diff --git a/lib/lwip/Makefile b/lib/lwip/Makefile
index dfcd700ca474..19e5c6897f5a 100644
--- a/lib/lwip/Makefile
+++ b/lib/lwip/Makefile
@@ -53,3 +53,6 @@ obj-y += \
 	lwip/src/core/timeouts.o \
 	lwip/src/core/udp.o \
 	lwip/src/netif/ethernet.o
+
+obj-$(CONFIG_MBEDTLS_LIB_TLS) += lwip/src/apps/altcp_tls/altcp_tls_mbedtls.o \
+	lwip/src/apps/altcp_tls/altcp_tls_mbedtls_mem.o
diff --git a/lib/lwip/lwip/src/apps/altcp_tls/altcp_tls_mbedtls.c b/lib/lwip/lwip/src/apps/altcp_tls/altcp_tls_mbedtls.c
index a8c2fc2ee2cd..ef19821b89e0 100644
--- a/lib/lwip/lwip/src/apps/altcp_tls/altcp_tls_mbedtls.c
+++ b/lib/lwip/lwip/src/apps/altcp_tls/altcp_tls_mbedtls.c
@@ -3,7 +3,7 @@
  * Application layered TCP/TLS connection API (to be used from TCPIP thread)
  *
  * This file provides a TLS layer using mbedTLS
- * 
+ *
  * This version is currently compatible with the 2.x.x branch (current LTS).
  */
 
@@ -70,7 +70,6 @@
 /* @todo: which includes are really needed? */
 #include "mbedtls/entropy.h"
 #include "mbedtls/ctr_drbg.h"
-#include "mbedtls/certs.h"
 #include "mbedtls/x509.h"
 #include "mbedtls/ssl.h"
 #include "mbedtls/net_sockets.h"
@@ -81,8 +80,6 @@
 #include "mbedtls/ssl_cache.h"
 #include "mbedtls/ssl_ticket.h"
 
-#include "mbedtls/ssl_internal.h" /* to call mbedtls_flush_output after ERR_MEM */
-
 #include <string.h>
 
 #ifndef ALTCP_MBEDTLS_ENTROPY_PTR
@@ -132,6 +129,16 @@ static err_t altcp_mbedtls_lower_recv_process(struct altcp_pcb *conn, altcp_mbed
 static err_t altcp_mbedtls_handle_rx_appldata(struct altcp_pcb *conn, altcp_mbedtls_state_t *state);
 static int altcp_mbedtls_bio_send(void *ctx, const unsigned char *dataptr, size_t size);
 
+static void
+altcp_mbedtls_flush_output(altcp_mbedtls_state_t *state)
+{
+  if (state->ssl_context.MBEDTLS_PRIVATE(out_left) != 0) {
+    int flushed = mbedtls_ssl_send_alert_message(&state->ssl_context, 0, 0);
+    if (flushed) {
+      LWIP_DEBUGF(ALTCP_MBEDTLS_DEBUG, ("mbedtls_ssl_send_alert_message failed: %d\n", flushed));
+    }
+  }
+}
 
 /* callback functions from inner/lower connection: */
 
@@ -524,14 +531,14 @@ altcp_mbedtls_lower_sent(void *arg, struct altcp_pcb *inner_conn, u16_t len)
     LWIP_ASSERT("state", state != NULL);
     LWIP_ASSERT("pcb mismatch", conn->inner_conn == inner_conn);
     /* calculate TLS overhead part to not send it to application */
-    overhead = state->overhead_bytes_adjust + state->ssl_context.out_left;
+    overhead = state->overhead_bytes_adjust + state->ssl_context.MBEDTLS_PRIVATE(out_left);
     if ((unsigned)overhead > len) {
       overhead = len;
     }
     /* remove ACKed bytes from overhead adjust counter */
     state->overhead_bytes_adjust -= len;
     /* try to send more if we failed before (may increase overhead adjust counter) */
-    mbedtls_ssl_flush_output(&state->ssl_context);
+    altcp_mbedtls_flush_output(state);
     /* remove calculated overhead from ACKed bytes len */
     app_len = len - (u16_t)overhead;
     /* update application write counter and inform application */
@@ -559,7 +566,7 @@ altcp_mbedtls_lower_poll(void *arg, struct altcp_pcb *inner_conn)
     if (conn->state) {
       altcp_mbedtls_state_t *state = (altcp_mbedtls_state_t *)conn->state;
       /* try to send more if we failed before */
-      mbedtls_ssl_flush_output(&state->ssl_context);
+      altcp_mbedtls_flush_output(state);
       if (altcp_mbedtls_handle_rx_appldata(conn, state) == ERR_ABRT) {
         return ERR_ABRT;
       }
@@ -683,7 +690,7 @@ altcp_tls_set_session(struct altcp_pcb *conn, struct altcp_tls_session *session)
   if (session && conn && conn->state) {
     altcp_mbedtls_state_t *state = (altcp_mbedtls_state_t *)conn->state;
     int ret = -1;
-    if (session->data.start)
+    if (session->data.MBEDTLS_PRIVATE(start))
       ret = mbedtls_ssl_set_session(&state->ssl_context, &session->data);
     return ret < 0 ? ERR_VAL : ERR_OK;
   }
@@ -776,7 +783,7 @@ altcp_tls_create_config(int is_server, u8_t cert_count, u8_t pkey_count, int hav
   struct altcp_tls_config *conf;
   mbedtls_x509_crt *mem;
 
-  if (TCP_WND < MBEDTLS_SSL_MAX_CONTENT_LEN) {
+  if (TCP_WND < MBEDTLS_SSL_IN_CONTENT_LEN || TCP_WND < MBEDTLS_SSL_OUT_CONTENT_LEN) {
     LWIP_DEBUGF(ALTCP_MBEDTLS_DEBUG|LWIP_DBG_LEVEL_SERIOUS,
       ("altcp_tls: TCP_WND is smaller than the RX decrypion buffer, connection RX might stall!\n"));
   }
@@ -900,7 +907,7 @@ err_t altcp_tls_config_server_add_privkey_cert(struct altcp_tls_config *config,
     return ERR_VAL;
   }
 
-  ret = mbedtls_pk_parse_key(pkey, (const unsigned char *) privkey, privkey_len, privkey_pass, privkey_pass_len);
+  ret = mbedtls_pk_parse_key(pkey, (const unsigned char *) privkey, privkey_len, privkey_pass, privkey_pass_len, mbedtls_ctr_drbg_random, &altcp_tls_entropy_rng->ctr_drbg);
   if (ret != 0) {
     LWIP_DEBUGF(ALTCP_MBEDTLS_DEBUG, ("mbedtls_pk_parse_public_key failed: %d\n", ret));
     mbedtls_x509_crt_free(srvcert);
@@ -1003,7 +1010,7 @@ altcp_tls_create_config_client_2wayauth(const u8_t *ca, size_t ca_len, const u8_
   }
 
   mbedtls_pk_init(conf->pkey);
-  ret = mbedtls_pk_parse_key(conf->pkey, privkey, privkey_len, privkey_pass, privkey_pass_len);
+  ret = mbedtls_pk_parse_key(conf->pkey, privkey, privkey_len, privkey_pass, privkey_pass_len, mbedtls_ctr_drbg_random, &altcp_tls_entropy_rng->ctr_drbg);
   if (ret != 0) {
     LWIP_DEBUGF(ALTCP_MBEDTLS_DEBUG, ("mbedtls_pk_parse_key failed: %d 0x%x\n", ret, -1*ret));
     altcp_tls_free_config(conf);
@@ -1189,7 +1196,7 @@ altcp_mbedtls_sndbuf(struct altcp_pcb *conn)
           size_t ret;
 #if defined(MBEDTLS_SSL_MAX_FRAGMENT_LENGTH)
           /* @todo: adjust ssl_added to real value related to negotiated cipher */
-          size_t max_frag_len = mbedtls_ssl_get_max_frag_len(&state->ssl_context);
+          size_t max_frag_len = mbedtls_ssl_get_max_in_record_payload(&state->ssl_context);
           max_len = LWIP_MIN(max_frag_len, max_len);
 #endif
           /* Adjust sndbuf of inner_conn with what added by SSL */
@@ -1232,9 +1239,9 @@ altcp_mbedtls_write(struct altcp_pcb *conn, const void *dataptr, u16_t len, u8_t
   /* HACK: if there is something left to send, try to flush it and only
      allow sending more if this succeeded (this is a hack because neither
      returning 0 nor MBEDTLS_ERR_SSL_WANT_WRITE worked for me) */
-  if (state->ssl_context.out_left) {
-    mbedtls_ssl_flush_output(&state->ssl_context);
-    if (state->ssl_context.out_left) {
+  if (state->ssl_context.MBEDTLS_PRIVATE(out_left)) {
+    altcp_mbedtls_flush_output(state);
+    if (state->ssl_context.MBEDTLS_PRIVATE(out_left)) {
       return ERR_MEM;
     }
   }
@@ -1284,6 +1291,8 @@ altcp_mbedtls_bio_send(void *ctx, const unsigned char *dataptr, size_t size)
   while (size_left) {
     u16_t write_len = (u16_t)LWIP_MIN(size_left, 0xFFFF);
     err_t err = altcp_write(conn->inner_conn, (const void *)dataptr, write_len, apiflags);
+    /* try to send data... */
+    altcp_output(conn->inner_conn);
     if (err == ERR_OK) {
       written += write_len;
       size_left -= write_len;
diff --git a/lib/lwip/lwip/src/core/tcp_out.c b/lib/lwip/lwip/src/core/tcp_out.c
index 64579ee5cbd8..b5d312137368 100644
--- a/lib/lwip/lwip/src/core/tcp_out.c
+++ b/lib/lwip/lwip/src/core/tcp_out.c
@@ -1255,14 +1255,6 @@ tcp_output(struct tcp_pcb *pcb)
   LWIP_ASSERT("don't call tcp_output for listen-pcbs",
               pcb->state != LISTEN);
 
-  /* First, check if we are invoked by the TCP input processing
-     code. If so, we do not output anything. Instead, we rely on the
-     input processing code to call us when input processing is done
-     with. */
-  if (tcp_input_pcb == pcb) {
-    return ERR_OK;
-  }
-
   wnd = LWIP_MIN(pcb->snd_wnd, pcb->cwnd);
 
   seg = pcb->unsent;
@@ -2036,7 +2028,7 @@ tcp_rst(const struct tcp_pcb *pcb, u32_t seqno, u32_t ackno,
         u16_t local_port, u16_t remote_port)
 {
   struct pbuf *p;
-  
+
   p = tcp_rst_common(pcb, seqno, ackno, local_ip, remote_ip, local_port, remote_port);
   if (p != NULL) {
     tcp_output_control_segment(pcb, p, local_ip, remote_ip);
diff --git a/lib/lwip/u-boot/lwipopts.h b/lib/lwip/u-boot/lwipopts.h
index 9d618625facb..88d6faf327ae 100644
--- a/lib/lwip/u-boot/lwipopts.h
+++ b/lib/lwip/u-boot/lwipopts.h
@@ -154,4 +154,10 @@
 #define MEMP_MEM_INIT			1
 #define MEM_LIBC_MALLOC			1
 
+#if defined(CONFIG_MBEDTLS_LIB_TLS)
+#define LWIP_ALTCP                      1
+#define LWIP_ALTCP_TLS                  1
+#define LWIP_ALTCP_TLS_MBEDTLS          1
+#endif
+
 #endif /* LWIP_UBOOT_LWIPOPTS_H */
