source: MondoRescue/branches/3.3/mindi-busybox/networking/udhcp/packet.c@ 3621

/* vi: set sw=4 ts=4: */
/*
 * Packet ops
 *
 * Rewrite by Russ Dill <Russ.Dill@asu.edu> July 2001
 *
 * Licensed under GPLv2, see file LICENSE in this source tree.
 */
#include "common.h"
#include "dhcpd.h"
#include <netinet/in.h>
#include <netinet/if_ether.h>
#include <netpacket/packet.h>

void FAST_FUNC udhcp_init_header(struct dhcp_packet *packet, char type)
{
    memset(packet, 0, sizeof(*packet));
    packet->op = BOOTREQUEST; /* if client to a server */
    switch (type) {
    case DHCPOFFER:
    case DHCPACK:
    case DHCPNAK:
        packet->op = BOOTREPLY; /* if server to client */
    }
    packet->htype = 1; /* ethernet */
    packet->hlen = 6;
    packet->cookie = htonl(DHCP_MAGIC);
    if (DHCP_END != 0)
        packet->options[0] = DHCP_END;
    udhcp_add_simple_option(packet, DHCP_MESSAGE_TYPE, type);
}

#if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 2
void FAST_FUNC udhcp_dump_packet(struct dhcp_packet *packet)
{
    char buf[sizeof(packet->chaddr)*2 + 1];

    if (dhcp_verbose < 2)
        return;

    bb_error_msg(
        //"op %x"
        //" htype %x"
        " hlen %x"
        //" hops %x"
        " xid %x"
        //" secs %x"
        //" flags %x"
        " ciaddr %x"
        " yiaddr %x"
        " siaddr %x"
        " giaddr %x"
        //" chaddr %s"
        //" sname %s"
        //" file %s"
        //" cookie %x"
        //" options %s"
        //, packet->op
        //, packet->htype
        , packet->hlen
        //, packet->hops
        , packet->xid
        //, packet->secs
        //, packet->flags
        , packet->ciaddr
        , packet->yiaddr
        , packet->siaddr_nip
        , packet->gateway_nip
        //, packet->chaddr[16]
        //, packet->sname[64]
        //, packet->file[128]
        //, packet->cookie
        //, packet->options[]
    );
    *bin2hex(buf, (void *) packet->chaddr, sizeof(packet->chaddr)) = '\0';
    bb_error_msg("chaddr %s", buf);
}
#endif

/* Read a packet from socket fd, return -1 on read error, -2 on packet error */
int FAST_FUNC udhcp_recv_kernel_packet(struct dhcp_packet *packet, int fd)
{
    int bytes;

    memset(packet, 0, sizeof(*packet));
    bytes = safe_read(fd, packet, sizeof(*packet));
    if (bytes < 0) {
        log1("packet read error, ignoring");
        return bytes; /* returns -1 */
    }

    if (bytes < offsetof(struct dhcp_packet, options)
     || packet->cookie != htonl(DHCP_MAGIC)
    ) {
        bb_error_msg("packet with bad magic, ignoring");
        return -2;
    }
    log1("received %s", "a packet");
    udhcp_dump_packet(packet);

    return bytes;
}

/* Construct a ip/udp header for a packet, send packet */
int FAST_FUNC udhcp_send_raw_packet(struct dhcp_packet *dhcp_pkt,
        uint32_t source_nip, int source_port,
        uint32_t dest_nip, int dest_port, const uint8_t *dest_arp,
        int ifindex)
{
    struct sockaddr_ll dest_sll;
    struct ip_udp_dhcp_packet packet;
    unsigned padding;
    int fd;
    int result = -1;
    const char *msg;

    fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
    if (fd < 0) {
        msg = "socket(%s)";
        goto ret_msg;
    }

    memset(&dest_sll, 0, sizeof(dest_sll));
    memset(&packet, 0, offsetof(struct ip_udp_dhcp_packet, data));
    packet.data = *dhcp_pkt; /* struct copy */

    dest_sll.sll_family = AF_PACKET;
    dest_sll.sll_protocol = htons(ETH_P_IP);
    dest_sll.sll_ifindex = ifindex;
    dest_sll.sll_halen = 6;
    memcpy(dest_sll.sll_addr, dest_arp, 6);

    if (bind(fd, (struct sockaddr *)&dest_sll, sizeof(dest_sll)) < 0) {
        msg = "bind(%s)";
        goto ret_close;
    }

    /* We were sending full-sized DHCP packets (zero padded),
     * but some badly configured servers were seen dropping them.
     * Apparently they drop all DHCP packets >576 *ethernet* octets big,
     * whereas they may only drop packets >576 *IP* octets big
     * (which for typical Ethernet II means 590 octets: 6+6+2 + 576).
     *
     * In order to work with those buggy servers,
     * we truncate packets after end option byte.
     *
     * However, RFC 1542 says "The IP Total Length and UDP Length
     * must be large enough to contain the minimal BOOTP header of 300 octets".
     * Thus, we retain enough padding to not go below 300 BOOTP bytes.
     * Some devices have filters which drop DHCP packets shorter than that.
     */
    padding = DHCP_OPTIONS_BUFSIZE - 1 - udhcp_end_option(packet.data.options);
    if (padding > DHCP_SIZE - 300)
        padding = DHCP_SIZE - 300;

    packet.ip.protocol = IPPROTO_UDP;
    packet.ip.saddr = source_nip;
    packet.ip.daddr = dest_nip;
    packet.udp.source = htons(source_port);
    packet.udp.dest = htons(dest_port);
    /* size, excluding IP header: */
    packet.udp.len = htons(UDP_DHCP_SIZE - padding);
    /* for UDP checksumming, ip.len is set to UDP packet len */
    packet.ip.tot_len = packet.udp.len;
    packet.udp.check = inet_cksum((uint16_t *)&packet,
            IP_UDP_DHCP_SIZE - padding);
    /* but for sending, it is set to IP packet len */
    packet.ip.tot_len = htons(IP_UDP_DHCP_SIZE - padding);
    packet.ip.ihl = sizeof(packet.ip) >> 2;
    packet.ip.version = IPVERSION;
    packet.ip.ttl = IPDEFTTL;
    packet.ip.check = inet_cksum((uint16_t *)&packet.ip, sizeof(packet.ip));

    udhcp_dump_packet(dhcp_pkt);
    result = sendto(fd, &packet, IP_UDP_DHCP_SIZE - padding, /*flags:*/ 0,
            (struct sockaddr *) &dest_sll, sizeof(dest_sll));
    msg = "sendto";
 ret_close:
    close(fd);
    if (result < 0) {
 ret_msg:
        bb_perror_msg(msg, "PACKET");
    }
    return result;
}

/* Let the kernel do all the work for packet generation */
int FAST_FUNC udhcp_send_kernel_packet(struct dhcp_packet *dhcp_pkt,
        uint32_t source_nip, int source_port,
        uint32_t dest_nip, int dest_port)
{
    struct sockaddr_in sa;
    unsigned padding;
    int fd;
    int result = -1;
    const char *msg;

    fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
    if (fd < 0) {
        msg = "socket(%s)";
        goto ret_msg;
    }
    setsockopt_reuseaddr(fd);

    memset(&sa, 0, sizeof(sa));
    sa.sin_family = AF_INET;
    sa.sin_port = htons(source_port);
    sa.sin_addr.s_addr = source_nip;
    if (bind(fd, (struct sockaddr *)&sa, sizeof(sa)) == -1) {
        msg = "bind(%s)";
        goto ret_close;
    }

    memset(&sa, 0, sizeof(sa));
    sa.sin_family = AF_INET;
    sa.sin_port = htons(dest_port);
    sa.sin_addr.s_addr = dest_nip;
    if (connect(fd, (struct sockaddr *)&sa, sizeof(sa)) == -1) {
        msg = "connect";
        goto ret_close;
    }

    udhcp_dump_packet(dhcp_pkt);
    padding = DHCP_OPTIONS_BUFSIZE - 1 - udhcp_end_option(dhcp_pkt->options);
    if (padding > DHCP_SIZE - 300)
        padding = DHCP_SIZE - 300;
    result = safe_write(fd, dhcp_pkt, DHCP_SIZE - padding);
    msg = "write";
 ret_close:
    close(fd);
    if (result < 0) {
 ret_msg:
        bb_perror_msg(msg, "UDP");
    }
    return result;
}