net: sockets: Manage TCP receive window

As we buffer incoming packets in receive callbacks, we must decrease
receive window to avoid situation that incoming stream for one socket
uses up all buffers in the system and causes deadlock. Once user app
consumes queued data using recv() call, we increase window again.

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>

subsys/net/lib/sockets/sockets.c

@@ -141,6 +141,10 @@ static void zsock_received_cb(struct net_context *ctx, struct net_pkt *pkt,
 	header_len = net_pkt_appdata(pkt) - pkt->frags->data;
 	net_buf_pull(pkt->frags, header_len);
 
+	if (net_context_get_type(ctx) == SOCK_STREAM) {
+		net_context_update_recv_wnd(ctx, -net_pkt_appdatalen(pkt));
+	}
+
 	k_fifo_put(&ctx->recv_q, pkt);
 }
 
@@ -311,6 +315,8 @@ static inline ssize_t zsock_recv_stream(struct net_context *ctx, void *buf, size
 		}
 	} while (recv_len == 0);
 
+	net_context_update_recv_wnd(ctx, recv_len);
+
 	return recv_len;
 }