From fe84f4140f0d24deca8591e38926b95cfd097e62 Mon Sep 17 00:00:00 2001 From: Gerrit Renker Date: Wed, 27 Oct 2010 19:16:25 +0000 Subject: 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-3/4 the maximum possible inter-packet gap is fixed at t_mbi = 64 sec. Signed-off-by: Gerrit Renker Signed-off-by: David S. Miller --- net/dccp/ccid.h | 34 +++++++++++++++++++++++++++++++--- net/dccp/ccids/ccid3.c | 12 ++++++------ 2 files changed, 37 insertions(+), 9 deletions(-) (limited to 'net') diff --git a/net/dccp/ccid.h b/net/dccp/ccid.h index 117fb093dcaf..75c3582a7678 100644 --- a/net/dccp/ccid.h +++ b/net/dccp/ccid.h @@ -134,13 +134,41 @@ 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, diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c index 3060a60ed5ab..3d604e1349c0 100644 --- a/net/dccp/ccids/ccid3.c +++ b/net/dccp/ccids/ccid3.c @@ -268,11 +268,11 @@ 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) { @@ -348,7 +348,7 @@ static int ccid3_hc_tx_send_packet(struct sock *sk, struct sk_buff *skb) /* set the nominal send time for the next following packet */ hc->tx_t_nom = ktime_add_us(hc->tx_t_nom, hc->tx_t_ipi); - return 0; + return CCID_PACKET_SEND_AT_ONCE; } static void ccid3_hc_tx_packet_sent(struct sock *sk, unsigned int len) -- cgit v1.2.1