diff options
Diffstat (limited to 'net/dccp/ccids/lib')
| -rw-r--r-- | net/dccp/ccids/lib/loss_interval.c | 8 | ||||
| -rw-r--r-- | net/dccp/ccids/lib/loss_interval.h | 2 | ||||
| -rw-r--r-- | net/dccp/ccids/lib/packet_history.c | 219 | ||||
| -rw-r--r-- | net/dccp/ccids/lib/packet_history.h | 130 | ||||
| -rw-r--r-- | net/dccp/ccids/lib/tfrc.h | 23 | ||||
| -rw-r--r-- | net/dccp/ccids/lib/tfrc_equation.c | 241 |
6 files changed, 355 insertions, 268 deletions
diff --git a/net/dccp/ccids/lib/loss_interval.c b/net/dccp/ccids/lib/loss_interval.c index 906c81ab9d4f..0a0baef16b3e 100644 --- a/net/dccp/ccids/lib/loss_interval.c +++ b/net/dccp/ccids/lib/loss_interval.c @@ -13,7 +13,7 @@ #include <linux/module.h> #include <net/sock.h> - +#include "../../dccp.h" #include "loss_interval.h" struct dccp_li_hist *dccp_li_hist_new(const char *name) @@ -109,7 +109,7 @@ u32 dccp_li_hist_calc_i_mean(struct list_head *list) i_tot = max(i_tot0, i_tot1); if (!w_tot) { - LIMIT_NETDEBUG(KERN_WARNING "%s: w_tot = 0\n", __FUNCTION__); + DCCP_WARN("w_tot = 0\n"); return 1; } @@ -125,10 +125,10 @@ int dccp_li_hist_interval_new(struct dccp_li_hist *hist, int i; for (i = 0; i < DCCP_LI_HIST_IVAL_F_LENGTH; i++) { - entry = dccp_li_hist_entry_new(hist, SLAB_ATOMIC); + entry = dccp_li_hist_entry_new(hist, GFP_ATOMIC); if (entry == NULL) { dccp_li_hist_purge(hist, list); - dump_stack(); + DCCP_BUG("loss interval list entry is NULL"); return 0; } entry->dccplih_interval = ~0; diff --git a/net/dccp/ccids/lib/loss_interval.h b/net/dccp/ccids/lib/loss_interval.h index 0ae85f0340b2..eb257014dd74 100644 --- a/net/dccp/ccids/lib/loss_interval.h +++ b/net/dccp/ccids/lib/loss_interval.h @@ -20,7 +20,7 @@ #define DCCP_LI_HIST_IVAL_F_LENGTH 8 struct dccp_li_hist { - kmem_cache_t *dccplih_slab; + struct kmem_cache *dccplih_slab; }; extern struct dccp_li_hist *dccp_li_hist_new(const char *name); diff --git a/net/dccp/ccids/lib/packet_history.c b/net/dccp/ccids/lib/packet_history.c index b876c9c81c65..2e8ef42721e2 100644 --- a/net/dccp/ccids/lib/packet_history.c +++ b/net/dccp/ccids/lib/packet_history.c @@ -36,9 +36,100 @@ #include <linux/module.h> #include <linux/string.h> - #include "packet_history.h" +/* + * Transmitter History Routines + */ +struct dccp_tx_hist *dccp_tx_hist_new(const char *name) +{ + struct dccp_tx_hist *hist = kmalloc(sizeof(*hist), GFP_ATOMIC); + static const char dccp_tx_hist_mask[] = "tx_hist_%s"; + char *slab_name; + + if (hist == NULL) + goto out; + + slab_name = kmalloc(strlen(name) + sizeof(dccp_tx_hist_mask) - 1, + GFP_ATOMIC); + if (slab_name == NULL) + goto out_free_hist; + + sprintf(slab_name, dccp_tx_hist_mask, name); + hist->dccptxh_slab = kmem_cache_create(slab_name, + sizeof(struct dccp_tx_hist_entry), + 0, SLAB_HWCACHE_ALIGN, + NULL, NULL); + if (hist->dccptxh_slab == NULL) + goto out_free_slab_name; +out: + return hist; +out_free_slab_name: + kfree(slab_name); +out_free_hist: + kfree(hist); + hist = NULL; + goto out; +} + +EXPORT_SYMBOL_GPL(dccp_tx_hist_new); + +void dccp_tx_hist_delete(struct dccp_tx_hist *hist) +{ + const char* name = kmem_cache_name(hist->dccptxh_slab); + + kmem_cache_destroy(hist->dccptxh_slab); + kfree(name); + kfree(hist); +} + +EXPORT_SYMBOL_GPL(dccp_tx_hist_delete); + +struct dccp_tx_hist_entry * + dccp_tx_hist_find_entry(const struct list_head *list, const u64 seq) +{ + struct dccp_tx_hist_entry *packet = NULL, *entry; + + list_for_each_entry(entry, list, dccphtx_node) + if (entry->dccphtx_seqno == seq) { + packet = entry; + break; + } + + return packet; +} + +EXPORT_SYMBOL_GPL(dccp_tx_hist_find_entry); + +void dccp_tx_hist_purge(struct dccp_tx_hist *hist, struct list_head *list) +{ + struct dccp_tx_hist_entry *entry, *next; + + list_for_each_entry_safe(entry, next, list, dccphtx_node) { + list_del_init(&entry->dccphtx_node); + dccp_tx_hist_entry_delete(hist, entry); + } +} + +EXPORT_SYMBOL_GPL(dccp_tx_hist_purge); + +void dccp_tx_hist_purge_older(struct dccp_tx_hist *hist, + struct list_head *list, + struct dccp_tx_hist_entry *packet) +{ + struct dccp_tx_hist_entry *next; + + list_for_each_entry_safe_continue(packet, next, list, dccphtx_node) { + list_del_init(&packet->dccphtx_node); + dccp_tx_hist_entry_delete(hist, packet); + } +} + +EXPORT_SYMBOL_GPL(dccp_tx_hist_purge_older); + +/* + * Receiver History Routines + */ struct dccp_rx_hist *dccp_rx_hist_new(const char *name) { struct dccp_rx_hist *hist = kmalloc(sizeof(*hist), GFP_ATOMIC); @@ -83,18 +174,24 @@ void dccp_rx_hist_delete(struct dccp_rx_hist *hist) EXPORT_SYMBOL_GPL(dccp_rx_hist_delete); -void dccp_rx_hist_purge(struct dccp_rx_hist *hist, struct list_head *list) +int dccp_rx_hist_find_entry(const struct list_head *list, const u64 seq, + u8 *ccval) { - struct dccp_rx_hist_entry *entry, *next; + struct dccp_rx_hist_entry *packet = NULL, *entry; - list_for_each_entry_safe(entry, next, list, dccphrx_node) { - list_del_init(&entry->dccphrx_node); - kmem_cache_free(hist->dccprxh_slab, entry); - } -} + list_for_each_entry(entry, list, dccphrx_node) + if (entry->dccphrx_seqno == seq) { + packet = entry; + break; + } -EXPORT_SYMBOL_GPL(dccp_rx_hist_purge); + if (packet) + *ccval = packet->dccphrx_ccval; + return packet != NULL; +} + +EXPORT_SYMBOL_GPL(dccp_rx_hist_find_entry); struct dccp_rx_hist_entry * dccp_rx_hist_find_data_packet(const struct list_head *list) { @@ -184,110 +281,18 @@ void dccp_rx_hist_add_packet(struct dccp_rx_hist *hist, EXPORT_SYMBOL_GPL(dccp_rx_hist_add_packet); -struct dccp_tx_hist *dccp_tx_hist_new(const char *name) -{ - struct dccp_tx_hist *hist = kmalloc(sizeof(*hist), GFP_ATOMIC); - static const char dccp_tx_hist_mask[] = "tx_hist_%s"; - char *slab_name; - - if (hist == NULL) - goto out; - - slab_name = kmalloc(strlen(name) + sizeof(dccp_tx_hist_mask) - 1, - GFP_ATOMIC); - if (slab_name == NULL) - goto out_free_hist; - - sprintf(slab_name, dccp_tx_hist_mask, name); - hist->dccptxh_slab = kmem_cache_create(slab_name, - sizeof(struct dccp_tx_hist_entry), - 0, SLAB_HWCACHE_ALIGN, - NULL, NULL); - if (hist->dccptxh_slab == NULL) - goto out_free_slab_name; -out: - return hist; -out_free_slab_name: - kfree(slab_name); -out_free_hist: - kfree(hist); - hist = NULL; - goto out; -} - -EXPORT_SYMBOL_GPL(dccp_tx_hist_new); - -void dccp_tx_hist_delete(struct dccp_tx_hist *hist) -{ - const char* name = kmem_cache_name(hist->dccptxh_slab); - - kmem_cache_destroy(hist->dccptxh_slab); - kfree(name); - kfree(hist); -} - -EXPORT_SYMBOL_GPL(dccp_tx_hist_delete); - -struct dccp_tx_hist_entry * - dccp_tx_hist_find_entry(const struct list_head *list, const u64 seq) -{ - struct dccp_tx_hist_entry *packet = NULL, *entry; - - list_for_each_entry(entry, list, dccphtx_node) - if (entry->dccphtx_seqno == seq) { - packet = entry; - break; - } - - return packet; -} - -EXPORT_SYMBOL_GPL(dccp_tx_hist_find_entry); - -int dccp_rx_hist_find_entry(const struct list_head *list, const u64 seq, - u8 *ccval) -{ - struct dccp_rx_hist_entry *packet = NULL, *entry; - - list_for_each_entry(entry, list, dccphrx_node) - if (entry->dccphrx_seqno == seq) { - packet = entry; - break; - } - - if (packet) - *ccval = packet->dccphrx_ccval; - - return packet != NULL; -} - -EXPORT_SYMBOL_GPL(dccp_rx_hist_find_entry); - -void dccp_tx_hist_purge_older(struct dccp_tx_hist *hist, - struct list_head *list, - struct dccp_tx_hist_entry *packet) +void dccp_rx_hist_purge(struct dccp_rx_hist *hist, struct list_head *list) { - struct dccp_tx_hist_entry *next; + struct dccp_rx_hist_entry *entry, *next; - list_for_each_entry_safe_continue(packet, next, list, dccphtx_node) { - list_del_init(&packet->dccphtx_node); - dccp_tx_hist_entry_delete(hist, packet); + list_for_each_entry_safe(entry, next, list, dccphrx_node) { + list_del_init(&entry->dccphrx_node); + kmem_cache_free(hist->dccprxh_slab, entry); } } -EXPORT_SYMBOL_GPL(dccp_tx_hist_purge_older); - -void dccp_tx_hist_purge(struct dccp_tx_hist *hist, struct list_head *list) -{ - struct dccp_tx_hist_entry *entry, *next; - - list_for_each_entry_safe(entry, next, list, dccphtx_node) { - list_del_init(&entry->dccphtx_node); - dccp_tx_hist_entry_delete(hist, entry); - } -} +EXPORT_SYMBOL_GPL(dccp_rx_hist_purge); -EXPORT_SYMBOL_GPL(dccp_tx_hist_purge); MODULE_AUTHOR("Ian McDonald <ian.mcdonald@jandi.co.nz>, " "Arnaldo Carvalho de Melo <acme@ghostprotocols.net>"); diff --git a/net/dccp/ccids/lib/packet_history.h b/net/dccp/ccids/lib/packet_history.h index 067cf1c85a37..1f960c19ea1b 100644 --- a/net/dccp/ccids/lib/packet_history.h +++ b/net/dccp/ccids/lib/packet_history.h @@ -49,43 +49,27 @@ #define TFRC_WIN_COUNT_PER_RTT 4 #define TFRC_WIN_COUNT_LIMIT 16 +/* + * Transmitter History data structures and declarations + */ struct dccp_tx_hist_entry { struct list_head dccphtx_node; u64 dccphtx_seqno:48, - dccphtx_ccval:4, dccphtx_sent:1; u32 dccphtx_rtt; struct timeval dccphtx_tstamp; }; -struct dccp_rx_hist_entry { - struct list_head dccphrx_node; - u64 dccphrx_seqno:48, - dccphrx_ccval:4, - dccphrx_type:4; - u32 dccphrx_ndp; /* In fact it is from 8 to 24 bits */ - struct timeval dccphrx_tstamp; -}; - struct dccp_tx_hist { - kmem_cache_t *dccptxh_slab; + struct kmem_cache *dccptxh_slab; }; extern struct dccp_tx_hist *dccp_tx_hist_new(const char *name); -extern void dccp_tx_hist_delete(struct dccp_tx_hist *hist); - -struct dccp_rx_hist { - kmem_cache_t *dccprxh_slab; -}; - -extern struct dccp_rx_hist *dccp_rx_hist_new(const char *name); -extern void dccp_rx_hist_delete(struct dccp_rx_hist *hist); -extern struct dccp_rx_hist_entry * - dccp_rx_hist_find_data_packet(const struct list_head *list); +extern void dccp_tx_hist_delete(struct dccp_tx_hist *hist); static inline struct dccp_tx_hist_entry * - dccp_tx_hist_entry_new(struct dccp_tx_hist *hist, - const gfp_t prio) + dccp_tx_hist_entry_new(struct dccp_tx_hist *hist, + const gfp_t prio) { struct dccp_tx_hist_entry *entry = kmem_cache_alloc(hist->dccptxh_slab, prio); @@ -96,18 +80,20 @@ static inline struct dccp_tx_hist_entry * return entry; } -static inline void dccp_tx_hist_entry_delete(struct dccp_tx_hist *hist, - struct dccp_tx_hist_entry *entry) +static inline struct dccp_tx_hist_entry * + dccp_tx_hist_head(struct list_head *list) { - if (entry != NULL) - kmem_cache_free(hist->dccptxh_slab, entry); + struct dccp_tx_hist_entry *head = NULL; + + if (!list_empty(list)) + head = list_entry(list->next, struct dccp_tx_hist_entry, + dccphtx_node); + return head; } extern struct dccp_tx_hist_entry * dccp_tx_hist_find_entry(const struct list_head *list, const u64 seq); -extern int dccp_rx_hist_find_entry(const struct list_head *list, const u64 seq, - u8 *ccval); static inline void dccp_tx_hist_add_entry(struct list_head *list, struct dccp_tx_hist_entry *entry) @@ -115,30 +101,45 @@ static inline void dccp_tx_hist_add_entry(struct list_head *list, list_add(&entry->dccphtx_node, list); } +static inline void dccp_tx_hist_entry_delete(struct dccp_tx_hist *hist, + struct dccp_tx_hist_entry *entry) +{ + if (entry != NULL) + kmem_cache_free(hist->dccptxh_slab, entry); +} + +extern void dccp_tx_hist_purge(struct dccp_tx_hist *hist, + struct list_head *list); + extern void dccp_tx_hist_purge_older(struct dccp_tx_hist *hist, struct list_head *list, struct dccp_tx_hist_entry *next); -extern void dccp_tx_hist_purge(struct dccp_tx_hist *hist, - struct list_head *list); +/* + * Receiver History data structures and declarations + */ +struct dccp_rx_hist_entry { + struct list_head dccphrx_node; + u64 dccphrx_seqno:48, + dccphrx_ccval:4, + dccphrx_type:4; + u32 dccphrx_ndp; /* In fact it is from 8 to 24 bits */ + struct timeval dccphrx_tstamp; +}; -static inline struct dccp_tx_hist_entry * - dccp_tx_hist_head(struct list_head *list) -{ - struct dccp_tx_hist_entry *head = NULL; +struct dccp_rx_hist { + struct kmem_cache *dccprxh_slab; +}; - if (!list_empty(list)) - head = list_entry(list->next, struct dccp_tx_hist_entry, - dccphtx_node); - return head; -} +extern struct dccp_rx_hist *dccp_rx_hist_new(const char *name); +extern void dccp_rx_hist_delete(struct dccp_rx_hist *hist); static inline struct dccp_rx_hist_entry * - dccp_rx_hist_entry_new(struct dccp_rx_hist *hist, - const struct sock *sk, - const u32 ndp, - const struct sk_buff *skb, - const gfp_t prio) + dccp_rx_hist_entry_new(struct dccp_rx_hist *hist, + const struct sock *sk, + const u32 ndp, + const struct sk_buff *skb, + const gfp_t prio) { struct dccp_rx_hist_entry *entry = kmem_cache_alloc(hist->dccprxh_slab, prio); @@ -156,18 +157,8 @@ static inline struct dccp_rx_hist_entry * return entry; } -static inline void dccp_rx_hist_entry_delete(struct dccp_rx_hist *hist, - struct dccp_rx_hist_entry *entry) -{ - if (entry != NULL) - kmem_cache_free(hist->dccprxh_slab, entry); -} - -extern void dccp_rx_hist_purge(struct dccp_rx_hist *hist, - struct list_head *list); - static inline struct dccp_rx_hist_entry * - dccp_rx_hist_head(struct list_head *list) + dccp_rx_hist_head(struct list_head *list) { struct dccp_rx_hist_entry *head = NULL; @@ -177,6 +168,27 @@ static inline struct dccp_rx_hist_entry * return head; } +extern int dccp_rx_hist_find_entry(const struct list_head *list, const u64 seq, + u8 *ccval); +extern struct dccp_rx_hist_entry * + dccp_rx_hist_find_data_packet(const struct list_head *list); + +extern void dccp_rx_hist_add_packet(struct dccp_rx_hist *hist, + struct list_head *rx_list, + struct list_head *li_list, + struct dccp_rx_hist_entry *packet, + u64 nonloss_seqno); + +static inline void dccp_rx_hist_entry_delete(struct dccp_rx_hist *hist, + struct dccp_rx_hist_entry *entry) +{ + if (entry != NULL) + kmem_cache_free(hist->dccprxh_slab, entry); +} + +extern void dccp_rx_hist_purge(struct dccp_rx_hist *hist, + struct list_head *list); + static inline int dccp_rx_hist_entry_data_packet(const struct dccp_rx_hist_entry *entry) { @@ -184,12 +196,6 @@ static inline int entry->dccphrx_type == DCCP_PKT_DATAACK; } -extern void dccp_rx_hist_add_packet(struct dccp_rx_hist *hist, - struct list_head *rx_list, - struct list_head *li_list, - struct dccp_rx_hist_entry *packet, - u64 nonloss_seqno); - extern u64 dccp_rx_hist_detect_loss(struct list_head *rx_list, struct list_head *li_list, u8 *win_loss); diff --git a/net/dccp/ccids/lib/tfrc.h b/net/dccp/ccids/lib/tfrc.h index 45f30f59ea2a..faf5f7e219e3 100644 --- a/net/dccp/ccids/lib/tfrc.h +++ b/net/dccp/ccids/lib/tfrc.h @@ -13,8 +13,29 @@ * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. */ - #include <linux/types.h> +#include <asm/div64.h> + +/* integer-arithmetic divisions of type (a * 1000000)/b */ +static inline u64 scaled_div(u64 a, u32 b) +{ + BUG_ON(b==0); + a *= 1000000; + do_div(a, b); + return a; +} + +static inline u32 scaled_div32(u64 a, u32 b) +{ + u64 result = scaled_div(a, b); + + if (result > UINT_MAX) { + DCCP_CRIT("Overflow: a(%llu)/b(%u) > ~0U", + (unsigned long long)a, b); + return UINT_MAX; + } + return result; +} extern u32 tfrc_calc_x(u16 s, u32 R, u32 p); extern u32 tfrc_calc_x_reverse_lookup(u32 fvalue); diff --git a/net/dccp/ccids/lib/tfrc_equation.c b/net/dccp/ccids/lib/tfrc_equation.c index 44076e0c6591..90009fd77e15 100644 --- a/net/dccp/ccids/lib/tfrc_equation.c +++ b/net/dccp/ccids/lib/tfrc_equation.c @@ -13,16 +13,83 @@ */ #include <linux/module.h> - -#include <asm/div64.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) -#define TFRC_CALC_X_SPLIT 50000 -/* equivalent to 0.05 */ - +/* + 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 }, @@ -526,117 +593,105 @@ static const u32 tfrc_calc_x_lookup[TFRC_CALC_X_ARRSIZE][2] = { { 243315981, 271305 } }; -/* Calculate the send rate as per section 3.1 of RFC3448 - -Returns send rate in bytes per second - -Integer maths and lookups are used as not allowed floating point in kernel - -The function for Xcalc as per section 3.1 of RFC3448 is: - -X = s - ------------------------------------------------------------- - R*sqrt(2*b*p/3) + (t_RTO * (3*sqrt(3*b*p/8) * p * (1+32*p^2))) - -where -X is the trasmit 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 acknowledgement - -we can assume that b = 1 and t_RTO is 4 * R. With this the equation becomes: - -X = s - ----------------------------------------------------------------------- - R * sqrt(2 * p / 3) + (12 * R * (sqrt(3 * p / 8) * p * (1 + 32 * p^2))) - - -which we can break down into: - -X = s - -------- - R * f(p) - -where f(p) = sqrt(2 * p / 3) + (12 * sqrt(3 * p / 8) * p * (1 + 32 * p * p)) - -Function parameters: -s - bytes -R - RTT in usecs -p - loss rate (decimal fraction multiplied by 1,000,000) - -Returns Xcalc in bytes per second - -DON'T alter this code unless you run test cases against it as the code -has been manipulated to stop underflow/overlow. +/* 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) { - int index; + u16 index; u32 f; - u64 tmp1, tmp2; + u64 result; - if (p < TFRC_CALC_X_SPLIT) - index = (p / (TFRC_CALC_X_SPLIT / TFRC_CALC_X_ARRSIZE)) - 1; - else - index = (p / (1000000 / TFRC_CALC_X_ARRSIZE)) - 1; + /* 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 (index < 0) - /* p should be 0 unless there is a bug in my code */ - index = 0; + 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; - if (R == 0) - R = 1; /* RTT can't be zero or else divide by zero */ + f = tfrc_calc_x_lookup[index][1]; - BUG_ON(index >= TFRC_CALC_X_ARRSIZE); + } else { /* 0.05 < p <= 1.00 */ + index = p/(1000000/TFRC_CALC_X_ARRSIZE) - 1; - if (p >= TFRC_CALC_X_SPLIT) f = tfrc_calc_x_lookup[index][0]; - else - f = tfrc_calc_x_lookup[index][1]; - - tmp1 = ((u64)s * 100000000); - tmp2 = ((u64)R * (u64)f); - do_div(tmp2, 10000); - do_div(tmp1, tmp2); - /* Don't alter above math unless you test due to overflow on 32 bit */ - - return (u32)tmp1; + } + + /* + * 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); } EXPORT_SYMBOL_GPL(tfrc_calc_x); /* - * args: fvalue - function value to match - * returns: p closest to that value + * tfrc_calc_x_reverse_lookup - try to find p given f(p) * - * both fvalue and p are multiplied by 1,000,000 to use ints + * @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 ctr = 0; - int small; + int index; - if (fvalue < tfrc_calc_x_lookup[0][1]) + if (fvalue == 0) /* f(p) = 0 whenever p = 0 */ return 0; - if (fvalue <= tfrc_calc_x_lookup[TFRC_CALC_X_ARRSIZE - 1][1]) - small = 1; - else if (fvalue > tfrc_calc_x_lookup[TFRC_CALC_X_ARRSIZE - 1][0]) + /* Error cases. */ + if (fvalue < tfrc_calc_x_lookup[0][1]) { + DCCP_WARN("fvalue %d smaller than resolution\n", fvalue); + return tfrc_calc_x_lookup[0][1]; + } + if (fvalue > tfrc_calc_x_lookup[TFRC_CALC_X_ARRSIZE - 1][0]) { + DCCP_WARN("fvalue %d exceeds bounds!\n", fvalue); return 1000000; - else - small = 0; - - while (fvalue > tfrc_calc_x_lookup[ctr][small]) - ctr++; + } - if (small) - return TFRC_CALC_X_SPLIT * ctr / TFRC_CALC_X_ARRSIZE; - else - return 1000000 * ctr / TFRC_CALC_X_ARRSIZE; + 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; } EXPORT_SYMBOL_GPL(tfrc_calc_x_reverse_lookup); |