/*
 * arpping.c
 *
 * Mostly stolen from: dhcpcd - DHCP client daemon
 * by Yoichi Hariguchi <yoichi@fore.com>
 */

#include <sys/time.h>
#include <time.h>
#include <sys/socket.h>
#include <netinet/if_ether.h>
#include <net/if_arp.h>
#include <netinet/in.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>

#include "dhcpd.h"
#include "arpping.h"
#include "common.h"

/* args:  yiaddr - what IP to ping
 *    ip - our ip
 *    mac - our arp address
 *    interface - interface to use
 * retn:  1 addr free
 *    0 addr used
 *    -1 error
 */

/* FIXME: match response against chaddr */
int arpping(uint32_t yiaddr, uint32_t ip, uint8_t *mac, char *interface)
{

  int timeout = 2;
  int optval = 1;
  int s;      /* socket */
  int rv = 1;     /* return value */
  struct sockaddr addr;   /* for interface name */
  struct arpMsg arp;
  fd_set    fdset;
  struct timeval  tm;
  time_t    prevTime;


  if ((s = socket (PF_PACKET, SOCK_PACKET, htons(ETH_P_ARP))) == -1) {
#ifdef IN_BUSYBOX
    LOG(LOG_ERR, bb_msg_can_not_create_raw_socket);
#else
    LOG(LOG_ERR, "Could not open raw socket");
#endif
    return -1;
  }

  if (setsockopt(s, SOL_SOCKET, SO_BROADCAST, &optval, sizeof(optval)) == -1) {
    LOG(LOG_ERR, "Could not setsocketopt on raw socket");
    close(s);
    return -1;
  }

  /* send arp request */
  memset(&arp, 0, sizeof(arp));
  memcpy(arp.h_dest, MAC_BCAST_ADDR, 6);    /* MAC DA */
  memcpy(arp.h_source, mac, 6);     /* MAC SA */
  arp.h_proto = htons(ETH_P_ARP);     /* protocol type (Ethernet) */
  arp.htype = htons(ARPHRD_ETHER);    /* hardware type */
  arp.ptype = htons(ETH_P_IP);      /* protocol type (ARP message) */
  arp.hlen = 6;         /* hardware address length */
  arp.plen = 4;         /* protocol address length */
  arp.operation = htons(ARPOP_REQUEST);   /* ARP op code */
  memcpy(arp.sInaddr, &ip, sizeof(ip));   /* source IP address */
  memcpy(arp.sHaddr, mac, 6);     /* source hardware address */
  memcpy(arp.tInaddr, &yiaddr, sizeof(yiaddr)); /* target IP address */

  memset(&addr, 0, sizeof(addr));
  strcpy(addr.sa_data, interface);
  if (sendto(s, &arp, sizeof(arp), 0, &addr, sizeof(addr)) < 0)
    rv = 0;

  /* wait arp reply, and check it */
  tm.tv_usec = 0;
  prevTime = uptime();
  while (timeout > 0) {
    FD_ZERO(&fdset);
    FD_SET(s, &fdset);
    tm.tv_sec = timeout;
    if (select(s + 1, &fdset, (fd_set *) NULL, (fd_set *) NULL, &tm) < 0) {
      DEBUG(LOG_ERR, "Error on ARPING request: %m");
      if (errno != EINTR) rv = 0;
    } else if (FD_ISSET(s, &fdset)) {
      if (recv(s, &arp, sizeof(arp), 0) < 0 ) rv = 0;
      if (arp.operation == htons(ARPOP_REPLY) &&
          memcmp(arp.tHaddr, mac, 6) == 0 &&
          *((uint32_t *) arp.sInaddr) == yiaddr) {
        DEBUG(LOG_INFO, "Valid arp reply receved for this address");
        rv = 0;
        break;
      }
    }
    timeout -= uptime() - prevTime;
    prevTime = uptime();
  }
  close(s);
  DEBUG(LOG_INFO, "%salid arp replies for this address", rv ? "No v" : "V");
  return rv;
}
