Re: Getting "write: address family not supported by protocol family" when using Restic over Tailscale

[Matti Andreas Kähäri <andreas.kahari%abc.se@localhost>]

On Thu, Oct 29, 2026 at 07:09:28AM -0400, Greg Troxel wrote:
> Matti Andreas Kähäri <andreas.kahari%abc.se@localhost> writes:
> 
> > For what it's worth, I've tested this patch on a 11.0_STABLE amd64
> > system, and it appears to fix the issue that I first reported.
> 
> Thanks very much for testing.  I have committed the change to -current
> and will request pullups.
> 
> > Throughput over Tailscale on NetBSD is dreadfully slow, though, but I
> > can live with that, as it's outweighed by the benefits of being able to
> > use the VPN at all.
> 
> Do you think this is a NetBSD issue?  Are you seeing the same
> configuration with other operating systems be faster?
> 
> I have been using wg, but not tailscale, and it seems fine, but that's
> in-kernel wg(4) vs user space tun(4).

I have two "sibling" VM's on the same host ("henry", Alpine Linux), one
is "eeyore" (OpenBSD) and another is "mzulft" (NetBSD). "Sibling" means
I can test over the same network distance as they are next to each
other.

On NetBSD:

mzulft% iperf3 -c henry -t 5
Connecting to host henry, port 5201
[  7] local 100.119.75.59 port 65380 connected to 100.108.126.65 port
5201
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[  7]   0.00-1.01   sec  12.8 MBytes   105 Mbits/sec    0   3.89 MBytes       
[  7]   1.01-2.02   sec  11.4 MBytes  95.0 Mbits/sec    0   7.25 MBytes       
[  7]   2.02-3.02   sec  11.5 MBytes  96.0 Mbits/sec    0   10.7 MBytes       
[  7]   3.02-4.02   sec  13.1 MBytes   111 Mbits/sec    0   14.2 MBytes       
[  7]   4.02-5.02   sec  12.0 MBytes   100 Mbits/sec    0   16.0 MBytes       
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  7]   0.00-5.02   sec  60.8 MBytes   101 Mbits/sec    0
sender
[  7]   0.00-5.03   sec  60.8 MBytes   101 Mbits/sec
receiver

iperf Done.

On OpenBSD:

eeyore% iperf3 -c henry -t 5
Connecting to host henry, port 5201
[  4] local 100.83.76.79 port 16294 connected to 100.108.126.65 port
5201
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[  4]   0.00-1.01   sec  66.5 MBytes   553 Mbits/sec    0    180 KBytes
[  4]   1.01-2.02   sec  77.0 MBytes   639 Mbits/sec    0    261 KBytes
[  4]   2.02-3.02   sec  70.2 MBytes   589 Mbits/sec    0   37.5 KBytes
[  4]   3.02-4.02   sec  62.5 MBytes   524 Mbits/sec    0    190 KBytes
[  4]   4.02-5.02   sec  72.9 MBytes   611 Mbits/sec    0    261 KBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  4]   0.00-5.02   sec   349 MBytes   583 Mbits/sec    0
sender
[  4]   0.00-5.02   sec   349 MBytes   583 Mbits/sec
receiver

iperf Done.

To be honest, the networking with VMs is far beyond me, and I'm sure
there are hundreds of things to tweak, but with a default setup, NetBSD
is more than 400 Mbit/s slower than OpenBSD here.

I also have a bare metal install of NetBSD on the host "bthalft":

bthalft% iperf3 -c henry -t 5
Connecting to host henry, port 5201
[  7] local 100.125.62.124 port 65405 connected to 100.108.126.65 port
5201
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[  7]   0.00-1.00   sec  30.1 MBytes   253 Mbits/sec    0   10.8 KBytes       
[  7]   1.00-2.01   sec  29.9 MBytes   248 Mbits/sec    0   48.0 KBytes       
[  7]   2.01-3.01   sec  31.1 MBytes   261 Mbits/sec    0   81.5 KBytes       
[  7]   3.01-4.01   sec  28.6 MBytes   240 Mbits/sec    0   43.2 KBytes       
[  7]   4.01-5.01   sec  28.2 MBytes   237 Mbits/sec    0   86.3 KBytes       
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  7]   0.00-5.01   sec   148 MBytes   248 Mbits/sec    0
sender
[  7]   0.00-5.01   sec   148 MBytes   247 Mbits/sec
receiver

iperf Done.

I can compare this with its "sibling" macOS system ("laban", a Mac Mini,
sitting next to "bthalft" on my desk):

laban% iperf3-darwin -c henry -t 5
Connecting to host henry, port 5201
[  7] local 100.77.195.15 port 51009 connected to 100.108.126.65 port
5201         
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
RTT      
[  7]   0.00-1.00   sec  40.2 MBytes   337 Mbits/sec  371   40.8 KBytes
1ms      
[  7]   1.00-2.00   sec  40.5 MBytes   340 Mbits/sec  198   69.6 KBytes
1ms      
[  7]   2.00-3.00   sec  45.0 MBytes   377 Mbits/sec  152   85.1 KBytes
2ms      
[  7]   3.00-4.00   sec  45.1 MBytes   378 Mbits/sec  226   60.0 KBytes
1ms      
[  7]   4.00-5.00   sec  43.8 MBytes   368 Mbits/sec  199   67.2 KBytes
3ms      
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  7]   0.00-5.00   sec   215 MBytes   360 Mbits/sec  1146
sender      
[  7]   0.00-5.00   sec   214 MBytes   360 Mbits/sec
receiver     
iperf Done.

The difference is not that big, but NetBSD still clocks in at 100+ Mbit/s
slower than macOS.

All NetBSD systems tested has the fix to if_tun.c applied (thanks for
that!).  But, as I said, I'm not personally greatly troubled by this
slight slowness.  I'm just happy things work.

Regards,
Andreas