samples/net/mbedtls_dtlsserver/src/dtls_server.c - third_party/github/zephyrproject-rtos/zephyr - Git at Google

 /*  Minimal DTLS server.
  *  (Meant to be used with config-threadnet.h)
  *
  *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
  *
  *  SPDX-License-Identifier: Apache-2.0
  *
  *  This file is part of mbed TLS (https://tls.mbed.org)
  */

 #include <zephyr.h>
 #include <stdio.h>

 #include <errno.h>
 #include <misc/printk.h>

 #if !defined(CONFIG_MBEDTLS_CFG_FILE)
 #include "mbedtls/config.h"
 #else
 #include CONFIG_MBEDTLS_CFG_FILE
 #endif

 #if defined(MBEDTLS_PLATFORM_C)
 #include "mbedtls/platform.h"
 #else
 #include <stdlib.h>
 #define mbedtls_time_t       time_t
 #define MBEDTLS_EXIT_SUCCESS EXIT_SUCCESS
 #define MBEDTLS_EXIT_FAILURE EXIT_FAILURE
 #endif

 #include <string.h>
 #include <net/net_context.h>
 #include <net/net_if.h>
 #include "udp.h"
 #include "udp_cfg.h"

 #include "mbedtls/net.h"
 #include "mbedtls/ssl.h"
 #include "mbedtls/entropy.h"
 #include "mbedtls/ctr_drbg.h"
 #include "mbedtls/ssl_cookie.h"

 #if defined(MBEDTLS_DEBUG_C)
 #include "mbedtls/debug.h"
 #endif

 #if defined(MBEDTLS_MEMORY_BUFFER_ALLOC_C)
 #include "mbedtls/memory_buffer_alloc.h"
 static unsigned char heap[20480];
 #endif

 #define DEBUG_THRESHOLD 0
 /*
  * Hardcoded values for server host and port
  */

 const char *pers = "dtsl_server";

 #if defined(MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED)
 #define ECJPAKE_PW_SIZE 6
 const unsigned char ecjpake_pw[ECJPAKE_PW_SIZE] = "passwd";
 #endif

 struct dtls_timing_context {
 	u32_t snapshot;
 	u32_t int_ms;
 	u32_t fin_ms;
 };

 static void my_debug(void *ctx, int level,
 		     const char *file, int line, const char *str)
 {
 	const char *p, *basename;

 	ARG_UNUSED(ctx);

 	/* Extract basename from file */
 	for (p = basename = file; *p != '\0'; p++) {
 		if (*p == '/' || *p == '\\') {
 			basename = p + 1;
 		}

 	}

 	mbedtls_printf("%s:%04d: |%d| %s", basename, line, level, str);
 }

 void dtls_timing_set_delay(void *data, u32_t int_ms, u32_t fin_ms)
 {
 	struct dtls_timing_context *ctx = (struct dtls_timing_context *)data;

 	ctx->int_ms = int_ms;
 	ctx->fin_ms = fin_ms;

 	if (fin_ms != 0) {
 		ctx->snapshot = k_uptime_get_32();
 	}
 }

 int dtls_timing_get_delay(void *data)
 {
 	struct dtls_timing_context *ctx = (struct dtls_timing_context *)data;
 	unsigned long elapsed_ms;

 	if (ctx->fin_ms == 0) {
 		return -1;
 	}

 	elapsed_ms = k_uptime_get_32() - ctx->snapshot;

 	if (elapsed_ms >= ctx->fin_ms) {
 		return 2;
 	}

 	if (elapsed_ms >= ctx->int_ms) {
 		return 1;
 	}

 	return 0;
 }

 static int entropy_source(void *data, unsigned char *output, size_t len,
 			  size_t *olen)
 {
 	u32_t seed;

 	ARG_UNUSED(data);

 	seed = sys_rand32_get();

 	if (len > sizeof(seed)) {
 		len = sizeof(seed);
 	}

 	memcpy(output, &seed, len);

 	*olen = len;

 	return 0;
 }

 unsigned char payload[256];

 void dtls_server(void)
 {
 	int len, ret = 0;
 	struct udp_context ctx;
 	struct dtls_timing_context timer;

 	mbedtls_ssl_cookie_ctx cookie_ctx;
 	mbedtls_entropy_context entropy;
 	mbedtls_ctr_drbg_context ctr_drbg;
 	mbedtls_ssl_context ssl;
 	mbedtls_ssl_config conf;

 	mbedtls_ctr_drbg_init(&ctr_drbg);

 	mbedtls_platform_set_printf(printk);

 #if defined(MBEDTLS_DEBUG_C)
 	mbedtls_debug_set_threshold(DEBUG_THRESHOLD);
 #endif

 	/*
 	 * Initialize and setup
 	 */
 	mbedtls_ssl_init(&ssl);
 	mbedtls_ssl_config_init(&conf);

 	mbedtls_printf("\n  . Seeding the random number generator...");
 	mbedtls_entropy_init(&entropy);
 	mbedtls_entropy_add_source(&entropy, entropy_source, NULL,
 				   MBEDTLS_ENTROPY_MAX_GATHER,
 				   MBEDTLS_ENTROPY_SOURCE_STRONG);

 	ret = mbedtls_ctr_drbg_seed(&ctr_drbg, mbedtls_entropy_func, &entropy,
 				    (const unsigned char *)pers, strlen(pers));
 	if (ret != 0) {
 		mbedtls_printf
 		    (" failed\n  ! mbedtls_ctr_drbg_seed returned -0x%x\n",
 		     -ret);
 		goto exit;
 	}

 	mbedtls_printf(" ok\n");

 	mbedtls_printf("  . Setting up the DTLS structure...");
 	ret = mbedtls_ssl_config_defaults(&conf,
 					  MBEDTLS_SSL_IS_SERVER,
 					  MBEDTLS_SSL_TRANSPORT_DATAGRAM,
 					  MBEDTLS_SSL_PRESET_DEFAULT);
 	if (ret != 0) {
 		mbedtls_printf(" failed! returned -0x%x\n\n", -ret);
 		goto exit;
 	}

 /* Modify this to change the default timeouts for the DTLS handshake */
 /*        mbedtls_ssl_conf_handshake_timeout( &conf, min, max ); */

 	mbedtls_ssl_conf_rng(&conf, mbedtls_ctr_drbg_random, &ctr_drbg);
 	mbedtls_ssl_conf_dbg(&conf, my_debug, NULL);

 #if defined(MBEDTLS_MEMORY_BUFFER_ALLOC_C)
 	mbedtls_memory_buffer_alloc_init(heap, sizeof(heap));
 #endif
 	ret = mbedtls_ssl_cookie_setup(&cookie_ctx, mbedtls_ctr_drbg_random,
 				       &ctr_drbg);
 	if (ret != 0) {
 		printf(" failed\n ! mbedtls_ssl_cookie_setup returned -0x%x\n",
 		       -ret);
 		goto exit;
 	}

 	mbedtls_ssl_conf_dtls_cookies(&conf, mbedtls_ssl_cookie_write,
 				      mbedtls_ssl_cookie_check, &cookie_ctx);

 	ret = mbedtls_ssl_setup(&ssl, &conf);
 	if (ret != 0) {
 		mbedtls_printf
 		    (" failed\n  ! mbedtls_ssl_setup returned -0x%x\n", -ret);
 		goto exit;
 	}

 	mbedtls_printf(" ok\n");

 	/*
 	 * Start the connection
 	 */

 	mbedtls_printf("  . Setting connection\n");

 	ret = udp_init(&ctx);
 	if (ret != 0) {
 		mbedtls_printf(" failed! udp_init returned -0x%x\n", -ret);
 		goto exit;
 	}

 	mbedtls_printf(" ok\n");

 reset:
 	mbedtls_ssl_session_reset(&ssl);

 #if defined(MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED)
 	mbedtls_printf("  . Setting up ecjpake password ...");
 	ret = mbedtls_ssl_set_hs_ecjpake_password(&ssl, ecjpake_pw,
 						  ECJPAKE_PW_SIZE);
 	if (ret != 0) {
 		mbedtls_printf(" failed! set ecjpake password returned -%d\n\n",
 			       -ret);
 		goto exit;
 	}
 #endif
 	mbedtls_printf(" ok\n");

 	mbedtls_ssl_set_timer_cb(&ssl, &timer, dtls_timing_set_delay,
 				 dtls_timing_get_delay);

 	mbedtls_ssl_set_bio(&ssl, &ctx, udp_tx, udp_rx, NULL);

 	/* For HelloVerifyRequest cookies */
 	ctx.client_id = (char)ctx.remaining;

 	ret = mbedtls_ssl_set_client_transport_id(&ssl, &ctx.client_id,
 						  sizeof(char));
 	if (ret != 0) {
 		mbedtls_printf(" failed\n  ! "
 			       "mbedtls_ssl_set_client_transport_id()"
 			       " returned -0x%x\n\n", -ret);
 		goto exit;
 	}

 	mbedtls_printf("  . Performing the TLS handshake...");

 	do {
 		ret = mbedtls_ssl_handshake(&ssl);
 	} while (ret == MBEDTLS_ERR_SSL_WANT_READ ||
 		 ret == MBEDTLS_ERR_SSL_WANT_WRITE);

 	if (ret == MBEDTLS_ERR_SSL_HELLO_VERIFY_REQUIRED) {
 		mbedtls_printf(" hello verification requested\n");
 		ret = 0;
 		goto reset;
 	}

 	if (ret != 0) {
 		mbedtls_printf
 		    (" failed\n  ! mbedtls_ssl_handshake returned -0x%x\n",
 		     -ret);
 		goto reset;
 	}

 	mbedtls_printf(" ok\n");

 	do {
 		/* Read the request */
 		mbedtls_printf("  < Read from client:");
 		len = sizeof(payload) - 1;
 		memset(payload, 0, sizeof(payload));
 		ret = mbedtls_ssl_read(&ssl, payload, len);

 		if (ret == MBEDTLS_ERR_SSL_WANT_READ ||
 		    ret == MBEDTLS_ERR_SSL_WANT_WRITE) {
 			continue;
 		}

 		if (ret <= 0) {
 			switch (ret) {
 			case MBEDTLS_ERR_SSL_TIMEOUT:
 				mbedtls_printf(" timeout\n");
 				goto reset;

 			case MBEDTLS_ERR_SSL_PEER_CLOSE_NOTIFY:
 				mbedtls_printf(" connection was closed"
 					       " gracefully\n");
 				ret = 0;
 				goto close_notify;

 			default:
 				mbedtls_printf(" mbedtls_ssl_read"
 					       " returned -0x%x\n", -ret);
 				goto reset;
 			}
 		}

 		len = ret;
 		mbedtls_printf(" %d bytes read\n\n%s\n\n", len, payload);

 		/* Write the response */
 		mbedtls_printf("  > Write to client:");

 		do {
 			ret = mbedtls_ssl_write(&ssl, payload, len);
 		} while (ret == MBEDTLS_ERR_SSL_WANT_READ ||
 			 ret == MBEDTLS_ERR_SSL_WANT_WRITE);

 		if (ret < 0) {
 			mbedtls_printf(" failed\n  ! mbedtls_ssl_write"
 				       " returned -%d\n\n", -ret);
 			goto exit;
 		}

 		len = ret;
 		mbedtls_printf(" %d bytes written\n\n%s\n\n", len, payload);
 	} while (1);

 close_notify:
 	mbedtls_printf("  . Closing the connection...");
 	/* No error checking, the connection might be closed already */
 	do {
 		ret = mbedtls_ssl_close_notify(&ssl);
 	} while (ret == MBEDTLS_ERR_SSL_WANT_WRITE);
 	ret = 0;
 	mbedtls_printf(" done\n");
 	goto reset;

 exit:
 	mbedtls_ssl_free(&ssl);
 	mbedtls_ssl_config_free(&conf);
 	mbedtls_ctr_drbg_free(&ctr_drbg);
 	mbedtls_entropy_free(&entropy);
 }

 #define STACK_SIZE		8192
 u8_t stack[STACK_SIZE];
 static struct k_thread dtls_thread;

 static inline int init_app(void)
 {
 #if defined(CONFIG_NET_IPV6)
 #if defined(CONFIG_NET_APP_MY_IPV6_ADDR)
 	if (net_addr_pton(AF_INET6, CONFIG_NET_APP_MY_IPV6_ADDR,
 			  &server_addr) < 0) {
 		mbedtls_printf("Invalid IPv6 address %s",
 			       CONFIG_NET_APP_MY_IPV6_ADDR);
 	}
 #endif
 	if (!net_if_ipv6_addr_add(net_if_get_default(), &server_addr,
 				  NET_ADDR_MANUAL, 0)) {
 		return -EIO;
 	}

 	net_if_ipv6_maddr_add(net_if_get_default(), &mcast_addr);

 #else
 #if defined(CONFIG_NET_APP_MY_IPV4_ADDR)
 	if (net_addr_pton(AF_INET, CONFIG_NET_APP_MY_IPV4_ADDR,
 			  &server_addr) < 0) {
 		mbedtls_printf("Invalid IPv4 address %s",
 			       CONFIG_NET_APP_MY_IPV4_ADDR);
 	}
 #endif

 	if (!net_if_ipv4_addr_add(net_if_get_default(), &server_addr,
 				  NET_ADDR_MANUAL, 0)) {
 		return -EIO;
 	}
 #endif
 	return 0;
 }

 void main(void)
 {
 	if (init_app() != 0) {
 		printf("Cannot initialize network\n");
 		return;
 	}

 	k_thread_create(&dtls_thread, stack, STACK_SIZE,
 			(k_thread_entry_t) dtls_server,
 			NULL, NULL, NULL, K_PRIO_COOP(7), 0, 0);
 }
	/* Minimal DTLS server.
	* (Meant to be used with config-threadnet.h)
	*
	* Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
	*
	* SPDX-License-Identifier: Apache-2.0
	*
	* This file is part of mbed TLS (https://tls.mbed.org)
	*/

	#include <zephyr.h>
	#include <stdio.h>

	#include <errno.h>
	#include <misc/printk.h>

	#if !defined(CONFIG_MBEDTLS_CFG_FILE)
	#include "mbedtls/config.h"
	#else
	#include CONFIG_MBEDTLS_CFG_FILE
	#endif

	#if defined(MBEDTLS_PLATFORM_C)
	#include "mbedtls/platform.h"
	#else
	#include <stdlib.h>
	#define mbedtls_time_t time_t
	#define MBEDTLS_EXIT_SUCCESS EXIT_SUCCESS
	#define MBEDTLS_EXIT_FAILURE EXIT_FAILURE
	#endif

	#include <string.h>
	#include <net/net_context.h>
	#include <net/net_if.h>
	#include "udp.h"
	#include "udp_cfg.h"

	#include "mbedtls/net.h"
	#include "mbedtls/ssl.h"
	#include "mbedtls/entropy.h"
	#include "mbedtls/ctr_drbg.h"
	#include "mbedtls/ssl_cookie.h"

	#if defined(MBEDTLS_DEBUG_C)
	#include "mbedtls/debug.h"
	#endif

	#if defined(MBEDTLS_MEMORY_BUFFER_ALLOC_C)
	#include "mbedtls/memory_buffer_alloc.h"
	static unsigned char heap[20480];
	#endif

	#define DEBUG_THRESHOLD 0
	/*
	* Hardcoded values for server host and port
	*/

	const char *pers = "dtsl_server";

	#if defined(MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED)
	#define ECJPAKE_PW_SIZE 6
	const unsigned char ecjpake_pw[ECJPAKE_PW_SIZE] = "passwd";
	#endif

	struct dtls_timing_context {
	u32_t snapshot;
	u32_t int_ms;
	u32_t fin_ms;
	};

	static void my_debug(void *ctx, int level,
	const char file, int line, const char str)
	{
	const char p, basename;

	ARG_UNUSED(ctx);

	/* Extract basename from file */
	for (p = basename = file; *p != '\0'; p++) {
	if (p == '/' \|\| p == '\\') {
	basename = p + 1;
	}

	}

	mbedtls_printf("%s:%04d: \|%d\| %s", basename, line, level, str);
	}

	void dtls_timing_set_delay(void *data, u32_t int_ms, u32_t fin_ms)
	{
	struct dtls_timing_context ctx = (struct dtls_timing_context )data;

	ctx->int_ms = int_ms;
	ctx->fin_ms = fin_ms;

	if (fin_ms != 0) {
	ctx->snapshot = k_uptime_get_32();
	}
	}

	int dtls_timing_get_delay(void *data)
	{
	struct dtls_timing_context ctx = (struct dtls_timing_context )data;
	unsigned long elapsed_ms;

	if (ctx->fin_ms == 0) {
	return -1;
	}

	elapsed_ms = k_uptime_get_32() - ctx->snapshot;

	if (elapsed_ms >= ctx->fin_ms) {
	return 2;
	}

	if (elapsed_ms >= ctx->int_ms) {
	return 1;
	}

	return 0;
	}

	static int entropy_source(void data, unsigned char output, size_t len,
	size_t *olen)
	{
	u32_t seed;

	ARG_UNUSED(data);

	seed = sys_rand32_get();

	if (len > sizeof(seed)) {
	len = sizeof(seed);
	}

	memcpy(output, &seed, len);

	*olen = len;

	return 0;
	}

	unsigned char payload[256];

	void dtls_server(void)
	{
	int len, ret = 0;
	struct udp_context ctx;
	struct dtls_timing_context timer;

	mbedtls_ssl_cookie_ctx cookie_ctx;
	mbedtls_entropy_context entropy;
	mbedtls_ctr_drbg_context ctr_drbg;
	mbedtls_ssl_context ssl;
	mbedtls_ssl_config conf;

	mbedtls_ctr_drbg_init(&ctr_drbg);

	mbedtls_platform_set_printf(printk);

	#if defined(MBEDTLS_DEBUG_C)
	mbedtls_debug_set_threshold(DEBUG_THRESHOLD);
	#endif

	/*
	* Initialize and setup
	*/
	mbedtls_ssl_init(&ssl);
	mbedtls_ssl_config_init(&conf);

	mbedtls_printf("\n . Seeding the random number generator...");
	mbedtls_entropy_init(&entropy);
	mbedtls_entropy_add_source(&entropy, entropy_source, NULL,
	MBEDTLS_ENTROPY_MAX_GATHER,
	MBEDTLS_ENTROPY_SOURCE_STRONG);

	ret = mbedtls_ctr_drbg_seed(&ctr_drbg, mbedtls_entropy_func, &entropy,
	(const unsigned char *)pers, strlen(pers));
	if (ret != 0) {
	mbedtls_printf
	(" failed\n ! mbedtls_ctr_drbg_seed returned -0x%x\n",
	-ret);
	goto exit;
	}

	mbedtls_printf(" ok\n");

	mbedtls_printf(" . Setting up the DTLS structure...");
	ret = mbedtls_ssl_config_defaults(&conf,
	MBEDTLS_SSL_IS_SERVER,
	MBEDTLS_SSL_TRANSPORT_DATAGRAM,
	MBEDTLS_SSL_PRESET_DEFAULT);
	if (ret != 0) {
	mbedtls_printf(" failed! returned -0x%x\n\n", -ret);
	goto exit;
	}

	/* Modify this to change the default timeouts for the DTLS handshake */
	/* mbedtls_ssl_conf_handshake_timeout( &conf, min, max ); */

	mbedtls_ssl_conf_rng(&conf, mbedtls_ctr_drbg_random, &ctr_drbg);
	mbedtls_ssl_conf_dbg(&conf, my_debug, NULL);

	#if defined(MBEDTLS_MEMORY_BUFFER_ALLOC_C)
	mbedtls_memory_buffer_alloc_init(heap, sizeof(heap));
	#endif
	ret = mbedtls_ssl_cookie_setup(&cookie_ctx, mbedtls_ctr_drbg_random,
	&ctr_drbg);
	if (ret != 0) {
	printf(" failed\n ! mbedtls_ssl_cookie_setup returned -0x%x\n",
	-ret);
	goto exit;
	}

	mbedtls_ssl_conf_dtls_cookies(&conf, mbedtls_ssl_cookie_write,
	mbedtls_ssl_cookie_check, &cookie_ctx);

	ret = mbedtls_ssl_setup(&ssl, &conf);
	if (ret != 0) {
	mbedtls_printf
	(" failed\n ! mbedtls_ssl_setup returned -0x%x\n", -ret);
	goto exit;
	}

	mbedtls_printf(" ok\n");

	/*
	* Start the connection
	*/

	mbedtls_printf(" . Setting connection\n");

	ret = udp_init(&ctx);
	if (ret != 0) {
	mbedtls_printf(" failed! udp_init returned -0x%x\n", -ret);
	goto exit;
	}

	mbedtls_printf(" ok\n");

	reset:
	mbedtls_ssl_session_reset(&ssl);

	#if defined(MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED)
	mbedtls_printf(" . Setting up ecjpake password ...");
	ret = mbedtls_ssl_set_hs_ecjpake_password(&ssl, ecjpake_pw,
	ECJPAKE_PW_SIZE);
	if (ret != 0) {
	mbedtls_printf(" failed! set ecjpake password returned -%d\n\n",
	-ret);
	goto exit;
	}
	#endif
	mbedtls_printf(" ok\n");

	mbedtls_ssl_set_timer_cb(&ssl, &timer, dtls_timing_set_delay,
	dtls_timing_get_delay);

	mbedtls_ssl_set_bio(&ssl, &ctx, udp_tx, udp_rx, NULL);

	/* For HelloVerifyRequest cookies */
	ctx.client_id = (char)ctx.remaining;

	ret = mbedtls_ssl_set_client_transport_id(&ssl, &ctx.client_id,
	sizeof(char));
	if (ret != 0) {
	mbedtls_printf(" failed\n ! "
	"mbedtls_ssl_set_client_transport_id()"
	" returned -0x%x\n\n", -ret);
	goto exit;
	}

	mbedtls_printf(" . Performing the TLS handshake...");

	do {
	ret = mbedtls_ssl_handshake(&ssl);
	} while (ret == MBEDTLS_ERR_SSL_WANT_READ \|\|
	ret == MBEDTLS_ERR_SSL_WANT_WRITE);

	if (ret == MBEDTLS_ERR_SSL_HELLO_VERIFY_REQUIRED) {
	mbedtls_printf(" hello verification requested\n");
	ret = 0;
	goto reset;
	}

	if (ret != 0) {
	mbedtls_printf
	(" failed\n ! mbedtls_ssl_handshake returned -0x%x\n",
	-ret);
	goto reset;
	}

	mbedtls_printf(" ok\n");

	do {
	/* Read the request */
	mbedtls_printf(" < Read from client:");
	len = sizeof(payload) - 1;
	memset(payload, 0, sizeof(payload));
	ret = mbedtls_ssl_read(&ssl, payload, len);

	if (ret == MBEDTLS_ERR_SSL_WANT_READ \|\|
	ret == MBEDTLS_ERR_SSL_WANT_WRITE) {
	continue;
	}

	if (ret <= 0) {
	switch (ret) {
	case MBEDTLS_ERR_SSL_TIMEOUT:
	mbedtls_printf(" timeout\n");
	goto reset;

	case MBEDTLS_ERR_SSL_PEER_CLOSE_NOTIFY:
	mbedtls_printf(" connection was closed"
	" gracefully\n");
	ret = 0;
	goto close_notify;

	default:
	mbedtls_printf(" mbedtls_ssl_read"
	" returned -0x%x\n", -ret);
	goto reset;
	}
	}

	len = ret;
	mbedtls_printf(" %d bytes read\n\n%s\n\n", len, payload);

	/* Write the response */
	mbedtls_printf(" > Write to client:");

	do {
	ret = mbedtls_ssl_write(&ssl, payload, len);
	} while (ret == MBEDTLS_ERR_SSL_WANT_READ \|\|
	ret == MBEDTLS_ERR_SSL_WANT_WRITE);

	if (ret < 0) {
	mbedtls_printf(" failed\n ! mbedtls_ssl_write"
	" returned -%d\n\n", -ret);
	goto exit;
	}

	len = ret;
	mbedtls_printf(" %d bytes written\n\n%s\n\n", len, payload);
	} while (1);

	close_notify:
	mbedtls_printf(" . Closing the connection...");
	/* No error checking, the connection might be closed already */
	do {
	ret = mbedtls_ssl_close_notify(&ssl);
	} while (ret == MBEDTLS_ERR_SSL_WANT_WRITE);
	ret = 0;
	mbedtls_printf(" done\n");
	goto reset;

	exit:
	mbedtls_ssl_free(&ssl);
	mbedtls_ssl_config_free(&conf);
	mbedtls_ctr_drbg_free(&ctr_drbg);
	mbedtls_entropy_free(&entropy);
	}

	#define STACK_SIZE 8192
	u8_t stack[STACK_SIZE];
	static struct k_thread dtls_thread;

	static inline int init_app(void)
	{
	#if defined(CONFIG_NET_IPV6)
	#if defined(CONFIG_NET_APP_MY_IPV6_ADDR)
	if (net_addr_pton(AF_INET6, CONFIG_NET_APP_MY_IPV6_ADDR,
	&server_addr) < 0) {
	mbedtls_printf("Invalid IPv6 address %s",
	CONFIG_NET_APP_MY_IPV6_ADDR);
	}
	#endif
	if (!net_if_ipv6_addr_add(net_if_get_default(), &server_addr,
	NET_ADDR_MANUAL, 0)) {
	return -EIO;
	}

	net_if_ipv6_maddr_add(net_if_get_default(), &mcast_addr);

	#else
	#if defined(CONFIG_NET_APP_MY_IPV4_ADDR)
	if (net_addr_pton(AF_INET, CONFIG_NET_APP_MY_IPV4_ADDR,
	&server_addr) < 0) {
	mbedtls_printf("Invalid IPv4 address %s",
	CONFIG_NET_APP_MY_IPV4_ADDR);
	}
	#endif

	if (!net_if_ipv4_addr_add(net_if_get_default(), &server_addr,
	NET_ADDR_MANUAL, 0)) {
	return -EIO;
	}
	#endif
	return 0;
	}

	void main(void)
	{
	if (init_app() != 0) {
	printf("Cannot initialize network\n");
	return;
	}

	k_thread_create(&dtls_thread, stack, STACK_SIZE,
	(k_thread_entry_t) dtls_server,
	NULL, NULL, NULL, K_PRIO_COOP(7), 0, 0);
	}