/* common (not config, need code patch after change) */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/select.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <sys/ioctl.h>
#include <termios.h>
#include <time.h>
#include <net/if.h>
#include <fcntl.h>

#ifdef __linux__
#include <linux/if_tun.h>
#elif __OpenBSD__
#include <sys/stat.h>
#else
#error "unsupported system"
#endif

#include "shorttypes.h"
#include "sponge-bob.h"

#define ERRDIE(a, b) if ((a) == -1) perror((b)), exit(1)

#define NONCE_SZ 16
#define HMAC_SZ  16

u8  key[32];
u32 prng_state[14];


static void send_pkt
(s32 skt, void *buf, u16 sz, struct sockaddr_storage *addr){
	ssize_t res;
	u8 *nonce, *tag;

	/* nonce, tag */
	nonce = (u8*)buf + sz;
	tag = nonce + NONCE_SZ;
	duplex257_prng_rand16(prng_state, nonce);

	/* encrypt */
	duplex257_ae_encrypt(key, nonce, tag, buf, sz);
	sz += NONCE_SZ + HMAC_SZ;

	/* send */
	res = sendto(skt, buf, sz, 0,(struct sockaddr*)addr, sizeof(*addr));
	ERRDIE(res, "sendto");
	return;
}

static s32 recv_pkt
(s32 skt, void *buf, u16 sz, struct sockaddr_storage *addr){
	socklen_t skl;
	s32 res;
	u8 *nonce, *rtag;
	u8 tag[HMAC_SZ];

	/* recv */
	skl = sizeof(*addr);
	res = recvfrom(skt, buf, sz, 0, (struct sockaddr*)addr, &skl);
	ERRDIE(res, "recvfrom");

	/* nonce, recieved tag */
	rtag = buf + res - HMAC_SZ;
	nonce  = rtag - NONCE_SZ;

	/* decrypt */
	res -= NONCE_SZ + HMAC_SZ;
	duplex257_ae_decrypt(key, nonce, tag, buf, res);
	if (0 != memcmp(tag, rtag, HMAC_SZ)) return -1;

	return res;
}