packet_history.h revision 8995a238ef6869bc5c80240440bc58452c7af283 
1/*
2 *  Packet RX/TX history data structures and routines for TFRC-based protocols.
3 *
4 *  Copyright (c) 2007   The University of Aberdeen, Scotland, UK
5 *  Copyright (c) 2005-6 The University of Waikato, Hamilton, New Zealand.
6 *
7 *  This code has been developed by the University of Waikato WAND
8 *  research group. For further information please see http://www.wand.net.nz/
9 *  or e-mail Ian McDonald - ian.mcdonald@jandi.co.nz
10 *
11 *  This code also uses code from Lulea University, rereleased as GPL by its
12 *  authors:
13 *  Copyright (c) 2003 Nils-Erik Mattsson, Joacim Haggmark, Magnus Erixzon
14 *
15 *  Changes to meet Linux coding standards, to make it meet latest ccid3 draft
16 *  and to make it work as a loadable module in the DCCP stack written by
17 *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>.
18 *
19 *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
20 *
21 *  This program is free software; you can redistribute it and/or modify
22 *  it under the terms of the GNU General Public License as published by
23 *  the Free Software Foundation; either version 2 of the License, or
24 *  (at your option) any later version.
25 *
26 *  This program is distributed in the hope that it will be useful,
27 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
28 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
29 *  GNU General Public License for more details.
30 *
31 *  You should have received a copy of the GNU General Public License
32 *  along with this program; if not, write to the Free Software
33 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
34 */
35
36#ifndef _DCCP_PKT_HIST_
37#define _DCCP_PKT_HIST_
38
39#include <linux/ktime.h>
40#include <linux/types.h>
41
42struct sk_buff;
43
44struct tfrc_tx_hist_entry;
45
46extern int  tfrc_tx_hist_add(struct tfrc_tx_hist_entry **headp, u64 seqno);
47extern void tfrc_tx_hist_purge(struct tfrc_tx_hist_entry **headp);
48extern u32  tfrc_tx_hist_rtt(struct tfrc_tx_hist_entry *head,
49			     const u64 seqno, const ktime_t now);
50
51/* Subtraction a-b modulo-16, respects circular wrap-around */
52#define SUB16(a, b) (((a) + 16 - (b)) & 0xF)
53
54/* Number of packets to wait after a missing packet (RFC 4342, 6.1) */
55#define TFRC_NDUPACK 3
56
57/**
58 * tfrc_rx_hist_entry - Store information about a single received packet
59 * @tfrchrx_seqno:	DCCP packet sequence number
60 * @tfrchrx_ccval:	window counter value of packet (RFC 4342, 8.1)
61 * @tfrchrx_ndp:	the NDP count (if any) of the packet
62 * @tfrchrx_tstamp:	actual receive time of packet
63 */
64struct tfrc_rx_hist_entry {
65	u64		 tfrchrx_seqno:48,
66			 tfrchrx_ccval:4,
67			 tfrchrx_type:4;
68	u32		 tfrchrx_ndp; /* In fact it is from 8 to 24 bits */
69	ktime_t		 tfrchrx_tstamp;
70};
71
72/**
73 * tfrc_rx_hist  -  RX history structure for TFRC-based protocols
74 *
75 * @ring:		Packet history for RTT sampling and loss detection
76 * @loss_count:		Number of entries in circular history
77 * @loss_start:		Movable index (for loss detection)
78 * @rtt_sample_prev:	Used during RTT sampling, points to candidate entry
79 */
80struct tfrc_rx_hist {
81	struct tfrc_rx_hist_entry *ring[TFRC_NDUPACK + 1];
82	u8			  loss_count:2,
83				  loss_start:2;
84#define rtt_sample_prev		  loss_start
85};
86
87/**
88 * tfrc_rx_hist_index - index to reach n-th entry after loss_start
89 */
90static inline u8 tfrc_rx_hist_index(const struct tfrc_rx_hist *h, const u8 n)
91{
92	return (h->loss_start + n) & TFRC_NDUPACK;
93}
94
95/**
96 * tfrc_rx_hist_last_rcv - entry with highest-received-seqno so far
97 */
98static inline struct tfrc_rx_hist_entry *
99			tfrc_rx_hist_last_rcv(const struct tfrc_rx_hist *h)
100{
101	return h->ring[tfrc_rx_hist_index(h, h->loss_count)];
102}
103
104/**
105 * tfrc_rx_hist_entry - return the n-th history entry after loss_start
106 */
107static inline struct tfrc_rx_hist_entry *
108			tfrc_rx_hist_entry(const struct tfrc_rx_hist *h, const u8 n)
109{
110	return h->ring[tfrc_rx_hist_index(h, n)];
111}
112
113/**
114 * tfrc_rx_hist_loss_prev - entry with highest-received-seqno before loss was detected
115 */
116static inline struct tfrc_rx_hist_entry *
117			tfrc_rx_hist_loss_prev(const struct tfrc_rx_hist *h)
118{
119	return h->ring[h->loss_start];
120}
121
122extern void tfrc_rx_hist_add_packet(struct tfrc_rx_hist *h,
123				    const struct sk_buff *skb, const u32 ndp);
124
125extern int tfrc_rx_hist_duplicate(struct tfrc_rx_hist *h, struct sk_buff *skb);
126extern int tfrc_rx_hist_new_loss_indicated(struct tfrc_rx_hist *h,
127					   const struct sk_buff *skb, u32 ndp);
128extern u32 tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h,
129				   const struct sk_buff *skb);
130extern int tfrc_rx_hist_alloc(struct tfrc_rx_hist *h);
131extern void tfrc_rx_hist_purge(struct tfrc_rx_hist *h);
132
133#endif /* _DCCP_PKT_HIST_ */
134