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
  25 enum 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
  33 enum 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  */
  47 typedef 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  */
  66 struct 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
  79 static 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  */
  93 struct 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  */
 103 extern unsigned long sysctl_dccp_sequence_window;
 104 extern int           sysctl_dccp_rx_ccid;
 105 extern int           sysctl_dccp_tx_ccid;
 106
 107 int dccp_feat_init(struct sock *sk);
 108 void dccp_feat_initialise_sysctls(void);
 109 int dccp_feat_register_sp(struct sock *sk, u8 feat, u8 is_local,
 110                           u8 const *list, u8 len);
 111 int dccp_feat_parse_options(struct sock *, struct dccp_request_sock *,
 112                             u8 mand, u8 opt, u8 feat, u8 *val, u8 len);
 113 int 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
 127 void dccp_encode_value_var(const u64 value, u8 *to, const u8 len);
 128 u64 dccp_decode_value_var(const u8 *bf, const u8 len);
 129 u64 dccp_feat_nn_get(struct sock *sk, u8 feat);
 130
 131 int dccp_insert_option_mandatory(struct sk_buff *skb);
 132 int 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 */