#include <stdio.h>
#include <stdint.h>
#include <netinet/in.h>

#include "dp_dhcpv6.h"
#include "dp_helpers.h"

void dp_dhcpv6_check(dp_conf *conf, unsigned char *pkt, int pktlen, int offset, unsigned char **remoteid, int *remoteidlen) {
	uint8_t msgtype = (uint8_t)pkt[offset];

	if ( conf->debug ) printf("offset=%i\n",offset);

	switch(msgtype) {
		case 12: // RELAY-FORW
		case 13: // RELAY-REPL
			offset += 2 + 16 + 16; // msg-type, hop-count, link-addr, peer-addr
			if ( conf->debug ) printf("this is a relay msg\n");
			break;
		default: // all other msgtypes
			offset += 4; // msg-type, transaction-id
	}

	if ( conf->debug ) printf("offset=%i\n",offset);

	while(offset+4<=pktlen) {
		uint16_t code = ntohs(*(uint16_t*)(pkt+offset));
		uint16_t len  = ntohs(*(uint16_t*)(pkt+offset+2));

		if ( conf->debug ) printf("code %i len %i\n", code, len);

		offset+=4;

		if ( code == 9 ) { // relay message
			if ( conf->debug ) printf("option 9, relay msg\n");
			offset+=4;
			continue;
		}

		if ( code == 1 ) { // Client identifier / DUID
			// make sure there's enough space
			if ( offset + len <= pktlen ) {
				*remoteid = pkt+offset;
				*remoteidlen = len;
				break;
			}
		}
		offset+=len;
	}
}