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    Contents of /trunk/mkinitrd-magellan/busybox/networking/udhcp/arpping.c

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    Revision 984 - (show annotations) (download)
    Sun May 30 11:32:42 2010 UTC (13 years, 11 months ago) by niro
    File MIME type: text/plain
    File size: 4225 byte(s) 
    -updated to busybox-1.16.1 and enabled blkid/uuid support in default config
    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 * Licensed under GPLv2, see file LICENSE in this tarball for details.
    9 */
    10 #include <netinet/if_ether.h>
    11 #include <net/if_arp.h>
    12
    13 #include "common.h"
    14 #include "dhcpd.h"
    15
    16 struct 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 } PACKED;
    34
    35 enum {
    36 ARP_MSG_SIZE = 0x2a
    37 };
    38
    39 /* Returns 1 if no reply received */
    40 int FAST_FUNC arpping(uint32_t test_nip,
    41 const uint8_t *safe_mac,
    42 uint32_t from_ip,
    43 uint8_t *from_mac,
    44 const char *interface)
    45 {
    46 int timeout_ms;
    47 struct pollfd pfd[1];
    48 #define s (pfd[0].fd) /* socket */
    49 int rv = 1; /* "no reply received" yet */
    50 struct sockaddr addr; /* for interface name */
    51 struct arpMsg arp;
    52
    53 s = socket(PF_PACKET, SOCK_PACKET, htons(ETH_P_ARP));
    54 if (s == -1) {
    55 bb_perror_msg(bb_msg_can_not_create_raw_socket);
    56 return -1;
    57 }
    58
    59 if (setsockopt_broadcast(s) == -1) {
    60 bb_perror_msg("can't enable bcast on raw socket");
    61 goto ret;
    62 }
    63
    64 /* send arp request */
    65 memset(&arp, 0, sizeof(arp));
    66 memset(arp.h_dest, 0xff, 6); /* MAC DA */
    67 memcpy(arp.h_source, from_mac, 6); /* MAC SA */
    68 arp.h_proto = htons(ETH_P_ARP); /* protocol type (Ethernet) */
    69 arp.htype = htons(ARPHRD_ETHER); /* hardware type */
    70 arp.ptype = htons(ETH_P_IP); /* protocol type (ARP message) */
    71 arp.hlen = 6; /* hardware address length */
    72 arp.plen = 4; /* protocol address length */
    73 arp.operation = htons(ARPOP_REQUEST); /* ARP op code */
    74 memcpy(arp.sHaddr, from_mac, 6); /* source hardware address */
    75 memcpy(arp.sInaddr, &from_ip, sizeof(from_ip)); /* source IP address */
    76 /* tHaddr is zero-filled */ /* target hardware address */
    77 memcpy(arp.tInaddr, &test_nip, sizeof(test_nip));/* target IP address */
    78
    79 memset(&addr, 0, sizeof(addr));
    80 safe_strncpy(addr.sa_data, interface, sizeof(addr.sa_data));
    81 if (sendto(s, &arp, sizeof(arp), 0, &addr, sizeof(addr)) < 0) {
    82 // TODO: error message? caller didn't expect us to fail,
    83 // just returning 1 "no reply received" misleads it.
    84 goto ret;
    85 }
    86
    87 /* wait for arp reply, and check it */
    88 timeout_ms = 2000;
    89 do {
    90 int r;
    91 unsigned prevTime = monotonic_ms();
    92
    93 pfd[0].events = POLLIN;
    94 r = safe_poll(pfd, 1, timeout_ms);
    95 if (r < 0)
    96 break;
    97 if (r) {
    98 r = safe_read(s, &arp, sizeof(arp));
    99 if (r < 0)
    100 break;
    101
    102 //log3("sHaddr %02x:%02x:%02x:%02x:%02x:%02x",
    103 // arp.sHaddr[0], arp.sHaddr[1], arp.sHaddr[2],
    104 // arp.sHaddr[3], arp.sHaddr[4], arp.sHaddr[5]);
    105
    106 if (r >= ARP_MSG_SIZE
    107 && arp.operation == htons(ARPOP_REPLY)
    108 /* don't check it: Linux doesn't return proper tHaddr (fixed in 2.6.24?) */
    109 /* && memcmp(arp.tHaddr, from_mac, 6) == 0 */
    110 && *((uint32_t *) arp.sInaddr) == test_nip
    111 ) {
    112 /* if ARP source MAC matches safe_mac
    113 * (which is client's MAC), then it's not a conflict
    114 * (client simply already has this IP and replies to ARPs!)
    115 */
    116 if (!safe_mac || memcmp(safe_mac, arp.sHaddr, 6) != 0)
    117 rv = 0;
    118 //else log2("sHaddr == safe_mac");
    119 break;
    120 }
    121 }
    122 timeout_ms -= (unsigned)monotonic_ms() - prevTime;
    123 } while (timeout_ms > 0);
    124
    125 ret:
    126 close(s);
    127 log1("%srp reply received for this address", rv ? "No a" : "A");
    128 return rv;
    129 }