b3d14bff12
This completes the implementation of a circular buffer for Ack Vectors, by
extending the current (linear array-based) implementation. The changes are:
(a) An `overflow' flag to deal with the case of overflow. As before, dynamic
growth of the buffer will not be supported; but code will be added to deal
robustly with overflowing Ack Vector buffers.
(b) A `tail_seqno' field. When naively implementing the algorithm of Appendix A
in RFC 4340, problems arise whenever subsequent Ack Vector records overlap,
which can bring the entire run length calculation completely out of synch.
(This is documented on http://www.erg.abdn.ac.uk/users/gerrit/dccp/notes/\
ack_vectors/tracking_tail_ackno/ .)
(c) The buffer length is now computed dynamically (i.e. current fill level),
as the span between head to tail.
As a result, dccp_ackvec_pending() is now simpler - the #ifdef is no longer
necessary since buf_empty is always true when IP_DCCP_ACKVEC is not configured.
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
127 lines
4.4 KiB
C
127 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 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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