ARP协议的c语言实现源代码【转载】

什么是ARP协议
英文原义：Address Resolution Protocol

中文释义：（RFC-826）地址解析协议

 

#include
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#define src_addr "192.168.0.239"
#define device  "eth0"
#define fill_buf "aaaaaaaaaaaa"
int socket_id;
char *target = src_addr;
int send_count = 0;
int recv_count = 0;
struct in_addr  src, dst;
struct sockaddr_ll   me,  he;
struct timeval   send_time, recv_time;
struct in_addr get_src_ip(char * devices)
{
struct sockaddr_in saddr;
int sock_id = socket(AF_INET, SOCK_DGRAM, 0);
if (sock_id < 0) {
  perror("socket");
  exit(2);
}
if (devices) {
      if (setsockopt(sock_id, SOL_SOCKET, SO_BINDTODEVICE, device, strlen(device)+1) == -1)
   perror("WARNING: interface is ignored");
}
int alen = sizeof(saddr);
memset(&saddr, 0, sizeof(saddr));
saddr.sin_port = htons(0x1000);
saddr.sin_family = AF_INET; 
if (connect(sock_id, (struct sockaddr*)&saddr, sizeof(saddr)) == -1) {
  perror("connect");
  exit(2);
}
if (getsockname(sock_id, (struct sockaddr*)&saddr, &alen) == -1) {
  perror("getsockname");
  exit(2);
}
close(sock_id);
return saddr.sin_addr;
}
int check_device(char* if_dev, int ss)
{
int ifindex;
struct ifreq ifr;
memset(&ifr, 0, sizeof(ifr));
strncpy(ifr.ifr_name, if_dev, IFNAMSIZ-1);
  if (ioctl(ss, SIOCGIFINDEX, &ifr) < 0) {
   fprintf(stderr, "arping: unknown iface %s\n", if_dev);
   exit(2);
  }
  ifindex = ifr.ifr_ifindex;
  if (ioctl(ss, SIOCGIFFLAGS, (char*)&ifr)) {
   perror("ioctl(SIOCGIFFLAGS)");
   exit(2);
  }
  if (!(ifr.ifr_flags&IFF_UP)) {
    printf("Interface \"%s\" is down\n", if_dev);
   exit(2);
  }
  if (ifr.ifr_flags&(IFF_NOARP|IFF_LOOPBACK)) {
    printf("Interface \"%s\" is not ARPable\n", if_dev);
   exit(2);
  }
return ifindex;
} // check_device()
int socket_init()
{
int s,  s_errno;
s = socket(PF_PACKET,  SOCK_DGRAM,  0);
s_errno = errno;

me.sll_family = AF_PACKET;
me.sll_ifindex = check_device(device,  s);
me.sll_protocol = htons(ETH_P_ARP);
if (bind(s,  (struct sockaddr*)&me,  sizeof(me)) == -1) {
  perror("bind");
  exit(2); 
}
int alen = sizeof(me);
if (getsockname(s, (struct sockaddr*)&me, &alen) == -1) {
  perror("getsockname");
  exit(2);
}
if (me.sll_halen == 0) {
  printf("Interface \"%s\" is not ARPable (no ll address)\n", device);
  exit(2);
}
he = me;
memset(he.sll_addr, -1, he.sll_halen);  // set dmac addr FF:FF:FF:FF:FF:FF
return s;
}

int
create_pkt(unsigned char * buf, struct in_addr src, struct in_addr dst, struct sockaddr_ll * FROM, struct sockaddr_ll * TO)
{
struct arphdr *ah = (struct arphdr*) buf;
unsigned char *p = (unsigned char *)(ah+1);
ah->ar_hrd = htons(FROM->sll_hatype);
if (ah->ar_hrd == htons(ARPHRD_FDDI))
  ah->ar_hrd = htons(ARPHRD_ETHER);
ah->ar_pro = htons(ETH_P_IP);
ah->ar_hln = FROM->sll_halen;
ah->ar_pln = 4;
ah->ar_op  =  htons(ARPOP_REQUEST);
memcpy(p, &FROM->sll_addr, ah->ar_hln);
p+=FROM->sll_halen;
memcpy(p, &src, 4);
p+=4;
memcpy(p, &TO->sll_addr, ah->ar_hln);
p+=ah->ar_hln;
memcpy(p, &dst, 4);
p+=4;
memcpy(p, fill_buf, strlen(fill_buf) );
p+=12;
return  (p-buf);
}
void send_pkt()
{
unsigned char send_buf[256];
int pkt_size = create_pkt(send_buf,  src,  dst,  &me,  &he);
gettimeofday(&send_time, NULL); 
int cc = sendto(socket_id, send_buf, pkt_size, 0, (struct sockaddr*)&he, sizeof(he));
if( cc == pkt_size )
  send_count++; 
alarm(1);
}
int chk_recv_pkt(unsigned char * buf, struct sockaddr_ll * FROM)
{
struct arphdr *ah = (struct arphdr*)buf;
unsigned char *p = (unsigned char *)(ah+1);
struct in_addr src_ip, dst_ip;
if (ah->ar_op != htons(ARPOP_REQUEST) &&  ah->ar_op != htons(ARPOP_REPLY))
  return 0;
if (ah->ar_pro != htons(ETH_P_IP) || ah->ar_pln != 4 || ah->ar_hln != me.sll_halen )
  return 0;
memcpy(&src_ip, p+ah->ar_hln, 4);
memcpy(&dst_ip, p+ah->ar_hln+4+ah->ar_hln, 4);
if (src_ip.s_addr != dst.s_addr || src.s_addr != dst_ip.s_addr )
  return 0;

return (p-buf);
}
void disp_info(int received,  struct in_addr dst, int msecs, int usecs, struct sockaddr_ll from)
{
printf("%03d ", received);
printf("%s ", from.sll_pkttype==PACKET_HOST ? "Unicast" : "Broadcast");
printf("%s from %s",  "reply",   inet_ntoa(dst) );
printf(" [%02X:%02X:%02X:%02X:%02X:%02X] ", from.sll_addr[0], from.sll_addr[1], \
  from.sll_addr[2], from.sll_addr[3], from.sll_addr[4], from.sll_addr[5]);   
printf(" %ld.%ld ms\n", (long int)msecs, (long int)usecs);
fflush(stdout);
}
void finish()
{
printf("\nSent %d ARP probe packet(s) \n", send_count);
printf("Received %d response(s)", recv_count);
printf("\n\n");
fflush(stdout);
exit(!recv_count);
}
////////////////////////////////////////////////////////////////
int
main(int argc, char **argv)
{
uid_t uid = getuid();
setuid(uid);
if( *(argv+1) != NULL )
  target = *(argv+1);
if (inet_aton(target, &dst) != 1) {
  struct hostent *hp;
  hp = gethostbyname2(target, AF_INET);
  printf("\ntarget = %s \n", target );
  if (!hp) {
   fprintf(stderr, "arping: unknown host %s\n", target);
   exit(2);
  }
  memcpy(&dst, hp->h_addr, 4);
}
src =  get_src_ip(device);
if (!src.s_addr ) {
  fprintf(stderr, "arping: no source address in not-DAD mode\n");
  exit(2);
}
socket_id = socket_init();
printf("\nARPING %s ", inet_ntoa(dst));
printf("from %s %s\n\n",  inet_ntoa(src), device ? : "");
signal(SIGINT,   finish);
signal(SIGALRM, send_pkt);
send_pkt();

while(1)
{
  struct sockaddr_ll from;
  int alen = sizeof(from);
  char recv_buf[0x1000];
 
  int recv_size = recvfrom(socket_id, recv_buf,  sizeof(recv_buf), 0,  (struct sockaddr *)&from, &alen );
 
  gettimeofday(&recv_time, NULL); 
  if( recv_size < 0 ) {
   perror("arping: recvfrom");
   continue;
  }

  if( chk_recv_pkt(recv_buf, &from) > 0 ) {
   memcpy(he.sll_addr, from.sll_addr, he.sll_halen);  
   long usecs, msecs;
   if (recv_time.tv_sec) {
    usecs = (recv_time.tv_sec - send_time.tv_sec) * 1000000 + recv_time.tv_usec - send_time.tv_usec;
    msecs = (usecs+500)/1000;
    usecs -= msecs*1000 - 500;
   }   
   recv_count++;
   disp_info(recv_count,  dst,  msecs,  usecs,  from);     
  } // if (chk...)   
 
}

return 0;
}