ssh -Y forwarding seems to be damaged of late

[Ross Alexander]

Folks,

I have notice over the last month or two that I don't seem to
be able to get the VirtualBox UI to come up on an X11 forwarding
ssh connection.  I'm seeing the same problem with libreoffice.

What's particularly interesting is that 'ssh -Y old.grotty.server',
where old is defined as:

     FreeBSD 10.1-STABLE (GENERIC) #0 r283154: Wed May 20 11:49:55 MDT 2015
     virtualbox-ose-4.3.22_2
     virtualbox-ose-kmod-4.3.22

(and everything else there is of comparable antiquity) and then running
the VirtualBox UI works fine.  But running same out to new.shiny.box,

     FreeBSD 10.3-STABLE (GENERIC) #0 r314889: Tue Mar  7 17:55:43 MST 2017
     virtualbox-ose-5.1.14_2
     virtualbox-ose-kmod-5.1.14

(and, in a similar fashion, every port on that machine was built Monday,
via a local poudriere server) yields this:

     griffon:/u0/rwa > KDE_FORK_SLAVES=1 VirtualBox
     debug1: client_input_channel_open: ctype x11 rchan 4 win 65536 max 16384
     debug1: client_request_x11: request from 127.0.0.1 38136
     debug1: channel 1: new [x11]
     debug1: confirm x11
     ^Tload: 0.20  cmd: VirtualBox 2798 [uwait] 13.09r 0.13u 0.01s 0% 49896k
     ^Tload: 0.15  cmd: VirtualBox 2798 [uwait] 26.87r 0.13u 0.01s 0% 49896k
     ^Cdebug1: channel 1: FORCE input drain
     debug1: channel 1: free: x11, nchannels 2

and it will sit there in uwait sucking down cycles for as long as you care
to wait.  And, if you walk down the hall and log in via the local console,
all is well.

Any clues, or further debug info I can supply?  All boxes amd64, 10.3-STABLE.

regards,
Ross
--
Ross Alexander, (780) 675-6823 desk / (780) 689-0749 cell, rwa at athabascau.ca

    The fear of infinity is a form of myopia that destroys the possibility
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    all around us and even inhabits our minds. -- Georg Cantor
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