Add the rt linux 4.1.3-rt3 as base
[kvmfornfv.git] / kernel / net / dccp / ccids / lib / loss_interval.c
diff --git a/kernel/net/dccp/ccids/lib/loss_interval.c b/kernel/net/dccp/ccids/lib/loss_interval.c
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+/*
+ *  Copyright (c) 2007   The University of Aberdeen, Scotland, UK
+ *  Copyright (c) 2005-7 The University of Waikato, Hamilton, New Zealand.
+ *  Copyright (c) 2005-7 Ian McDonald <ian.mcdonald@jandi.co.nz>
+ *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ */
+#include <net/sock.h>
+#include "tfrc.h"
+
+static struct kmem_cache  *tfrc_lh_slab  __read_mostly;
+/* Loss Interval weights from [RFC 3448, 5.4], scaled by 10 */
+static const int tfrc_lh_weights[NINTERVAL] = { 10, 10, 10, 10, 8, 6, 4, 2 };
+
+/* implements LIFO semantics on the array */
+static inline u8 LIH_INDEX(const u8 ctr)
+{
+       return LIH_SIZE - 1 - (ctr % LIH_SIZE);
+}
+
+/* the `counter' index always points at the next entry to be populated */
+static inline struct tfrc_loss_interval *tfrc_lh_peek(struct tfrc_loss_hist *lh)
+{
+       return lh->counter ? lh->ring[LIH_INDEX(lh->counter - 1)] : NULL;
+}
+
+/* given i with 0 <= i <= k, return I_i as per the rfc3448bis notation */
+static inline u32 tfrc_lh_get_interval(struct tfrc_loss_hist *lh, const u8 i)
+{
+       BUG_ON(i >= lh->counter);
+       return lh->ring[LIH_INDEX(lh->counter - i - 1)]->li_length;
+}
+
+/*
+ *     On-demand allocation and de-allocation of entries
+ */
+static struct tfrc_loss_interval *tfrc_lh_demand_next(struct tfrc_loss_hist *lh)
+{
+       if (lh->ring[LIH_INDEX(lh->counter)] == NULL)
+               lh->ring[LIH_INDEX(lh->counter)] = kmem_cache_alloc(tfrc_lh_slab,
+                                                                   GFP_ATOMIC);
+       return lh->ring[LIH_INDEX(lh->counter)];
+}
+
+void tfrc_lh_cleanup(struct tfrc_loss_hist *lh)
+{
+       if (!tfrc_lh_is_initialised(lh))
+               return;
+
+       for (lh->counter = 0; lh->counter < LIH_SIZE; lh->counter++)
+               if (lh->ring[LIH_INDEX(lh->counter)] != NULL) {
+                       kmem_cache_free(tfrc_lh_slab,
+                                       lh->ring[LIH_INDEX(lh->counter)]);
+                       lh->ring[LIH_INDEX(lh->counter)] = NULL;
+               }
+}
+
+static void tfrc_lh_calc_i_mean(struct tfrc_loss_hist *lh)
+{
+       u32 i_i, i_tot0 = 0, i_tot1 = 0, w_tot = 0;
+       int i, k = tfrc_lh_length(lh) - 1; /* k is as in rfc3448bis, 5.4 */
+
+       if (k <= 0)
+               return;
+
+       for (i = 0; i <= k; i++) {
+               i_i = tfrc_lh_get_interval(lh, i);
+
+               if (i < k) {
+                       i_tot0 += i_i * tfrc_lh_weights[i];
+                       w_tot  += tfrc_lh_weights[i];
+               }
+               if (i > 0)
+                       i_tot1 += i_i * tfrc_lh_weights[i-1];
+       }
+
+       lh->i_mean = max(i_tot0, i_tot1) / w_tot;
+}
+
+/**
+ * tfrc_lh_update_i_mean  -  Update the `open' loss interval I_0
+ * For recomputing p: returns `true' if p > p_prev  <=>  1/p < 1/p_prev
+ */
+u8 tfrc_lh_update_i_mean(struct tfrc_loss_hist *lh, struct sk_buff *skb)
+{
+       struct tfrc_loss_interval *cur = tfrc_lh_peek(lh);
+       u32 old_i_mean = lh->i_mean;
+       s64 len;
+
+       if (cur == NULL)                        /* not initialised */
+               return 0;
+
+       len = dccp_delta_seqno(cur->li_seqno, DCCP_SKB_CB(skb)->dccpd_seq) + 1;
+
+       if (len - (s64)cur->li_length <= 0)     /* duplicate or reordered */
+               return 0;
+
+       if (SUB16(dccp_hdr(skb)->dccph_ccval, cur->li_ccval) > 4)
+               /*
+                * Implements RFC 4342, 10.2:
+                * If a packet S (skb) exists whose seqno comes `after' the one
+                * starting the current loss interval (cur) and if the modulo-16
+                * distance from C(cur) to C(S) is greater than 4, consider all
+                * subsequent packets as belonging to a new loss interval. This
+                * test is necessary since CCVal may wrap between intervals.
+                */
+               cur->li_is_closed = 1;
+
+       if (tfrc_lh_length(lh) == 1)            /* due to RFC 3448, 6.3.1 */
+               return 0;
+
+       cur->li_length = len;
+       tfrc_lh_calc_i_mean(lh);
+
+       return lh->i_mean < old_i_mean;
+}
+
+/* Determine if `new_loss' does begin a new loss interval [RFC 4342, 10.2] */
+static inline u8 tfrc_lh_is_new_loss(struct tfrc_loss_interval *cur,
+                                    struct tfrc_rx_hist_entry *new_loss)
+{
+       return  dccp_delta_seqno(cur->li_seqno, new_loss->tfrchrx_seqno) > 0 &&
+               (cur->li_is_closed || SUB16(new_loss->tfrchrx_ccval, cur->li_ccval) > 4);
+}
+
+/**
+ * tfrc_lh_interval_add  -  Insert new record into the Loss Interval database
+ * @lh:                   Loss Interval database
+ * @rh:                   Receive history containing a fresh loss event
+ * @calc_first_li: Caller-dependent routine to compute length of first interval
+ * @sk:                   Used by @calc_first_li in caller-specific way (subtyping)
+ *
+ * Updates I_mean and returns 1 if a new interval has in fact been added to @lh.
+ */
+int tfrc_lh_interval_add(struct tfrc_loss_hist *lh, struct tfrc_rx_hist *rh,
+                        u32 (*calc_first_li)(struct sock *), struct sock *sk)
+{
+       struct tfrc_loss_interval *cur = tfrc_lh_peek(lh), *new;
+
+       if (cur != NULL && !tfrc_lh_is_new_loss(cur, tfrc_rx_hist_loss_prev(rh)))
+               return 0;
+
+       new = tfrc_lh_demand_next(lh);
+       if (unlikely(new == NULL)) {
+               DCCP_CRIT("Cannot allocate/add loss record.");
+               return 0;
+       }
+
+       new->li_seqno     = tfrc_rx_hist_loss_prev(rh)->tfrchrx_seqno;
+       new->li_ccval     = tfrc_rx_hist_loss_prev(rh)->tfrchrx_ccval;
+       new->li_is_closed = 0;
+
+       if (++lh->counter == 1)
+               lh->i_mean = new->li_length = (*calc_first_li)(sk);
+       else {
+               cur->li_length = dccp_delta_seqno(cur->li_seqno, new->li_seqno);
+               new->li_length = dccp_delta_seqno(new->li_seqno,
+                                 tfrc_rx_hist_last_rcv(rh)->tfrchrx_seqno) + 1;
+               if (lh->counter > (2*LIH_SIZE))
+                       lh->counter -= LIH_SIZE;
+
+               tfrc_lh_calc_i_mean(lh);
+       }
+       return 1;
+}
+
+int __init tfrc_li_init(void)
+{
+       tfrc_lh_slab = kmem_cache_create("tfrc_li_hist",
+                                        sizeof(struct tfrc_loss_interval), 0,
+                                        SLAB_HWCACHE_ALIGN, NULL);
+       return tfrc_lh_slab == NULL ? -ENOBUFS : 0;
+}
+
+void tfrc_li_exit(void)
+{
+       if (tfrc_lh_slab != NULL) {
+               kmem_cache_destroy(tfrc_lh_slab);
+               tfrc_lh_slab = NULL;
+       }
+}