/*
     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 */
