connection.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 <errno.h>
#include <string.h>
#include <time.h>
 
#ifdef FREECIV_HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#ifdef HAVE_SYS_SELECT_H
/* For some platforms this must be below sys/types.h. */
#include <sys/select.h>
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
 
/* utility */
#include "fcintl.h"
#include "genhash.h"
#include "log.h"
#include "mem.h"
#include "netintf.h"
#include "support.h"            /* fc_str(n)casecmp */
 
/* common */
#include "game.h"               /* game.all_connections */
#include "packets.h"
 
#include "connection.h"
 
 
static void default_conn_close_callback(struct connection *pconn);
 
/* String used for connection.addr and related cases to indicate
 * blank/unknown/not-applicable address:
 */
const char blank_addr_str[] = "---.---.---.---";
 
/****************************************************************************
  This callback is used when an error occurs trying to write to the
  connection. The effect of the callback should be to close the connection.
  This is here so that the server and client can take appropriate
  (different) actions: server lost a client, client lost connection to
  server. Never attempt to call this function directly, call
  connection_close() instead.
****************************************************************************/
static conn_close_fn_t conn_close_callback = default_conn_close_callback;
 
/************************************************************************/
static void default_conn_close_callback(struct connection *pconn)
{
  fc_assert_msg(conn_close_callback != default_conn_close_callback,
                "Closing a socket (%s) before calling "
                "close_socket_set_callback().", conn_description(pconn));
}
 
/**********************************************************************/
void connections_set_close_callback(conn_close_fn_t func)
{
  conn_close_callback = func;
}
 
/**********************************************************************/
void connection_close(struct connection *pconn, const char *reason)
{
  fc_assert_ret(pconn != nullptr);
 
  if (reason != nullptr && pconn->closing_reason == nullptr) {
    /* NB: We don't overwrite the original reason. */
    pconn->closing_reason = fc_strdup(reason);
  }
 
  (*conn_close_callback) (pconn);
}
 
/**********************************************************************/
static bool buffer_ensure_free_extra_space(struct socket_packet_buffer *buf,
                                           int extra_space)
{
  /* room for more? */
  if (buf->nsize - buf->ndata < extra_space) {
    buf->nsize = buf->ndata + extra_space;
 
    /* added this check so we don't gobble up too much mem */
    if (buf->nsize > MAX_LEN_BUFFER) {
      return FALSE;
    }
    buf->data = (unsigned char *) fc_realloc(buf->data, buf->nsize);
  }
 
  return TRUE;
}
 
/**********************************************************************/
int read_socket_data(int sock, struct socket_packet_buffer *buffer)
{
  int didget;
 
  if (!buffer_ensure_free_extra_space(buffer, MAX_LEN_PACKET)) {
    log_error("can't grow buffer");
    return -1;
  }
 
  log_debug("try reading %d bytes", buffer->nsize - buffer->ndata);
  didget = fc_readsocket(sock, (char *) (buffer->data + buffer->ndata),
                         buffer->nsize - buffer->ndata);
 
  if (didget > 0) {
    buffer->ndata += didget;
    log_debug("didget:%d", didget);
    return didget;
  } else if (didget == 0) {
    log_debug("EOF on socket read");
    return -2;
  }
 
#ifdef NONBLOCKING_SOCKETS
  else if (errno == EWOULDBLOCK || errno == EAGAIN) {
    log_debug("EGAIN on socket read");
    return 0;
  }
#endif /* NONBLOCKING_SOCKETS */
 
  return -1;
}
 
/**********************************************************************/
static int write_socket_data(struct connection *pc,
                             struct socket_packet_buffer *buf, int limit)
{
  int start, nput, nblock;
 
  if (is_server() && pc->server.is_closing) {
    return 0;
  }
 
  for (start = 0; buf->ndata-start > limit;) {
    fd_set writefs, exceptfs;
    fc_timeval tv;
 
    FC_FD_ZERO(&writefs);
    FC_FD_ZERO(&exceptfs);
    FD_SET(pc->sock, &writefs);
    FD_SET(pc->sock, &exceptfs);
 
    tv.tv_sec = 0; tv.tv_usec = 0;
 
    if (fc_select(pc->sock + 1, nullptr, &writefs, &exceptfs, &tv) <= 0) {
      if (errno != EINTR) {
        break;
      } else {
        /* EINTR can happen sometimes, especially when compiling with -pg.
         * Generally we just want to run select again. */
        continue;
      }
    }
 
    if (FD_ISSET(pc->sock, &exceptfs)) {
      connection_close(pc, _("network exception"));
      return -1;
    }
 
    if (FD_ISSET(pc->sock, &writefs)) {
      nblock = MIN(buf->ndata-start, MAX_LEN_PACKET);
      log_debug("trying to write %d limit=%d", nblock, limit);
      if ((nput = fc_writesocket(pc->sock,
                                 (const char *)buf->data+start, nblock)) == -1) {
#ifdef NONBLOCKING_SOCKETS
        if (errno == EWOULDBLOCK || errno == EAGAIN) {
          break;
        }
#endif /* NONBLOCKING_SOCKETS */
        connection_close(pc, _("lagging connection"));
        return -1;
      }
      start += nput;
    }
  }
 
  if (start > 0) {
    buf->ndata -= start;
    memmove(buf->data, buf->data+start, buf->ndata);
    pc->last_write = timer_renew(pc->last_write, TIMER_USER, TIMER_ACTIVE,
                                 pc->last_write != nullptr
                                 ? nullptr : "socket write");
    timer_start(pc->last_write);
  }
 
  return 0;
}
 
/**********************************************************************/
void flush_connection_send_buffer_all(struct connection *pc)
{
  if (pc && pc->used && pc->send_buffer->ndata > 0) {
    write_socket_data(pc, pc->send_buffer, 0);
    if (pc->notify_of_writable_data) {
      pc->notify_of_writable_data(pc, pc->send_buffer
                                  && pc->send_buffer->ndata > 0);
    }
  }
}
 
/**********************************************************************/
#ifndef FREECIV_JSON_CONNECTION
static void flush_connection_send_buffer_packets(struct connection *pc)
{
  if (pc && pc->used && pc->send_buffer->ndata >= MAX_LEN_PACKET) {
    write_socket_data(pc, pc->send_buffer, MAX_LEN_PACKET-1);
    if (pc->notify_of_writable_data) {
      pc->notify_of_writable_data(pc, pc->send_buffer
                                  && pc->send_buffer->ndata > 0);
    }
  }
}
#endif /* FREECIV_JSON_CONNECTION */
 
/**********************************************************************/
static bool add_connection_data(struct connection *pconn,
                                const unsigned char *data, int len)
{
  struct socket_packet_buffer *buf;
 
  if (pconn == nullptr
      || !pconn->used
      || (is_server() && pconn->server.is_closing)) {
    return TRUE;
  }
 
  buf = pconn->send_buffer;
  log_debug("add %d bytes to %d (space =%d)", len, buf->ndata, buf->nsize);
  if (!buffer_ensure_free_extra_space(buf, len)) {
    connection_close(pconn, _("buffer overflow"));
    return FALSE;
  }
 
  memcpy(buf->data + buf->ndata, data, len);
  buf->ndata += len;
 
  return TRUE;
}
 
/**********************************************************************/
bool connection_send_data(struct connection *pconn,
                          const unsigned char *data, int len)
{
  if (pconn == nullptr
      || !pconn->used
      || (is_server() && pconn->server.is_closing)) {
    return TRUE;
  }
 
  pconn->statistics.bytes_send += len;
 
#ifndef FREECIV_JSON_CONNECTION
  if (0 < pconn->send_buffer->do_buffer_sends) {
    flush_connection_send_buffer_packets(pconn);
    if (!add_connection_data(pconn, data, len)) {
      log_verbose("cut connection %s due to huge send buffer (1)",
                  conn_description(pconn));
      return FALSE;
    }
    flush_connection_send_buffer_packets(pconn);
  } else
#endif /* FREECIV_JSON_CONNECTION */
  {
    flush_connection_send_buffer_all(pconn);
    if (!add_connection_data(pconn, data, len)) {
      log_verbose("cut connection %s due to huge send buffer (2)",
                  conn_description(pconn));
      return FALSE;
    }
    flush_connection_send_buffer_all(pconn);
  }
  return TRUE;
}
 
/**********************************************************************/
void connection_do_buffer(struct connection *pc)
{
  if (pc && pc->used) {
    pc->send_buffer->do_buffer_sends++;
  }
}
 
/**********************************************************************/
void connection_do_unbuffer(struct connection *pc)
{
  if (pc == nullptr || !pc->used
      || (is_server() && pc->server.is_closing)) {
    return;
  }
 
  pc->send_buffer->do_buffer_sends--;
  if (0 > pc->send_buffer->do_buffer_sends) {
    log_error("Too many calls to unbuffer %s!", pc->username);
    pc->send_buffer->do_buffer_sends = 0;
  }
 
  if (0 == pc->send_buffer->do_buffer_sends) {
    flush_connection_send_buffer_all(pc);
  }
}
 
/**********************************************************************/
void conn_list_do_buffer(struct conn_list *dest)
{
  conn_list_iterate(dest, pconn) {
    connection_do_buffer(pconn);
  } conn_list_iterate_end;
}
 
/**********************************************************************/
void conn_list_do_unbuffer(struct conn_list *dest)
{
  conn_list_iterate(dest, pconn) {
    connection_do_unbuffer(pconn);
  } conn_list_iterate_end;
}
 
/**********************************************************************/
struct connection *conn_by_user(const char *user_name)
{
  conn_list_iterate(game.all_connections, pconn) {
    if (fc_strcasecmp(user_name, pconn->username) == 0) {
      return pconn;
    }
  } conn_list_iterate_end;
 
  return nullptr;
}
 
/**********************************************************************/
static const char *connection_accessor(int i) {
  return conn_list_get(game.all_connections, i)->username;
}
 
struct connection *conn_by_user_prefix(const char *user_name,
                                       enum m_pre_result *result)
{
  int ind;
 
  *result = match_prefix(connection_accessor,
                         conn_list_size(game.all_connections),
                         MAX_LEN_NAME-1, fc_strncasequotecmp,
                         effectivestrlenquote, user_name, &ind);
 
  if (*result < M_PRE_AMBIGUOUS) {
    return conn_list_get(game.all_connections, ind);
  } else {
    return nullptr;
  }
}
 
/**********************************************************************/
struct connection *conn_by_number(int id)
{
  conn_list_iterate(game.all_connections, pconn) {
    fc_assert_msg(pconn != nullptr,
                  "Trying to look at the id of a non existing connection");
 
    if (pconn->id == id) {
      return pconn;
    }
  }
  conn_list_iterate_end;
 
  return nullptr;
}
 
/**********************************************************************/
struct socket_packet_buffer *new_socket_packet_buffer(void)
{
  struct socket_packet_buffer *buf;
 
  buf = fc_malloc(sizeof(*buf));
  buf->ndata = 0;
  buf->do_buffer_sends = 0;
  buf->nsize = 10*MAX_LEN_PACKET;
  buf->data = (unsigned char *)fc_malloc(buf->nsize);
 
  return buf;
}
 
/**********************************************************************/
static void free_socket_packet_buffer(struct socket_packet_buffer *buf)
{
  if (buf) {
    if (buf->data) {
      free(buf->data);
    }
    free(buf);
  }
}
 
/**********************************************************************/
const char *conn_description(const struct connection *pconn)
{
  static char buffer[MAX_LEN_NAME*2 + MAX_LEN_ADDR + 128];
 
  buffer[0] = '\0';
 
  if (*pconn->username != '\0') {
    fc_snprintf(buffer, sizeof(buffer), _("%s from %s"),
                pconn->username, pconn->addr);
  } else {
    sz_strlcpy(buffer, "server");
  }
  if (pconn->closing_reason != nullptr) {
    /* TRANS: Appending the reason why a connection has closed.
     * Preserve leading space. */
    cat_snprintf(buffer, sizeof(buffer), _(" (%s)"), pconn->closing_reason);
  } else if (!pconn->established) {
    /* TRANS: Preserve leading space. */
    sz_strlcat(buffer, _(" (connection incomplete)"));
    return buffer;
  }
  if (pconn->playing != nullptr) {
    /* TRANS: Preserve leading space. */
    cat_snprintf(buffer, sizeof(buffer), _(" (player %s)"),
                 player_name(pconn->playing));
  }
  if (pconn->observer) {
    /* TRANS: Preserve leading space. */
    sz_strlcat(buffer, _(" (observer)"));
  }
 
  return buffer;
}
 
/**********************************************************************/
bool can_conn_edit(const struct connection *pconn)
{
  return (can_conn_enable_editing(pconn)
          && game.info.is_edit_mode
          && (pconn->playing != nullptr || pconn->observer));
}
 
/**********************************************************************/
bool can_conn_enable_editing(const struct connection *pconn)
{
  return pconn->access_level == ALLOW_HACK;
}
 
/**********************************************************************/
int get_next_request_id(int old_request_id)
{
  int result = old_request_id + 1;
 
  if ((result & 0xffff) == 0) {
    log_packet("INFORMATION: request_id has wrapped around; "
               "setting from %d to 2", result);
    result = 2;
  }
  fc_assert(0 != result);
 
  return result;
}
 
/**********************************************************************/
void free_compression_queue(struct connection *pc)
{
#ifdef USE_COMPRESSION
  byte_vector_free(&pc->compression.queue);
#endif /* USE_COMPRESSION */
}
 
/**********************************************************************/
static void init_packet_hashes(struct connection *pc)
{
  enum packet_type i;
 
  pc->phs.sent = fc_malloc(sizeof(*pc->phs.sent) * PACKET_LAST);
  pc->phs.received = fc_malloc(sizeof(*pc->phs.received) * PACKET_LAST);
  pc->phs.handlers = packet_handlers_initial();
 
  for (i = 0; i < PACKET_LAST; i++) {
    pc->phs.sent[i] = nullptr;
    pc->phs.received[i] = nullptr;
  }
}
 
/**********************************************************************/
static void free_packet_hashes(struct connection *pc)
{
  int i;
 
  if (pc->phs.sent) {
    for (i = 0; i < PACKET_LAST; i++) {
      if (pc->phs.sent[i] != nullptr) {
        genhash_destroy(pc->phs.sent[i]);
      }
    }
    free(pc->phs.sent);
    pc->phs.sent = nullptr;
  }
 
  if (pc->phs.received) {
    for (i = 0; i < PACKET_LAST; i++) {
      if (pc->phs.received[i] != nullptr) {
        genhash_destroy(pc->phs.received[i]);
      }
    }
    free(pc->phs.received);
    pc->phs.received = nullptr;
  }
}
 
/**********************************************************************/
void connection_common_init(struct connection *pconn)
{
  pconn->established = FALSE;
  pconn->used = TRUE;
  packet_header_init(&pconn->packet_header);
  pconn->closing_reason = nullptr;
  pconn->last_write = nullptr;
  pconn->buffer = new_socket_packet_buffer();
  pconn->send_buffer = new_socket_packet_buffer();
  pconn->statistics.bytes_send = 0;
#ifdef FREECIV_JSON_CONNECTION
  pconn->json_mode = TRUE;
#endif /* FREECIV_JSON_CONNECTION */
 
  init_packet_hashes(pconn);
 
#ifdef USE_COMPRESSION
  byte_vector_init(&pconn->compression.queue);
  pconn->compression.frozen_level = 0;
#endif /* USE_COMPRESSION */
 
  pconn->client_gui = GUI_STUB;
}
 
/**********************************************************************/
void connection_common_close(struct connection *pconn)
{
  if (!pconn->used) {
    log_error("WARNING: Trying to close already closed connection");
  } else {
    fc_closesocket(pconn->sock);
    pconn->used = FALSE;
    pconn->established = FALSE;
    if (pconn->closing_reason != nullptr) {
      free(pconn->closing_reason);
    }
 
    free_socket_packet_buffer(pconn->buffer);
    pconn->buffer = nullptr;
 
    free_socket_packet_buffer(pconn->send_buffer);
    pconn->send_buffer = nullptr;
 
    if (pconn->last_write) {
      timer_destroy(pconn->last_write);
      pconn->last_write = nullptr;
    }
 
    free_compression_queue(pconn);
    free_packet_hashes(pconn);
  }
}
 
/**********************************************************************/
void conn_set_capability(struct connection *pconn, const char *capability)
{
  fc_assert(strlen(capability) < sizeof(pconn->capability));
 
  sz_strlcpy(pconn->capability, capability);
  pconn->phs.handlers = packet_handlers_get(capability);
}
 
/**********************************************************************/
void conn_reset_delta_state(struct connection *pc)
{
  int i;
 
  for (i = 0; i < PACKET_LAST; i++) {
    if (packet_has_game_info_flag(i)) {
      if (pc->phs.sent != nullptr && pc->phs.sent[i] != nullptr) {
        genhash_clear(pc->phs.sent[i]);
      }
      if (pc->phs.received != nullptr && pc->phs.received[i] != nullptr) {
        genhash_clear(pc->phs.received[i]);
      }
    }
  }
}
 
/**********************************************************************/
void conn_compression_freeze(struct connection *pconn)
{
#ifdef USE_COMPRESSION
  if (0 == pconn->compression.frozen_level) {
    byte_vector_reserve(&pconn->compression.queue, 0);
  }
  pconn->compression.frozen_level++;
#endif /* USE_COMPRESSION */
}
 
/**********************************************************************/
bool conn_compression_frozen(const struct connection *pconn)
{
#ifdef USE_COMPRESSION
  return 0 < pconn->compression.frozen_level;
#else  /* USE_COMPRESSION */
  return FALSE;
#endif /* USE_COMPRESSION */
}
 
/**********************************************************************/
void conn_list_compression_freeze(const struct conn_list *pconn_list)
{
#ifdef USE_COMPRESSION
  conn_list_iterate(pconn_list, pconn) {
    conn_compression_freeze(pconn);
  } conn_list_iterate_end;
#endif /* USE_COMPRESSION */
}
 
/**********************************************************************/
void conn_list_compression_thaw(const struct conn_list *pconn_list)
{
#ifdef USE_COMPRESSION
  conn_list_iterate(pconn_list, pconn) {
    conn_compression_thaw(pconn);
  } conn_list_iterate_end;
#endif /* USE_COMPRESSION */
}
 
/**********************************************************************/
bool conn_controls_player(const struct connection *pconn)
{
  return pconn && pconn->playing && !pconn->observer;
}
 
/**********************************************************************/
bool conn_is_global_observer(const struct connection *pconn)
{
  return pconn && !pconn->playing && pconn->observer;
}
 
/**********************************************************************/
struct player *conn_get_player(const struct connection *pconn)
{
  if (pconn == nullptr) {
    return nullptr;
  }
 
  return pconn->playing;
}
 
/**********************************************************************/
enum cmdlevel conn_get_access(const struct connection *pconn)
{
  if (pconn == nullptr) {
    return ALLOW_NONE; /* Would not want to give hack on error... */
  }
 
  return pconn->access_level;
}
 
 
/**************************************************************************
  Connection patterns.
**************************************************************************/
struct conn_pattern {
  enum conn_pattern_type type;
  char *wildcard;
};
 
/**********************************************************************/
struct conn_pattern *conn_pattern_new(enum conn_pattern_type type,
                                      const char *wildcard)
{
  struct conn_pattern *ppattern = fc_malloc(sizeof(*ppattern));
 
  ppattern->type = type;
  ppattern->wildcard = fc_strdup(wildcard);
 
  return ppattern;
}
 
/**********************************************************************/
void conn_pattern_destroy(struct conn_pattern *ppattern)
{
  fc_assert_ret(ppattern != nullptr);
  free(ppattern->wildcard);
  free(ppattern);
}
 
/**********************************************************************/
bool conn_pattern_match(const struct conn_pattern *ppattern,
                        const struct connection *pconn)
{
  const char *test = nullptr;
 
  switch (ppattern->type) {
  case CPT_USER:
    test = pconn->username;
    break;
  case CPT_HOST:
    test =  pconn->addr;
    break;
  case CPT_IP:
    if (is_server()) {
      test = pconn->server.ipaddr;
    }
    break;
  }
 
  if (test != nullptr) {
    return wildcard_fit_string(ppattern->wildcard, test);
  } else {
    log_error("%s(): Invalid pattern type (%d)",
              __FUNCTION__, ppattern->type);
    return FALSE;
  }
}
 
/**********************************************************************/
bool conn_pattern_list_match(const struct conn_pattern_list *plist,
                             const struct connection *pconn)
{
  conn_pattern_list_iterate(plist, ppattern) {
    if (conn_pattern_match(ppattern, pconn)) {
      return TRUE;
    }
  } conn_pattern_list_iterate_end;
 
  return FALSE;
}
 
/**********************************************************************/
size_t conn_pattern_to_string(const struct conn_pattern *ppattern,
                              char *buf, size_t buf_len)
{
  return fc_snprintf(buf, buf_len, "<%s=%s>",
                     conn_pattern_type_name(ppattern->type),
                     ppattern->wildcard);
}
 
/**********************************************************************/
struct conn_pattern *conn_pattern_from_string(const char *pattern,
                                              enum conn_pattern_type prefer,
                                              char *error_buf,
                                              size_t error_buf_len)
{
  enum conn_pattern_type type;
  const char *p;
 
  /* Determine pattern type. */
  if ((p = strchr(pattern, '='))) {
    /* Special character to separate the type of the pattern. */
    const size_t pattern_type_len = ++p - pattern;
    char pattern_type[pattern_type_len];
 
    fc_strlcpy(pattern_type, pattern, pattern_type_len);
    remove_leading_trailing_spaces(pattern_type);
    type = conn_pattern_type_by_name(pattern_type, fc_strcasecmp);
    if (!conn_pattern_type_is_valid(type)) {
      if (error_buf != nullptr) {
        fc_snprintf(error_buf, error_buf_len,
                    _("\"%s\" is not a valid pattern type"),
                    pattern_type);
      }
 
      return nullptr;
    }
  } else {
    /* Use 'prefer' type. */
    p = pattern;
    type = prefer;
    if (!conn_pattern_type_is_valid(type)) {
      if (error_buf != nullptr) {
        fc_strlcpy(error_buf, _("Missing pattern type"), error_buf_len);
      }
 
      return nullptr;
    }
  }
 
  /* Remove leading spaces. */
  while (fc_isspace(*p)) {
    p++;
  }
 
  if ('\0' == *p) {
    if (error_buf != nullptr) {
      fc_strlcpy(error_buf, _("Missing pattern"), error_buf_len);
    }
 
    return nullptr;
  }
 
  return conn_pattern_new(type, p);
}
 
/**********************************************************************/
bool conn_is_valid(const struct connection *pconn)
{
  return (pconn != nullptr && pconn->used && !pconn->server.is_closing);
}