/* Shared library add-on to ip6tables to add Hop-by-Hop and Dst headers support. */
#include <stdio.h>
#include <netdb.h>
#include <string.h>
#include <stdlib.h>
#include <getopt.h>
#include <errno.h>
#include <ip6tables.h>
#include <linux/netfilter_ipv6/ip6t_opts.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>

#ifdef HOPBYHOP
#define UNAME "HBH"
#define LNAME "hbh"
#else
#define UNAME "DST"
#define LNAME "dst"
#endif

/* Function which prints out usage message. */
static void
help(void)
{
	printf(
UNAME " v%s options:\n"
" --" LNAME "-len [!] length           total length of this header\n"
" --" LNAME "-opts TYPE[:LEN][,TYPE[:LEN]...] \n"
"                               Options and its length (list, max: %d)\n", 
IPTABLES_VERSION, IP6T_OPTS_OPTSNR);
}

static struct option opts[] = {
	{ .name = LNAME "-len",        .has_arg = 1, .flag = 0, .val = '1' },
	{ .name = LNAME "-opts",       .has_arg = 1, .flag = 0, .val = '2' },
	{ .name = LNAME "-not-strict", .has_arg = 1, .flag = 0, .val = '3' },
	{ .name = 0 }
};

static u_int32_t
parse_opts_num(const char *idstr, const char *typestr)
{
	unsigned long int id;
	char* ep;

	id = strtoul(idstr, &ep, 0);

	if ( idstr == ep ) {
		exit_error(PARAMETER_PROBLEM,
			   UNAME " no valid digits in %s `%s'", typestr, idstr);
	}
	if ( id == ULONG_MAX  && errno == ERANGE ) {
		exit_error(PARAMETER_PROBLEM,
			   "%s `%s' specified too big: would overflow",
			   typestr, idstr);
	}
	if ( *idstr != '\0'  && *ep != '\0' ) {
		exit_error(PARAMETER_PROBLEM,
			   UNAME " error parsing %s `%s'", typestr, idstr);
	}
	return (u_int32_t) id;
}

static int
parse_options(const char *optsstr, u_int16_t *opts)
{
        char *buffer, *cp, *next, *range;
        unsigned int i;
	
	buffer = strdup(optsstr);
        if (!buffer)
		exit_error(OTHER_PROBLEM, "strdup failed");
			
        for (cp = buffer, i = 0; cp && i < IP6T_OPTS_OPTSNR; cp = next, i++)
        {
                next = strchr(cp, ',');

                if (next)
			*next++='\0';

                range = strchr(cp, ':');

                if (range) {
                        if (i == IP6T_OPTS_OPTSNR-1)
                                exit_error(PARAMETER_PROBLEM,
                                           "too many ports specified");
                        *range++ = '\0';
                }

                opts[i] = (u_int16_t)((parse_opts_num(cp,"opt") & 0x000000FF)<<8); 
                if (range) {
			if (opts[i] == 0)
        			exit_error(PARAMETER_PROBLEM,
					"PAD0 hasn't got length");
                        opts[i] |= (u_int16_t)(parse_opts_num(range,"length") &
					0x000000FF);
                } else
                        opts[i] |= (0x00FF);

#ifdef DEBUG
		printf("opts str: %s %s\n", cp, range);
		printf("opts opt: %04X\n", opts[i]);
#endif
	}

        if (cp)
		exit_error(PARAMETER_PROBLEM, "too many addresses specified");

	free(buffer);

#ifdef DEBUG
	printf("addr nr: %d\n", i);
#endif

	return i;
}

/* Initialize the match. */
static void
init(struct xt_entry_match *m, unsigned int *nfcache)
{
	struct ip6t_opts *optinfo = (struct ip6t_opts *)m->data;

	optinfo->hdrlen = 0;
	optinfo->flags = 0;
	optinfo->invflags = 0;
	optinfo->optsnr = 0;
}

/* Function which parses command options; returns true if it
   ate an option */
static int
parse(int c, char **argv, int invert, unsigned int *flags,
      const struct ip6t_entry *entry,
      unsigned int *nfcache,
      struct xt_entry_match **match)
{
	struct ip6t_opts *optinfo = (struct ip6t_opts *)(*match)->data;

	switch (c) {
	case '1':
		if (*flags & IP6T_OPTS_LEN)
			exit_error(PARAMETER_PROBLEM,
				   "Only one `--" LNAME "-len' allowed");
		check_inverse(optarg, &invert, &optind, 0);
		optinfo->hdrlen = parse_opts_num(argv[optind-1], "length");
		if (invert)
			optinfo->invflags |= IP6T_OPTS_INV_LEN;
		optinfo->flags |= IP6T_OPTS_LEN;
		*flags |= IP6T_OPTS_LEN;
		break;
	case '2':
		if (*flags & IP6T_OPTS_OPTS)
			exit_error(PARAMETER_PROBLEM,
				   "Only one `--" LNAME "-opts' allowed");
                check_inverse(optarg, &invert, &optind, 0);
                if (invert)
                        exit_error(PARAMETER_PROBLEM,
				" '!' not allowed with `--" LNAME "-opts'");
		optinfo->optsnr = parse_options(argv[optind-1], optinfo->opts);
		optinfo->flags |= IP6T_OPTS_OPTS;
		*flags |= IP6T_OPTS_OPTS;
		break;
	case '3':
		if (*flags & IP6T_OPTS_NSTRICT)
			exit_error(PARAMETER_PROBLEM,
				   "Only one `--" LNAME "-not-strict' allowed");
		if ( !(*flags & IP6T_OPTS_OPTS) )
			exit_error(PARAMETER_PROBLEM,
				   "`--" LNAME "-opts ...' required before `--"
				   LNAME "-not-strict'");
		optinfo->flags |= IP6T_OPTS_NSTRICT;
		*flags |= IP6T_OPTS_NSTRICT;
		break;
	default:
		return 0;
	}

	return 1;
}

/* Final check; we don't care. */
static void
final_check(unsigned int flags)
{
}

static void
print_options(int optsnr, u_int16_t *optsp)
{
	unsigned int i;

	for(i = 0; i < optsnr; i++) {
		printf("%d", (optsp[i] & 0xFF00) >> 8);

		if ((optsp[i] & 0x00FF) != 0x00FF)
			printf(":%d", (optsp[i] & 0x00FF));

		printf("%c", (i != optsnr - 1) ? ',' : ' ');
	}
}

/* Prints out the union ip6t_matchinfo. */
static void
print(const struct ip6t_ip6 *ip,
      const struct xt_entry_match *match, int numeric)
{
	const struct ip6t_opts *optinfo = (struct ip6t_opts *)match->data;

	printf(LNAME " ");
	if (optinfo->flags & IP6T_OPTS_LEN)
		printf("length:%s%u ",
			optinfo->invflags & IP6T_OPTS_INV_LEN ? "!" : "",
			optinfo->hdrlen);

	if (optinfo->flags & IP6T_OPTS_OPTS)
		printf("opts ");

	print_options(optinfo->optsnr, (u_int16_t *)optinfo->opts);

	if (optinfo->flags & IP6T_OPTS_NSTRICT)
		printf("not-strict ");

	if (optinfo->invflags & ~IP6T_OPTS_INV_MASK)
		printf("Unknown invflags: 0x%X ",
		       optinfo->invflags & ~IP6T_OPTS_INV_MASK);
}

/* Saves the union ip6t_matchinfo in parsable form to stdout. */
static void save(const struct ip6t_ip6 *ip, const struct xt_entry_match *match)
{
	const struct ip6t_opts *optinfo = (struct ip6t_opts *)match->data;

	if (optinfo->flags & IP6T_OPTS_LEN) {
		printf("--" LNAME "-len %s%u ", 
			(optinfo->invflags & IP6T_OPTS_INV_LEN) ? "! " : "", 
			optinfo->hdrlen);
	}

	if (optinfo->flags & IP6T_OPTS_OPTS)
		printf("--" LNAME "-opts ");

	print_options(optinfo->optsnr, (u_int16_t *)optinfo->opts);

	if (optinfo->flags & IP6T_OPTS_NSTRICT)
		printf("--" LNAME "-not-strict ");
}

static
struct ip6tables_match optstruct = {
	.name          = LNAME,
	.version       = IPTABLES_VERSION,
	.size          = IP6T_ALIGN(sizeof(struct ip6t_opts)),
	.userspacesize = IP6T_ALIGN(sizeof(struct ip6t_opts)),
	.help          = &help,
	.init          = &init,
	.parse         = &parse,
	.final_check   = &final_check,
	.print         = &print,
	.save          = &save,
	.extra_opts    = opts
};

void
_init(void)
{
	register_match6(&optstruct);
}