[CCID 3]: New RX History Step 5 - CCID3 packet reception
This patch continues with the integration of the new RX history structure:
It takes care of
1. recomputing p after the first loss occurred (RFC 3448, 6.1);
2. marking history entries as `loss is indicated';
3. sending the initial feedback (RFC 3448, 6.3)
(Note: the state transition is now in ccid3_hc_rx_send_feedback());
4. loss detection wrt NDUPACK (RFC 4342, 6.1).
Due to the amount of required changes, (4) was split into a subsequent patch.
Documentation on http://www.erg.abdn.ac.uk/users/gerrit/dccp/notes/ccid3_packet_reception/
Signed-off-by: Gerrit Renker <gerrit@xxxxxxxxxxxxxx>
---
net/dccp/ccids/ccid3.c | 102 +++++++++++++++++++------------------------------
1 file changed, 41 insertions(+), 61 deletions(-)
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -685,6 +685,7 @@ static void ccid3_hc_rx_send_feedback(st
case TFRC_RSTATE_NO_DATA:
hcrx->ccid3hcrx_x_recv = 0;
hcrx->ccid3hcrx_pinv = ~0U; /* see RFC 4342, 8.5 */
+ ccid3_hc_rx_set_state(sk, TFRC_RSTATE_DATA);
break;
case TFRC_RSTATE_DATA:
delta = ktime_delta(now, hcrx->ccid3hcrx_last_feedback);
@@ -886,13 +887,44 @@ detect_out:
static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
{
struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
- struct dccp_rx_hist_entry *packet;
- struct timeval now;
- u32 p_prev, loss;
u32 sample, ndp = dccp_sk(sk)->dccps_options_received.dccpor_ndp,
payload_size = skb->len - dccp_hdr(skb)->dccph_doff * 4;
u8 is_data_packet = dccp_data_packet(skb), do_feedback = 0;
+ spin_lock(&hcrx->ccid3hcrx_hist.lock);
+
+ if (unlikely(hcrx->ccid3hcrx_state == TFRC_RSTATE_NO_DATA)) {
+ /* Handle initial feedback */
+ if (is_data_packet) {
+ do_feedback = 1;
+ ccid3_hc_rx_update_s(hcrx, payload_size);
+ }
+ goto update_records;
+ }
+
+ if (tfrc_rx_duplicate(&hcrx->ccid3hcrx_hist, skb))
+ goto done_receiving;
+
+ if (is_data_packet) {
+ ccid3_hc_rx_update_s(hcrx, payload_size);
+ hcrx->ccid3hcrx_bytes_recv += payload_size;
+ }
+
+ /*
+ * Handle pending losses and otherwise check for new loss
+ */
+ if (tfrc_rx_loss_pending(&hcrx->ccid3hcrx_hist)) {
+ /*
+ * Loss Handling
+ *
+ * XXX: part of subsequent patch
+ */
+ goto done_receiving;
+ }
+
+ if (tfrc_rx_new_loss_indicated(&hcrx->ccid3hcrx_hist, skb, ndp))
+ goto update_records;
+
/*
* Handle data packets: RTT sampling and monitoring p
*/
@@ -908,70 +940,18 @@ static void ccid3_hc_rx_packet_recv(stru
}
- packet = dccp_rx_hist_entry_new(ccid3_rx_hist, sk, ndp, skb, GFP_ATOMIC);
- if (unlikely(packet == NULL)) {
- DCCP_WARN("%s(%p), Not enough mem to add rx packet "
- "to history, consider it lost!\n", dccp_role(sk), sk);
- return;
- }
-
- loss = ccid3_hc_rx_detect_loss(sk, packet);
-
- ccid3_hc_rx_update_s(hcrx, payload_size);
-
- switch (hcrx->ccid3hcrx_state) {
- case TFRC_RSTATE_NO_DATA:
- ccid3_pr_debug("%s(%p, state=%s), skb=%p, sending initial "
- "feedback\n", dccp_role(sk), sk,
- dccp_state_name(sk->sk_state), skb);
- ccid3_hc_rx_send_feedback(sk, skb);
- ccid3_hc_rx_set_state(sk, TFRC_RSTATE_DATA);
- return;
- case TFRC_RSTATE_DATA:
- hcrx->ccid3hcrx_bytes_recv += payload_size;
- if (loss)
- break;
-
-/* XXX periodic feedback is resolved later on, the problem with the following
- * code is that it introduces a second variable `_tstamp_last_ack'. A
- * solution is presented later on in the patch set, for the moment, we
- * comment this out.
- dccp_timestamp(sk, &now);
- if ((timeval_delta(&now, &hcrx->ccid3hcrx_tstamp_last_ack) -
- (suseconds_t)hcrx->ccid3hcrx_rtt) >= 0) {
- hcrx->ccid3hcrx_tstamp_last_ack = now;
- ccid3_hc_rx_send_feedback(sk);
- }
-*/
- return;
- case TFRC_RSTATE_TERM:
- DCCP_BUG("%s(%p) - Illegal state TERM", dccp_role(sk), sk);
- return;
- }
+ /* check if the periodic once-per-RTT feedback is due; RFC 4342, 10.3 */
+ if (SUB16(dccp_hdr(skb)->dccph_ccval, hcrx->ccid3hcrx_last_counter) > 3)
+ do_feedback = 1;
update_records:
tfrc_rx_hist_update(&hcrx->ccid3hcrx_hist, skb, ndp);
- /* Dealing with packet loss */
- ccid3_pr_debug("%s(%p, state=%s), data loss! Reacting...\n",
- dccp_role(sk), sk, dccp_state_name(sk->sk_state));
-
- p_prev = hcrx->ccid3hcrx_p;
-
- /* Calculate loss event rate */
- if (!list_empty(&hcrx->ccid3hcrx_li_hist)) {
- u32 i_mean = dccp_li_hist_calc_i_mean(&hcrx->ccid3hcrx_li_hist);
-
- /* Scaling up by 1000000 as fixed decimal */
- if (i_mean != 0)
- hcrx->ccid3hcrx_p = 1000000 / i_mean;
- } else
- DCCP_BUG("empty loss history");
+done_receiving:
+ spin_unlock(&hcrx->ccid3hcrx_hist.lock);
- if (hcrx->ccid3hcrx_p > p_prev) {
+ if (do_feedback)
ccid3_hc_rx_send_feedback(sk, skb);
- return;
- }
}
static int ccid3_hc_rx_init(struct ccid *ccid, struct sock *sk)
-
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