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 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