untun interface number keeps increasing

[Orion Poplawski]

We seem to see the untun interface number used keep increasing, e.g.:

utun0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1380
       inet6 fe80::8c84:e08c:a73a:90c2%utun0 prefixlen 64 scopeid 0xf
       nd6 options=201<PERFORMNUD,DAD>
utun1: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 2000
       inet6 fe80::5df8:7b59:f27a:95c7%utun1 prefixlen 64 scopeid 0x10
       nd6 options=201<PERFORMNUD,DAD>
utun2: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1000
       inet6 fe80::ce81:b1c:bd2c:69e%utun2 prefixlen 64 scopeid 0x11
       nd6 options=201<PERFORMNUD,DAD>
utun3: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1380
       inet6 fe80::c3b8:fade:6a8b:afc6%utun3 prefixlen 64 scopeid 0x12
       nd6 options=201<PERFORMNUD,DAD>
utun4: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1380
       inet6 fe80::fd89:fa02:dc36:5aed%utun4 prefixlen 64 scopeid 0x13
       nd6 options=201<PERFORMNUD,DAD>
utun5: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1380
       inet6 fe80::b776:ad68:b0b6:8891%utun5 prefixlen 64 scopeid 0x14
       nd6 options=201<PERFORMNUD,DAD>
utun6: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1380
       inet6 fe80::a9f6:9b57:8916:8ed6%utun6 prefixlen 64 scopeid 0x15
       nd6 options=201<PERFORMNUD,DAD>
utun7: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1500
       inet 10.31.2.137 --> 10.31.2.137 netmask 0xffffff00

any idea what would cause that?

Thanks.

[Tunnelblick developer]

My understanding is that it isn't that a single interface number is increasing. It is that a number of different utun interfaces are being created. macOS creates one for each of the several services it runs in the background, so having seven or eight does not seem unreasonable.

Because macOS creates at least some of these interfaces when the system is booted, and others apparently later, when OpenVPN gets a new utun interface, it will not necessarily have the same number as it had previously.

[Orion Poplawski]

Still seems pretty odd to me. I have started to see utun0-2 pretty regularly
on macOS machines (with OpenVPN using utun3) - but I think utun4-7 are new to
me. I seem to be unable to delete them as well. I wonder what they might be
used for.

Thanks for the reply,

Orion

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--
Orion Poplawski
IT Systems Manager 720-772-5637
NWRA, Boulder/CoRA Office FAX: 303-415-9702
3380 Mitchell Lane or...@nwra.com
Boulder, CO 80301 https://www.nwra.com/

[Tunnelblick developer]

macOS itself is apparently using utun to implement features like "Find My". So a bunch of utunX are already used.

Years ago, only Tunnelblick and other non-OS software used utun devices, but macOS also uses them now; that's what you're seeing. And you probably can't delete them because they are in use by macOS.