net/dccp/output.c - kernel/msm-4.9 - Gitiles

 /*
  *  net/dccp/output.c
  *
  *  An implementation of the DCCP protocol
  *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>
  *
  *	This program is free software; you can redistribute it and/or
  *	modify it under the terms of the GNU General Public License
  *	as published by the Free Software Foundation; either version
  *	2 of the License, or (at your option) any later version.
  */

 #include <linux/dccp.h>
 #include <linux/kernel.h>
 #include <linux/skbuff.h>

 #include <net/inet_sock.h>
 #include <net/sock.h>

 #include "ackvec.h"
 #include "ccid.h"
 #include "dccp.h"

 static inline void dccp_event_ack_sent(struct sock *sk)
 {
 	inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
 }

 static void dccp_skb_entail(struct sock *sk, struct sk_buff *skb)
 {
 	skb_set_owner_w(skb, sk);
 	WARN_ON(sk->sk_send_head);
 	sk->sk_send_head = skb;
 }

 /*
  * All SKB's seen here are completely headerless. It is our
  * job to build the DCCP header, and pass the packet down to
  * IP so it can do the same plus pass the packet off to the
  * device.
  */
 static int dccp_transmit_skb(struct sock *sk, struct sk_buff *skb)
 {
 	if (likely(skb != NULL)) {
 		const struct inet_sock *inet = inet_sk(sk);
 		const struct inet_connection_sock *icsk = inet_csk(sk);
 		struct dccp_sock *dp = dccp_sk(sk);
 		struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
 		struct dccp_hdr *dh;
 		/* XXX For now we're using only 48 bits sequence numbers */
 		const u32 dccp_header_size = sizeof(*dh) +
 					     sizeof(struct dccp_hdr_ext) +
 					  dccp_packet_hdr_len(dcb->dccpd_type);
 		int err, set_ack = 1;
 		u64 ackno = dp->dccps_gsr;

 		dccp_inc_seqno(&dp->dccps_gss);

 		switch (dcb->dccpd_type) {
 		case DCCP_PKT_DATA:
 			set_ack = 0;
 			/* fall through */
 		case DCCP_PKT_DATAACK:
 			break;

 		case DCCP_PKT_REQUEST:
 			set_ack = 0;
 			/* fall through */

 		case DCCP_PKT_SYNC:
 		case DCCP_PKT_SYNCACK:
 			ackno = dcb->dccpd_seq;
 			/* fall through */
 		default:
 			/*
 			 * Only data packets should come through with skb->sk
 			 * set.
 			 */
 			WARN_ON(skb->sk);
 			skb_set_owner_w(skb, sk);
 			break;
 		}

 		dcb->dccpd_seq = dp->dccps_gss;

 		if (dccp_insert_options(sk, skb)) {
 			kfree_skb(skb);
 			return -EPROTO;
 		}


 		/* Build DCCP header and checksum it. */
 		dh = dccp_zeroed_hdr(skb, dccp_header_size);
 		dh->dccph_type	= dcb->dccpd_type;
 		dh->dccph_sport	= inet->sport;
 		dh->dccph_dport	= inet->dport;
 		dh->dccph_doff	= (dccp_header_size + dcb->dccpd_opt_len) / 4;
 		dh->dccph_ccval	= dcb->dccpd_ccval;
 		dh->dccph_cscov = dp->dccps_pcslen;
 		/* XXX For now we're using only 48 bits sequence numbers */
 		dh->dccph_x	= 1;

 		dp->dccps_awh = dp->dccps_gss;
 		dccp_hdr_set_seq(dh, dp->dccps_gss);
 		if (set_ack)
 			dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), ackno);

 		switch (dcb->dccpd_type) {
 		case DCCP_PKT_REQUEST:
 			dccp_hdr_request(skb)->dccph_req_service =
 							dp->dccps_service;
 			break;
 		case DCCP_PKT_RESET:
 			dccp_hdr_reset(skb)->dccph_reset_code =
 							dcb->dccpd_reset_code;
 			break;
 		}

 		icsk->icsk_af_ops->send_check(sk, 0, skb);

 		if (set_ack)
 			dccp_event_ack_sent(sk);

 		DCCP_INC_STATS(DCCP_MIB_OUTSEGS);

 		memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
 		err = icsk->icsk_af_ops->queue_xmit(skb, 0);
 		return net_xmit_eval(err);
 	}
 	return -ENOBUFS;
 }

 unsigned int dccp_sync_mss(struct sock *sk, u32 pmtu)
 {
 	struct inet_connection_sock *icsk = inet_csk(sk);
 	struct dccp_sock *dp = dccp_sk(sk);
 	int mss_now = (pmtu - icsk->icsk_af_ops->net_header_len -
 		       sizeof(struct dccp_hdr) - sizeof(struct dccp_hdr_ext));

 	/* Now subtract optional transport overhead */
 	mss_now -= icsk->icsk_ext_hdr_len;

 	/*
 	 * FIXME: this should come from the CCID infrastructure, where, say,
 	 * TFRC will say it wants TIMESTAMPS, ELAPSED time, etc, for now lets
 	 * put a rough estimate for NDP + TIMESTAMP + TIMESTAMP_ECHO + ELAPSED
 	 * TIME + TFRC_OPT_LOSS_EVENT_RATE + TFRC_OPT_RECEIVE_RATE + padding to
 	 * make it a multiple of 4
 	 */

 	mss_now -= ((5 + 6 + 10 + 6 + 6 + 6 + 3) / 4) * 4;

 	/* And store cached results */
 	icsk->icsk_pmtu_cookie = pmtu;
 	dp->dccps_mss_cache = mss_now;

 	return mss_now;
 }

 EXPORT_SYMBOL_GPL(dccp_sync_mss);

 void dccp_write_space(struct sock *sk)
 {
 	read_lock(&sk->sk_callback_lock);

 	if (sk->sk_sleep && waitqueue_active(sk->sk_sleep))
 		wake_up_interruptible(sk->sk_sleep);
 	/* Should agree with poll, otherwise some programs break */
 	if (sock_writeable(sk))
 		sk_wake_async(sk, 2, POLL_OUT);

 	read_unlock(&sk->sk_callback_lock);
 }

 /**
  * dccp_wait_for_ccid - Wait for ccid to tell us we can send a packet
  * @sk: socket to wait for
  */
 static int dccp_wait_for_ccid(struct sock *sk, struct sk_buff *skb)
 {
 	struct dccp_sock *dp = dccp_sk(sk);
 	DEFINE_WAIT(wait);
 	unsigned long delay;
 	int rc;

 	while (1) {
 		prepare_to_wait(sk->sk_sleep, &wait, TASK_INTERRUPTIBLE);

 		if (sk->sk_err)
 			goto do_error;
 		if (signal_pending(current))
 			goto do_interrupted;

 		rc = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb);
 		if (rc <= 0)
 			break;
 		delay = msecs_to_jiffies(rc);
 		sk->sk_write_pending++;
 		release_sock(sk);
 		schedule_timeout(delay);
 		lock_sock(sk);
 		sk->sk_write_pending--;
 	}
 out:
 	finish_wait(sk->sk_sleep, &wait);
 	return rc;

 do_error:
 	rc = -EPIPE;
 	goto out;
 do_interrupted:
 	rc = -EINTR;
 	goto out;
 }

 static void dccp_write_xmit_timer(unsigned long data) {
 	struct sock *sk = (struct sock *)data;
 	struct dccp_sock *dp = dccp_sk(sk);

 	bh_lock_sock(sk);
 	if (sock_owned_by_user(sk))
 		sk_reset_timer(sk, &dp->dccps_xmit_timer, jiffies+1);
 	else
 		dccp_write_xmit(sk, 0);
 	bh_unlock_sock(sk);
 	sock_put(sk);
 }

 void dccp_write_xmit(struct sock *sk, int block)
 {
 	struct dccp_sock *dp = dccp_sk(sk);
 	struct sk_buff *skb;

 	while ((skb = skb_peek(&sk->sk_write_queue))) {
 		int err = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb);

 		if (err > 0) {
 			if (!block) {
 				sk_reset_timer(sk, &dp->dccps_xmit_timer,
 						msecs_to_jiffies(err)+jiffies);
 				break;
 			} else
 				err = dccp_wait_for_ccid(sk, skb);
 			if (err && err != -EINTR)
 				DCCP_BUG("err=%d after dccp_wait_for_ccid", err);
 		}

 		skb_dequeue(&sk->sk_write_queue);
 		if (err == 0) {
 			struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
 			const int len = skb->len;

 			if (sk->sk_state == DCCP_PARTOPEN) {
 				/* See 8.1.5.  Handshake Completion */
 				inet_csk_schedule_ack(sk);
 				inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
 						  inet_csk(sk)->icsk_rto,
 						  DCCP_RTO_MAX);
 				dcb->dccpd_type = DCCP_PKT_DATAACK;
 			} else if (dccp_ack_pending(sk))
 				dcb->dccpd_type = DCCP_PKT_DATAACK;
 			else
 				dcb->dccpd_type = DCCP_PKT_DATA;

 			err = dccp_transmit_skb(sk, skb);
 			ccid_hc_tx_packet_sent(dp->dccps_hc_tx_ccid, sk, 0, len);
 			if (err)
 				DCCP_BUG("err=%d after ccid_hc_tx_packet_sent",
 					 err);
 		} else {
 			dccp_pr_debug("packet discarded\n");
 			kfree(skb);
 		}
 	}
 }

 int dccp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
 {
 	if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk) != 0)
 		return -EHOSTUNREACH; /* Routing failure or similar. */

 	return dccp_transmit_skb(sk, (skb_cloned(skb) ?
 				      pskb_copy(skb, GFP_ATOMIC):
 				      skb_clone(skb, GFP_ATOMIC)));
 }

 struct sk_buff *dccp_make_response(struct sock *sk, struct dst_entry *dst,
 				   struct request_sock *req)
 {
 	struct dccp_hdr *dh;
 	struct dccp_request_sock *dreq;
 	const u32 dccp_header_size = sizeof(struct dccp_hdr) +
 				     sizeof(struct dccp_hdr_ext) +
 				     sizeof(struct dccp_hdr_response);
 	struct sk_buff *skb = sock_wmalloc(sk, sk->sk_prot->max_header, 1,
 					   GFP_ATOMIC);
 	if (skb == NULL)
 		return NULL;

 	/* Reserve space for headers. */
 	skb_reserve(skb, sk->sk_prot->max_header);

 	skb->dst = dst_clone(dst);

 	dreq = dccp_rsk(req);
 	if (inet_rsk(req)->acked)	/* increase ISS upon retransmission */
 		dccp_inc_seqno(&dreq->dreq_iss);
 	DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_RESPONSE;
 	DCCP_SKB_CB(skb)->dccpd_seq  = dreq->dreq_iss;

 	if (dccp_insert_options(sk, skb)) {
 		kfree_skb(skb);
 		return NULL;
 	}

 	/* Build and checksum header */
 	dh = dccp_zeroed_hdr(skb, dccp_header_size);

 	dh->dccph_sport	= inet_sk(sk)->sport;
 	dh->dccph_dport	= inet_rsk(req)->rmt_port;
 	dh->dccph_doff	= (dccp_header_size +
 			   DCCP_SKB_CB(skb)->dccpd_opt_len) / 4;
 	dh->dccph_type	= DCCP_PKT_RESPONSE;
 	dh->dccph_x	= 1;
 	dccp_hdr_set_seq(dh, dreq->dreq_iss);
 	dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dreq->dreq_isr);
 	dccp_hdr_response(skb)->dccph_resp_service = dreq->dreq_service;

 	dccp_csum_outgoing(skb);

 	/* We use `acked' to remember that a Response was already sent. */
 	inet_rsk(req)->acked = 1;
 	DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
 	return skb;
 }

 EXPORT_SYMBOL_GPL(dccp_make_response);

 static struct sk_buff *dccp_make_reset(struct sock *sk, struct dst_entry *dst,
 				       const enum dccp_reset_codes code)
 {
 	struct dccp_hdr *dh;
 	struct dccp_sock *dp = dccp_sk(sk);
 	const u32 dccp_header_size = sizeof(struct dccp_hdr) +
 				     sizeof(struct dccp_hdr_ext) +
 				     sizeof(struct dccp_hdr_reset);
 	struct sk_buff *skb = sock_wmalloc(sk, sk->sk_prot->max_header, 1,
 					   GFP_ATOMIC);
 	if (skb == NULL)
 		return NULL;

 	/* Reserve space for headers. */
 	skb_reserve(skb, sk->sk_prot->max_header);

 	skb->dst = dst_clone(dst);

 	dccp_inc_seqno(&dp->dccps_gss);

 	DCCP_SKB_CB(skb)->dccpd_reset_code = code;
 	DCCP_SKB_CB(skb)->dccpd_type	   = DCCP_PKT_RESET;
 	DCCP_SKB_CB(skb)->dccpd_seq	   = dp->dccps_gss;

 	if (dccp_insert_options(sk, skb)) {
 		kfree_skb(skb);
 		return NULL;
 	}

 	dh = dccp_zeroed_hdr(skb, dccp_header_size);

 	dh->dccph_sport	= inet_sk(sk)->sport;
 	dh->dccph_dport	= inet_sk(sk)->dport;
 	dh->dccph_doff	= (dccp_header_size +
 			   DCCP_SKB_CB(skb)->dccpd_opt_len) / 4;
 	dh->dccph_type	= DCCP_PKT_RESET;
 	dh->dccph_x	= 1;
 	dccp_hdr_set_seq(dh, dp->dccps_gss);
 	dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dp->dccps_gsr);

 	dccp_hdr_reset(skb)->dccph_reset_code = code;
 	inet_csk(sk)->icsk_af_ops->send_check(sk, 0, skb);

 	DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
 	return skb;
 }

 int dccp_send_reset(struct sock *sk, enum dccp_reset_codes code)
 {
 	/*
 	 * FIXME: what if rebuild_header fails?
 	 * Should we be doing a rebuild_header here?
 	 */
 	int err = inet_sk_rebuild_header(sk);

 	if (err == 0) {
 		struct sk_buff *skb = dccp_make_reset(sk, sk->sk_dst_cache,
 						      code);
 		if (skb != NULL) {
 			memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
 			err = inet_csk(sk)->icsk_af_ops->queue_xmit(skb, 0);
 			return net_xmit_eval(err);
 		}
 	}

 	return err;
 }

 /*
  * Do all connect socket setups that can be done AF independent.
  */
 static inline void dccp_connect_init(struct sock *sk)
 {
 	struct dccp_sock *dp = dccp_sk(sk);
 	struct dst_entry *dst = __sk_dst_get(sk);
 	struct inet_connection_sock *icsk = inet_csk(sk);

 	sk->sk_err = 0;
 	sock_reset_flag(sk, SOCK_DONE);

 	dccp_sync_mss(sk, dst_mtu(dst));

 	/*
 	 * SWL and AWL are initially adjusted so that they are not less than
 	 * the initial Sequence Numbers received and sent, respectively:
 	 *	SWL := max(GSR + 1 - floor(W/4), ISR),
 	 *	AWL := max(GSS - W' + 1, ISS).
 	 * These adjustments MUST be applied only at the beginning of the
 	 * connection.
 	 */
 	dccp_update_gss(sk, dp->dccps_iss);
 	dccp_set_seqno(&dp->dccps_awl, max48(dp->dccps_awl, dp->dccps_iss));

 	/* S.GAR - greatest valid acknowledgement number received on a non-Sync;
 	 *         initialized to S.ISS (sec. 8.5)                            */
 	dp->dccps_gar = dp->dccps_iss;

 	icsk->icsk_retransmits = 0;
 	init_timer(&dp->dccps_xmit_timer);
 	dp->dccps_xmit_timer.data = (unsigned long)sk;
 	dp->dccps_xmit_timer.function = dccp_write_xmit_timer;
 }

 int dccp_connect(struct sock *sk)
 {
 	struct sk_buff *skb;
 	struct inet_connection_sock *icsk = inet_csk(sk);

 	dccp_connect_init(sk);

 	skb = alloc_skb(sk->sk_prot->max_header, sk->sk_allocation);
 	if (unlikely(skb == NULL))
 		return -ENOBUFS;

 	/* Reserve space for headers. */
 	skb_reserve(skb, sk->sk_prot->max_header);

 	DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_REQUEST;

 	dccp_skb_entail(sk, skb);
 	dccp_transmit_skb(sk, skb_clone(skb, GFP_KERNEL));
 	DCCP_INC_STATS(DCCP_MIB_ACTIVEOPENS);

 	/* Timer for repeating the REQUEST until an answer. */
 	inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
 				  icsk->icsk_rto, DCCP_RTO_MAX);
 	return 0;
 }

 EXPORT_SYMBOL_GPL(dccp_connect);

 void dccp_send_ack(struct sock *sk)
 {
 	/* If we have been reset, we may not send again. */
 	if (sk->sk_state != DCCP_CLOSED) {
 		struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header,
 						GFP_ATOMIC);

 		if (skb == NULL) {
 			inet_csk_schedule_ack(sk);
 			inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
 			inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
 						  TCP_DELACK_MAX,
 						  DCCP_RTO_MAX);
 			return;
 		}

 		/* Reserve space for headers */
 		skb_reserve(skb, sk->sk_prot->max_header);
 		DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_ACK;
 		dccp_transmit_skb(sk, skb);
 	}
 }

 EXPORT_SYMBOL_GPL(dccp_send_ack);

 void dccp_send_delayed_ack(struct sock *sk)
 {
 	struct inet_connection_sock *icsk = inet_csk(sk);
 	/*
 	 * FIXME: tune this timer. elapsed time fixes the skew, so no problem
 	 * with using 2s, and active senders also piggyback the ACK into a
 	 * DATAACK packet, so this is really for quiescent senders.
 	 */
 	unsigned long timeout = jiffies + 2 * HZ;

 	/* Use new timeout only if there wasn't a older one earlier. */
 	if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
 		/* If delack timer was blocked or is about to expire,
 		 * send ACK now.
 		 *
 		 * FIXME: check the "about to expire" part
 		 */
 		if (icsk->icsk_ack.blocked) {
 			dccp_send_ack(sk);
 			return;
 		}

 		if (!time_before(timeout, icsk->icsk_ack.timeout))
 			timeout = icsk->icsk_ack.timeout;
 	}
 	icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
 	icsk->icsk_ack.timeout = timeout;
 	sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
 }

 void dccp_send_sync(struct sock *sk, const u64 seq,
 		    const enum dccp_pkt_type pkt_type)
 {
 	/*
 	 * We are not putting this on the write queue, so
 	 * dccp_transmit_skb() will set the ownership to this
 	 * sock.
 	 */
 	struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header, GFP_ATOMIC);

 	if (skb == NULL)
 		/* FIXME: how to make sure the sync is sent? */
 		return;

 	/* Reserve space for headers and prepare control bits. */
 	skb_reserve(skb, sk->sk_prot->max_header);
 	DCCP_SKB_CB(skb)->dccpd_type = pkt_type;
 	DCCP_SKB_CB(skb)->dccpd_seq = seq;

 	dccp_transmit_skb(sk, skb);
 }

 EXPORT_SYMBOL_GPL(dccp_send_sync);

 /*
  * Send a DCCP_PKT_CLOSE/CLOSEREQ. The caller locks the socket for us. This
  * cannot be allowed to fail queueing a DCCP_PKT_CLOSE/CLOSEREQ frame under
  * any circumstances.
  */
 void dccp_send_close(struct sock *sk, const int active)
 {
 	struct dccp_sock *dp = dccp_sk(sk);
 	struct sk_buff *skb;
 	const gfp_t prio = active ? GFP_KERNEL : GFP_ATOMIC;

 	skb = alloc_skb(sk->sk_prot->max_header, prio);
 	if (skb == NULL)
 		return;

 	/* Reserve space for headers and prepare control bits. */
 	skb_reserve(skb, sk->sk_prot->max_header);
 	DCCP_SKB_CB(skb)->dccpd_type = dp->dccps_role == DCCP_ROLE_CLIENT ?
 					DCCP_PKT_CLOSE : DCCP_PKT_CLOSEREQ;

 	if (active) {
 		dccp_write_xmit(sk, 1);
 		dccp_skb_entail(sk, skb);
 		dccp_transmit_skb(sk, skb_clone(skb, prio));
 		/* FIXME do we need a retransmit timer here? */
 	} else
 		dccp_transmit_skb(sk, skb);
 }
	/*
	* net/dccp/output.c
	*
	* An implementation of the DCCP protocol
	* Arnaldo Carvalho de Melo <acme@conectiva.com.br>
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public License
	* as published by the Free Software Foundation; either version
	* 2 of the License, or (at your option) any later version.
	*/

	#include <linux/dccp.h>
	#include <linux/kernel.h>
	#include <linux/skbuff.h>

	#include <net/inet_sock.h>
	#include <net/sock.h>

	#include "ackvec.h"
	#include "ccid.h"
	#include "dccp.h"

	static inline void dccp_event_ack_sent(struct sock *sk)
	{
	inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
	}

	static void dccp_skb_entail(struct sock sk, struct sk_buff skb)
	{
	skb_set_owner_w(skb, sk);
	WARN_ON(sk->sk_send_head);
	sk->sk_send_head = skb;
	}

	/*
	* All SKB's seen here are completely headerless. It is our
	* job to build the DCCP header, and pass the packet down to
	* IP so it can do the same plus pass the packet off to the
	* device.
	*/
	static int dccp_transmit_skb(struct sock sk, struct sk_buff skb)
	{
	if (likely(skb != NULL)) {
	const struct inet_sock *inet = inet_sk(sk);
	const struct inet_connection_sock *icsk = inet_csk(sk);
	struct dccp_sock *dp = dccp_sk(sk);
	struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
	struct dccp_hdr *dh;
	/* XXX For now we're using only 48 bits sequence numbers */
	const u32 dccp_header_size = sizeof(*dh) +
	sizeof(struct dccp_hdr_ext) +
	dccp_packet_hdr_len(dcb->dccpd_type);
	int err, set_ack = 1;
	u64 ackno = dp->dccps_gsr;

	dccp_inc_seqno(&dp->dccps_gss);

	switch (dcb->dccpd_type) {
	case DCCP_PKT_DATA:
	set_ack = 0;
	/* fall through */
	case DCCP_PKT_DATAACK:
	break;

	case DCCP_PKT_REQUEST:
	set_ack = 0;
	/* fall through */

	case DCCP_PKT_SYNC:
	case DCCP_PKT_SYNCACK:
	ackno = dcb->dccpd_seq;
	/* fall through */
	default:
	/*
	* Only data packets should come through with skb->sk
	* set.
	*/
	WARN_ON(skb->sk);
	skb_set_owner_w(skb, sk);
	break;
	}

	dcb->dccpd_seq = dp->dccps_gss;

	if (dccp_insert_options(sk, skb)) {
	kfree_skb(skb);
	return -EPROTO;
	}


	/* Build DCCP header and checksum it. */
	dh = dccp_zeroed_hdr(skb, dccp_header_size);
	dh->dccph_type = dcb->dccpd_type;
	dh->dccph_sport = inet->sport;
	dh->dccph_dport = inet->dport;
	dh->dccph_doff = (dccp_header_size + dcb->dccpd_opt_len) / 4;
	dh->dccph_ccval = dcb->dccpd_ccval;
	dh->dccph_cscov = dp->dccps_pcslen;
	/* XXX For now we're using only 48 bits sequence numbers */
	dh->dccph_x = 1;

	dp->dccps_awh = dp->dccps_gss;
	dccp_hdr_set_seq(dh, dp->dccps_gss);
	if (set_ack)
	dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), ackno);

	switch (dcb->dccpd_type) {
	case DCCP_PKT_REQUEST:
	dccp_hdr_request(skb)->dccph_req_service =
	dp->dccps_service;
	break;
	case DCCP_PKT_RESET:
	dccp_hdr_reset(skb)->dccph_reset_code =
	dcb->dccpd_reset_code;
	break;
	}

	icsk->icsk_af_ops->send_check(sk, 0, skb);

	if (set_ack)
	dccp_event_ack_sent(sk);

	DCCP_INC_STATS(DCCP_MIB_OUTSEGS);

	memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
	err = icsk->icsk_af_ops->queue_xmit(skb, 0);
	return net_xmit_eval(err);
	}
	return -ENOBUFS;
	}

	unsigned int dccp_sync_mss(struct sock *sk, u32 pmtu)
	{
	struct inet_connection_sock *icsk = inet_csk(sk);
	struct dccp_sock *dp = dccp_sk(sk);
	int mss_now = (pmtu - icsk->icsk_af_ops->net_header_len -
	sizeof(struct dccp_hdr) - sizeof(struct dccp_hdr_ext));

	/* Now subtract optional transport overhead */
	mss_now -= icsk->icsk_ext_hdr_len;

	/*
	* FIXME: this should come from the CCID infrastructure, where, say,
	* TFRC will say it wants TIMESTAMPS, ELAPSED time, etc, for now lets
	* put a rough estimate for NDP + TIMESTAMP + TIMESTAMP_ECHO + ELAPSED
	* TIME + TFRC_OPT_LOSS_EVENT_RATE + TFRC_OPT_RECEIVE_RATE + padding to
	* make it a multiple of 4
	*/

	mss_now -= ((5 + 6 + 10 + 6 + 6 + 6 + 3) / 4) * 4;

	/* And store cached results */
	icsk->icsk_pmtu_cookie = pmtu;
	dp->dccps_mss_cache = mss_now;

	return mss_now;
	}

	EXPORT_SYMBOL_GPL(dccp_sync_mss);

	void dccp_write_space(struct sock *sk)
	{
	read_lock(&sk->sk_callback_lock);

	if (sk->sk_sleep && waitqueue_active(sk->sk_sleep))
	wake_up_interruptible(sk->sk_sleep);
	/* Should agree with poll, otherwise some programs break */
	if (sock_writeable(sk))
	sk_wake_async(sk, 2, POLL_OUT);

	read_unlock(&sk->sk_callback_lock);
	}

	/**
	* dccp_wait_for_ccid - Wait for ccid to tell us we can send a packet
	* @sk: socket to wait for
	*/
	static int dccp_wait_for_ccid(struct sock sk, struct sk_buff skb)
	{
	struct dccp_sock *dp = dccp_sk(sk);
	DEFINE_WAIT(wait);
	unsigned long delay;
	int rc;

	while (1) {
	prepare_to_wait(sk->sk_sleep, &wait, TASK_INTERRUPTIBLE);

	if (sk->sk_err)
	goto do_error;
	if (signal_pending(current))
	goto do_interrupted;

	rc = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb);
	if (rc <= 0)
	break;
	delay = msecs_to_jiffies(rc);
	sk->sk_write_pending++;
	release_sock(sk);
	schedule_timeout(delay);
	lock_sock(sk);
	sk->sk_write_pending--;
	}
	out:
	finish_wait(sk->sk_sleep, &wait);
	return rc;

	do_error:
	rc = -EPIPE;
	goto out;
	do_interrupted:
	rc = -EINTR;
	goto out;
	}

	static void dccp_write_xmit_timer(unsigned long data) {
	struct sock sk = (struct sock )data;
	struct dccp_sock *dp = dccp_sk(sk);

	bh_lock_sock(sk);
	if (sock_owned_by_user(sk))
	sk_reset_timer(sk, &dp->dccps_xmit_timer, jiffies+1);
	else
	dccp_write_xmit(sk, 0);
	bh_unlock_sock(sk);
	sock_put(sk);
	}

	void dccp_write_xmit(struct sock *sk, int block)
	{
	struct dccp_sock *dp = dccp_sk(sk);
	struct sk_buff *skb;

	while ((skb = skb_peek(&sk->sk_write_queue))) {
	int err = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb);

	if (err > 0) {
	if (!block) {
	sk_reset_timer(sk, &dp->dccps_xmit_timer,
	msecs_to_jiffies(err)+jiffies);
	break;
	} else
	err = dccp_wait_for_ccid(sk, skb);
	if (err && err != -EINTR)
	DCCP_BUG("err=%d after dccp_wait_for_ccid", err);
	}

	skb_dequeue(&sk->sk_write_queue);
	if (err == 0) {
	struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
	const int len = skb->len;

	if (sk->sk_state == DCCP_PARTOPEN) {
	/* See 8.1.5. Handshake Completion */
	inet_csk_schedule_ack(sk);
	inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
	inet_csk(sk)->icsk_rto,
	DCCP_RTO_MAX);
	dcb->dccpd_type = DCCP_PKT_DATAACK;
	} else if (dccp_ack_pending(sk))
	dcb->dccpd_type = DCCP_PKT_DATAACK;
	else
	dcb->dccpd_type = DCCP_PKT_DATA;

	err = dccp_transmit_skb(sk, skb);
	ccid_hc_tx_packet_sent(dp->dccps_hc_tx_ccid, sk, 0, len);
	if (err)
	DCCP_BUG("err=%d after ccid_hc_tx_packet_sent",
	err);
	} else {
	dccp_pr_debug("packet discarded\n");
	kfree(skb);
	}
	}
	}

	int dccp_retransmit_skb(struct sock sk, struct sk_buff skb)
	{
	if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk) != 0)
	return -EHOSTUNREACH; /* Routing failure or similar. */

	return dccp_transmit_skb(sk, (skb_cloned(skb) ?
	pskb_copy(skb, GFP_ATOMIC):
	skb_clone(skb, GFP_ATOMIC)));
	}

	struct sk_buff dccp_make_response(struct sock sk, struct dst_entry *dst,
	struct request_sock *req)
	{
	struct dccp_hdr *dh;
	struct dccp_request_sock *dreq;
	const u32 dccp_header_size = sizeof(struct dccp_hdr) +
	sizeof(struct dccp_hdr_ext) +
	sizeof(struct dccp_hdr_response);
	struct sk_buff *skb = sock_wmalloc(sk, sk->sk_prot->max_header, 1,
	GFP_ATOMIC);
	if (skb == NULL)
	return NULL;

	/* Reserve space for headers. */
	skb_reserve(skb, sk->sk_prot->max_header);

	skb->dst = dst_clone(dst);

	dreq = dccp_rsk(req);
	if (inet_rsk(req)->acked) /* increase ISS upon retransmission */
	dccp_inc_seqno(&dreq->dreq_iss);
	DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_RESPONSE;
	DCCP_SKB_CB(skb)->dccpd_seq = dreq->dreq_iss;

	if (dccp_insert_options(sk, skb)) {
	kfree_skb(skb);
	return NULL;
	}

	/* Build and checksum header */
	dh = dccp_zeroed_hdr(skb, dccp_header_size);

	dh->dccph_sport = inet_sk(sk)->sport;
	dh->dccph_dport = inet_rsk(req)->rmt_port;
	dh->dccph_doff = (dccp_header_size +
	DCCP_SKB_CB(skb)->dccpd_opt_len) / 4;
	dh->dccph_type = DCCP_PKT_RESPONSE;
	dh->dccph_x = 1;
	dccp_hdr_set_seq(dh, dreq->dreq_iss);
	dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dreq->dreq_isr);
	dccp_hdr_response(skb)->dccph_resp_service = dreq->dreq_service;

	dccp_csum_outgoing(skb);

	/* We use `acked' to remember that a Response was already sent. */
	inet_rsk(req)->acked = 1;
	DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
	return skb;
	}

	EXPORT_SYMBOL_GPL(dccp_make_response);

	static struct sk_buff dccp_make_reset(struct sock sk, struct dst_entry *dst,
	const enum dccp_reset_codes code)
	{
	struct dccp_hdr *dh;
	struct dccp_sock *dp = dccp_sk(sk);
	const u32 dccp_header_size = sizeof(struct dccp_hdr) +
	sizeof(struct dccp_hdr_ext) +
	sizeof(struct dccp_hdr_reset);
	struct sk_buff *skb = sock_wmalloc(sk, sk->sk_prot->max_header, 1,
	GFP_ATOMIC);
	if (skb == NULL)
	return NULL;

	/* Reserve space for headers. */
	skb_reserve(skb, sk->sk_prot->max_header);

	skb->dst = dst_clone(dst);

	dccp_inc_seqno(&dp->dccps_gss);

	DCCP_SKB_CB(skb)->dccpd_reset_code = code;
	DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_RESET;
	DCCP_SKB_CB(skb)->dccpd_seq = dp->dccps_gss;

	if (dccp_insert_options(sk, skb)) {
	kfree_skb(skb);
	return NULL;
	}

	dh = dccp_zeroed_hdr(skb, dccp_header_size);

	dh->dccph_sport = inet_sk(sk)->sport;
	dh->dccph_dport = inet_sk(sk)->dport;
	dh->dccph_doff = (dccp_header_size +
	DCCP_SKB_CB(skb)->dccpd_opt_len) / 4;
	dh->dccph_type = DCCP_PKT_RESET;
	dh->dccph_x = 1;
	dccp_hdr_set_seq(dh, dp->dccps_gss);
	dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dp->dccps_gsr);

	dccp_hdr_reset(skb)->dccph_reset_code = code;
	inet_csk(sk)->icsk_af_ops->send_check(sk, 0, skb);

	DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
	return skb;
	}

	int dccp_send_reset(struct sock *sk, enum dccp_reset_codes code)
	{
	/*
	* FIXME: what if rebuild_header fails?
	* Should we be doing a rebuild_header here?
	*/
	int err = inet_sk_rebuild_header(sk);

	if (err == 0) {
	struct sk_buff *skb = dccp_make_reset(sk, sk->sk_dst_cache,
	code);
	if (skb != NULL) {
	memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
	err = inet_csk(sk)->icsk_af_ops->queue_xmit(skb, 0);
	return net_xmit_eval(err);
	}
	}

	return err;
	}

	/*
	* Do all connect socket setups that can be done AF independent.
	*/
	static inline void dccp_connect_init(struct sock *sk)
	{
	struct dccp_sock *dp = dccp_sk(sk);
	struct dst_entry *dst = __sk_dst_get(sk);
	struct inet_connection_sock *icsk = inet_csk(sk);

	sk->sk_err = 0;
	sock_reset_flag(sk, SOCK_DONE);

	dccp_sync_mss(sk, dst_mtu(dst));

	/*
	* SWL and AWL are initially adjusted so that they are not less than
	* the initial Sequence Numbers received and sent, respectively:
	* SWL := max(GSR + 1 - floor(W/4), ISR),
	* AWL := max(GSS - W' + 1, ISS).
	* These adjustments MUST be applied only at the beginning of the
	* connection.
	*/
	dccp_update_gss(sk, dp->dccps_iss);
	dccp_set_seqno(&dp->dccps_awl, max48(dp->dccps_awl, dp->dccps_iss));

	/* S.GAR - greatest valid acknowledgement number received on a non-Sync;
	* initialized to S.ISS (sec. 8.5) */
	dp->dccps_gar = dp->dccps_iss;

	icsk->icsk_retransmits = 0;
	init_timer(&dp->dccps_xmit_timer);
	dp->dccps_xmit_timer.data = (unsigned long)sk;
	dp->dccps_xmit_timer.function = dccp_write_xmit_timer;
	}

	int dccp_connect(struct sock *sk)
	{
	struct sk_buff *skb;
	struct inet_connection_sock *icsk = inet_csk(sk);

	dccp_connect_init(sk);

	skb = alloc_skb(sk->sk_prot->max_header, sk->sk_allocation);
	if (unlikely(skb == NULL))
	return -ENOBUFS;

	/* Reserve space for headers. */
	skb_reserve(skb, sk->sk_prot->max_header);

	DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_REQUEST;

	dccp_skb_entail(sk, skb);
	dccp_transmit_skb(sk, skb_clone(skb, GFP_KERNEL));
	DCCP_INC_STATS(DCCP_MIB_ACTIVEOPENS);

	/* Timer for repeating the REQUEST until an answer. */
	inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
	icsk->icsk_rto, DCCP_RTO_MAX);
	return 0;
	}

	EXPORT_SYMBOL_GPL(dccp_connect);

	void dccp_send_ack(struct sock *sk)
	{
	/* If we have been reset, we may not send again. */
	if (sk->sk_state != DCCP_CLOSED) {
	struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header,
	GFP_ATOMIC);

	if (skb == NULL) {
	inet_csk_schedule_ack(sk);
	inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
	inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
	TCP_DELACK_MAX,
	DCCP_RTO_MAX);
	return;
	}

	/* Reserve space for headers */
	skb_reserve(skb, sk->sk_prot->max_header);
	DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_ACK;
	dccp_transmit_skb(sk, skb);
	}
	}

	EXPORT_SYMBOL_GPL(dccp_send_ack);

	void dccp_send_delayed_ack(struct sock *sk)
	{
	struct inet_connection_sock *icsk = inet_csk(sk);
	/*
	* FIXME: tune this timer. elapsed time fixes the skew, so no problem
	* with using 2s, and active senders also piggyback the ACK into a
	* DATAACK packet, so this is really for quiescent senders.
	*/
	unsigned long timeout = jiffies + 2 * HZ;

	/* Use new timeout only if there wasn't a older one earlier. */
	if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
	/* If delack timer was blocked or is about to expire,
	* send ACK now.
	*
	* FIXME: check the "about to expire" part
	*/
	if (icsk->icsk_ack.blocked) {
	dccp_send_ack(sk);
	return;
	}

	if (!time_before(timeout, icsk->icsk_ack.timeout))
	timeout = icsk->icsk_ack.timeout;
	}
	icsk->icsk_ack.pending \|= ICSK_ACK_SCHED \| ICSK_ACK_TIMER;
	icsk->icsk_ack.timeout = timeout;
	sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
	}

	void dccp_send_sync(struct sock *sk, const u64 seq,
	const enum dccp_pkt_type pkt_type)
	{
	/*
	* We are not putting this on the write queue, so
	* dccp_transmit_skb() will set the ownership to this
	* sock.
	*/
	struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header, GFP_ATOMIC);

	if (skb == NULL)
	/* FIXME: how to make sure the sync is sent? */
	return;

	/* Reserve space for headers and prepare control bits. */
	skb_reserve(skb, sk->sk_prot->max_header);
	DCCP_SKB_CB(skb)->dccpd_type = pkt_type;
	DCCP_SKB_CB(skb)->dccpd_seq = seq;

	dccp_transmit_skb(sk, skb);
	}

	EXPORT_SYMBOL_GPL(dccp_send_sync);

	/*
	* Send a DCCP_PKT_CLOSE/CLOSEREQ. The caller locks the socket for us. This
	* cannot be allowed to fail queueing a DCCP_PKT_CLOSE/CLOSEREQ frame under
	* any circumstances.
	*/
	void dccp_send_close(struct sock *sk, const int active)
	{
	struct dccp_sock *dp = dccp_sk(sk);
	struct sk_buff *skb;
	const gfp_t prio = active ? GFP_KERNEL : GFP_ATOMIC;

	skb = alloc_skb(sk->sk_prot->max_header, prio);
	if (skb == NULL)
	return;

	/* Reserve space for headers and prepare control bits. */
	skb_reserve(skb, sk->sk_prot->max_header);
	DCCP_SKB_CB(skb)->dccpd_type = dp->dccps_role == DCCP_ROLE_CLIENT ?
	DCCP_PKT_CLOSE : DCCP_PKT_CLOSEREQ;

	if (active) {
	dccp_write_xmit(sk, 1);
	dccp_skb_entail(sk, skb);
	dccp_transmit_skb(sk, skb_clone(skb, prio));
	/* FIXME do we need a retransmit timer here? */
	} else
	dccp_transmit_skb(sk, skb);
	}