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Commit dc841e30 authored by Gerrit Renker's avatar Gerrit Renker Committed by David S. Miller
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dccp: Extend CCID packet dequeueing interface 



This extends the packet dequeuing interface of dccp_write_xmit() to allow
 1. CCIDs to take care of timing when the next packet may be sent;
 2. delayed sending (as before, with an inter-packet gap up to 65.535 seconds).

The main purpose is to take CCID-2 out of its polling mode (when it is network-
limited, it tries every millisecond to send, without interruption).

The mode of operation for (2) is as follows:
 * new packet is enqueued via dccp_sendmsg() => dccp_write_xmit(),
 * ccid_hc_tx_send_packet() detects that it may not send (e.g. window full),
 * it signals this condition via `CCID_PACKET_WILL_DEQUEUE_LATER',
 * dccp_write_xmit() returns without further action;
 * after some time the wait-condition for CCID becomes true,
 * that CCID schedules the tasklet,
 * tasklet function calls ccid_hc_tx_send_packet() via dccp_write_xmit(),
 * since the wait-condition is now true, ccid_hc_tx_packet() returns "send now",
 * packet is sent, and possibly more (since dccp_write_xmit() loops).

Code reuse: the taskled function calls dccp_write_xmit(), the timer function
            reduces to a wrapper around the same code.

Signed-off-by: default avatarGerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent fe84f414

include/linux/dccp.h

+3 −1
Original line number Diff line number Diff line
@@ -462,7 +462,8 @@ struct dccp_ackvec; 
 * @dccps_hc_rx_insert_options - receiver wants to add options when acking

 * @dccps_hc_tx_insert_options - sender wants to add options when sending

 * @dccps_server_timewait - server holds timewait state on close (RFC 4340, 8.3)

 * @dccps_xmit_timer - timer for when CCID is not ready to send

 * @dccps_xmitlet - tasklet scheduled by the TX CCID to dequeue data packets

 * @dccps_xmit_timer - used by the TX CCID to delay sending (rate-based pacing)

 * @dccps_syn_rtt - RTT sample from Request/Response exchange (in usecs)

 */

struct dccp_sock {
@@ -502,6 +503,7 @@ struct dccp_sock { 
	__u8				dccps_hc_rx_insert_options:1;

	__u8				dccps_hc_tx_insert_options:1;

	__u8				dccps_server_timewait:1;

	struct tasklet_struct		dccps_xmitlet;

	struct timer_list		dccps_xmit_timer;

};

net/dccp/output.c

+72 −46
Original line number Diff line number Diff line
@@ -254,29 +254,19 @@ do_interrupted: 
	goto out;

}



void dccp_write_xmit(struct sock *sk, int block)

/**

 * dccp_xmit_packet  -  Send data packet under control of CCID

 * Transmits next-queued payload and informs CCID to account for the packet.

 */

static void dccp_xmit_packet(struct sock *sk)

{

	int err, len;

	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, err);

			if (err && err != -EINTR)

				DCCP_BUG("err=%d after dccp_wait_for_ccid", err);

		}

	struct sk_buff *skb = skb_dequeue(&sk->sk_write_queue);



		skb_dequeue(&sk->sk_write_queue);

		if (err == 0) {

			struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);

			const int len = skb->len;

	if (unlikely(skb == NULL))

		return;

	len = skb->len;



	if (sk->sk_state == DCCP_PARTOPEN) {

		const u32 cur_mps = dp->dccps_mss_cache - DCCP_FEATNEG_OVERHEAD;
@@ -297,20 +287,56 @@ void dccp_write_xmit(struct sock *sk, int block) 
		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;

		DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_DATAACK;

	} else if (dccp_ack_pending(sk)) {

		DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_DATAACK;

	} else {

		DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_DATA;

	}



	err = dccp_transmit_skb(sk, skb);

			ccid_hc_tx_packet_sent(dp->dccps_hc_tx_ccid, sk, len);

	if (err)

				DCCP_BUG("err=%d after ccid_hc_tx_packet_sent",

					 err);

		} else {

			dccp_pr_debug("packet discarded due to err=%d\n", err);

		dccp_pr_debug("transmit_skb() returned err=%d\n", err);

	/*

	 * Register this one as sent even if an error occurred. To the remote

	 * end a local packet drop is indistinguishable from network loss, i.e.

	 * any local drop will eventually be reported via receiver feedback.

	 */

	ccid_hc_tx_packet_sent(dp->dccps_hc_tx_ccid, sk, len);

}



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 rc = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb);



		switch (ccid_packet_dequeue_eval(rc)) {

		case CCID_PACKET_WILL_DEQUEUE_LATER:

			return;

		case CCID_PACKET_DELAY:

			if (!block) {

				sk_reset_timer(sk, &dp->dccps_xmit_timer,

						msecs_to_jiffies(rc)+jiffies);

				return;

			}

			rc = dccp_wait_for_ccid(sk, skb, rc);

			if (rc && rc != -EINTR) {

				DCCP_BUG("err=%d after dccp_wait_for_ccid", rc);

				skb_dequeue(&sk->sk_write_queue);

				kfree_skb(skb);

				break;

			}

			/* fall through */

		case CCID_PACKET_SEND_AT_ONCE:

			dccp_xmit_packet(sk);

			break;

		case CCID_PACKET_ERR:

			skb_dequeue(&sk->sk_write_queue);

			kfree_skb(skb);

			dccp_pr_debug("packet discarded due to err=%d\n", rc);

		}

	}

}

net/dccp/timer.c

+14 −11
Original line number Diff line number Diff line
@@ -237,32 +237,35 @@ out: 
	sock_put(sk);

}



/* Transmit-delay timer: used by the CCIDs to delay actual send time */

static void dccp_write_xmit_timer(unsigned long data)

/**

 * dccp_write_xmitlet  -  Workhorse for CCID packet dequeueing interface

 * See the comments above %ccid_dequeueing_decision for supported modes.

 */

static void dccp_write_xmitlet(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);

		sk_reset_timer(sk, &dccp_sk(sk)->dccps_xmit_timer, jiffies + 1);

	else

		dccp_write_xmit(sk, 0);

	bh_unlock_sock(sk);

	sock_put(sk);

}



static void dccp_init_write_xmit_timer(struct sock *sk)

static void dccp_write_xmit_timer(unsigned long data)

{

	struct dccp_sock *dp = dccp_sk(sk);



	setup_timer(&dp->dccps_xmit_timer, dccp_write_xmit_timer,

			(unsigned long)sk);

	dccp_write_xmitlet(data);

	sock_put((struct sock *)data);

}



void dccp_init_xmit_timers(struct sock *sk)

{

	dccp_init_write_xmit_timer(sk);

	struct dccp_sock *dp = dccp_sk(sk);



	tasklet_init(&dp->dccps_xmitlet, dccp_write_xmitlet, (unsigned long)sk);

	setup_timer(&dp->dccps_xmit_timer, dccp_write_xmit_timer,

							     (unsigned long)sk);

	inet_csk_init_xmit_timers(sk, &dccp_write_timer, &dccp_delack_timer,

				  &dccp_keepalive_timer);

}