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This provides a routine to consistently update the buffer state when the peer acknowledges receipt of Ack Vectors; updating state in the list of Ack Vectors as well as in the circular buffer. While based on RFC 4340, several additional (and necessary) precautions were added to protect the consistency of the buffer state. These additions are essential, since analysis and experience showed that the basic algorithm was insufficient for this task (which lead to problems that were hard to debug). The algorithm now * deals with HC-sender acknowledging to HC-receiver and vice versa, * keeps track of the last unacknowledged but received seqno in tail_ackno, * has special cases to reset the overflow condition when appropriate, * is protected against receiving older information (would mess up buffer state). Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
128 lines
4.4 KiB
C
128 lines
4.4 KiB
C
#ifndef _ACKVEC_H
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#define _ACKVEC_H
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/*
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* net/dccp/ackvec.h
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*
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* An implementation of Ack Vectors for the DCCP protocol
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* Copyright (c) 2007 University of Aberdeen, Scotland, UK
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* Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@mandriva.com>
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/dccp.h>
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#include <linux/compiler.h>
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#include <linux/list.h>
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#include <linux/types.h>
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/*
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* Ack Vector buffer space is static, in multiples of %DCCP_SINGLE_OPT_MAXLEN,
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* the maximum size of a single Ack Vector. Setting %DCCPAV_NUM_ACKVECS to 1
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* will be sufficient for most cases of low Ack Ratios, using a value of 2 gives
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* more headroom if Ack Ratio is higher or when the sender acknowledges slowly.
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* The maximum value is bounded by the u16 types for indices and functions.
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*/
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#define DCCPAV_NUM_ACKVECS 2
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#define DCCPAV_MAX_ACKVEC_LEN (DCCP_SINGLE_OPT_MAXLEN * DCCPAV_NUM_ACKVECS)
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/* Estimated minimum average Ack Vector length - used for updating MPS */
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#define DCCPAV_MIN_OPTLEN 16
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enum dccp_ackvec_states {
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DCCPAV_RECEIVED = 0x00,
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DCCPAV_ECN_MARKED = 0x40,
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DCCPAV_RESERVED = 0x80,
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DCCPAV_NOT_RECEIVED = 0xC0
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};
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#define DCCPAV_MAX_RUNLEN 0x3F
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static inline u8 dccp_ackvec_runlen(const u8 *cell)
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{
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return *cell & DCCPAV_MAX_RUNLEN;
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}
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static inline u8 dccp_ackvec_state(const u8 *cell)
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{
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return *cell & ~DCCPAV_MAX_RUNLEN;
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}
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/** struct dccp_ackvec - Ack Vector main data structure
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*
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* This implements a fixed-size circular buffer within an array and is largely
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* based on Appendix A of RFC 4340.
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*
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* @av_buf: circular buffer storage area
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* @av_buf_head: head index; begin of live portion in @av_buf
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* @av_buf_tail: tail index; first index _after_ the live portion in @av_buf
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* @av_buf_ackno: highest seqno of acknowledgeable packet recorded in @av_buf
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* @av_tail_ackno: lowest seqno of acknowledgeable packet recorded in @av_buf
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* @av_buf_nonce: ECN nonce sums, each covering subsequent segments of up to
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* %DCCP_SINGLE_OPT_MAXLEN cells in the live portion of @av_buf
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* @av_overflow: if 1 then buf_head == buf_tail indicates buffer wraparound
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* @av_records: list of %dccp_ackvec_record (Ack Vectors sent previously)
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* @av_veclen: length of the live portion of @av_buf
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*/
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struct dccp_ackvec {
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u8 av_buf[DCCPAV_MAX_ACKVEC_LEN];
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u16 av_buf_head;
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u16 av_buf_tail;
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u64 av_buf_ackno:48;
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u64 av_tail_ackno:48;
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bool av_buf_nonce[DCCPAV_NUM_ACKVECS];
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u8 av_overflow:1;
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struct list_head av_records;
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u16 av_vec_len;
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};
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/** struct dccp_ackvec_record - Records information about sent Ack Vectors
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*
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* These list entries define the additional information which the HC-Receiver
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* keeps about recently-sent Ack Vectors; again refer to RFC 4340, Appendix A.
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*
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* @avr_node: the list node in @av_records
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* @avr_ack_seqno: sequence number of the packet the Ack Vector was sent on
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* @avr_ack_ackno: the Ack number that this record/Ack Vector refers to
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* @avr_ack_ptr: pointer into @av_buf where this record starts
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* @avr_ack_runlen: run length of @avr_ack_ptr at the time of sending
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* @avr_ack_nonce: the sum of @av_buf_nonce's at the time this record was sent
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*
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* The list as a whole is sorted in descending order by @avr_ack_seqno.
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*/
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struct dccp_ackvec_record {
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struct list_head avr_node;
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u64 avr_ack_seqno:48;
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u64 avr_ack_ackno:48;
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u16 avr_ack_ptr;
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u8 avr_ack_runlen;
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u8 avr_ack_nonce:1;
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};
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struct sock;
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struct sk_buff;
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extern int dccp_ackvec_init(void);
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extern void dccp_ackvec_exit(void);
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extern struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority);
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extern void dccp_ackvec_free(struct dccp_ackvec *av);
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extern int dccp_ackvec_add(struct dccp_ackvec *av, const struct sock *sk,
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const u64 ackno, const u8 state);
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extern void dccp_ackvec_check_rcv_ackno(struct dccp_ackvec *av,
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struct sock *sk, const u64 ackno);
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extern int dccp_ackvec_parse(struct sock *sk, const struct sk_buff *skb,
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u64 *ackno, const u8 opt,
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const u8 *value, const u8 len);
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extern int dccp_ackvec_update_records(struct dccp_ackvec *av, u64 seq, u8 sum);
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extern void dccp_ackvec_clear_state(struct dccp_ackvec *av, const u64 ackno);
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extern u16 dccp_ackvec_buflen(const struct dccp_ackvec *av);
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static inline bool dccp_ackvec_is_empty(const struct dccp_ackvec *av)
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{
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return av->av_overflow == 0 && av->av_buf_head == av->av_buf_tail;
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}
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#endif /* _ACKVEC_H */
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