mptcp:
> is_fourth_ack, etc. especially for fields like checksum and version.
> And maybe share a byte but can be changed later. I should certainly not
> look at these details :-)

Definitely should share a byte for these flags.

> > +	struct	sock *conn;	// parent mptcp_sock
> > +};
> > +
> > +static inline struct subflow_sock *subflow_sk(const struct sock *sk)
> > +{
> > +	return (struct subflow_sock *)sk;
> > +}
> > +
> >  #ifdef CONFIG_MPTCP
> >  
> >  void mptcp_parse_option(const unsigned char *ptr, int opsize,
> >  			struct tcp_options_received *opt_rx);
> > +unsigned int mptcp_syn_options(struct sock *sk, u64 *local_key);
> > +
> > +void mptcp_finish_connect(struct sock *sk, int mp_capable);
> > +
> > +int mptcp_subflow_init(void);
> > +void mptcp_subflow_exit(void);
> >  
> >  void mptcp_get_options(const struct sk_buff *skb,
> >  		       struct tcp_options_received *options);
> > @@ -64,7 +92,10 @@ static inline void mptcp_parse_option(const unsigned char *ptr, int opsize,
> >  {
> >  }
> >  
> > -
> > +static inline unsigned int mptcp_syn_options(struct sock *sk, u64 *local_key)
> > +{
> > +	return 0;
> > +}
> >  
> >  #endif /* CONFIG_MPTCP */
> >  #endif /* __NET_MPTCP_H */
> > diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
> > index 81fccf0c9120..4cb38904bb5f 100644
> > --- a/net/ipv4/tcp_input.c
> > +++ b/net/ipv4/tcp_input.c
> > @@ -5856,6 +5856,15 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
> >  		tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
> >  		tcp_initialize_rcv_mss(sk);
> >  
> > +		// @@ could use a callout here
> > +		if (tp->is_mptcp) {
> > +			struct subflow_sock *subflow = subflow_sk(sk);
> > +			if (subflow->request_mptcp && tp->rx_opt.mptcp.mp_capable) {
> > +				subflow->mp_capable = 1;
> > +				subflow->remote_key = tp->rx_opt.mptcp.sndr_key;
> > +			}
> 
> detail: Should we do this kind of think in MPTCP specific files?

Agree, I should have followed the comment. This is removing
subflow_sock from tcp code too.

> 
> > +		}
> > +
> >  		/* Remember, tcp_poll() does not lock socket!
> >  		 * Change state from SYN-SENT only after copied_seq
> >  		 * is initialized. */
> > diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> > index a6ea8520e5d9..9919793e293b 100644
> > --- a/net/ipv4/tcp_output.c
> > +++ b/net/ipv4/tcp_output.c
> > @@ -697,6 +697,16 @@ static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
> >  
> >  	smc_set_option(tp, opts, &remaining);
> >  
> > +	if (tp->is_mptcp) {
> > +		u64 local_key;
> > +		if (mptcp_syn_options(sk, &local_key)) {
> > +			opts->options |= OPTION_MPTCP;
> > +			opts->suboptions |= OPTION_MPTCP_MPC_SYN;
> > +			opts->sndr_key = local_key;
> > +			remaining -= TCPOLEN_MPTCP_MPC_SYN;
> > +		}
> > +	}
> > +
> >  	return MAX_TCP_OPTION_SPACE - remaining;
> >  }
> >  
> > @@ -804,6 +814,28 @@ static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb
> >  			opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK;
> >  	}
> >  
> > +	if (tp->is_mptcp) {
> > +		struct subflow_sock *subflow = subflow_sk(sk);
> > +
> > +		pr_debug("tcp_established_options: subflow=%p", subflow);
> > +		opts->suboptions = 0;
> > +		if (subflow->mp_capable) {
> > +			const unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
> > +			pr_debug("tcp_established_options: remaining=%d", remaining);
> > +			if (!subflow->fourth_ack) {
> > +				pr_debug("tcp_established_options: OPTION_MPTCP_MPC_ACK");
> > +				if (remaining >= 20) {
> > +					opts->options |= OPTION_MPTCP;
> > +					opts->suboptions |= OPTION_MPTCP_MPC_ACK;
> > +					opts->sndr_key = subflow->local_key;
> > +					opts->rcvr_key = subflow->remote_key;
> > +					size += 20;
> > +				}
> > +				subflow->fourth_ack = 1;
> > +				// @@ also this is where first DSS goes in?
> > +			}
> > +		}
> > +	}
> >  	return size;
> >  }
> >  
> > diff --git a/net/mptcp/Makefile b/net/mptcp/Makefile
> > index 2bd18e3b9fda..3f0e7163fe80 100644
> > --- a/net/mptcp/Makefile
> > +++ b/net/mptcp/Makefile
> > @@ -1,3 +1,3 @@
> >  obj-$(CONFIG_MPTCP) += mptcp.o
> >  
> > -mptcp-y := protocol.o options.o
> > +mptcp-y := protocol.o subflow.o options.o
> > diff --git a/net/mptcp/options.c b/net/mptcp/options.c
> > index 4fd64e0bdd2e..4b1cbc3b3efe 100644
> > --- a/net/mptcp/options.c
> > +++ b/net/mptcp/options.c
> > @@ -150,3 +150,14 @@ void mptcp_get_options(const struct sk_buff *skb,
> >  		}
> >  	}
> >  }
> > +
> > +unsigned int mptcp_syn_options(struct sock *sk, u64 *local_key)
> > +{
> > +	struct subflow_sock *subflow = subflow_sk(sk);
> > +
> > +	if (subflow->request_mptcp) {
> > +		pr_debug("local_key=%llu", subflow->local_key);
> > +		*local_key = subflow->local_key;
> > +	}
> > +	return subflow->request_mptcp;
> > +}
> > diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
> > index c1eb4afc3ca4..1a3412a742ea 100644
> > --- a/net/mptcp/protocol.c
> > +++ b/net/mptcp/protocol.c
> > @@ -26,9 +26,15 @@
> >  static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
> >  {
> >  	struct mptcp_sock *msk = mptcp_sk(sk);
> > -	struct socket *subflow = msk->subflow;
> > -
> > -	pr_debug("subflow=%p", subflow->sk);
> > +	struct socket *subflow;
> > +
> > +	if (msk->connection_list) {
> > +		subflow = msk->connection_list;
> > +		pr_debug("conn_list->subflow=%p", subflow->sk);
> > +	} else {
> > +		subflow = msk->subflow;
> > +		pr_debug("subflow=%p", subflow->sk);
> > +	}
> >  
> >  	return sock_sendmsg(subflow, msg);
> >  }
> > @@ -37,9 +43,15 @@ static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
> >  			 int nonblock, int flags, int *addr_len)
> >  {
> >  	struct mptcp_sock *msk = mptcp_sk(sk);
> > -	struct socket *subflow = msk->subflow;
> > -
> > -	pr_debug("subflow=%p", subflow->sk);
> > +	struct socket *subflow;
> > +
> > +	if (msk->connection_list) {
> > +		subflow = msk->connection_list;
> > +		pr_debug("conn_list->subflow=%p", subflow->sk);
> > +	} else {
> > +		subflow = msk->subflow;
> > +		pr_debug("subflow=%p", subflow->sk);
> > +	}
> >  
> >  	return sock_recvmsg(subflow, msg, flags);
> >  }
> > @@ -47,19 +59,10 @@ static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
> >  static int mptcp_init_sock(struct sock *sk)
> >  {
> >  	struct mptcp_sock *msk = mptcp_sk(sk);
> > -	struct socket *sf;
> > -	int err;
> >  
> >  	pr_debug("msk=%p", msk);
> >  
> > -	err = sock_create_kern(&init_net, PF_INET, SOCK_STREAM, IPPROTO_TCP,
> > -			       &sf);
> > -	if (!err) {
> > -		pr_debug("subflow=%p", sf->sk);
> > -		msk->subflow = sf;
> > -	}
> > -
> > -	return err;
> > +	return 0;
> >  }
> >  
> >  static void mptcp_close(struct sock *sk, long timeout)
> > @@ -70,65 +73,171 @@ static void mptcp_close(struct sock *sk, long timeout)
> >  		pr_debug("subflow=%p", msk->subflow->sk);
> >  		sock_release(msk->subflow);
> >  	}
> > +
> > +	if (msk->connection_list) {
> > +		pr_debug("conn_list->subflow=%p", msk->connection_list->sk);
> > +		sock_release(msk->connection_list);
> > +	}
> >  }
> >  
> > -static int mptcp_connect(struct sock *sk, struct sockaddr *saddr, int len)
> > +static int mptcp_get_port(struct sock *sk, unsigned short snum)
> >  {
> >  	struct mptcp_sock *msk = mptcp_sk(sk);
> > -	int err;
> > +	struct sock *subflow = msk->subflow->sk;
> > +
> > +	pr_debug("msk=%p, subflow=%p", sk, subflow);
> >  
> > -	saddr->sa_family = AF_INET;
> > +	return inet_csk_get_port(subflow, snum);
> > +}
> >  
> > -	pr_debug("msk=%p, subflow=%p", msk, msk->subflow->sk);
> > +void mptcp_finish_connect(struct sock *sk, int mp_capable)
> > +{
> > +	struct mptcp_sock *msk = mptcp_sk(sk);
> > +	struct subflow_sock *subflow = subflow_sk(msk->subflow->sk);
> >  
> > -	err = kernel_connect(msk->subflow, saddr, len, 0);
> > +	pr_debug("msk=%p", msk);
> >  
> > +	if (mp_capable) {
> > +		msk->remote_key = subflow->remote_key;
> > +		msk->local_key = subflow->local_key;
> > +		msk->connection_list = msk->subflow;
> > +		msk->subflow = NULL;
> > +	}
> >  	sk->sk_state = TCP_ESTABLISHED;
> 
> (should we not call tcp_set_state here?)

Yes.

> 
> > +}
> >  
> > +static int subflow_create(struct sock *sock)
> > +{
> > +	struct mptcp_sock *msk = mptcp_sk(sock);
> > +	struct socket *sf;
> > +	int err;
> > +
> > +	err = sock_create_kern(&init_net, PF_INET, SOCK_STREAM, IPPROTO_SUBFLOW,
> > +			       &sf);
> > +	if (!err) {
> > +		struct subflow_sock *subflow = subflow_sk(sf->sk);
> > +		pr_debug("subflow=%p", subflow);
> > +		msk->subflow = sf;
> > +		subflow->conn = sock;
> > +		subflow->request_mptcp = 1; // @@ if MPTCP enabled
> > +		subflow->checksum = 1; // @@ if checksum enabled
> > +		subflow->version = 0;
> > +	}
> >  	return err;
> >  }
> >  
> > +int mptcp_stream_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
> > +{
> > +	struct mptcp_sock *msk = mptcp_sk(sock->sk);
> > +	struct socket *subflow = msk->subflow;
> > +
> > +	pr_debug("msk=%p, subflow=%p", msk, subflow->sk);
> > +
> > +	return inet_bind(subflow, uaddr, addr_len);
> > +}
> > +
> > +int mptcp_stream_connect(struct socket *sock, struct sockaddr *uaddr,
> 
> detail: I guess these two functions can be static
> 

OK

> > +			 int addr_len, int flags)
> > +{
> > +	struct mptcp_sock *msk = mptcp_sk(sock->sk);
> > +	int err;
> > +
> > +	pr_debug("msk=%p", msk);
> > +
> > +	if (msk->subflow == NULL) {
> > +		err = subflow_create(sock->sk);
> > +		if (err)
> > +			return err;
> > +	}
> > +
> > +	return inet_stream_connect(msk->subflow, uaddr, addr_len, flags);
> > +}
> > +
> >  static struct proto mptcp_prot = {
> >  	.name		= "MPTCP",
> >  	.owner		= THIS_MODULE,
> >  	.init		= mptcp_init_sock,
> >  	.close		= mptcp_close,
> >  	.accept		= inet_csk_accept,
> > -	.connect	= mptcp_connect,
> >  	.shutdown	= tcp_shutdown,
> >  	.sendmsg	= mptcp_sendmsg,
> >  	.recvmsg	= mptcp_recvmsg,
> >  	.hash		= inet_hash,
> >  	.unhash		= inet_unhash,
> > -	.get_port	= inet_csk_get_port,
> > +	.get_port	= mptcp_get_port,
> >  	.obj_size	= sizeof(struct mptcp_sock),
> >  	.no_autobind	= 1,
> >  };
> >  
> > +const struct proto_ops mptcp_stream_ops = {
> > +	.family		   = PF_INET,
> > +	.owner		   = THIS_MODULE,
> > +	.release	   = inet_release,
> > +	.bind		   = mptcp_stream_bind,
> > +	.connect	   = mptcp_stream_connect,
> > +	.socketpair	   = sock_no_socketpair,
> > +	.accept		   = inet_accept,
> > +	.getname	   = inet_getname,
> > +	.poll		   = tcp_poll,
> > +	.ioctl		   = inet_ioctl,
> > +	.listen		   = inet_listen,
> > +	.shutdown	   = inet_shutdown,
> > +	.setsockopt	   = sock_common_setsockopt,
> > +	.getsockopt	   = sock_common_getsockopt,
> > +	.sendmsg	   = inet_sendmsg,
> > +	.recvmsg	   = inet_recvmsg,
> > +	.mmap		   = sock_no_mmap,
> > +	.sendpage	   = inet_sendpage,
> > +	.splice_read	   = tcp_splice_read,
> > +	.read_sock	   = tcp_read_sock,
> > +	.peek_len	   = tcp_peek_len,
> > +#ifdef CONFIG_COMPAT
> > +	.compat_setsockopt = compat_sock_common_setsockopt,
> > +	.compat_getsockopt = compat_sock_common_getsockopt,
> > +	.compat_ioctl	   = inet_compat_ioctl,
> > +#endif
> > +};
> > +
> >  static struct inet_protosw mptcp_protosw = {
> >  	.type		= SOCK_STREAM,
> >  	.protocol	= IPPROTO_MPTCP,
> >  	.prot		= &mptcp_prot,
> > -	.ops		= &inet_stream_ops,
> > +	.ops		= &mptcp_stream_ops,
> > +	.flags		= INET_PROTOSW_ICSK,
> >  };
> >  
> >  static int __init mptcp_init(void)
> >  {
> >  	int err;
> >  
> > -	err = proto_register(&mptcp_prot, 1);
> > +	mptcp_prot.h.hashinfo = tcp_prot.h.hashinfo;
> > +
> > +	err = mptcp_subflow_init();
> >  	if (err)
> > -		return err;
> > +		goto subflow_failed;
> > +
> > +	err = proto_register(&mptcp_prot, 1);
> > +	if (err) {
> > +		goto proto_failed;
> > +	}
> >  
> >  	inet_register_protosw(&mptcp_protosw);
> >  
> >  	return 0;
> > +
> > +proto_failed:
> > +	mptcp_subflow_exit();
> > +
> > +subflow_failed:
> > +	return err;
> >  }
> >  
> >  static void __exit mptcp_exit(void)
> >  {
> >  	inet_unregister_protosw(&mptcp_protosw);
> >  	proto_unregister(&mptcp_prot);
> > +
> > +	mptcp_subflow_exit();
> >  }
> >  
> >  module_init(mptcp_init);
> > diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
> > new file mode 100644
> > index 000000000000..5e5fdcb3175f
> > --- /dev/null
> > +++ b/net/mptcp/subflow.c
> > @@ -0,0 +1,192 @@
> > +/*
> > + * Multipath TCP
> > + *
> > + * Copyright (c) 2017, Intel Corporation.
> > + *
> > + * This program is free software; you can redistribute it and/or modify it
> > + * under the terms and conditions of the GNU General Public License,
> > + * version 2, as published by the Free Software Foundation.
> > + *
> > + * This program is distributed in the hope it will be useful, but WITHOUT
> > + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> > + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> > + * more details.
> > + */
> > +
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/netdevice.h>
> > +#include <net/sock.h>
> > +#include <net/inet_common.h>
> > +#include <net/inet_hashtables.h>
> > +#include <net/protocol.h>
> > +#include <net/tcp.h>
> > +#include <net/mptcp.h>
> > +
> > +static int subflow_connect(struct sock *sk, struct sockaddr *saddr, int len)
> > +{
> > +	struct subflow_sock *subflow = subflow_sk(sk);
> > +
> > +	saddr->sa_family = AF_INET; // @@ presume IPv4 for now
> > +
> > +	pr_debug("subflow=%p", subflow);
> > +
> > +	return tcp_v4_connect(sk, saddr, len);
> > +}
> > +
> > +static int subflow_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
> > +{
> > +	struct subflow_sock *subflow = subflow_sk(sk);
> > +
> > +	pr_debug("subflow=%p", subflow);
> > +
> > +	return tcp_sendmsg(sk, msg, len);
> > +}
> > +
> > +static int subflow_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
> > +			   int nonblock, int flags, int *addr_len)
> > +{
> > +	struct subflow_sock *subflow = subflow_sk(sk);
> > +
> > +	pr_debug("subflow=%p", subflow);
> > +
> > +	return tcp_recvmsg(sk, msg, len, nonblock, flags, addr_len);
> > +}
> > +
> > +static void subflow_finish_connect(struct sock *sk, const struct sk_buff *skb)
> > +{
> > +	struct subflow_sock *subflow = subflow_sk(sk);
> > +
> > +	inet_sk_rx_dst_set(sk, skb);
> > +
> > +	pr_debug("subflow=%p", subflow);
> > +
> > +	if (subflow->conn) {
> > +		pr_debug("remote_key=%llu", subflow->remote_key);
> > +		mptcp_finish_connect(subflow->conn, subflow->mp_capable);
> > +		subflow->conn = NULL;
> > +	}
> > +}
> > +
> > +const struct inet_connection_sock_af_ops subflow_specific = {
> > +	.queue_xmit	   = ip_queue_xmit,
> > +	.send_check	   = tcp_v4_send_check,
> > +	.rebuild_header	   = inet_sk_rebuild_header,
> > +	.sk_rx_dst_set	   = subflow_finish_connect,
> > +	.conn_request	   = tcp_v4_conn_request,
> > +	.syn_recv_sock	   = tcp_v4_syn_recv_sock,
> > +	.net_header_len	   = sizeof(struct iphdr),
> > +	.setsockopt	   = ip_setsockopt,
> > +	.getsockopt	   = ip_getsockopt,
> > +	.addr2sockaddr	   = inet_csk_addr2sockaddr,
> > +	.sockaddr_len	   = sizeof(struct sockaddr_in),
> > +#ifdef CONFIG_COMPAT
> > +	.compat_setsockopt = compat_ip_setsockopt,
> > +	.compat_getsockopt = compat_ip_getsockopt,
> > +#endif
> > +	.mtu_reduced	   = tcp_v4_mtu_reduced,
> > +};
> > +
> > +static int subflow_init_sock(struct sock *sk)
> > +{
> > +	struct subflow_sock *subflow = subflow_sk(sk);
> > +	struct tcp_sock *tsk = tcp_sk(sk);
> > +	struct inet_connection_sock *icsk = inet_csk(sk);
> > +	int err;
> > +
> > +	pr_debug("subflow=%p", subflow);
> > +
> > +	err = tcp_v4_init_sock(sk);
> > +	if (!err) { // @@ AND mptcp is enabled
> > +		tsk->is_mptcp = 1;
> > +		icsk->icsk_af_ops = &subflow_specific;
> > +	}
> > +
> > +	return err;
> > +}
> > +
> > +static void subflow_close(struct sock *sk, long timeout)
> > +{
> > +	pr_debug("subflow=%p", sk);
> > +
> > +	tcp_close(sk, timeout);
> > +}
> > +
> > +static void subflow_destroy(struct sock *sk)
> > +{
> > +	pr_debug("subflow=%p", sk);
> > +
> > +	tcp_v4_destroy_sock(sk);
> > +}
> > +
> > +static struct proto subflow_prot = {
> > +	.name		= "SUBFLOW",
> 
> (MPTCP_SUBFLOW?)

OK.

Thanks,

Peter.

> Cheers,
> Matthieu
> 
> > +	.owner		= THIS_MODULE,
> > +	.close		= subflow_close,
> > +	.connect	= subflow_connect,
> > +	.disconnect	= tcp_disconnect,
> > +	.accept		= inet_csk_accept,
> > +	.ioctl		= tcp_ioctl,
> > +	.init		= subflow_init_sock,
> > +	.destroy	= subflow_destroy,
> > +	.shutdown	= tcp_shutdown,
> > +	.keepalive	= tcp_set_keepalive,
> > +	.recvmsg	= subflow_recvmsg,
> > +	.sendmsg	= subflow_sendmsg,
> > +	.sendpage	= tcp_sendpage,
> > +	.backlog_rcv	= tcp_v4_do_rcv,
> > +	.release_cb	= tcp_release_cb,
> > +	.hash		= inet_hash,
> > +	.unhash		= inet_unhash,
> > +	.get_port	= inet_csk_get_port,
> > +	.enter_memory_pressure	= tcp_enter_memory_pressure,
> > +	.stream_memory_free	= tcp_stream_memory_free,
> > +	.sockets_allocated	= &tcp_sockets_allocated,
> > +	.orphan_count		= &tcp_orphan_count,
> > +	.memory_allocated	= &tcp_memory_allocated,
> > +	.memory_pressure	= &tcp_memory_pressure,
> > +	.sysctl_mem		= sysctl_tcp_mem,
> > +	.sysctl_wmem_offset	= offsetof(struct net, ipv4.sysctl_tcp_wmem),
> > +	.sysctl_rmem_offset	= offsetof(struct net, ipv4.sysctl_tcp_rmem),
> > +	.max_header		= MAX_TCP_HEADER,
> > +	.obj_size		= sizeof(struct subflow_sock),
> > +	.slab_flags		= SLAB_TYPESAFE_BY_RCU,
> > +
> > +	.no_autobind		= true,
> > +};
> > +
> > +static struct inet_protosw subflow_protosw = {
> > +	.type		= SOCK_STREAM,
> > +	.protocol	= IPPROTO_SUBFLOW,
> > +	.prot		= &subflow_prot,
> > +	.ops		= &inet_stream_ops,
> > +	.flags		= INET_PROTOSW_ICSK,
> > +};
> > +
> > +int mptcp_subflow_init(void)
> > +{
> > +	int err = -ENOMEM;
> > +
> > +	/* TODO: Register path manager callbacks. */
> > +
> > +	subflow_prot.twsk_prot		= tcp_prot.twsk_prot;
> > +	subflow_prot.h.hashinfo		= tcp_prot.h.hashinfo;
> > +	err = proto_register(&subflow_prot, 1);
> > +	if (err)
> > +		goto fail;
> > +
> > +	inet_register_protosw(&subflow_protosw);
> > +
> > +	return 0;
> > +
> > +fail:
> > +	return err;
> > +}
> > +
> > +void mptcp_subflow_exit(void)
> > +{
> > +	inet_unregister_protosw(&subflow_protosw);
> > +	proto_unregister(&subflow_prot);
> > +}
> > +
> > +MODULE_LICENSE("GPL");
> > 
> 
>