packets.c

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/***********************************************************************
 Freeciv - Copyright (C) 1996 - A Kjeldberg, L Gregersen, P Unold
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.
 
   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.
***********************************************************************/
 
#ifdef HAVE_CONFIG_H
#include <fc_config.h>
#endif
 
#include "fc_prehdrs.h"
 
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
 
#ifdef HAVE_ARPA_INET_H
#include <arpa/inet.h>
#endif
#ifdef HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif
 
/* utility */
#include "capability.h"
#include "fc_cmdline.h"
#include "fcintl.h"
#include "log.h"
#include "mem.h"
#include "support.h"
 
/* common */
#include "dataio.h"
#include "game.h"
#include "events.h"
#include "map.h"
 
#include "packets.h"
 
#ifdef USE_COMPRESSION
#include <zlib.h>
/*
 * Value for the 16bit size to indicate a jumbo packet
 */
#define JUMBO_SIZE              0xffff
 
/*
 * All values 0 <= size < COMPRESSION_BORDER are uncompressed packets.
 */
#define COMPRESSION_BORDER      (16*1024+1)
 
/*
 * All compressed packets this size or greater are sent as a jumbo packet.
 */
#define JUMBO_BORDER            (64*1024-COMPRESSION_BORDER-1)
 
#define log_compress    log_debug
#define log_compress2   log_debug
 
#define MAX_DECOMPRESSION 400
 
#endif /* USE_COMPRESSION */
 
/* 
 * Valid values are 0, 1 and 2. For 2 you have to set generate_stats
 * to 1 in generate_packets.py.
 */
#define PACKET_SIZE_STATISTICS 0
 
extern const char *const packet_functional_capability;
 
#define SPECHASH_TAG packet_handler
#define SPECHASH_ASTR_KEY_TYPE
#define SPECHASH_IDATA_TYPE struct packet_handlers *
#define SPECHASH_IDATA_FREE (packet_handler_hash_data_free_fn_t) free
#include "spechash.h"
 
static struct packet_handler_hash *packet_handlers = NULL;
 
#ifdef USE_COMPRESSION
static int stat_size_alone = 0;
static int stat_size_uncompressed = 0;
static int stat_size_compressed = 0;
static int stat_size_no_compression = 0;
 
/**********************************************************************/
static inline int get_compression_level(void)
{
  static int level = -2;        /* Magic not initialized, see below. */
 
  if (-2 == level) {
    const char *s = getenv("FREECIV_COMPRESSION_LEVEL");
 
    if (NULL == s || !str_to_int(s, &level) || -1 > level || 9 < level) {
      level = -1;
    }
  }
 
  return level;
}
 
/**********************************************************************/
static bool conn_compression_flush(struct connection *pconn)
{
  int compression_level = get_compression_level();
  uLongf compressed_size = 12 + 1.001 * pconn->compression.queue.size;
  Bytef compressed[compressed_size];
  bool jumbo;
  unsigned long compressed_packet_len;
 
#ifndef FREECIV_NDEBUG
  int error =
#endif
  compress2(compressed, &compressed_size,
            pconn->compression.queue.p,
            pconn->compression.queue.size,
            compression_level);
 
  fc_assert_ret_val(error == Z_OK, FALSE);
 
  /* Compression signalling currently assumes a 2-byte packet length; if that
   * changes, the protocol should probably be changed */
  fc_assert_ret_val(data_type_size(pconn->packet_header.length) == 2, FALSE);
 
  /* Include normal length field in decision */
  jumbo = (compressed_size+2 >= JUMBO_BORDER);
 
  compressed_packet_len = compressed_size + (jumbo ? 6 : 2);
  if (compressed_packet_len < pconn->compression.queue.size) {
    struct raw_data_out dout;
 
    log_compress("COMPRESS: compressed %lu bytes to %ld (level %d)",
                 (unsigned long) pconn->compression.queue.size,
                 compressed_size, compression_level);
    stat_size_uncompressed += pconn->compression.queue.size;
    stat_size_compressed += compressed_size;
 
    if (!jumbo) {
      unsigned char header[2];
 
      FC_STATIC_ASSERT(COMPRESSION_BORDER > MAX_LEN_PACKET,
                       uncompressed_compressed_packet_len_overlap);
 
      log_compress("COMPRESS: sending %ld as normal", compressed_size);
 
      dio_output_init(&dout, header, sizeof(header));
      dio_put_uint16_raw(&dout, 2 + compressed_size + COMPRESSION_BORDER);
      connection_send_data(pconn, header, sizeof(header));
      connection_send_data(pconn, compressed, compressed_size);
    } else {
      unsigned char header[6];
 
      FC_STATIC_ASSERT(JUMBO_SIZE >= JUMBO_BORDER+COMPRESSION_BORDER,
                       compressed_normal_jumbo_packet_len_overlap);
 
      log_compress("COMPRESS: sending %ld as jumbo", compressed_size);
      dio_output_init(&dout, header, sizeof(header));
      dio_put_uint16_raw(&dout, JUMBO_SIZE);
      dio_put_uint32_raw(&dout, 6 + compressed_size);
      connection_send_data(pconn, header, sizeof(header));
      connection_send_data(pconn, compressed, compressed_size);
    }
  } else {
    log_compress("COMPRESS: would enlarge %lu bytes to %ld; "
                 "sending uncompressed",
                 (unsigned long) pconn->compression.queue.size,
                 compressed_packet_len);
    connection_send_data(pconn, pconn->compression.queue.p,
                         pconn->compression.queue.size);
    stat_size_no_compression += pconn->compression.queue.size;
  }
 
  return pconn->used;
}
#endif /* USE_COMPRESSION */
 
/**********************************************************************/
bool conn_compression_thaw(struct connection *pconn)
{
#ifdef USE_COMPRESSION
  pconn->compression.frozen_level--;
  fc_assert_action_msg(pconn->compression.frozen_level >= 0,
                       pconn->compression.frozen_level = 0,
                       "Too many calls to conn_compression_thaw on %s!",
                       conn_description(pconn));
  if (0 == pconn->compression.frozen_level) {
    return conn_compression_flush(pconn);
  }
#endif /* USE_COMPRESSION */
 
  return pconn->used;
}
 
/**********************************************************************/
int send_packet_data(struct connection *pc, unsigned char *data, int len,
                     enum packet_type packet_type)
{
  /* default for the server */
  int result = 0;
 
  log_packet("sending packet type=%s(%d) len=%d to %s",
             packet_name(packet_type), packet_type, len,
             is_server() ? pc->username : "server");
 
  if (!is_server()) {
    pc->client.last_request_id_used =
        get_next_request_id(pc->client.last_request_id_used);
    result = pc->client.last_request_id_used;
    log_packet("sending request %d", result);
  }
 
  if (pc->outgoing_packet_notify) {
    pc->outgoing_packet_notify(pc, packet_type, len, result);
  }
 
#ifdef USE_COMPRESSION
  if (TRUE) {
    int size = len;
 
    if (conn_compression_frozen(pc)) {
      size_t old_size;
 
      /* Keep this a decent amount less than MAX_LEN_BUFFER to avoid the
       * (remote) possibility of trying to dump MAX_LEN_BUFFER to the
       * network in one go */
#define MAX_LEN_COMPRESS_QUEUE (MAX_LEN_BUFFER/2)
      FC_STATIC_ASSERT(MAX_LEN_COMPRESS_QUEUE < MAX_LEN_BUFFER,
                       compress_queue_maxlen_too_big);
 
      /* If this packet would cause us to overfill the queue, flush
       * everything that's in there already before queuing this one */
      if (MAX_LEN_COMPRESS_QUEUE
          < byte_vector_size(&pc->compression.queue) + len) {
        log_compress2("COMPRESS: huge queue, forcing to flush (%lu/%lu)",
                      (long unsigned)
                      byte_vector_size(&pc->compression.queue),
                      (long unsigned) MAX_LEN_COMPRESS_QUEUE);
        if (!conn_compression_flush(pc)) {
          return -1;
        }
        byte_vector_reserve(&pc->compression.queue, 0);
      }
 
      old_size = byte_vector_size(&pc->compression.queue);
      byte_vector_reserve(&pc->compression.queue, old_size + len);
      memcpy(pc->compression.queue.p + old_size, data, len);
      log_compress2("COMPRESS: putting %s into the queue",
                    packet_name(packet_type));
    } else {
      stat_size_alone += size;
      log_compress("COMPRESS: sending %s alone (%d bytes total)",
                   packet_name(packet_type), stat_size_alone);
      connection_send_data(pc, data, len);
    }
 
    log_compress2("COMPRESS: STATS: alone=%d compression-expand=%d "
                  "compression (before/after) = %d/%d",
                  stat_size_alone, stat_size_no_compression,
                  stat_size_uncompressed, stat_size_compressed);
  }
#else  /* USE_COMPRESSION */
  connection_send_data(pc, data, len);
#endif /* USE_COMPRESSION */
 
#if PACKET_SIZE_STATISTICS
  {
    static struct {
      int counter;
      int size;
    } packets_stats[PACKET_LAST];
    static int packet_counter = 0;
    static int last_start_turn_seen = -1;
    static bool start_turn_seen = FALSE;
 
    int size = len;
    bool print = FALSE;
    bool clear = FALSE;
 
    if (!packet_counter) {
      int i;
 
      for (i = 0; i < PACKET_LAST; i++) {
        packets_stats[i].counter = 0;
        packets_stats[i].size = 0;
      }
    }
 
    packets_stats[packet_type].counter++;
    packets_stats[packet_type].size += size;
 
    packet_counter++;
    if (packet_type == PACKET_START_TURN
        && last_start_turn_seen != game.turn) {
      start_turn_seen = TRUE;
      last_start_turn_seen = game.turn;
    }
 
    if ((packet_type ==
         PACKET_PROCESSING_FINISHED || packet_type == PACKET_THAW_HINT)
        && start_turn_seen) {
      start_turn_seen = FALSE;
      print = TRUE;
      clear = TRUE;
    }
 
    if (print) {
      int i, sum = 0;
#define log_ll log_debug
 
#if PACKET_SIZE_STATISTICS == 2
      delta_stats_report();
#endif
      log_ll("Transmitted packets:");
      log_ll("%8s %8s %8s %s", "Packets", "Bytes", "Byt/Pac", "Name");
 
      for (i = 0; i < PACKET_LAST; i++) {
        if (packets_stats[i].counter == 0) {
          continue;
        }
        sum += packets_stats[i].size;
        log_ll("%8d %8d %8d %s(%i)",
               packets_stats[i].counter, packets_stats[i].size,
               packets_stats[i].size / packets_stats[i].counter,
               packet_name(i),i);
      }
      log_test("turn=%d; transmitted %d bytes in %d packets;average size "
               "per packet %d bytes", game.turn, sum, packet_counter,
               sum / packet_counter);
      log_test("turn=%d; transmitted %d bytes", game.turn,
               pc->statistics.bytes_send);
    }
    if (clear) {
      int i;
 
      for (i = 0; i < PACKET_LAST; i++) {
        packets_stats[i].counter = 0;
        packets_stats[i].size = 0;
      }
      packet_counter = 0;
      pc->statistics.bytes_send = 0;
      delta_stats_reset();
    }
  }
#undef log_ll
#endif /* PACKET_SIZE_STATISTICS */
 
  return result;
}
 
/**********************************************************************/
void *get_packet_from_connection_raw(struct connection *pc,
                                     enum packet_type *ptype)
{
  int len_read;
  int whole_packet_len;
  struct {
    enum packet_type type;
    int itype;
  } utype;
  struct data_in din;
#ifdef USE_COMPRESSION
  bool compressed_packet = FALSE;
  int header_size = 0;
#endif
  void *data;
  void *(*receive_handler)(struct connection *);
 
  if (!pc->used) {
    return NULL; /* connection was closed, stop reading */
  }
  
  if (pc->buffer->ndata < data_type_size(pc->packet_header.length)) {
    /* Not got enough for a length field yet */
    return NULL;
  }
 
  dio_input_init(&din, pc->buffer->data, pc->buffer->ndata);
  dio_get_type_raw(&din, pc->packet_header.length, &len_read);
 
  /* The non-compressed case */
  whole_packet_len = len_read;
 
#ifdef USE_COMPRESSION
  /* Compression signalling currently assumes a 2-byte packet length; if that
   * changes, the protocol should probably be changed */
  fc_assert(data_type_size(pc->packet_header.length) == 2);
  if (len_read == JUMBO_SIZE) {
    compressed_packet = TRUE;
    header_size = 6;
    if (dio_input_remaining(&din) >= 4) {
      dio_get_uint32_raw(&din, &whole_packet_len);
      log_compress("COMPRESS: got a jumbo packet of size %d",
                   whole_packet_len);
    } else {
      /* to return NULL below */
      whole_packet_len = 6;
    }
  } else if (len_read >= COMPRESSION_BORDER) {
    compressed_packet = TRUE;
    header_size = 2;
    whole_packet_len = len_read - COMPRESSION_BORDER;
    log_compress("COMPRESS: got a normal packet of size %d",
                 whole_packet_len);
  }
#endif /* USE_COMPRESSION */
 
  if ((unsigned)whole_packet_len > pc->buffer->ndata) {
    return NULL; /* not all data has been read */
  }
 
#ifdef USE_COMPRESSION
  if (whole_packet_len < header_size) {
    log_verbose("The packet size is reported to be less than header alone. "
                "The connection will be closed now.");
    connection_close(pc, _("illegal packet size"));
 
    return NULL;
  }
 
  if (compressed_packet) {
    uLong compressed_size = whole_packet_len - header_size;
    int decompress_factor = 80;
    unsigned long int decompressed_size = decompress_factor * compressed_size;
    int error = Z_BUF_ERROR;
    struct socket_packet_buffer *buffer = pc->buffer;
    void *decompressed = fc_malloc(decompressed_size);
 
    do {
      error =
        uncompress(decompressed, &decompressed_size,
                   ADD_TO_POINTER(buffer->data, header_size),
                   compressed_size);
 
      if (error == Z_BUF_ERROR) {
        decompress_factor += 50;
        decompressed_size = decompress_factor * compressed_size;
        decompressed = fc_realloc(decompressed, decompressed_size);
      }
 
      if (error != Z_OK) {
        if (error != Z_BUF_ERROR || decompress_factor > MAX_DECOMPRESSION ) {
          log_verbose("Uncompressing of the packet stream failed. "
                      "The connection will be closed now.");
          connection_close(pc, _("decoding error"));
          return NULL;
        }
      }
 
    } while (error != Z_OK);
 
    buffer->ndata -= whole_packet_len;
    /* 
     * Remove the packet with the compressed data and shift all the
     * remaining data to the front. 
     */
    memmove(buffer->data, buffer->data + whole_packet_len, buffer->ndata);
 
    if (buffer->ndata + decompressed_size > buffer->nsize) {
      buffer->nsize += decompressed_size;
      buffer->data = fc_realloc(buffer->data, buffer->nsize);
    }
 
    /*
     * Make place for the uncompressed data by moving the remaining
     * data.
     */
    memmove(buffer->data + decompressed_size, buffer->data, buffer->ndata);
 
    /* 
     * Copy the uncompressed data.
     */
    memcpy(buffer->data, decompressed, decompressed_size);
 
    free(decompressed);
 
    buffer->ndata += decompressed_size;
    
    log_compress("COMPRESS: decompressed %ld into %ld",
                 compressed_size, decompressed_size);
 
    return get_packet_from_connection(pc, ptype);
  }
#endif /* USE_COMPRESSION */
 
  /*
   * At this point the packet is a plain uncompressed one. These have
   * to have to be at least the header bytes in size.
   */
  if (whole_packet_len < (data_type_size(pc->packet_header.length)
                          + data_type_size(pc->packet_header.type))) {
    log_verbose("The packet stream is corrupt. The connection "
                "will be closed now.");
    connection_close(pc, _("decoding error"));
    return NULL;
  }
 
  dio_get_type_raw(&din, pc->packet_header.type, &utype.itype);
  utype.type = utype.itype;
 
  if (utype.type >= PACKET_LAST
      || (receive_handler = pc->phs.handlers->receive[utype.type]) == NULL) {
    log_verbose("Received unsupported packet type %d (%s). The connection "
                "will be closed now.",
                utype.type, packet_name(utype.type));
    connection_close(pc, _("unsupported packet type"));
    return NULL;
  }
 
  log_packet("got packet type=(%s)%d len=%d from %s",
             packet_name(utype.type), utype.itype, whole_packet_len,
             is_server() ? pc->username : "server");
 
  *ptype = utype.type;
 
  if (pc->incoming_packet_notify) {
    pc->incoming_packet_notify(pc, utype.type, whole_packet_len);
  }
 
#if PACKET_SIZE_STATISTICS 
  {
    static struct {
      int counter;
      int size;
    } packets_stats[PACKET_LAST];
    static int packet_counter = 0;
 
    int packet_type = utype.itype;
    int size = whole_packet_len;
 
    if (!packet_counter) {
      int i;
 
      for (i = 0; i < PACKET_LAST; i++) {
        packets_stats[i].counter = 0;
        packets_stats[i].size = 0;
      }
    }
 
    packets_stats[packet_type].counter++;
    packets_stats[packet_type].size += size;
 
    packet_counter++;
    if (packet_counter % 100 == 0) {
      int i, sum = 0;
 
      log_test("Received packets:");
      for (i = 0; i < PACKET_LAST; i++) {
        if (packets_stats[i].counter == 0) {
          continue;
        }
        sum += packets_stats[i].size;
        log_test("  [%-25.25s %3d]: %6d packets; %8d bytes total; "
                 "%5d bytes/packet average",
                 packet_name(i), i, packets_stats[i].counter,
                 packets_stats[i].size,
                 packets_stats[i].size / packets_stats[i].counter);
      }
      log_test("received %d bytes in %d packets;average size "
               "per packet %d bytes",
               sum, packet_counter, sum / packet_counter);
    }
  }
#endif /* PACKET_SIZE_STATISTICS */
  data = receive_handler(pc);
  if (!data) {
    connection_close(pc, _("incompatible packet contents"));
    return NULL;
  } else {
    return data;
  }
}
 
/**********************************************************************/
void remove_packet_from_buffer(struct socket_packet_buffer *buffer)
{
  struct data_in din;
  int len;
 
  dio_input_init(&din, buffer->data, buffer->ndata);
  dio_get_uint16_raw(&din, &len);
  memmove(buffer->data, buffer->data + len, buffer->ndata - len);
  buffer->ndata -= len;
  log_debug("remove_packet_from_buffer: remove %d; remaining %d",
            len, buffer->ndata);
}
 
/**********************************************************************/
void packet_header_init(struct packet_header *packet_header)
{
  packet_header->length = DIOT_UINT16;
  packet_header->type = DIOT_UINT8;
}
 
/**********************************************************************/
static inline void packet_header_set(struct packet_header *packet_header)
{
  /* Ensure we have values initialized in packet_header_init(). */
  fc_assert(packet_header->length == DIOT_UINT16);
  fc_assert(packet_header->type == DIOT_UINT8);
 
  packet_header->length = DIOT_UINT16;
  packet_header->type = DIOT_UINT16;
}
 
/**********************************************************************/
void post_send_packet_server_join_reply(struct connection *pconn,
                                        const struct packet_server_join_reply
                                        *packet)
{
  if (packet->you_can_join) {
    packet_header_set(&pconn->packet_header);
  }
}
 
/**********************************************************************/
void post_receive_packet_server_join_reply(struct connection *pconn,
                                           const struct
                                           packet_server_join_reply *packet)
{
  if (packet->you_can_join) {
    packet_header_set(&pconn->packet_header);
  }
}
 
 
/**********************************************************************/
bool packet_check(struct data_in *din, struct connection *pc)
{
  size_t rem = dio_input_remaining(din);
 
  if (rem > 0) {
    int type, len;
 
    dio_input_rewind(din);
    dio_get_type_raw(din, pc->packet_header.length, &len);
    dio_get_type_raw(din, pc->packet_header.type, &type);
 
    log_packet("received long packet (type %d, len %d, rem %lu) from %s",
               type,
               len,
               (unsigned long) rem,
               conn_description (pc));
    return FALSE;
  }
 
  return TRUE;
}
 
/**********************************************************************/
void generic_handle_player_attribute_chunk(struct player *pplayer,
                                           const struct
                                           packet_player_attribute_chunk
                                           *chunk)
{
  log_packet("received attribute chunk %u/%u %u",
             (unsigned int) chunk->offset,
             (unsigned int) chunk->total_length,
             (unsigned int) chunk->chunk_length);
 
  if (chunk->total_length < 0
      || chunk->chunk_length < 0
      || chunk->total_length >= MAX_ATTRIBUTE_BLOCK
      || chunk->offset < 0
      || chunk->offset > chunk->total_length /* necessary check on 32 bit systems */
      || chunk->chunk_length > chunk->total_length
      || chunk->offset + chunk->chunk_length > chunk->total_length
      || (chunk->offset != 0
          && chunk->total_length != pplayer->attribute_block_buffer.length)) {
    /* wrong attribute data */
    if (pplayer->attribute_block_buffer.data) {
      free(pplayer->attribute_block_buffer.data);
      pplayer->attribute_block_buffer.data = NULL;
    }
    pplayer->attribute_block_buffer.length = 0;
    log_error("Received wrong attribute chunk");
    return;
  }
  /* first one in a row */
  if (chunk->offset == 0) {
    if (pplayer->attribute_block_buffer.data) {
      free(pplayer->attribute_block_buffer.data);
      pplayer->attribute_block_buffer.data = NULL;
    }
    pplayer->attribute_block_buffer.data = fc_malloc(chunk->total_length);
    pplayer->attribute_block_buffer.length = chunk->total_length;
  }
  memcpy((char *) (pplayer->attribute_block_buffer.data) + chunk->offset,
         chunk->data, chunk->chunk_length);
  
  if (chunk->offset + chunk->chunk_length == chunk->total_length) {
    /* Received full attribute block */
    if (pplayer->attribute_block.data != NULL) {
      free(pplayer->attribute_block.data);
    }
    pplayer->attribute_block.data = pplayer->attribute_block_buffer.data;
    pplayer->attribute_block.length = pplayer->attribute_block_buffer.length;
    
    pplayer->attribute_block_buffer.data = NULL;
    pplayer->attribute_block_buffer.length = 0;
  }
}
 
/**********************************************************************/
void send_attribute_block(const struct player *pplayer,
                          struct connection *pconn)
{
  struct packet_player_attribute_chunk packet;
  int current_chunk, chunks, bytes_left;
 
  if (!pplayer || !pplayer->attribute_block.data) {
    return;
  }
 
  fc_assert_ret(pplayer->attribute_block.length > 0
                && pplayer->attribute_block.length < MAX_ATTRIBUTE_BLOCK);
 
  chunks =
      (pplayer->attribute_block.length - 1) / ATTRIBUTE_CHUNK_SIZE + 1;
  bytes_left = pplayer->attribute_block.length;
 
  connection_do_buffer(pconn);
 
  for (current_chunk = 0; current_chunk < chunks; current_chunk++) {
    int size_of_current_chunk = MIN(bytes_left, ATTRIBUTE_CHUNK_SIZE);
 
    packet.offset = ATTRIBUTE_CHUNK_SIZE * current_chunk;
    packet.total_length = pplayer->attribute_block.length;
    packet.chunk_length = size_of_current_chunk;
 
    memcpy(packet.data,
           (char *) (pplayer->attribute_block.data) + packet.offset,
           packet.chunk_length);
    bytes_left -= packet.chunk_length;
 
    if (packet.chunk_length < ATTRIBUTE_CHUNK_SIZE) {
      /* Last chunk is not full. Make sure that delta does
       * not use random data. */
      memset(packet.data + packet.chunk_length, 0,
             ATTRIBUTE_CHUNK_SIZE - packet.chunk_length);
    }
 
    send_packet_player_attribute_chunk(pconn, &packet);
  }
 
  connection_do_unbuffer(pconn);
}
 
/**********************************************************************/
void pre_send_packet_player_attribute_chunk(struct connection *pc,
                                            struct packet_player_attribute_chunk
                                            *packet)
{
  fc_assert(packet->total_length > 0
            && packet->total_length < MAX_ATTRIBUTE_BLOCK);
  /* 500 bytes header, just to be sure */
  fc_assert(packet->chunk_length > 0
            && packet->chunk_length < MAX_LEN_PACKET - 500);
  fc_assert(packet->chunk_length <= packet->total_length);
  fc_assert(packet->offset >= 0 && packet->offset < packet->total_length);
 
  log_packet("sending attribute chunk %d/%d %d",
             packet->offset, packet->total_length, packet->chunk_length);
}
 
/**********************************************************************/
static void packet_handlers_free(void)
{
  if (packet_handlers != NULL) {
    packet_handler_hash_destroy(packet_handlers);
    packet_handlers = NULL;
  }
}
 
/**********************************************************************/
const struct packet_handlers *packet_handlers_initial(void)
{
  static struct packet_handlers default_handlers;
  static bool initialized = FALSE;
 
  if (!initialized) {
    memset(&default_handlers, 0, sizeof(default_handlers));
    packet_handlers_fill_initial(&default_handlers);
    initialized = TRUE;
  }
 
  return &default_handlers;
}
 
/**********************************************************************/
const struct packet_handlers *packet_handlers_get(const char *capability)
{
  struct packet_handlers *phandlers;
  char functional_capability[MAX_LEN_CAPSTR] = "";
  char *tokens[MAX_LEN_CAPSTR / 2];
  char *functional_tokens[MAX_LEN_CAPSTR / 2];
  int tokens_num;
  int functional_tokens_num = 0;
  int i;
 
  fc_assert(strlen(capability) < sizeof(functional_capability));
 
  /* Get functional network capability string. */
  tokens_num = get_tokens(capability, tokens, ARRAY_SIZE(tokens), " \t\n,");
  for (i = 0; i < tokens_num; i++) {
    char *token;
 
    token = tokens[i];
    if (token[0] == '+') {
      token++;
    }
 
    if (has_capability(token, packet_functional_capability)) {
      functional_tokens[functional_tokens_num++] = token;
    }
  }
  qsort(functional_tokens, functional_tokens_num,
        sizeof(*functional_tokens), compare_strings_ptrs);
  for (i = 0; i < functional_tokens_num; i++) {
    if (functional_capability[0] != '\0') {
      sz_strlcat(functional_capability, " ");
    }
    sz_strlcat(functional_capability, functional_tokens[i]);
  }
  free_tokens(tokens, tokens_num);
 
  /* Ensure the hash table is created. */
  if (packet_handlers == NULL) {
    packet_handlers = packet_handler_hash_new();
  }
 
  /* Lookup handlers for the capabilities or create new handlers. */
  if (!packet_handler_hash_lookup(packet_handlers, functional_capability,
                                  &phandlers)) {
    phandlers = fc_malloc(sizeof(*phandlers));
    memcpy(phandlers, packet_handlers_initial(), sizeof(*phandlers));
    packet_handlers_fill_capability(phandlers, functional_capability);
    packet_handler_hash_insert(packet_handlers, functional_capability,
                               phandlers);
  }
 
  fc_assert(phandlers != NULL);
 
  return phandlers;
}
 
/**********************************************************************/
void packets_deinit(void)
{
  packet_handlers_free();
}