linux/net/dccp/feat.h
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   1#ifndef _DCCP_FEAT_H
   2#define _DCCP_FEAT_H
   3/*
   4 *  net/dccp/feat.h
   5 *
   6 *  Feature negotiation for the DCCP protocol (RFC 4340, section 6)
   7 *  Copyright (c) 2008 Gerrit Renker <gerrit@erg.abdn.ac.uk>
   8 *  Copyright (c) 2005 Andrea Bittau <a.bittau@cs.ucl.ac.uk>
   9 *
  10 *  This program is free software; you can redistribute it and/or modify it
  11 *  under the terms of the GNU General Public License version 2 as
  12 *  published by the Free Software Foundation.
  13 */
  14#include <linux/types.h>
  15#include "dccp.h"
  16
  17/*
  18 * Known limit values
  19 */
  20/* Ack Ratio takes 2-byte integer values (11.3) */
  21#define DCCPF_ACK_RATIO_MAX     0xFFFF
  22/* Wmin=32 and Wmax=2^46-1 from 7.5.2 */
  23#define DCCPF_SEQ_WMIN          32
  24#define DCCPF_SEQ_WMAX          0x3FFFFFFFFFFFull
  25/* Maximum number of SP values that fit in a single (Confirm) option */
  26#define DCCP_FEAT_MAX_SP_VALS   (DCCP_SINGLE_OPT_MAXLEN - 2)
  27
  28enum dccp_feat_type {
  29        FEAT_AT_RX   = 1,       /* located at RX side of half-connection  */
  30        FEAT_AT_TX   = 2,       /* located at TX side of half-connection  */
  31        FEAT_SP      = 4,       /* server-priority reconciliation (6.3.1) */
  32        FEAT_NN      = 8,       /* non-negotiable reconciliation (6.3.2)  */
  33        FEAT_UNKNOWN = 0xFF     /* not understood or invalid feature      */
  34};
  35
  36enum dccp_feat_state {
  37        FEAT_DEFAULT = 0,       /* using default values from 6.4 */
  38        FEAT_INITIALISING,      /* feature is being initialised  */
  39        FEAT_CHANGING,          /* Change sent but not confirmed yet */
  40        FEAT_UNSTABLE,          /* local modification in state CHANGING */
  41        FEAT_STABLE             /* both ends (think they) agree */
  42};
  43
  44/**
  45 * dccp_feat_val  -  Container for SP or NN feature values
  46 * @nn:     single NN value
  47 * @sp.vec: single SP value plus optional preference list
  48 * @sp.len: length of @sp.vec in bytes
  49 */
  50typedef union {
  51        u64 nn;
  52        struct {
  53                u8      *vec;
  54                u8      len;
  55        }   sp;
  56} dccp_feat_val;
  57
  58/**
  59 * struct feat_entry  -  Data structure to perform feature negotiation
  60 * @val: feature's current value (SP features may have preference list)
  61 * @state: feature's current state
  62 * @feat_num: one of %dccp_feature_numbers
  63 * @needs_mandatory: whether Mandatory options should be sent
  64 * @needs_confirm: whether to send a Confirm instead of a Change
  65 * @empty_confirm: whether to send an empty Confirm (depends on @needs_confirm)
  66 * @is_local: feature location (1) or feature-remote (0)
  67 * @node: list pointers, entries arranged in FIFO order
  68 */
  69struct dccp_feat_entry {
  70        dccp_feat_val           val;
  71        enum dccp_feat_state    state:8;
  72        u8                      feat_num;
  73
  74        bool                    needs_mandatory,
  75                                needs_confirm,
  76                                empty_confirm,
  77                                is_local;
  78
  79        struct list_head        node;
  80};
  81
  82static inline u8 dccp_feat_genopt(struct dccp_feat_entry *entry)
  83{
  84        if (entry->needs_confirm)
  85                return entry->is_local ? DCCPO_CONFIRM_L : DCCPO_CONFIRM_R;
  86        return entry->is_local ? DCCPO_CHANGE_L : DCCPO_CHANGE_R;
  87}
  88
  89/**
  90 * struct ccid_dependency  -  Track changes resulting from choosing a CCID
  91 * @dependent_feat: one of %dccp_feature_numbers
  92 * @is_local: local (1) or remote (0) @dependent_feat
  93 * @is_mandatory: whether presence of @dependent_feat is mission-critical or not
  94 * @val: corresponding default value for @dependent_feat (u8 is sufficient here)
  95 */
  96struct ccid_dependency {
  97        u8      dependent_feat;
  98        bool    is_local:1,
  99                is_mandatory:1;
 100        u8      val;
 101};
 102
 103/*
 104 * Sysctls to seed defaults for feature negotiation
 105 */
 106extern unsigned long sysctl_dccp_sequence_window;
 107extern int           sysctl_dccp_rx_ccid;
 108extern int           sysctl_dccp_tx_ccid;
 109
 110extern int  dccp_feat_init(struct sock *sk);
 111extern void dccp_feat_initialise_sysctls(void);
 112extern int  dccp_feat_register_sp(struct sock *sk, u8 feat, u8 is_local,
 113                                  u8 const *list, u8 len);
 114extern int  dccp_feat_parse_options(struct sock *, struct dccp_request_sock *,
 115                                    u8 mand, u8 opt, u8 feat, u8 *val, u8 len);
 116extern int  dccp_feat_clone_list(struct list_head const *, struct list_head *);
 117
 118/*
 119 * Encoding variable-length options and their maximum length.
 120 *
 121 * This affects NN options (SP options are all u8) and other variable-length
 122 * options (see table 3 in RFC 4340). The limit is currently given the Sequence
 123 * Window NN value (sec. 7.5.2) and the NDP count (sec. 7.7) option, all other
 124 * options consume less than 6 bytes (timestamps are 4 bytes).
 125 * When updating this constant (e.g. due to new internet drafts / RFCs), make
 126 * sure that you also update all code which refers to it.
 127 */
 128#define DCCP_OPTVAL_MAXLEN      6
 129
 130extern void dccp_encode_value_var(const u64 value, u8 *to, const u8 len);
 131extern u64  dccp_decode_value_var(const u8 *bf, const u8 len);
 132extern u64  dccp_feat_nn_get(struct sock *sk, u8 feat);
 133
 134extern int  dccp_insert_option_mandatory(struct sk_buff *skb);
 135extern int  dccp_insert_fn_opt(struct sk_buff *skb, u8 type, u8 feat,
 136                               u8 *val, u8 len, bool repeat_first);
 137#endif /* _DCCP_FEAT_H */
 138
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