[DCCP]: Fix CCID3

This fixes CCID3 to give much closer performance to RFC4342.

CCID3 is meant to alter sending rate based on RTT and loss.

The performance was verified against:
http://wand.net.nz/~perry/max_download.php

For example I tested with netem and had the following parameters:
Delayed Acks 1, MSS 256 bytes, RTT 105 ms, packet loss 5%.

This gives a theoretical speed of 71.9 Kbits/s. I measured across three
runs with this patch set and got 70.1 Kbits/s. Without this patchset the
average was 232 Kbits/s which means Linux can't be used for CCID3 research
properly.

I also tested with netem turned off so box just acting as router with 1.2
msec RTT. The performance with this is the same with or without the patch
at around 30 Mbit/s.

Signed off by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 119 insertions, 30 deletions

diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index 0f85970ee6d1..090bc39e8199 100644
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -342,6 +342,8 @@ static int ccid3_hc_tx_send_packet(struct sock *sk,
                 new_packet->dccphtx_ccval =
                         DCCP_SKB_CB(skb)->dccpd_ccval =
                                 hctx->ccid3hctx_last_win_count;
+                timeval_add_usecs(&hctx->ccid3hctx_t_nom,
+                                  hctx->ccid3hctx_t_ipi);
         }
 out:
         return rc;
@@ -413,7 +415,8 @@ static void ccid3_hc_tx_packet_sent(struct sock *sk, int more, int len)
         case TFRC_SSTATE_NO_FBACK:
         case TFRC_SSTATE_FBACK:
                 if (len > 0) {
-                        hctx->ccid3hctx_t_nom = now;
+                        timeval_sub_usecs(&hctx->ccid3hctx_t_nom,
+                                  hctx->ccid3hctx_t_ipi);
                         ccid3_calc_new_t_ipi(hctx);
                         ccid3_calc_new_delta(hctx);
                         timeval_add_usecs(&hctx->ccid3hctx_t_nom,
@@ -757,8 +760,7 @@ static void ccid3_hc_rx_send_feedback(struct sock *sk)
         }
 
         hcrx->ccid3hcrx_tstamp_last_feedback = now;
-        hcrx->ccid3hcrx_last_counter         = packet->dccphrx_ccval;
-        hcrx->ccid3hcrx_seqno_last_counter   = packet->dccphrx_seqno;
+        hcrx->ccid3hcrx_ccval_last_counter   = packet->dccphrx_ccval;
         hcrx->ccid3hcrx_bytes_recv           = 0;
 
         /* Convert to multiples of 10us */
@@ -782,7 +784,7 @@ static int ccid3_hc_rx_insert_options(struct sock *sk, struct sk_buff *skb)
         if (!(sk->sk_state == DCCP_OPEN || sk->sk_state == DCCP_PARTOPEN))
                 return 0;
 
-        DCCP_SKB_CB(skb)->dccpd_ccval = hcrx->ccid3hcrx_last_counter;
+        DCCP_SKB_CB(skb)->dccpd_ccval = hcrx->ccid3hcrx_ccval_last_counter;
 
         if (dccp_packet_without_ack(skb))
                 return 0;
@@ -854,6 +856,11 @@ static u32 ccid3_hc_rx_calc_first_li(struct sock *sk)
                 interval = 1;
         }
 found:
+        if (!tail) {
+                LIMIT_NETDEBUG(KERN_WARNING "%s: tail is null\n",
+                   __FUNCTION__);
+                return ~0;
+        }
         rtt = timeval_delta(&tstamp, &tail->dccphrx_tstamp) * 4 / interval;
         ccid3_pr_debug("%s, sk=%p, approximated RTT to %uus\n",
                        dccp_role(sk), sk, rtt);
@@ -864,9 +871,20 @@ found:
         delta = timeval_delta(&tstamp, &hcrx->ccid3hcrx_tstamp_last_feedback);
         x_recv = usecs_div(hcrx->ccid3hcrx_bytes_recv, delta);
 
+        if (x_recv == 0)
+                x_recv = hcrx->ccid3hcrx_x_recv;
+
         tmp1 = (u64)x_recv * (u64)rtt;
         do_div(tmp1,10000000);
         tmp2 = (u32)tmp1;
+
+        if (!tmp2) {
+                LIMIT_NETDEBUG(KERN_WARNING "tmp2 = 0 "
+                   "%s: x_recv = %u, rtt =%u\n",
+                   __FUNCTION__, x_recv, rtt);
+                return ~0;
+        }
+
         fval = (hcrx->ccid3hcrx_s * 100000) / tmp2;
         /* do not alter order above or you will get overflow on 32 bit */
         p = tfrc_calc_x_reverse_lookup(fval);
@@ -882,31 +900,101 @@ found:
 static void ccid3_hc_rx_update_li(struct sock *sk, u64 seq_loss, u8 win_loss)
 {
         struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
+        struct dccp_li_hist_entry *next, *head;
+        u64 seq_temp;
 
-        if (seq_loss != DCCP_MAX_SEQNO + 1 &&
-            list_empty(&hcrx->ccid3hcrx_li_hist)) {
-                struct dccp_li_hist_entry *li_tail;
+        if (list_empty(&hcrx->ccid3hcrx_li_hist)) {
+                if (!dccp_li_hist_interval_new(ccid3_li_hist,
+                   &hcrx->ccid3hcrx_li_hist, seq_loss, win_loss))
+                        return;
 
-                li_tail = dccp_li_hist_interval_new(ccid3_li_hist,
-                                                    &hcrx->ccid3hcrx_li_hist,
-                                                    seq_loss, win_loss);
-                if (li_tail == NULL)
+                next = (struct dccp_li_hist_entry *)
+                   hcrx->ccid3hcrx_li_hist.next;
+                next->dccplih_interval = ccid3_hc_rx_calc_first_li(sk);
+        } else {
+                struct dccp_li_hist_entry *entry;
+                struct list_head *tail;
+
+                head = (struct dccp_li_hist_entry *)
+                   hcrx->ccid3hcrx_li_hist.next;
+                /* FIXME win count check removed as was wrong */
+                /* should make this check with receive history */
+                /* and compare there as per section 10.2 of RFC4342 */
+
+                /* new loss event detected */
+                /* calculate last interval length */
+                seq_temp = dccp_delta_seqno(head->dccplih_seqno, seq_loss);
+                entry = dccp_li_hist_entry_new(ccid3_li_hist, SLAB_ATOMIC);
+
+                if (entry == NULL) {
+                        printk(KERN_CRIT "%s: out of memory\n",__FUNCTION__);
+                        dump_stack();
                         return;
-                li_tail->dccplih_interval = ccid3_hc_rx_calc_first_li(sk);
-        } else
-                    LIMIT_NETDEBUG(KERN_WARNING "%s: FIXME: find end of "
-                                   "interval\n", __FUNCTION__);
+                }
+
+                list_add(&entry->dccplih_node, &hcrx->ccid3hcrx_li_hist);
+
+                tail = hcrx->ccid3hcrx_li_hist.prev;
+                list_del(tail);
+                kmem_cache_free(ccid3_li_hist->dccplih_slab, tail);
+
+                /* Create the newest interval */
+                entry->dccplih_seqno = seq_loss;
+                entry->dccplih_interval = seq_temp;
+                entry->dccplih_win_count = win_loss;
+        }
 }
 
-static void ccid3_hc_rx_detect_loss(struct sock *sk)
+static int ccid3_hc_rx_detect_loss(struct sock *sk,
+                                    struct dccp_rx_hist_entry *packet)
 {
         struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
-        u8 win_loss;
-        const u64 seq_loss = dccp_rx_hist_detect_loss(&hcrx->ccid3hcrx_hist,
-                                                      &hcrx->ccid3hcrx_li_hist,
-                                                      &win_loss);
+        struct dccp_rx_hist_entry *rx_hist = dccp_rx_hist_head(&hcrx->ccid3hcrx_hist);
+        u64 seqno = packet->dccphrx_seqno;
+        u64 tmp_seqno;
+        int loss = 0;
+        u8 ccval;
+
+
+        tmp_seqno = hcrx->ccid3hcrx_seqno_nonloss;
+
+        if (!rx_hist ||
+           follows48(packet->dccphrx_seqno, hcrx->ccid3hcrx_seqno_nonloss)) {
+                hcrx->ccid3hcrx_seqno_nonloss = seqno;
+                hcrx->ccid3hcrx_ccval_nonloss = packet->dccphrx_ccval;
+                goto detect_out;
+        }
+
 
-        ccid3_hc_rx_update_li(sk, seq_loss, win_loss);
+        while (dccp_delta_seqno(hcrx->ccid3hcrx_seqno_nonloss, seqno)
+           > TFRC_RECV_NUM_LATE_LOSS) {
+                loss = 1;
+                ccid3_hc_rx_update_li(sk, hcrx->ccid3hcrx_seqno_nonloss,
+                   hcrx->ccid3hcrx_ccval_nonloss);
+                tmp_seqno = hcrx->ccid3hcrx_seqno_nonloss;
+                dccp_inc_seqno(&tmp_seqno);
+                hcrx->ccid3hcrx_seqno_nonloss = tmp_seqno;
+                dccp_inc_seqno(&tmp_seqno);
+                while (dccp_rx_hist_find_entry(&hcrx->ccid3hcrx_hist,
+                   tmp_seqno, &ccval)) {
+                        hcrx->ccid3hcrx_seqno_nonloss = tmp_seqno;
+                        hcrx->ccid3hcrx_ccval_nonloss = ccval;
+                        dccp_inc_seqno(&tmp_seqno);
+                }
+        }
+
+        /* FIXME - this code could be simplified with above while */
+        /* but works at moment */
+        if (follows48(packet->dccphrx_seqno, hcrx->ccid3hcrx_seqno_nonloss)) {
+                hcrx->ccid3hcrx_seqno_nonloss = seqno;
+                hcrx->ccid3hcrx_ccval_nonloss = packet->dccphrx_ccval;
+        }
+
+detect_out:
+        dccp_rx_hist_add_packet(ccid3_rx_hist, &hcrx->ccid3hcrx_hist,
+                   &hcrx->ccid3hcrx_li_hist, packet,
+                   hcrx->ccid3hcrx_seqno_nonloss);
+        return loss;
 }
 
 static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
@@ -916,8 +1004,8 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
         struct dccp_rx_hist_entry *packet;
         struct timeval now;
         u8 win_count;
-        u32 p_prev, r_sample, t_elapsed;
-        int ins;
+        u32 p_prev, rtt_prev, r_sample, t_elapsed;
+        int loss;
 
         BUG_ON(hcrx == NULL ||
                !(hcrx->ccid3hcrx_state == TFRC_RSTATE_NO_DATA ||
@@ -932,7 +1020,7 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
         case DCCP_PKT_DATAACK:
                 if (opt_recv->dccpor_timestamp_echo == 0)
                         break;
-                p_prev = hcrx->ccid3hcrx_rtt;
+                rtt_prev = hcrx->ccid3hcrx_rtt;
                 dccp_timestamp(sk, &now);
                 timeval_sub_usecs(&now, opt_recv->dccpor_timestamp_echo * 10);
                 r_sample = timeval_usecs(&now);
@@ -951,8 +1039,8 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
                         hcrx->ccid3hcrx_rtt = (hcrx->ccid3hcrx_rtt * 9) / 10 +
                                               r_sample / 10;
 
-                if (p_prev != hcrx->ccid3hcrx_rtt)
-                        ccid3_pr_debug("%s, New RTT=%luus, elapsed time=%u\n",
+                if (rtt_prev != hcrx->ccid3hcrx_rtt)
+                        ccid3_pr_debug("%s, New RTT=%uus, elapsed time=%u\n",
                                        dccp_role(sk), hcrx->ccid3hcrx_rtt,
                                        opt_recv->dccpor_elapsed_time);
                 break;
@@ -973,8 +1061,7 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
 
         win_count = packet->dccphrx_ccval;
 
-        ins = dccp_rx_hist_add_packet(ccid3_rx_hist, &hcrx->ccid3hcrx_hist,
-                                      &hcrx->ccid3hcrx_li_hist, packet);
+        loss = ccid3_hc_rx_detect_loss(sk, packet);
 
         if (DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_ACK)
                 return;
@@ -991,7 +1078,7 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
         case TFRC_RSTATE_DATA:
                 hcrx->ccid3hcrx_bytes_recv += skb->len -
                                               dccp_hdr(skb)->dccph_doff * 4;
-                if (ins != 0)
+                if (loss)
                         break;
 
                 dccp_timestamp(sk, &now);
@@ -1012,7 +1099,6 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
         ccid3_pr_debug("%s, sk=%p(%s), data loss! Reacting...\n",
                        dccp_role(sk), sk, dccp_state_name(sk->sk_state));
 
-        ccid3_hc_rx_detect_loss(sk);
         p_prev = hcrx->ccid3hcrx_p;
         
         /* Calculate loss event rate */
@@ -1022,6 +1108,9 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
                 /* Scaling up by 1000000 as fixed decimal */
                 if (i_mean != 0)
                         hcrx->ccid3hcrx_p = 1000000 / i_mean;
+        } else {
+                printk(KERN_CRIT "%s: empty loss hist\n",__FUNCTION__);
+                dump_stack();
         }
 
         if (hcrx->ccid3hcrx_p > p_prev) {