source: branches/3.2/mindi-busybox/networking/udhcp/arpping.c @ 3232

Last change on this file since 3232 was 3232, checked in by bruno, 5 years ago
  • Update mindi-busybox to 1.21.1
File size: 4.3 KB
Line 
1/* vi: set sw=4 ts=4: */
2/*
3 * Mostly stolen from: dhcpcd - DHCP client daemon
4 * by Yoichi Hariguchi <yoichi@fore.com>
5 *
6 * Licensed under GPLv2, see file LICENSE in this source tree.
7 */
8#include <netinet/if_ether.h>
9#include <net/if_arp.h>
10
11#include "common.h"
12#include "dhcpd.h"
13
14struct arpMsg {
15    /* Ethernet header */
16    uint8_t  h_dest[6];     /* 00 destination ether addr */
17    uint8_t  h_source[6];   /* 06 source ether addr */
18    uint16_t h_proto;       /* 0c packet type ID field */
19
20    /* ARP packet */
21    uint16_t htype;         /* 0e hardware type (must be ARPHRD_ETHER) */
22    uint16_t ptype;         /* 10 protocol type (must be ETH_P_IP) */
23    uint8_t  hlen;          /* 12 hardware address length (must be 6) */
24    uint8_t  plen;          /* 13 protocol address length (must be 4) */
25    uint16_t operation;     /* 14 ARP opcode */
26    uint8_t  sHaddr[6];     /* 16 sender's hardware address */
27    uint8_t  sInaddr[4];    /* 1c sender's IP address */
28    uint8_t  tHaddr[6];     /* 20 target's hardware address */
29    uint8_t  tInaddr[4];    /* 26 target's IP address */
30    uint8_t  pad[18];       /* 2a pad for min. ethernet payload (60 bytes) */
31} PACKED;
32
33enum {
34    ARP_MSG_SIZE = 0x2a
35};
36
37/* Returns 1 if no reply received */
38int FAST_FUNC arpping(uint32_t test_nip,
39        const uint8_t *safe_mac,
40        uint32_t from_ip,
41        uint8_t *from_mac,
42        const char *interface)
43{
44    int timeout_ms;
45    struct pollfd pfd[1];
46#define s (pfd[0].fd)           /* socket */
47    int rv = 1;             /* "no reply received" yet */
48    struct sockaddr addr;   /* for interface name */
49    struct arpMsg arp;
50
51    s = socket(PF_PACKET, SOCK_PACKET, htons(ETH_P_ARP));
52    if (s == -1) {
53        bb_perror_msg(bb_msg_can_not_create_raw_socket);
54        return -1;
55    }
56
57    if (setsockopt_broadcast(s) == -1) {
58        bb_perror_msg("can't enable bcast on raw socket");
59        goto ret;
60    }
61
62    /* send arp request */
63    memset(&arp, 0, sizeof(arp));
64    memset(arp.h_dest, 0xff, 6);                    /* MAC DA */
65    memcpy(arp.h_source, from_mac, 6);              /* MAC SA */
66    arp.h_proto = htons(ETH_P_ARP);                 /* protocol type (Ethernet) */
67    arp.htype = htons(ARPHRD_ETHER);                /* hardware type */
68    arp.ptype = htons(ETH_P_IP);                    /* protocol type (ARP message) */
69    arp.hlen = 6;                                   /* hardware address length */
70    arp.plen = 4;                                   /* protocol address length */
71    arp.operation = htons(ARPOP_REQUEST);           /* ARP op code */
72    memcpy(arp.sHaddr, from_mac, 6);                /* source hardware address */
73    memcpy(arp.sInaddr, &from_ip, sizeof(from_ip)); /* source IP address */
74    /* tHaddr is zero-filled */                     /* target hardware address */
75    memcpy(arp.tInaddr, &test_nip, sizeof(test_nip));/* target IP address */
76
77    memset(&addr, 0, sizeof(addr));
78    safe_strncpy(addr.sa_data, interface, sizeof(addr.sa_data));
79    if (sendto(s, &arp, sizeof(arp), 0, &addr, sizeof(addr)) < 0) {
80        // TODO: error message? caller didn't expect us to fail,
81        // just returning 1 "no reply received" misleads it.
82        goto ret;
83    }
84
85    /* wait for arp reply, and check it */
86    timeout_ms = 2000;
87    do {
88        typedef uint32_t aliased_uint32_t FIX_ALIASING;
89        int r;
90        unsigned prevTime = monotonic_ms();
91
92        pfd[0].events = POLLIN;
93        r = safe_poll(pfd, 1, timeout_ms);
94        if (r < 0)
95            break;
96        if (r) {
97            r = safe_read(s, &arp, sizeof(arp));
98            if (r < 0)
99                break;
100
101            //log3("sHaddr %02x:%02x:%02x:%02x:%02x:%02x",
102            //  arp.sHaddr[0], arp.sHaddr[1], arp.sHaddr[2],
103            //  arp.sHaddr[3], arp.sHaddr[4], arp.sHaddr[5]);
104
105            if (r >= ARP_MSG_SIZE
106             && arp.operation == htons(ARPOP_REPLY)
107             /* don't check it: Linux doesn't return proper tHaddr (fixed in 2.6.24?) */
108             /* && memcmp(arp.tHaddr, from_mac, 6) == 0 */
109             && *(aliased_uint32_t*)arp.sInaddr == test_nip
110            ) {
111                /* if ARP source MAC matches safe_mac
112                 * (which is client's MAC), then it's not a conflict
113                 * (client simply already has this IP and replies to ARPs!)
114                 */
115                if (!safe_mac || memcmp(safe_mac, arp.sHaddr, 6) != 0)
116                    rv = 0;
117                //else log2("sHaddr == safe_mac");
118                break;
119            }
120        }
121        timeout_ms -= (unsigned)monotonic_ms() - prevTime + 1;
122
123        /* We used to check "timeout_ms > 0", but
124         * this is more under/overflow-resistant
125         * (people did see overflows here when system time jumps):
126         */
127    } while ((unsigned)timeout_ms <= 2000);
128
129 ret:
130    close(s);
131    log1("%srp reply received for this address", rv ? "No a" : "A");
132    return rv;
133}
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