1/* 2 * arpping.c 3 * 4 * Mostly stolen from: dhcpcd - DHCP client daemon 5 * by Yoichi Hariguchi <yoichi@fore.com> 6 */ 7 8#include <sys/types.h> 9#include <sys/time.h> 10#include <time.h> 11#include <sys/types.h> 12#include <sys/socket.h> 13#include <netinet/if_ether.h> 14#include <net/if_arp.h> 15#include <netinet/in.h> 16#include <stdio.h> 17#include <string.h> 18#include <unistd.h> 19#include <errno.h> 20 21#include "dhcpd.h" 22#include "debug.h" 23#include "arpping.h" 24 25/* args: yiaddr - what IP to ping 26 * ip - our ip 27 * mac - our arp address 28 * interface - interface to use 29 * retn: 1 addr free 30 * 0 addr used 31 * -1 error 32 */ 33 34int arpping(u_int32_t yiaddr, u_int32_t ip, unsigned char *mac, char *interface) 35{ 36 37 int timeout = 2; 38 int optval = 1; 39 int s; /* socket */ 40 int rv = 1; /* return value */ 41 struct sockaddr addr; /* for interface name */ 42 struct arpMsg arp; 43 fd_set fdset; 44 struct timeval tm; 45 time_t prevTime; 46 47 48 if ((s = socket (PF_PACKET, SOCK_PACKET, htons(ETH_P_ARP))) == -1) { 49 LOG(LOG_ERR, "Could not open raw socket"); 50 return -1; 51 } 52 53 if (setsockopt(s, SOL_SOCKET, SO_BROADCAST, &optval, sizeof(optval)) == -1) { 54 LOG(LOG_ERR, "Could not setsocketopt on raw socket"); 55 close(s); 56 return -1; 57 } 58 59 /* send arp request */ 60 memset(&arp, 0, sizeof(arp)); 61 memcpy(arp.ethhdr.h_dest, MAC_BCAST_ADDR, 6); /* MAC DA */ 62 memcpy(arp.ethhdr.h_source, mac, 6); /* MAC SA */ 63 arp.ethhdr.h_proto = htons(ETH_P_ARP); /* protocol type (Ethernet) */ 64 arp.htype = htons(ARPHRD_ETHER); /* hardware type */ 65 arp.ptype = htons(ETH_P_IP); /* protocol type (ARP message) */ 66 arp.hlen = 6; /* hardware address length */ 67 arp.plen = 4; /* protocol address length */ 68 arp.operation = htons(ARPOP_REQUEST); /* ARP op code */ 69 *((u_int *) arp.sInaddr) = ip; /* source IP address */ 70 memcpy(arp.sHaddr, mac, 6); /* source hardware address */ 71 *((u_int *) arp.tInaddr) = yiaddr; /* target IP address */ 72 73 memset(&addr, 0, sizeof(addr)); 74 strcpy(addr.sa_data, interface); 75 if (sendto(s, &arp, sizeof(arp), 0, &addr, sizeof(addr)) < 0) 76 rv = 0; 77 78 /* wait arp reply, and check it */ 79 tm.tv_usec = 0; 80 time(&prevTime); 81 while (timeout > 0) { 82 FD_ZERO(&fdset); 83 FD_SET(s, &fdset); 84 tm.tv_sec = timeout; 85 if (select(s + 1, &fdset, (fd_set *) NULL, (fd_set *) NULL, &tm) < 0) { 86 DEBUG(LOG_ERR, "Error on ARPING request: %s", strerror(errno)); 87 if (errno != EINTR) rv = 0; 88 } else if (FD_ISSET(s, &fdset)) { 89 if (recv(s, &arp, sizeof(arp), 0) < 0 ) rv = 0; 90 if (arp.operation == htons(ARPOP_REPLY) && 91 bcmp(arp.tHaddr, mac, 6) == 0 && 92 *((u_int *) arp.sInaddr) == yiaddr) { 93 DEBUG(LOG_INFO, "Valid arp reply receved for this address"); 94 rv = 0; 95 break; 96 } 97 } 98 timeout -= time(NULL) - prevTime; 99 time(&prevTime); 100 } 101 close(s); 102 DEBUG(LOG_INFO, "%salid arp replies for this address", rv ? "No v" : "V"); 103 return rv; 104} 105