feat: Support user specify udp packet size in config (#1794)

conf/frps_full.ini

@@ -113,6 +113,11 @@ tcp_mux = true
 # custom 404 page for HTTP requests
 # custom_404_page = /path/to/404.html
 
+# specify udp packet size, unit is byte. If not set, the default value is 1500.
+# This parameter should be same between client and server.
+# It affects the udp and sudp proxy.
+udp_packet_size = 1500
+
 [plugin.user-manager]
 addr = 127.0.0.1:9000
 path = /handler