tcp/close: Fix clean socket closure when lignering

If so_linger option enabled, we should preferably close the socket cleanly. Only
after timeout, we give up and close it with RTS.

src/api/api_msg.c

@@ -897,7 +897,7 @@ netconn_drain(struct netconn *conn)
           /* Only tcp pcbs have an acceptmbox, so no need to check conn->type */
           /* pcb might be set to NULL already by err_tcp() */
           /* drain recvmbox */
-#if ESP_LWIP
+#if ESP_LWIP && LWIP_NETCONN_FULLDUPLEX
           newconn->flags |= NETCONN_FLAG_MBOXINVALID;
 #endif /* ESP_LWIP */
           netconn_drain(newconn);
@@ -1007,7 +1007,7 @@ lwip_netconn_do_close_internal(struct netconn *conn  WRITE_DELAYED_PARAM)
     err = ERR_OK;
     /* linger enabled/required at all? (i.e. is there untransmitted data left?) */
     if ((conn->linger >= 0) && (conn->pcb.tcp->unsent || conn->pcb.tcp->unacked)) {
-      if ((conn->linger == 0)) {
+      if (conn->linger == 0) {
         /* data left but linger prevents waiting */
         tcp_abort(tpcb);
         tpcb = NULL;
@@ -1031,7 +1031,11 @@ lwip_netconn_do_close_internal(struct netconn *conn  WRITE_DELAYED_PARAM)
     if ((err == ERR_OK) && (tpcb != NULL))
 #endif /* LWIP_SO_LINGER */
     {
-      err = tcp_close(tpcb);
+      err = tcp_close_ext(tpcb,
+#if LWIP_SO_LINGER
+                          /* don't send RST yet if linger-wait-required */ linger_wait_required ? 0 :
+#endif
+                          1);
     }
   } else {
     err = tcp_shutdown(tpcb, shut_rx, shut_tx);

src/core/dns.c

@@ -96,6 +96,9 @@
 #include "lwip/prot/dns.h"
 
 #include <string.h>
+#if ESP_DNS
+#include <stdbool.h>
+#endif
 
 /** Random generator function to create random TXIDs and source ports for queries */
 #ifndef DNS_RAND_TXID

src/core/tcp.c

@@ -482,6 +482,12 @@ tcp_close_shutdown_fin(struct tcp_pcb *pcb)
  */
 err_t
 tcp_close(struct tcp_pcb *pcb)
+{
+  return tcp_close_ext(pcb, 1);
+}
+
+err_t
+tcp_close_ext(struct tcp_pcb *pcb, u8_t rst_on_unacked_data)
 {
   LWIP_ASSERT_CORE_LOCKED();
 
@@ -495,7 +501,7 @@ tcp_close(struct tcp_pcb *pcb)
     tcp_set_flags(pcb, TF_RXCLOSED);
   }
   /* ... and close */
-  return tcp_close_shutdown(pcb, 1);
+  return tcp_close_shutdown(pcb, rst_on_unacked_data);
 }
 
 /**

src/include/lwip/tcp.h

@@ -468,6 +468,8 @@ struct tcp_pcb * tcp_listen_with_backlog(struct tcp_pcb *pcb, u8_t backlog);
 
 void             tcp_abort (struct tcp_pcb *pcb);
 err_t            tcp_close   (struct tcp_pcb *pcb);
+err_t            tcp_close_ext(struct tcp_pcb *pcb, u8_t rst_on_unacked_data);
+
 err_t            tcp_shutdown(struct tcp_pcb *pcb, int shut_rx, int shut_tx);
 
 err_t            tcp_write   (struct tcp_pcb *pcb, const void *dataptr, u16_t len,