/****************************************************************************
 * netutils/netlib/netlib_getarptab.c
 *
 *   Copyright (C) 2019 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>

#include <sys/socket.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <errno.h>

#include <netpacket/netlink.h>

#include <nuttx/net/arp.h>

#include "netutils/netlib.h"

#if defined(CONFIG_NET_ARP) && defined(CONFIG_NETLINK_ROUTE)

/****************************************************************************
 * Private Types
 ****************************************************************************/

struct netlib_sendto_request_s
{
  struct nlmsghdr hdr;
  struct ndmsg msg;
};

struct netlib_recvfrom_response_s
{
  struct nlmsghdr hdr;
  struct ndmsg msg;
  struct rtattr attr;
  uint8_t data[1];
};

#define SIZEOF_NETLIB_RECVFROM_RESPONSE_S(n) \
  (sizeof(struct netlib_recvfrom_response_s) + (n) - 1)

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: netlib_get_arptable
 *
 * Description:
 *   Attempt to read the entire ARP table into a buffer.
 *
 * Parameters:
 *   arptab   - The location to store the copy of the ARP table
 *   nentries - The size of the provided 'arptab' in number of entries each
 *              of size sizeof(struct arp_entry_s)
 *
 * Return:
 *   The number of ARP table entries read is returned on success; a negated
 *   errno value is returned on failure.
 *
 ****************************************************************************/

ssize_t netlib_get_arptable(FAR struct arp_entry_s *arptab,
                            unsigned int nentries)
{
  FAR struct netlib_recvfrom_response_s *resp;
  struct netlib_sendto_request_s req;
  struct sockaddr_nl addr;
  static unsigned int seqno = 0;
  unsigned int thiseq;
  unsigned int allocsize;
  ssize_t nsent;
  ssize_t nrecvd;
  ssize_t paysize;
  ssize_t maxsize;
  int fd;
  int ret;

  /* Pre-allocate a buffer to hold the response */

  maxsize   = CONFIG_NET_ARPTAB_SIZE * sizeof(struct arp_entry_s);
  allocsize = SIZEOF_NETLIB_RECVFROM_RESPONSE_S(maxsize);
  resp = (FAR struct netlib_recvfrom_response_s *)malloc(allocsize);
  if (resp == NULL)
    {
      fprintf(stderr, "ERROR: Failed to allocate response buffer\n");
      ret = -ENOMEM;
      return EXIT_FAILURE;
    }

  /* Create a NetLink socket with NETLINK_ROUTE protocol */

  fd = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_ROUTE);
  if (fd < 0)
    {
      int errcode = errno;
      fprintf(stderr, "ERROR: socket() failed: %d\n", errcode);
      ret = -errcode;
      goto errout_with_resp;
    }

  /* Bind the socket so that we can use send() and receive() */

  addr.nl_family = AF_NETLINK;
  addr.nl_pad    = 0;
  addr.nl_pid    = getpid();
  addr.nl_groups = RTM_GETNEIGH;

  ret = bind(fd, (FAR const struct sockaddr *)&addr,
             sizeof( struct sockaddr_nl));
  if (fd < 0)
    {
      int errcode = errno;
      fprintf(stderr, "ERROR: bind() failed: %d\n", errcode);
      ret = -errcode;
      goto errout_with_socket;
    }

  /* Initialize the request */

  thiseq = ++seqno;

  memset(&req, 0, sizeof(req));
  req.hdr.nlmsg_len   = NLMSG_LENGTH(sizeof(struct ndmsg));
  req.hdr.nlmsg_flags = NLM_F_REQUEST | NLM_F_ROOT | NLM_F_REQUEST;
  req.hdr.nlmsg_seq   = thiseq;
  req.hdr.nlmsg_type  = RTM_GETNEIGH;
  req.msg.ndm_family  = AF_INET;

  nsent = send(fd, &req, req.hdr.nlmsg_len, 0);
  if (nsent < 0)
    {
      int errcode = errno;
      fprintf(stderr, "ERROR: send() failed: %d\n", errcode);
      ret = -errcode;
      goto errout_with_socket;
    }

  /* Read the response */

  nrecvd = recv(fd, resp, allocsize, 0);
  if (nrecvd < 0)
    {
      int errcode = errno;
      fprintf(stderr, "ERROR: recv() failed: %d\n", errcode);
      ret = -errcode;
      goto errout_with_socket;
    }

  /* Verify the data and transfer the ARP table data to the caller */

  if (resp->hdr.nlmsg_len < sizeof(struct nlmsghdr) ||
      resp->hdr.nlmsg_len > nrecvd)
    {
      fprintf(stderr, "ERROR: Bad message\n");
      ret = -EIO;
      goto errout_with_socket;
    }

   /* The sequence number in the response should match the sequence
    * number in the request (since we created the socket, this should
    * always be true).
    */

   if (resp->hdr.nlmsg_seq != thiseq)
     {
      fprintf(stderr, "ERROR: Bad sequence number in response\n");
      ret = -EIO;
      goto errout_with_socket;
     }

  /* Copy the ARP table data to the caller's buffer */

  paysize = resp->attr.rta_len;
  if (paysize > maxsize)
    {
      paysize = maxsize;
    }

  memcpy(arptab, resp->data, paysize);
  ret = paysize / sizeof(struct arp_entry_s);

errout_with_socket:
  close(fd);

errout_with_resp:
  free(resp);
  return ret;
}

#endif /* CONFIG_NET_ARP && CONFIG_NETLINK_ROUTE */