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The Maximum Packet Size (MPS) is of interest for applications which want to transfer data, so it is only relevant to the data transfer phase of a connection (unless one wants to send data on the DCCP-Request, but that is not considered here). The strategy chosen to deal with this requirement is to leave room for only such options that may appear on data packets. A special consideration applies to Ack Vectors: this is purely guesswork, since these can have any length between 3 and 1020 bytes. The strategy chosen here is to subtract a configurable minimum, the value of 16 bytes (2 bytes for type/length plus 14 Ack Vector cells) has been found by experimentatation. If people experience this as too much or too little, this could later be turned into a Kconfig option. There are currently no CCID-specific header options which may appear on data packets, hence it is not necessary to define a corresponding CCID field. Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk> Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
160 lines
4.3 KiB
C
160 lines
4.3 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 the DCCP protocol
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* Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@mandriva.com>
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*
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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/ktime.h>
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#include <linux/list.h>
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#include <linux/types.h>
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/* We can spread an ack vector across multiple options */
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#define DCCP_MAX_ACKVEC_LEN (DCCP_SINGLE_OPT_MAXLEN * 2)
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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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#define DCCP_ACKVEC_STATE_RECEIVED 0
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#define DCCP_ACKVEC_STATE_ECN_MARKED (1 << 6)
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#define DCCP_ACKVEC_STATE_NOT_RECEIVED (3 << 6)
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#define DCCP_ACKVEC_STATE_MASK 0xC0 /* 11000000 */
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#define DCCP_ACKVEC_LEN_MASK 0x3F /* 00111111 */
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/** struct dccp_ackvec - ack vector
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*
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* This data structure is the one defined in RFC 4340, Appendix A.
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*
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* @av_buf_head - circular buffer head
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* @av_buf_tail - circular buffer tail
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* @av_buf_ackno - ack # of the most recent packet acknowledgeable in the
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* buffer (i.e. %av_buf_head)
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* @av_buf_nonce - the one-bit sum of the ECN Nonces on all packets acked
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* by the buffer with State 0
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*
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* Additionally, the HC-Receiver must keep some information about the
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* Ack Vectors it has recently sent. For each packet sent carrying an
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* Ack Vector, it remembers four variables:
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*
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* @av_records - list of dccp_ackvec_record
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* @av_ack_nonce - the one-bit sum of the ECN Nonces for all State 0.
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*
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* @av_time - the time in usecs
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* @av_buf - circular buffer of acknowledgeable packets
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*/
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struct dccp_ackvec {
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u64 av_buf_ackno;
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struct list_head av_records;
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ktime_t av_time;
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u16 av_buf_head;
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u16 av_vec_len;
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u8 av_buf_nonce;
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u8 av_ack_nonce;
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u8 av_buf[DCCP_MAX_ACKVEC_LEN];
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};
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/** struct dccp_ackvec_record - ack vector record
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*
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* ACK vector record as defined in Appendix A of spec.
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*
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* The list is sorted by avr_ack_seqno
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*
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* @avr_node - node in av_records
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* @avr_ack_seqno - sequence number of the packet this record was sent on
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* @avr_ack_ackno - sequence number being acknowledged
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* @avr_ack_ptr - pointer into av_buf where this record starts
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* @avr_ack_nonce - av_ack_nonce at the time this record was sent
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* @avr_sent_len - lenght of the record in av_buf
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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;
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u64 avr_ack_ackno;
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u16 avr_ack_ptr;
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u16 avr_sent_len;
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u8 avr_ack_nonce;
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};
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struct sock;
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struct sk_buff;
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#ifdef CONFIG_IP_DCCP_ACKVEC
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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_insert_option_ackvec(struct sock *sk, struct sk_buff *skb);
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static inline int dccp_ackvec_pending(const struct dccp_ackvec *av)
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{
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return av->av_vec_len;
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}
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#else /* CONFIG_IP_DCCP_ACKVEC */
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static inline int dccp_ackvec_init(void)
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{
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return 0;
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}
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static inline void dccp_ackvec_exit(void)
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{
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}
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static inline struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority)
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{
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return NULL;
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}
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static inline void dccp_ackvec_free(struct dccp_ackvec *av)
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{
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}
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static inline 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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{
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return -1;
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}
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static inline void dccp_ackvec_check_rcv_ackno(struct dccp_ackvec *av,
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struct sock *sk, const u64 ackno)
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{
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}
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static inline int dccp_ackvec_parse(struct sock *sk, const struct sk_buff *skb,
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const u64 *ackno, const u8 opt,
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const u8 *value, const u8 len)
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{
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return -1;
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}
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static inline int dccp_insert_option_ackvec(const struct sock *sk,
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const struct sk_buff *skb)
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{
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return -1;
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}
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static inline int dccp_ackvec_pending(const struct dccp_ackvec *av)
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{
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return 0;
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}
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#endif /* CONFIG_IP_DCCP_ACKVEC */
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#endif /* _ACKVEC_H */
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