source: MondoRescue/branches/stable/mindi-busybox/networking/udhcp/options.c@ 904

/*
 * options.c -- DHCP server option packet tools
 * Rewrite by Russ Dill <Russ.Dill@asu.edu> July 2001
 */

#include <stdlib.h>
#include <string.h>

#include "common.h"
#include "dhcpd.h"
#include "options.h"
#include "files.h"


/* supported options are easily added here */
struct dhcp_option dhcp_options[] = {
    /* name[10] flags                   code */
    {"subnet",  OPTION_IP | OPTION_REQ,         0x01},
    {"timezone",    OPTION_S32,             0x02},
    {"router",  OPTION_IP | OPTION_LIST | OPTION_REQ,   0x03},
    {"timesvr", OPTION_IP | OPTION_LIST,        0x04},
    {"namesvr", OPTION_IP | OPTION_LIST,        0x05},
    {"dns",     OPTION_IP | OPTION_LIST | OPTION_REQ,   0x06},
    {"logsvr",  OPTION_IP | OPTION_LIST,        0x07},
    {"cookiesvr",   OPTION_IP | OPTION_LIST,        0x08},
    {"lprsvr",  OPTION_IP | OPTION_LIST,        0x09},
    {"hostname",    OPTION_STRING | OPTION_REQ,     0x0c},
    {"bootsize",    OPTION_U16,             0x0d},
    {"domain",  OPTION_STRING | OPTION_REQ,     0x0f},
    {"swapsvr", OPTION_IP,              0x10},
    {"rootpath",    OPTION_STRING,              0x11},
    {"ipttl",   OPTION_U8,              0x17},
    {"mtu",     OPTION_U16,             0x1a},
    {"broadcast",   OPTION_IP | OPTION_REQ,         0x1c},
    {"nisdomain",   OPTION_STRING | OPTION_REQ,     0x28},
    {"nissrv",  OPTION_IP | OPTION_LIST | OPTION_REQ,   0x29},
    {"ntpsrv",  OPTION_IP | OPTION_LIST | OPTION_REQ,   0x2a},
    {"wins",    OPTION_IP | OPTION_LIST,        0x2c},
    {"requestip",   OPTION_IP,              0x32},
    {"lease",   OPTION_U32,             0x33},
    {"dhcptype",    OPTION_U8,              0x35},
    {"serverid",    OPTION_IP,              0x36},
    {"message", OPTION_STRING,              0x38},
    {"tftp",    OPTION_STRING,              0x42},
    {"bootfile",    OPTION_STRING,              0x43},
    {"",        0x00,               0x00}
};

/* Lengths of the different option types */
int option_lengths[] = {
    [OPTION_IP] =       4,
    [OPTION_IP_PAIR] =  8,
    [OPTION_BOOLEAN] =  1,
    [OPTION_STRING] =   1,
    [OPTION_U8] =       1,
    [OPTION_U16] =      2,
    [OPTION_S16] =      2,
    [OPTION_U32] =      4,
    [OPTION_S32] =      4
};


/* get an option with bounds checking (warning, not aligned). */
uint8_t *get_option(struct dhcpMessage *packet, int code)
{
    int i, length;
    uint8_t *optionptr;
    int over = 0, done = 0, curr = OPTION_FIELD;

    optionptr = packet->options;
    i = 0;
    length = 308;
    while (!done) {
        if (i >= length) {
            LOG(LOG_WARNING, "bogus packet, option fields too long.");
            return NULL;
        }
        if (optionptr[i + OPT_CODE] == code) {
            if (i + 1 + optionptr[i + OPT_LEN] >= length) {
                LOG(LOG_WARNING, "bogus packet, option fields too long.");
                return NULL;
            }
            return optionptr + i + 2;
        }
        switch (optionptr[i + OPT_CODE]) {
        case DHCP_PADDING:
            i++;
            break;
        case DHCP_OPTION_OVER:
            if (i + 1 + optionptr[i + OPT_LEN] >= length) {
                LOG(LOG_WARNING, "bogus packet, option fields too long.");
                return NULL;
            }
            over = optionptr[i + 3];
            i += optionptr[OPT_LEN] + 2;
            break;
        case DHCP_END:
            if (curr == OPTION_FIELD && over & FILE_FIELD) {
                optionptr = packet->file;
                i = 0;
                length = 128;
                curr = FILE_FIELD;
            } else if (curr == FILE_FIELD && over & SNAME_FIELD) {
                optionptr = packet->sname;
                i = 0;
                length = 64;
                curr = SNAME_FIELD;
            } else done = 1;
            break;
        default:
            i += optionptr[OPT_LEN + i] + 2;
        }
    }
    return NULL;
}


/* return the position of the 'end' option (no bounds checking) */
int end_option(uint8_t *optionptr)
{
    int i = 0;

    while (optionptr[i] != DHCP_END) {
        if (optionptr[i] == DHCP_PADDING) i++;
        else i += optionptr[i + OPT_LEN] + 2;
    }
    return i;
}


/* add an option string to the options (an option string contains an option code,
 * length, then data) */
int add_option_string(uint8_t *optionptr, uint8_t *string)
{
    int end = end_option(optionptr);

    /* end position + string length + option code/length + end option */
    if (end + string[OPT_LEN] + 2 + 1 >= 308) {
        LOG(LOG_ERR, "Option 0x%02x did not fit into the packet!", string[OPT_CODE]);
        return 0;
    }
    DEBUG(LOG_INFO, "adding option 0x%02x", string[OPT_CODE]);
    memcpy(optionptr + end, string, string[OPT_LEN] + 2);
    optionptr[end + string[OPT_LEN] + 2] = DHCP_END;
    return string[OPT_LEN] + 2;
}


/* add a one to four byte option to a packet */
int add_simple_option(uint8_t *optionptr, uint8_t code, uint32_t data)
{
    struct dhcp_option *dh;

    for (dh=dhcp_options; dh->code; dh++) {
        if (dh->code == code) {
            uint8_t option[6], len;

            option[OPT_CODE] = code;
            len = option_lengths[dh->flags & TYPE_MASK];
            option[OPT_LEN] = len;
            if (BB_BIG_ENDIAN) data <<= 8 * (4 - len);
            /* This memcpy is for broken processors which can't
             * handle a simple unaligned 32-bit assignment */
            memcpy(&option[OPT_DATA], &data, 4);
            return add_option_string(optionptr, option);
        }
    }

    DEBUG(LOG_ERR, "Could not add option 0x%02x", code);
    return 0;
}