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: Gerrit Renker <gerrit@erg.abdn.ac.uk>
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@ -129,13 +129,41 @@ static inline int ccid_get_current_tx_ccid(struct dccp_sock *dp)
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extern void ccid_hc_rx_delete(struct ccid *ccid, struct sock *sk);
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extern void ccid_hc_tx_delete(struct ccid *ccid, struct sock *sk);
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/*
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* Congestion control of queued data packets via CCID decision.
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*
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* The TX CCID performs its congestion-control by indicating whether and when a
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* queued packet may be sent, using the return code of ccid_hc_tx_send_packet().
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* The following modes are supported via the symbolic constants below:
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* - timer-based pacing (CCID returns a delay value in milliseconds);
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* - autonomous dequeueing (CCID internally schedules dccps_xmitlet).
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*/
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enum ccid_dequeueing_decision {
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CCID_PACKET_SEND_AT_ONCE = 0x00000, /* "green light": no delay */
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CCID_PACKET_DELAY_MAX = 0x0FFFF, /* maximum delay in msecs */
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CCID_PACKET_DELAY = 0x10000, /* CCID msec-delay mode */
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CCID_PACKET_WILL_DEQUEUE_LATER = 0x20000, /* CCID autonomous mode */
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CCID_PACKET_ERR = 0xF0000, /* error condition */
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};
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static inline int ccid_packet_dequeue_eval(const int return_code)
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{
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if (return_code < 0)
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return CCID_PACKET_ERR;
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if (return_code == 0)
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return CCID_PACKET_SEND_AT_ONCE;
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if (return_code <= CCID_PACKET_DELAY_MAX)
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return CCID_PACKET_DELAY;
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return return_code;
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}
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static inline int ccid_hc_tx_send_packet(struct ccid *ccid, struct sock *sk,
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struct sk_buff *skb)
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{
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int rc = 0;
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if (ccid->ccid_ops->ccid_hc_tx_send_packet != NULL)
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rc = ccid->ccid_ops->ccid_hc_tx_send_packet(sk, skb);
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return rc;
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return ccid->ccid_ops->ccid_hc_tx_send_packet(sk, skb);
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return CCID_PACKET_SEND_AT_ONCE;
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}
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static inline void ccid_hc_tx_packet_sent(struct ccid *ccid, struct sock *sk,
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@ -269,11 +269,11 @@ out:
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sock_put(sk);
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}
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/*
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* returns
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* > 0: delay (in msecs) that should pass before actually sending
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* = 0: can send immediately
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* < 0: error condition; do not send packet
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/**
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* ccid3_hc_tx_send_packet - Delay-based dequeueing of TX packets
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* @skb: next packet candidate to send on @sk
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* This function uses the convention of ccid_packet_dequeue_eval() and
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* returns a millisecond-delay value between 0 and t_mbi = 64000 msec.
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*/
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static int ccid3_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb)
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{
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@ -349,7 +349,7 @@ static int ccid3_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb)
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/* set the nominal send time for the next following packet */
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hctx->t_nom = ktime_add_us(hctx->t_nom, hctx->t_ipi);
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return 0;
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return CCID_PACKET_SEND_AT_ONCE;
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}
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static void ccid3_hc_tx_packet_sent(struct sock *sk, unsigned int len)
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