[DCCP] ccid3: Track RX/TX packet size `s' using moving-average
Problem:
diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index 577fd0e..05513f3 100644
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -159,6 +159,25 @@
ccid3_update_send_time(hctx);
}
+/*
+ * Track the mean packet size `s' (cf. RFC 4342, 5.3 and RFC 3448, 4.1)
+ * @len: DCCP packet payload size in bytes
+ */
+static inline void ccid3_hc_tx_update_s(struct ccid3_hc_tx_sock *hctx, int len)
+{
+ if (unlikely(len == 0))
+ ccid3_pr_debug("Packet payload length is 0 - not updating\n");
+ else
+ hctx->ccid3hctx_s = hctx->ccid3hctx_s == 0 ? len :
+ (9 * hctx->ccid3hctx_s + len) / 10;
+ /*
+ * Note: We could do a potential optimisation here - when `s' changes,
+ * recalculate sending rate and consequently t_ipi, t_delta, and
+ * t_now. This is however non-standard, and the benefits are not
+ * clear, so it is currently left out.
+ */
+}
+
static void ccid3_hc_tx_no_feedback_timer(unsigned long data)
{
struct sock *sk = (struct sock *)data;
@@ -299,6 +318,10 @@
hctx->ccid3hctx_t_last_win_count = now;
ccid3_hc_tx_set_state(sk, TFRC_SSTATE_NO_FBACK);
+ /* Set initial sending rate to 1 packet per second */
+ ccid3_hc_tx_update_s(hctx, len);
+ hctx->ccid3hctx_x = hctx->ccid3hctx_s;
+
/* First timeout, according to [RFC 3448, 4.2], is 1 second */
hctx->ccid3hctx_t_ipi = USEC_PER_SEC;
/* Initial delta: minimum of 0.5 sec and t_gran/2 */
@@ -350,6 +373,8 @@
unsigned long quarter_rtt;
struct dccp_tx_hist_entry *packet;
+ ccid3_hc_tx_update_s(hctx, len);
+
packet = dccp_tx_hist_head(&hctx->ccid3hctx_hist);
if (unlikely(packet == NULL)) {
DCCP_WARN("packet doesn't exist in history!\n");
@@ -594,17 +619,9 @@
static int ccid3_hc_tx_init(struct ccid *ccid, struct sock *sk)
{
- struct dccp_sock *dp = dccp_sk(sk);
struct ccid3_hc_tx_sock *hctx = ccid_priv(ccid);
- if (dp->dccps_packet_size >= TFRC_MIN_PACKET_SIZE &&
- dp->dccps_packet_size <= TFRC_MAX_PACKET_SIZE)
- hctx->ccid3hctx_s = dp->dccps_packet_size;
- else
- hctx->ccid3hctx_s = TFRC_STD_PACKET_SIZE;
-
- /* Set transmission rate to 1 packet per second */
- hctx->ccid3hctx_x = hctx->ccid3hctx_s;
+ hctx->ccid3hctx_s = 0;
hctx->ccid3hctx_state = TFRC_SSTATE_NO_SENT;
INIT_LIST_HEAD(&hctx->ccid3hctx_hist);
@@ -658,6 +675,15 @@
hcrx->ccid3hcrx_state = state;
}
+static inline void ccid3_hc_rx_update_s(struct ccid3_hc_rx_sock *hcrx, int len)
+{
+ if (unlikely(len == 0)) /* don't update on empty packets (e.g. ACKs) */
+ ccid3_pr_debug("Packet payload length is 0 - not updating\n");
+ else
+ hcrx->ccid3hcrx_s = hcrx->ccid3hcrx_s == 0 ? len :
+ (9 * hcrx->ccid3hcrx_s + len) / 10;
+}
+
static void ccid3_hc_rx_send_feedback(struct sock *sk)
{
struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
@@ -934,7 +960,7 @@
struct dccp_rx_hist_entry *packet;
struct timeval now;
u32 p_prev, rtt_prev, r_sample, t_elapsed;
- int loss;
+ int loss, payload_size;
BUG_ON(hcrx == NULL);
@@ -989,6 +1015,9 @@
if (DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_ACK)
return;
+ payload_size = skb->len - dccp_hdr(skb)->dccph_doff * 4;
+ ccid3_hc_rx_update_s(hcrx, payload_size);
+
switch (hcrx->ccid3hcrx_state) {
case TFRC_RSTATE_NO_DATA:
ccid3_pr_debug("%s, sk=%p(%s), skb=%p, sending initial "
@@ -999,8 +1028,7 @@
ccid3_hc_rx_set_state(sk, TFRC_RSTATE_DATA);
return;
case TFRC_RSTATE_DATA:
- hcrx->ccid3hcrx_bytes_recv += skb->len -
- dccp_hdr(skb)->dccph_doff * 4;
+ hcrx->ccid3hcrx_bytes_recv += payload_size;
if (loss)
break;
@@ -1040,22 +1068,16 @@
static int ccid3_hc_rx_init(struct ccid *ccid, struct sock *sk)
{
- struct dccp_sock *dp = dccp_sk(sk);
struct ccid3_hc_rx_sock *hcrx = ccid_priv(ccid);
ccid3_pr_debug("%s, sk=%p\n", dccp_role(sk), sk);
- if (dp->dccps_packet_size >= TFRC_MIN_PACKET_SIZE &&
- dp->dccps_packet_size <= TFRC_MAX_PACKET_SIZE)
- hcrx->ccid3hcrx_s = dp->dccps_packet_size;
- else
- hcrx->ccid3hcrx_s = TFRC_STD_PACKET_SIZE;
-
hcrx->ccid3hcrx_state = TFRC_RSTATE_NO_DATA;
INIT_LIST_HEAD(&hcrx->ccid3hcrx_hist);
INIT_LIST_HEAD(&hcrx->ccid3hcrx_li_hist);
dccp_timestamp(sk, &hcrx->ccid3hcrx_tstamp_last_ack);
hcrx->ccid3hcrx_tstamp_last_feedback = hcrx->ccid3hcrx_tstamp_last_ack;
+ hcrx->ccid3hcrx_s = 0;
hcrx->ccid3hcrx_rtt = 5000; /* XXX 5ms for now... */
return 0;
}