net/dccp/feat.h

0001 /* SPDX-License-Identifier: GPL-2.0-only */
0002 #ifndef _DCCP_FEAT_H
0003 #define _DCCP_FEAT_H
0004 /*
0005  *  net/dccp/feat.h
0006  *
0007  *  Feature negotiation for the DCCP protocol (RFC 4340, section 6)
0008  *  Copyright (c) 2008 Gerrit Renker <gerrit@erg.abdn.ac.uk>
0009  *  Copyright (c) 2005 Andrea Bittau <a.bittau@cs.ucl.ac.uk>
0010  */
0011 #include <linux/types.h>
0012 #include "dccp.h"
0013
0014 /*
0015  * Known limit values
0016  */
0017 /* Ack Ratio takes 2-byte integer values (11.3) */
0018 #define DCCPF_ACK_RATIO_MAX 0xFFFF
0019 /* Wmin=32 and Wmax=2^46-1 from 7.5.2 */
0020 #define DCCPF_SEQ_WMIN      32
0021 #define DCCPF_SEQ_WMAX      0x3FFFFFFFFFFFull
0022 /* Maximum number of SP values that fit in a single (Confirm) option */
0023 #define DCCP_FEAT_MAX_SP_VALS   (DCCP_SINGLE_OPT_MAXLEN - 2)
0024
0025 enum dccp_feat_type {
0026     FEAT_AT_RX   = 1,   /* located at RX side of half-connection  */
0027     FEAT_AT_TX   = 2,   /* located at TX side of half-connection  */
0028     FEAT_SP      = 4,   /* server-priority reconciliation (6.3.1) */
0029     FEAT_NN      = 8,   /* non-negotiable reconciliation (6.3.2)  */
0030     FEAT_UNKNOWN = 0xFF /* not understood or invalid feature      */
0031 };
0032
0033 enum dccp_feat_state {
0034     FEAT_DEFAULT = 0,   /* using default values from 6.4 */
0035     FEAT_INITIALISING,  /* feature is being initialised  */
0036     FEAT_CHANGING,      /* Change sent but not confirmed yet */
0037     FEAT_UNSTABLE,      /* local modification in state CHANGING */
0038     FEAT_STABLE     /* both ends (think they) agree */
0039 };
0040
0041 /**
0042  * dccp_feat_val  -  Container for SP or NN feature values
0043  * @nn:     single NN value
0044  * @sp.vec: single SP value plus optional preference list
0045  * @sp.len: length of @sp.vec in bytes
0046  */
0047 typedef union {
0048     u64 nn;
0049     struct {
0050         u8  *vec;
0051         u8  len;
0052     }   sp;
0053 } dccp_feat_val;
0054
0055 /**
0056  * struct feat_entry  -  Data structure to perform feature negotiation
0057  * @val: feature's current value (SP features may have preference list)
0058  * @state: feature's current state
0059  * @feat_num: one of %dccp_feature_numbers
0060  * @needs_mandatory: whether Mandatory options should be sent
0061  * @needs_confirm: whether to send a Confirm instead of a Change
0062  * @empty_confirm: whether to send an empty Confirm (depends on @needs_confirm)
0063  * @is_local: feature location (1) or feature-remote (0)
0064  * @node: list pointers, entries arranged in FIFO order
0065  */
0066 struct dccp_feat_entry {
0067     dccp_feat_val           val;
0068     enum dccp_feat_state    state:8;
0069     u8                      feat_num;
0070
0071     bool            needs_mandatory,
0072                 needs_confirm,
0073                 empty_confirm,
0074                 is_local;
0075
0076     struct list_head    node;
0077 };
0078
0079 static inline u8 dccp_feat_genopt(struct dccp_feat_entry *entry)
0080 {
0081     if (entry->needs_confirm)
0082         return entry->is_local ? DCCPO_CONFIRM_L : DCCPO_CONFIRM_R;
0083     return entry->is_local ? DCCPO_CHANGE_L : DCCPO_CHANGE_R;
0084 }
0085
0086 /**
0087  * struct ccid_dependency  -  Track changes resulting from choosing a CCID
0088  * @dependent_feat: one of %dccp_feature_numbers
0089  * @is_local: local (1) or remote (0) @dependent_feat
0090  * @is_mandatory: whether presence of @dependent_feat is mission-critical or not
0091  * @val: corresponding default value for @dependent_feat (u8 is sufficient here)
0092  */
0093 struct ccid_dependency {
0094     u8  dependent_feat;
0095     bool    is_local:1,
0096         is_mandatory:1;
0097     u8  val;
0098 };
0099
0100 /*
0101  * Sysctls to seed defaults for feature negotiation
0102  */
0103 extern unsigned long sysctl_dccp_sequence_window;
0104 extern int       sysctl_dccp_rx_ccid;
0105 extern int       sysctl_dccp_tx_ccid;
0106
0107 int dccp_feat_init(struct sock *sk);
0108 void dccp_feat_initialise_sysctls(void);
0109 int dccp_feat_register_sp(struct sock *sk, u8 feat, u8 is_local,
0110               u8 const *list, u8 len);
0111 int dccp_feat_parse_options(struct sock *, struct dccp_request_sock *,
0112                 u8 mand, u8 opt, u8 feat, u8 *val, u8 len);
0113 int dccp_feat_clone_list(struct list_head const *, struct list_head *);
0114
0115 /*
0116  * Encoding variable-length options and their maximum length.
0117  *
0118  * This affects NN options (SP options are all u8) and other variable-length
0119  * options (see table 3 in RFC 4340). The limit is currently given the Sequence
0120  * Window NN value (sec. 7.5.2) and the NDP count (sec. 7.7) option, all other
0121  * options consume less than 6 bytes (timestamps are 4 bytes).
0122  * When updating this constant (e.g. due to new internet drafts / RFCs), make
0123  * sure that you also update all code which refers to it.
0124  */
0125 #define DCCP_OPTVAL_MAXLEN  6
0126
0127 void dccp_encode_value_var(const u64 value, u8 *to, const u8 len);
0128 u64 dccp_decode_value_var(const u8 *bf, const u8 len);
0129 u64 dccp_feat_nn_get(struct sock *sk, u8 feat);
0130
0131 int dccp_insert_option_mandatory(struct sk_buff *skb);
0132 int dccp_insert_fn_opt(struct sk_buff *skb, u8 type, u8 feat, u8 *val, u8 len,
0133                bool repeat_first);
0134 #endif /* _DCCP_FEAT_H */