net/dccp/feat.h

   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
  28 enum 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
  36 enum 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  */
  50 typedef 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  */
  69 struct 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
  82 static 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  */
  96 struct 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  */
 106 extern unsigned long sysctl_dccp_sequence_window;
 107 extern int           sysctl_dccp_rx_ccid;
 108 extern int           sysctl_dccp_tx_ccid;
 109
 110 int dccp_feat_init(struct sock *sk);
 111 void dccp_feat_initialise_sysctls(void);
 112 int dccp_feat_register_sp(struct sock *sk, u8 feat, u8 is_local,
 113                           u8 const *list, u8 len);
 114 int dccp_feat_parse_options(struct sock *, struct dccp_request_sock *,
 115                             u8 mand, u8 opt, u8 feat, u8 *val, u8 len);
 116 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
 130 void dccp_encode_value_var(const u64 value, u8 *to, const u8 len);
 131 u64 dccp_decode_value_var(const u8 *bf, const u8 len);
 132 u64 dccp_feat_nn_get(struct sock *sk, u8 feat);
 133
 134 int dccp_insert_option_mandatory(struct sk_buff *skb);
 135 int dccp_insert_fn_opt(struct sk_buff *skb, u8 type, u8 feat, u8 *val, u8 len,
 136                        bool repeat_first);
 137 #endif /* _DCCP_FEAT_H */