fragment.h

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/*
 *  OpenVPN -- An application to securely tunnel IP networks
 *             over a single UDP port, with support for SSL/TLS-based
 *             session authentication and key exchange,
 *             packet encryption, packet authentication, and
 *             packet compression.
 *
 *  Copyright (C) 2002-2021 OpenVPN Inc <sales@openvpn.net>
 *
 *  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.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#ifndef FRAGMENT_H
#define FRAGMENT_H

#ifdef ENABLE_FRAGMENT

#include "common.h"
#include "buffer.h"
#include "interval.h"
#include "mtu.h"
#include "shaper.h"
#include "error.h"


#define N_FRAG_BUF                   25

#define FRAG_TTL_SEC                 10

#define FRAG_WAKEUP_INTERVAL         5

/**************************************************************************/
struct fragment {
    bool defined;               
    int max_frag_size;          
#define FRAG_MAP_MASK 0xFFFFFFFF

#define MAX_FRAGS 32            
    unsigned int map;

    time_t timestamp;           
    struct buffer buf;          
};


struct fragment_list {
    int seq_id;                 
    int index;                  
    struct fragment fragments[N_FRAG_BUF];
};


struct fragment_master {
    struct event_timeout wakeup; 
    bool received_os_mtu_hint;  
#define N_SEQ_ID            256

    int outgoing_seq_id;        
#define MAX_FRAG_PKT_SIZE 65536

    int outgoing_frag_size;     
    int outgoing_frag_id;       
    struct buffer outgoing;     
    struct buffer outgoing_return;
    struct fragment_list incoming;
};


/**************************************************************************//*************************************/

typedef uint32_t fragment_header_type;
#define hton_fragment_header_type(x) htonl(x)

#define ntoh_fragment_header_type(x) ntohl(x)

#define FRAG_TYPE_MASK        0x00000003

#define FRAG_TYPE_SHIFT       0 
#define FRAG_WHOLE            0 
#define FRAG_YES_NOTLAST      1 
#define FRAG_YES_LAST         2 
#define FRAG_TEST             3 
#define FRAG_SEQ_ID_MASK      0x000000ff

#define FRAG_SEQ_ID_SHIFT     2 
#define FRAG_ID_MASK          0x0000001f

#define FRAG_ID_SHIFT         10

/*
 * FRAG_SIZE  14 bits
 *
 * IF FRAG_YES_LAST (FRAG_SIZE):
 *   The max size of a %fragment.  If a %fragment is not the last %fragment in the packet,
 *   then the %fragment size is guaranteed to be equal to the max %fragment size.  Therefore,
 *   max_frag_size is only sent over the wire if FRAG_LAST is set.  Otherwise it is assumed
 *   to be the actual %fragment size received.
 */
#define FRAG_SIZE_MASK        0x00003fff

#define FRAG_SIZE_SHIFT       15

#define FRAG_SIZE_ROUND_SHIFT 2 
#define FRAG_SIZE_ROUND_MASK ((1 << FRAG_SIZE_ROUND_SHIFT) - 1)

/*
 * FRAG_EXTRA 16 bits
 *
 * IF FRAG_WHOLE or FRAG_YES_NOTLAST, these 16 bits are available (not currently used)
 */
#define FRAG_EXTRA_MASK         0x0000ffff

#define FRAG_EXTRA_SHIFT        15
/********************************************/


/**************************************************************************//************/

struct fragment_master *fragment_init(struct frame *frame);


void fragment_frame_init(struct fragment_master *f, const struct frame *frame);


void fragment_free(struct fragment_master *f);
/*******************/


/**************************************************************************/
void fragment_incoming(struct fragment_master *f, struct buffer *buf,
                       const struct frame *frame);

/**************************************************************************/
void fragment_outgoing(struct fragment_master *f, struct buffer *buf,
                       const struct frame *frame);

bool fragment_ready_to_send(struct fragment_master *f, struct buffer *buf,
                            const struct frame *frame);

static inline bool
fragment_outgoing_defined(struct fragment_master *f)
{
    return f->outgoing.len > 0;
}

void fragment_wakeup(struct fragment_master *f, struct frame *frame);


/**************************************************************************//******************/

static inline void
fragment_housekeeping(struct fragment_master *f, struct frame *frame, struct timeval *tv)
{
    if (event_timeout_trigger(&f->wakeup, tv, ETT_DEFAULT))
    {
        fragment_wakeup(f, frame);
    }
}
/*************************/

/****************************************/


#endif /* ifdef ENABLE_FRAGMENT */
#endif /* ifndef FRAGMENT_H */