net/dccp/ackvec.h

0001 /* SPDX-License-Identifier: GPL-2.0-only */
0002 #ifndef _ACKVEC_H
0003 #define _ACKVEC_H
0004 /*
0005  *  net/dccp/ackvec.h
0006  *
0007  *  An implementation of Ack Vectors for the DCCP protocol
0008  *  Copyright (c) 2007 University of Aberdeen, Scotland, UK
0009  *  Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@mandriva.com>
0010  */
0011
0012 #include <linux/dccp.h>
0013 #include <linux/compiler.h>
0014 #include <linux/list.h>
0015 #include <linux/types.h>
0016
0017 /*
0018  * Ack Vector buffer space is static, in multiples of %DCCP_SINGLE_OPT_MAXLEN,
0019  * the maximum size of a single Ack Vector. Setting %DCCPAV_NUM_ACKVECS to 1
0020  * will be sufficient for most cases of low Ack Ratios, using a value of 2 gives
0021  * more headroom if Ack Ratio is higher or when the sender acknowledges slowly.
0022  * The maximum value is bounded by the u16 types for indices and functions.
0023  */
0024 #define DCCPAV_NUM_ACKVECS  2
0025 #define DCCPAV_MAX_ACKVEC_LEN   (DCCP_SINGLE_OPT_MAXLEN * DCCPAV_NUM_ACKVECS)
0026
0027 /* Estimated minimum average Ack Vector length - used for updating MPS */
0028 #define DCCPAV_MIN_OPTLEN   16
0029
0030 /* Threshold for coping with large bursts of losses */
0031 #define DCCPAV_BURST_THRESH (DCCPAV_MAX_ACKVEC_LEN / 8)
0032
0033 enum dccp_ackvec_states {
0034     DCCPAV_RECEIVED =   0x00,
0035     DCCPAV_ECN_MARKED = 0x40,
0036     DCCPAV_RESERVED =   0x80,
0037     DCCPAV_NOT_RECEIVED =   0xC0
0038 };
0039 #define DCCPAV_MAX_RUNLEN   0x3F
0040
0041 static inline u8 dccp_ackvec_runlen(const u8 *cell)
0042 {
0043     return *cell & DCCPAV_MAX_RUNLEN;
0044 }
0045
0046 static inline u8 dccp_ackvec_state(const u8 *cell)
0047 {
0048     return *cell & ~DCCPAV_MAX_RUNLEN;
0049 }
0050
0051 /**
0052  * struct dccp_ackvec - Ack Vector main data structure
0053  *
0054  * This implements a fixed-size circular buffer within an array and is largely
0055  * based on Appendix A of RFC 4340.
0056  *
0057  * @av_buf:    circular buffer storage area
0058  * @av_buf_head:   head index; begin of live portion in @av_buf
0059  * @av_buf_tail:   tail index; first index _after_ the live portion in @av_buf
0060  * @av_buf_ackno:  highest seqno of acknowledgeable packet recorded in @av_buf
0061  * @av_tail_ackno: lowest  seqno of acknowledgeable packet recorded in @av_buf
0062  * @av_buf_nonce:  ECN nonce sums, each covering subsequent segments of up to
0063  *         %DCCP_SINGLE_OPT_MAXLEN cells in the live portion of @av_buf
0064  * @av_overflow:   if 1 then buf_head == buf_tail indicates buffer wraparound
0065  * @av_records:    list of %dccp_ackvec_record (Ack Vectors sent previously)
0066  */
0067 struct dccp_ackvec {
0068     u8          av_buf[DCCPAV_MAX_ACKVEC_LEN];
0069     u16         av_buf_head;
0070     u16         av_buf_tail;
0071     u64         av_buf_ackno:48;
0072     u64         av_tail_ackno:48;
0073     bool            av_buf_nonce[DCCPAV_NUM_ACKVECS];
0074     u8          av_overflow:1;
0075     struct list_head    av_records;
0076 };
0077
0078 /**
0079  * struct dccp_ackvec_record - Records information about sent Ack Vectors
0080  *
0081  * These list entries define the additional information which the HC-Receiver
0082  * keeps about recently-sent Ack Vectors; again refer to RFC 4340, Appendix A.
0083  *
0084  * @avr_node:       the list node in @av_records
0085  * @avr_ack_seqno:  sequence number of the packet the Ack Vector was sent on
0086  * @avr_ack_ackno:  the Ack number that this record/Ack Vector refers to
0087  * @avr_ack_ptr:    pointer into @av_buf where this record starts
0088  * @avr_ack_runlen: run length of @avr_ack_ptr at the time of sending
0089  * @avr_ack_nonce:  the sum of @av_buf_nonce's at the time this record was sent
0090  *
0091  * The list as a whole is sorted in descending order by @avr_ack_seqno.
0092  */
0093 struct dccp_ackvec_record {
0094     struct list_head avr_node;
0095     u64      avr_ack_seqno:48;
0096     u64      avr_ack_ackno:48;
0097     u16      avr_ack_ptr;
0098     u8       avr_ack_runlen;
0099     u8       avr_ack_nonce:1;
0100 };
0101
0102 int dccp_ackvec_init(void);
0103 void dccp_ackvec_exit(void);
0104
0105 struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority);
0106 void dccp_ackvec_free(struct dccp_ackvec *av);
0107
0108 void dccp_ackvec_input(struct dccp_ackvec *av, struct sk_buff *skb);
0109 int dccp_ackvec_update_records(struct dccp_ackvec *av, u64 seq, u8 sum);
0110 void dccp_ackvec_clear_state(struct dccp_ackvec *av, const u64 ackno);
0111 u16 dccp_ackvec_buflen(const struct dccp_ackvec *av);
0112
0113 static inline bool dccp_ackvec_is_empty(const struct dccp_ackvec *av)
0114 {
0115     return av->av_overflow == 0 && av->av_buf_head == av->av_buf_tail;
0116 }
0117
0118 /**
0119  * struct dccp_ackvec_parsed  -  Record offsets of Ack Vectors in skb
0120  * @vec:    start of vector (offset into skb)
0121  * @len:    length of @vec
0122  * @nonce:  whether @vec had an ECN nonce of 0 or 1
0123  * @node:   FIFO - arranged in descending order of ack_ackno
0124  *
0125  * This structure is used by CCIDs to access Ack Vectors in a received skb.
0126  */
0127 struct dccp_ackvec_parsed {
0128     u8       *vec,
0129              len,
0130              nonce:1;
0131     struct list_head node;
0132 };
0133
0134 int dccp_ackvec_parsed_add(struct list_head *head, u8 *vec, u8 len, u8 nonce);
0135 void dccp_ackvec_parsed_cleanup(struct list_head *parsed_chunks);
0136 #endif /* _ACKVEC_H */