/* vi: set sw=4 ts=4: */ /* * arpping.c * * Mostly stolen from: dhcpcd - DHCP client daemon * by Yoichi Hariguchi */ #include #include #include "common.h" #include "dhcpd.h" struct arpMsg { /* Ethernet header */ uint8_t h_dest[6]; /* destination ether addr */ uint8_t h_source[6]; /* source ether addr */ uint16_t h_proto; /* packet type ID field */ /* ARP packet */ uint16_t htype; /* hardware type (must be ARPHRD_ETHER) */ uint16_t ptype; /* protocol type (must be ETH_P_IP) */ uint8_t hlen; /* hardware address length (must be 6) */ uint8_t plen; /* protocol address length (must be 4) */ uint16_t operation; /* ARP opcode */ uint8_t sHaddr[6]; /* sender's hardware address */ uint8_t sInaddr[4]; /* sender's IP address */ uint8_t tHaddr[6]; /* target's hardware address */ uint8_t tInaddr[4]; /* target's IP address */ uint8_t pad[18]; /* pad for min. Ethernet payload (60 bytes) */ } ATTRIBUTE_PACKED; /* 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 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; s = socket(PF_PACKET, SOCK_PACKET, htons(ETH_P_ARP)); if (s == -1) { bb_perror_msg(bb_msg_can_not_create_raw_socket); return -1; } if (setsockopt_broadcast(s) == -1) { bb_perror_msg("cannot 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) { bb_perror_msg("error on ARPING request"); 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("Valid arp reply received for this address"); rv = 0; break; } } timeout -= uptime() - prevTime; prevTime = uptime(); } close(s); DEBUG("%salid arp replies for this address", rv ? "No v" : "V"); return rv; }