Commit f4a66ca4 authored by Gerrit Renker's avatar Gerrit Renker
Browse files

dccp: Return-value convention of hc_tx_send_packet() 



This patch reorganises the return value convention of the CCID TX sending
function, to permit more flexible schemes, as required by subsequent patches.

Currently the convention is 
 * values < 0     mean error,
 * a value == 0   means "send now", and
 * a value x > 0  means "send in x milliseconds".

The patch provides symbolic constants and a function to interpret return values.
In addition, it caps the maximum positive return value to 0xFFFF milliseconds,
corresponding to 65.535 seconds. 

This is possible since in CCID-3 the maximum inter-packet gap is t_mbi = 64 sec.

Signed-off-by: default avatarGerrit Renker <gerrit@erg.abdn.ac.uk>
parent c8bf462b

net/dccp/ccid.h

+31 −3
Original line number Diff line number Diff line
@@ -129,13 +129,41 @@ static inline int ccid_get_current_tx_ccid(struct dccp_sock *dp) 
extern void ccid_hc_rx_delete(struct ccid *ccid, struct sock *sk);

extern void ccid_hc_tx_delete(struct ccid *ccid, struct sock *sk);



/*

 * Congestion control of queued data packets via CCID decision.

 *

 * The TX CCID performs its congestion-control by indicating whether and when a

 * queued packet may be sent, using the return code of ccid_hc_tx_send_packet().

 * The following modes are supported via the symbolic constants below:

 * - timer-based pacing    (CCID returns a delay value in milliseconds);

 * - autonomous dequeueing (CCID internally schedules dccps_xmitlet).

 */



enum ccid_dequeueing_decision {

	CCID_PACKET_SEND_AT_ONCE =	 0x00000,  /* "green light": no delay */

	CCID_PACKET_DELAY_MAX =		 0x0FFFF,  /* maximum delay in msecs  */

	CCID_PACKET_DELAY =		 0x10000,  /* CCID msec-delay mode */

	CCID_PACKET_WILL_DEQUEUE_LATER = 0x20000,  /* CCID autonomous mode */

	CCID_PACKET_ERR =		 0xF0000,  /* error condition */

};



static inline int ccid_packet_dequeue_eval(const int return_code)

{

	if (return_code < 0)

		return CCID_PACKET_ERR;

	if (return_code == 0)

		return CCID_PACKET_SEND_AT_ONCE;

	if (return_code <= CCID_PACKET_DELAY_MAX)

		return CCID_PACKET_DELAY;

	return return_code;

}



static inline int ccid_hc_tx_send_packet(struct ccid *ccid, struct sock *sk,

					 struct sk_buff *skb)

{

	int rc = 0;

	if (ccid->ccid_ops->ccid_hc_tx_send_packet != NULL)

		rc = ccid->ccid_ops->ccid_hc_tx_send_packet(sk, skb);

	return rc;

		return ccid->ccid_ops->ccid_hc_tx_send_packet(sk, skb);

	return CCID_PACKET_SEND_AT_ONCE;

}



static inline void ccid_hc_tx_packet_sent(struct ccid *ccid, struct sock *sk,

net/dccp/ccids/ccid3.c

+6 −6
Original line number Diff line number Diff line
@@ -269,11 +269,11 @@ out: 
	sock_put(sk);

}



/*

 * returns

 *   > 0: delay (in msecs) that should pass before actually sending

 *   = 0: can send immediately

 *   < 0: error condition; do not send packet

/**

 * ccid3_hc_tx_send_packet  -  Delay-based dequeueing of TX packets

 * @skb: next packet candidate to send on @sk

 * This function uses the convention of ccid_packet_dequeue_eval() and

 * returns a millisecond-delay value between 0 and t_mbi = 64000 msec.

 */

static int ccid3_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb)

{
@@ -349,7 +349,7 @@ static int ccid3_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb) 


	/* set the nominal send time for the next following packet */

	hctx->t_nom = ktime_add_us(hctx->t_nom, hctx->t_ipi);

	return 0;

	return CCID_PACKET_SEND_AT_ONCE;

}



static void ccid3_hc_tx_packet_sent(struct sock *sk, unsigned int len)

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