Websocket buffering & FIN

[PeterR]

A websocket server might provide a partial frame (FIN=0)
Must I always buffer application side? In the old lwip days I could just hang on to the pbuf.
Seems like ethernet lib has 16K+ of buffers & so maybe I could influence the TCP/IP to buffer until FIN? Can httpd_ws_recv_frame() etc buffer (using Ethernet reserves) until FIN?
Not getting why Ethernet lib needs so much buffer when it just passes the packet to an event handler?
Guessing its all about producer/consumer queues?
Hoping to learn!

BTW I am looking to use/create a MQTT server (with permissive licence) & so multiple fragmented frames might (worse case) present a heavy RAM hit. If I can baulk on httpd_ws_recv_frame() then that might also be cool but I think I am on httpd context (& so if I wait I might block another connection).
Guess the broader Q is too understand how to make httpd & websockets async (with buffering on Ethernet until FIN).