/*
   * Copyright (C) 2015 Ludwig Knüpfer <ludwig.knuepfer@fu-berlin.de>,
   *                    Martine Lenders <mlenders@inf.fu-berlin.de>
   *                    Kaspar Schleiser <kaspar@schleiser.de>
   *                    Ell-i open source co-operative
   *
   * This file is subject to the terms and conditions of the GNU Lesser General
   * Public License v2.1. See the file LICENSE in the top level directory for
   * more details.
   */
  
  /*
   * @ingroup netdev
   * @{
   * @brief   Low-level ethernet driver for tap interfaces
   * @author  Kaspar Schleiser <kaspar@schleiser.de>
   * @}
   */
  #include <assert.h>
  #include <err.h>
  #include <errno.h>
  #include <fcntl.h>
  #include <inttypes.h>
  #include <stdio.h>
  #include <stdint.h>
  #include <stdlib.h>
  #include <string.h>
  #include <sys/ioctl.h>
  #include <unistd.h>
  
  /* needs to be included before native's declarations of ntohl etc. */
  #include "byteorder.h"
  
  #ifdef __MACH__
  #include <net/if.h>
  #include <sys/types.h>
  #include <ifaddrs.h>
  #include <net/if_dl.h>
  #elif defined(__FreeBSD__)
  #include <sys/socket.h>
  #include <net/if.h>
  #include <ifaddrs.h>
  #include <net/if_dl.h>
  #else
  #include <net/if.h>
  #include <linux/if_tun.h>
  #include <linux/if_ether.h>
  #endif
  
  #include "native_internal.h"
  
  #include "async_read.h"
  
  #include "net/eui64.h"
  #include "net/netdev.h"
  #include "net/netdev/eth.h"
  #include "net/ethernet.h"
  #include "net/ethernet/hdr.h"
  #include "netdev_tap.h"
  #include "net/netopt.h"
  
  #define ENABLE_DEBUG (0)
  #include "debug.h"
  
  /* netdev interface */
  static int _init(netdev_t *netdev);
  static int _send(netdev_t *netdev, const struct iovec *vector, unsigned n);
  static int _recv(netdev_t *netdev, void *buf, size_t n, void *info);
  
  static inline void _get_mac_addr(netdev_t *netdev, uint8_t *dst)
  {
      netdev_tap_t *dev = (netdev_tap_t*)netdev;
      memcpy(dst, dev->addr, ETHERNET_ADDR_LEN);
  }
  
  static inline void _set_mac_addr(netdev_t *netdev, const uint8_t *src)
  {
      netdev_tap_t *dev = (netdev_tap_t*)netdev;
      memcpy(dev->addr, src, ETHERNET_ADDR_LEN);
  }
  
  static inline int _get_promiscous(netdev_t *netdev)
  {
      netdev_tap_t *dev = (netdev_tap_t*)netdev;
      return dev->promiscous;
  }
  
  static inline int _set_promiscous(netdev_t *netdev, int value)
  {
      netdev_tap_t *dev = (netdev_tap_t*)netdev;
      dev->promiscous = value;
      return value;
  }
  
  static inline void _isr(netdev_t *netdev)
  {
      if (netdev->event_callback) {
          netdev->event_callback(netdev, NETDEV_EVENT_RX_COMPLETE);
      }
  #if DEVELHELP
      else {
          puts("netdev_tap: _isr(): no event_callback set.");
      }
  #endif
  }
  
  static int _get(netdev_t *dev, netopt_t opt, void *value, size_t max_len)
  {
      int res = 0;
  
      switch (opt) {
          case NETOPT_ADDRESS:
              if (max_len < ETHERNET_ADDR_LEN) {
                  res = -EINVAL;
              }
              else {
                  _get_mac_addr(dev, (uint8_t*)value);
                  res = ETHERNET_ADDR_LEN;
              }
              break;
          case NETOPT_PROMISCUOUSMODE:
              *((bool*)value) = (bool)_get_promiscous(dev);
              res = sizeof(bool);
              break;
          default:
              res = netdev_eth_get(dev, opt, value, max_len);
              break;
      }
  
      return res;
  }
  
  static int _set(netdev_t *dev, netopt_t opt, const void *value, size_t value_len)
  {
      (void)value_len;
      int res = 0;
  
      switch (opt) {
          case NETOPT_ADDRESS:
              assert(value_len >= ETHERNET_ADDR_LEN);
              _set_mac_addr(dev, (const uint8_t*)value);
              break;
          case NETOPT_PROMISCUOUSMODE:
              _set_promiscous(dev, ((const bool *)value)[0]);
              break;
          default:
              res = netdev_eth_set(dev, opt, value, value_len);
              break;
      }
  
      return res;
  }
  
  static netdev_driver_t netdev_driver_tap = {
      .send = _send,
      .recv = _recv,
      .init = _init,
      .isr = _isr,
      .get = _get,
      .set = _set,
  };
  
  /* driver implementation */
  static inline bool _is_addr_broadcast(uint8_t *addr)
  {
      return ((addr[0] == 0xff) && (addr[1] == 0xff) && (addr[2] == 0xff) &&
              (addr[3] == 0xff) && (addr[4] == 0xff) && (addr[5] == 0xff));
  }
  
  static inline bool _is_addr_multicast(uint8_t *addr)
  {
      /* source: http://ieee802.org/secmail/pdfocSP2xXA6d.pdf */
      return (addr[0] & 0x01);
  }
  
  static void _continue_reading(netdev_tap_t *dev)
  {
      /* work around lost signals */
      fd_set rfds;
      struct timeval t;
      memset(&t, 0, sizeof(t));
      FD_ZERO(&rfds);
      FD_SET(dev->tap_fd, &rfds);
  
      _native_in_syscall++; /* no switching here */
  
      if (real_select(dev->tap_fd + 1, &rfds, NULL, NULL, &t) == 1) {
          int sig = SIGIO;
          extern int _sig_pipefd[2];
          extern ssize_t (*real_write)(int fd, const void * buf, size_t count);
          real_write(_sig_pipefd[1], &sig, sizeof(int));
          _native_sigpend++;
          DEBUG("netdev_tap: sigpend++\n");
      }
      else {
          DEBUG("netdev_tap: native_async_read_continue\n");
          native_async_read_continue(dev->tap_fd);
      }
  
      _native_in_syscall--;
  }
  
  static int _recv(netdev_t *netdev, void *buf, size_t len, void *info)
  {
      netdev_tap_t *dev = (netdev_tap_t*)netdev;
      (void)info;
  
      if (!buf) {
          if (len > 0) {
              /* no memory available in pktbuf, discarding the frame */
              DEBUG("netdev_tap: discarding the frame\n");
  
              /* repeating `real_read` for small size on tap device results in
               * freeze for some reason. Using a large buffer for now. */
              /*
              uint8_t buf[4];
              while (real_read(dev->tap_fd, buf, sizeof(buf)) > 0) {
              }
              */
  
              static uint8_t buf[ETHERNET_FRAME_LEN];
  
              real_read(dev->tap_fd, buf, sizeof(buf));
  
              _continue_reading(dev);
          }
  
          /* no way of figuring out packet size without racey buffering,
           * so we return the maximum possible size */
          return ETHERNET_FRAME_LEN;
      }
  
      int nread = real_read(dev->tap_fd, buf, len);
      DEBUG("netdev_tap: read %d bytes\n", nread);
  
      if (nread > 0) {
          ethernet_hdr_t *hdr = (ethernet_hdr_t *)buf;
          if (!(dev->promiscous) && !_is_addr_multicast(hdr->dst) &&
              !_is_addr_broadcast(hdr->dst) &&
              (memcmp(hdr->dst, dev->addr, ETHERNET_ADDR_LEN) != 0)) {
              DEBUG("netdev_tap: received for %02x:%02x:%02x:%02x:%02x:%02x\n"
                    "That's not me => Dropped\n",
                    hdr->dst[0], hdr->dst[1], hdr->dst[2],
                    hdr->dst[3], hdr->dst[4], hdr->dst[5]);
  
              native_async_read_continue(dev->tap_fd);
  
              return 0;
          }
  
          _continue_reading(dev);
  
  #ifdef MODULE_NETSTATS_L2
          netdev->stats.rx_count++;
          netdev->stats.rx_bytes += nread;
  #endif
          return nread;
      }
      else if (nread == -1) {
          if ((errno == EAGAIN) || (errno == EWOULDBLOCK)) {
          }
          else {
              err(EXIT_FAILURE, "netdev_tap: read");
          }
      }
      else if (nread == 0) {
          DEBUG("_native_handle_tap_input: ignoring null-event\n");
      }
      else {
          errx(EXIT_FAILURE, "internal error _rx_event");
      }
  
      return -1;
  }
  
  static int _send(netdev_t *netdev, const struct iovec *vector, unsigned n)
  {
      netdev_tap_t *dev = (netdev_tap_t*)netdev;
      int res = _native_writev(dev->tap_fd, vector, n);
  #ifdef MODULE_NETSTATS_L2
      size_t bytes = 0;
      for (unsigned i = 0; i < n; i++) {
          bytes += vector->iov_len;
          vector++;
      }
      netdev->stats.tx_bytes += bytes;
  #endif
      if (netdev->event_callback) {
          netdev->event_callback(netdev, NETDEV_EVENT_TX_COMPLETE);
      }
      return res;
  }
  
  void netdev_tap_setup(netdev_tap_t *dev, const netdev_tap_params_t *params) {
      dev->netdev.driver = &netdev_driver_tap;
      strncpy(dev->tap_name, *(params->tap_name), IFNAMSIZ);
  }
  
  static void _tap_isr(int fd, void *arg) {
      (void) fd;
  
      netdev_t *netdev = (netdev_t *)arg;
  
      if (netdev->event_callback) {
          netdev->event_callback(netdev, NETDEV_EVENT_ISR);
      }
      else {
          puts("netdev_tap: _isr: no event callback.");
      }
  }
  
  static int _init(netdev_t *netdev)
  {
      DEBUG("%s:%s:%u\n", RIOT_FILE_RELATIVE, __func__, __LINE__);
  
      netdev_tap_t *dev = (netdev_tap_t*)netdev;
  
      /* check device parametrs */
      if (dev == NULL) {
          return -ENODEV;
      }
  
      char *name = dev->tap_name;
  #ifdef __MACH__ /* OSX */
      char clonedev[255] = "/dev/"; /* XXX bad size */
      strncpy(clonedev + 5, name, 250);
  #elif defined(__FreeBSD__)
      char clonedev[255] = "/dev/"; /* XXX bad size */
      strncpy(clonedev + 5, name, 250);
  #else /* Linux */
      struct ifreq ifr;
      const char *clonedev = "/dev/net/tun";
  #endif
      /* initialize device descriptor */
      dev->promiscous = 0;
      /* implicitly create the tap interface */
      if ((dev->tap_fd = real_open(clonedev, O_RDWR | O_NONBLOCK)) == -1) {
          err(EXIT_FAILURE, "open(%s)", clonedev);
      }
  #if (defined(__MACH__) || defined(__FreeBSD__)) /* OSX/FreeBSD */
      struct ifaddrs *iflist;
      if (real_getifaddrs(&iflist) == 0) {
          for (struct ifaddrs *cur = iflist; cur; cur = cur->ifa_next) {
              if ((cur->ifa_addr->sa_family == AF_LINK) && (strcmp(cur->ifa_name, name) == 0) && cur->ifa_addr) {
                  struct sockaddr_dl *sdl = (struct sockaddr_dl *)cur->ifa_addr;
                  memcpy(dev->addr, LLADDR(sdl), sdl->sdl_alen);
                  break;
              }
          }
          real_freeifaddrs(iflist);
      }
  #else /* Linux */
      memset(&ifr, 0, sizeof(ifr));
      ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
      strncpy(ifr.ifr_name, name, IFNAMSIZ);
      if (real_ioctl(dev->tap_fd, TUNSETIFF, (void *)&ifr) == -1) {
          _native_in_syscall++;
          warn("ioctl TUNSETIFF");
          warnx("probably the tap interface (%s) does not exist or is already in use", name);
          real_exit(EXIT_FAILURE);
      }
  
      /* get MAC address */
      memset(&ifr, 0, sizeof(ifr));
      snprintf(ifr.ifr_name, sizeof(ifr.ifr_name), "%s", name);
      if (real_ioctl(dev->tap_fd, SIOCGIFHWADDR, &ifr) == -1) {
          _native_in_syscall++;
          warn("ioctl SIOCGIFHWADDR");
          if (real_close(dev->tap_fd) == -1) {
              warn("close");
          }
          real_exit(EXIT_FAILURE);
      }
      memcpy(dev->addr, ifr.ifr_hwaddr.sa_data, ETHERNET_ADDR_LEN);
  
      /* change mac addr so it differs from what the host is using */
      dev->addr[5]++;
  #endif
      DEBUG("gnrc_tapnet_init(): dev->addr = %02x:%02x:%02x:%02x:%02x:%02x\n",
              dev->addr[0], dev->addr[1], dev->addr[2],
              dev->addr[3], dev->addr[4], dev->addr[5]);
  
      /* configure signal handler for fds */
      native_async_read_setup();
      native_async_read_add_handler(dev->tap_fd, netdev, _tap_isr);
  
  #ifdef MODULE_NETSTATS_L2
      memset(&netdev->stats, 0, sizeof(netstats_t));
  #endif
      DEBUG("gnrc_tapnet: initialized.\n");
      return 0;
  }