feat.h

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#ifndef _DCCP_FEAT_H
#define _DCCP_FEAT_H
/*
 *  net/dccp/feat.h
 *
 *  Feature negotiation for the DCCP protocol (RFC 4340, section 6)
 *  Copyright (c) 2008 Gerrit Renker <[email protected]>
 *  Copyright (c) 2005 Andrea Bittau <[email protected]>
 *
 *  This program is free software; you can redistribute it and/or modify it
 *  under the terms of the GNU General Public License version 2 as
 *  published by the Free Software Foundation.
 */
#include <linux/types.h>
#include "dccp.h"

/*
 * Known limit values
 */
/* Ack Ratio takes 2-byte integer values (11.3) */
#define DCCPF_ACK_RATIO_MAX 0xFFFF
/* Wmin=32 and Wmax=2^46-1 from 7.5.2 */
#define DCCPF_SEQ_WMIN      32
#define DCCPF_SEQ_WMAX      0x3FFFFFFFFFFFull
/* Maximum number of SP values that fit in a single (Confirm) option */
#define DCCP_FEAT_MAX_SP_VALS   (DCCP_SINGLE_OPT_MAXLEN - 2)

enum dccp_feat_type {
    FEAT_AT_RX   = 1,   /* located at RX side of half-connection  */
    FEAT_AT_TX   = 2,   /* located at TX side of half-connection  */
    FEAT_SP      = 4,   /* server-priority reconciliation (6.3.1) */
    FEAT_NN      = 8,   /* non-negotiable reconciliation (6.3.2)  */
    FEAT_UNKNOWN = 0xFF /* not understood or invalid feature      */
};

enum dccp_feat_state {
    FEAT_DEFAULT = 0,   /* using default values from 6.4 */
    FEAT_INITIALISING,  /* feature is being initialised  */
    FEAT_CHANGING,      /* Change sent but not confirmed yet */
    FEAT_UNSTABLE,      /* local modification in state CHANGING */
    FEAT_STABLE     /* both ends (think they) agree */
};

typedef union {
    u64 nn;
    struct {
        u8  *vec;
        u8  len;
    }   sp;
} dccp_feat_val;

struct dccp_feat_entry {
    dccp_feat_val           val;
    enum dccp_feat_state    state:8;
    u8                      feat_num;

    bool            needs_mandatory,
                needs_confirm,
                empty_confirm,
                is_local;

    struct list_head    node;
};

static inline u8 dccp_feat_genopt(struct dccp_feat_entry *entry)
{
    if (entry->needs_confirm)
        return entry->is_local ? DCCPO_CONFIRM_L : DCCPO_CONFIRM_R;
    return entry->is_local ? DCCPO_CHANGE_L : DCCPO_CHANGE_R;
}

struct ccid_dependency {
    u8  dependent_feat;
    bool    is_local:1,
        is_mandatory:1;
    u8  val;
};

/*
 * Sysctls to seed defaults for feature negotiation
 */
extern unsigned long sysctl_dccp_sequence_window;
extern int       sysctl_dccp_rx_ccid;
extern int       sysctl_dccp_tx_ccid;

extern int  dccp_feat_init(struct sock *sk);
extern void dccp_feat_initialise_sysctls(void);
extern int  dccp_feat_register_sp(struct sock *sk, u8 feat, u8 is_local,
                  u8 const *list, u8 len);
extern int  dccp_feat_parse_options(struct sock *, struct dccp_request_sock *,
                    u8 mand, u8 opt, u8 feat, u8 *val, u8 len);
extern int  dccp_feat_clone_list(struct list_head const *, struct list_head *);

/*
 * Encoding variable-length options and their maximum length.
 *
 * This affects NN options (SP options are all u8) and other variable-length
 * options (see table 3 in RFC 4340). The limit is currently given the Sequence
 * Window NN value (sec. 7.5.2) and the NDP count (sec. 7.7) option, all other
 * options consume less than 6 bytes (timestamps are 4 bytes).
 * When updating this constant (e.g. due to new internet drafts / RFCs), make
 * sure that you also update all code which refers to it.
 */
#define DCCP_OPTVAL_MAXLEN  6

extern void dccp_encode_value_var(const u64 value, u8 *to, const u8 len);
extern u64  dccp_decode_value_var(const u8 *bf, const u8 len);
extern u64  dccp_feat_nn_get(struct sock *sk, u8 feat);

extern int  dccp_insert_option_mandatory(struct sk_buff *skb);
extern int  dccp_insert_fn_opt(struct sk_buff *skb, u8 type, u8 feat,
                   u8 *val, u8 len, bool repeat_first);
#endif /* _DCCP_FEAT_H */