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

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    Revision 1123 - (hide annotations) (download)
    Wed Aug 18 21:56:57 2010 UTC (13 years, 9 months ago) by niro
    File MIME type: text/plain
    File size: 4263 byte(s) 
    -updated to busybox-1.17.1
    1 niro 532 /* vi: set sw=4 ts=4: */
    2     /*
    3     * Mostly stolen from: dhcpcd - DHCP client daemon
    4     * by Yoichi Hariguchi <yoichi@fore.com>
    5 niro 984 *
    6     * Licensed under GPLv2, see file LICENSE in this tarball for details.
    7 niro 532 */
    8     #include <netinet/if_ether.h>
    9     #include <net/if_arp.h>
    10    
    11     #include "common.h"
    12     #include "dhcpd.h"
    13    
    14     struct arpMsg {
    15     /* Ethernet header */
    16 niro 816 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 niro 532
    20     /* ARP packet */
    21 niro 816 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 niro 532
    33 niro 816 enum {
    34     ARP_MSG_SIZE = 0x2a
    35     };
    36 niro 532
    37 niro 816 /* Returns 1 if no reply received */
    38 niro 984 int 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 niro 532 {
    44 niro 816 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 niro 532
    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 niro 984 bb_perror_msg("can't enable bcast on raw socket");
    59 niro 816 goto ret;
    60 niro 532 }
    61    
    62     /* send arp request */
    63     memset(&arp, 0, sizeof(arp));
    64 niro 816 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 niro 984 /* tHaddr is zero-filled */ /* target hardware address */
    75     memcpy(arp.tInaddr, &test_nip, sizeof(test_nip));/* target IP address */
    76 niro 532
    77     memset(&addr, 0, sizeof(addr));
    78 niro 816 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 niro 532
    85 niro 816 /* wait for arp reply, and check it */
    86     timeout_ms = 2000;
    87     do {
    88 niro 1123 typedef uint32_t aliased_uint32_t FIX_ALIASING;
    89 niro 816 int r;
    90 niro 984 unsigned prevTime = monotonic_ms();
    91 niro 816
    92     pfd[0].events = POLLIN;
    93     r = safe_poll(pfd, 1, timeout_ms);
    94     if (r < 0)
    95     break;
    96     if (r) {
    97 niro 984 r = safe_read(s, &arp, sizeof(arp));
    98 niro 816 if (r < 0)
    99     break;
    100 niro 984
    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 niro 816 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 niro 1123 && *(aliased_uint32_t*)arp.sInaddr == test_nip
    110 niro 816 ) {
    111 niro 984 /* 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 niro 532 break;
    119     }
    120     }
    121 niro 984 timeout_ms -= (unsigned)monotonic_ms() - prevTime;
    122 niro 816 } while (timeout_ms > 0);
    123    
    124     ret:
    125 niro 532 close(s);
    126 niro 984 log1("%srp reply received for this address", rv ? "No a" : "A");
    127 niro 532 return rv;
    128     }