1 #ifndef _ACKVEC_H
2 #define _ACKVEC_H
3 /*
4  *  net/dccp/ackvec.h
5  *
6  *  An implementation of Ack Vectors for the DCCP protocol
7  *  Copyright (c) 2007 University of Aberdeen, Scotland, UK
8  *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@mandriva.com>
9  *	This program is free software; you can redistribute it and/or modify it
10  *	under the terms of the GNU General Public License version 2 as
11  *	published by the Free Software Foundation.
12  */
13 
14 #include <linux/dccp.h>
15 #include <linux/compiler.h>
16 #include <linux/list.h>
17 #include <linux/types.h>
18 
19 /*
20  * Ack Vector buffer space is static, in multiples of %DCCP_SINGLE_OPT_MAXLEN,
21  * the maximum size of a single Ack Vector. Setting %DCCPAV_NUM_ACKVECS to 1
22  * will be sufficient for most cases of low Ack Ratios, using a value of 2 gives
23  * more headroom if Ack Ratio is higher or when the sender acknowledges slowly.
24  * The maximum value is bounded by the u16 types for indices and functions.
25  */
26 #define DCCPAV_NUM_ACKVECS	2
27 #define DCCPAV_MAX_ACKVEC_LEN	(DCCP_SINGLE_OPT_MAXLEN * DCCPAV_NUM_ACKVECS)
28 
29 /* Estimated minimum average Ack Vector length - used for updating MPS */
30 #define DCCPAV_MIN_OPTLEN	16
31 
32 /* Threshold for coping with large bursts of losses */
33 #define DCCPAV_BURST_THRESH	(DCCPAV_MAX_ACKVEC_LEN / 8)
34 
35 enum dccp_ackvec_states {
36 	DCCPAV_RECEIVED =	0x00,
37 	DCCPAV_ECN_MARKED =	0x40,
38 	DCCPAV_RESERVED =	0x80,
39 	DCCPAV_NOT_RECEIVED =	0xC0
40 };
41 #define DCCPAV_MAX_RUNLEN	0x3F
42 
dccp_ackvec_runlen(const u8 * cell)43 static inline u8 dccp_ackvec_runlen(const u8 *cell)
44 {
45 	return *cell & DCCPAV_MAX_RUNLEN;
46 }
47 
dccp_ackvec_state(const u8 * cell)48 static inline u8 dccp_ackvec_state(const u8 *cell)
49 {
50 	return *cell & ~DCCPAV_MAX_RUNLEN;
51 }
52 
53 /** struct dccp_ackvec - Ack Vector main data structure
54  *
55  * This implements a fixed-size circular buffer within an array and is largely
56  * based on Appendix A of RFC 4340.
57  *
58  * @av_buf:	   circular buffer storage area
59  * @av_buf_head:   head index; begin of live portion in @av_buf
60  * @av_buf_tail:   tail index; first index _after_ the live portion in @av_buf
61  * @av_buf_ackno:  highest seqno of acknowledgeable packet recorded in @av_buf
62  * @av_tail_ackno: lowest  seqno of acknowledgeable packet recorded in @av_buf
63  * @av_buf_nonce:  ECN nonce sums, each covering subsequent segments of up to
64  *		   %DCCP_SINGLE_OPT_MAXLEN cells in the live portion of @av_buf
65  * @av_overflow:   if 1 then buf_head == buf_tail indicates buffer wraparound
66  * @av_records:	   list of %dccp_ackvec_record (Ack Vectors sent previously)
67  */
68 struct dccp_ackvec {
69 	u8			av_buf[DCCPAV_MAX_ACKVEC_LEN];
70 	u16			av_buf_head;
71 	u16			av_buf_tail;
72 	u64			av_buf_ackno:48;
73 	u64			av_tail_ackno:48;
74 	bool			av_buf_nonce[DCCPAV_NUM_ACKVECS];
75 	u8			av_overflow:1;
76 	struct list_head	av_records;
77 };
78 
79 /** struct dccp_ackvec_record - Records information about sent Ack Vectors
80  *
81  * These list entries define the additional information which the HC-Receiver
82  * keeps about recently-sent Ack Vectors; again refer to RFC 4340, Appendix A.
83  *
84  * @avr_node:	    the list node in @av_records
85  * @avr_ack_seqno:  sequence number of the packet the Ack Vector was sent on
86  * @avr_ack_ackno:  the Ack number that this record/Ack Vector refers to
87  * @avr_ack_ptr:    pointer into @av_buf where this record starts
88  * @avr_ack_runlen: run length of @avr_ack_ptr at the time of sending
89  * @avr_ack_nonce:  the sum of @av_buf_nonce's at the time this record was sent
90  *
91  * The list as a whole is sorted in descending order by @avr_ack_seqno.
92  */
93 struct dccp_ackvec_record {
94 	struct list_head avr_node;
95 	u64		 avr_ack_seqno:48;
96 	u64		 avr_ack_ackno:48;
97 	u16		 avr_ack_ptr;
98 	u8		 avr_ack_runlen;
99 	u8		 avr_ack_nonce:1;
100 };
101 
102 extern int dccp_ackvec_init(void);
103 extern void dccp_ackvec_exit(void);
104 
105 extern struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority);
106 extern void dccp_ackvec_free(struct dccp_ackvec *av);
107 
108 extern void dccp_ackvec_input(struct dccp_ackvec *av, struct sk_buff *skb);
109 extern int  dccp_ackvec_update_records(struct dccp_ackvec *av, u64 seq, u8 sum);
110 extern void dccp_ackvec_clear_state(struct dccp_ackvec *av, const u64 ackno);
111 extern u16  dccp_ackvec_buflen(const struct dccp_ackvec *av);
112 
dccp_ackvec_is_empty(const struct dccp_ackvec * av)113 static inline bool dccp_ackvec_is_empty(const struct dccp_ackvec *av)
114 {
115 	return av->av_overflow == 0 && av->av_buf_head == av->av_buf_tail;
116 }
117 
118 /**
119  * struct dccp_ackvec_parsed  -  Record offsets of Ack Vectors in skb
120  * @vec:	start of vector (offset into skb)
121  * @len:	length of @vec
122  * @nonce:	whether @vec had an ECN nonce of 0 or 1
123  * @node:	FIFO - arranged in descending order of ack_ackno
124  * This structure is used by CCIDs to access Ack Vectors in a received skb.
125  */
126 struct dccp_ackvec_parsed {
127 	u8		 *vec,
128 			 len,
129 			 nonce:1;
130 	struct list_head node;
131 };
132 
133 extern int dccp_ackvec_parsed_add(struct list_head *head,
134 				  u8 *vec, u8 len, u8 nonce);
135 extern void dccp_ackvec_parsed_cleanup(struct list_head *parsed_chunks);
136 #endif /* _ACKVEC_H */
137