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);
108int dccp_feat_register_sp(struct sock *sk, u8 feat, u8 is_local,
109			  u8 const *list, u8 len);
110int dccp_feat_parse_options(struct sock *, struct dccp_request_sock *,
111			    u8 mand, u8 opt, u8 feat, u8 *val, u8 len);
112int dccp_feat_clone_list(struct list_head const *, struct list_head *);
113
114/*
115 * Encoding variable-length options and their maximum length.
116 *
117 * This affects NN options (SP options are all u8) and other variable-length
118 * options (see table 3 in RFC 4340). The limit is currently given the Sequence
119 * Window NN value (sec. 7.5.2) and the NDP count (sec. 7.7) option, all other
120 * options consume less than 6 bytes (timestamps are 4 bytes).
121 * When updating this constant (e.g. due to new internet drafts / RFCs), make
122 * sure that you also update all code which refers to it.
123 */
124#define DCCP_OPTVAL_MAXLEN	6
125
126void dccp_encode_value_var(const u64 value, u8 *to, const u8 len);
127u64 dccp_decode_value_var(const u8 *bf, const u8 len);
128u64 dccp_feat_nn_get(struct sock *sk, u8 feat);
129
130int dccp_insert_option_mandatory(struct sk_buff *skb);
131int dccp_insert_fn_opt(struct sk_buff *skb, u8 type, u8 feat, u8 *val, u8 len,
132		       bool repeat_first);
133#endif /* _DCCP_FEAT_H */
134