[DCCP] loss_interval: Move ccid3_hc_rx_update_li to loss_interval

Renaming it to dccp_li_update_li.

Also based on previous work by Ian McDonald.

Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>

1 files changed, 160 insertions, 0 deletions

diff --git a/net/dccp/ccids/lib/loss_interval.c b/net/dccp/ccids/lib/loss_interval.c
index 3829afc31176..ee59fde6653f 100644
--- a/net/dccp/ccids/lib/loss_interval.c
+++ b/net/dccp/ccids/lib/loss_interval.c
@@ -15,6 +15,8 @@
 #include <net/sock.h>
 #include "../../dccp.h"
 #include "loss_interval.h"
+#include "packet_history.h"
+#include "tfrc.h"
 
 struct dccp_li_hist *dccp_li_hist_new(const char *name)
 {
@@ -141,3 +143,161 @@ int dccp_li_hist_interval_new(struct dccp_li_hist *hist,
 }
 
 EXPORT_SYMBOL_GPL(dccp_li_hist_interval_new);
+
+/* calculate first loss interval
+ *
+ * returns estimated loss interval in usecs */
+static u32 dccp_li_calc_first_li(struct sock *sk,
+                                 struct list_head *hist_list,
+                                 struct timeval *last_feedback,
+                                 u16 s, u32 bytes_recv,
+                                 u32 previous_x_recv)
+{
+        struct dccp_rx_hist_entry *entry, *next, *tail = NULL;
+        u32 x_recv, p;
+        suseconds_t rtt, delta;
+        struct timeval tstamp = { 0, 0 };
+        int interval = 0;
+        int win_count = 0;
+        int step = 0;
+        u64 fval;
+
+        list_for_each_entry_safe(entry, next, hist_list, dccphrx_node) {
+                if (dccp_rx_hist_entry_data_packet(entry)) {
+                        tail = entry;
+
+                        switch (step) {
+                        case 0:
+                                tstamp    = entry->dccphrx_tstamp;
+                                win_count = entry->dccphrx_ccval;
+                                step = 1;
+                                break;
+                        case 1:
+                                interval = win_count - entry->dccphrx_ccval;
+                                if (interval < 0)
+                                        interval += TFRC_WIN_COUNT_LIMIT;
+                                if (interval > 4)
+                                        goto found;
+                                break;
+                        }
+                }
+        }
+
+        if (unlikely(step == 0)) {
+                DCCP_WARN("%s(%p), packet history has no data packets!\n",
+                          dccp_role(sk), sk);
+                return ~0;
+        }
+
+        if (unlikely(interval == 0)) {
+                DCCP_WARN("%s(%p), Could not find a win_count interval > 0."
+                          "Defaulting to 1\n", dccp_role(sk), sk);
+                interval = 1;
+        }
+found:
+        if (!tail) {
+                DCCP_CRIT("tail is null\n");
+                return ~0;
+        }
+
+        delta = timeval_delta(&tstamp, &tail->dccphrx_tstamp);
+        DCCP_BUG_ON(delta < 0);
+
+        rtt = delta * 4 / interval;
+        dccp_pr_debug("%s(%p), approximated RTT to %dus\n",
+                      dccp_role(sk), sk, (int)rtt);
+
+        /*
+         * Determine the length of the first loss interval via inverse lookup.
+         * Assume that X_recv can be computed by the throughput equation
+         *                  s
+         *      X_recv = --------
+         *               R * fval
+         * Find some p such that f(p) = fval; return 1/p [RFC 3448, 6.3.1].
+         */
+        if (rtt == 0) {                 /* would result in divide-by-zero */
+                DCCP_WARN("RTT==0\n");
+                return ~0;
+        }
+
+        dccp_timestamp(sk, &tstamp);
+        delta = timeval_delta(&tstamp, last_feedback);
+        DCCP_BUG_ON(delta <= 0);
+
+        x_recv = scaled_div32(bytes_recv, delta);
+        if (x_recv == 0) {              /* would also trigger divide-by-zero */
+                DCCP_WARN("X_recv==0\n");
+                if (previous_x_recv == 0) {
+                        DCCP_BUG("stored value of X_recv is zero");
+                        return ~0;
+                }
+                x_recv = previous_x_recv;
+        }
+
+        fval = scaled_div(s, rtt);
+        fval = scaled_div32(fval, x_recv);
+        p = tfrc_calc_x_reverse_lookup(fval);
+
+        dccp_pr_debug("%s(%p), receive rate=%u bytes/s, implied "
+                      "loss rate=%u\n", dccp_role(sk), sk, x_recv, p);
+
+        if (p == 0)
+                return ~0;
+        else
+                return 1000000 / p;
+}
+
+void dccp_li_update_li(struct sock *sk, struct dccp_li_hist *li_hist,
+                       struct list_head *li_hist_list,
+                       struct list_head *hist_list,
+                       struct timeval *last_feedback, u16 s, u32 bytes_recv,
+                       u32 previous_x_recv, u64 seq_loss, u8 win_loss)
+{
+        struct dccp_li_hist_entry *head;
+        u64 seq_temp;
+
+        if (list_empty(li_hist_list)) {
+                if (!dccp_li_hist_interval_new(li_hist, li_hist_list,
+                                               seq_loss, win_loss))
+                        return;
+
+                head = list_entry(li_hist_list->next, struct dccp_li_hist_entry,
+                                  dccplih_node);
+                head->dccplih_interval = dccp_li_calc_first_li(sk, hist_list,
+                                                               last_feedback,
+                                                               s, bytes_recv,
+                                                               previous_x_recv);
+        } else {
+                struct dccp_li_hist_entry *entry;
+                struct list_head *tail;
+
+                head = list_entry(li_hist_list->next, struct dccp_li_hist_entry,
+                                  dccplih_node);
+                /* 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(li_hist, GFP_ATOMIC);
+
+                if (entry == NULL) {
+                        DCCP_BUG("out of memory - can not allocate entry");
+                        return;
+                }
+
+                list_add(&entry->dccplih_node, li_hist_list);
+
+                tail = li_hist_list->prev;
+                list_del(tail);
+                kmem_cache_free(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;
+        }
+}
+
+EXPORT_SYMBOL_GPL(dccp_li_update_li);