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author | Gerrit Renker <gerrit@erg.abdn.ac.uk> | 2008-09-04 05:30:19 (GMT) |
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committer | Gerrit Renker <gerrit@erg.abdn.ac.uk> | 2008-09-04 05:45:38 (GMT) |
commit | f4a66ca4d2ff093c0f9111b449a248ffb8209b4d (patch) | |
tree | 0643f7420a1d0b071f12c719129750d2028bb6e1 /net | |
parent | c8bf462bc567c3dcb083ff95cc13060dd06f138c (diff) | |
download | linux-fsl-qoriq-f4a66ca4d2ff093c0f9111b449a248ffb8209b4d.tar.xz |
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>
Diffstat (limited to 'net')
-rw-r--r-- | net/dccp/ccid.h | 34 | ||||
-rw-r--r-- | net/dccp/ccids/ccid3.c | 12 |
2 files changed, 37 insertions, 9 deletions
diff --git a/net/dccp/ccid.h b/net/dccp/ccid.h index 430a3c2..d27054b 100644 --- a/net/dccp/ccid.h +++ b/net/dccp/ccid.h @@ -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, diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c index 0751a8f..0d406f8 100644 --- a/net/dccp/ccids/ccid3.c +++ b/net/dccp/ccids/ccid3.c @@ -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) |