Em Wed, Dec 05, 2007 at 02:53:09PM +0000, Gerrit Renker escreveu:
> | Thanks, I folded this into the reorganized RX history handling patch,
> | together with reverting ccid3_hc_rx_packet_recv to very close to your
> | original patch, with this changes:
> |
> | 1. no need to calculate the payload size for non data packets as this
> | value won't be used.
> | 2. Initialize hcrx->ccid3hcrx_bytes_recv with the payload size when
> | hcrx->ccid3hcrx_state == TFRC_RSTATE_NO_DATA.
> | 3. tfrc_rx_hist_duplicate() is only called when ccid3hcrx_state !=
> | TFRC_RSTATE_NO_DATA, so it doesn't need to goto the done_receiving
> | label (that was removed as this was its only use) as do_feedback
> | would always be CCID3_FBACK_NONE and so the test would always fail
> | and no feedback would be sent, so just return right there.
> |
> | Now it reads:
> |
> | 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);
> | enum ccid3_fback_type do_feedback = CCID3_FBACK_NONE;
> | const u32 ndp = dccp_sk(sk)->dccps_options_received.dccpor_ndp;
> | const bool is_data_packet = dccp_data_packet(skb);
> |
> | if (unlikely(hcrx->ccid3hcrx_state == TFRC_RSTATE_NO_DATA)) {
> | if (is_data_packet) {
> | const u32 payload = skb->len - dccp_hdr(skb)->dccph_doff * 4;
> | do_feedback = FBACK_INITIAL;
> | ccid3_hc_rx_set_state(sk, TFRC_RSTATE_DATA);
> | hcrx->ccid3hcrx_s =
> | hcrx->ccid3hcrx_bytes_recv = payload_size;
>
> ==> Please see other email regarding bytes_recv, but I think you already got that.
> Maybe one could then write
> hcrx->ccid3hcrx_s = skb->len - dccp_hdr(skb)->dccph_doff * 4;
OK, I got that.
> | }
> | goto update_records;
> | }
> |
> | if (tfrc_rx_hist_duplicate(&hcrx->ccid3hcrx_hist, skb))
> | return; /* done receiving */
> |
> | if (is_data_packet) {
> | const u32 payload = skb->len - dccp_hdr(skb)->dccph_doff * 4;
> | /*
> | * Update moving-average of s and the sum of received payload bytes
> | */
> | hcrx->ccid3hcrx_s = tfrc_ewma(hcrx->ccid3hcrx_s, payload_size, 9);
> | hcrx->ccid3hcrx_bytes_recv += payload_size;
> | }
> |
> | /*
> | * Handle pending losses and otherwise check for new loss
> | */
> | if (tfrc_rx_hist_new_loss_indicated(&hcrx->ccid3hcrx_hist, skb, ndp))
> | goto update_records;
> |
> | /*
> | * Handle data packets: RTT sampling and monitoring p
> | */
> | if (unlikely(!is_data_packet))
> | goto update_records;
> |
> | if (list_empty(&hcrx->ccid3hcrx_li_hist)) { /* no loss so far: p = 0 */
> | const u32 sample = tfrc_rx_hist_sample_rtt(&hcrx->ccid3hcrx_hist, skb);
> ==> If you like, you could add the original comment here that p=0 if no loss occured, i.e.
> /*
> * Empty loss history: no loss so far, hence p stays 0.
> * Sample RTT values, since an RTT estimate is required for the
> * computation of p when the first loss occurs; RFC 3448, 6.3.1.
> */
done
> | if (sample != 0)
> | hcrx->ccid3hcrx_rtt = tfrc_ewma(hcrx->ccid3hcrx_rtt, sample, 9);
> | }
> |
> | /*
> | * 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 = CCID3_FBACK_PERIODIC;
> |
> | update_records:
> | tfrc_rx_hist_add_packet(&hcrx->ccid3hcrx_hist, skb, ndp);
> |
> ==> here a jump label is missing. It is not needed by this patch and
> above you have replaced it with a return + comment, but it is needed in a later
> patch: when a new loss event occurs, the control jumps to `done_receiving' and
> sends a feedback packet with type FBACK_PARAM_CHANGE.
OK, I was wondering that the user for FBACK_PARAM_CHANGE in
ccid3_hc_rx_send_feedback was in another patch.
> done_receiving:
Ok, we can add the jump label when we make use of it
> | if (do_feedback)
> | ccid3_hc_rx_send_feedback(sk, skb, do_feedback);
> | }
> |
>
> | Now to some questions and please bear with me as I haven't got to the
> | patches after this:
> |
> | tfrc_rx_hist->loss_count as of now is a boolean, my understanding is
> | that you are counting loss events, i.e. it doesn't matter in:
> |
> It is not a boolean, but uses a hidden trick which maybe should be commented:
> * here and in the TCP world NDUPACK = 3
> * hence the bitfield size for loss_count is 2 bits, which can express
> at most 3 = NDUPACK (that is why it is declared as loss_count:2)
> * the trick is that when the loss count increases beyond 3, it automatically
> cycles back to 0 (although the code does not rely on that features
> and does this explicitly);
> * loss_start is the same
OK, will read the next patches with this in mind, thanks for the
explanations.
- Arnaldo
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