1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
|
/* vi: set sw=4 ts=4: */
/*
* arpping.c
*
* Mostly stolen from: dhcpcd - DHCP client daemon
* by Yoichi Hariguchi <yoichi@fore.com>
*
* Licensed under GPLv2, see file LICENSE in this tarball for details.
*/
#include <netinet/if_ether.h>
#include <net/if_arp.h>
#include "common.h"
#include "dhcpd.h"
struct arpMsg {
/* Ethernet header */
uint8_t h_dest[6]; /* 00 destination ether addr */
uint8_t h_source[6]; /* 06 source ether addr */
uint16_t h_proto; /* 0c packet type ID field */
/* ARP packet */
uint16_t htype; /* 0e hardware type (must be ARPHRD_ETHER) */
uint16_t ptype; /* 10 protocol type (must be ETH_P_IP) */
uint8_t hlen; /* 12 hardware address length (must be 6) */
uint8_t plen; /* 13 protocol address length (must be 4) */
uint16_t operation; /* 14 ARP opcode */
uint8_t sHaddr[6]; /* 16 sender's hardware address */
uint8_t sInaddr[4]; /* 1c sender's IP address */
uint8_t tHaddr[6]; /* 20 target's hardware address */
uint8_t tInaddr[4]; /* 26 target's IP address */
uint8_t pad[18]; /* 2a pad for min. ethernet payload (60 bytes) */
} PACKED;
enum {
ARP_MSG_SIZE = 0x2a
};
/* Returns 1 if no reply received */
int FAST_FUNC arpping(uint32_t test_ip,
const uint8_t *safe_mac,
uint32_t from_ip,
uint8_t *from_mac,
const char *interface)
{
int timeout_ms;
struct pollfd pfd[1];
#define s (pfd[0].fd) /* socket */
int rv = 1; /* "no reply received" yet */
struct sockaddr addr; /* for interface name */
struct arpMsg arp;
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 enable bcast on raw socket");
goto ret;
}
/* send arp request */
memset(&arp, 0, sizeof(arp));
memset(arp.h_dest, 0xff, 6); /* MAC DA */
memcpy(arp.h_source, from_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.sHaddr, from_mac, 6); /* source hardware address */
memcpy(arp.sInaddr, &from_ip, sizeof(from_ip)); /* source IP address */
/* tHaddr is zero-filled */ /* target hardware address */
memcpy(arp.tInaddr, &test_ip, sizeof(test_ip)); /* target IP address */
memset(&addr, 0, sizeof(addr));
safe_strncpy(addr.sa_data, interface, sizeof(addr.sa_data));
if (sendto(s, &arp, sizeof(arp), 0, &addr, sizeof(addr)) < 0) {
// TODO: error message? caller didn't expect us to fail,
// just returning 1 "no reply received" misleads it.
goto ret;
}
/* wait for arp reply, and check it */
timeout_ms = 2000;
do {
int r;
unsigned prevTime = monotonic_us();
pfd[0].events = POLLIN;
r = safe_poll(pfd, 1, timeout_ms);
if (r < 0)
break;
if (r) {
r = read(s, &arp, sizeof(arp));
if (r < 0)
break;
//bb_error_msg("sHaddr %02x:%02x:%02x:%02x:%02x:%02x",
// arp.sHaddr[0], arp.sHaddr[1], arp.sHaddr[2],
// arp.sHaddr[3], arp.sHaddr[4], arp.sHaddr[5]);
if (r >= ARP_MSG_SIZE
&& arp.operation == htons(ARPOP_REPLY)
/* don't check it: Linux doesn't return proper tHaddr (fixed in 2.6.24?) */
/* && memcmp(arp.tHaddr, from_mac, 6) == 0 */
&& *((uint32_t *) arp.sInaddr) == test_ip
) {
/* if ARP source MAC matches safe_mac
* (which is client's MAC), then it's not a conflict
* (client simply already has this IP and replies to ARPs!)
*/
if (!safe_mac || memcmp(safe_mac, arp.sHaddr, 6) != 0)
rv = 0;
//else bb_error_msg("sHaddr == safe_mac");
break;
}
}
timeout_ms -= ((unsigned)monotonic_us() - prevTime) / 1000;
} while (timeout_ms > 0);
ret:
close(s);
DEBUG("%srp reply received for this address", rv ? "No a" : "A");
return rv;
}
|
