1/* vi: set sw=4 ts=4: */ 2/* 3 * arpping.c 4 * 5 * Mostly stolen from: dhcpcd - DHCP client daemon 6 * by Yoichi Hariguchi <yoichi@fore.com> 7 */ 8 9#include <netinet/if_ether.h> 10#include <net/if_arp.h> 11 12#include "common.h" 13#include "dhcpd.h" 14 15 16struct arpMsg { 17 /* Ethernet header */ 18 uint8_t h_dest[6]; /* 00 destination ether addr */ 19 uint8_t h_source[6]; /* 06 source ether addr */ 20 uint16_t h_proto; /* 0c packet type ID field */ 21 22 /* ARP packet */ 23 uint16_t htype; /* 0e hardware type (must be ARPHRD_ETHER) */ 24 uint16_t ptype; /* 10 protocol type (must be ETH_P_IP) */ 25 uint8_t hlen; /* 12 hardware address length (must be 6) */ 26 uint8_t plen; /* 13 protocol address length (must be 4) */ 27 uint16_t operation; /* 14 ARP opcode */ 28 uint8_t sHaddr[6]; /* 16 sender's hardware address */ 29 uint8_t sInaddr[4]; /* 1c sender's IP address */ 30 uint8_t tHaddr[6]; /* 20 target's hardware address */ 31 uint8_t tInaddr[4]; /* 26 target's IP address */ 32 uint8_t pad[18]; /* 2a pad for min. ethernet payload (60 bytes) */ 33} ATTRIBUTE_PACKED; 34 35 36/* Returns 1 if no reply received */ 37 38int arpping(uint32_t test_ip, uint32_t from_ip, uint8_t *from_mac, const char *interface) 39{ 40 int timeout = 2; 41 int s; /* socket */ 42 int rv = 1; /* "no reply received" yet */ 43 struct sockaddr addr; /* for interface name */ 44 struct arpMsg arp; 45 fd_set fdset; 46 struct timeval tm; 47 unsigned prevTime; 48 49 s = socket(PF_PACKET, SOCK_PACKET, htons(ETH_P_ARP)); 50 if (s == -1) { 51 bb_perror_msg(bb_msg_can_not_create_raw_socket); 52 return -1; 53 } 54 55 if (setsockopt_broadcast(s) == -1) { 56 bb_perror_msg("cannot setsocketopt on raw socket"); 57 goto ret; 58 } 59 60 /* send arp request */ 61 memset(&arp, 0, sizeof(arp)); 62 memset(arp.h_dest, 0xff, 6); /* MAC DA */ 63 memcpy(arp.h_source, from_mac, 6); /* MAC SA */ 64 arp.h_proto = htons(ETH_P_ARP); /* protocol type (Ethernet) */ 65 arp.htype = htons(ARPHRD_ETHER); /* hardware type */ 66 arp.ptype = htons(ETH_P_IP); /* protocol type (ARP message) */ 67 arp.hlen = 6; /* hardware address length */ 68 arp.plen = 4; /* protocol address length */ 69 arp.operation = htons(ARPOP_REQUEST); /* ARP op code */ 70 memcpy(arp.sHaddr, from_mac, 6); /* source hardware address */ 71 memcpy(arp.sInaddr, &from_ip, sizeof(from_ip)); /* source IP address */ 72 /* tHaddr */ /* target hardware address */ 73 memcpy(arp.tInaddr, &test_ip, sizeof(test_ip)); /* target IP address */ 74 75 memset(&addr, 0, sizeof(addr)); 76 safe_strncpy(addr.sa_data, interface, sizeof(addr.sa_data)); 77 if (sendto(s, &arp, sizeof(arp), 0, &addr, sizeof(addr)) < 0) 78 goto ret; 79 80 /* wait for arp reply, and check it */ 81 do { 82 int r; 83 prevTime = monotonic_sec(); 84 FD_ZERO(&fdset); 85 FD_SET(s, &fdset); 86 tm.tv_sec = timeout; 87 tm.tv_usec = 0; 88 r = select(s + 1, &fdset, NULL, NULL, &tm); 89 if (r < 0) { 90 bb_perror_msg("error on ARPING request"); 91 if (errno != EINTR) 92 break; 93 } else if (r) { 94 if (recv(s, &arp, sizeof(arp), 0) < 0) 95 break; 96 if (arp.operation == htons(ARPOP_REPLY) 97 && memcmp(arp.tHaddr, from_mac, 6) == 0 98 && *((uint32_t *) arp.sInaddr) == test_ip 99 ) { 100 rv = 0; 101 break; 102 } 103 } 104 timeout -= monotonic_sec() - prevTime; 105 } while (timeout > 0); 106 107 ret: 108 close(s); 109 DEBUG("%srp reply received for this address", rv ? "No a" : "A"); 110 return rv; 111} 112