Strange ssh hangups, netbsd-9 GENERIC

[Louis Guillaume <louis%zabrico.com@localhost>]

I have a netbsd-9 machine that is exhibiting some weird behavior with ssh:

NetBSD <> 9.0_STABLE NetBSD 9.0_STABLE (GENERIC) #0: Sun Jul 26 11:09:19 
UTC 2020 
mkrepro%mkrepro.NetBSD.org@localhost:/usr/src/sys/arch/amd64/compile/GENERIC amd64


When a bunch of data are sent to the terminal at once the session quits 
unexpectedly. I can't run a "dmesg" or even read a man page without it 
hanging up.

I'm only seeing this on a GENERIC machine. ssh client doesn't seem to 
matter: xterm, Apple Terminal, puTTY on Windows all have the same 
behavior. It seems the only significant debug statement I see is 
"debug3: fd 1 is not O_NONBLOCK".

$ dmesg
[     1.000000] Copyright (c) 1996, 1997, 1998, 1999, 2000, 2001, 2002, 
2003, 2004, 2005,
[     1.000000]     2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 
2014, 2015, 2016, 2017,
[     1.000000]     2018, 2019, 2020 The NetBSD Foundation, Inc.  All 
rights reserved.
[     1.000000] Copyright (c) 1982, 1986, 1989, 1991, 1993
[     1.000000]     The Regents of the University of California.  All 
rights reserved.

[     1.000000] NetBSD 9.0_STABLE (GENERIC) #0: Sun Jul 26 11:09:19 UTC 2020
[     1.000000] 
mkrepro%mkrepro.NetBSD.org@localhost:/usr/src/sys/arch/amd64/compile/GENERIC
[     1.000000] total memory = 8013 MB
[     1.000000] avail memory = 7754 MB
[     1.000000] cpu_rng: RDSEED
[     1.000000] rnd: seeded with 256 bits
[     1.000000] timecounter: Timecounters tick every 10.000 msec
[     1.000000] Kernelized RAIDframe activated
[     1.000000] running cgd selftest aes-xts-256 aes-xts-512 done
[     1.000000] RTC BIOS diagnostic error 0xf<fixed_disk,invalid_time>
[     1.000000] timecounter: Timecounter "i8254" frequency 1193182 Hz 
quality 100
[     1.000003] efi: systbl at pa 79ff8018
[     1.000003] Supermicro Super Server (0123456789)
[     1.000003] mainbus0 (root)
[     1.000003] ACPI: RSDP 0x0000000079B29000 000024 (v02 SUPERM)
[     1.000003] ACPI: XSDT 0x0000000079B290B0 0000D4 (v01 SUPERM 
SMCI--MB 01072009 AMI  00010013)
debug3: send packet: type 1
debug1: channel 0: free: client-session, nchannels 1
debug3: channel 0: status: The following connections are open:
  #0 client-session (t4 r0 i0/0 o0/0 e[write]/0 fd 6/7/8 sock -1 cc -1)

debug3: fd 1 is not O_NONBLOCK
Connection to <> closed by remote host.
Connection to <> closed.
Transferred: sent 2868, received 5772 bytes, in 5.0 seconds
Bytes per second: sent 568.8, received 1144.8
debug1: Exit status -1



Here's also the network configurations (up to the hangup). All 
interfaces are 1000baseT:


wm0: flags=0x8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        capabilities=7ff80<TSO4,IP4CSUM_Rx,IP4CSUM_Tx,TCP4CSUM_Rx>
        capabilities=7ff80<TCP4CSUM_Tx,UDP4CSUM_Rx,UDP4CSUM_Tx,TCP6CSUM_Rx>
        capabilities=7ff80<TCP6CSUM_Tx,UDP6CSUM_Rx,UDP6CSUM_Tx,TSO6>
        enabled=0
        ec_capabilities=17<VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,EEE>
        ec_enabled=2<VLAN_HWTAGGING>
        address: 02:00:e8:16:41:15
        media: Ethernet autoselect (1000baseT 
full-duplex,flowcontrol,rxpause)
        status: active
        inet 173.48.81.60/24 broadcast 173.48.81.255 flags 0x0
        inet6 fe80::3093:984:6d25:b09f%wm0/64 flags 0x0 scopeid 0x1
wm1: flags=0x8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        capabilities=7ff80<TSO4,IP4CSUM_Rx,IP4CSUM_Tx,TCP4CSUM_Rx>
        capabilities=7ff80<TCP4CSUM_Tx,UDP4CSUM_Rx,UDP4CSUM_Tx,TCP6CSUM_Rx>
        capabilities=7ff80<TCP6CSUM_Tx,UDP6CSUM_Rx,UDP6CSUM_Tx,TSO6>
        enabled=0
        ec_capabilities=17<VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,EEE>
        ec_enabled=2<VLAN_HWTAGGING>
        address: 02:00:e8:16:41:15
        media: Ethernet autoselect (1000baseT full-duplex)
        status: active
        inet 192.168.1.2/24 broadcast 192.168.1.255 flags 0x0
        inet6 fe80::e8ff:fe16:4115%wm1/64 flags 0x0 scopeid 0x2
wm2: flags=0x8802<BROADCAST,SIMPLEX,MULTICAST> mtu 1500
        capabilities=7ff80<TSO4,IP4CSUM_Rx,IP4CSUM_Tx,TCP4CSUM_Rx>
debug3: send packet: type 1
debug1: channel 0: free: client-session, nchannels 1
debug3: channel 0: status: The following connections are open:
  #0 client-session (t4 r0 i0/0 o0/0 e[write]/0 fd 6/7/8 sock -1 cc -1)

debug3: fd 1 is not O_NONBLOCK
Connection to <> closed by remote host.
Connection to <> closed.
Transferred: sent 2988, received 5480 bytes, in 3.4 seconds
Bytes per second: sent 880.7, received 1615.1
debug1: Exit status -1
dhcp-203 $



Any help would be great. Let me know if I can provide more details. Thanks!

--
Louis