315-i-get-the-error-cannot-ioctl-tunsetiff-tun0-file-descriptor-in-bad-state-errno77 - blame None

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193f02	Samuli Seppänen	2025-02-11 11:47:26	1	# I get the error Cannot ioctl TUNSETIFF tun0: File descriptor in bad state (errno=77)
			2
			3	>>What was happening
			4	>>earlier was that I built openvpn first, then realized I needed to build
			5	>>the tun/tap kernel module, so built that and then rebuilt openvpn - but
			6	>>configure (god bless it) used the cached result of NOT finding if_tun.h.
			7	>>I cleared configure's cache and rebuilt it again - this time it found
			8	>>"tun/tap v1.4". Now I'm onto a new set of problems though. Now I get:
			9	>>
			10	>>34: Cannot ioctl TUNSETIFF tun: File descriptor in bad state (errno=77)
			11	>>
			12	>>Though I've never seen this error personally, it has been talked about
			13	>>extensively on the vtun list (another tunneling daemon that uses the TUN/TAP
			14	>>driver).
			15	>>
			16	>>Go to [http://sourceforge.net/mailarchive/forum.php?forum_id=1826](http://sourceforge.net/mailarchive/forum.php?forum_id=1826)
			17	>>
			18	>>and search for "bad state".
			19	>>
			20	>>It appears to be caused by a mismatch between the tun/tap kernel module and
			21	>>the kernel itself.
			22	>>
			23	>>What kernel version are you using?
			24	>>
			25	>>Because in versions 2.4.6 and higher, the TUN/TAP module is integral to the
			26	>>kernel -- if you try to build an external version of the module, rather than
			27	>>using the one already bundled, it will likely fail.
			28	> Also, I've read a few posts that suggest that /usr/src/linux needs to point
			29	> to headers that match the running kernel. Depending on what Sean has, it
			30	> may be worthwhile to ensure all the various versions
			31	> (kernel/headers/tunTap) all match.