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
28enum 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
36enum 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 */
50typedef 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 */
69struct 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
82static 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 */
96struct 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 */
106extern unsigned long sysctl_dccp_sequence_window;
107extern int	     sysctl_dccp_rx_ccid;
108extern int	     sysctl_dccp_tx_ccid;
109
110extern int  dccp_feat_init(struct sock *sk);
111extern void dccp_feat_initialise_sysctls(void);
112extern int  dccp_feat_register_sp(struct sock *sk, u8 feat, u8 is_local,
113				  u8 const *list, u8 len);
114extern int  dccp_feat_register_nn(struct sock *sk, u8 feat, u64 val);
115extern int  dccp_feat_parse_options(struct sock *, struct dccp_request_sock *,
116				    u8 mand, u8 opt, u8 feat, u8 *val, u8 len);
117extern int  dccp_feat_clone_list(struct list_head const *, struct list_head *);
118
119/*
120 * Encoding variable-length options and their maximum length.
121 *
122 * This affects NN options (SP options are all u8) and other variable-length
123 * options (see table 3 in RFC 4340). The limit is currently given the Sequence
124 * Window NN value (sec. 7.5.2) and the NDP count (sec. 7.7) option, all other
125 * options consume less than 6 bytes (timestamps are 4 bytes).
126 * When updating this constant (e.g. due to new internet drafts / RFCs), make
127 * sure that you also update all code which refers to it.
128 */
129#define DCCP_OPTVAL_MAXLEN	6
130
131extern void dccp_encode_value_var(const u64 value, u8 *to, const u8 len);
132extern u64  dccp_decode_value_var(const u8 *bf, const u8 len);
133
134extern int  dccp_insert_option_mandatory(struct sk_buff *skb);
135extern int  dccp_insert_fn_opt(struct sk_buff *skb, u8 type, u8 feat,
136			       u8 *val, u8 len, bool repeat_first);
137#endif /* _DCCP_FEAT_H */
138