1 /* SPDX-License-Identifier: GPL-2.0-only */
2 #ifndef _ACKVEC_H
3 #define _ACKVEC_H
4 /*
5  *  net/dccp/ackvec.h
6  *
7  *  An implementation of Ack Vectors for the DCCP protocol
8  *  Copyright (c) 2007 University of Aberdeen, Scotland, UK
9  *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@mandriva.com>
10  */
11 
12 #include <linux/dccp.h>
13 #include <linux/compiler.h>
14 #include <linux/list.h>
15 #include <linux/types.h>
16 
17 /*
18  * Ack Vector buffer space is static, in multiples of %DCCP_SINGLE_OPT_MAXLEN,
19  * the maximum size of a single Ack Vector. Setting %DCCPAV_NUM_ACKVECS to 1
20  * will be sufficient for most cases of low Ack Ratios, using a value of 2 gives
21  * more headroom if Ack Ratio is higher or when the sender acknowledges slowly.
22  * The maximum value is bounded by the u16 types for indices and functions.
23  */
24 #define DCCPAV_NUM_ACKVECS	2
25 #define DCCPAV_MAX_ACKVEC_LEN	(DCCP_SINGLE_OPT_MAXLEN * DCCPAV_NUM_ACKVECS)
26 
27 /* Estimated minimum average Ack Vector length - used for updating MPS */
28 #define DCCPAV_MIN_OPTLEN	16
29 
30 /* Threshold for coping with large bursts of losses */
31 #define DCCPAV_BURST_THRESH	(DCCPAV_MAX_ACKVEC_LEN / 8)
32 
33 enum dccp_ackvec_states {
34 	DCCPAV_RECEIVED =	0x00,
35 	DCCPAV_ECN_MARKED =	0x40,
36 	DCCPAV_RESERVED =	0x80,
37 	DCCPAV_NOT_RECEIVED =	0xC0
38 };
39 #define DCCPAV_MAX_RUNLEN	0x3F
40 
dccp_ackvec_runlen(const u8 * cell)41 static inline u8 dccp_ackvec_runlen(const u8 *cell)
42 {
43 	return *cell & DCCPAV_MAX_RUNLEN;
44 }
45 
dccp_ackvec_state(const u8 * cell)46 static inline u8 dccp_ackvec_state(const u8 *cell)
47 {
48 	return *cell & ~DCCPAV_MAX_RUNLEN;
49 }
50 
51 /**
52  * struct dccp_ackvec - Ack Vector main data structure
53  *
54  * This implements a fixed-size circular buffer within an array and is largely
55  * based on Appendix A of RFC 4340.
56  *
57  * @av_buf:	   circular buffer storage area
58  * @av_buf_head:   head index; begin of live portion in @av_buf
59  * @av_buf_tail:   tail index; first index _after_ the live portion in @av_buf
60  * @av_buf_ackno:  highest seqno of acknowledgeable packet recorded in @av_buf
61  * @av_tail_ackno: lowest  seqno of acknowledgeable packet recorded in @av_buf
62  * @av_buf_nonce:  ECN nonce sums, each covering subsequent segments of up to
63  *		   %DCCP_SINGLE_OPT_MAXLEN cells in the live portion of @av_buf
64  * @av_overflow:   if 1 then buf_head == buf_tail indicates buffer wraparound
65  * @av_records:	   list of %dccp_ackvec_record (Ack Vectors sent previously)
66  */
67 struct dccp_ackvec {
68 	u8			av_buf[DCCPAV_MAX_ACKVEC_LEN];
69 	u16			av_buf_head;
70 	u16			av_buf_tail;
71 	u64			av_buf_ackno:48;
72 	u64			av_tail_ackno:48;
73 	bool			av_buf_nonce[DCCPAV_NUM_ACKVECS];
74 	u8			av_overflow:1;
75 	struct list_head	av_records;
76 };
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 int dccp_ackvec_init(void);
103 void dccp_ackvec_exit(void);
104 
105 struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority);
106 void dccp_ackvec_free(struct dccp_ackvec *av);
107 
108 void dccp_ackvec_input(struct dccp_ackvec *av, struct sk_buff *skb);
109 int dccp_ackvec_update_records(struct dccp_ackvec *av, u64 seq, u8 sum);
110 void dccp_ackvec_clear_state(struct dccp_ackvec *av, const u64 ackno);
111 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  *
125  * This structure is used by CCIDs to access Ack Vectors in a received skb.
126  */
127 struct dccp_ackvec_parsed {
128 	u8		 *vec,
129 			 len,
130 			 nonce:1;
131 	struct list_head node;
132 };
133 
134 int dccp_ackvec_parsed_add(struct list_head *head, u8 *vec, u8 len, u8 nonce);
135 void dccp_ackvec_parsed_cleanup(struct list_head *parsed_chunks);
136 #endif /* _ACKVEC_H */
137