Something I would really like to see in modern operating systems is the ability to do TCP like UDP, i.e. you bind a socket and then send and receive TCP packets

Something I would really like to see in modern operating systems is the ability to do TCP like UDP, i.e. you bind a socket and then send and receive TCP packets (everything after the ports in the TCP header) as datagrams. The problem that solves is this. Right now if you don't want to use the OS TCP implementation your choices are a) raw sockets or tun/tap or kernel drivers or something equally heavy-handed that all require privileges, or b) encapsulate in UDP. Which makes "encapsulate in UDP" a great choice until you see this: $ cat /proc/sys/net/netfilter/nf_conntrack_tcp_timeout_established 432000 $ cat /proc/sys/net/netfilter/nf_conntrack_udp_timeout_stream 180 The reason for that is because UDP is connectionless. With TCP a long timeout is reasonable because the state can be discarded before that when the middlebox sees the connection close. So if you need long-lived sessions, UDP requires you to send a lot of keepalives. But "TCP as datagrams" would let you actually look like TCP to the middlebox and get the long timeout and the ability to notify it when you're done, without requiring CAP_NET_ADMIN or similar from the OS.