/*
     This file is part of GNUnet.
     Copyright (C) 2010-2015, 2018 GNUnet e.V.

     GNUnet is free software: you can redistribute it and/or modify it
     under the terms of the GNU Affero General Public License as published
     by the Free Software Foundation, either version 3 of the License,
     or (at your option) any later version.

     GNUnet 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
     Affero General Public License for more details.

     You should have received a copy of the GNU Affero General Public License
     along with this program.  If not, see <http://www.gnu.org/licenses/>.

     SPDX-License-Identifier: AGPL3.0-or-later
 */
/**
 * @file nt/nt_api_scanner.c
 * @brief LAN interface scanning to determine IPs in LAN
 * @author Christian Grothoff
 * @author Matthias Wachs
 */
#include "platform.h"
#include "gnunet_util_lib.h"
#include "gnunet_nt_lib.h"

/**
 * How frequently do we scan the interfaces for changes to the addresses?
 */
#define INTERFACE_PROCESSING_INTERVAL GNUNET_TIME_relative_multiply(GNUNET_TIME_UNIT_MINUTES, 2)


/**
 * Convert a `enum GNUNET_NetworkType` to a string
 *
 * @param net the network type
 * @return a string or NULL if invalid
 */
const char *
GNUNET_NT_to_string(enum GNUNET_NetworkType net)
{
  switch (net)
    {
    case GNUNET_NT_UNSPECIFIED:
      return "UNSPECIFIED";

    case GNUNET_NT_LOOPBACK:
      return "LOOPBACK";

    case GNUNET_NT_LAN:
      return "LAN";

    case GNUNET_NT_WAN:
      return "WAN";

    case GNUNET_NT_WLAN:
      return "WLAN";

    case GNUNET_NT_BT:
      return "BLUETOOTH";

    default:
      return NULL;
    }
}


/**
 * We keep a list of our local networks so we can answer
 * LAN vs. WAN questions.  Note: WLAN is not detected yet.
 * (maybe we can do that heuristically based on interface
 * name in the future?).
 */
struct NT_Network {
  /**
   * Kept in a DLL.
   */
  struct NT_Network *next;

  /**
   * Kept in a DLL.
   */
  struct NT_Network *prev;

  /**
   * Network address.
   */
  struct sockaddr *network;

  /**
   * Netmask to determine what is in the LAN.
   */
  struct sockaddr *netmask;

  /**
   * How long are @e network and @e netmask?
   */
  socklen_t length;
};


/**
 * Handle to the interface scanner.
 */
struct GNUNET_NT_InterfaceScanner {
  /**
   * Head of LAN networks list.
   */
  struct NT_Network *net_head;

  /**
   * Tail of LAN networks list.
   */
  struct NT_Network *net_tail;

  /**
   * Task for periodically refreshing our LAN network list.
   */
  struct GNUNET_SCHEDULER_Task *interface_task;
};


/**
 * Delete all entries from the current network list.
 *
 * @param is scanner to clean up
 */
static void
delete_networks(struct GNUNET_NT_InterfaceScanner *is)
{
  struct NT_Network *cur;

  while (NULL != (cur = is->net_head))
    {
      GNUNET_CONTAINER_DLL_remove(is->net_head,
                                  is->net_tail,
                                  cur);
      GNUNET_free(cur);
    }
}


/**
 * Function invoked for each interface found.  Adds the interface's
 * network addresses to the respective DLL, so we can distinguish
 * between LAN and WAN.
 *
 * @param cls closure with the `struct GNUNET_NT_InterfaceScanner`
 * @param name name of the interface (can be NULL for unknown)
 * @param isDefault is this presumably the default interface
 * @param addr address of this interface (can be NULL for unknown or unassigned)
 * @param broadcast_addr the broadcast address (can be NULL for unknown or unassigned)
 * @param netmask the network mask (can be NULL for unknown or unassigned)
 * @param addrlen length of the address
 * @return #GNUNET_OK to continue iteration
 */
static int
interface_proc(void *cls,
               const char *name,
               int isDefault,
               const struct sockaddr *addr,
               const struct sockaddr *broadcast_addr,
               const struct sockaddr *netmask,
               socklen_t addrlen)
{
  struct GNUNET_NT_InterfaceScanner *is = cls;
  /* Calculate network */
  struct NT_Network *net = NULL;

  (void)name;
  (void)isDefault;
  (void)broadcast_addr;

  /* Skipping IPv4 loopback addresses since we have special check  */
  if (addr->sa_family == AF_INET)
    {
      const struct sockaddr_in *a4 = (const struct sockaddr_in *)addr;

      if ((a4->sin_addr.s_addr & htonl(0xff000000)) == htonl(0x7f000000))
        return GNUNET_OK;
    }
  /* Skipping IPv6 loopback addresses since we have special check  */
  if (addr->sa_family == AF_INET6)
    {
      const struct sockaddr_in6 *a6 = (const struct sockaddr_in6 *)addr;
      if (IN6_IS_ADDR_LOOPBACK(&a6->sin6_addr))
        return GNUNET_OK;
    }

  if (addr->sa_family == AF_INET)
    {
      const struct sockaddr_in *addr4 = (const struct sockaddr_in *)addr;
      const struct sockaddr_in *netmask4 = (const struct sockaddr_in *)netmask;
      struct sockaddr_in *tmp;
      struct sockaddr_in network4;

      net = GNUNET_malloc(sizeof(struct NT_Network) + 2 * sizeof(struct sockaddr_in));
      tmp = (struct sockaddr_in *)&net[1];
      net->network = (struct sockaddr *)&tmp[0];
      net->netmask = (struct sockaddr *)&tmp[1];
      net->length = addrlen;

      memset(&network4,
             0,
             sizeof(network4));
      network4.sin_family = AF_INET;
#if HAVE_SOCKADDR_IN_SIN_LEN
      network4.sin_len = sizeof(network4);
#endif
      network4.sin_addr.s_addr = (addr4->sin_addr.s_addr & netmask4->sin_addr.s_addr);

      GNUNET_memcpy(net->netmask,
                    netmask4,
                    sizeof(struct sockaddr_in));
      GNUNET_memcpy(net->network,
                    &network4,
                    sizeof(struct sockaddr_in));
    }

  if (addr->sa_family == AF_INET6)
    {
      const struct sockaddr_in6 *addr6 = (const struct sockaddr_in6 *)addr;
      const struct sockaddr_in6 *netmask6 = (const struct sockaddr_in6 *)netmask;
      struct sockaddr_in6 * tmp;
      struct sockaddr_in6 network6;

      net = GNUNET_malloc(sizeof(struct NT_Network) + 2 * sizeof(struct sockaddr_in6));
      tmp = (struct sockaddr_in6 *)&net[1];
      net->network = (struct sockaddr *)&tmp[0];
      net->netmask = (struct sockaddr *)&tmp[1];
      net->length = addrlen;

      memset(&network6, 0, sizeof(network6));
      network6.sin6_family = AF_INET6;
#if HAVE_SOCKADDR_IN_SIN_LEN
      network6.sin6_len = sizeof(network6);
#endif
      unsigned int c = 0;
      uint32_t *addr_elem = (uint32_t *)&addr6->sin6_addr;
      uint32_t *mask_elem = (uint32_t *)&netmask6->sin6_addr;
      uint32_t *net_elem = (uint32_t *)&network6.sin6_addr;
      for (c = 0; c < 4; c++)
        net_elem[c] = addr_elem[c] & mask_elem[c];

      GNUNET_memcpy(net->netmask,
                    netmask6,
                    sizeof(struct sockaddr_in6));
      GNUNET_memcpy(net->network,
                    &network6,
                    sizeof(struct sockaddr_in6));
    }
  if (NULL == net)
    return GNUNET_OK; /* odd / unsupported address family */

  /* Store in list */
#if VERBOSE_NT
  char * netmask = GNUNET_strdup(GNUNET_a2s((struct sockaddr *)net->netmask, addrlen));
  GNUNET_log_from(GNUNET_ERROR_TYPE_DEBUG,
                  "nt",
                  "Adding network `%s', netmask `%s'\n",
                  GNUNET_a2s((struct sockaddr *)net->network,
                             addrlen),
                  netmask);
  GNUNET_free(netmask);
#endif
  GNUNET_CONTAINER_DLL_insert(is->net_head,
                              is->net_tail,
                              net);

  return GNUNET_OK;
}


/**
 * Periodically get list of network addresses from our interfaces.
 *
 * @param cls closure
 */
static void
get_addresses(void *cls)
{
  struct GNUNET_NT_InterfaceScanner *is = cls;

  is->interface_task = NULL;
  delete_networks(is);
  GNUNET_OS_network_interfaces_list(&interface_proc,
                                    is);
  is->interface_task = GNUNET_SCHEDULER_add_delayed(INTERFACE_PROCESSING_INTERVAL,
                                                    &get_addresses,
                                                    is);
}


/**
 * Returns where the address is located: LAN or WAN or ...
 *
 * @param is the interface scanner handle
 * @param addr address
 * @param addrlen address length
 * @return type of the network the address belongs to
 */
enum GNUNET_NetworkType
GNUNET_NT_scanner_get_type(struct GNUNET_NT_InterfaceScanner *is,
                           const struct sockaddr *addr,
                           socklen_t addrlen)
{
  struct NT_Network *cur = is->net_head;
  enum GNUNET_NetworkType type = GNUNET_NT_UNSPECIFIED;

  switch (addr->sa_family)
    {
    case AF_UNIX:
      type = GNUNET_NT_LOOPBACK;
      break;

    case AF_INET:
    {
      const struct sockaddr_in *a4 = (const struct sockaddr_in *)addr;

      if ((a4->sin_addr.s_addr & htonl(0xff000000)) == htonl(0x7f000000))
        type = GNUNET_NT_LOOPBACK;
      break;
    }

    case AF_INET6:
    {
      const struct sockaddr_in6 *a6 = (const struct sockaddr_in6 *)addr;

      if (IN6_IS_ADDR_LOOPBACK(&a6->sin6_addr))
        type = GNUNET_NT_LOOPBACK;
      break;
    }

    default:
      GNUNET_break(0);
      break;
    }

  /* Check local networks */
  while ((NULL != cur) && (GNUNET_NT_UNSPECIFIED == type))
    {
      if (addrlen != cur->length)
        {
          cur = cur->next;
          continue;
        }
      if (addr->sa_family == AF_INET)
        {
          const struct sockaddr_in *a4 = (const struct sockaddr_in *)addr;
          const struct sockaddr_in *net4 = (const struct sockaddr_in *)cur->network;
          const struct sockaddr_in *mask4 = (const struct sockaddr_in *)cur->netmask;

          if (((a4->sin_addr.s_addr & mask4->sin_addr.s_addr)) == net4->sin_addr.s_addr)
            type = GNUNET_NT_LAN;
        }
      if (addr->sa_family == AF_INET6)
        {
          const struct sockaddr_in6 *a6 = (const struct sockaddr_in6 *)addr;
          const struct sockaddr_in6 *net6 = (const struct sockaddr_in6 *)cur->network;
          const struct sockaddr_in6 *mask6 = (const struct sockaddr_in6 *)cur->netmask;

          int res = GNUNET_YES;
          int c = 0;
          uint32_t *addr_elem = (uint32_t *)&a6->sin6_addr;
          uint32_t *mask_elem = (uint32_t *)&mask6->sin6_addr;
          uint32_t *net_elem = (uint32_t *)&net6->sin6_addr;
          for (c = 0; c < 4; c++)
            if ((addr_elem[c] & mask_elem[c]) != net_elem[c])
              res = GNUNET_NO;

          if (res == GNUNET_YES)
            type = GNUNET_NT_LAN;
        }
      cur = cur->next;
    }

  /* no local network found for this address, default: WAN */
  if (type == GNUNET_NT_UNSPECIFIED)
    type = GNUNET_NT_WAN;
  GNUNET_log_from(GNUNET_ERROR_TYPE_DEBUG,
                  "nt-scanner-api",
                  "`%s' is in network `%s'\n",
                  GNUNET_a2s(addr,
                             addrlen),
                  GNUNET_NT_to_string(type));
  return type;
}


/**
 * Initialize the interface scanner.
 *
 * @return interface scanner
 */
struct GNUNET_NT_InterfaceScanner *
GNUNET_NT_scanner_init()
{
  struct GNUNET_NT_InterfaceScanner *is;

  is = GNUNET_new(struct GNUNET_NT_InterfaceScanner);
  GNUNET_OS_network_interfaces_list(&interface_proc,
                                    is);
  is->interface_task = GNUNET_SCHEDULER_add_delayed(INTERFACE_PROCESSING_INTERVAL,
                                                    &get_addresses,
                                                    is);
  return is;
}


/**
 * Client is done with the interface scanner, release resources.
 *
 * @param is handle to release
 */
void
GNUNET_NT_scanner_done(struct GNUNET_NT_InterfaceScanner *is)
{
  if (NULL != is->interface_task)
    {
      GNUNET_SCHEDULER_cancel(is->interface_task);
      is->interface_task = NULL;
    }
  delete_networks(is);
  GNUNET_free(is);
}


/* end of nt.c */