[ephemient]

Are you thinking of EXTPROC/LINEMODE? There's outstanding patches to bash, telnet, and ssh to support these, which enables local line-editing that works smarter than just local echo.

TIOCPKT_IOCTL(EXTPROC) and TIOCSIG support landed in Linux kernel 2.6.36: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux....