Commit 783237e8 authored by Yuchung Cheng's avatar Yuchung Cheng Committed by David S. Miller
Browse files

net-tcp: Fast Open client - sending SYN-data 



This patch implements sending SYN-data in tcp_connect(). The data is
from tcp_sendmsg() with flag MSG_FASTOPEN (implemented in a later patch).

The length of the cookie in tcp_fastopen_req, init'd to 0, controls the
type of the SYN. If the cookie is not cached (len==0), the host sends
data-less SYN with Fast Open cookie request option to solicit a cookie
from the remote. If cookie is not available (len > 0), the host sends
a SYN-data with Fast Open cookie option. If cookie length is negative,
  the SYN will not include any Fast Open option (for fall back operations).

To deal with middleboxes that may drop SYN with data or experimental TCP
option, the SYN-data is only sent once. SYN retransmits do not include
data or Fast Open options. The connection will fall back to regular TCP
handshake.

Signed-off-by: default avatarYuchung Cheng <ycheng@google.com>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 1fe4c481

include/linux/snmp.h

+1 −0
Original line number Diff line number Diff line
@@ -238,6 +238,7 @@ enum 
	LINUX_MIB_TCPOFOMERGE,			/* TCPOFOMerge */

	LINUX_MIB_TCPCHALLENGEACK,		/* TCPChallengeACK */

	LINUX_MIB_TCPSYNCHALLENGE,		/* TCPSYNChallenge */

	LINUX_MIB_TCPFASTOPENACTIVE,		/* TCPFastOpenActive */

	__LINUX_MIB_MAX

};

include/linux/tcp.h

+5 −1
Original line number Diff line number Diff line
@@ -386,7 +386,8 @@ struct tcp_sock { 
		unused      : 1;

	u8	repair_queue;

	u8	do_early_retrans:1,/* Enable RFC5827 early-retransmit  */

		early_retrans_delayed:1; /* Delayed ER timer installed */

		early_retrans_delayed:1, /* Delayed ER timer installed */

		syn_fastopen:1;	/* SYN includes Fast Open option */



/* RTT measurement */

	u32	srtt;		/* smoothed round trip time << 3	*/
@@ -500,6 +501,9 @@ struct tcp_sock { 
	struct tcp_md5sig_info	__rcu *md5sig_info;

#endif



/* TCP fastopen related information */

	struct tcp_fastopen_request *fastopen_req;



	/* When the cookie options are generated and exchanged, then this

	 * object holds a reference to them (cookie_values->kref).  Also

	 * contains related tcp_cookie_transactions fields.

include/net/tcp.h

+9 −0
Original line number Diff line number Diff line
@@ -1289,6 +1289,15 @@ extern int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *, const struct sk_buff 
extern int tcp_md5_hash_key(struct tcp_md5sig_pool *hp,

			    const struct tcp_md5sig_key *key);



struct tcp_fastopen_request {

	/* Fast Open cookie. Size 0 means a cookie request */

	struct tcp_fastopen_cookie	cookie;

	struct msghdr			*data;  /* data in MSG_FASTOPEN */

	u16				copied;	/* queued in tcp_connect() */

};



void tcp_free_fastopen_req(struct tcp_sock *tp);



/* write queue abstraction */

static inline void tcp_write_queue_purge(struct sock *sk)

{

net/ipv4/af_inet.c

+8 −2
Original line number Diff line number Diff line
@@ -556,11 +556,12 @@ int inet_dgram_connect(struct socket *sock, struct sockaddr *uaddr, 
}

EXPORT_SYMBOL(inet_dgram_connect);



static long inet_wait_for_connect(struct sock *sk, long timeo)

static long inet_wait_for_connect(struct sock *sk, long timeo, int writebias)

{

	DEFINE_WAIT(wait);



	prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);

	sk->sk_write_pending += writebias;



	/* Basic assumption: if someone sets sk->sk_err, he _must_

	 * change state of the socket from TCP_SYN_*.
@@ -576,6 +577,7 @@ static long inet_wait_for_connect(struct sock *sk, long timeo) 
		prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);

	}

	finish_wait(sk_sleep(sk), &wait);

	sk->sk_write_pending -= writebias;

	return timeo;

}
@@ -634,8 +636,12 @@ int inet_stream_connect(struct socket *sock, struct sockaddr *uaddr, 
	timeo = sock_sndtimeo(sk, flags & O_NONBLOCK);



	if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {

		int writebias = (sk->sk_protocol == IPPROTO_TCP) &&

				tcp_sk(sk)->fastopen_req &&

				tcp_sk(sk)->fastopen_req->data ? 1 : 0;



		/* Error code is set above */

		if (!timeo || !inet_wait_for_connect(sk, timeo))

		if (!timeo || !inet_wait_for_connect(sk, timeo, writebias))

			goto out;



		err = sock_intr_errno(timeo);

net/ipv4/proc.c

+1 −0
Original line number Diff line number Diff line
@@ -262,6 +262,7 @@ static const struct snmp_mib snmp4_net_list[] = { 
	SNMP_MIB_ITEM("TCPOFOMerge", LINUX_MIB_TCPOFOMERGE),

	SNMP_MIB_ITEM("TCPChallengeACK", LINUX_MIB_TCPCHALLENGEACK),

	SNMP_MIB_ITEM("TCPSYNChallenge", LINUX_MIB_TCPSYNCHALLENGE),

	SNMP_MIB_ITEM("TCPFastOpenActive", LINUX_MIB_TCPFASTOPENACTIVE),

	SNMP_MIB_SENTINEL

};

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