2 * net/dccp/ccids/lib/loss_interval.c
4 * Copyright (c) 2007 The University of Aberdeen, Scotland, UK
5 * Copyright (c) 2005-7 The University of Waikato, Hamilton, New Zealand.
6 * Copyright (c) 2005-7 Ian McDonald <ian.mcdonald@jandi.co.nz>
7 * Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License as published by
11 * the Free Software Foundation; either version 2 of the License, or
12 * (at your option) any later version.
17 static struct kmem_cache
*tfrc_lh_slab __read_mostly
;
18 /* Loss Interval weights from [RFC 3448, 5.4], scaled by 10 */
19 static const int tfrc_lh_weights
[NINTERVAL
] = { 10, 10, 10, 10, 8, 6, 4, 2 };
21 /* implements LIFO semantics on the array */
22 static inline u8
LIH_INDEX(const u8 ctr
)
24 return (LIH_SIZE
- 1 - (ctr
% LIH_SIZE
));
27 /* the `counter' index always points at the next entry to be populated */
28 static inline struct tfrc_loss_interval
*tfrc_lh_peek(struct tfrc_loss_hist
*lh
)
30 return lh
->counter
? lh
->ring
[LIH_INDEX(lh
->counter
- 1)] : NULL
;
33 /* given i with 0 <= i <= k, return I_i as per the rfc3448bis notation */
34 static inline u32
tfrc_lh_get_interval(struct tfrc_loss_hist
*lh
, const u8 i
)
36 BUG_ON(i
>= lh
->counter
);
37 return lh
->ring
[LIH_INDEX(lh
->counter
- i
- 1)]->li_length
;
41 * On-demand allocation and de-allocation of entries
43 static struct tfrc_loss_interval
*tfrc_lh_demand_next(struct tfrc_loss_hist
*lh
)
45 if (lh
->ring
[LIH_INDEX(lh
->counter
)] == NULL
)
46 lh
->ring
[LIH_INDEX(lh
->counter
)] = kmem_cache_alloc(tfrc_lh_slab
,
48 return lh
->ring
[LIH_INDEX(lh
->counter
)];
51 void tfrc_lh_cleanup(struct tfrc_loss_hist
*lh
)
53 if (!tfrc_lh_is_initialised(lh
))
56 for (lh
->counter
= 0; lh
->counter
< LIH_SIZE
; lh
->counter
++)
57 if (lh
->ring
[LIH_INDEX(lh
->counter
)] != NULL
) {
58 kmem_cache_free(tfrc_lh_slab
,
59 lh
->ring
[LIH_INDEX(lh
->counter
)]);
60 lh
->ring
[LIH_INDEX(lh
->counter
)] = NULL
;
63 EXPORT_SYMBOL_GPL(tfrc_lh_cleanup
);
65 static void tfrc_lh_calc_i_mean(struct tfrc_loss_hist
*lh
)
67 u32 i_i
, i_tot0
= 0, i_tot1
= 0, w_tot
= 0;
68 int i
, k
= tfrc_lh_length(lh
) - 1; /* k is as in rfc3448bis, 5.4 */
73 for (i
= 0; i
<= k
; i
++) {
74 i_i
= tfrc_lh_get_interval(lh
, i
);
77 i_tot0
+= i_i
* tfrc_lh_weights
[i
];
78 w_tot
+= tfrc_lh_weights
[i
];
81 i_tot1
+= i_i
* tfrc_lh_weights
[i
-1];
84 lh
->i_mean
= max(i_tot0
, i_tot1
) / w_tot
;
88 * tfrc_lh_update_i_mean - Update the `open' loss interval I_0
89 * This updates I_mean as the sequence numbers increase. As a consequence, the
90 * open loss interval I_0 increases, hence p = W_tot/max(I_tot0, I_tot1)
91 * decreases, and thus there is no need to send renewed feedback.
93 void tfrc_lh_update_i_mean(struct tfrc_loss_hist
*lh
, struct sk_buff
*skb
)
95 struct tfrc_loss_interval
*cur
= tfrc_lh_peek(lh
);
98 if (cur
== NULL
) /* not initialised */
101 /* FIXME: should probably also count non-data packets (RFC 4342, 6.1) */
102 if (!dccp_data_packet(skb
))
105 len
= dccp_delta_seqno(cur
->li_seqno
, DCCP_SKB_CB(skb
)->dccpd_seq
) + 1;
107 if (len
- (s64
)cur
->li_length
<= 0) /* duplicate or reordered */
110 if (SUB16(dccp_hdr(skb
)->dccph_ccval
, cur
->li_ccval
) > 4)
112 * Implements RFC 4342, 10.2:
113 * If a packet S (skb) exists whose seqno comes `after' the one
114 * starting the current loss interval (cur) and if the modulo-16
115 * distance from C(cur) to C(S) is greater than 4, consider all
116 * subsequent packets as belonging to a new loss interval. This
117 * test is necessary since CCVal may wrap between intervals.
119 cur
->li_is_closed
= 1;
121 if (tfrc_lh_length(lh
) == 1) /* due to RFC 3448, 6.3.1 */
124 cur
->li_length
= len
;
125 tfrc_lh_calc_i_mean(lh
);
128 /* Determine if `new_loss' does begin a new loss interval [RFC 4342, 10.2] */
129 static inline u8
tfrc_lh_is_new_loss(struct tfrc_loss_interval
*cur
,
130 struct tfrc_rx_hist_entry
*new_loss
)
132 return dccp_delta_seqno(cur
->li_seqno
, new_loss
->tfrchrx_seqno
) > 0 &&
133 (cur
->li_is_closed
|| SUB16(new_loss
->tfrchrx_ccval
, cur
->li_ccval
) > 4);
136 /** tfrc_lh_interval_add - Insert new record into the Loss Interval database
137 * @lh: Loss Interval database
138 * @rh: Receive history containing a fresh loss event
139 * @calc_first_li: Caller-dependent routine to compute length of first interval
140 * @sk: Used by @calc_first_li in caller-specific way (subtyping)
141 * Updates I_mean and returns 1 if a new interval has in fact been added to @lh.
143 int tfrc_lh_interval_add(struct tfrc_loss_hist
*lh
, struct tfrc_rx_hist
*rh
,
144 u32 (*calc_first_li
)(struct sock
*), struct sock
*sk
)
146 struct tfrc_loss_interval
*cur
= tfrc_lh_peek(lh
), *new;
148 if (cur
!= NULL
&& !tfrc_lh_is_new_loss(cur
, tfrc_rx_hist_loss_prev(rh
)))
151 new = tfrc_lh_demand_next(lh
);
152 if (unlikely(new == NULL
)) {
153 DCCP_CRIT("Cannot allocate/add loss record.");
157 new->li_seqno
= tfrc_rx_hist_loss_prev(rh
)->tfrchrx_seqno
;
158 new->li_ccval
= tfrc_rx_hist_loss_prev(rh
)->tfrchrx_ccval
;
159 new->li_is_closed
= 0;
161 if (++lh
->counter
== 1)
162 lh
->i_mean
= new->li_length
= (*calc_first_li
)(sk
);
164 cur
->li_length
= dccp_delta_seqno(cur
->li_seqno
, new->li_seqno
);
165 new->li_length
= dccp_delta_seqno(new->li_seqno
,
166 tfrc_rx_hist_last_rcv(rh
)->tfrchrx_seqno
) + 1;
167 if (lh
->counter
> (2*LIH_SIZE
))
168 lh
->counter
-= LIH_SIZE
;
170 tfrc_lh_calc_i_mean(lh
);
174 EXPORT_SYMBOL_GPL(tfrc_lh_interval_add
);
176 int __init
tfrc_li_init(void)
178 tfrc_lh_slab
= kmem_cache_create("tfrc_li_hist",
179 sizeof(struct tfrc_loss_interval
), 0,
180 SLAB_HWCACHE_ALIGN
, NULL
);
181 return tfrc_lh_slab
== NULL
? -ENOBUFS
: 0;
184 void tfrc_li_exit(void)
186 if (tfrc_lh_slab
!= NULL
) {
187 kmem_cache_destroy(tfrc_lh_slab
);