/*
 * ngtcp2
 *
 * Copyright (c) 2019 ngtcp2 contributors
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
#ifndef NGTCP2_PV_H
#define NGTCP2_PV_H

#ifdef HAVE_CONFIG_H
#  include <config.h>
#endif /* defined(HAVE_CONFIG_H) */

#include <ngtcp2/ngtcp2.h>

#include "ngtcp2_cid.h"
#include "ngtcp2_ringbuf.h"

/* NGTCP2_PV_MAX_ENTRIES is the maximum number of entries that
   ngtcp2_pv can contain.  It must be power of 2. */
#define NGTCP2_PV_MAX_ENTRIES 8
/* NGTCP2_PV_NUM_PROBE_PKT is the number of probe packets containing
   PATH_CHALLENGE sent at a time. */
#define NGTCP2_PV_NUM_PROBE_PKT 2

typedef struct ngtcp2_log ngtcp2_log;

typedef struct ngtcp2_frame_chain ngtcp2_frame_chain;

/* NGTCP2_PV_ENTRY_FLAG_NONE indicates that no flag is set. */
#define NGTCP2_PV_ENTRY_FLAG_NONE 0x00u
/* NGTCP2_PV_ENTRY_FLAG_UNDERSIZED indicates that UDP datagram which
   contains PATH_CHALLENGE is undersized (< 1200 bytes) */
#define NGTCP2_PV_ENTRY_FLAG_UNDERSIZED 0x01u

typedef struct ngtcp2_pv_entry {
  /* expiry is the timestamp when this PATH_CHALLENGE expires. */
  ngtcp2_tstamp expiry;
  /* flags is zero or more of NGTCP2_PV_ENTRY_FLAG_*. */
  uint8_t flags;
  /* data is a byte string included in PATH_CHALLENGE. */
  uint8_t data[NGTCP2_PATH_CHALLENGE_DATALEN];
} ngtcp2_pv_entry;

void ngtcp2_pv_entry_init(ngtcp2_pv_entry *pvent, const uint8_t *data,
                          ngtcp2_tstamp expiry, uint8_t flags);

/* NGTCP2_PV_FLAG_NONE indicates no flag is set. */
#define NGTCP2_PV_FLAG_NONE 0x00u
/* NGTCP2_PV_FLAG_DONT_CARE indicates that the outcome of path
   validation should be ignored entirely. */
#define NGTCP2_PV_FLAG_DONT_CARE 0x01u
/* NGTCP2_PV_FLAG_CANCEL_TIMER indicates that the expiry timer is
   cancelled. */
#define NGTCP2_PV_FLAG_CANCEL_TIMER 0x02u
/* NGTCP2_PV_FLAG_FALLBACK_PRESENT indicates that a fallback
   Destination Connection ID and PTO are available in ngtcp2_pv.  If
   path validation fails, then fallback to them.  If path validation
   succeeds, the fallback Destination Connection ID is retired if it
   is not zero length, and does not equal to the current Destination
   Connection ID. */
#define NGTCP2_PV_FLAG_FALLBACK_PRESENT 0x04u
/* NGTCP2_PV_FLAG_PREFERRED_ADDR indicates that client is migrating to
   server's preferred address.  This flag is only used by client. */
#define NGTCP2_PV_FLAG_PREFERRED_ADDR 0x10u

typedef struct ngtcp2_pv ngtcp2_pv;

ngtcp2_static_ringbuf_def(pv_ents, NGTCP2_PV_MAX_ENTRIES,
                          sizeof(ngtcp2_pv_entry))
/*
 * ngtcp2_pv is the context of a single path validation.
 */
struct ngtcp2_pv {
  const ngtcp2_mem *mem;
  ngtcp2_log *log;
  /* dcid is DCID and path this path validation uses. */
  ngtcp2_dcid dcid;
  /* fallback_dcid is the usually validated DCID and used as a
     fallback if this path validation fails. */
  ngtcp2_dcid fallback_dcid;
  /* ents is the ring buffer of ngtcp2_pv_entry */
  ngtcp2_static_ringbuf_pv_ents ents;
  /* timeout is the duration within which this path validation should
     succeed. */
  ngtcp2_duration timeout;
  /* fallback_pto is PTO of fallback connection. */
  ngtcp2_duration fallback_pto;
  /* started_ts is the timestamp this path validation starts. */
  ngtcp2_tstamp started_ts;
  /* round is the number of times that probe_pkt_left is reset. */
  size_t round;
  /* probe_pkt_left is the number of probe packets containing
     PATH_CHALLENGE which can be send without waiting for an
     expiration of a previous flight. */
  size_t probe_pkt_left;
  /* flags is bitwise-OR of zero or more of NGTCP2_PV_FLAG_*. */
  uint8_t flags;
};

/*
 * ngtcp2_pv_new creates new ngtcp2_pv object and assigns its pointer
 * to |*ppv|.  This function makes a copy of |dcid|.  |timeout| is a
 * duration within which this path validation must succeed.
 *
 * This function returns 0 if it succeeds, or one of the following
 * negative error codes:
 *
 * NGTCP2_ERR_NOMEM
 *     Out of memory
 */
int ngtcp2_pv_new(ngtcp2_pv **ppv, const ngtcp2_dcid *dcid,
                  ngtcp2_duration timeout, uint8_t flags, ngtcp2_log *log,
                  const ngtcp2_mem *mem);

/*
 * ngtcp2_pv_del deallocates |pv|.  This function frees memory |pv|
 * points too.
 */
void ngtcp2_pv_del(ngtcp2_pv *pv);

/*
 * ngtcp2_pv_add_entry adds new entry with |data|.  |expiry| is the
 * expiry time of the entry.
 */
void ngtcp2_pv_add_entry(ngtcp2_pv *pv, const uint8_t *data,
                         ngtcp2_tstamp expiry, uint8_t flags, ngtcp2_tstamp ts);

/*
 * ngtcp2_pv_full returns nonzero if |pv| is full of ngtcp2_pv_entry.
 */
int ngtcp2_pv_full(ngtcp2_pv *pv);

/*
 * ngtcp2_pv_validate validates that the received |data| matches the
 * one of the existing entry.  The flag of ngtcp2_pv_entry that
 * matches |data| is assigned to |*pflags| if this function succeeds.
 *
 * This function returns 0 if it succeeds, or one of the following
 * negative error codes:
 *
 * NGTCP2_ERR_PATH_VALIDATION_FAILED
 *     path validation has failed and must be abandoned
 * NGTCP2_ERR_INVALID_STATE
 *     |pv| includes no entry
 * NGTCP2_ERR_INVALID_ARGUMENT
 *     |pv| does not have an entry which has |data| and |path|
 */
int ngtcp2_pv_validate(ngtcp2_pv *pv, uint8_t *pflags, const uint8_t *data);

/*
 * ngtcp2_pv_handle_entry_expiry checks expiry of existing entries.
 */
void ngtcp2_pv_handle_entry_expiry(ngtcp2_pv *pv, ngtcp2_tstamp ts);

/*
 * ngtcp2_pv_should_send_probe returns nonzero if new entry can be
 * added by ngtcp2_pv_add_entry.
 */
int ngtcp2_pv_should_send_probe(ngtcp2_pv *pv);

/*
 * ngtcp2_pv_validation_timed_out returns nonzero if the path
 * validation fails because of timeout.
 */
int ngtcp2_pv_validation_timed_out(ngtcp2_pv *pv, ngtcp2_tstamp ts);

/*
 * ngtcp2_pv_next_expiry returns the earliest expiry.
 */
ngtcp2_tstamp ngtcp2_pv_next_expiry(ngtcp2_pv *pv);

/*
 * ngtcp2_pv_cancel_expired_timer cancels the expired timer.
 */
void ngtcp2_pv_cancel_expired_timer(ngtcp2_pv *pv, ngtcp2_tstamp ts);

/*
 * ngtcp2_pv_set_fallback sets |dcid| and |pto| as fallback.
 */
void ngtcp2_pv_set_fallback(ngtcp2_pv *pv, const ngtcp2_dcid *dcid,
                            ngtcp2_duration pto);

#endif /* !defined(NGTCP2_PV_H) */
