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#ifndef _ACKVEC_H
#define _ACKVEC_H
* net/dccp/ackvec.h
* An implementation of Ack Vectors for the DCCP protocol
* Copyright (c) 2007 University of Aberdeen, Scotland, UK
* Copyright (c) 2005 Arnaldo Carvalho de Melo <>
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
#include <linux/dccp.h>
#include <linux/compiler.h>
#include <linux/list.h>
#include <linux/types.h>
* Ack Vector buffer space is static, in multiples of %DCCP_SINGLE_OPT_MAXLEN,
* the maximum size of a single Ack Vector. Setting %DCCPAV_NUM_ACKVECS to 1
* will be sufficient for most cases of low Ack Ratios, using a value of 2 gives
* more headroom if Ack Ratio is higher or when the sender acknowledges slowly.
* The maximum value is bounded by the u16 types for indices and functions.
/* Estimated minimum average Ack Vector length - used for updating MPS */
/* Threshold for coping with large bursts of losses */
enum dccp_ackvec_states {
static inline u8 dccp_ackvec_runlen(const u8 *cell)
return *cell & DCCPAV_MAX_RUNLEN;
static inline u8 dccp_ackvec_state(const u8 *cell)
return *cell & ~DCCPAV_MAX_RUNLEN;
* struct dccp_ackvec - Ack Vector main data structure
* This implements a fixed-size circular buffer within an array and is largely
* based on Appendix A of RFC 4340.
* @av_buf: circular buffer storage area
* @av_buf_head: head index; begin of live portion in @av_buf
* @av_buf_tail: tail index; first index _after_ the live portion in @av_buf
* @av_buf_ackno: highest seqno of acknowledgeable packet recorded in @av_buf
* @av_tail_ackno: lowest seqno of acknowledgeable packet recorded in @av_buf
* @av_buf_nonce: ECN nonce sums, each covering subsequent segments of up to
* %DCCP_SINGLE_OPT_MAXLEN cells in the live portion of @av_buf
* @av_overflow: if 1 then buf_head == buf_tail indicates buffer wraparound
* @av_records: list of %dccp_ackvec_record (Ack Vectors sent previously)
struct dccp_ackvec {
u16 av_buf_head;
u16 av_buf_tail;
u64 av_buf_ackno:48;
u64 av_tail_ackno:48;
bool av_buf_nonce[DCCPAV_NUM_ACKVECS];
u8 av_overflow:1;
struct list_head av_records;
* struct dccp_ackvec_record - Records information about sent Ack Vectors
* These list entries define the additional information which the HC-Receiver
* keeps about recently-sent Ack Vectors; again refer to RFC 4340, Appendix A.
* @avr_node: the list node in @av_records
* @avr_ack_seqno: sequence number of the packet the Ack Vector was sent on
* @avr_ack_ackno: the Ack number that this record/Ack Vector refers to
* @avr_ack_ptr: pointer into @av_buf where this record starts
* @avr_ack_runlen: run length of @avr_ack_ptr at the time of sending
* @avr_ack_nonce: the sum of @av_buf_nonce's at the time this record was sent
* The list as a whole is sorted in descending order by @avr_ack_seqno.
struct dccp_ackvec_record {
struct list_head avr_node;
u64 avr_ack_seqno:48;
u64 avr_ack_ackno:48;
u16 avr_ack_ptr;
u8 avr_ack_runlen;
u8 avr_ack_nonce:1;
int dccp_ackvec_init(void);
void dccp_ackvec_exit(void);
struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority);
void dccp_ackvec_free(struct dccp_ackvec *av);
void dccp_ackvec_input(struct dccp_ackvec *av, struct sk_buff *skb);
int dccp_ackvec_update_records(struct dccp_ackvec *av, u64 seq, u8 sum);
void dccp_ackvec_clear_state(struct dccp_ackvec *av, const u64 ackno);
u16 dccp_ackvec_buflen(const struct dccp_ackvec *av);
static inline bool dccp_ackvec_is_empty(const struct dccp_ackvec *av)
return av->av_overflow == 0 && av->av_buf_head == av->av_buf_tail;
* struct dccp_ackvec_parsed - Record offsets of Ack Vectors in skb
* @vec: start of vector (offset into skb)
* @len: length of @vec
* @nonce: whether @vec had an ECN nonce of 0 or 1
* @node: FIFO - arranged in descending order of ack_ackno
* This structure is used by CCIDs to access Ack Vectors in a received skb.
struct dccp_ackvec_parsed {
u8 *vec,
struct list_head node;
int dccp_ackvec_parsed_add(struct list_head *head, u8 *vec, u8 len, u8 nonce);
void dccp_ackvec_parsed_cleanup(struct list_head *parsed_chunks);
#endif /* _ACKVEC_H */