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>
diff --git a/net/dccp/ccid.h b/net/dccp/ccid.h
index 117fb09..75c3582 100644
--- a/net/dccp/ccid.h
+++ b/net/dccp/ccid.h
@@ -134,13 +134,41 @@
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,