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 */