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Re: Strange ssh hangups, netbsd-9 GENERIC
On 3/12/21 8:38 AM, RVP wrote:
On Fri, 12 Mar 2021, Louis Guillaume wrote:
OpenSSH_8.0 NetBSD_Secure_Shell-20190418-hpn13v14-lpk, OpenSSL 1.1.1g
21 Apr 2020
Is this the server or the client? Can you post both?
ssh -vvv user%ser.ver@localhost 'dd if=/dev/zero bs=1m count=1 2>/dev/null'
Actually out.bin is 0b after running that - but it doesn't surprise
me. Would it actually send text to stdout for each \0 returned by dd?
Seems like it would basically be an empty string. The stderr is below.
Thanks for looking!
You should get a 1MB file if /dev/zero exists, and is readable on
the server (and the dd on the server understands `bs=1m'):
$ ssh -vvv u%s.loc@localhost 'dd if=/dev/zero bs=1048576 count=1 2>/dev/null'
$ ls -l
-rw------- 1 rvp wheel 1048576 Mar 12 13:15 out.bin
-rw------- 1 rvp wheel 11282 Mar 12 13:15 ssh.log.txt
$ hexdump -C out.bin
00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Yes - it's not writing any data through the socket after some
non-specific number of bytes. So the output of this is just empty.
OpenSSH_8.1p1, LibreSSL 2.7.3
What OS & client is this? Can you try a different client?
Connecting from NetBSD or macOS hosts gives the results I've been
describing. But a connection from Linux is never accepted. We get this
in the authlog:
ssh_dispatch_run_fatal: Connection from 192.168.1.127 port 35632:
Network is unreachable [preauth]
debug1: Exit status -1
The client is not exiting cleanly. It should--even if there
is a command execution error on the server.
It's definitely something on the server. When this hangup happens I see
this in the authlog...
sshd: fatal: process_output: ssh_packet_write_poll: Network is
... but the system is consistently up and transferring data with no
downtime (it is in fact a firewall). The problem seems isolated to sshd,
and only when a rush of data happens.
Here's the interface in case that helps.
wm1: flags=0x8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
media: Ethernet autoselect (1000baseT full-duplex)
inet 192.168.1.2/24 broadcast 192.168.1.255 flags 0x0
inet6 fe80::e8ff:fe16:4115%wm1/64 flags 0x0 scopeid 0x2
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