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