LXR linux/net/dccp/feat.h

   1/* SPDX-License-Identifier: GPL-2.0-only */
   2#ifndef _DCCP_FEAT_H
   3#define _DCCP_FEAT_H
   4/*
   5 *  net/dccp/feat.h
   6 *
   7 *  Feature negotiation for the DCCP protocol (RFC 4340, section 6)
   8 *  Copyright (c) 2008 Gerrit Renker <gerrit@erg.abdn.ac.uk>
   9 *  Copyright (c) 2005 Andrea Bittau <a.bittau@cs.ucl.ac.uk>
  10 */
  11#include <linux/types.h>
  12#include "dccp.h"
  13
  14/*
  15 * Known limit values
  16 */
  17/* Ack Ratio takes 2-byte integer values (11.3) */
  18#define DCCPF_ACK_RATIO_MAX     0xFFFF
  19/* Wmin=32 and Wmax=2^46-1 from 7.5.2 */
  20#define DCCPF_SEQ_WMIN          32
  21#define DCCPF_SEQ_WMAX          0x3FFFFFFFFFFFull
  22/* Maximum number of SP values that fit in a single (Confirm) option */
  23#define DCCP_FEAT_MAX_SP_VALS   (DCCP_SINGLE_OPT_MAXLEN - 2)
  24
  25enum dccp_feat_type {
  26        FEAT_AT_RX   = 1,       /* located at RX side of half-connection  */
  27        FEAT_AT_TX   = 2,       /* located at TX side of half-connection  */
  28        FEAT_SP      = 4,       /* server-priority reconciliation (6.3.1) */
  29        FEAT_NN      = 8,       /* non-negotiable reconciliation (6.3.2)  */
  30        FEAT_UNKNOWN = 0xFF     /* not understood or invalid feature      */
  31};
  32
  33enum dccp_feat_state {
  34        FEAT_DEFAULT = 0,       /* using default values from 6.4 */
  35        FEAT_INITIALISING,      /* feature is being initialised  */
  36        FEAT_CHANGING,          /* Change sent but not confirmed yet */
  37        FEAT_UNSTABLE,          /* local modification in state CHANGING */
  38        FEAT_STABLE             /* both ends (think they) agree */
  39};
  40
  41/**
  42 * dccp_feat_val  -  Container for SP or NN feature values
  43 * @nn:     single NN value
  44 * @sp.vec: single SP value plus optional preference list
  45 * @sp.len: length of @sp.vec in bytes
  46 */
  47typedef union {
  48        u64 nn;
  49        struct {
  50                u8      *vec;
  51                u8      len;
  52        }   sp;
  53} dccp_feat_val;
  54
  55/**
  56 * struct feat_entry  -  Data structure to perform feature negotiation
  57 * @val: feature's current value (SP features may have preference list)
  58 * @state: feature's current state
  59 * @feat_num: one of %dccp_feature_numbers
  60 * @needs_mandatory: whether Mandatory options should be sent
  61 * @needs_confirm: whether to send a Confirm instead of a Change
  62 * @empty_confirm: whether to send an empty Confirm (depends on @needs_confirm)
  63 * @is_local: feature location (1) or feature-remote (0)
  64 * @node: list pointers, entries arranged in FIFO order
  65 */
  66struct dccp_feat_entry {
  67        dccp_feat_val           val;
  68        enum dccp_feat_state    state:8;
  69        u8                      feat_num;
  70
  71        bool                    needs_mandatory,
  72                                needs_confirm,
  73                                empty_confirm,
  74                                is_local;
  75
  76        struct list_head        node;
  77};
  78
  79static inline u8 dccp_feat_genopt(struct dccp_feat_entry *entry)
  80{
  81        if (entry->needs_confirm)
  82                return entry->is_local ? DCCPO_CONFIRM_L : DCCPO_CONFIRM_R;
  83        return entry->is_local ? DCCPO_CHANGE_L : DCCPO_CHANGE_R;
  84}
  85
  86/**
  87 * struct ccid_dependency  -  Track changes resulting from choosing a CCID
  88 * @dependent_feat: one of %dccp_feature_numbers
  89 * @is_local: local (1) or remote (0) @dependent_feat
  90 * @is_mandatory: whether presence of @dependent_feat is mission-critical or not
  91 * @val: corresponding default value for @dependent_feat (u8 is sufficient here)
  92 */
  93struct ccid_dependency {
  94        u8      dependent_feat;
  95        bool    is_local:1,
  96                is_mandatory:1;
  97        u8      val;
  98};
  99
 100/*
 101 * Sysctls to seed defaults for feature negotiation
 102 */
 103extern unsigned long sysctl_dccp_sequence_window;
 104extern int           sysctl_dccp_rx_ccid;
 105extern int           sysctl_dccp_tx_ccid;
 106
 107int dccp_feat_init(struct sock *sk);
 108void dccp_feat_initialise_sysctls(void);
 109int dccp_feat_register_sp(struct sock *sk, u8 feat, u8 is_local,
 110                          u8 const *list, u8 len);
 111int dccp_feat_parse_options(struct sock *, struct dccp_request_sock *,
 112                            u8 mand, u8 opt, u8 feat, u8 *val, u8 len);
 113int dccp_feat_clone_list(struct list_head const *, struct list_head *);
 114
 115/*
 116 * Encoding variable-length options and their maximum length.
 117 *
 118 * This affects NN options (SP options are all u8) and other variable-length
 119 * options (see table 3 in RFC 4340). The limit is currently given the Sequence
 120 * Window NN value (sec. 7.5.2) and the NDP count (sec. 7.7) option, all other
 121 * options consume less than 6 bytes (timestamps are 4 bytes).
 122 * When updating this constant (e.g. due to new internet drafts / RFCs), make
 123 * sure that you also update all code which refers to it.
 124 */
 125#define DCCP_OPTVAL_MAXLEN      6
 126
 127void dccp_encode_value_var(const u64 value, u8 *to, const u8 len);
 128u64 dccp_decode_value_var(const u8 *bf, const u8 len);
 129u64 dccp_feat_nn_get(struct sock *sk, u8 feat);
 130
 131int dccp_insert_option_mandatory(struct sk_buff *skb);
 132int dccp_insert_fn_opt(struct sk_buff *skb, u8 type, u8 feat, u8 *val, u8 len,
 133                       bool repeat_first);
 134#endif /* _DCCP_FEAT_H */
 135