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115 lines
3.3 KiB
C
115 lines
3.3 KiB
C
/* vi: set sw=4 ts=4: */
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/*
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* arpping.c
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*
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* Mostly stolen from: dhcpcd - DHCP client daemon
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* by Yoichi Hariguchi <yoichi@fore.com>
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*/
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#include <netinet/if_ether.h>
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#include <net/if_arp.h>
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#include "common.h"
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#include "dhcpd.h"
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struct arpMsg {
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/* Ethernet header */
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uint8_t h_dest[6]; /* destination ether addr */
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uint8_t h_source[6]; /* source ether addr */
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uint16_t h_proto; /* packet type ID field */
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/* ARP packet */
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uint16_t htype; /* hardware type (must be ARPHRD_ETHER) */
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uint16_t ptype; /* protocol type (must be ETH_P_IP) */
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uint8_t hlen; /* hardware address length (must be 6) */
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uint8_t plen; /* protocol address length (must be 4) */
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uint16_t operation; /* ARP opcode */
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uint8_t sHaddr[6]; /* sender's hardware address */
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uint8_t sInaddr[4]; /* sender's IP address */
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uint8_t tHaddr[6]; /* target's hardware address */
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uint8_t tInaddr[4]; /* target's IP address */
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uint8_t pad[18]; /* pad for min. Ethernet payload (60 bytes) */
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} ATTRIBUTE_PACKED;
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/* args: yiaddr - what IP to ping
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* ip - our ip
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* mac - our arp address
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* interface - interface to use
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* retn: 1 addr free
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* 0 addr used
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* -1 error
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*/
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/* FIXME: match response against chaddr */
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int arpping(uint32_t yiaddr, uint32_t ip, uint8_t *mac, char *interface)
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{
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int timeout = 2;
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int s; /* socket */
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int rv = 1; /* return value */
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struct sockaddr addr; /* for interface name */
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struct arpMsg arp;
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fd_set fdset;
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struct timeval tm;
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time_t prevTime;
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s = socket(PF_PACKET, SOCK_PACKET, htons(ETH_P_ARP));
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if (s == -1) {
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bb_perror_msg(bb_msg_can_not_create_raw_socket);
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return -1;
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}
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if (setsockopt_broadcast(s) == -1) {
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bb_perror_msg("cannot setsocketopt on raw socket");
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close(s);
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return -1;
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}
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/* send arp request */
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memset(&arp, 0, sizeof(arp));
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memcpy(arp.h_dest, MAC_BCAST_ADDR, 6); /* MAC DA */
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memcpy(arp.h_source, mac, 6); /* MAC SA */
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arp.h_proto = htons(ETH_P_ARP); /* protocol type (Ethernet) */
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arp.htype = htons(ARPHRD_ETHER); /* hardware type */
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arp.ptype = htons(ETH_P_IP); /* protocol type (ARP message) */
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arp.hlen = 6; /* hardware address length */
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arp.plen = 4; /* protocol address length */
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arp.operation = htons(ARPOP_REQUEST); /* ARP op code */
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memcpy(arp.sInaddr, &ip, sizeof(ip)); /* source IP address */
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memcpy(arp.sHaddr, mac, 6); /* source hardware address */
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memcpy(arp.tInaddr, &yiaddr, sizeof(yiaddr)); /* target IP address */
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memset(&addr, 0, sizeof(addr));
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strcpy(addr.sa_data, interface);
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if (sendto(s, &arp, sizeof(arp), 0, &addr, sizeof(addr)) < 0)
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rv = 0;
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/* wait arp reply, and check it */
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tm.tv_usec = 0;
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prevTime = uptime();
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while (timeout > 0) {
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FD_ZERO(&fdset);
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FD_SET(s, &fdset);
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tm.tv_sec = timeout;
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if (select(s + 1, &fdset, (fd_set *) NULL, (fd_set *) NULL, &tm) < 0) {
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bb_perror_msg("error on ARPING request");
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if (errno != EINTR) rv = 0;
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} else if (FD_ISSET(s, &fdset)) {
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if (recv(s, &arp, sizeof(arp), 0) < 0 ) rv = 0;
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if (arp.operation == htons(ARPOP_REPLY) &&
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memcmp(arp.tHaddr, mac, 6) == 0 &&
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*((uint32_t *) arp.sInaddr) == yiaddr) {
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DEBUG("Valid arp reply received for this address");
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rv = 0;
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break;
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}
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}
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timeout -= uptime() - prevTime;
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prevTime = uptime();
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}
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close(s);
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DEBUG("%salid arp replies for this address", rv ? "No v" : "V");
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return rv;
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}
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