From: Gerrit Renker Date: Wed, 12 Dec 2007 15:50:51 +0000 (-0200) Subject: [TFRC]: Ringbuffer to track loss interval history X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=8a9c7e92e0ca97632126feee32ba2698b4eb6c8f;p=openwrt%2Fstaging%2Fblogic.git [TFRC]: Ringbuffer to track loss interval history A ringbuffer-based implementation of loss interval history is easier to maintain, allocate, and update. The `swap' routine to keep the RX history sorted is due to and was written by Arnaldo Carvalho de Melo, simplifying an earlier macro-based variant. Details: * access to the Loss Interval Records via macro wrappers (with safety checks); * simplified, on-demand allocation of entries (no extra memory consumption on lossless links); cache allocation is local to the module / exported as service; * provision of RFC-compliant algorithm to re-compute average loss interval; * provision of comprehensive, new loss detection algorithm - support for all cases of loss, including re-ordered/duplicate packets; - waiting for NDUPACK=3 packets to fill the hole; - updating loss records when a late-arriving packet fills a hole. Signed-off-by: Gerrit Renker Signed-off-by: Ian McDonald Signed-off-by: Arnaldo Carvalho de Melo Signed-off-by: David S. Miller --- diff --git a/net/dccp/ccids/lib/loss_interval.c b/net/dccp/ccids/lib/loss_interval.c index c0a933a1d28e..39980d1f5352 100644 --- a/net/dccp/ccids/lib/loss_interval.c +++ b/net/dccp/ccids/lib/loss_interval.c @@ -1,6 +1,7 @@ /* * net/dccp/ccids/lib/loss_interval.c * + * 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 * Copyright (c) 2005 Arnaldo Carvalho de Melo @@ -10,12 +11,7 @@ * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. */ - -#include #include -#include "../../dccp.h" -#include "loss_interval.h" -#include "packet_history.h" #include "tfrc.h" #define DCCP_LI_HIST_IVAL_F_LENGTH 8 @@ -27,6 +23,54 @@ struct dccp_li_hist_entry { u32 dccplih_interval; }; +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; + } +} +EXPORT_SYMBOL_GPL(tfrc_lh_cleanup); + static struct kmem_cache *dccp_li_cachep __read_mostly; static inline struct dccp_li_hist_entry *dccp_li_hist_entry_new(const gfp_t prio) @@ -98,6 +142,65 @@ u32 dccp_li_hist_calc_i_mean(struct list_head *list) EXPORT_SYMBOL_GPL(dccp_li_hist_calc_i_mean); +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 */ + + 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]; + } + + BUG_ON(w_tot == 0); + 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 length; + + if (cur == NULL) /* not initialised */ + return 0; + + length = dccp_delta_seqno(cur->li_seqno, DCCP_SKB_CB(skb)->dccpd_seq); + + if (length - 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 = length; + tfrc_lh_calc_i_mean(lh); + + return (lh->i_mean < old_i_mean); +} +EXPORT_SYMBOL_GPL(tfrc_lh_update_i_mean); + static int dccp_li_hist_interval_new(struct list_head *list, const u64 seq_loss, const u8 win_loss) { @@ -284,6 +387,54 @@ void dccp_li_update_li(struct sock *sk, EXPORT_SYMBOL_GPL(dccp_li_update_li); +/* 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); + if (lh->counter > (2*LIH_SIZE)) + lh->counter -= LIH_SIZE; + + tfrc_lh_calc_i_mean(lh); + } + return 1; +} +EXPORT_SYMBOL_GPL(tfrc_lh_interval_add); + int __init dccp_li_init(void) { dccp_li_cachep = kmem_cache_create("dccp_li_hist", diff --git a/net/dccp/ccids/lib/loss_interval.h b/net/dccp/ccids/lib/loss_interval.h index 27bee92dae13..5e3c5c54a495 100644 --- a/net/dccp/ccids/lib/loss_interval.h +++ b/net/dccp/ccids/lib/loss_interval.h @@ -3,6 +3,7 @@ /* * net/dccp/ccids/lib/loss_interval.h * + * 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 * Copyright (c) 2005 Arnaldo Carvalho de Melo @@ -12,11 +13,64 @@ * Software Foundation; either version 2 of the License, or (at your option) * any later version. */ - #include #include +#include + +/* + * 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); +} extern void dccp_li_hist_purge(struct list_head *list); +struct tfrc_rx_hist; +extern int tfrc_lh_interval_add(struct tfrc_loss_hist *, struct tfrc_rx_hist *, + u32 (*first_li)(struct sock *), struct sock *); +extern u8 tfrc_lh_update_i_mean(struct tfrc_loss_hist *lh, struct sk_buff *); +extern void tfrc_lh_cleanup(struct tfrc_loss_hist *lh); extern u32 dccp_li_hist_calc_i_mean(struct list_head *list); diff --git a/net/dccp/ccids/lib/packet_history.c b/net/dccp/ccids/lib/packet_history.c index dd2cf2d6b8fc..5b10a1ecf138 100644 --- a/net/dccp/ccids/lib/packet_history.c +++ b/net/dccp/ccids/lib/packet_history.c @@ -151,11 +151,10 @@ void tfrc_rx_packet_history_exit(void) } } -void tfrc_rx_hist_add_packet(struct tfrc_rx_hist *h, - const struct sk_buff *skb, - const u32 ndp) +static inline void tfrc_rx_hist_entry_from_skb(struct tfrc_rx_hist_entry *entry, + const struct sk_buff *skb, + const u32 ndp) { - struct tfrc_rx_hist_entry *entry = tfrc_rx_hist_last_rcv(h); const struct dccp_hdr *dh = dccp_hdr(skb); entry->tfrchrx_seqno = DCCP_SKB_CB(skb)->dccpd_seq; @@ -164,6 +163,15 @@ void tfrc_rx_hist_add_packet(struct tfrc_rx_hist *h, 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 u32 ndp) +{ + struct tfrc_rx_hist_entry *entry = tfrc_rx_hist_last_rcv(h); + + tfrc_rx_hist_entry_from_skb(entry, skb, ndp); +} EXPORT_SYMBOL_GPL(tfrc_rx_hist_add_packet); /* has the packet contained in skb been seen before? */ @@ -209,6 +217,208 @@ int tfrc_rx_hist_new_loss_indicated(struct tfrc_rx_hist *h, } EXPORT_SYMBOL_GPL(tfrc_rx_hist_new_loss_indicated); +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); + struct tfrc_rx_hist_entry *tmp = h->ring[idx_a]; + + h->ring[idx_a] = h->ring[idx_b]; + h->ring[idx_b] = tmp; +} + +/* + * 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 __after_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 hist_entry. + */ +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; + int n1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_ndp, + d12 = dccp_delta_seqno(s1, s2), d2; + + if (d12 > 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 */ + d2 = dccp_delta_seqno(s0, s2); + + if (d2 == 1 || n2 >= d2) { /* S2 is direct successor of S0 */ + int d21 = -d12; + + if (d21 == 1 || n1 >= d21) { + /* 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 { /* hole 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; + int n1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_ndp, + d23 = dccp_delta_seqno(s2, s3), d13, d3, d31; + + if (d23 > 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 */ + d13 = dccp_delta_seqno(s1, s3); + + if (d13 > 0) { + /* + * The sequence number order is S1, S3, S2 + * Reorder history to insert entry 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 */ + d31 = -d13; + d3 = dccp_delta_seqno(s0, s3); + + if (d3 == 1 || n3 >= d3) { /* S3 is a successor of S0 */ + + if (d31 == 1 || n1 >= d31) { + /* hole between S0 and S1 filled by S3 */ + int d2 = dccp_delta_seqno(s1, s2), + n2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_ndp; + + if (d2 == 1 || n2 >= d2) { + /* 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: S3 is not a successor of S0. + * Sequence order is S0, S3, S1, S2; reorder to insert 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; +} + +/* return the signed modulo-2^48 sequence number distance from entry e1 to e2 */ +static s64 tfrc_rx_hist_delta_seqno(struct tfrc_rx_hist *h, u8 e1, u8 e2) +{ + DCCP_BUG_ON(e1 > h->loss_count || e2 > h->loss_count); + + return dccp_delta_seqno(tfrc_rx_hist_entry(h, e1)->tfrchrx_seqno, + tfrc_rx_hist_entry(h, e2)->tfrchrx_seqno); +} + +/* recycle RX history records to continue loss detection if necessary */ +static void __three_after_loss(struct tfrc_rx_hist *h) +{ + /* + * The distance between S0 and S1 is always greater than 1 and the NDP + * count of S1 is smaller than this distance. Otherwise there would + * have been no loss. Hence it is only necessary to see whether there + * are further missing data packets between S1/S2 and S2/S3. + */ + int d2 = tfrc_rx_hist_delta_seqno(h, 1, 2), + d3 = tfrc_rx_hist_delta_seqno(h, 2, 3), + n2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_ndp, + n3 = tfrc_rx_hist_entry(h, 3)->tfrchrx_ndp; + + if (d2 == 1 || n2 >= d2) { /* S2 is successor to S1 */ + + if (d3 == 1 || n3 >= d3) { + /* S3 is successor of S2: 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. + */ +int tfrc_rx_handle_loss(struct tfrc_rx_hist *h, + struct tfrc_loss_hist *lh, + struct sk_buff *skb, u32 ndp, + u32 (*calc_first_li)(struct sock *), struct sock *sk) +{ + int is_new_loss = 0; + + 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; +} +EXPORT_SYMBOL_GPL(tfrc_rx_handle_loss); + int tfrc_rx_hist_alloc(struct tfrc_rx_hist *h) { int i; diff --git a/net/dccp/ccids/lib/packet_history.h b/net/dccp/ccids/lib/packet_history.h index e58b0fcdc6ae..24edd8df54b9 100644 --- a/net/dccp/ccids/lib/packet_history.h +++ b/net/dccp/ccids/lib/packet_history.h @@ -36,10 +36,9 @@ #ifndef _DCCP_PKT_HIST_ #define _DCCP_PKT_HIST_ -#include -#include - -struct sk_buff; +#include +#include +#include "tfrc.h" struct tfrc_tx_hist_entry; @@ -125,6 +124,10 @@ extern void tfrc_rx_hist_add_packet(struct tfrc_rx_hist *h, extern int tfrc_rx_hist_duplicate(struct tfrc_rx_hist *h, struct sk_buff *skb); extern int tfrc_rx_hist_new_loss_indicated(struct tfrc_rx_hist *h, const struct sk_buff *skb, u32 ndp); +struct tfrc_loss_hist; +extern int tfrc_rx_handle_loss(struct tfrc_rx_hist *, struct tfrc_loss_hist *, + struct sk_buff *skb, u32 ndp, + u32 (*first_li)(struct sock *), struct sock *); extern u32 tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h, const struct sk_buff *skb); extern int tfrc_rx_hist_alloc(struct tfrc_rx_hist *h); diff --git a/net/dccp/ccids/lib/tfrc.h b/net/dccp/ccids/lib/tfrc.h index ab8848c0f8c9..1fb1187bbf1c 100644 --- a/net/dccp/ccids/lib/tfrc.h +++ b/net/dccp/ccids/lib/tfrc.h @@ -17,6 +17,9 @@ #include #include #include "../../dccp.h" +/* internal includes that this module exports: */ +#include "loss_interval.h" +#include "packet_history.h" #ifdef CONFIG_IP_DCCP_TFRC_DEBUG extern int tfrc_debug;