xref: /openbmc/linux/net/dccp/feat.h (revision d4a80cc6)
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 
dccp_feat_genopt(struct dccp_feat_entry * entry)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 int dccp_feat_register_sp(struct sock *sk, u8 feat, u8 is_local,
109 			  u8 const *list, u8 len);
110 int dccp_feat_parse_options(struct sock *, struct dccp_request_sock *,
111 			    u8 mand, u8 opt, u8 feat, u8 *val, u8 len);
112 int 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 
126 void dccp_encode_value_var(const u64 value, u8 *to, const u8 len);
127 u64 dccp_decode_value_var(const u8 *bf, const u8 len);
128 u64 dccp_feat_nn_get(struct sock *sk, u8 feat);
129 
130 int dccp_insert_option_mandatory(struct sk_buff *skb);
131 int 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