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authorGerrit Renker <gerrit@erg.abdn.ac.uk>2008-09-04 07:30:19 +0200
committerGerrit Renker <gerrit@erg.abdn.ac.uk>2008-09-04 07:45:42 +0200
commit68c89ee53571a441799c03d5e240c6441bced620 (patch)
treea355d77fd0bf9e57375601286bf4b792456b423e /net/dccp/ccids/lib
parent22338f09bd60434a3f1d6608f0fa55972067985f (diff)
dccp ccid-3: Update the computation of X_recv
This updates the computation of X_recv with regard to Errata 610/611 for RFC 4342 and draft rfc3448bis-06, ensuring that at least an interval of 1 RTT is used to compute X_recv. The change is wrapped into a new function ccid3_hc_rx_x_recv(). Further changes: ---------------- * feedback is not sent when no data packets arrived (bytes_recv == 0), as per rfc3448bis-06, 6.2; * take the timestamp for the feedback /after/ dccp_send_ack() returns, to avoid taking the transmission time into account (in case layer-2 is busy); * clearer handling of failure in ccid3_first_li(). Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Diffstat (limited to 'net/dccp/ccids/lib')
-rw-r--r--net/dccp/ccids/lib/packet_history.c30
-rw-r--r--net/dccp/ccids/lib/packet_history.h13
2 files changed, 42 insertions, 1 deletions
diff --git a/net/dccp/ccids/lib/packet_history.c b/net/dccp/ccids/lib/packet_history.c
index 5c4ded1cf422..547ad098ea6a 100644
--- a/net/dccp/ccids/lib/packet_history.c
+++ b/net/dccp/ccids/lib/packet_history.c
@@ -385,6 +385,36 @@ int tfrc_rx_handle_loss(struct tfrc_rx_hist *h,
}
EXPORT_SYMBOL_GPL(tfrc_rx_handle_loss);
+/* Compute the sending rate X_recv measured between feedback intervals */
+u32 tfrc_rx_hist_x_recv(struct tfrc_rx_hist *h, const u32 last_x_recv)
+{
+ u64 bytes = h->bytes_recvd, last_rtt = h->rtt_estimate;
+ s64 delta = ktime_to_us(net_timedelta(h->bytes_start));
+
+ WARN_ON(delta <= 0);
+ /*
+ * Ensure that the sampling interval for X_recv is at least one RTT,
+ * by extending the sampling interval backwards in time, over the last
+ * R_(m-1) seconds, as per rfc3448bis-06, 6.2.
+ * To reduce noise (e.g. when the RTT changes often), this is only
+ * done when delta is smaller than RTT/2.
+ */
+ if (last_x_recv > 0 && delta < last_rtt/2) {
+ tfrc_pr_debug("delta < RTT ==> %ld us < %u us\n",
+ (long)delta, (unsigned)last_rtt);
+
+ delta = (bytes ? delta : 0) + last_rtt;
+ bytes += div_u64((u64)last_x_recv * last_rtt, USEC_PER_SEC);
+ }
+
+ if (unlikely(bytes == 0)) {
+ DCCP_WARN("X_recv == 0, using old value of %u\n", last_x_recv);
+ return last_x_recv;
+ }
+ return scaled_div32(bytes, delta);
+}
+EXPORT_SYMBOL_GPL(tfrc_rx_hist_x_recv);
+
void tfrc_rx_hist_purge(struct tfrc_rx_hist *h)
{
int i;
diff --git a/net/dccp/ccids/lib/packet_history.h b/net/dccp/ccids/lib/packet_history.h
index ba5832bbc348..6552be63cb0a 100644
--- a/net/dccp/ccids/lib/packet_history.h
+++ b/net/dccp/ccids/lib/packet_history.h
@@ -93,7 +93,8 @@ struct tfrc_rx_hist_entry {
* @rtt_sample_prev: Used during RTT sampling, points to candidate entry
* @rtt_estimate: Receiver RTT estimate
* @packet_size: Packet size in bytes (as per RFC 3448, 3.1)
- * @bytes_recvd: Number of bytes received since last sending feedback
+ * @bytes_recvd: Number of bytes received since @bytes_start
+ * @bytes_start: Start time for counting @bytes_recvd
*/
struct tfrc_rx_hist {
struct tfrc_rx_hist_entry *ring[TFRC_NDUPACK + 1];
@@ -105,6 +106,7 @@ struct tfrc_rx_hist {
/* Receiver sampling of application payload lengths */
u32 packet_size,
bytes_recvd;
+ ktime_t bytes_start;
};
/**
@@ -169,6 +171,15 @@ static inline u32 tfrc_rx_hist_rtt(const struct tfrc_rx_hist *h)
return h->rtt_estimate;
}
+static inline void tfrc_rx_hist_restart_byte_counter(struct tfrc_rx_hist *h)
+{
+ h->bytes_recvd = 0;
+ h->bytes_start = ktime_get_real();
+}
+
+extern u32 tfrc_rx_hist_x_recv(struct tfrc_rx_hist *h, const u32 last_x_recv);
+
+
extern void tfrc_rx_hist_add_packet(struct tfrc_rx_hist *h,
const struct sk_buff *skb, const u64 ndp);