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
41 static inline u8 dccp_ackvec_runlen(const u8 *cell)
42 {
43 return *cell & DCCPAV_MAX_RUNLEN;
44 }
45
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
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 */