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authorGerrit Renker <gerrit@erg.abdn.ac.uk>2010-10-27 19:16:25 +0000
committerDavid S. Miller <davem@davemloft.net>2010-10-28 10:27:00 -0700
commitfe84f4140f0d24deca8591e38926b95cfd097e62 (patch)
tree5b4c809f131105fddb533776632ff1d546b604a7 /net
parentde7fe7874dc55e8226245c50f07dec3c7b285044 (diff)
downloadlinux-2.6.38-lt-ux500-fe84f4140f0d24deca8591e38926b95cfd097e62.tar.gz
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 <gerrit@erg.abdn.ac.uk> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/dccp/ccid.h34
-rw-r--r--net/dccp/ccids/ccid3.c12
2 files changed, 37 insertions, 9 deletions
diff --git a/net/dccp/ccid.h b/net/dccp/ccid.h
index 117fb093dca..75c3582a767 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 3060a60ed5a..3d604e1349c 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)