More file transfer improvements.

toxcore/net_crypto.c

@@ -2235,7 +2235,12 @@ static void send_crypto_packets(Net_Crypto *c)
                         total_resent += conn->last_num_packets_resent[ind];
                     }
 
-                    total_sent -= sum;
+                    if (sum > 0) {
+                        total_sent -= sum;
+                    } else {
+                        if (total_resent > -sum)
+                            total_resent = -sum;
+                    }
 
                     /* if queue is too big only allow resending packets. */
                     uint32_t npackets = num_packets_array(&conn->send_array);

toxcore/net_crypto.h

@@ -80,7 +80,7 @@
 
 /* Base current transfer speed on last CONGESTION_QUEUE_ARRAY_SIZE number of points taken
    at the dT defined in net_crypto.c */
-#define CONGESTION_QUEUE_ARRAY_SIZE 24
+#define CONGESTION_QUEUE_ARRAY_SIZE 12
 #define CONGESTION_LAST_SENT_ARRAY_SIZE (CONGESTION_QUEUE_ARRAY_SIZE * 2)
 
 /* Default connection ping in ms. */