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-rw-r--r--net/dccp/ccids/lib/loss_interval.c184
-rw-r--r--net/dccp/ccids/lib/loss_interval.h69
-rw-r--r--net/dccp/ccids/lib/packet_history.c439
-rw-r--r--net/dccp/ccids/lib/packet_history.h142
-rw-r--r--net/dccp/ccids/lib/tfrc.c46
-rw-r--r--net/dccp/ccids/lib/tfrc.h73
-rw-r--r--net/dccp/ccids/lib/tfrc_equation.c702
7 files changed, 1655 insertions, 0 deletions
diff --git a/net/dccp/ccids/lib/loss_interval.c b/net/dccp/ccids/lib/loss_interval.c
new file mode 100644
index 000000000..da9531984
--- /dev/null
+++ b/net/dccp/ccids/lib/loss_interval.c
@@ -0,0 +1,184 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * 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>
+ */
+#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
+ * @lh: histogram to update
+ * @skb: received socket triggering loss interval update
+ *
+ * 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;
+ }
+}
diff --git a/net/dccp/ccids/lib/loss_interval.h b/net/dccp/ccids/lib/loss_interval.h
new file mode 100644
index 000000000..c3d95f85e
--- /dev/null
+++ b/net/dccp/ccids/lib/loss_interval.h
@@ -0,0 +1,69 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef _DCCP_LI_HIST_
+#define _DCCP_LI_HIST_
+/*
+ * 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>
+ */
+#include <linux/ktime.h>
+#include <linux/list.h>
+#include <linux/slab.h>
+
+/*
+ * Number of loss intervals (RFC 4342, 8.6.1). The history size is one more than
+ * NINTERVAL, since the `open' interval I_0 is always stored as the first entry.
+ */
+#define NINTERVAL 8
+#define LIH_SIZE (NINTERVAL + 1)
+
+/**
+ * tfrc_loss_interval - Loss history record for TFRC-based protocols
+ * @li_seqno: Highest received seqno before the start of loss
+ * @li_ccval: The CCVal belonging to @li_seqno
+ * @li_is_closed: Whether @li_seqno is older than 1 RTT
+ * @li_length: Loss interval sequence length
+ */
+struct tfrc_loss_interval {
+ u64 li_seqno:48,
+ li_ccval:4,
+ li_is_closed:1;
+ u32 li_length;
+};
+
+/**
+ * tfrc_loss_hist - Loss record database
+ * @ring: Circular queue managed in LIFO manner
+ * @counter: Current count of entries (can be more than %LIH_SIZE)
+ * @i_mean: Current Average Loss Interval [RFC 3448, 5.4]
+ */
+struct tfrc_loss_hist {
+ struct tfrc_loss_interval *ring[LIH_SIZE];
+ u8 counter;
+ u32 i_mean;
+};
+
+static inline void tfrc_lh_init(struct tfrc_loss_hist *lh)
+{
+ memset(lh, 0, sizeof(struct tfrc_loss_hist));
+}
+
+static inline u8 tfrc_lh_is_initialised(struct tfrc_loss_hist *lh)
+{
+ return lh->counter > 0;
+}
+
+static inline u8 tfrc_lh_length(struct tfrc_loss_hist *lh)
+{
+ return min(lh->counter, (u8)LIH_SIZE);
+}
+
+struct tfrc_rx_hist;
+
+int tfrc_lh_interval_add(struct tfrc_loss_hist *, struct tfrc_rx_hist *,
+ u32 (*first_li)(struct sock *), struct sock *);
+u8 tfrc_lh_update_i_mean(struct tfrc_loss_hist *lh, struct sk_buff *);
+void tfrc_lh_cleanup(struct tfrc_loss_hist *lh);
+
+#endif /* _DCCP_LI_HIST_ */
diff --git a/net/dccp/ccids/lib/packet_history.c b/net/dccp/ccids/lib/packet_history.c
new file mode 100644
index 000000000..0cdda3c66
--- /dev/null
+++ b/net/dccp/ccids/lib/packet_history.c
@@ -0,0 +1,439 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2007 The University of Aberdeen, Scotland, UK
+ * Copyright (c) 2005-7 The University of Waikato, Hamilton, New Zealand.
+ *
+ * An implementation of the DCCP protocol
+ *
+ * This code has been developed by the University of Waikato WAND
+ * research group. For further information please see https://www.wand.net.nz/
+ * or e-mail Ian McDonald - ian.mcdonald@jandi.co.nz
+ *
+ * This code also uses code from Lulea University, rereleased as GPL by its
+ * authors:
+ * Copyright (c) 2003 Nils-Erik Mattsson, Joacim Haggmark, Magnus Erixzon
+ *
+ * Changes to meet Linux coding standards, to make it meet latest ccid3 draft
+ * and to make it work as a loadable module in the DCCP stack written by
+ * Arnaldo Carvalho de Melo <acme@conectiva.com.br>.
+ *
+ * Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
+ */
+
+#include <linux/string.h>
+#include <linux/slab.h>
+#include "packet_history.h"
+#include "../../dccp.h"
+
+/*
+ * Transmitter History Routines
+ */
+static struct kmem_cache *tfrc_tx_hist_slab;
+
+int __init tfrc_tx_packet_history_init(void)
+{
+ tfrc_tx_hist_slab = kmem_cache_create("tfrc_tx_hist",
+ sizeof(struct tfrc_tx_hist_entry),
+ 0, SLAB_HWCACHE_ALIGN, NULL);
+ return tfrc_tx_hist_slab == NULL ? -ENOBUFS : 0;
+}
+
+void tfrc_tx_packet_history_exit(void)
+{
+ if (tfrc_tx_hist_slab != NULL) {
+ kmem_cache_destroy(tfrc_tx_hist_slab);
+ tfrc_tx_hist_slab = NULL;
+ }
+}
+
+int tfrc_tx_hist_add(struct tfrc_tx_hist_entry **headp, u64 seqno)
+{
+ struct tfrc_tx_hist_entry *entry = kmem_cache_alloc(tfrc_tx_hist_slab, gfp_any());
+
+ if (entry == NULL)
+ return -ENOBUFS;
+ entry->seqno = seqno;
+ entry->stamp = ktime_get_real();
+ entry->next = *headp;
+ *headp = entry;
+ return 0;
+}
+
+void tfrc_tx_hist_purge(struct tfrc_tx_hist_entry **headp)
+{
+ struct tfrc_tx_hist_entry *head = *headp;
+
+ while (head != NULL) {
+ struct tfrc_tx_hist_entry *next = head->next;
+
+ kmem_cache_free(tfrc_tx_hist_slab, head);
+ head = next;
+ }
+
+ *headp = NULL;
+}
+
+/*
+ * Receiver History Routines
+ */
+static struct kmem_cache *tfrc_rx_hist_slab;
+
+int __init tfrc_rx_packet_history_init(void)
+{
+ tfrc_rx_hist_slab = kmem_cache_create("tfrc_rxh_cache",
+ sizeof(struct tfrc_rx_hist_entry),
+ 0, SLAB_HWCACHE_ALIGN, NULL);
+ return tfrc_rx_hist_slab == NULL ? -ENOBUFS : 0;
+}
+
+void tfrc_rx_packet_history_exit(void)
+{
+ if (tfrc_rx_hist_slab != NULL) {
+ kmem_cache_destroy(tfrc_rx_hist_slab);
+ tfrc_rx_hist_slab = NULL;
+ }
+}
+
+static inline void tfrc_rx_hist_entry_from_skb(struct tfrc_rx_hist_entry *entry,
+ const struct sk_buff *skb,
+ const u64 ndp)
+{
+ const struct dccp_hdr *dh = dccp_hdr(skb);
+
+ entry->tfrchrx_seqno = DCCP_SKB_CB(skb)->dccpd_seq;
+ entry->tfrchrx_ccval = dh->dccph_ccval;
+ entry->tfrchrx_type = dh->dccph_type;
+ entry->tfrchrx_ndp = ndp;
+ entry->tfrchrx_tstamp = ktime_get_real();
+}
+
+void tfrc_rx_hist_add_packet(struct tfrc_rx_hist *h,
+ const struct sk_buff *skb,
+ const u64 ndp)
+{
+ struct tfrc_rx_hist_entry *entry = tfrc_rx_hist_last_rcv(h);
+
+ tfrc_rx_hist_entry_from_skb(entry, skb, ndp);
+}
+
+/* has the packet contained in skb been seen before? */
+int tfrc_rx_hist_duplicate(struct tfrc_rx_hist *h, struct sk_buff *skb)
+{
+ const u64 seq = DCCP_SKB_CB(skb)->dccpd_seq;
+ int i;
+
+ if (dccp_delta_seqno(tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno, seq) <= 0)
+ return 1;
+
+ for (i = 1; i <= h->loss_count; i++)
+ if (tfrc_rx_hist_entry(h, i)->tfrchrx_seqno == seq)
+ return 1;
+
+ return 0;
+}
+
+static void tfrc_rx_hist_swap(struct tfrc_rx_hist *h, const u8 a, const u8 b)
+{
+ const u8 idx_a = tfrc_rx_hist_index(h, a),
+ idx_b = tfrc_rx_hist_index(h, b);
+
+ swap(h->ring[idx_a], h->ring[idx_b]);
+}
+
+/*
+ * Private helper functions for loss detection.
+ *
+ * In the descriptions, `Si' refers to the sequence number of entry number i,
+ * whose NDP count is `Ni' (lower case is used for variables).
+ * Note: All __xxx_loss functions expect that a test against duplicates has been
+ * performed already: the seqno of the skb must not be less than the seqno
+ * of loss_prev; and it must not equal that of any valid history entry.
+ */
+static void __do_track_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u64 n1)
+{
+ u64 s0 = tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno,
+ s1 = DCCP_SKB_CB(skb)->dccpd_seq;
+
+ if (!dccp_loss_free(s0, s1, n1)) { /* gap between S0 and S1 */
+ h->loss_count = 1;
+ tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 1), skb, n1);
+ }
+}
+
+static void __one_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n2)
+{
+ u64 s0 = tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno,
+ s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno,
+ s2 = DCCP_SKB_CB(skb)->dccpd_seq;
+
+ if (likely(dccp_delta_seqno(s1, s2) > 0)) { /* S1 < S2 */
+ h->loss_count = 2;
+ tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 2), skb, n2);
+ return;
+ }
+
+ /* S0 < S2 < S1 */
+
+ if (dccp_loss_free(s0, s2, n2)) {
+ u64 n1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_ndp;
+
+ if (dccp_loss_free(s2, s1, n1)) {
+ /* hole is filled: S0, S2, and S1 are consecutive */
+ h->loss_count = 0;
+ h->loss_start = tfrc_rx_hist_index(h, 1);
+ } else
+ /* gap between S2 and S1: just update loss_prev */
+ tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_loss_prev(h), skb, n2);
+
+ } else { /* gap between S0 and S2 */
+ /*
+ * Reorder history to insert S2 between S0 and S1
+ */
+ tfrc_rx_hist_swap(h, 0, 3);
+ h->loss_start = tfrc_rx_hist_index(h, 3);
+ tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 1), skb, n2);
+ h->loss_count = 2;
+ }
+}
+
+/* return 1 if a new loss event has been identified */
+static int __two_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n3)
+{
+ u64 s0 = tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno,
+ s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno,
+ s2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_seqno,
+ s3 = DCCP_SKB_CB(skb)->dccpd_seq;
+
+ if (likely(dccp_delta_seqno(s2, s3) > 0)) { /* S2 < S3 */
+ h->loss_count = 3;
+ tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 3), skb, n3);
+ return 1;
+ }
+
+ /* S3 < S2 */
+
+ if (dccp_delta_seqno(s1, s3) > 0) { /* S1 < S3 < S2 */
+ /*
+ * Reorder history to insert S3 between S1 and S2
+ */
+ tfrc_rx_hist_swap(h, 2, 3);
+ tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 2), skb, n3);
+ h->loss_count = 3;
+ return 1;
+ }
+
+ /* S0 < S3 < S1 */
+
+ if (dccp_loss_free(s0, s3, n3)) {
+ u64 n1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_ndp;
+
+ if (dccp_loss_free(s3, s1, n1)) {
+ /* hole between S0 and S1 filled by S3 */
+ u64 n2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_ndp;
+
+ if (dccp_loss_free(s1, s2, n2)) {
+ /* entire hole filled by S0, S3, S1, S2 */
+ h->loss_start = tfrc_rx_hist_index(h, 2);
+ h->loss_count = 0;
+ } else {
+ /* gap remains between S1 and S2 */
+ h->loss_start = tfrc_rx_hist_index(h, 1);
+ h->loss_count = 1;
+ }
+
+ } else /* gap exists between S3 and S1, loss_count stays at 2 */
+ tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_loss_prev(h), skb, n3);
+
+ return 0;
+ }
+
+ /*
+ * The remaining case: S0 < S3 < S1 < S2; gap between S0 and S3
+ * Reorder history to insert S3 between S0 and S1.
+ */
+ tfrc_rx_hist_swap(h, 0, 3);
+ h->loss_start = tfrc_rx_hist_index(h, 3);
+ tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 1), skb, n3);
+ h->loss_count = 3;
+
+ return 1;
+}
+
+/* recycle RX history records to continue loss detection if necessary */
+static void __three_after_loss(struct tfrc_rx_hist *h)
+{
+ /*
+ * At this stage we know already that there is a gap between S0 and S1
+ * (since S0 was the highest sequence number received before detecting
+ * the loss). To recycle the loss record, it is thus only necessary to
+ * check for other possible gaps between S1/S2 and between S2/S3.
+ */
+ u64 s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno,
+ s2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_seqno,
+ s3 = tfrc_rx_hist_entry(h, 3)->tfrchrx_seqno;
+ u64 n2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_ndp,
+ n3 = tfrc_rx_hist_entry(h, 3)->tfrchrx_ndp;
+
+ if (dccp_loss_free(s1, s2, n2)) {
+
+ if (dccp_loss_free(s2, s3, n3)) {
+ /* no gap between S2 and S3: entire hole is filled */
+ h->loss_start = tfrc_rx_hist_index(h, 3);
+ h->loss_count = 0;
+ } else {
+ /* gap between S2 and S3 */
+ h->loss_start = tfrc_rx_hist_index(h, 2);
+ h->loss_count = 1;
+ }
+
+ } else { /* gap between S1 and S2 */
+ h->loss_start = tfrc_rx_hist_index(h, 1);
+ h->loss_count = 2;
+ }
+}
+
+/**
+ * tfrc_rx_handle_loss - Loss detection and further processing
+ * @h: The non-empty RX history object
+ * @lh: Loss Intervals database to update
+ * @skb: Currently received packet
+ * @ndp: The NDP count belonging to @skb
+ * @calc_first_li: Caller-dependent computation of first loss interval in @lh
+ * @sk: Used by @calc_first_li (see tfrc_lh_interval_add)
+ *
+ * Chooses action according to pending loss, updates LI database when a new
+ * loss was detected, and does required post-processing. Returns 1 when caller
+ * should send feedback, 0 otherwise.
+ * Since it also takes care of reordering during loss detection and updates the
+ * records accordingly, the caller should not perform any more RX history
+ * operations when loss_count is greater than 0 after calling this function.
+ */
+int tfrc_rx_handle_loss(struct tfrc_rx_hist *h,
+ struct tfrc_loss_hist *lh,
+ struct sk_buff *skb, const u64 ndp,
+ u32 (*calc_first_li)(struct sock *), struct sock *sk)
+{
+ int is_new_loss = 0;
+
+ if (h->loss_count == 0) {
+ __do_track_loss(h, skb, ndp);
+ } else if (h->loss_count == 1) {
+ __one_after_loss(h, skb, ndp);
+ } else if (h->loss_count != 2) {
+ DCCP_BUG("invalid loss_count %d", h->loss_count);
+ } else if (__two_after_loss(h, skb, ndp)) {
+ /*
+ * Update Loss Interval database and recycle RX records
+ */
+ is_new_loss = tfrc_lh_interval_add(lh, h, calc_first_li, sk);
+ __three_after_loss(h);
+ }
+ return is_new_loss;
+}
+
+int tfrc_rx_hist_alloc(struct tfrc_rx_hist *h)
+{
+ int i;
+
+ for (i = 0; i <= TFRC_NDUPACK; i++) {
+ h->ring[i] = kmem_cache_alloc(tfrc_rx_hist_slab, GFP_ATOMIC);
+ if (h->ring[i] == NULL)
+ goto out_free;
+ }
+
+ h->loss_count = h->loss_start = 0;
+ return 0;
+
+out_free:
+ while (i-- != 0) {
+ kmem_cache_free(tfrc_rx_hist_slab, h->ring[i]);
+ h->ring[i] = NULL;
+ }
+ return -ENOBUFS;
+}
+
+void tfrc_rx_hist_purge(struct tfrc_rx_hist *h)
+{
+ int i;
+
+ for (i = 0; i <= TFRC_NDUPACK; ++i)
+ if (h->ring[i] != NULL) {
+ kmem_cache_free(tfrc_rx_hist_slab, h->ring[i]);
+ h->ring[i] = NULL;
+ }
+}
+
+/**
+ * tfrc_rx_hist_rtt_last_s - reference entry to compute RTT samples against
+ * @h: The non-empty RX history object
+ */
+static inline struct tfrc_rx_hist_entry *
+ tfrc_rx_hist_rtt_last_s(const struct tfrc_rx_hist *h)
+{
+ return h->ring[0];
+}
+
+/**
+ * tfrc_rx_hist_rtt_prev_s - previously suitable (wrt rtt_last_s) RTT-sampling entry
+ * @h: The non-empty RX history object
+ */
+static inline struct tfrc_rx_hist_entry *
+ tfrc_rx_hist_rtt_prev_s(const struct tfrc_rx_hist *h)
+{
+ return h->ring[h->rtt_sample_prev];
+}
+
+/**
+ * tfrc_rx_hist_sample_rtt - Sample RTT from timestamp / CCVal
+ * @h: receive histogram
+ * @skb: packet containing timestamp.
+ *
+ * Based on ideas presented in RFC 4342, 8.1. Returns 0 if it was not able
+ * to compute a sample with given data - calling function should check this.
+ */
+u32 tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h, const struct sk_buff *skb)
+{
+ u32 sample = 0,
+ delta_v = SUB16(dccp_hdr(skb)->dccph_ccval,
+ tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
+
+ if (delta_v < 1 || delta_v > 4) { /* unsuitable CCVal delta */
+ if (h->rtt_sample_prev == 2) { /* previous candidate stored */
+ sample = SUB16(tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_ccval,
+ tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
+ if (sample)
+ sample = 4 / sample *
+ ktime_us_delta(tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_tstamp,
+ tfrc_rx_hist_rtt_last_s(h)->tfrchrx_tstamp);
+ else /*
+ * FIXME: This condition is in principle not
+ * possible but occurs when CCID is used for
+ * two-way data traffic. I have tried to trace
+ * it, but the cause does not seem to be here.
+ */
+ DCCP_BUG("please report to dccp@vger.kernel.org"
+ " => prev = %u, last = %u",
+ tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_ccval,
+ tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval);
+ } else if (delta_v < 1) {
+ h->rtt_sample_prev = 1;
+ goto keep_ref_for_next_time;
+ }
+
+ } else if (delta_v == 4) /* optimal match */
+ sample = ktime_to_us(net_timedelta(tfrc_rx_hist_rtt_last_s(h)->tfrchrx_tstamp));
+ else { /* suboptimal match */
+ h->rtt_sample_prev = 2;
+ goto keep_ref_for_next_time;
+ }
+
+ if (unlikely(sample > DCCP_SANE_RTT_MAX)) {
+ DCCP_WARN("RTT sample %u too large, using max\n", sample);
+ sample = DCCP_SANE_RTT_MAX;
+ }
+
+ h->rtt_sample_prev = 0; /* use current entry as next reference */
+keep_ref_for_next_time:
+
+ return sample;
+}
diff --git a/net/dccp/ccids/lib/packet_history.h b/net/dccp/ccids/lib/packet_history.h
new file mode 100644
index 000000000..159cc9326
--- /dev/null
+++ b/net/dccp/ccids/lib/packet_history.h
@@ -0,0 +1,142 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Packet RX/TX history data structures and routines for TFRC-based protocols.
+ *
+ * Copyright (c) 2007 The University of Aberdeen, Scotland, UK
+ * Copyright (c) 2005-6 The University of Waikato, Hamilton, New Zealand.
+ *
+ * This code has been developed by the University of Waikato WAND
+ * research group. For further information please see https://www.wand.net.nz/
+ * or e-mail Ian McDonald - ian.mcdonald@jandi.co.nz
+ *
+ * This code also uses code from Lulea University, rereleased as GPL by its
+ * authors:
+ * Copyright (c) 2003 Nils-Erik Mattsson, Joacim Haggmark, Magnus Erixzon
+ *
+ * Changes to meet Linux coding standards, to make it meet latest ccid3 draft
+ * and to make it work as a loadable module in the DCCP stack written by
+ * Arnaldo Carvalho de Melo <acme@conectiva.com.br>.
+ *
+ * Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
+ */
+
+#ifndef _DCCP_PKT_HIST_
+#define _DCCP_PKT_HIST_
+
+#include <linux/list.h>
+#include <linux/slab.h>
+#include "tfrc.h"
+
+/**
+ * tfrc_tx_hist_entry - Simple singly-linked TX history list
+ * @next: next oldest entry (LIFO order)
+ * @seqno: sequence number of this entry
+ * @stamp: send time of packet with sequence number @seqno
+ */
+struct tfrc_tx_hist_entry {
+ struct tfrc_tx_hist_entry *next;
+ u64 seqno;
+ ktime_t stamp;
+};
+
+static inline struct tfrc_tx_hist_entry *
+ tfrc_tx_hist_find_entry(struct tfrc_tx_hist_entry *head, u64 seqno)
+{
+ while (head != NULL && head->seqno != seqno)
+ head = head->next;
+ return head;
+}
+
+int tfrc_tx_hist_add(struct tfrc_tx_hist_entry **headp, u64 seqno);
+void tfrc_tx_hist_purge(struct tfrc_tx_hist_entry **headp);
+
+/* Subtraction a-b modulo-16, respects circular wrap-around */
+#define SUB16(a, b) (((a) + 16 - (b)) & 0xF)
+
+/* Number of packets to wait after a missing packet (RFC 4342, 6.1) */
+#define TFRC_NDUPACK 3
+
+/**
+ * tfrc_rx_hist_entry - Store information about a single received packet
+ * @tfrchrx_seqno: DCCP packet sequence number
+ * @tfrchrx_ccval: window counter value of packet (RFC 4342, 8.1)
+ * @tfrchrx_ndp: the NDP count (if any) of the packet
+ * @tfrchrx_tstamp: actual receive time of packet
+ */
+struct tfrc_rx_hist_entry {
+ u64 tfrchrx_seqno:48,
+ tfrchrx_ccval:4,
+ tfrchrx_type:4;
+ u64 tfrchrx_ndp:48;
+ ktime_t tfrchrx_tstamp;
+};
+
+/**
+ * tfrc_rx_hist - RX history structure for TFRC-based protocols
+ * @ring: Packet history for RTT sampling and loss detection
+ * @loss_count: Number of entries in circular history
+ * @loss_start: Movable index (for loss detection)
+ * @rtt_sample_prev: Used during RTT sampling, points to candidate entry
+ */
+struct tfrc_rx_hist {
+ struct tfrc_rx_hist_entry *ring[TFRC_NDUPACK + 1];
+ u8 loss_count:2,
+ loss_start:2;
+#define rtt_sample_prev loss_start
+};
+
+/**
+ * tfrc_rx_hist_index - index to reach n-th entry after loss_start
+ */
+static inline u8 tfrc_rx_hist_index(const struct tfrc_rx_hist *h, const u8 n)
+{
+ return (h->loss_start + n) & TFRC_NDUPACK;
+}
+
+/**
+ * tfrc_rx_hist_last_rcv - entry with highest-received-seqno so far
+ */
+static inline struct tfrc_rx_hist_entry *
+ tfrc_rx_hist_last_rcv(const struct tfrc_rx_hist *h)
+{
+ return h->ring[tfrc_rx_hist_index(h, h->loss_count)];
+}
+
+/**
+ * tfrc_rx_hist_entry - return the n-th history entry after loss_start
+ */
+static inline struct tfrc_rx_hist_entry *
+ tfrc_rx_hist_entry(const struct tfrc_rx_hist *h, const u8 n)
+{
+ return h->ring[tfrc_rx_hist_index(h, n)];
+}
+
+/**
+ * tfrc_rx_hist_loss_prev - entry with highest-received-seqno before loss was detected
+ */
+static inline struct tfrc_rx_hist_entry *
+ tfrc_rx_hist_loss_prev(const struct tfrc_rx_hist *h)
+{
+ return h->ring[h->loss_start];
+}
+
+/* indicate whether previously a packet was detected missing */
+static inline bool tfrc_rx_hist_loss_pending(const struct tfrc_rx_hist *h)
+{
+ return h->loss_count > 0;
+}
+
+void tfrc_rx_hist_add_packet(struct tfrc_rx_hist *h, const struct sk_buff *skb,
+ const u64 ndp);
+
+int tfrc_rx_hist_duplicate(struct tfrc_rx_hist *h, struct sk_buff *skb);
+
+struct tfrc_loss_hist;
+int tfrc_rx_handle_loss(struct tfrc_rx_hist *h, struct tfrc_loss_hist *lh,
+ struct sk_buff *skb, const u64 ndp,
+ u32 (*first_li)(struct sock *sk), struct sock *sk);
+u32 tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h, const struct sk_buff *skb);
+int tfrc_rx_hist_alloc(struct tfrc_rx_hist *h);
+void tfrc_rx_hist_purge(struct tfrc_rx_hist *h);
+
+#endif /* _DCCP_PKT_HIST_ */
diff --git a/net/dccp/ccids/lib/tfrc.c b/net/dccp/ccids/lib/tfrc.c
new file mode 100644
index 000000000..d7f265e1f
--- /dev/null
+++ b/net/dccp/ccids/lib/tfrc.c
@@ -0,0 +1,46 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * TFRC library initialisation
+ *
+ * Copyright (c) 2007 The University of Aberdeen, Scotland, UK
+ * Copyright (c) 2007 Arnaldo Carvalho de Melo <acme@redhat.com>
+ */
+#include <linux/moduleparam.h>
+#include "tfrc.h"
+
+#ifdef CONFIG_IP_DCCP_TFRC_DEBUG
+bool tfrc_debug;
+module_param(tfrc_debug, bool, 0644);
+MODULE_PARM_DESC(tfrc_debug, "Enable TFRC debug messages");
+#endif
+
+int __init tfrc_lib_init(void)
+{
+ int rc = tfrc_li_init();
+
+ if (rc)
+ goto out;
+
+ rc = tfrc_tx_packet_history_init();
+ if (rc)
+ goto out_free_loss_intervals;
+
+ rc = tfrc_rx_packet_history_init();
+ if (rc)
+ goto out_free_tx_history;
+ return 0;
+
+out_free_tx_history:
+ tfrc_tx_packet_history_exit();
+out_free_loss_intervals:
+ tfrc_li_exit();
+out:
+ return rc;
+}
+
+void tfrc_lib_exit(void)
+{
+ tfrc_rx_packet_history_exit();
+ tfrc_tx_packet_history_exit();
+ tfrc_li_exit();
+}
diff --git a/net/dccp/ccids/lib/tfrc.h b/net/dccp/ccids/lib/tfrc.h
new file mode 100644
index 000000000..0a63e8750
--- /dev/null
+++ b/net/dccp/ccids/lib/tfrc.h
@@ -0,0 +1,73 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef _TFRC_H_
+#define _TFRC_H_
+/*
+ * Copyright (c) 2007 The University of Aberdeen, Scotland, UK
+ * Copyright (c) 2005-6 The University of Waikato, Hamilton, New Zealand.
+ * Copyright (c) 2005-6 Ian McDonald <ian.mcdonald@jandi.co.nz>
+ * Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
+ * Copyright (c) 2003 Nils-Erik Mattsson, Joacim Haggmark, Magnus Erixzon
+ */
+#include <linux/types.h>
+#include <linux/math64.h>
+#include "../../dccp.h"
+
+/* internal includes that this library exports: */
+#include "loss_interval.h"
+#include "packet_history.h"
+
+#ifdef CONFIG_IP_DCCP_TFRC_DEBUG
+extern bool tfrc_debug;
+#define tfrc_pr_debug(format, a...) DCCP_PR_DEBUG(tfrc_debug, format, ##a)
+#else
+#define tfrc_pr_debug(format, a...)
+#endif
+
+/* integer-arithmetic divisions of type (a * 1000000)/b */
+static inline u64 scaled_div(u64 a, u64 b)
+{
+ BUG_ON(b == 0);
+ return div64_u64(a * 1000000, b);
+}
+
+static inline u32 scaled_div32(u64 a, u64 b)
+{
+ u64 result = scaled_div(a, b);
+
+ if (result > UINT_MAX) {
+ DCCP_CRIT("Overflow: %llu/%llu > UINT_MAX",
+ (unsigned long long)a, (unsigned long long)b);
+ return UINT_MAX;
+ }
+ return result;
+}
+
+/**
+ * tfrc_ewma - Exponentially weighted moving average
+ * @weight: Weight to be used as damping factor, in units of 1/10
+ */
+static inline u32 tfrc_ewma(const u32 avg, const u32 newval, const u8 weight)
+{
+ return avg ? (weight * avg + (10 - weight) * newval) / 10 : newval;
+}
+
+u32 tfrc_calc_x(u16 s, u32 R, u32 p);
+u32 tfrc_calc_x_reverse_lookup(u32 fvalue);
+u32 tfrc_invert_loss_event_rate(u32 loss_event_rate);
+
+int tfrc_tx_packet_history_init(void);
+void tfrc_tx_packet_history_exit(void);
+int tfrc_rx_packet_history_init(void);
+void tfrc_rx_packet_history_exit(void);
+
+int tfrc_li_init(void);
+void tfrc_li_exit(void);
+
+#ifdef CONFIG_IP_DCCP_TFRC_LIB
+int tfrc_lib_init(void);
+void tfrc_lib_exit(void);
+#else
+#define tfrc_lib_init() (0)
+#define tfrc_lib_exit()
+#endif
+#endif /* _TFRC_H_ */
diff --git a/net/dccp/ccids/lib/tfrc_equation.c b/net/dccp/ccids/lib/tfrc_equation.c
new file mode 100644
index 000000000..92a8c6bea
--- /dev/null
+++ b/net/dccp/ccids/lib/tfrc_equation.c
@@ -0,0 +1,702 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2005 The University of Waikato, Hamilton, New Zealand.
+ * Copyright (c) 2005 Ian McDonald <ian.mcdonald@jandi.co.nz>
+ * Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
+ * Copyright (c) 2003 Nils-Erik Mattsson, Joacim Haggmark, Magnus Erixzon
+ */
+
+#include <linux/module.h>
+#include "../../dccp.h"
+#include "tfrc.h"
+
+#define TFRC_CALC_X_ARRSIZE 500
+#define TFRC_CALC_X_SPLIT 50000 /* 0.05 * 1000000, details below */
+#define TFRC_SMALLEST_P (TFRC_CALC_X_SPLIT/TFRC_CALC_X_ARRSIZE)
+
+/*
+ TFRC TCP Reno Throughput Equation Lookup Table for f(p)
+
+ The following two-column lookup table implements a part of the TCP throughput
+ equation from [RFC 3448, sec. 3.1]:
+
+ s
+ X_calc = --------------------------------------------------------------
+ R * sqrt(2*b*p/3) + (3 * t_RTO * sqrt(3*b*p/8) * (p + 32*p^3))
+
+ Where:
+ X is the transmit rate in bytes/second
+ s is the packet size in bytes
+ R is the round trip time in seconds
+ p is the loss event rate, between 0 and 1.0, of the number of loss
+ events as a fraction of the number of packets transmitted
+ t_RTO is the TCP retransmission timeout value in seconds
+ b is the number of packets acknowledged by a single TCP ACK
+
+ We can assume that b = 1 and t_RTO is 4 * R. The equation now becomes:
+
+ s
+ X_calc = -------------------------------------------------------
+ R * sqrt(p*2/3) + (12 * R * sqrt(p*3/8) * (p + 32*p^3))
+
+ which we can break down into:
+
+ s
+ X_calc = ---------
+ R * f(p)
+
+ where f(p) is given for 0 < p <= 1 by:
+
+ f(p) = sqrt(2*p/3) + 12 * sqrt(3*p/8) * (p + 32*p^3)
+
+ Since this is kernel code, floating-point arithmetic is avoided in favour of
+ integer arithmetic. This means that nearly all fractional parameters are
+ scaled by 1000000:
+ * the parameters p and R
+ * the return result f(p)
+ The lookup table therefore actually tabulates the following function g(q):
+
+ g(q) = 1000000 * f(q/1000000)
+
+ Hence, when p <= 1, q must be less than or equal to 1000000. To achieve finer
+ granularity for the practically more relevant case of small values of p (up to
+ 5%), the second column is used; the first one ranges up to 100%. This split
+ corresponds to the value of q = TFRC_CALC_X_SPLIT. At the same time this also
+ determines the smallest resolution possible with this lookup table:
+
+ TFRC_SMALLEST_P = TFRC_CALC_X_SPLIT / TFRC_CALC_X_ARRSIZE
+
+ The entire table is generated by:
+ for(i=0; i < TFRC_CALC_X_ARRSIZE; i++) {
+ lookup[i][0] = g((i+1) * 1000000/TFRC_CALC_X_ARRSIZE);
+ lookup[i][1] = g((i+1) * TFRC_CALC_X_SPLIT/TFRC_CALC_X_ARRSIZE);
+ }
+
+ With the given configuration, we have, with M = TFRC_CALC_X_ARRSIZE-1,
+ lookup[0][0] = g(1000000/(M+1)) = 1000000 * f(0.2%)
+ lookup[M][0] = g(1000000) = 1000000 * f(100%)
+ lookup[0][1] = g(TFRC_SMALLEST_P) = 1000000 * f(0.01%)
+ lookup[M][1] = g(TFRC_CALC_X_SPLIT) = 1000000 * f(5%)
+
+ In summary, the two columns represent f(p) for the following ranges:
+ * The first column is for 0.002 <= p <= 1.0
+ * The second column is for 0.0001 <= p <= 0.05
+ Where the columns overlap, the second (finer-grained) is given preference,
+ i.e. the first column is used only for p >= 0.05.
+ */
+static const u32 tfrc_calc_x_lookup[TFRC_CALC_X_ARRSIZE][2] = {
+ { 37172, 8172 },
+ { 53499, 11567 },
+ { 66664, 14180 },
+ { 78298, 16388 },
+ { 89021, 18339 },
+ { 99147, 20108 },
+ { 108858, 21738 },
+ { 118273, 23260 },
+ { 127474, 24693 },
+ { 136520, 26052 },
+ { 145456, 27348 },
+ { 154316, 28589 },
+ { 163130, 29783 },
+ { 171919, 30935 },
+ { 180704, 32049 },
+ { 189502, 33130 },
+ { 198328, 34180 },
+ { 207194, 35202 },
+ { 216114, 36198 },
+ { 225097, 37172 },
+ { 234153, 38123 },
+ { 243294, 39055 },
+ { 252527, 39968 },
+ { 261861, 40864 },
+ { 271305, 41743 },
+ { 280866, 42607 },
+ { 290553, 43457 },
+ { 300372, 44293 },
+ { 310333, 45117 },
+ { 320441, 45929 },
+ { 330705, 46729 },
+ { 341131, 47518 },
+ { 351728, 48297 },
+ { 362501, 49066 },
+ { 373460, 49826 },
+ { 384609, 50577 },
+ { 395958, 51320 },
+ { 407513, 52054 },
+ { 419281, 52780 },
+ { 431270, 53499 },
+ { 443487, 54211 },
+ { 455940, 54916 },
+ { 468635, 55614 },
+ { 481581, 56306 },
+ { 494785, 56991 },
+ { 508254, 57671 },
+ { 521996, 58345 },
+ { 536019, 59014 },
+ { 550331, 59677 },
+ { 564939, 60335 },
+ { 579851, 60988 },
+ { 595075, 61636 },
+ { 610619, 62279 },
+ { 626491, 62918 },
+ { 642700, 63553 },
+ { 659253, 64183 },
+ { 676158, 64809 },
+ { 693424, 65431 },
+ { 711060, 66050 },
+ { 729073, 66664 },
+ { 747472, 67275 },
+ { 766266, 67882 },
+ { 785464, 68486 },
+ { 805073, 69087 },
+ { 825103, 69684 },
+ { 845562, 70278 },
+ { 866460, 70868 },
+ { 887805, 71456 },
+ { 909606, 72041 },
+ { 931873, 72623 },
+ { 954614, 73202 },
+ { 977839, 73778 },
+ { 1001557, 74352 },
+ { 1025777, 74923 },
+ { 1050508, 75492 },
+ { 1075761, 76058 },
+ { 1101544, 76621 },
+ { 1127867, 77183 },
+ { 1154739, 77741 },
+ { 1182172, 78298 },
+ { 1210173, 78852 },
+ { 1238753, 79405 },
+ { 1267922, 79955 },
+ { 1297689, 80503 },
+ { 1328066, 81049 },
+ { 1359060, 81593 },
+ { 1390684, 82135 },
+ { 1422947, 82675 },
+ { 1455859, 83213 },
+ { 1489430, 83750 },
+ { 1523671, 84284 },
+ { 1558593, 84817 },
+ { 1594205, 85348 },
+ { 1630518, 85878 },
+ { 1667543, 86406 },
+ { 1705290, 86932 },
+ { 1743770, 87457 },
+ { 1782994, 87980 },
+ { 1822973, 88501 },
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+};
+
+/* return largest index i such that fval <= lookup[i][small] */
+static inline u32 tfrc_binsearch(u32 fval, u8 small)
+{
+ u32 try, low = 0, high = TFRC_CALC_X_ARRSIZE - 1;
+
+ while (low < high) {
+ try = (low + high) / 2;
+ if (fval <= tfrc_calc_x_lookup[try][small])
+ high = try;
+ else
+ low = try + 1;
+ }
+ return high;
+}
+
+/**
+ * tfrc_calc_x - Calculate the send rate as per section 3.1 of RFC3448
+ * @s: packet size in bytes
+ * @R: RTT scaled by 1000000 (i.e., microseconds)
+ * @p: loss ratio estimate scaled by 1000000
+ *
+ * Returns X_calc in bytes per second (not scaled).
+ */
+u32 tfrc_calc_x(u16 s, u32 R, u32 p)
+{
+ u16 index;
+ u32 f;
+ u64 result;
+
+ /* check against invalid parameters and divide-by-zero */
+ BUG_ON(p > 1000000); /* p must not exceed 100% */
+ BUG_ON(p == 0); /* f(0) = 0, divide by zero */
+ if (R == 0) { /* possible divide by zero */
+ DCCP_CRIT("WARNING: RTT is 0, returning maximum X_calc.");
+ return ~0U;
+ }
+
+ if (p <= TFRC_CALC_X_SPLIT) { /* 0.0000 < p <= 0.05 */
+ if (p < TFRC_SMALLEST_P) { /* 0.0000 < p < 0.0001 */
+ DCCP_WARN("Value of p (%d) below resolution. "
+ "Substituting %d\n", p, TFRC_SMALLEST_P);
+ index = 0;
+ } else /* 0.0001 <= p <= 0.05 */
+ index = p/TFRC_SMALLEST_P - 1;
+
+ f = tfrc_calc_x_lookup[index][1];
+
+ } else { /* 0.05 < p <= 1.00 */
+ index = p/(1000000/TFRC_CALC_X_ARRSIZE) - 1;
+
+ f = tfrc_calc_x_lookup[index][0];
+ }
+
+ /*
+ * Compute X = s/(R*f(p)) in bytes per second.
+ * Since f(p) and R are both scaled by 1000000, we need to multiply by
+ * 1000000^2. To avoid overflow, the result is computed in two stages.
+ * This works under almost all reasonable operational conditions, for a
+ * wide range of parameters. Yet, should some strange combination of
+ * parameters result in overflow, the use of scaled_div32 will catch
+ * this and return UINT_MAX - which is a logically adequate consequence.
+ */
+ result = scaled_div(s, R);
+ return scaled_div32(result, f);
+}
+
+/**
+ * tfrc_calc_x_reverse_lookup - try to find p given f(p)
+ * @fvalue: function value to match, scaled by 1000000
+ *
+ * Returns closest match for p, also scaled by 1000000
+ */
+u32 tfrc_calc_x_reverse_lookup(u32 fvalue)
+{
+ int index;
+
+ if (fvalue == 0) /* f(p) = 0 whenever p = 0 */
+ return 0;
+
+ /* Error cases. */
+ if (fvalue < tfrc_calc_x_lookup[0][1]) {
+ DCCP_WARN("fvalue %u smaller than resolution\n", fvalue);
+ return TFRC_SMALLEST_P;
+ }
+ if (fvalue > tfrc_calc_x_lookup[TFRC_CALC_X_ARRSIZE - 1][0]) {
+ DCCP_WARN("fvalue %u exceeds bounds!\n", fvalue);
+ return 1000000;
+ }
+
+ if (fvalue <= tfrc_calc_x_lookup[TFRC_CALC_X_ARRSIZE - 1][1]) {
+ index = tfrc_binsearch(fvalue, 1);
+ return (index + 1) * TFRC_CALC_X_SPLIT / TFRC_CALC_X_ARRSIZE;
+ }
+
+ /* else ... it must be in the coarse-grained column */
+ index = tfrc_binsearch(fvalue, 0);
+ return (index + 1) * 1000000 / TFRC_CALC_X_ARRSIZE;
+}
+
+/**
+ * tfrc_invert_loss_event_rate - Compute p so that 10^6 corresponds to 100%
+ * @loss_event_rate: loss event rate to invert
+ * When @loss_event_rate is large, there is a chance that p is truncated to 0.
+ * To avoid re-entering slow-start in that case, we set p = TFRC_SMALLEST_P > 0.
+ */
+u32 tfrc_invert_loss_event_rate(u32 loss_event_rate)
+{
+ if (loss_event_rate == UINT_MAX) /* see RFC 4342, 8.5 */
+ return 0;
+ if (unlikely(loss_event_rate == 0)) /* map 1/0 into 100% */
+ return 1000000;
+ return max_t(u32, scaled_div(1, loss_event_rate), TFRC_SMALLEST_P);
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-06-22 07:40:31 +0000