Bug 3139

Summary:	Tunneling does not work on recent versions of macOS
Product:	Portable OpenSSH	Reporter:	Jamie Schnaitter <jamie.schnaitter>
Component:	Miscellaneous	Assignee:	Assigned to nobody <unassigned-bugs>
Status:	NEW ---
Severity:	normal	CC:	jamie.schnaitter
Priority:	P5
Version:	7.9p1
Hardware:	All
OS:	Mac OS X

Description Jamie Schnaitter 2020-03-20 10:34:14 AEDT

Support for it was already tenuous, as I am assuming it was using the tuntaposx http://tuntaposx.sourceforge.net/ TUN/TAP driver which appears to be defunct (it was hard to maintain and Apple is "discouraging" development of KEXTs).

Darwin and thus macOS has had for a while "user tunnel" (utun) pseudodevices, which could be a solution to this.  Several VPN packages use this on macOS to provide their functionality, but I have not found much about it in relation to OpenSSH.

utun operates in user mode and presents a socket rather than a character device.  It is pretty well described in Chapter 17 of http://newosxbook.com/MOXiI.pdf , especially from page 682 (PDF page 718)