#include <stdio.h>
#include <stdint.h>
#include <getopt.h>
#include <string.h>
#include <xtables.h>

#include "xt_dns_name.h"

/******************************************************************************
 ************************************ API *************************************
 ******************************************************************************/

static void dns_name_mt_help(void);
static void dns_name_mt_init(struct xt_entry_match *match);
static int  dns_name_mt_parse(int c, char **argv, int invert,
                              unsigned int *flags, const void *entry,
                              struct xt_entry_match **match);
static void dns_name_mt_check(unsigned int flags);
static void dns_name_mt_print(const void *entry,
                              const struct xt_entry_match *match, int numeric);
static void dns_name_mt_save(const void *entry,
                             const struct xt_entry_match *match);

/******************************************************************************
 *********************** MODULE SPECIFICATION STRUCTURES **********************
 ******************************************************************************/

/* module specific options */
const struct option dns_name_mt_opts[] = {
    { .name="domain", .has_arg=required_argument, .val='1' },
    { NULL },
};

/* module userspace extension vtable */
static struct xtables_match dns_name_mt_reg = {
    .version        = XTABLES_VERSION,
    .name           = "dns_name",
    .revision       = 0,
    .family         = NFPROTO_IPV4,
    .size           = XT_ALIGN(sizeof(struct xt_dns_name_mtinfo)),
    .userspacesize  = XT_ALIGN(sizeof(struct xt_dns_name_mtinfo)),
    .help           = dns_name_mt_help,
    .init           = dns_name_mt_init,
    .parse          = dns_name_mt_parse,
    .final_check    = dns_name_mt_check,
    .print          = dns_name_mt_print,
    .save           = dns_name_mt_save,
    .extra_opts     = dns_name_mt_opts,
};

/******************************************************************************
 ************************* IPTABLES MODULE CALLBACKS **************************
 ******************************************************************************/

/* dns_name_mt_help - prints help message for this module
 */
static void
dns_name_mt_help(void)
{
    printf("dns_name match options\n"
           "[!] --domain <string>\t\tQueried domain name.\n");
}

/* dns_name_mt_init - initializes our data struct fields before parsing
 *  @match : pointer to our data struct
 */
static void
dns_name_mt_init(struct xt_entry_match *match)
{
    /* match is an internal structure; we are only interested in data */
    struct xt_dns_name_mtinfo *info = (void *)match->data;

    /* zero out structure */
    memset(info, 0, sizeof(*info));
}

/* dns_name_mt_parse - called for each module-specific argument
 *  @c      : option id (see .val in dns_name_mt_opts)
 *  @argv   : argv (simple as that)
 *  @invert : 1 if user specified "!" before argument
 *  @flags  : for parser's discretionary use
 *  @entry  : ptr to an ipt_entry struct (don't care)
 *  @match  : contains pointer to our data struct (data field)
 *
 *  @return : true if option was parsed, false otherwise
 */
static int
dns_name_mt_parse(int c, char **argv, int invert, unsigned int *flags,
                  const void *entry, struct xt_entry_match **match)
{
    /* get reference to our xt_dns_name_mtinfo instance */
    struct xt_dns_name_mtinfo *info = (void *)(*match)->data;

    /* option-specific parsing */
    switch (c) {
        case '1':       /* --domain */
            /* check for multiple occurrences */
            if (*flags & XT_DNS_NAME)
                xtables_error(PARAMETER_PROBLEM, "xt_dns_name: "
                    "use \"--domain\" only once!");

            /* update parser flags and match criteria flags */
            *flags      |= XT_DNS_NAME;
            info->flags |= XT_DNS_NAME;

            /* check for match rule inversion */
            if (invert)
                info->flags |= XT_DNS_NAME_INV;

            /* initalize info->name                                      *
             * NOTE: argument is in global variable <optarg>             *
             * NOTE: convert the "." characters according to QNAME specs */

            /* TODO 1: initialize info->name */

            return true;
    }

    /* unknown option */
    return false;
}

/* dns_name_mt_check - verify that all required options were processed
 *  @flags : the persistent <flags> argument from dns_name_mt_parse()
 */
static void
dns_name_mt_check(unsigned int flags)
{
    if (!(flags & XT_DNS_NAME))
        xtables_error(PARAMETER_PROBLEM, "xt_dns_name: "
            "make sure to specify the \"--domain\" argument!");
}

/* dns_name_mt_print - print the match criteria fields for `iptables -L`
 *  @entry   : internal stuff (don't care)
 *  @match   : contains pointer to our data struct (data field)
 *  @numeric : do not resolve IP addresses to host names if true (don't care)
 */
static void
dns_name_mt_print(const void *entry, const struct xt_entry_match *match,
                  int numeric)
{
    const struct xt_dns_name_mtinfo *info = (void *) match->data;

    /* check for match rule reversal */
    if (info->flags & XT_DNS_NAME_INV)
        printf("! ");

    /* print domain name                                  *
     * NOTE: replace length of labels with "." characters *
     * NOTE: do NOT print a "\n" character                */

    /* TODO 2: print info->name */
}

/* dns_name_mt_save - print out arguments that generate this rule
 *  @entry : internal stuff (don't care)
 *  @match : contains pointer to our data struct (data field)
 */
static void
dns_name_mt_save(const void *entry, const struct xt_entry_match *match)
{
    const struct xt_dns_name_mtinfo *info = (void *) match->data;

    /* check for match rule reversal */
    if (info->flags & XT_DNS_NAME_INV)
        printf("! ");

    /* print "--domain" and the argument */
    printf("--domain ");

    /* TODO 3: copy paste TODO 2 here */
}

/******************************************************************************
 ************************ LIBRARY MANAGEMENT FUNCTIONS ************************
 ******************************************************************************/

/* _init - iptables library constructor
 *
 * NOTE: the '_init' symbol is expanded as a macro by iptables
 */
static void
_init(void)
{
    xtables_register_match(&dns_name_mt_reg);
}