Drain rx_chain before closing the connection

PUBLISHED_FROM=08eee4052dd9bbc364875a577409cb78665dee30

mongoose.c

@@ -14792,7 +14792,9 @@ struct mg_lwip_conn_state {
   /* Last SSL write size, for retries. */
   int last_ssl_write_size;
   /* Whether MG_SIG_RECV is already pending for this connection */
-  int recv_pending;
+  int recv_pending : 1;
+  /* Whether the connection is about to close, just `rx_chain` needs to drain */
+  int draining_rx_chain : 1;
 };
 
 enum mg_sig_type {
@@ -14951,7 +14953,16 @@ static err_t mg_lwip_tcp_recv_cb(void *arg, struct tcp_pcb *tpcb,
   DBG(("%p %p %u %d", nc, tpcb, (p != NULL ? p->tot_len : 0), err));
   if (p == NULL) {
     if (nc != NULL && !(nc->flags & MG_F_CLOSE_IMMEDIATELY)) {
-      mg_lwip_post_signal(MG_SIG_CLOSE_CONN, nc);
+      struct mg_lwip_conn_state *cs = (struct mg_lwip_conn_state *) nc->sock;
+      if (cs->rx_chain != NULL) {
+        /*
+         * rx_chain still contains non-consumed data, don't close the
+         * connection
+         */
+        cs->draining_rx_chain = 1;
+      } else {
+        mg_lwip_post_signal(MG_SIG_CLOSE_CONN, nc);
+      }
     } else {
       /* Tombstoned connection, do nothing. */
     }
@@ -14988,23 +14999,12 @@ static err_t mg_lwip_tcp_recv_cb(void *arg, struct tcp_pcb *tpcb,
   return ERR_OK;
 }
 
-static void mg_lwip_handle_recv_tcp(struct mg_connection *nc) {
+static void mg_lwip_consume_rx_chain_tcp(struct mg_connection *nc) {
   struct mg_lwip_conn_state *cs = (struct mg_lwip_conn_state *) nc->sock;
-
-#if MG_ENABLE_SSL
-  if (nc->flags & MG_F_SSL) {
-    if (nc->flags & MG_F_SSL_HANDSHAKE_DONE) {
-      mg_lwip_ssl_recv(nc);
-    } else {
-      mg_lwip_ssl_do_hs(nc);
-    }
-    return;
-  }
-#endif
-
   mgos_lock();
   while (cs->rx_chain != NULL && nc->recv_mbuf.len < nc->recv_mbuf_limit) {
     struct pbuf *seg = cs->rx_chain;
+
     size_t seg_len = (seg->len - cs->rx_offset);
     size_t buf_avail = (nc->recv_mbuf_limit - nc->recv_mbuf.len);
     size_t len = MIN(seg_len, buf_avail);
@@ -15027,6 +15027,21 @@ static void mg_lwip_handle_recv_tcp(struct mg_connection *nc) {
     mgos_lock();
   }
   mgos_unlock();
+}
+
+static void mg_lwip_handle_recv_tcp(struct mg_connection *nc) {
+#if MG_ENABLE_SSL
+  if (nc->flags & MG_F_SSL) {
+    if (nc->flags & MG_F_SSL_HANDSHAKE_DONE) {
+      mg_lwip_ssl_recv(nc);
+    } else {
+      mg_lwip_ssl_do_hs(nc);
+    }
+    return;
+  }
+#endif
+
+  mg_lwip_consume_rx_chain_tcp(nc);
 
   if (nc->send_mbuf.len > 0) {
     mg_lwip_mgr_schedule_poll(nc->mgr);
@@ -15647,7 +15662,7 @@ void mg_ev_mgr_lwip_process_signals(struct mg_mgr *mgr) {
         break;
       }
       case MG_SIG_CLOSE_CONN: {
-        nc->flags |= MG_F_CLOSE_IMMEDIATELY;
+        nc->flags |= MG_F_SEND_AND_CLOSE;
         mg_close_conn(nc);
         break;
       }
@@ -15758,6 +15773,19 @@ time_t mg_lwip_if_poll(struct mg_iface *iface, int timeout_ms) {
       }
       num_timers++;
     }
+
+    if (nc->sock != INVALID_SOCKET) {
+      /* Try to consume data from cs->rx_chain */
+      mg_lwip_consume_rx_chain_tcp(nc);
+
+      /*
+       * If the connection is about to close, and rx_chain is finally empty,
+       * send the MG_SIG_CLOSE_CONN signal
+       */
+      if (cs->draining_rx_chain && cs->rx_chain == NULL) {
+        mg_lwip_post_signal(MG_SIG_CLOSE_CONN, nc);
+      }
+    }
   }
 #if 0
   DBG(("end poll @%u, %d conns, %d timers (min %u), next in %d ms",