No worries; I imagine most people don't run sshd on cygwin. It looks to
me like the issue involves i/o between sshd and its sub-processes on cygwin.
Is anyone else able to successfully scp large files (>64KB) to cygwin as
the remote receiving end (with the latest cygwin)?
On 2023-06-23 16:27, Voris, Ben wrote:
I did not and cannot. Sorry.
Fwiw, pushing from Cygwin to the remote also worked.
-----Original Message-----
From: Chris Roehrig <croeh...@house.org>
Sent: 23 June 2023 17:23
To: Voris, Ben <ben.vo...@hpe.com>
Subject: Re: scp and ssh 'cat' stalls at 64k bytes
Did you execute the scp on the remote (e.g. Linux) host? It only
fails when cygwin is the remote and target end (i.e. "pushing" to a
cygwin host); "pulling" works fine.
On 2023-06-23 16:07, Voris, Ben wrote:
Using scp from OpenSSH_9.3p1, 30 May 2023, copied a 8317351936 byte file from
a remote to Cygwin. sha1sum says it arrived correctly.
Windows Firewall is running.
-----Original Message-----
From: Chris Roehrig <croeh...@house.org>
Sent: 23 June 2023 13:42
To: cygwin@cygwin.com
Subject: Re: scp and ssh 'cat' stalls at 64k bytes
On 2023-06-23 08:28, Brian Inglis wrote:
On 2023-06-23 00:26, Chris Roehrig via Cygwin wrote:
I've upgraded cygwin recently (from a much older version) and am
encountering a new problem on all my Win10/WIn11 machines.
With openssh and pv installed on cygwin (3.4.7-1):
dd if=/dev/zero bs=1 count=65536 | ssh localhost 'cat > /dev/null'
# works
dd if=/dev/zero bs=1 count=65537 | ssh localhost 'cat > /dev/null'
# stalls (and anything larger)
dd if=/dev/zero bs=1 count=65537 | ssh localhost 'pv > /dev/null'
# replace 'cat' with 'pv' and it works
This happens with or without Windows Firewall enabled, with any input
64k, and also remotely from Linux.
It also seems to affect scp to cygwin which stalls if the file is >= 64k
In case equivalent Windows services are running, I check for, shut
down, and disable the following Windows services I have seen, or seen
warnings about, before trying to start Cygwin services:
ssh ssh-agent sshbroker sshproxy sshd sshdbroker sshdproxy
Do you take similar precautions on the Windows systems with issues?
The only service listed is ssh-agent which is disabled and stopped.
TaskManager did show many zombie/stuck cat.exe and scp.exe which I
terminated, but that did not help. Nor did rebooting.
I use ssh, rsync, slogin frequently on these machines to/from windows
and linux and rsync (over ssh) gigabytes of stuff daily to/from Linux
and other windows machines with no issues. It is only this case of
reading more than 64K from stdin over ssh (and scp) that is hanging.
Please show at least the output of `uname -srvmo`,
CYGWIN_NT-10.0-19045 3.4.7-1.x86_64 2023-06-16 14:04 UTC x86_64 Cygwin
and if possible provide a text attachment of the output log from
running `cygcheck -hrsv > cygcheck.out`, as suggested under the
Problem reports link below.
I've attached the file.
I take it then you can't replicate this? Can you confirm whether this
command works successfully (i.e. exits without hanging):
dd if=/dev/zero bs=1 count=65537 | ssh localhost 'cat > /dev/null'
Are you able to 'scp' large files to cygwin?
It also hangs if I replace 'cat' with 'sed {}' or 'awk {print}', but not
with 'pv'. Those all passthrough stdin>stdout and should behave the
same as cat. (pv is basically cat with a progress bar which is omitted
if there's no controlling terminal like in this case).
The curious fact that 'pv' works makes me think it is a Cygwin library
problem and not anything related to firewall/network/Windows.
I've verified that cat, pv, and sshd all have the same ACLs. e.g.
aquila[77]% icacls pv.exe
pv.exe AQUILA\croehrig:(F)
BUILTIN\Administrators:(RX)
Everyone:(RX)
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